Handbook Liquid Mono Propellant Thruster Performance Measurement

AFRPL-TR-79-24

_.'". i

JPL

79-32

"" ADA072125

It1111_111111111111111111 f

Handbook of Recommen"deO .......... Practices for the Determination of Liquid Monopropellant Rocket Engine Performance

• _--.__J

c

JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY PASADENA

s

CALIFORNIA

AUTHORS:

R, R, R.

JUNE

1979

Ao S. K.

91103

BJORKLUND ROGERO BAERWALD

Approved

_or

_i_trib_tion

Pablic

Re£e=_e;

_nlimited

_F

PREPARED AIR

L"

FORCE

DIRECTOR AIR

OF

FORCE

EDWARDS

ROCKET

SCIENCE

SYSTEMS

AFB,

PROPULSION

FOR:

LABORATORY

& TECHNOLOGY

WASHINGTON,

COMMAND

CALIFORNIA

NATIONAL AERONAUTICS SPACE ADMINISTRATION

93523

Ill_ODtR[OBY

NATIONAL TECHNICAL INFORMATION SERVICE U.S.

O[FARIM|III SFIIIIIGFIELD,

O| ¢OIIN£RC[ VA. 22161

D.C.

&

J

NOTICES

I

When U.S. Government drawings, specifications, or other data are used for any purpose other than a definitely related government procurement operation, the Government thereby incurs no responsibility nor any obligation whatsoever, and the fact that the Government may have formulated, furmished, or in any way supplied the said drawings, specifications or other data, is not to be regarded by implication or otherwise, or in any manner licensing the holder or any other person or corporation; or conveying any rights or permission to manufacture, use, or sell any patented invention that may in any way be related thereto.

FOREWORD

The work was prepared by the Control and Energy Conversion Division, Jet Propulsion Laboratory, California Institute of Technology, and was Jointly sponsored by the Air Force Rocket Propulsion Laboratory, Edwards AFB, California, through a MIPR FO-4611-76-X-O053 with NASA and by the National Aeronautics and Space Administration under Contract NAS7-100. This report has been reviewed by the information office/XOJ and is releaseable to the National Technical Information Service (NTIS). At NTIS it will be available to the general public, including foreign nations. This technical report has been reviewed and is approved for publication; it is unclassified and suitable for general public release.

WALTER Chief,

FOR

THE

EDWARD Liquid

A. DETJEN Satellite

Propulsion

Branch

COMMANDER

E. STEIN, Deputy Rocket Division

Chief,

GENERAL

DISCLAIMER

8

This document may have problems that one or more of the following disclaimer statements refer to: t

This document has been reproduced from the best copy furnished sponsoring agency. It is being released in the interest of making available as much information as possible.

by the

This document may contain data which exceeds the sheet parameters. It was furnished in this condition by the sponsoring agency and is the best copy available. •

•

This document

may contain

pictures

have been reproduced

which

The document

is paginated

tone-on-tone

or color graphs,

in black

as submitted

charts and/or

and white.

by the original

source.

Portions of this document are not fully legible due to the historical nature of some of the material. However, it is the best reproduction available from the original submission.

UNCLASSIFIED SECURIT_'-_CL--A'SSIFICATION

OF

THIS

PAGE

(When

Dill

Entered)

,,! AFRPL_'TR-

READINSTRUCTIONS BEFORE COMPLETING

PAGE

,._.' / ,/REPORT DOCUMENTATION -,.. REPOR'i_%MBE-R--: I"

2.

GDVT

ACCESSION

NO.

RECIPIENT'SCATALOG

5.

TYPE

FORM

NUMBER

79- 24 i

....T_-_-L 79-'c_ _.....

\

4. T,ITLE (and Subtitle) .

3,

/-

!;HANDBOOK

OF

RECOMMENDED

_DETERMINATIONOF

PRACTICES

LflQUID

FOR

MONOPROPELLANT

PERFO_NCE,

-

.

1

:

PERFORM , ..............

_ "'.

it

AUTHOR(_

....

'_RT_: ,

f .Bj;rklund,

S._ogero,

R,

Jet

ORGANIZATION

Propulsion

Calif. 4800

/

K./Baerwald

AND ADDRESS

of

OR

- NAS7-100,

Task

10.

Grove

Dr.,

PROGRAM

Force

Rocket

14.

AFB

MONITORING

.r-

12,

,_

•

-i

,

,,

.,

./,-,

!

i.;_. _

? "16.

= I_1S T RI

NAME

BU

,

TI

/

Laboratory/LK

;

\

13."

1979

NUMBER

oF'

J

PAGES

I

265 &

AODRESSOI

.

,

dllfetent

from

Controllln

80lttcs)

15.

SECURITY

,

...... .' •

,

CLASS•

(of

this

report)

Unclassified

, ] /

/

!15a.

DECLASSIFICATION/DOWNGRADING SCHEDULE

,

t

O N_ST'A'T:EI_I_e_N'T

APPROVED

/

REPORT.DAT.E..-

93523

AGENCY

TASK ....

91103

AND ADDRESS Propulsion

CA

No. 240

PROJECT, NUMBERS

•

1 June Edwards

No.

UNIT

/ Alr

Order

ELEMENT, &._WORK

." i

CA

Contract

Amendment

AREA

Pasadena

NUMBER

GRA't_'T'NUM'B'ER(s)

Prime

Technology

I1.--CONTROLLINGOFFICENAME

REPORT

JPL/NASA

Laboratory

Institute Oak

NAME

COVERED

79

RD-65 S: PERFORMING

PERIOD

/,

CON'TRACT

8.

"

R.

&

NG.ORG

:JPL 7.

REPORT

,ROCKET '-6>

li ENGINE

OF

THE

FOR

(of

PUBLIC

thts

Report)

RELEASE:

DISTRIBUTION

UNLIMITED--

\

I7.

DISTRIBUTION

STATEMENT

_'o!

the

abstract

entered

In

Block

20,

It

different

Irom

Report)-'_

•

_,_-

.,

,_"i'_.......

, I.

..:c-._.. -

P~

" "'-,,.... , -_-

: .... lB.

SUPPLEMENTARY

, "

.

..:--:.

..

2,.'*

:":,

..

,.,

.

NOTES .

"-6..

b

'__---_-.'._".'.., .... 19.

KEY

WORDS

(Continua

Performance and

on

reverse

wide

_l necessary

standardization,

steady

state,

Test

and

Identify

by

block'number)

Monopropellant

fixtures,

.... :.

." ,-,

rocket

engines;

:_

."

--Pbl_e

"T:esting "

Instrumentatio_

-.:.

" ,--',:

,'"'"'..-.;

:,.._

,

, t

...-: • L

20.

ABSTRACT

(Continua

on

reverse

side

II

necessary

_d

Identt_

by

block

numbe_

' '

• ,

,,:.

,

" '

.'I

..._ This

handbook

neer

in

direct the

the

is

intended

design,

measurement

determination

of of

defining

relations

are

given.,(OVER)

also

to

serve

installation, those

as and

reducing

which thruster

the

for

operation

quantities

monopropellant

for

a guide

measurements

the

of are

of

experienced.test

systems

to

fundamental

performance. to

be

engi-

used

for

importance

The

performance

the to

procedures,

and

parameters t I I

FORM

DD ,_AN_, 1473

EDITION

OF

1 NOV

6S

IS

OBSOLETE

UNCLASS •

/

SECURITY

CL'ASSIFICATION

IFIED OF

THIS

! PAGE

(When

Data

Entarad)_.J,

. •

,-:_=

F

[

UNCLASSIFIED SECURITY

CLASSIFICA'T'ION

This

handbook

impulse

is

THiS

data

PAGE(When

composed

measurement,

measurement, and

OF

of

glossaries

are

six

propellant

temperature reduction

Detm

and

Eneered_

discrete mass

measurement, performance

included

with

each

-

f._>

. .. -

_ •.

I-'

i-

•

-._-

_"

exhaust section

r

'f.-

and

as

flow gas

determination.

_ -....,.-; .

sections

usage

pertaining measurement, composition References,

necessary.

to

force

and

pressure measuremdnt, appendixes,

and

PREFACE

I

This Handbook of Recommended Practices for the Determination of Liquid Monopropellant Rocket Engine P_rfbrmance has the objective of promoting a uniformity of methodology throughout the monopropellant community as regards to pulse mode and steady state thruster testing and data reduction. The program was conceived within a Joint Army-NavyNASA-Air Force (JANNAF) monopropellant working group, consisting also of representatives from industry and academia, to fill what was felt to be a universal need for such standardization of practices among the

manufacturers

and

users

of monopropellant

rocket

engines.

The JANNAF Rocket Engine Performance Working Group has devoted considerable effort toward the development of a consistent methodology for determining rocket engine performance. However, the publications of the JANNAF Rocket Engine Performance Working Group are directed primarily toward bipropellant engines operating at steady state conditions and are, therefore, not directly applicable to the performance determination of monopropellant engines which may operate primarily in the pulse mode. However, the Handbook of Recommended Practices of Measurement of Liquid Propellant Rocket Engine Parameters, Chemical Propulsion Information Agency (CPIA) Publication No. 179, and Rocket Engine Performance Test Data Acquisition and Interpretation Manual, CPIA Publication No. 245, both published by the JANNAF Rocket Engine Performance Working Group, have served as excellent guides for the development of the current document. This handbook is intended to serve the experienced test engineer in the design, installation, and operation of systems which include the determination, by direct measurement, of rocket engine thrust and impulse, propellant mass flow, pressure, temperature, and exhaust gas composition. The algorithms and defining relations for reducing these measurements to performance parameters are also given. This document is not intended to serve as a primer for the inexperienced engineer, as the depth required for such a publ_cation is clearly beyond the scope of this or any other single document.. Specific design guideline_ are, however, offered for the critical components of each system.

These

This handbook is divided into six sections are presented in the following •

Force

and

•

Propellant Pressure

Impulse Mass

relatively order:

discrete

sections.

Measurement Usage

and

Flow

Measurement

Measurement

•

Temperature

Measurement

•

Exhaust

Composition

•

Data

Gas

Reduction

and

Measurement

Performance

Determination

iv

IPreceding pageblankI l

f

Each and

of the

sections

appendixes

includes

a table

of

contents,

of

data

glossary,

references,

as necessary.

To

achieve

the

uniformity

acquisition

and

interpreta-

tion which is the goal of the handbook, it is recommended that the procedures and practices outlined herein be required for all RFQ's and contracts. This recommendation implic_tly includes also adherence to CPIA Publication No. 180, _RPG Handboo_ for Estimating _he Uncertainty in Measurements Made With Licuid Pro_ellant Rocket Engine SYstems. Deviations from these procedures should be specifically negotiated. This

handbook

has

been

formatted

for

reprint

as

a CPIA

publi-

cation. It is probable that its use by the monopropellant community will result in recommendations for additions or revisions. These comments are welcomed and may be addressed to the authors at JPL, the program sponsors at

AFRPL

and

NASA/OAST, Chemical Johns

Qr_

in the

Propulsion

Hopkins

case

of

Information

University

Applied Physics Laboratory 8621 Georgia Avenue Silver Springs, Maryland

V

20910

the

CPIA

Agency

version,

to:

ACKNOWLEDGMENTS I This handbook was produced under the joint sponsorship of the U.S. Air Force Rocket Propulsion Laboratory (AFRPL) and the National Aeronautics and Space Administration, Office o£ Aeronautics and Space Technology (NASA/CAST). Program managers at AFRPL included Mr. Paul Erickson, Lt. Vince Broderick, and Capt. Dennis Gorman. Mr. Frank Stephenson was the program manager at NASA/CAST. The

development

of

this

handbook

involved

the

efforts

of

almost the entire monopropellant community. A considerable expenditure of time and energy was contributed by those organizations which supplied materials or comments in response to the comprehensive survey questionnaire which was distributed throughout the monopropellant and bipropellant community. The following individuals and organizations deserve much credit for their efforts in this regard (listed alphabetically): Mr. Dan Balzer RCA/Astro Electronics P.O. Box 80 Princeton,

New

York

Division 08540

Mr. Fred Etheridge Rockwell International Space Division 12214 Lakewood Blvd. Downey,

California

Mr.

Freeman

Jim

_-_ 90241

":'

Air Force Rocket Propulsion Edwards Air Force Base Edwards,

6alifornia

Laboratory

935.23

Mr. J. L. Gallagher Vought Corporation System Division P.O. Box 5907 Dallas, Texas 75222 Mr. George Huson COMSAT Laboratories Clarksburg,

Maryland

Mr.

Miller

Richard

2O734

Boeing Aerospace Company P.O. Box 3999 Seattle, Washington 98124 Mr. R. R. Nunamaker NASA/Ames Research Moffett

Field,

'%

Center

California

vl

94035

S

L/ Mr. R. David Steel Martin Marietta Corporation P.O. Box 179 Denver, Colorado 80201 Mr. NormStern Aeroneutronic Ford Corporation OneFord Road Newport Beach, California 92663 Mr. ThomasE. Williams NASA/Goddard SpaceFlight Center Greenbelt, Maryland 20771 By far the most comprehensiveresponses were supplied by the rocket engine manufacturers themselves. This seemsto be due not only to the fact that t_e manufacturers have the most sophisticated and complete rocket engine test facilities, but also to a genuine interest on the part of the manufacturers in the production of this handbook. Excellent responses were received from the following (alphabetically): Mr. T. E. Hudson The Marquardt Company 16555Saticoy Street 91409 Van Nuys, California Mr. Milt Marcus Hamilton Standard Bradley Field Road Windsor Locks, Connecticut

06096

Mr. V. A. Moseley Bell Aerospace Company P.O. Box One Buffalo, NewYork 14240 Mr. Robert Sackheim TRWSystemsGroup OneSpace Park RedondoBeach, California

92078

Mr. Bruce Schmitz Rocket Research Corporation York Center Redmond,Washington 98052 Mr. Walter Schubert Pratt & Whitney Aircraft Florida Researchand DevelopmentCenter P.O. Box 2691 West Palm Beach, Florida 33902 In addition to the written responses, muchadditional information was obtained from visits to select organizations. This provided vii

the authors with the opportunity to see firsthand the test facilities involved and to have explained the rationale behind the various measurement philosophies and data reduction procedures. The following organizations were gracious enoughto give of their time in this manner (alphabetically): Air Force Rocket Propulsion Laboratory Edwards, California Bell Aerospace Buffalo, NewYork GoddardSpace Flight Center Greenbelt, Maryland Hamilton Standard Windsor Locks, Connecticut HughesAircraft Company E1 Segundo, California The Marquardt Company Van Nuys, California Rocket Research Corporation Redmond,Washington Rockwell International Space Division Seal Beach, California TRWSystems, Inc. RedondoBeach, California Vought Corporation SystemsDivision Dallas, Texas The authors would like to take this opportunity to express their appreciation for the cordial way in which they were received and for the hospitality extended to them by the above organizations. Following acquisition of the information which was gathered in the manner described above, a draft Of the six handbooksections was produced and distributed to over 32 membersof the monopropellant community. Several months were allowed for a review and critique of the proposed recommended practices. In addition to those membersand organizations of the monopropellant thruster community, gratitude is expressed to the following individuals for taking the time to review and commentin detail upon various sections of the draft document: Mr. Phil Bliss, Intersociety DireCtor, Instrument Society of America; Mr. Pierre F. Fuselier (retired), viii

Lawrence

Livermore

Mr.

Frederick

Mr.

Phillip

Laboratory;

Williams, Scott,

the

Mr.

Eastern

Jon

Inskeep,

Standards

Jet

Propulsion

Laboratory,

Dept.

Laboratory; of

Foxboro

Company;

and

Mr.

Donald

Bond,

pointed

out

not

all

commentsreceived

the

Jet

Navy;

Propulsion

Laboratory. It the the of

various

and

be

were

acknowledgments the

handbook

suggested of

must

reviewers

the

by task

fiscal

strongly

given by

the and

any

would

complications. and,

in

other

here

do

individual

reviewers have

that

incorporated not or

would

cases,

offered. It is felt, however, have worked to the detriment

imply

of

in

ix

final

an

Some increase

disagreed

endorsement the

changes

in

the

scope

one with

none of the required usefulness or accuracy

and

of

publication

contradicted

from

document

unqualified

unacceptable

authors

that the

the

caused

reviewers the

the

organization.

have

resulted Some

into

delays

another

the

rather

comments

compromises of the document.

CONTENTS

SECTION

I

FORCE

SECTION

II

PROPELLANT

SECTION

III

PRESSURE

SECTION

IV

TEMPERATURE

MEASUREMENT

SECTION

V

EXHAUST

COMPOSITION

SECTIONVI

DATA

AND

IMPULSE

MASS

MEASUREMENT

USAGE

AND

FLOW

I-I

MEASUREMENT

MEASUREMENT

GAS

REDUCTION

AND

2-I

3-I

4-I

MEASUREMENT

PERFORMANCE

DETERMINATION

5-I

6-I

SECTION

FORCE

AND

IMPULSE

e

//-/

I

MEASUREMENT

"

FORCE

AND

SECTION

I

IMPULSE

MEASUREMENT

I

CONTENTS

1.0

INTRODUCTION

I-I

2.0

SCOPE

I-I

2.1

OBJECTIVE

2.2

LIMITATIONS

I-2

3.0

DESIGN

I-2

3.1

MECHANICAL

3.1.1

Thrust

3.1.2

Measurement

Force

3.1.3

Calibration

Equipment

3.2

ELECTRICAL

3.2.1

Signal

3.2.2

Electrical

3.2.3

Recording

3.2.4

Visual

3.2.5

Data

4.0

INSTALLATION

4.1

COMPONENT

4.1.1

Force

4.1.2

Calibrator

4.1.3

Thrust

4.1.4

Dynamic

--

I-I

CONSIDERATIONS COMPONENTS

I-2 I-4

Stand

AND

Transducer

1-12

ELECTRONIC

Conditioning

COMPONENTS

Equipment

Calibration

Equipment

Equipment

AND

CHECKOUT

PROCEDURES

Force r

1-19 1-19

Transducer

Stand

1-18

1-19

CERTIFICATION

Dead

1-15

1-18

Equipment

Processing

1-15

1-18

Equipment

Display

I-6

1-19 Weights

Flexures

1-25 and

Calibrator

Restraints

1-25 I_25

SYSTEM

CERTIFICATION

1-26

ENGINE

INSTALLATION

1-26

5.0

CALIBRATION

5.1

STATIC

5.1.1

Deadweight

5.1.2

Working

Standard

5.1.3

General

Calibration

5.1.4

General

Verification

5.2

DYNAMIC

CALIBRATION

6.0

OPERATING

6.1

PRETEST

6.2

POSTTEST

7.0

DATA

7.1

CALIBRATION

7.2

RUN

8.0

GLOSSARY

1-34

9.0

REFERENCES

1-38

AND

VERIFICATION

PROCEDURES

1-26

CALIBRATION

1-26

Calibrator

Method

Force

1-27

Transducer

Calibration

Method

Procedures

1-29

VERIFICATION

1-29

PROCEDURES

1-30

PROCEDURES

1-30

1-31

PROCEDURES

ACQUISITION AND

1-27 1-28

Procedures AND

--

AND

PROCESSING

VERIFICATION

TECHNIQUES

DATA

1-31 1-31

DATA

1-33

APPENDIX_ I-A

THRUST

I-B

SHORTAND UNCERTAINTY

I-C

SHUNT

MEASUREMENT

SYSTEM

LONG-TERM

CALIBRATION

THRUST

ELEMENTAL

UNCERTAINTIES

MEASUREMENT

IA-I

SYSTEM IB-I

OF FORCE

1-ii

TRANSDUCERS

IC-I

Mechanical Components of a Vertical Axial Thrust Measurement Stand

I-2

Conventional

I-3

Thrust

I-4

Abnormal

I-B-I

Example

Measurement Loading of Control

Uncertainty I-B-2

1-C-1

6-Wire

Strain System

Test

Bridge

Calibration

Element I-3

Transducer

.....

I-9

Diagram

1-16

Installation

1-24

for

Checks

IB-3

Block Diagram of ShortUncertainty Checks Shunt

Block

Effect, Data

Gage

Single

and

Circuit

1-iii

Long-Term IB-4

Configuration

IC-2

i

FORCE

AND

SECTION

I

IMPULSE

MEASUREMENT

1.0

Recommended lation,

checkout,

system

to

Three

be

used

appendixes and

are and

during

of

tests

included:

I-B,

Uncertainty;

practices

calibration, are

Uncertainties;

INTRODUCTION

Short-

I-C,

a

and

This

section

experienced

engineer

Long-Term

measurement

system

liquid

monopropellant

the

detailed

but

rather of

juction

with

good

meets

rocket

each

portion

engine.

current,

performance

2. I

The

thrust

to

of

has the

a

the of

produced

been

to

measurement for

a

by

made

a

specify

system,

the

guidelines,

provide

for

operation

impulse

provided

These

a guide

critical used

in

available

measurement

comcon-

equipment

system

which

specified.

be

of

monopropellant

rocket

at

pressures

tests

are

altitudes

of

These

engine engine

simulated The

recommended

specifically uncertainties.

Thrust

Range

to

44

N

(0.01

to

10

ibf)

measured

30

is

ranging

km

Mode

to

4400 1000

N

69

conducted (100,000

contained

measurements

in

from

of

of

Steady

ft) in

thrust

this and

Operation

Steady

from

the

to

3450

kN/m

in

a vacuum

or

higher section

impulse

the

5 ms

state

catalytic

reaction

chamber 2

(10

to

chamber be

min.

mode, on

50

time

I-I

ms

a psia).

maintained.

are

directed

having

the

in

following

Measurement

+_0.5%

Thrust

+_5.0%

Impulse

+_0.25%

Thrust

±2.0%

Impulse

ibf) Pulse

of 500

where

can

Uncertainty

state

Pulsed mode, min. on time to

derived

hydrazine

normally

practices to

0.044

(I0

System

OBJECTIVE

decomposition

44

as and

commercially

will

criteria

serve

attempt

are

system.

practices,

engine. Elemental

Transducers.

and

portion

state-of-the-art,

engineering

the

No

any

the

to

thrust

guidelines

of

rocket System

Measurement

Force

installation, the

for

design

of

instal-

measurement

Measurement

written

measuring

design,

SCOPE

design,

configuration specific

ponents and

for

been

the

thrust

Thrust

Calibration

has

in

the

a

monopropellant

Thrust

2.0

for of

liquid

I-A,

Shunt

outlined

operation

2.2

LIMITATIONS The

recommended

practices

in this

section

are

limited

to

thrust measurements of a single monopropellant hydrazine rocket engine. There is ho fundamental reason why these practices would not be applicable to other types of monopropellant thrusters or even bipropellant rocket engines if certain environmental factors peculiar to the specified propellant(s) are accommodated. Additional limitations are listed below: (1)

Only those thrust systems that infer a force from a bonded metallic strain gage transducer are considered in this section. Specialized applications requiring higher transducer electrical output, extehded highfrequency response, miniature size and/or weight or some combination of these characteristics may necessitate other transduction techniques. For the vast majority of force measurements related to monopropellant rocket engines, however, the bonded metallic strain gage transduction element is the recommended choice.

(2)

Test Cell simulated altitude pressure should be maintained at a level which assures design exhaust nozzle flow characteristics.

(3)

Temperature

conditioning

should

be

limited

to

a practical

operating range as determined for the specified spacecraft environment designed to use monopropellant hydrazine. (4)

The

minimum

pulsed

thrust

duration

is

limited

by

the

propellant control Valve operating time. For low thrust, below 44 N (10 ibf), this could be as short as 5 ms; however, at higher thrust, above 44 N (10 Ibf), a more practical limit is about 50 ms.

3.0

DESIGN

CONSIDERATIONS

The design of a thrust measuring system requires consideration of certain key mechanical, electrical, and electronic components which must be incorporated. Mechanical components include the thrust stand, a measurement force transducer and the force calibration equipment. Electrical and electronic components include electrical calibration, signal conditioning, recording, visual display and data processing equipment.

3.1

MECHANICAL A typical

in a vertical, in Figure I-I.

_(I)

single These

COMPONENTS arrangement

of the

element, axial components are

Thrust frame is mounted.

into

I-2

major

mechanical

components

thrust measuring stand identified as follows: which

the

rocket

engine

is shown

assembly

DYNAMIC

II

FORCE CALIBRATOR (REMOVA

WORKING

BLEI

STANDARD

FORCE

TRANSDUCER

STATIC

CALIBRATOR

------]

ADJUSTABLE

L I

L..

I

L

MULTIPLE

CALIBRATION

DEAD

FORCE

STATIC

TRANSDUCER

CALIBRATOR

I

(ALTERNATE1

I I

FORCE

WEIGHT

RODS

FORCE

I

GEN£1_TOR

__

SEISMIC MASS

VIBRATION )I, ATORS ,],.,

,;,_,

..."i/

_

GROUND PLANE

LINKAGE FLEXTURES MEASUREMENT FORCE

TRANSDUCER

O,SCO NECT LINKAGE

_

FRAME-_

J

r

_

-_

.THRUST

FRAME

/_uExTUrES

ROCKET

Figure

I-I.

Mechanical Components of a Vertical Axial Thrust Measurement Stand

I-3

Single

Element

-J

(2)

Measurement force and flexures.

transducer

(3)

Seismic

vibration

mass

ground

the

same

isolators

(q)

Thrust frame restraints the seismic mass.

(5)

In-place static force calibrator dead weight type or the working with force generator type,

(6)

Dynamic force during engine

for

the

linkages

attached

to

the

and

calibrator testing.

flexures

attached

to

of either the multiple standard force transducer

which

is

normally

removed

oriented thrust measuring stand will have Additional flexural supports would normally

thrust

As shown

mechanical

plane.

A horizontally basic components.

be required

with

with

frame.

in Figure

I-I,

the measurement

force

transducer

is normally linked mechanically between the thrust frame and the seismic mass with -flexures. An alternate method for the optimum high-response pulsed thrust stand would be to eliminate the flexures and use hard mounting on both ends of a ruggedized force measurement transducer. The rocket engine thrust frame assembly is restrained by struts containing pa_rs of flexures so that movement along only the thrust axis is permitted. The geometric centerline of the axisymmetrical engine is shown to coincide with the thrust measurement axis. Forces-applied by the static calibrator should also coincide with the thrust measurement axis. The interaction of the thrust system components that takes place during engine testing should be faithfully duplicated by in-place calibration techniques.

3.1.I

the

design

Thrust

Stand

The following considerations of a thrust measuring stand:

are

of

primary

interest

in

(1)

The thrust stand should be designed to have a large seismic mass to engine-thrust frame mass ratio (ms/me). Experience has indicated that this ratio should be greater than 20:1 with values around 500:I desirable.

(2)

The

seismic

by the

(3)

mass

test

Transverse

should

chamber

be well

and

restraints

ground

used

isolated

(4)

axial

force

forces

and

be designed than 0.15%

applied.

Transverse restraints should to the main axis of thrust.

I-4

vibration

:

to counteract

moments generated by the engine should to limit their axlal restraint to less of the

from

plane.

be

installed

perpendicular

"7.

(5)

Transverse restraints should be designed at least 20% of the axial force because magnitude or during

I

(6)

may be developed engine failures.

Transverse

restraints

during

should

the

start

be attached

the thrust frame and the seismic mass changes can be made without disturbing stand alignment. (7)

Propellant that they

(8)

Propellant

and purge lines serve as elastic and

purge

perpendicular to and moments, and temperature, and ments. Flexible unless it can be procedures, that are negligible.

(g)

(10)

lines

to withstand forces of this transients

between

so that engine the thrust

should be installed pivots.

so

should

nominally

be

installed

the main thrust axis to balance forces to minimize the effect of fluid flow, pressure variations on thrust measurepropellant lines should be avoided demonstrated, through calibration the effects of system pressurization

The thrust frame structure should be designed to deflection limits rather than stress limits. A very stiff lightweight structure will have a natural frequency high enough to ensure accurate response to pulsed thrust inputs and oscillations that will not influence steady state thrust measurement. A na.tural frequency in excess of 200 Hz is attainable. Environmental changes which may affect the alignment and restraint should be thoroughly evaluated. Safety

stops

should

if a thrust frame fatigue, overload,

be used

to limit

engine

motion

member fails during a test because or other hardware failures.

of

(11)

Safety stops should be set for 4 times the rated deflection.

(12)

The measurement force transducer must be protected from inadvertent overloads during installation and removal of the test engine assembly by suitable mechanical stops.. If this is not practical the force transducer should be removed during these operations.

(13)

Lost

(14)

Clearance

motion

of the system

must

axial

exist

thrust frame deflection.

(15)

Targets

(16)

Locating stand

in the

should Jigs

load

between over

the

be installed and

to facilitate

I-5

indexes proper

a clearance

column

should

fixed

and

range

of

for should

of at

be

alignment.

be eliminated.

movable interest

alignment built

least

parts of

purposes. into

the

(17)

Thermal

load

on the

thrust

stand

should

be

minimized

through the use of radiation shields, conductive insulators, or thermal compensating elements.

Measurement

3.1.2

that

measure

Force

Transducer

These recommended practices are limited to thrust systems force with a bonded metallic strain gage force transducer,

commonly referred to as a load cell. The load-carrying structure of the force transducer is normally machined from a single piece of heattreated metal. The elastic deformation of this structure=is sensed by attached strain gage elements. These strain gages are electrically connected in a Wheatstone bridge circuit which can be balanced at no load. The application of a force to the load structure produces resistance changes in the strain gages, thus unbalancing the bridge circuit. The resultant output signal is directly proportional to the applied force and the excitation voltage. Standard design specifications for strain gage force transducers are given in ISA-$37.8, Reference I-1. The following is a summary of these basic design considerations as they apply to a thrust stand force transducer.

3.1.2.1

Mechanical

(1)

The

Design type

of

force

transducer

is

determined

by

the

direction of the applied load as tension, compression, or universal, combining both tension and compression. The universal type would normally be used in thrust stands. Where preloading is used a compression type could be employed. (2)

The physical dimensions, type of mounting, mounting dimensions, and type of force connection will vary with manufacturer, but all transducers can generally be adapted for thrust stand installation.

(3)

The load-line linkage from the thrust frame to the force transducer should be designed such that only axial loads are transmitted. When using a directly connected load line, flexural linkages are normally used on both ends of the transducer. Preloaded installations contact

(4)

A series thrust

(5)

use a hard mount on the fixed on the active end to eliminate installation measurement

of is not

force

end and point off-axis loads.

transducers

for redundant

recommended.

A parallel installation of force transducers is not recommended for single-component axial thrust measurement. This arrangement reduces the output signal sensitivity and compounds inaccuracies and nonreliabi!ity.

I-6

(6)

The electrical connections standard connectors mounted

can on

be either multipin the transducer outer

case or a flexible cable providing the and shielding for each bridge circuit.

0

required

conductors

(7)

Load range selection should be made such that the transducer is normally operating over the 75 to 90% portion of its full scale range. An overload of 150% of full scale range should produce no degradation in specifications. The ultimate rating for structural failure should be 300% of capacity or greater.

(8)

Derated (downranged) force transducers are used to increase overload capability, increase thrust system stiffness and therefore dynamic measurement response, or extend the static force measurement range to lower values. If derated by a factor of 10:1 or more, the force transducer will probably have to be specially selected and thermally compensated to obtain the desired accuracy.

(9)

Deflection of the force transducer's strain element must be minimized to keep the thrust stand total deflection low and dynamic response high. Total deflection over the full scale load of 0.044 to 4400 N (10 to 1000 ibf) varies from 0.0013 to 0.013 cm (0.0005 to 0.005 in.) depending on the type of strain element used.

(1o)

The natural frequency of the transducer should be several times greater than the thrust stand resonant frequency; a value of 1000 Hz or higher is recommended.

(11)

A safe operating temperature range that is compatible with the test cell environment and that will not cause permanent calibration shift or permanent change in any of its characteristics should be specified for the force transducer. Normal compensated temperature range should be around 0 ° to 66°C (32 ° to 150°F). Maximum operating and storage temperature range should be around -54 ° to +93°C (-65 ° to ÷200°F). Extended temperature ranges are possible with special design provisions. Due to the highly transient nature of the operating temperature that can exist in a test cell, it is recommended that an independent temperature controlled environment be provided for the force transducer. Experience has shown that thermal drift can prove to be the highest single source of error in thrust measurements.

(12)

Barometric test cell transducer

pressure decrease vacuum should not characteristics.

I-7

from cause

ambient to complete any change in

(13)

Material selection for all transducer components should acknowledge possible contact with hydrazine decomposition products. Metal parts which experience temperatures above 93°C (200°F) while exposed to ammonia may be nitrided (Reference I-2). Also, stress corrosion cracking is accelerated under these conditions. An inert gas purge of the transducer case or the surrounding environment will prevent these effects.

(14)

Vibration and acceleration along the load axis resulting from rough engine operations should be considered separately from the static overload requirements. The strain gage mounting and electrical connections are the transducer elements which are most susceptible to these effects. Bonded strain gages with well-designed terminal pads and supported lead wires are recommended.

Electrical

Design

(I)

The

type

of s_rain

_a_e

should

be bonded

metallic

(2)

The number of active strain ga_e bridge arms should be four for a single bridge and eight for a double bridge. A double bridge is recommended for load ranges of 222 N (50 Ibf) and above.

(3)

Recommended excitation should be a regulated voltage of 5 to 28 V dc. Maximum excitation voltage which will not permanently damage the transducer should be 20% or greater than the rated voltage.

(4)

InDu_ and output resistance for dc excitation in ohms at a specific temperature in °C (OF). values range from 120 to 350 ohms.

(5)

Electrical connectiQn_ for conform to pin designation

each bridge circuit shown in the wiring

foil.

is specified Normal

should schematic

diagram (Figure I-2). The output polarities indicated on the wiring diagram apply when an increasing force is applied to the transducer.

(6)

Insulation resistance is specified in megaohms at a specific voltage and temperature between all terminals or leads connected in parallel and the transducer case. A value of 5000 megohms or greater is recommended.

(7)

Shunt calibration resistance should be specified in ohms for a nominal percentage of full scale output at _ specific temperature. The terminal across which the resistor is to be placed shall be specified.

I-8

O

A

(+) EXCITATION

B

(+) OUTPUT

D

(-)

EXCITATION

E

(-)

OUTPUT

SHUNT

F

CALIBRATION

RESISTOR

I

___jJ CONNECTOR

NOTES: 1.

THE OUTPUT POLARITIES INDICATED ON THE WIRING DIAGRAM APPLY WHEN AN INCREASING ABSOLUTE PRESSURE iS APPLIED TO THE PRESSURE PORT (SENSING END) OF AN ABSOLUTE PRESSURE TRANSDUCER. FO R DIFFERENTIAL AND GAGE PRESSURE TRANSDUCERS, THE INDICATED POLARITIES APPLY WHEN THE ABSOLUTE PRESSURE AT MEASURAND PORT IS GREATER THAN THE ABSOLUTE PRESSURE AT THE REFERENCE PRESSURE PORT.

2.

THE BRIDGE ELEMENTS SHALL BE ARRANGED PRODUCING POSITIVE OUTPUT WILL CAUSE IN ARMS 1 AND 3 OF THE BRIDGE.

3.

POSITION OF ANY INTERNAL COMPENSATION INDICATED. SEE APPENDIX III-C.

Figure

I-2.

3.1.2.3 of

performance

measurement

specified, 23

±2°C

pressure

Conventional

they

98

transducers

apply

at

+__.6°F); ±10

(I)

kN/m

the

2

(29

Range

is

End

or

points

citation

are or

SHOULD

BE

Bridge

basic below.

ambient

humidity

usually

compression

(2)

listed

following

+__3 in.

Gage

The

are

relative

NETWORK

Strain

Chgracteristics.

force

(73.4

6-Wire

SO THAT FUNCTIONS INCREASING RESISTANCE

Transducer

performance Unless

parameters otherwise

conditions:

90%

maximum;

temperature barometric

Hg).

expressed tension

in or

expressed

millivolts

I-9

as at

newton

(pounds

force)

both.

millivolts

specified

per volts

volt of

of

ex-

excitation.

(3)

Full scale excitation

(4)

Zero-measured output output at fuI1 rated

(5)

Stability refers to the ability of a transducer to retain its performance throughout its specified operating and storage life.

(6)

L_nearitv is expressed as in direct!on(s) of applied

(7)

Hysteresis is expressed as percent of full scale output upon application of ascending and descending applied forces including rated force.

(8)

Combined hysteresis and linearity are of full scale output upon application and descending forces including rated

(9)

Repeatability is expressed as percent of full over a specified time period with a specified of cycles of load application.

output (FSO) or millivolts

is expressed at specified

as millivolts per volt volts of excitation.

is expressed as percent of full scale excitation and no applied load force.

percent of loading.

full

scale

output

expressed as percent of ascending force. scale output number

(10)

Static error band and repeatability output as referred

(11)

Creep at load is expressed as percent of full output with the transducer subjected to rated for a specified time period.

(12)

Creep recovery is expressed as percent of full scale output measured at no load and over a specified time period immediately following removal of rated force, that force having been applied for the same period of time as specified above.

(13)

Warm-up period the application that subsequent not exceed the

(14)

Static sprin_ (pounds force

is the combined linearity, hysteresis expressed as percent of full scale to a defined type of straight line.

is that time period, starting with of excitation, required to assure shifts in sensitivity and zero will specified percent of full scale output. 90nstant is expressed in newtons per meter per inch) as determined experimentally

or analytically from the dynamic spring mass system representing

(15)

scale force

response the force

of a simplified transducer.

_qNivalent dynamic masses are expressed in kilograms (pounds mass) for both ends of the transducer in the system

described

above.

1-10

(16)

Internal mechanical damping is expressed in newtons per meter/second relative velocity (pounds force per inch/ second relative velocity) between ends at a specified frequency in hertz and a specified dynamic load in newtons '(pounds force).

(17)

Safe overload rating is expressed as an applied force in newtons (pounds force) for a specified time period in minutes which will not cause permanent changes in transducer performance beyond specified static error band.

(18)

Rated axial force

(19)

Thermal sensitivity shift is expressed as percent of sensitivity per specified °C (OF) temperature change over the compensated temperature range in °C (OF).

(2O)

Thermal zero shift is expressed as percent of full scale output per specified °C (OF) temperature change over the compensated temperature range in °C (OF).

(21)

Temperature error b_nd is expressed as output values within a specified percent of full scale output from the straight line establishing the static error band over the compensated temperature range in °C (OF).

(22)

Tem.Perature gradient error is expressed as less than a specified percent of full scale output while at zero load and subjected to a step function temperature change over a specified range in °C (OF) lasting'for a specific time

forc_ of the transducer is the maximum designed force in newtons (pounds force). The rated may be in compression, tension, or both.

period in minutes transducer.

and

applied

to a specific

part

of

the

(23)

Cycling l_fe is expressed as a number of full scale cycles over which the transducer shall operate without change in characteristics beyond its specified tolerance.

(24)

Other environmental CQn_t_ons transducer performance beyond be listed, such as: (a)

Shock,

(b)

High-level

(c)

Humidity

(d)

Corrosive

spray

(e)

Corrosive

gases

which should not change specified limits should

triaxial acoustic

1-11

excitation

(f)

Electromagnetic

(g)

Magnetic

(25)

fields

fields is expressed

as

a specific

(days, months, years) thetransducer in a specified environment without performance characteristics beyond tolerances. (26)

time

period

can be stored changing specific their specifi@d

Concentric angular load effect is expressed as percent of full scale output difference from true output (axially loaded output multiplied by cosine of angle) resulting from a load applied concentric with the primary axis at the point of application and at a specified angle in degrees with respect to the primary axfs.

(27)

Eccentric

an_ular

load

effect

is

expressed

as

percent

of

full scale output difference from true output (axially loaded output multiplied by cosine of angle) resulting from a load applied eccentric with the primary axis and at a specified angle in degrees with respect to the primary

(28)

axis.

Eccentric

load

effect

is expressed

as percent

of

scale output to difference from axially loaded resulting from a load parallel to but displaced specific distance in millimeters (inches) from tricity with the primary axis. (29)

3.1.3

output a concen-

AI_bient pressure effects are expressed as the change in sensitivity and the change in zero measurand output due to subjecting the transducer to a specified ambient pressure change above or below atmospheric.

Calibration

Equipment

Calibration

equipment

for

the

thrust

measuring

system

separated into three types. The in-place static calibrator dynamic calibrator are used on the thrust stand in the test third type involves the laboratory calibration of the force

3.1.3.1

full

_j]m_ce

_atic

Calibrator.

It

is essential

is

and the cell. A transducer.

that

the

thrust

measuring system be provided with in-place static calibration equipment that can produce the same axial deflection on all critical restraints as will be present during the actual engine test. This equipment should be capable of remote operation within the test cell under both pretest and posttest conditions of simulated altitude (vacuum) and temperature and in the presence of all contributing forces including mechanical line and flexure effects, pressurized propellant supply lines, and the

dynamic

influence

of all

supporting

1-12

systems.

static

The following calibrator:

items

should

be

included

in the

design

of

the

in-place

(i)

The calibrator should be either a multipoint dead weight type or a working standard force transducer with a variable force generator.

(2)

The calibration range should be from 0 to 120% of the highest anticipated normal load with values established at three or more intermediate steps.

(3)

The application of the calibration loads should be in both ascending and descending steps that are repeatable in either a preprogrammed or selective manner, so that the transition from one force to the next is accomplished without creating a hysteresis error in the measurement due to overshoot.

(4)

The

|

maximum

inaccuracy

of

the

force

calibrator

not be more than one half the permissible of the measurement force transducer.

should

tolerance

(5)

Traceability (not more than National Bureau of Standards for the force calibrator.

(6)

The calibration force should be applied coincident with the thrust axis of the test engine and in the same direction as the deflection produced by engine operation.

(7)

The calibrator support structure should be independently mounted on the seismic mass, separate from the fixed structure of the measurement force transducer.

(8)

The calibrator force linkage should include a disconnect coupling that will isolate the calibrator from the thrust frame when not in use.

(9)

Provisions of as

(lO)

the the

for adjustment,

calibration measurement

twice removed) to the should be established

alignment

force must force.

and

be given

verification

the

same

emphasis

Protection against damage from shock, vibration, radiation or corrosion caused by the test cell environment should be provided for the calibrator.

3.1.3.2 Dynamic Calibrator. The dynamic response of a thrust stand depends on the stiffness and mass distribution throughout the entire active system. The response characteristic can best be determined by experimentally applying a suitable time-varying force to the complete sxstem and measuring the output versus time response of the measurement force transdu6er. The time-varying of producing

force can _inusoidal

be supplied forces or

by an electromagnetic step function forces.

1-13

forcing coil capable A simpler method is

to use

a single

instantaneous

force

change

of

sufficient

magnitude

to

cause the thrust stand to ring. In either case, data can be developed which provide a measure of thrust stand sensitivity, resonant frequency, and damping factor. The dynamic calibrator should be capable of remote operation with the thrust stand and test cell at simulated engine Operating conditions. The dynamic

force

following

items

should

be included

in the

design

of

the

calibrator:

(1)

The dynamic force should be applied to the thrust frame coincident with the measurement thrust axis and in the same direction operation.

(2)

The

dynamic

as

force

the

deflection

calibrator

produced=by

should

be

the static force calibrator so as not damage to the sensitive equipment.

engine

independent to dause

of

any

(3)

Due to the added weight and complexity, the dynamic calibrator should be disconnected from the active mass of the thrust frame. It may even be removed from the thrust stand completely and only installed when required.

(4)

Magnetic forcing coils should be thoroughly characterized using simulated engine and thrust frame mass before being employed on the thrust stand. The generated force input should be tailored to match the anticipated operating characteristics of test engine thrust pulse whenever possible.

(5)

The application of an instantaneous force change using falling weights, swinging hammer, frangible preloaded linkage, electric solenoid hammer (pinger), etc., should be thoroughly evaluated for causing possible shock overloads to the test engine assembly or the measurement force transducer.

3.1.3.3 Laboratory Calibration. Acceptance and qualification tests should be performed on the strain gage force transducer in a calibration laboratory before the transducer is installed into the thrust stand. The basic equipment consists of a force calibrator, a source of electrical excitation for the strain gage, and a device which measures.the electrical output of the transducer. The error or uncertainties of the laboratory calibration system should be less than one third of the permissible tolerance of the measurement force transducer. Traceability (not more than twice removed) to the National Bureau of Standards should be established for the laboratory equipment. The a laboratory

following

force

is

calibration

a summary system

1-14

of as

the given

design

considerations

in Reference

I-I:

for

(I)

i

3.2

The force calibrator should have a maximum uncertainty of no more than one fifth of that permissible for the measurement force transducer. Typical values for three types of force calibrators in either tension or compression are: (a)

Dead

weight:

(b)

Proving

(c)

Reference standard force error ÷-0.1% full scale.

ring:

maximum

error

maximum

error

±0.01% +_0.1%

transducer:

test

load

full

scale

maximum

(2)

The range of the instrument supplying the calibration force should provide accuracy to 125% of full scale range

(3)

A stable source of electrical excitation of accurately known amplitude is required for the strain gage bridge circuit. DC excitation is normally provided by electronically regulated power supplies utilizing line power. The maximum uncertainty for these excitation power sources should be ±0.02% of reading or better.

(4)

A digital electronic voltmeter with preamplifier is normally used to measure the electrical output signal of the force transducer. The maximum uncertainty for this type of instrument is (a) for 0 to 10 mV range with I _V sensitivity maximum error ±0.02% of reading or +_2 _V, whichever is greater or (b) 0 to 100 mV with 10 wV sensitivity maximum error +_0.01% of reading or ±10 _V, whichever is greater.

ELECTRICAL

AND

ELECTRONIC

or monitoring the necessary of the transducer.

COMPONENTS

The major electrical and electronic components to be considered in the design of a thrust measurement system include (I) signal conditioning equipment, (2) electrical calibration equipment, (3) recording equipment, (4) visual display equipment, and (5) data processing equipment. These components are shown in the thrust measurement system block diagram, Figure I-3. In general all of these components are commercially available, off-the-shelf items. Most of the items are available from more than one manufacturer. The major concern in the selection of these components must be the evaluation of the various manufacturers' general specifications in relation to the specialized force measurement requirement. A subsequent verification that the equipment finally selected conforms to the manufacturers' specifications is essential.

3.2.1

Signal

Conditioning

Equipment

Signal conditioning equipment includes the following functional devices: power supplies, amplifiers, electrical cabling, shielding, signal d£stribution and switching network, and filters. The regulation and stability

1-15

ENGINE ROCKET ASSEMBLY

I

J

CA LIBRAT IO N DYNAMIC SYSTEM

CA LIBRAT ION SYSTEM STATIC

t

J

FRA/vI£ THRUST

J

J

MECHANICAL COMPONENTS FORCE TRANSDUCER MEASUREMENT

1

ELECTRICAL AND ELECTRON!C COMPONENTS

CALIBRATION E I..ECTRICA L EQUIPMENT

t

SIGNAL CONDITIONING EQUIPMENT

i

I RECORDE R OSCILLOGR1APH

/_,NALOG

GRAPH IC RECORDER

1

, FfM

DIGITAL ANALOG-TORECORDER

RECORDER

VISUAL , DISPLAY

J

Figure

I-3.

Thrust

Measurement

i-16

DATA

System

PROCESSING

Block

EQIJIPMENT

Diagram

I

of this equipment should be ±0.05% or better, wherever applicable. The design of these devices varies widely depending on system philosophy and economics; however, certain design principles are universally recommended as follows:

(1)

PoweY Supplies. Constant voltage excitation is the primary type used with hlgh-accuracy thrust measurement systems. Power supplies can be individually rack-mounted units or miniature (several in one card) devices integral with other signal conditioning equipment. Generally, there are provisions for voltage adjustments, less often for zero balance. Ripple should be less than 100 MV peak to peak.

(2)

Amplifiers. The use of high-quality differential amplifiers is now almost universal. With a transducer full scale output of 20 to 40 mV, an amplifier gain of 50 to 500 is sufficient for most conventional analog-todigital conversion and recording systems. It should be verified that peak common mode voltages do not exceed the rejection limits of the amplifier.

(3)

Electrical Cablin_ and Shielding. Electrical noise can be minimized by the use of proper shielding and grounding techniques (Reference I-3). Transmission cables between the transducer and the recording system usually consist of multiple pairs of twisted, shielded, splice-free conductors. A total of 6 conductors should be used for each transducer. The wire gage and corresponding resistance of the excitation and calibration leads should be taken into account when developing calibration techniques and other system design considerations. Each transducer cable should be individually shielded, with continuity of shield to the operational amplifier. The shield grounding connection should be in accordance with the amplifier manufacturer's recommendations. Multichannel cables consisting of inner cable shielding, and overall shielding of the large cable are recommended for long transmission runs. The outer shield of the multiconductor cable should also be terminated at a single point ground. The outer shield and all shields should be insulated from each other.

(4)

e

inner

Other signal conditioning eauipment includes such items as filters, distribution and switching units, and impedance matching devices. The design of these and related devices varies depending on system philosophy, but should in all cases be high-quality equipment providing stability (both with time and temperature), line voltage regulation, and linearity. Thermally induced errors should be minimized in all circuits.

1-17

3.2.2

Electrical

Calibration

Equipment

Some form of electrical simulation of the transducer response to force should be provided. This simulation should track any change in the system sensitivity that is caused by changes in the environmental conditions. The two most commonly used electrical calibration systems that are readily adaptable to automated periodic tests are discussed below. The first of these techniques includes the transducer in the calibration and is thus quasi end to end. The other involves only the:electrical and electronic equipment. The advantages (convenience, technical, or economic) of each system will largely depend upon the user's existing transducers, signal conditioning equipment, cabling, etc.

3.2.3

(i)

Shunt calibration with a constant voltage system requires a 6-wire system to the transducer if an external signal shunt resistor is used: 2 wires are used for excitation, 2 for output, and 2 for shunt simulation; The technique for using a 6-wire shunt resistor calibration method is presented in Appendix III-C.

'(2)

Voltage substitution techniques can be used to calibrate the electronics system (amplifier, recorder, etc.) in addition to, or in lieu of, any transducer electrical or end-to-end calibration. This method requires that the transducer be electrically disconnected (usually by a switching network) and a known voltage substituted. Such a calibration technique will not necessarily provide any information about changes in ambient output nor will it even reveal if thetransducer has been disconnected. It should therefore not be the only type of electrical calibration employed.

Recording

Equipment

• The four commonly used recording systems for recording thrust measurement, data are (I) digital system, (2) graphic recorders, (3) oscillograph and (4) analog magnetic tape recorders. Two or more of these systems may: be combined to provide high accuracy, high-frequency response, and quick readout.

3.2.4

Visual'Display

Equipment

A visual display of real time measured data in engineering units along with other critical operating parameters is required for both pretest and posttest calibrations and for monitoring during the engine test. This alphanumeric data can be presented in either hard copy (printed) or non-hard-copy (no record) form or both. The non-hard-copy is usually displayed on some type of cathode ray tube (CRT) device through a selective preprogrammed format.

1-1S

3.2.5

Data

Processing

The exclusively

data

to

many

other

with

care

the

processing thrust

parameters so

Equipment

that

also.

the

equipment

measurement This

is

not

system, equipment

uncertainty

of

the

generally

but

is

should data

is

dedicated

used

be not

to

chosen

process and

increased

used

during

processing.

4.0 4.1

INSTALLATION

COMPONENT

All should

be

the

critical for

This

all

data

as

transducers such

tests

compliance force one

working-standard

(3)

Calibrator

dead

(4)

Thrust

stand

flexures

(5)

Thrust

stand

restraints

(6)

Dynamic

Force

Transducer

thrust

in makes

may

be

transducer the

Acceptance those

parts, to the

assembly, next.

The I-I

are

summarized

as

transducer is

to

tests

I-I.

for

1-19

(Where

might

the

a vary

force

quantity

of

able

certify

to

working-standard

of

tests of

considerably

transducer

certi-

difficult,

force

function

be

recording

testing The

uncertainty

acceptance

and

the

is

calibrator

should

tests

measurement

are

the

used,

units.)

an

the

which

follows:

be

manufacturer

of

and

to

and

qualification

similar

Individual

adjustment,

acceptance

plus

certified

transducer

qualification

the on

certified

Test.

force

one

of

tolerance

characteristics or

if and

provided be

inspection so

transducer

Reference

testing

should

to

force

justification

permissiSle

4.1.1.1 evaluate

ISA-$37.8,

waived

precision

system before

calibrator

acceptance

previous

measurement

specifications

weights

transducer,

the

used

force

measurement

force given

force

thrust

Components

Calibrator

measurement

the

by

evaluation. items:

(e)

from

half

accomplished

test and following

performing

PROCEDURES

design

Thrust

working-standard by

best

of

with

(i)

The

fied

components

compliance

is

standard laboratory should include the

4.1 .I

CHECKOUT

CERTIFICATION

certified

installation.

AND

not

more

than

transducer.

are

performed

transducer from

from

one

piece unit

Reference

(i)

(2)

Inspect the transducer for mechanical defects, finish and improper identification markings. Install

the

transducer

into

the

force

with axial alignment as specified Connect the excitation source and

poor

calibrator

by the manufacturer. readout instrumenta-

tion to the transducer and turn on for the specified warm-up period. Prior to calibration, it is desirable to exercise the force transducer by applying rated load and returning to zero load for several cycles.

(3)

(4)

(5)

Conduct two or more calibration cycles in succession, including five to eleven points in both ascending and descending directions while monitoring excitation amplitude and recording output signal. From the data obtained in these tests the following transducer characteristics should be determined: (a)

End

points

(b)

Full

scale

(c)

Zero

unbalance

(d)

Linearity

(e)

Hysteresis

(f)

Hysteresis

(g)

Repeatability

(h)

Static

,

and

error

linearity

combined

band

Repeat the calibration cycles over a specffied period of time after warm-up. This data establishes the following characteristics for that period of time: (a)

Zero

drift

(b)

Sensitivity

drift

Apply the rated force to the transducer during a specified short period of time. The measurement of changes in output at constant excitation during the time period should establish: Creep

...

output

at

load

,

(6)

At zero

load,

measure

output

and

sensitivity

over

a period of time, up to one hour, starting with the application of excitation to the transducer. The observed time to stabilize should determine the following

characteristic:

1-20

Warm-up

(7)

B

Apply the specified rated overload for the specified number of times in the specified direction of tension or compression, followed by one complete calibration cycle to establish that the transducer performance characteristics are still within specification. This should verify: Safe

(8)

period

Measure

overload

the

rating

insulation

resistance

between

all

terminals,

or leads connected in parallel, and the case of the transducer with a megohm-meter using a potential of 50 V, unless otherwise specified, at room temperature. This should establish: Insulation

(9)

resistance

A Wheatstone bridge (for dc) or an impedance bridge (for ac) should be used to measure and establish the following: (a)

Input

(b)

Output

impedance impedance

4.1.1.2 Qualification Test. Qualification tests are performed to evaluate those characteristics which are a function of transducer design. They thus would not be expected to vary appreciably from one unit to another for a particular transducer model. The performance of a representative sample of units should represent the performance of an entire lot.

I-I)

are

The qualification tests summarized as follows: (I)

The

force

for the

transducer,

force

while

transducer

still

installed

(Reference

in the

force

calibrator, should be placed in a suitable temperaturecontrolled chamber. After stabilizing the chamber and transducer at a specified temperature, one or more calibration cycles should be performed within the chamber. The procedure should be repeated at an adequate number of selected temperatures within the specified operating range of the transducer, and finally after return to room temperature and stabilization. From these tests the following characteristics should .be determined:

(a)

Thermal

sensitivity

(b)

Thermal

zero

(c)

Temperature

shift

shift error

1-21

band

(2)

With the force transducer at room temperature within the controlled chamber, and with no applied load, it should be subjected to a specified thermal transient above or below room temperature. The observed output over a specified period of time establishes: Temperature

(3)

Install

the

transient

force

error

transducer

into

a suitable

test

fixture with the axial alignment as specified. Attach an electromagnetic forcing coil which is capable of producing an axial load which is 20% of the force transducer rated 10ad or higher. Connect the excitation source, readout instrumentation, and recorder and turn on for the specified warm-up period. Apply a sinusoidal force at a specified load and sweep the frequency from zero This

until the first resonant peak should establish transducer:

(a)

Natural

(b)

Frequency

Apply time

a step period.

resonant

output

is

reached.

frequency

response

function The

(a)

Natural

(b)

Static

(c)

Damping

(d)

Equivalent

force

recorded

resonant spring

at

a specified

output

should

load

and

establish:

frequency

constant

factor dynamic

masses

After completion of the above test, remove the transducer from the test fixture and reinstall it into the force calibrator. Perform one complete calibration cycle to verify the satisfactorily.

(4)

ability

of

the

transducer

to

perform

Install the force transducer into a suitable vacuum chamber with the axial alignment as specified. Connect the excitation source and readout instrumentation to the transducer and turn on for the specified warm-up period. With the transducer at room temperature and no applied load, reduce the barometric pressure within the test chamber in a controlled manner to a specified level below atmospheric and hold. Observe the output over a specified time period to establish: Ambient

pressure

effects

After

completion

of

test,

remove

transducer

the

two or

1-22

/

more from

cycles the

of the vacuum

above

chamber

and

reinstall

into

the

force

calibrator.

Perform

one complete calibration cycle to verify ability of the transducer to perform satisfactorily. O

(5)

Install

the

force

transducer

into

a suitable

test

fixture with the axial alignment as specified. Mount this test assembly onto a vibration and/or shock test machine in the axial loading direction as specified. Connect the excitation source and readout instrumentation to the transducer and turn on for a specified warm-up period. With the transducer at room temperature and zero initial applied load, subject the transducer to a specified series of vibration and/or shock tests

i

at prescribed output during establish: Vibration

frequency and g loading. each of the specification

and/or

shock

effects

After completion of the above test, from the test fixture and reinstall calibrator. Perform one complete verify ability of the transducer

(6)

Observe the tests to

remove the transducer into the force

calibration cycle to to perform satisfactorily.

To determine the effects of concentric angular loading (and side loading), insert wedge blocks above and below the force transducer installed in the force calibrator as shown in Figure I-4a. The angle subtended by the two larger surface areas (b) of each block should be equivalent to the specified angle of interest and should result in the specified side load. Apply rated load and as soon as stabilized, read output and remove the load. A comparison of pretest and posttest zero measurand should establish: Concentric

(7)

loading

effects

I

To determine the effects of eccentric angular loading, remove the upper wedge block as shown in Figure I-4b. Apply rated load and as soon as stabilized, read output and remove the load. A comparison of pretest and posttest zero measurand should establish: Eccentric

(8)

angular

angular

loading

effects

I

To determine the effect of eccentric loading, wedge blocks, install a flat load button into

IThe effects of the various types of loading related conditions can be determined in accordance with the in Figure I-4.

1-23

remove both the transducer,

to axial loading expressions included

c

_u

_< L

\ \

Z U

,..l_

Z

<

-x

>.0

a 8 o <

8

.....

z

\ \

u

c _.-Z

J_

w

c 0

b f_,"l

o_

I o

,.f e-

0

z

113

o

_,_

! -O,--

\

< u

_J

w

,

Z u

i

I

|

I

o_"I

z

,-.1

O

1.0

DAMPING COE'FFICIENT " C

0.6 I=,-

_o _

0.4

IO I

-....4

0.2

,

o 0.1

o -

0.2

0.3

0.4

0.5

0.6

0.7

I

0.8

0.9

1.0

DAMPING RAI"IO, h

Figure

NATURAL

'Damping

pressure

system

containing

transducers)

the

a

where fn constant

is of

at

the

which

called

the

do

free

the the

output

the

natural

not

the

The

natural

of

at at

I/v_,

damping,

no

response

occurs

real

the peak

maximum is

shown

is

often at

Only

natural the

90 ° .

if

in

does

term

reality, affect

applied be

this the

a

(typical

by:

the as

(fn)

the

spring the frequency

is

damping

is at

Figure

3E-6

at

to

damping As

the

occurs zero

all. III-E-7.

a

sometimes

has

period

at

transducer

frequency

maximum

response

response exists

restraint

given

and k is be defined

This

In

frequency.

peak

spring is

nothing which

frequency).

frequency

which

the

but

will

frequency.

occur

frequency

ratio

Overshoot

(III-E-3)

by

input

there

a

of the system It may also

input

(ringing

sinusoidal

a maximum.

response the

a

recorded,

and

frequency

freauencv.

frequency

occur

If is

the

natural

oscillations

at

From

= u 2=

frequency mass m.

lags

undamDe_

with

output is

natural suspended

mass

natural

fn

to

Ratio

FREQUENCY Ina

of

III-E-6.

The

at

and

which

is

the

is

zero

does

damping

is

is

resonant

lowered

frequency. frequency

at

response frequency,

the

maximum

increased, and,

For

the

the

at

a damping

greater

which

maximum

[

I

I

I

I

I

I

1.0 0.8 z 0.6

Z

0.4

°,9, I 0.2

0

I

I

I

I

J

I

0.1

0.2

0.3

0.4

0.5

0.6

IL

1

0.7

O.B

DAMPING RATIO, h

Figure

III-E-7.

If to

execute

decay to the

a

is

it.

transducer

typical

This

is

frequency the

of

oscillation

of

natural

the

frequency)

oscillatory

transient

As and,

nature

of

transient

the at

the

a

oscillation

I

I

I

I

a

is

and

freauency

ratio

at

a

in

I

allowed the

may zero

be

of

(by

The

I

1.0

(5 0.8 Z

8 _

o.6

u.

0 z

RI

5 o.4 _z 0.2

0 0

I

i

I

I

I

I

I

I

i

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

DAMPING RATIO, h

Figure

III-E-8.

Ringing

3E-7

Frequency

vs

Damping

same

definition),

III-E-8.

]

is

freouency

disappeared.

Figure

I

assigned the

the

unity

transient

damping

freauency)

entirely

plotted

then

that

increased,

has

I

Ratio

found

(ringin_

damping

is

be

Only

dampln_

transient

Dampin_

displaced may

and

frequency.

decreases

of

it

natural

frequency.

oscillatory

frequency

the

vs

is

transient,

(ringing

not

Frequency

diaphragm

damped

oscillatory

as the

the

Resonant

Ratio

1.0

FREQUENCY RESPONSE (AMPLITUDE) The amplitude of the system transfer function versus frequency is often referred to as the frequency response. It is freouently normalized

to

show

deviations

illustrates with

the

various

response there

damping

of is

a

a

single

system

(h

mined

<

by

approximation can

be

step

this

input

slightly the

Assume

than ratio

i

the

from a

is

a

good

sinusoidal

Figure order

III-E-9 systems

representation pressure

frequency

the

curves

and

natural

step

of

the

variations

response of

of

Figure

input

and

an

if

underdamped

III-E-9

frequency

pressure

a

40% h

I I I

a

(Figure

can

flush

ringing be

III-E-3).

determined

i

mounted

once

have the

transducer

frequency

_

of

1000

From to

been

analysis

be

Hz

the

whose with

curve

the determethods

response

to

overshoot

of

Figure

III-E-6

in

approximately

0.4.

T

I

2.0

Knowin_

I

the

I

h=C

-

1 1.5

one. second

frequency.

ratio, of

of of

appendix.

indicates

less

damping

made

ratio input

plot to

of

damping

Example: a

This

resonant

application

in

amplitude

sinuscidal

transducer

major

1.0)

the

a

ratios.

frequency,

described

an

to

pressure

An

ringing

from

response

h=0.3

:0

AMPLITUDE RATIO = V( I-/32) 2 + f2hB) 2 h=0.5 h = 0.707

/9= THE RATIO OF THE VARIABLE INPUT PRESSURE FREQUENCY, f, TO THE SYSTEMNATURAL FREQUENCY, f n

I 0.06

_ I I 0.08 0.I

i 0.15

0.3

0.2

0.4

0.5 0.6 0,7

1.0

I .5

2.0

FREQUENCY RATIO B = f/fn

Figure

III-E-9.

Frequency

Response

3E-8

of

a Second

Order

System

3.0

damping

ratio

III-E-8) Figure of

and

is III-E-9

1100

the

it

They

will

be

with

less

than

response

to

10%

can

be

ringing be

can

output

In a

the

found

frequency,

approximately

be

shown

readings high

at

case

10%

overshoot,

of

about

fn

(440

Hz)

an

overdamped

from

the

by

f3dB

50%

during

(3 a

is

the

frequency

dB)

and

T is

test.

While

transducer

under

conversion

is

the plus

95%

by

time

III-E-I,

time

this

with

5%

a

at

high

critically time

Using

natural

0.8 at

(±10%)

(Figure

Hz. fn

0.25 damped

for

the

frequency or

880

fn

(275

the

transducer,

data:

output

amplitude

of

transducer

it T in

3-9).

Hz).

(III-E-4)

the

can

conditions,

Hz.

frequency

I : T

constan_

(Reference

1100

high

response

which

replacing

40% and

frequency

or

value

relationship

test

obtained

response

Figure

this

ideal

at

the

natural

system

or

a coarse

determined

a

be

f3dB where

for

will 0.4

the

that

the 1000/O.91

be

appears

the See

applied

as

to

that

above also

is an

a more

equation, Rise

and

reduced measured ideal realistic with

t95%,

Response

Time

appendix.

REFERENCE

III-E-I.

Burns, Statham

J.,

and

Rosa,

Instrument

G., Notes,

3E-9

CalibratiQn Number

and 6,

Test

December

of 1948.

Accelerometers,

SECTION

TEMPERATURE

e

IV

MEASUREMENT

SECTION TEMPERATURE

IV

MEASUREMENT

CONTENTS D

f

1.0

INTRODUCTION

4-I

2.0

SCOPE

4-I

2.1

OBJECTIVE

4-I

2.2

LIMITATIONS

4-2

3.0

DESIGN

4-2

3.1

TEMPERATURE

3.1.1

Transduction

3.1.2

Performance

3.1.3

Mechanical

Design

4-7

3.1.4

Electrical

Design

4-11

3.2

ELECTRICAL

AND

3.2.1

Signal

3.2.2

Electrical

3.2.3

Recording

3.2.4

Visual

3.2.5

Data

4.0

PERFORMANCE

4.1

TRANSDUCER

4.1 .I

Visual

Inspection

4.1.2

Range,

Output,

4.1.3

Repeatability

o

CONSIDERATIONS TRANSDUCERS

U-2

Element

_-2

Characteristics

ELECTRONIC

Conditionin_

4-5

COMPONENTS

Eauipment

Calibration

4- 16

Equipment

Processing

4-16

Eauipment

4- 16

VERIFICATION TESTING

and

4-12

Equipment

Eauipment

Display

4-12

AND

2-16 CALIBRATION

4-16 4-18

Error

Limits

4-18 4-18

4.1.4

Insulation

4.1.5

Dynamic

4!1.6

Proof

4.1.7

Thermoelectric

4.1.8

Vibration

4.1.9

Other

Surface

4.1.10

Other

Environmental

4.2

SYSTEM

4.3

STANDARDS

4.3.1

Temperature

4.3.2

Readout

5.0

OPERATING

5.1

PRETEST

5.2

POSTTEST

6.0

DATA

6.1

CALIBRATION

6.2

RUN

7.0

GLOSSARY

4-26

8.0

REFERENCES

4-30

4-18

Resistance

4-18

Response Pressure

and

4-19 Potential

4-19

Acceleration

4-19

Temperature

Transducer

Tests

Tests

4-20 4-20 4-20

CALIBRATION

4-21 4-22

Source

4-23

Instrument

4-23

PROCEDURES PROCEDURES

4-23 4-24

PROCEDURES

ACQUISITION AND

AND

PROCESSING

VERIFICATION

TECHNIQUES

4-24 4-24

DATA

DATA

4-25

APPENDIXES IV-A

IV-B

TEMPERATURE MEASUREMENT UNCERTAINTIES

SYSTEM

ELEMENTAL 4A-1

TABLES AND EQUATIONS FOR USE AND RESISTANCE THERMOMETERS

4-ii

WITH

THERMOCOUPLES 4B-I

4-I

Temperature Measuring System

4-2

Basic ThermocoupleCircuit

4-3

Measuring Circuits Transducers

for Resistance Thermometer

IV-B-I

Characteristics

Common

IV-B-2

Callendar-Van

IV-B-3

Thermocouple Materials, Type Letters, and Color Codes for Duplex Insulated Thermocouples and Extension Wires

4_-3

Fixed Points Thermocouples

4B-4

4-14

Tables

IV-B-4

of Dusen

Thermocouple

Materials

Equation

Available for Calibrating and Resistance Thermistors

f

4-iii

4B-I 4B-2

SECTION IV TEMPERATURE MEASUREMENT 1.0 INTRODUCTION Recommended practices are outlined for the design, installation, checkout, calibration, and operation of a temperature measuring system to be used during tests of a liquid monopropellant rocket engine. Twoappendixes are included: IV-A, Temperature MeasurementSystemElemental Uncertainties, and IV-B, Tables and Equations for Use With Thermocouples and Resistance Thermometers. 2.0

SCOPE

This section has been written to serve as a guide for the experienced engineer in the design, installation, and operation of a temperature measurementsystem for measuring the temperatures related to performance evaluation of a liquid monopropellant rocket engine. Design guidelines rather than detailed specifications are provided for the critical componentsof each portion of the system. These guidelines, used in conjunction with current state-of-the-art, commercially available equipment and good engineering practices, will provide an optimum temperature measurement system which meets the performance criteria specified.

2.1

OBJECTIVE

Temperature measurements are made at a number of locations in a monopropellant rocket engine test system, including propellant storage tank, propellant supply lines, propellant flowmeter, thruster catalyst bed, thruster chamber wall and throat, valves, brackets, and flanges. These measurements have different accuracy requirements. One objective of these recommended practices is to provide the propellant temperature data necessary to obtain the density factor which, together with compressibility effects, is required to determine propellant mass flow from simultaneously obtained volumetric flowmeter measurements. In order to do this within the required uncertainty limits for flow, propellant temperature must be determined to within ±0.56°C (±!°F) over the range from 0 ° to 80°C (32 ° to 176°F). Nozzle throat and thrust chamber temperatures, for performance calculations, should be measured to within the range from 705 ° to 871°C (1300 ° to 1600°F).

will

depend

The importance on the user's

attached interest

4_I

when used ±1.2% over

to other temperature measurements and the purpose of the tests.

2.2

LIMITATIoNs

These practices are limited to temperature measurements made with thermocouples and resistance thermometers. I Although not restricted to the Measurement of steady state values, the response of thermocouples and resistance thermometers usually limits temperature measurement to an average of that produced by a pulse train when the engine is operated in the pulsed mode. These direct measurement gas composition.

practices do not of temperatures

3.0

DESIGN

include related

recommendations concerning the to the determination of exhaust

CONSIDERATIONS

A temperature measuring system capable of obtaining accurate data requires that careful consideration be given to selecting and assembling the transducer 2 with its supporting electrical and electronic equipment. The type of transducer and the manner in which it is installed along with the effects of environmental conditions are important from the mechanical viewpoint." Electrical and electronic components include signal conditioning, electrical calibration, recording, visual display, and data processing equipment. They are shown as a block diagram in Figure 4-I.

3.1

TEMPERATURE

TRANSDUCERS

Thermocouples are used for the great majority of temperature measurements on monopropellant rocket engine test systems. This is because they are easy to use, economical, and provide sufficient accuracy for most applications. The resistance thermometer may provide greater accuracy in those cases where measurement Uncertainty is dominated by thermocouple inaccuracy wherever greater accuracy is required. applications may employ such types of transducers pyrometers and temperature sensitive photographic

3.1 .I

Transduction

A

few special measurement as thermistors, scanning film.

Element

3.1.i.1 _j_. Thermoelectric sensing elements are used in thermoCouple circuits. A basic thermocouple circuit, as shown in Figure 4-2, consists of a pair of conductors of dissimilar metal welded or fused £ogether at one end to form a measuring Junction and connected via transmission lines to a reference Junc{ion which is maintained at a well-defined temperature. The circuit is completed with signal conditioning or recording equipment.

IThe resistance bulb (RIB) and

thermometer is also referred as a resistance temperature

2Transducer and sensor can convert physical phenomena

to as a resistance transducer (RTD).

be synonymous words describing devices into measurable electrical signals.

4-2

temperature

which

ROCKET ENGINE

..... ]

[

I

(MECHANICAL

COMPONENTS'

RESISTANCE TH ERMOMETER

THERMOCOUPLE (ELECTRONIC

COMPONENTS)

PRECISION RESISTANCE OR VOLTAGE SUBSTITUTION

REFERENCE JUNCTION

PRECISION VOLTAGE SUBSTITUTION

BRIDGE COMPLETION

CONSTANT - OR

-

NETWORK

CURRENT POWER SUPPLY

If SIGNAL CONDITIONING COMMON EQUIPMENT

1 VISUAL DISPLAY EQUIPMENT

DIGITAL SYSTEM RECORDER

! DATA PROCESSING EQUIPMENT

constructed

Figure

4-1.

By

using

various

to

cover

the

copper/constantan-type S.

temperature

limit

for a in

See

8

AWG

Table

thermocouples;

wire

IV-B-I

to

Table

for

a

chromel/constantan, No.

types

of

+1538°C in

are

primarily

limits

are

thermocouples -253°C with

Appendix

example,

with

decreases for

intended

a

No.

for lower

Junctions.

4-3

from 28

AWG

can

exposed

with

platinum/platinum-t0% The wire 1260°C wire.

enclosed-element for

be

(-424°F)

IV-B.

decreases

(1600°F)

somewhat

System

from

(+2800°F)

IV-B-I

871°C

metals range

thermocouple for

to

Measuring

measurement T

rhodium-type

Temperature

recommended size.

upper The

limit

(2300°F) Limits

for shown

(protected) (bare

wire)

sensing

When used within their optimum ranges the uncertainty values will generally be I% of reading or less with standard materials, construction, etc., down to less than 0.5% of reading with special materials, maximum purities, etc. The Type S thermocouple is the standard by which the international temperature scale from 660 ° to I063°C (1220 ° to 1945°F) is defined by the International Practical Temperature Scale. The

temperature

sensitive

element

in

a thermocouple

may

be made

arbitrarily small thus facilitating precise measurement of temperature a point. The low thermal capacity of the element, resulting from this size, insures quick response. (See Paragraph 3.1.3.1, item 6.)

at small

3.1.1.2 Resistance Thermometers. A resistance thermometer usually consists of a coil or grid of temperature sensitive wire whose resistance, when exposed to the temperature to be measured, varies in a precise and predictable manner. The auxiliary irlstruments which are used to measure these changes in resistance generally consist of a Wheatstone bridge with constant voltage excitation or a constant current with voltage readout proportional to resistance. The resistance thermometer is regarded as the most precise and reliabie device for the range -190 ° to ÷660°C (-310 ° t_ +1220°F). In the vicinity of -18°C (O°F), or at room temperature, measurements with an uncertainty of less than 2.8 x I0-4°C (5 x I0"4°F) can be made; however, the error is normally several thousandths of a degree. At 316°C (600°F)the uncertainty is about I/I0°C or I/5°F.

i

0

LO CONDITIONING AND RECORDING EQUIPMENI

REFERENCE JUNCTION

0

jHERMOCOUPI_E WIRE

Figure

E×TENSIO_ WIRE

4-2.

O

-- COPPER

Basic

TRANSMISSION

Thermocouple

/

4.4

WIRE---e,

Circuit

A winding of pure, strain-free, annealed platinum wire is widely used in transducers for precise temperature measurement. An element of this type is used to define the International Practical Temperature Scale between the limits of -183 ° and +630°C (-298 ° and +1165OF). An element wound from pure nickel wire or from nickel alloy wire such as "Balco" is used +300°C (-148 ° to +572°F); it

3.1.1.3

Thermistors.

A

in the medium temperature range -100 o to is less costly than a platinum wire element.

thermistor

is a semiconductor

whose

resistance

varies strongly with temperature. The semiconductor materials, usually sintered mixtures of sulfides, selenides, or oxides of metals such as nickel, manganese, cobalt, copper, iron, or uranium, are formed into small glass-enclosed beads, disks, or rods. They have high resistivities and high negative temperature coefficients of resistance. Their resistancevs-temperature characteristics are not linear, and it is difficult to maintain narrow resistance tolerances during manufacture. A thermistor must be individually calibrated and is inclined to drift; however, its wide variation in resistance and extremely small size make it desirable for certain applications. The thermistor is generally powered by a few microamps from a constant current source. The resistance is then inferred from voltage measurements. A thermistor is normally used over the temperature range of -75 ° to +250°C (-103 ° to +482°F).

3.1.2

Performance

Characteristics

The transducer performance characteristics (or properties) which are of greatest interest to the user are listed below. A brief commentary and suggested specifications are included where applicable. Unless otherwise specified they apply at the following ambient conditions: temperature 25 ±I0°C (77 ±18°F); relative humidity. 90% maximum; barometric pressure 73 _+7 cm Hg (29 ±2.8 in. Hg).

3.1.2.1 range over frequently capability.

Ra_. Range is usually specified as a nominal temperature which all other performance characteristics apply. It is selected as a range narrower than that given by the transducer's

3.1.2.2 Overload Temoerature. Overload temperature is the maximum or minimum temperature which is beyond the specified range limit, but to which the transducer can be exposed without incurring damage or subsequent performance changes beyond stated tolerances.

3.1.2.3 Ou__u_ID/_. Output can be stated as nominal full-scale output over the transdueer's span between its range limits, e.g., "Full-Scale Output: 36 mV (with reference junction at 0°C) '' or "Full-Scale Output: 250 ohms." Since most temperature transducers have a nonlinear outputvs-temperature relationship, the variation of output over the range

4-5

is best described by a table listing output values at several temperatures including the range limits. The curve established by such a table is often referred to as a theoretical or reference curve. This curve is often based partly or wholly on empirical data. 3.1.2.4 _. Repeatability and bias are usually the only steady state static accuracy characteristics specified for temperature transducers. Linearity is rarely specified since the reference curve of a large majority of temperature transducers is inherently nonlinear. Hysteresis and friction error are virtually nonexistent in temperature transducers. Repeatability, the maximum difference in repeated output readings from one another, can be expressed in percent of full-scale output but is usually stated in output units or output-equivalent .temperature units, e.g., "Repeatability: within 0.01°C ''or "Repeatability: within 1.0 ohm" or "Repeatability: within 0.5 mV." Repeatability has also been expressed in percent of reading (percent of reading-equivalent temperature correlated on the basis of a reference curve), e.g., "Repeatability: within 0.5% of reading." The tolerance specification can be followed by a statement of the period of time over which it is considered applicable. 3.1.2.5 Calibration Interchan_eabilitv. The maximum deviation over the specified range of the calibration curve of any one transducer from a reference curve is established for a group of transducers. A reference curve is often established for a certain transducer part number. Calibration interchangeability then applies to all transducers identified by this part number. It is normally expressed in the same terms as repeatability but with bipolar tolerances, e.g., "Calibration Interchangeability: Within +--2.0 ohms." Calibration interchangeability tolerances can be specified as larger in some portions of the range than in others.

3.1.2.6 Conduction Error. Conduction error iscaused by heat conduction between the sensing element and the mounting of the transducer. It occurs primarily in immersion probes, especially when the stem is short. Conduction error can be specified as the maximum difference in output reading when the transducer is first immersed, to just below the electrical connections, in an agitated temperature bath and when it is immersed up to the mounting fitting while the fitting and leads are artificially cooled or heated so that it attains the specified environmental temperature. The difference between sensing.element and environmental temperatures should be chosen as large as is estimated will occur in the end-use application of the transducer.

3.1.2.7

MQunting

Error.

Mounting

error

tolerances

(also

referred

to as strain effects or strain error) should be specified for surface temperature transducers. This error is introduced mostly by strain in the transducer after it is welded, cemented, or otherwise attached to a surface. It is specified as the maximum difference in output reading before and after mounting the transducer to a sample surface by a specified mounting method.

4-6

3.1.2.8 Time Constant. The time constant is an important dynamic performance parameter of an ideal transducer having a first order characteristic. It is specifically defined as the length of time required for the output of the transducer to rise to 63.2% of its final value as a result of a step change in temperature.

3.1.2.9 Resoonse Time. The time required for the transducer's output to rise to a specified percentage of its final value (say 98 or 99%) under the same test conditions as applicable to time constant determination. The limits of the step change in temperature and type and flow rate of the measured fluid at both limits must also be given, e.g., "from at I m/s."

still

air

3.1.3

Mechanical

at

25 +_5°C to distilled

water

at

80 ±2°C

moving

Design

The mechanical design of a temperature measuring system includes consideration of the characteristics of the type of transduction method selected and installation of the transducer in the system so as to obtain accurate measurement of the test item or medium with minimum effect on its temperature. These factors are discussed in the following paragraphs.

3.1.3.1

Thermoco_ple$

(i)

The performance of a fine gage thermocouple deteriorates more rapidly at elevated temperature than does that of a heavy gage thermocouple. The wire not only physically deteriorates, but the calibration of the wire irreversibly changes.

(2)

Thermocouple materials are normally furnished to a standard accuracy or calibration. There is usually an extra charge for both special accuracy and calibrated wire. The limits of error for standard and special accuracy are given in Table IV-B-I. No standardized limits have been established for calibrated wire.

(3)

Since spurious emfs are produced by temperature gradients in heterogeneous wire, all purchased lots of thermocouple wire should be checked for homogeneity.

(4)

The thermocouple junction may be formed by any of the following techniques which are presented in decreasing order of preference: electric, gas, or discharge welding, brazing, silver or soft soldering, immersion of the leads in a liquid metal pool, or mechanically forcing the wires into contact. For detailed information on thermocouple construction (both probe and surface installation) see References 4-I and 4-2.

4-7

(5)

In

any

near

junction

the

there

Junction

is

ent from the original as a short length of In order ture must (6)

The may

the

time

have

a time

may

(7)

have

(8)

be

If

response

down

in

splices used

The

(1)

to

large

oven

wire,

of

in

or

to

consistent

500

ms.

If

a'thermocouple

less..

known

thermal

the

gradients

thermocouple

matched

errors

thermal

and

due

block

continuously

thermometers units

The

to

material

materials to

must

gradients

temperature

should

monitored.

wire

should

show

metals

an

cobalt

an

which

be

specific

wound

special surface

available.

in

nickel

size

of

strain-

of

way. for

also

element

sensitive

wire

bonded

flexible,

electrically

4-8

resistance 0.003925.

resistivity, and

R,

then

iron,

Although

platinum

a

good

with

increases

particular

nickel is

resistance thermometer

(1200°F).

thermometer

measurements consists between

to

high-accuracy

makes

649°C

resistance

temperature This

In

standard

equal

linear

this

below

form

of

first

used

the

(a)

fashion.

universally

temperatures

to

alpha

increase

is

behave

thermometers,

for

should

conform

with

accelerated

almost

fully

t

Most

A

and

as

application.

element

curve

at

purchased

wire.

thermometer

and

be

performance

specific

transduction

Platinum

in

may

with

the

temperature

(5)

200

ms

be

thermocouples

bare

carefully

avoid

Resis£ance

free

(4)

should

sheath

Thermometers

tailored

(3)

the temperaof uncertainty.

from

50

differ-

4-3).

developed

(2)

to

connections

accurately

R_tance

of gage

vicinity

avoided,

reference

be

3.1.3.2

the

or

be

(Reference

(9)

constant

uncertainty

beregarded a third metal.

thermocouple Closed

small

may of

measurements this region

the

of

materials

avoided.

cannot be

of

from

Connections must

region of

wire] This wire composed

requirements.

constructed

a

consists

to make accurate be uniform over

response

with

always

which

two

insulating

element is

of thin

a

commercially grid pieces

material.

of

temperature of

3.1.3.3 should

.@

Transducer be

temperature general, the

listed

considered

Mouq_ing during

transducers. probes, items (I)

and

Configuration.

the They

surface

pertain

are

design

divided

into

measurements.

to

either

following and

three

Unless

items

installation

otherwise

thermocouples

of

categories

or

-

specified

resistance

thermometers.

General

(a)

Measured

fluids

sensing surface

(b)

material

used

exposure

(exposed,

immersion

identification

the

transducer

the

sensing

mounting

should markings

should

nomenclature,

or

information

number,

manufacturer's

of

external one

essential, at

a

as

to

a

nameplate

of

information temperature,

exposed-element. part

name,

and

identifica-

connections,

and

characteristic

nominal

should

be

be

furnished

throwaway

substrate

a

stated.

range

deemed or

resistance

temperature.

Consideration parts

as

for

includes

electrical

operating

such

stated

for

such

or

nameplate

least

and

transducer,

platinum-wire,

serial tion

element

be

include

e.g.,

on

coated) method

also

Other

at

limitations

stem materials, and should be defined.

enclosed,

or

transducer

resistance,

(e)

in

probe

The

as

, _ ,.-._

0) c,

,,-I :_ 0.,-4

cQ ._

c_ 0 .,.4

.._ O,

O

L._

_._ g., o.

Q;

o cO cQ Q;

L._

,q _u

._

._

c_ -,.-4

:_

.,._

_

._..._ _)

O

Q; e.

E

r,.,

O Q) c, ._m

.g: O.

.g:

L, _0 g_

O

O O

L

r_ _

0 J,.)_..) c_

0,, 0 Q) _

O

0._

c_ 0

CO _)

cO

_0 c_ oE-I

.r-I L

0 0

oJ

¢q

OJ

J -,-t

OJ

O4

c.

°_

.,=4

.,..(

-,-I

_0 0 ,.g:

q_ .0

.O

.O ,--I

0 _0 L

L

::I c. ..g: E-0 c_ .o

O_ 2

O_

C_J E

Z

Z

E

oJ

04

O_

E

._-( Z

Z

=,.

Z

Z

I-.I CO 0 0)

0 Q

"T

_O 0)

cO .,.-4

L

L,

O, n=

O'

.g: O

O L,

,=

_0 g) L, .O

c_ Q; Q) ,.-.4

X

"1

_0 _o Q) c_

.O

_.,

L, Q;

O p.

c_

0 Z

a_

O .O

E

CO JO r-,

O

O

cO

6-28

O O,

r_

Q) _

Q) O C (0 _J _o

cO

¢J

q) _-_ bO ._J c.

_

_ O O. E _

O

_ •

_-_ _

_ _

E

O

.,'_

.._ O r,.

O O

;3 .,-.I CO O9 L, L.

.,-I C .,.-4

_0 (0

:3

c0

.._

_) ._-_

c_ O

E_

"_ '_

0) c.

0 .,'_ ._ _

O •,-_

L _ c0

.,.._ _,.

_. r_ r'_ O

'O

L.

_) O

.._ ._.J

_

_0 I:_ _0 r_ _-,_

O

0) O

O

_.,

(1) (1) L O

0J L

c-_ c0 ," _ L

0

_1 .0

(1)

0

0

_

_

0

c'

_,,_

_._

_)

_-

,_

,...-I ._ i., r_

O _-

_) c'.

O .,-.I aJ cO

O cO

0 .,-4 aJ

c0 O •,-I

,--I _)

O

.C c0 c.

_

03

E

•

_0

q) O

o_-_

"10

E L.

N N 0 c.

L,

b0 c_ .,...i c. O C) v

.,-t _) c--

OJ

b0c0 r, ._.j F,.:2 .,.-_ O O c--,--I []

.O ,--I

cO .,-.I

cq

r_ .,-I

od .,..4

_O

.O

b0 c.

Q) co c_ [-., C0 c.

Od E

E Z

Q. O

Od E

oj E

-,.4 Z

Z

H CO

O c.. O

!

C O

L

,.O

0 f_

o9

S.,

0 cO cO

c_ -,.4

cO

I0 r_

_-, 0 _,._

O

.O

L 0

,O 6.4

O -,-3

.0 0 L.,

m .C

,.0 E

,-_

c0 _-)

c,

E_

0

J-) rO

O G..)

CD

O ..Q

c0

0 0 .C cO

0 ;0

W

0

O. _) L

0

0

0

cO

0._

L..) H

6-29

..c: ,-'4 _ CU t_ c_ c_ _ ,_..., r-,

-el c_ _._

,.4

_

_.-

_

,--_

0

•,_

_'_

_ r_ 0

e-. 0

E

•

C 0

C -,-4 C 0 C_

IlJ e_0_ r.1

r-

0 0 C

.rq

0

L_3

_O

cO ,-.4

0 c_ 0 0

.,_ E 0 ! E --_

L ,...-4

C 0

_ "0

[] co

m 0

0

0

_0

•,_

-_

_ E

-_

_

0 -_

_

_-_

6-30

._

.,.4

,-I

b0_,J

O c-

O

,-_

_J

O

c_

8 O

_ L .,_

,d O .,_

c-, _

°M

o_

_

cO ..t=00 O

b0 c. L _J O (.J

tb0

_0 O O r_ °_ []

r,1 .,.4

b0

c0 L,

CO c,...4 H CO O o .,"4

O

7 _O

O ,-I

" o

b0 -_

_

c_

•_ _._

.,._ _._

o

_0

_

O

O, .,-I O

,O O ,-_

.,._

_

1

A 0

O V O

L aJ

L

CO

6-31

0

,._ o .C

i.z

L

C_

r_ E _; .o

c_

v-0

E ,--I 0 _ _tm _-_ E _0 0

_0 bO

r,

_D .,.4

0

0

c_

0

0

0 ,-4 t_

E-,

t_ F_

v

_9

t_ O r.Q 0

0 IO

(0 cO O. i0

O cO

0 0 O. cO 0

r-, 0 .F-I

,-4

0 -,.4 0 _O 0

e_ .,-.I L O

0

,--4 r-I t_

.o bO

I _JO

:_.0 _ E 0 0 0

bO C 0

C

0

0

•,.4

.o

,_ B

O; B "0

0

I1) r_ B

,-4

•

t_

•

.o

,--I O 0

0 ;..

0 r_ E _J

0

0 >

:>

I:10 0 r_

i0 0

0

0

_

_'_

_

_ 0

0 0 ._-_

E

]

E I.

_,-., _t

0 .o

)

0 r_

_ 0 "_1 .._

._1 rio

oO

tO

0 LD

t..,

OO

e!

_D

t-.

_

OO 0

.,..4 c_ .,-I

0 ._

,--t

0 :_ ._.

C O .,...I

0

>

_, 0

_

0

;:h ,_

0 t) E-,

_o O9

6-32

0

0 CO

cO

I

0 qO c" 0 e" .o ,..-t •_.1 •_.-_

0

_

0

_

_

r...

_

_ 0 ,_

!=1. 0 (I1

._

0

_1 ,-¢ tO -r-4 L

0

CO c.

.4--_ r_

°

Q) O-O E

;_

> (2

O O. 1,_

e-

r_ (2

tlO

o

_) E r-._

O

II

I_

O 0...

c_ 0 °_ b0 c_ -fH L c. 0

c_

[J2

-_ r"

O O r_ S

o

_

°

._

_

_-_

e_o

O)

0

_

r"

E

c-, _ .,-I

_ 0 c-

0 c, ._

a_ O

cO .r-q

r_

L Q) ¢0 r-. E-,

¢0 -r-I

r_ H O0 O_ O r_ O

0

O r" O

4_ E .0..)

r_ L

r_ E

0 E E

0 -,-I

¢) ,-4 .O

O im

c-

c, 0

-,-I

0

0 O) O.

0

e., O 0 _., ..C

t

0 0

>

_., _,_

O r_ E X o0

6-33

_._

_1

_

>

0

_

._

0

o_...I I. a.a C L

C ,,4 c, ,,-,I ,-I

m

O 0

O ,,,-4 O -.4 c.,_

en I

I

I H >

O .,.-I

I. H

+

,Z

gJ .,-I

.,4

c,

c-

C

o_

C_ c_

.r-l.

_" ,_._

O

.,-I 'IO

O

O _

II O

C O &4

C

,O CD

c.c,l I_ -,-,I "El

_0 O

r-

t.

In -,-I ,-4

E r.,u E-4

"7 i= _D ,-4 I--I 0'3 0 I. c_ 0 C O

,,--I 0 .,-I .o L.

. ° v-. I ',,E,

O .,-I

,-I

.-I

_ 0 .,-I

0

ctl C_

_.,-I

c_ O .,.._

O i.

c. 0 .,-I

I. 0 (D

0

C O .,_

0 O

O .,-I

,-.4

,-I

I::

O bO

(tl

C .,4

O I-,

_a

0 0 I. >

-,-4

0 _0 C

.,-I

O ,,,.-t

0

6., I0,-4

O

,-.-I 0 ,,o

c/) -,..I O m.

[-i m,-g-

¢D

6-3_

¢D

,I

oL_.

3

,i._

e'_'

_k

7.0

REFERENCES

6--I.

Gardenshire, April 1964.

6-2.

Conte, S. D., and de Boor, C., Elementary McGraw-Hill Book Company, New York, 1972.

6--3.

Ha_ing, R. W., Numerical McGraw-Hill Book Company,

6--4.

Mechtly, E. A., The International System of Units, _d Conversion Factors, NASA SP-7012, 1969.

6--5.

Green, L., pP. 34-35,

6--6.

Page, _,

6-7.

Roscheke, Nozzle,"

6--8.

Garrett, J. W., Simmons, M., and Gobbell, W. C., Exit Noszle Flow Separation as Influenced by Nozzle Geometry. Fu_l-Oxid_zer Ratio. and Pressure Level, AEDC-TR-67-122, Arnold Engineering Development Center, Tennessee, July 1967.

6--9.

Rothe, D. E., Experimental _tudy of Viscous Low-Density Nozzle Flows, CAL Report AI-2590-A-2, Cornell Aeronautical Laboratory, June 1970.

L.

W.,

"Selecting

Sample

Rates,"

ISA

Journal,

Numerical

pp.

59-64,

Analysis,

J

W

R.

"Flow 1953.

Separation

H., "Flow Vol. 29,

Methods 1973.

for

Scientists

in Rocket

Nozzles,"

and

E. J., and ARS Journal,

Massier, P. F., pp. 1612-1613,

Physical

ARS

Separation in Nozzles," Journal pp. 110-111, January 1962.

Engineers,

Constants

4ournal,

of

"Flow Separation October 1962.

the

Vol.

23,

Aerospace

in a Contour

6-10.

Rae, W. J., Final Report on a Study of Low-Density Nozzle Flows With ADDliC_tion to Microthrust Rockets, CAL Report AI-2590-A-1, Cornell Aeronautical Laboratory, December 1969.

6-11.

Back, L. H., Massier, P. F., and Cuffel, R. F., "Flow and Heat Transfer'Measurements in Subsonic Air Flow Through a Contraction Section," Int. Journal of Heat and Mass'Transfer, Vol. 12, pp. 1-13, 1969.

6-12.

Back, L. H., Cuffel, R. F., and Massier, P. F., "Influence of Contraction Section Shape and Inlet Flow Direction on 'Supersonic Nozzle Flow Performance," Journal of Spacecraf$ _nd Rockets, Vol. No. 6, pp. 420-427, June 1972.

6-13.

JANNAF

Rocket

Dretation 6-14.

Engine

Manual,

Performance

CPIA

Publication

Test

Data

245,

Acquisition

April

and

9,

Inter-

1975.

Arblt, H. A., and Clapp, S. D., Fluorine-Hydrogen Performance, Phase I. Part I: Analysis. Design. and pem_ns_a_on of High Performance In lectors for the Licuid Fluorine - Gaseous _¥drogen Propellant Combination, NASA CR-54978, Rocketdyne Research Department, pp. 135-137, July 1966.

6-35

6-i5. Price,

T_ W., and Evans, D. D.,

Hydrazine Pasadena, 6-i6.

Technology, California,

Glossary, Monopropellant Monopropellant Working Agency, March 1976.

The Status of M6nopropeiiant JPL TR 32-1227, Jet Propulsion LabOratory, February 1968. Hydrazine Engine Technology, JANNAF Group, Chemical Propulsion Information

6-17.

Beltran, M. R._ CPIA Publication

and Kosvic, T. C., Rocket No. 131, January 1967.

6-18.

American Standard Letter Symbols Yi0.14-1959i American Society of

6-36

for Rocket Mechanical

Propulsion

Propulsion, Engineers,

Nomenciathre,

PUblication 1960.

APPENDIX THEORETICAL

PERFORMANCE

VI-A

OF

MONOPROPELLANT

HYDRAZINE

W

This calculations impulse and dissociation VI-A-2. as

a

The

appendix

for

Characteristic

ratio

of

of

of

expansion

product

gases

are

from

results

point

are

the

in

and

of

thrust

the

these

assumin_

assumed

VI-A-3.

Figure

molecular

VI-A-4.

Reference

ammonia

temperature

in and

Figure

by

in

was of

reaction

presented

generation

given

performance specific

functions of percent ammonia in Figures VI-A-I and

conditions

extended

gases

impulse

figures a

VI-A-I.

frozen

during

at

the

coefficient

were

constant

gamma

The

chemical

chamber

conditions

expansion

were

was

calculated

assuming

loss. stagnation

most

pressure here.

pressure

by

in

thermochemical Theoretical

adiabatic

shown

and

product

presented

the

at

from

hydrazine.

chamber

condensation

Specific

results

utilized

last

the

divergence

varying

used VI-A-I

the

of

A all

values

potential

ignored.

and

at

Reference

composition any

of

dissociation

heats

the

from

results

velocity

ammonia

specific

The taken

zero

presents

decomposition

thrust coefficient are shown as and nozzle expansion area ratio

function

weight

and

the

is

quite

stagnatlon

1030

effect

small

monopropellant

various

of

The

kN/m

on

over

the

hydrazlne pressures

2

the

(150

range

of

thrusters; are

psi)

calculated

was

operating however,

presented

used

values

in

for of

conditions tabular

Reference

VI-A-I.

REFERENCE VI-A-I.

Lee,

D.

H.,

Performance

Calculations

HYdrazine

and

Monopropellant

Mixtures,

JPL

TR

California,

32-348,

December

3,

Hydrazine Jet 1962.

t

6A-I

Propulsion

fo_

MonoDroDellant

- Hydrazine Laboratory,

Nitrate Pasadena,

i p

2600

270

I =

l(_30kN./m

2 (1501bf/in.

2)

c

_= 200 260 I00 250O

--

250

"--4

J.

24017

20

--

240

N _-

n_

10

-

--2_ t.)

-- 230

0

2200

--

"I" (-.

-- 220

2100

--

-- 210

2000

--

-- 200

I 20

I 40

I 60

I 80

I00

% rqH 3 DISSOCIATED

Figure VI-A-I.

Theoretical

Specific

6A-2

Impulse

for Monopropellant

Hydrazine

1.95

I

I

P

I

=

1030 kN/m

I

2 (150 Ibf/In.2)

20O P

1.9

oo\ 1.8.5

50

8 u_

z u 1.8--

8 -r .J

o

1.75

I

1.7--

1.65--

1

l

l

[

2O

40

60

80

100

% NH 3 DISSOCIATED

Figure

VI-A-2

Theoretical

Thrust

Coefficient

gr

6A-3

for MonoDropellant

Hydrazine

j

,

,

J

"

j

...........

jsooo

1400 Pc =

5 ¸

!039 kN/m

2 (150 !bf/in.

45OO

2)

D

44O0

1350

9 u

4300 1300 4200