lecture-17 ppt for Cubesat

Micropropulsion for Nanosatellites

Olivia Oli via Bil Billet lettt - AA 236 236A A 2006

Mission Statement Why do we need thrusters for CubeSats?  Attitude

Control  Camera Pointing  Formation Flying  Rendezvous  Vehicle Inspection  Orbit Changes  De-Orbit Capability  Research and Development  Because they’re cool

CubeSat Constraints What’s so hard about adding thrusters? 

Size: < 10 x 10 x 10 cm



Weight: < 1 kg



Power: < 1 Watt



Minimum Ibit ~ 10-4 Ns

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Flight ready ?



Affordable ?

Previous Missions What kinds of micropropulsion are currently in use? In student satellites: Not much. As of 2006: •

1 CubeSat (UIUC ION), pending launch

•

Few nanosats (UW, MTU, U Toronto) but no launches scheduled

In industry satellites: Increasing interest from DARPA, AFRL •

SSTL, Northrop Grumman, JPL

(Viable) Types of Micropropulsion 

Electric Propulsion    



Pulsed Plasma Thruster (PPT) Vacuum Arc Thruster (VAT) Micro Resistojet Colloid Microthrusters

Chemical Propulsion    

Monopropellant MEMs Bipropellant MEMs Solid Propellant MEMs Cold gas thrusters (micro & MEMs)

. . . more?

Evaluation Criteria 

Primary Propulsion vs Attitude Control? 



Thrust < 1 N

vs Ibit ~ 0.1 mNs

CubeSat constraints:    

1 kg, including all fuel 1 W (average power) 10 x 10 x 10 cm cheap!

(Viable) Types of Micropropulsion 

Electric Propulsion    



Pulsed Plasma Thruster (PPT) Vacuum Arc Thruster (VAT) Micro Resistojet Colloid Microthrusters

Chemical Propulsion    

Monopropellant MEMs Bipropellant MEMs Solid Propellant MEMs Cold gas thrusters (micro & MEMs)

the PPT man

Andy Sadhwani 2006 Thrusters Team Leader

Pulsed Plasma Microthruster 0.03 A

5V

Voltage Stepper 1500 V

1000 A for 10 ns

Teflon Coax

Capacitor

Specs

Pros

Cons

Thrust:

High

Low

0.006 mN Rotate 90º: 12 min (4,500 pulses) Lifetime: Forty 90° rotations (200,000 pulses ) Input: 5 V at 30 mA  Output: 1500 V at 1000 A for 10 ns at 6 pps

ISP Small Low Power

Thrust EM Interference Much R&D Left

Vacuum Arc Thrusters (VAT)  Different

cathodes vary impulse  Variable pulsing (width & freq)  Lighter PPU than PPT  MVAT – increased thrust?  High EMI  Not tested  Hard to fit 3 in CubeSat Alameda AlamedaApplied AppliedSciences Sciences ••Power Power==44W W ••Mass Mass==150 150gg ••Thrust Thrust==54 54uN uN(90 (90°°inin10 10min) min) ••IIbit = 1 uNs bit = 1 uNs ••Size Size==44xx44xx44cm cm

MTU HuskySat micro-Vacuum Arc Thruster

Micro Resistojet  Simple

system  Fuel: water, nitrous oxide  Larger versions used for years    

Low impulse Test failed – propellant leak? Research discontinued (water) Weight of propellant SSTL SSTL[Water] [Water] ••Power Power==33W W ••Dry DryMass Mass==13 13gg ••Thrust Thrust==3.3 3.3mN mN ••Size Size==10 10cm cmlong long

UK-DMC Micro-Resistojet, 2003

MEMs Resistojet  Entire

system on silicon chip  Easy to fit 3 axis system  Research at: Aerospace Corp, Tshingua U, Indian Institute of Technology 

Still in research stage  Thrust not well characterized IIT IIT ••Power Power==11––2.4 2.4W W ••Thrust Thrust==55--120 120uN uN ••Size Size==2.5 2.5xx2.5 2.5mm mm

Colloid Microthrusters  High

current  droplets and ions, high ISP  Low current  droplets only, low ISP  Tiny arrays of multiple needles with micromachining   

Need external neutralizer Operating voltage ~ 15 kV  Far from flight-ready – still in research stage, unreliable

Busek  Busek  ••Power Power==22W W ••Mass Mass==80 80gg ••Thrust Thrust==11mN mN

(Viable) Types of Micropropulsion 

Electric Propulsion    



Pulsed Plasma Thruster (PPT) Vacuum Arc Thruster (VAT) Micro Resistojet Colloid Microthrusters

Chemical Propulsion    

Monopropellant MEMs Bipropellant MEMs Solid Propellant MEMs Cold gas thrusters (micro & MEMs)

Monopropellant MEMs  High

propellant density  Low power, high Isp  Wide range of impulse and thrust levels  Hyrazine (high Isp) and hydrogen peroxide (noncorrosive, easy handling)  Essentially size of 1U  High Ibit

Picture courtesy of Nasda.go.jp

Micro MicroAerospace AerospaceSolutions Solutions ••Wet Wetmass mass==175 175gg ••IIbit = .17 mNs bit = .17 mNs ••Thrust Thrust==50 50mN mN ••Size Size== 22””diameter diametertank  tank  ••44thrusters thrusters ••Lifetime Lifetime==50,000 50,000firings firings ••Flight-ready Flight-ready

Picture courtesy of Micro Aerospace Solutions website

Bipropellant MEMs  Very

high thrust-to-weight ratio  High propellant densities  Low power  Research at Stanford (Mech Eng)  Ibit too  

high for attitude control. Good for primary propulsion only Still in research stage More complex system, harder to fabricate

Solid Propellant MEMs  High

propellant densities  Low power  No moving parts, feed systems, pumps, leakage  Tiny arrays of multiple nozzles allow for range of thrust  One-time-only firing  Too expensive!

Picture courtesy of Northrop Grumman

Picture courtesy of LAAS, France

Cold Gas Thrusters  Reliable,

simple systems with long flight history  Benign propellants  Continuous & pulsed operations  High Ibit  Propellant volume  Very low power  COTS valves available  Leakage Marotta Marotta ••Dry Drymass mass==50 50gg ••IIbit = 44 mNs bit = 44 mNs ••Thrust Thrust==445 445mN mN ••Power Power==0.4 0.4W W ••Flight-ready Flight-ready

Flight history on microsatellites: NASA ST missions

Picture courtesy of Marotta

Cold Gas MEMs

–

VACCO MiPS

 Chemically

etched valves and system  Fits all constraints  Butane propellant – easy handling  Designed for CubeSats  Expandable propellant tank 

Picture courtesy of VACCO Industries



Not ready/ not for sale?

VACCO VACCO ••Wet Wetmass mass==456 456gg ••IIbit = .55 mNs bit = .55 mNs ••Thrust Thrust==55 55mN mN ••Size Size== 2.5 2.5xx 10 10 xx10 10cm cm ••55thrusters thrusters 3-axis 3-axiscontrol control ••Designed Designedfor forCubeSats CubeSats

VACCO Piezoelectric Thrusters 2 identical 1” valves controlling flow of iso-butane Low power • To open valve: 200 mW for 20 ms • No power required to keep valve open

10 mN thrust • 220 ms pulse  1.5 deg/s rotation rate • 90 degree turn in 60 seconds

Liquid valve

120 psi Fuel storage tank

10-15 psi Plenum

Thruster valve

Isobutane Self-pressurization PV=nRT

P

T

Problem…

Only 2 thrusters donated by VACCO/JPL . . . can spin up but can never spin down

Solution: 2-Thruster Design • Centrifugal effect separates different phases of butane • Allows complete single-axis control

Liquid Perforated baffle plate

Gas Inlet tube

Tank Location in 2U Assembly Moment of Inertia

Single Axis Rotation

Temperature Protection

Tank Sizing and Characteristics Volume (cm3)

Maneuvers

62.79

7690

31.40

3845

20.93

2563

Full Volume = 62.7cm3 Pressure ~ 44 psi @20oC

(Viable) Types of Micropropulsion 

Electric Propulsion 

Pulsed Plasma Thruster (PPT) Arc Thruster (VAT)  Vacuum Propulsion  Chemical  Micro Cold Resistojet gas thrusters (micro & MEMs)  Colloid Microthrusters 

Chemical Propulsion 

Monopropellant MEMs  Bipropellant MEMs  Solid Propellant MEMs  Cold gas thrusters (micro & MEMs)

Questions?