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7/27/2019 Resv Final Report
1/23
1RE ENTRY OF SPACE VEHICLE
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, the spacecraft and its payloads
have to 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 manyparametric 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. USAs HERMS and Japans
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 spacecrafts speed . For an atmospheric
planet the problem involves essentially deceleration, aerodynamic heating,
control of time & location of landing. For non-atmospheric planets, theproblem 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 ) airfoil modified to meet hypersonic
DEPARTMENT OF MECHANICAL ENGINEERING
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2RE ENTRY OF SPACE VEHICLE
(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.
DEPARTMENT OF MECHANICAL ENGINEERING
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3RE ENTRY OF SPACE VEHICLE
CONTENTS
1. ABSTRACT
.2. INTRODUCTION
3. RE ENTRY MISSION PROFILE, CONSTRAINTS, AND VEHICLEREQUIREMENTS
4. ENTRY CORRIDOR
5. GAS DYNAMICS AND DECELERATION
6. AERODYNAMICS HEATING
7. MATERIAL SELECTION IN DESIGN
8. THERMAL PROTECTION SYSTEM (TPS)
9. VEHICLE GUIDANCE AND LANDING
10. CONCLUSION
11. REFERENCE
DEPARTMENT OF MECHANICAL ENGINEERING
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4RE ENTRY OF SPACE VEHICLE
1. ABSTRACT
In recent years, industry has produced high-temperature fiber and whiskers. The author examined
the atmospheric reentry of the USAs Space Shuttles and proposed the use of high temperature
tolerant parachute for atmospheric air braking. Though it is not large, a light parachute decreases
Shuttle speed from 8 km/s to 1 km/s and Shuttle heat flow by 3-4 times. The parachute surface is
opened with backside so that it can emit the heat radiation efficiently to Earth-atmosphere. The
temperature of parachute is about 1000-1300o C. The carbon fiber is able to keep its
functionality up to a temperature of 1500-2000o C. There is no conceivable problem to
manufacture the parachute from carbon fiber. The proposed new method of braking may be
applied to the old Space Shuttles as well as to newer spacecraft designs.
Re-entry capsules promises to intensify international competition in launch services,
microgravity research and space technology development. These systems will also confer an
important strategic advantage in the conduct of materials and in life science research.
The objective of this paper is to provide a modest degree of understanding of the complex inter-
relation which exist between performance requirements mission constraints , vehicle design and
trajectory selection of typical re-entry mission. A brief presentation of the flight regimes, the
structural loading and heating environment experienced by booth no lifting and lifting re-entry
vehicle is given.
DEPARTMENT OF MECHANICAL ENGINEERING
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5RE ENTRY OF SPACE VEHICLE
2. RE ENTRY MISSION PROFILE, CONSTRAINTS 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 reboots 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 vehicles 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
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.
DEPARTMENT OF MECHANICAL ENGINEERING
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6RE ENTRY OF SPACE VEHICLE
These limits require the flight State of the vehicle to the
constrained such that the:-
1. Load factor n
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7RE ENTRY OF SPACE VEHICLE
Cd= drag coefficient
Depending on the specified mission requirements the second or third property is chosen as
design drivers.
2.Parts of a space vehicle
3.ENTRY CORRIDOR
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8RE ENTRY OF SPACE VEHICLE
An entry corridor is a range of entry conditions within which an entry
is possible. The undershoot boundary and overshoot boundary forms the upper and the lower
limits of the entry corridor. Terrestrial flights are tolerant of guidance error accompanying a
landing approach. An undershoot may cause destruction of vehicle during entry and an
overshoot may result in a homeless exit to space.
Figure shows the explanation of entry corridor and possible path for vehicle with lift to Venus,
Mars, and Titan.
If the guidance error results in an excessive undershoot as shown by the two dashed
trajectories, the vehicle will enter the atmosphere at an excessively steep angle, thereby
experiencing too much deceleration. If the guidance error results in an excessive overshoot as
shown by the two outer dashed trajectories, the vehicle will not slow down considerably in order
to complete entry in a single pass. Hence the shaded portions representing excessively overshoot
and undershoot are excluded as not representing the intended entry maneuver.
Although overshoot at hyperbolic velocity > (2gRo)1/2 may result in a homeless exit to
space, overshoot at the outer corridor at parabolic speed = (2gRo)1/2or at an elliptical speed