Reentry of Space Vehicle

Re-entry of Space Vehicle

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1. INTRODUCTION The successful

exploration of space requires a system that

will

reliably transport payload such as personnel and instrumental etc. into space and return them back to earth without subjecting them an uncomfortable or hazardous environment. In other words, have to

the spacecraft and its payloads

be recovered safely into the earth. We have seen the re-entry

capsules and winged space vehicles approach the earth followed by safe landing. However, this could be accomplished only after considerable research in high speed aerodynamics and after many parametric studies to select the optimum design concept. Re-entry systems were among the first technologies developed in 1960s for military photo-reconnaissance, life science and manned space flights. By 1970s, it led to the development of new refurbish able space shuttles. Today space technology has developed to space planes which intend to go and come back regularly from earth to space stations. USA’s HERMS and Japan’s HOPE is designed to land at conventional airports. Few significant advances in current proposed re-entry capsules are ballistic designs to reduce development and refurbishable cost, to simplify operations. For entering into atmospheric and non-atmospheric planet

the

problem involves is reducing the spacecraft’s speed . For an atmospheric planet

the

problem involves essentially deceleration, aerodynamic heating,

control of time & location of landing. For non-atmospheric planets, the problem involves only deceleration and control of time & location of landing. The vehicle selected to accomplish a re-entry mission incorporates a thick wing , subsonic ( Mach < 1 ) Dept. of Mechanical Engineering

airfoil

modified

to meet hypersonic MESCE Kuttippuram

Re-entry of Space Vehicle

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(Mach>> 1 ) thermodynamic requirements. The flight mechanics of this vehicle are unique in that rolling manoeuvres are employed during descent such that dynamic loading and aerodynamic heating are held to a minimum. Therefore re-entry technology requires studies in the following areas: 1. Deceleration 2. Aerodynamic heating & air loads 3. Vehicle stability 4. Thermal Protection Systems (TPS) 5. Guidance and Landing.

Dept. of Mechanical Engineering

MESCE Kuttippuram

Re-entry of Space Vehicle

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2. RE-ENTRY MISSION PROFILE, CONSTRIANTS AND VEHICLE REQUIREMENTS The safe recovery of the spacecraft and its payloads is made possible by the re-entry mission. According to the different constraints the mission profile can be divided into three distinct flight segments:1. Deorbit and Descent to sensible atmosphere at an altitude of nearly

120kms. 2. Re-entry and hypersonic glide fight. 3. Transition flight phase, final approach and landing. The unguided first flight segment (Keplarian trajectory) initiated by a rocket deboost maneuver at a

specific orbital point determines the flight

condition at re-entry. The second flight segment covers the atmospheric glide at an altitude of 120 km to 30 km during which the re-entry vehicle’s high initial kinetic energy is dissipated by atmospheric breaking. The third flight segment does the final approach and landing. All these phases are shown in Fig.1. The various forces acting on the re-entry vehicle are:1. Gravitational force acting towards the centre of the planet. 2. Gas dynamic force opposite to the direction of motion of the vehicle. 3. Centrifugal and gas dynamic lift force acting normal to the direction of 4. motion of the vehicle. Along the re-entry flight several mission

constraints

much be

imposed arising from the structural limit, crew comfort and control limits.

Dept. of Mechanical Engineering

MESCE Kuttippuram

Re-entry of Space Vehicle

These

limits

4

require the flight

state

of

the vehicle

to the

constrained such that the:1. Load factor

n