REUSABLE LAUNCH VEHICLE

SEMINAR REPORT

Submitted by

SREERAM SADANANDAN

TJE17ME093

in partial fulfilment for the award of the degree

of

BACHELOR OF TECHNOLOGY

in

MECHANICAL ENGINEERING

THEJUS ENGINEERING COLLEGE

APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY

DECEMBER 2020
 THEJUS ENGINEERING COLLEGE
VELLARAKKAD, THRISSUR- 680584

DEPARTMENT OF MECHANICAL ENGINEERING

BONAFIDE CERTIFICATE
Certified that this seminar titled “REUSABLE LAUNCH VEHICLE”, is the bonafide work
of S R E E R A M S A D A N A N D A N ( T J E 1 7 M E 0 9 3 ) of 2017 – 2021 year in partial
fulfilment of the requirement for the award of bachelor of technology degree in
MECHANICAL ENGINEERING awarded by APJ Abdul Kalam Technological University
during the year 2020 under my guidance.

Guide: Head of the Department:

Mr. Arunnath P.R Dr. K. R. Jayadevan

Assistant Professor Head of the Department
Dept. of Mechanical Engineering Dept. of Mechanical Engineering
Thejus Engineering College Thejus Engineering College

Place: Vellarakkad
Date: 28-12-2020
 ACKNOWLEDGEMENT

I express my heartfelt gratitude to our Principal, Dr. K. Vijaya Kumar, for giving me
this opportunity to present this seminar and for the facilities offered to me throughout this
endeavour. I would like to express my sincere thanks to Dr. K. R. Jayadevan, Head of the
Department, Mechanical Engineering & Dr. V. Baskaran, Professor, Department of
Mechanical Engineering, for his support and guidance.

I am very much grateful to my seminar guide, Mr. Arunnath P.R, Assistant

Professor. Department of Mechanical Engineering, who guided and supported me for the
successful completion of this seminar. I would like to express deep sense of gratitude to my
seminar coordinators, Mr. Shreekiran and Mr. Jerin John Kutty.

I am deeply grateful to all those who helped me directly or indirectly during the
course of this work.

Finally, but above all I thank God Almighty for the divine blessing bestowed on me
for the completion of this seminar successfully.

iii
 ABSTRACT

Conserve, Reuse, Reproduce these are the words using which the present day society
is trying to make an impact in reducing the excessive usage of the depleting resources and
decreasing time as well as in bringing down the cost and in increasing the efficiency of the
products. One of the technology’s biggest inventions rather innovation at work is the
development of The Reusable Launch Vehicle, in short known as the RLV. Reusability is the
main criteria behind this vehicle. The vehicle will return back to earth after its task is
completed, and is used for further missions. This invention mainly reduces the cost, time and
the specified targets can be achieved with the use of fewer resources. The idea of RLV made
its foundation in the minds of the scientists in the 1950’s but bringing that idea into a real
launch vehicle took many years as this idea was beyond the hands of the technology of that
time. As the technology developed the path for the successful making of this launch vehicle
was getting cleared. There were many factors that were to be considered like the low weight
structure, heat shield, the propellants needed to be used, the engines etc. but the main aim was
to bring out the concept behind its working and building a proper design which are discussed
in this paper. With the ever-growing technology RLV’s with improved mechanisms like
SSTO, TSTO were developed which are also mentioned below. In near future these RLV’s
would completely bridge the gap between the earth and the sky.

iv
 TABLE OF CONTENTS

CHAPTER NO TITLE PAGE NO

ACKNOWLEDGEMENT iii

ABSTRACT iv
TABLE OF CONTENTS v
LIST OF FIGURES vi

LIST OF ABBREVATIONS vii

1 INTRODUCTION 1
2 LITERATURE SURVEY 3
3 THE KEY TECHNOLOGICAL ASPECTS THAT

ARE TO BE FOCUSED 6
4 WHAT IS REUSABLE LAUNCH VEHICLE 7

4.1 OBJECTIVES 7
4.2 HOW TRADITIONAL ROCKETS ARE USED 7

4.3 HISTORY 9
4.4 DIFFERENT REUSABLE CONCEPT 9
4.4.1 Single-Stage-To-Orbit (SSTO) 9
4.4.2 Two-Stage-To-Orbit (TSTO) 11
4.4.3 One And A Half Stage To Orbit (OHSTO) 12

5 DESIGN OF RLV 13
5.1 THERMAL PROTECTION SYSTEM 15

6 WORKING 16
6.1 FIRST STAGE- SUBSONIC AND SUPERSONIC
STAGE 16
6.2 SECOND STAGE-HYPERSONIC STAGE 16
6.3 THIRD STAGE- SPACE STAGE 17
6.4 FOURTH STAGE – RE-ENTRY STAGE 17

7 LANDING AND TAKE OFF SYSTEMS 18

v
 7.1 BRAKING 18
7.2 HORIZONTAL LANDING 18
7.3 VERTICAL LANDING 19
7.4 HORIZONTAL TAKE OFF 19
7.5 VERTICAL TAKE OFF 19

8 TECHNOLOGIES REQUIRED FOR RECOVERY 20

8.1 RETRO-PROPULSION 20
8.2 MID AIR RECOVERY 21
8.3 RECOVERY OF LAUNCH VEHICLE COMPONENTS 22

9 ADVANTAGES AND ECONOMIC BENEFITS 23

9.1 ADVANTAGES 23
9.2 ECONOMIC BENEFITS 24

10 CONCLUSION 25
REFERENCES 26

vi
 LIST OF FIGURES

FIGURE NO TITLE PAGE NO

4.1 DC-X 9

4.2 X-33 Venture Star 11

4.3 Two Stage To Orbit 12

7.1 Horizontal Landing 18

7.2 Vertical Landing 19

8.1 Landing By Reverse

Thrusting 21

8.2 Mid Air Recovery(MAR) 22

8.3 HIAD 23

vii
 LIST OF ABBREVATIONS

ADR Active Debris Removal

ELV Expendable Launch Vehicle

ERJ Ejector Ramjet

HIAD Hypersonic Inflatable Aerodynamic Decelerometer

IVHM Integrated Vehicle Health Management

LEO Low Earth Orbit

MAR Mid Air Recovery

NASP National Aerospace Plane

RLV Reusable Launch Vehicle

SSTO Single Stage-To-Orbit

TPS Thermal Protection System

TSTO Two-Stage-To-Orbit

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Reusable launch vehicle Seminar Report 2020

CHAPTER 1

INTRODUCTION

A Reusable launch vehicle (RLV) refers to a vehicle which can be used for several
missions. Once when a RLV completes a mission, it returns to the earth and can be used
again whereas the Expendable Launch Vehicles (ELV) can be used only once. This is the
main advantage of a Reusable Launch Vehicle (RLV) and this can be done at very low cost.
Though the thought of Reusable launch vehicles started in 1950’s, because of low technology
development like insufficient thrust-to-weight ratio of engine to escape our gravity etc. made
their thoughts impossible. Later due to the advancement in the technology, the existence of
the Reusable launch vehicle became possible.

Philip bono proposed few concepts for the development of the vehicle like plug
nozzle engines to retain high specific impulse at all altitudes, use of drop tanks to increase
range, use of in-orbit refuelling to increase range, use of spherical tanks and stubby shape to
reduce vehicle structural mass further. Eugen Sanger also proposed few concepts for
advancement of the vehicle like rail boost, use of lifting body designs to reduce vehicle
structural mass, use of in-flight refuelling. In 1960’s space shuttle design process started. The
space shuttle has rocket launch, orbital spacecraft and re-entry space plane. In 1986 an air
breathing scramjet was planned to build by 2000 but due to research project copper canyon
failure it was cancelled in 1993. Few more concepts were proposed in 1990’s. In 21st century
X-33, X-34 was cancelled due to rising cost. Later these space shuttles were found to be
highly expensive and two out of five space-worthy orbiters were destroyed during accidents.
Hence orbital reusable launch system is currently not in use. Several reusability concepts are
single stage, two or more stages to orbit, cross feed, horizontal landing, vertical landing,
horizontal take-off, vertical take-off, air breathing, propellant, propellant costs, launch
assistance, re-entry heat shields, weight penalty, maintenance, manpower and logistics. In this
paper, we will see the aspects that are to be considered while constructing an RLV, different
ways of launching of an RLV, design of an RLV and its working.

Department of Mechanical Engineering 1 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

Over the past several years many concepts have been proposed for the development
of the reusable launch vehicles. When the decision of replacement of shuttle has been taken,
interest and excitement was observed to generate a low cost Reusable Launch Vehicle while
designing an RLV, main aspects that are to be focused are composite, low weight structure, a
well-developed heat shield to protect the system from disintegration while re-entering,
improved propulsion, propellants, increased range, high payload carrying capacity. The
reusable launch system includes reusable cryogenic propellant tanks, composite structures,
thermal protection systems, and improved propulsion and subsystem operability
enhancements.

Department of Mechanical Engineering 2 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

CHAPTER 2

LITERATURE SURVEY

Ragab, Mohamed, and F. McNeil Cheatwood. “Launch vehicle recovery and reuse.”
AIAA Space 2015 Conference and Exposition. 2015: This paper briefly reviews the history
of Reusable Launch Vehicle development and recommended reuse techniques based on the
lessons learned from those efforts. The paper considers a range of techniques for recovery
and reuse of launch vehicles. Launch vehicle component cost and weight by major element
are also discussed as a method of determining cost/benefit of reuse. Of particular interest are
non-propulsive approaches as economic alternatives to propulsive approaches. These may
include aerodynamic decelerators (including inflatable decelerators and parachutes) and
terminal landing approaches including impact attenuators and mid-air recovery techniques.
Utilizing a Hypersonic Inflatable Aerodynamic Decelerator (HIAD) for atmospheric entry
should have considerable mass-fraction advantage over other technologies. Mid-air recovery
(MAR) is presented as an innovative approach for precision landing of impact susceptible
components such as rocket engines while minimizing contamination by avoiding salt water
immersion. The economics of reuse is presented as a basis for recommendations for cost
effective reuse and recovery of booster components.

Alexander Nebylov, Vladimir Nebylov“Reusable Space Plane Challenges And Control

Problems”(2016) : The possible directions of development of space launch technology,
including space launch to suborbital trajectory, in order to reduce the specific cost of launch
at the expense of the majority of reusable carrier components, are analysed. Opportunities of
providing reusability for horizontal and vertical launch are compared. The experience of soft
landing of the first stage of Falcon 9-R rocket of US firm SpaceX is taken into account. The
requirements to the air breathing engine, which could provide an economical horizontal
launch, are considered. The requirements for the engine could be reduced for suborbital
launch, and in this simplified case they could be fulfilled well already at the present stage of
development of aerospace technologies. The proposed principles of reusable HTHL system

Department of Mechanical Engineering 3 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

“WIG-craft +Aerospace Plane” are described and its advantages over the vertical launch
systems are considered.

Henry Adrian William Hyman“Reusable Launch System: The Gateway To The Future
Of Space Travel (2018): In the past, nearly every part of a rocket used to propel shuttles and
satellites into orbit has been designed for one time usage. Generally, after the first stage
rocket (which amounts to 70% of the total cost of a rocket) is used, the rocket falls back to
the Earth’s surface, burning up in the atmosphere and being destroyed. The reusable rocket is
an attempt to resolve this dilemma. SpaceX, the leading company pursuing the technology of
reusable rockets, has successfully developed rockets capable of multiple launches. Being able
to reuse a rocket is a daunting task that requires multiple processes. The following processes
have been used by SpaceX to land its relaunched rockets: stage separation, boost-back burn,
supersonic retropropulsion burn, landing burn, touchdown and recovery. After landing, the
rockets undergo an inspection and then are ready for relaunch. While this is still a relatively
new technology and process, the benefits of reusable rockets are apparent: time, money, and
materials are dramatically conserved. By conserving these valuable resources, reusable
rockets prove to be a sustainable option for space exploration. This sustainable technology
will facilitate greater space access, allowing a deeper understanding of the universe. There is
much to be gained from increased space exploration including the obtainment of materials,
the development of new technologies and possible colonization of other celestial bodies such
as Mars.

Bhavana, Y., N. Mani Shankar, and B. K. Prarthana. “Reusable Launch Vehicles:

Evolution Redefined.”(2013): Conserve, Reuse, Reproduce these are the words using which
the present day society is trying to make an impact in reducing the excessive usage of the
depleting resources and decreasing time as well as in bringing down the cost and in
increasing the efficiency of the products. One of the technology’s biggest inventions rather
innovation at work is the development of The Reusable Launch Vehicle, in short known as
the RLV. Reusability is the main criteria behind this vehicle. The vehicle will return back to
earth after its task is completed, and is used for further missions. This invention mainly
reduces the cost, time and the specified targets can be achieved with the use of fewer

Department of Mechanical Engineering 4 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

resources. The idea of RLV made its foundation in the minds of the scientists in the 1950’s
but bringing that idea into a real launch vehicle took many years as this idea was beyond the
hands of the technology of that time. As the technology developed the path for the successful
making of this launch vehicle was getting cleared. There were many factors that were to be
considered like the low weight structure, heat shield, the propellants needed to be used, the
engines etc. but the main aim was to bring out the concept behind its working and building a
proper design which are discussed in this paper. With the ever-growing technology RLV’s
with improved mechanisms like SSTO, TSTO were developed which are also mentioned
below. In near future these RLV’s would completely bridge the gap between the earth and the
sky.

Zhong, Ya, Danghui Liu, and Chen Wang. “Research progress of key technologies for
typical reusable launcher vehicles.”(2018): In recent years, driven by spaceX and other
commercial companies, the requirement of low cost and fast response to transport, reusable
launch vehicle technology is attracting the world’s attention. Aerospace agencies in various
countries have stepped up research and made some progress in the related technologies of
reusable launch vehicles. The development of reusable launch vehicle has become an
important direction of space development in the future. First, the development status of
reusable vehicles, the Space Shuttle Mode, the Falcon-9 Mode, the Launch Mode on board,
and the Airborne Aircraft Mode, are introduced. Second, the structure design, the propulsion
system, the recycling scheme, the thermal protection system and the launch costs of each
mode is analysed. Third, some related development suggestions are put forward in terms of
the carrier configuration, the design of recycling scheme, the choose of propulsion system
and the thermal protection system for reusable launch vehicle designer.

Department of Mechanical Engineering 5 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

CHAPTER 3

THE KEY TECHNOLOGICAL ASPECTS THAT ARE TO BE FOCUSED

Utilizing wave rider aerodynamics reduces the vehicle weight. The take-off weight
and the thrust required at take-off are reduced by collecting the rocket oxidizer in-flight.
Reusable Thermal Protection System (TPS) is one of the main aspects to be concentrated as it
is one of the most expensive systems of RLV. TPS should be lightweight, durable, operable
and cost effective. Metallic TPS, super alloy honeycomb TPS concept are used to get good
results. The surfaces are tested by low speed and hyper velocity impacts, aerodynamic
heating, acoustic loading. The TPS should be capable of withstanding the heat while re-
entering the earth. Some shields may undergo severe damage hence they cannot be used
again. The use of sharp materials whose tolerance temperature is about 3600°C helps a RLV
to re-enter the atmosphere safely and these materials need not require a constant maintenance.
The ramjet and scramjet propulsion technology is the most significant propulsion technology.
Solar thermal propulsion, hydrogen propulsion are demonstrated by SOTV space experiment.
Some other engines include hydrogen/oxygen rockets, turbojets, turbo rockets and liquid air
cycle engines. These engines fail to reach the goal which resulted in a pre-cooled hybrid air
breathing rocket engines. The propellants of high density compensate for reduced specific
impulse. Hydrogen is an environmentally acceptable aviation fuel. The development of an
RLV aim at the significant reduction of payload transportation costs. The design of large–
payload SSTO vehicle is based on projections of mature National Aerospace Plane (NASP)
technology. The single-stage vehicles which use air-breathing propulsion provide more
economical delivery of payloads to orbit. Several new propulsion concepts are being studied
to increase the payload capacity. When horizontal take-off is considered with first stage
powered by turbojet engines and the second stage propelled by a rocket engine provides 3
times the payload weight to orbit when compared to the vertical take-off mode.

Department of Mechanical Engineering 6 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

CHAPTER 4

WHAT IS A REUSABLE VEHICLE

A Reusable Launch Vehicle (RLV) is the space analog of an aircraft. Ideally it takes
off vertically on the back of an expendable rocket and then glides back down like an aircraft.
During landing phase, an RLV can either land on a runway or perform a splashdown. Small
wings provide maneuverability support during landing. The main advantage of an RLV is it
can be used multiple times, hopefully with low servicing costs. The expendable rocket that is
used for launching the RLV can also be designed to be used multiple times. A successful
RLV would surely cut down mission costs and make space travel more accessible.

4.1 OBJECTIVES

 Development of a launching vehicle which can fly to space at lower cost.

 Reuse the parts of launching vehicle.
 To carry more payload.
 To save resources.

4.2 HOW TRADITIONAL ROCKETS ARE USED

Since the dawn of space travel with the launch of the Soviet satellite, Sputnik 1 in
1954, payloads have only been able to overcome gravity and break away from the Earth’s
atmosphere through the use of multi-stage rockets. “Multistaged” means that a rocket is
separated into sections (usually a primary and secondary stage and the payload), that detach
after using up their fuel. The first stage, for instance, is the largest stage and provides the
initial and largest thrust to get the rocket moving skyward from launch. As P. Timm, in the
article “Stages of a Rocket Launch” explains, once the rocket has reached a specific height,
generally somewhere between 40 and 80 miles above the surface, the first stage runs out of

Department of Mechanical Engineering 7 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

fuel and is jettisoned from the rest of the rocket which continues soaring upward under the
power of the second stage engines. After separation, the first stage falls back down to Earth.
The concept of multistage rockets was separately worked on simultaneously in the early 20th
century by three scientists, American Robert Goddard, German Hermann Oberth, and
Russian Konstantin Tsoilkovski.Engineers designed rockets with multiple stages so that when
the fuel on one stage is depleted, that rocket can detach itself to prevent the rest of the rocket
from having to waste energy carrying unnecessary weight. This process is very efficient as it
greatly conserves fuel, which saves both resources and money. Despite the success and
practicality of using multistage rockets, there is one very critical issue to this practice
regarding what happens to the first stage after it separates. Traditionally, first stage rockets
are designed to either burn up upon entry to the Earth’s atmosphere or plummet into the
ocean at thousands of miles an hour. Either way, the rocket is rendered useless, never to fly
again. This creates a serious problem because, as reported by distinguished international
business magazine, Fortune, “the first stage of any space rocket is far and away the most
expensive piece of the space launch enterprise, containing the bulk of the rocket’s engines”.
On average, of the estimated $100 to $150 million required to build a rocket and launch it,
around $60 million (if not, more) of that price goes to building the first stage as reported by
Loren Grush of the technology news site, The Verge. Having to continually rebuild first
stages accounts for anywhere between 40%-70% of the entire launch process alone.
Additionally, having to rebuild these rockets means a huge cost, time and resources.
According to NASA, a first stage rocket requires hundreds of thousands of pounds of
aluminium and titanium and potentially several years to build. These setbacks illustrate the
non-sustainable economic and environmental issues that traditional rockets have by
constantly needing to be rebuilt. Due to the costs of money, time, and resources, launching
rockets has become a very limited practice leading to repressed space exploration which
proves them to also not be socially beneficial. This is a very unfortunate case because there’s
still so much to learn about and gain from space exploration. However, due to recent
innovations from space travel companies such as SpaceX, rocket travel will become much
more practical. This is thanks to the development of reusable rockets.

Department of Mechanical Engineering 8 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

4.3 HISTORY OF RLV

Throughout the 1990s, several spaceplane designs emerged in the US as smaller

private companies entered the fray. The term ‘spaceplane’ was replaced by the term RLV.
These concepts, however abandoned airbreathing propulsion concepts in favour of ground/air
launched conventional rockets, where all the oxygen needed for propulsion in space is carried
at launch. The reduction in cost of access to space was envisaged by reusing single stage
vehicles or the two stages of conventional rockets, by parachute recovery of each stage.
Among the more prominent RLV concepts in the US were the X-33, the Roton, Astroliner,
Pathfinder, Spacecruiser, Space Access SA-1, Kistler K1, Argus Maglifter and NASA’s SLI-
C1 and C2; and in UK, the Spacecab.

Fig.4.1 DC-X

4.4 DIFFERENT REUSABLE CONCEPT

4.4.1 Single-Stage-To-Orbit (SSTO)

It is a Reusable launch vehicle (RLV) that takes off and lands horizontally like a
conventional plane. It is generally regarded that this method will be more efficient and safer
than the 2-stage model, though that is not to belittle the 2-stage method which would be
aconsiderable improvement on the vertical take-off craft of today. It is also felt that while

Department of Mechanical Engineering 9 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

the 2-stage idea would be easier, the 1-stage would almost certainly be more commercially.
It is a reusable launch viable and would achieve a higher level of success in the objectives of
a space plane. What is required here is further development of jet engines. The only
possibility at the moment is ramjet working together with scramjet (Supersonic Combustion
Ramjet). The major problem is that the scramjets are far from fully developed, offering
many difficult aerodynamic problems. These, however, offer the only current hope of
sustained hypersonic flight. Even with the advance of scramjet development there are still
many problems to be addressed with horizontal take off of space planes. This is because a
Scramjet will only function at hypersonic speeds and a ramjet will only function at
supersonic speeds.

The design will therefore require:

1. A turbojet, once the air intake reaches to mach 1 (supersonic speed) the ramjet
would fire.
2. The ramjet would accelerate the plane to about mach 4 (hypersonic speed) then the
scramjet would fire.
3. The scramjet is expected to be able to reach speeds of mach 15, when finally the
rocket engine would fire.
4. The rocket engine would accelerate the plane to mach 25 (escape velocity) and
would be used in space operations.

While this sounds very good in theory, in practice it is very doubtful whether such
vehicles will have the efficiency to reach orbit, due to the excessive weight and complexity
of such a system. Further to this such a design will not solve the other problem of heat build-
up. What we are really looking for is the development of a combined jet engine that operates
across the range, with maybe a switch to a rocket engine for the last stage and for space
operations. The difficulties of designing a jet engine to perform at these levels are such that
it cannot even be seen how it could be done with present technology. The differences
between the engines are how they physically take the air in. Nanotechnology could solve the
problem by allowing the engine to reshape itself in flight, whether it could be shaped fast
enough remains to be seen.

Department of Mechanical Engineering 10 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

Fig.4.2 X-33 Venture Star

4.4.2 Two-Stage-To-Orbit (TSTO)

In the TSTO launch system, two independent vehicles operate. While the first stage
vehicle can return to the launch site for re-use, the second stage can return after flying one or
more orbits and re-enter. Stargazer is a TSTO vehicle with an expendable LOX/ RP upper
stage and a reusable fly back booster. It has a payload of 300lbs to low earth orbit. Advance
technology is used in the booster and the thermal protection system. The four LOX/LH2
ejector scramjet rocket-based combined cycle engines are used to power up the booster which
is Hankey wedge shaped. We can study the potential benefits of a fully reusable TSTO with a
separate ramjet and rocket propulsion system. The Saenger type TSTO vehicle having
subsonic air breathing propulsion in first stage and rocket propulsion in second stage can
deliver the specified payload mass and was found to be feasible, versatile. Starsaber is a
TSTO vehicle with a reusable winged booster and a LOX/RP-1 expendable upper stage. Two
hydrocarbons fuelled Ejector Ramjet (ERJ) engines are used to power up the booster. This
vehicle has a capability of 300lb payload into Low Earth Orbit (LEO) and utilizes advanced
technology in structural and thermal protection system materials. To explain the aerodynamic
forces, moments, and to determine the proximity flow environment a stage separation wind
tunnel tests of a generic TSTO launch vehicle were conducted. Radiance, a TSTO vehicle

Department of Mechanical Engineering 11 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

that stages at Mach 12 has an air breathing first stage and rocket-powered second stage. It
takes off horizontally with the help of integral landing gear. Radiance hampered by the high
drag losses because of its booster size. TSTO launch systems utilizing SSTO-class vehicle
technology, offer a better economic advantage for access to LEO. The below figure indicates
the diagram of a launch vehicle following the working of TSTO.

Fig.4.3 Two Stage To Orbit

4.4.3 One And A Half Stage To Orbit (OHSTO)

There are various 'One and a Half Stages' ideas that are certainly innovative ideas and
deserve mention. The most promising is that of mid-air fuelling, taking on the fuel and
oxidizer for space once at a high altitude. These ideas do not overcome the problems of
commercially viability that the 2-stage models suffer from; however it could be a good
temporary measure.

Department of Mechanical Engineering 12 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

CHAPTER 5
DESIGN OF RLV

The construction of a true RLV that can take a payload to space is still in the design
stage. It will sure have lot of designs taken from the space shuttle. Here are the main
construction details.

Body: The body of a RLV has to withstand very high stresses including thermal stresses
during re-entry. The plane expands due to the high heat of nearly 1500˚C or more. It also has
to cope with the rapid change in temperatures once in space. It changes from -250 degrees in
the shade to 250 degrees in direct sunlight. This change in temperature between two sides of
the same plane will put a lot of stress on its body. Titanium alloys are being used, being very
strong and light. To cope with the high temperatures developed in parts of the wing and
fuselage of the spacecraft today, reinforced carbon-carbon composite material is being added
to the leading edges of the vehicle's nose and wings to handle the higher temperatures.
Researches are being conducted to find the best materials for different parts of the
plane. One of these materials, γ-TiAl (Titanium Aluminide), has superior high-temperature
material properties. Its low density provides improved specific strength and creep resistance
in comparison to currently used titanium alloys. However, it is inherently brittle, and long life
durability is a potential problem along with the material’s sensitivity to defects.

Wings: The wing of the spacecraft has to be designed so that it provides enough lift to fly to
space and also reduce the friction during re-entry.

Cockpit: The cockpit is the place where the astronauts will stay most of the time during the
journey. It will have many windows, which are special double-paned glass, and each pane
alone can withstand the pressure and force of flight and the vacuum. This doubling up
ensures that if either window were to crack, the passengers would still be safe.
The air inside the cockpit is made breathable by a three-part system. Breathable air is
added at a constant rate by oxygen bottles. The exhaled carbon dioxide is removed from the
cabin by an absorber system, and humidity is controlled by an additional absorber created to
remove water vapor from the air. During the entire flight, the cockpit remains comfortable,
cool and dry.

Department of Mechanical Engineering 13 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

The avionics system and display unit for navigating has to be computer controlled
and free from bugs. It should give the pilot all the necessary data to make his choices. The
avionics are very critical, and it also needs to be very precise for the pilot to do what he
wants to do, and do it well.

Electric Power: The electrical power required for the running of the spacecraft has to be
taken from batteries. These batteries could be charged, if needed by using solar energy.
Researches are being initiated to find better and reliable batteries, like the lithium-based (i.e.,
Li metal or Li-ion intercalation compound as negative electrode), polymer electrolyte
regenerative battery system. Its advantages include reduced battery weight and volume,
relative to conventional Ni-Cd and Ni-H2, which permits greater payloads and greater cell
voltage, 3.5 volts vs. 1.2 volts, which permits use of fewer cells and results in reduced battery
system complexity.

Controls: When we're out in space, all you need to do is release a puff of air in a direction to
give you a reaction force to push you the other way. That is called a reaction control system.
High-pressure air is stored in bottles on the ship, and on the release of a little blast of air for
about one second, for example, with the right wing tip pointing up. And that is enough when
you're in space to push that wingtip down. It effectively rolls the aircraft, and that are the
controls when it is out in space.

Fuels: Many challenges have been overcome recently by the discovery and synthesis of
propellants that can have higher performance than traditional O2/H2, and aircraft fuels. These
propellants include high-density monopropellants for sounding rockets and upper stages, and
onboard propulsion for small spacecraft. Higher energy fuels, such as N4, N6, BH4, and
others, have a longer range development time and would be more applicable to future launch
vehicles.

Department of Mechanical Engineering 14 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

5.1 THERMAL PROTECTION SYSTEM

The thermal protection system (TPS) for the RLV must protect the structure and
cryogenic fuel tanks from extremely high temperatures during launch and re-entry. To meet
the requirements of an RLV, the TPS must be readily producible, lightweight, operable, and
reusable with a minimum lifetime of 100 missions. The TPS for the RLV must have an
adverse weather capability with 95 percent availability. The TPS must also exhibit an order
of magnitude reduction in maintenance and inspection requirements as compared with the
existing shuttle TPS to permit rapid turnaround. Unfortunately, during the course of this
study, the committee could not obtain the breakdown of the total shuttle maintenance and
inspection figures, including the TPS, both in terms of cost and manhours.

The space shuttle orbiter TPS, the only demonstrated reusable TPS, provides valuable
lessons for development of the RLV TPS. The aluminum orbiter structure has successfully
remained within temperature limits, and the primary bonded attachment method has
prevented heat leaks directly into the structure. However, as shown in a detailed assessment
of TPS damage, (Table 4–1), the TPS systems covering various parts of the orbiter were
exposed to temperatures beyond their true reuse limits, causing embrittlement, the slumping
of edges, and overheating, cracking and flaking of the coating. Damage to ancillary TPS
systems (e.g., gap fillers, thermal barrier coatings, filler bars) was especially high. The
designated orbiter TPS reuse temperatures (Table 4–2) are obviously too high because
irreversible changes in exposed materials occurred at those temperatures. Additional damage
was caused by lift-off and landing debris (chips, gouges) and by airflow and pressure
gradients (erosion, fabric frays and tears, lost gap fillers). This lack of TPS robustness and
resiliency would result in repair/replacement times and manhours that do not meet RLV
goals.

Another factor that contributes to the long TPS turnaround time and high cost after
each flight is extensive re-waterproofing, which is necessary for many of the tiles and
blankets on the orbiter to prevent them from absorbing moisture; additional moisture would
increase vehicle weight and, therefore, reduce payload to orbit.

Department of Mechanical Engineering 15 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

CHAPTER 6

WORKING

The working of a RLV can be divided into 4 stages:

6.1 FIRST STAGE- SUBSONIC AND SUPERSONIC STAGE

The RLV with its payload takes off from the runway and climbs to about 100,000 feet
or 30km using conventional jet-engines, or using a combination of conventional jet-engine
and ramjet engine, or using another plane to carry or pull the plane to a lower height and
using a booster rocket.

A ramjet operates by subsonic combustion of fuel in a stream of air compressed

by the forward speed of the aircraft. It doesn’t have or use very less moving parts compared
to a conventional jet-engine with thousands of moving parts. The compression of air before
burning of fuel is done in the ramjet by the addition of a diffuser at the inlet, while it is done
by the turbine in conventional jet-engine. The flow of air is subsonic.

The plane is accelerated to a speed of mach 4 or mach 5 and the flow inside the
engine becomes supersonic. Then the scramjet is powered up.

6.2 SECOND STAGE-HYPERSONIC STAGE

When the space-plane is at an altitude of about 100,000 ft and at a velocity of about

mach 4, the scramjets are fired. Scramjets are basically ramjets. They introduce fuel and mix
it with oxygen obtained from the air which compressed for combustion. The air is naturally
compressed by the forward speed of the vehicle and the shape of the inlet, similar to what
turbines or pistons do in slower-moving airplanes and cars. Rather than using a rotating
compressor, like a turbojet engine does, the forward velocity and aerodynamics compress the
air into the engine. Hydrogen fuel is then injected into the air stream, and the expanding hot
gases from combustion accelerate the exhaust air to create tremendous thrust. While the
concept is simple, proving the concept has not been simple. At operational speeds, flow
through the scramjet engine is supersonic - or faster than the speed of sound. At that speed,

Department of Mechanical Engineering 16 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

ignition and combustion take place in a matter of milliseconds. This is one reason it has taken
researchers decades to demonstrate scramjet technologies, first in wind tunnels and computer
simulations, and only recently in experimental flight tests. The Scramjet engine takes the
RLV to even greater heights and to speeds of up to Mach 15. This is the fastest speed an air
breathing plane can go using current technologies. At Mach 15, the RLV is at a great height
that there isn’t enough oxygen to sustain the scramjet engine. At this point the rocket engine
fires up.

6.3 THIRD STAGE- SPACE STAGE

The rocket engine fires , by mixing oxygen from the onboard storage tanks into the
scramjet engine, thereby replacing the supersonic airflow. The rocket engine is capable of
accelerating the RLV to speeds of about Mach 25, which is the escape velocity. It takes the
RLV into orbit. The rocket engine takes the RLV to the payload release site and the required
operations are done. Once this is over it enters its last stage – the re-entry stage.

6.4 FOURTH STAGE – RE-ENTRY STAGE

Once the RLV finishes its mission in space, It performs de-orbit operations, including
firing its thrusters to slow itself down, thereby dropping to a lower orbit and eventually
entering the upper layers of the atmosphere. As the vehicle encounters denser air, the
temperature of the ceramic skin builds to over 1,000 degrees C, and is also cooled by using
any remaining liquid hydrogen fuel. It is here that the structure of the plane undergoes heavy
thermal stress. If the heat shields do not protect the plane, it would simply burn off to the
ground, just like the space shuttle Columbia. It enters a radio silence zone as due to the heat,
radio contact is lost. Once it reaches dense air, it can use its aerodynamics to glide down to
the landing strip. It can also use any remaining fuel to fire the ramjet or conventional jet
(depends on the design) and change its course. Once on the landing strip it engages it slows
down using a series of parachutes and engages the brake.

Department of Mechanical Engineering 17 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

CHAPTER 7

LANDING AND TAKE OFF SYSTEMS

Reusable systems can come in single or multiple stages to orbit configurations. For
some or all stages the following landing system types can be employed.

7.1 BRAKING

These are landing systems which employ parachutes and bolstered hard landings, like
in a splashdown at sea. Though such system have been in use since the beginning
of astronautics to recover space vehicles, particularly crewed space capsules, only later have
the vehicles been reused. E.g.:

 Space Shuttle solid rocket boosters.

 Space Shuttle growth study recoverable liquid boosters

7.2 HORIZONTAL LANDING

In this case the vehicle requires wings and undercarriage (unless landing at sea). This
typically requires about 9-12% of the landing vehicle to be wings; which in turn implies that
the take-off weight is higher and/or the payload smaller. Concepts such as lifting bodies
attempt to deal with the somewhat conflicting issues of re-entry, hypersonic and subsonic
flight; as does the delta wing shape of the Space Shuttle.

Fig.7.1 Horizontal Landing

Department of Mechanical Engineering 18 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

7.3 VERTICAL LANDING

Parachutes could be used to land vertically, either at sea, or with the use of small
landing rockets, on land (as with Soyuz). Alternatively rockets could be used to softland the
vehicle on the ground from the subsonic speeds reached at low altitude (see DC-X). This
typically requires about 10% of the landing weight of the vehicle to be propellant. A slightly
different approach to vertical landing is to use an autogyro or helicopter rotor. This requires
perhaps 2-3% of the landing weight for the rotor.

Fig.7.2 Vertical Landing

7.4 HORIZONTAL TAKE OFF

The vehicle needs wings to take off. For reaching orbit, a 'wet wing' would often need
to be used where the wing contains propellant. Around 9-12% of the vehicle takeoff weight is
perhaps tied up in the wings.

7.5 VERTICAL TAKE OFF

This is the traditional takeoff regime for pure rocket vehicles. Rockets are good for
this regime, since they have a very high thrust/weight ratio (~100).

Department of Mechanical Engineering 19 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

CHAPTER 8

TECHNOLOGIES REQUIRED FOR RECOVERY

Recovery of hardware from space requires atmospheric reentry, deceleration, and

landing. Reentry can be accomplished either by via retro-propulsion, or by utilizing the
atmosphere to decelerate the object via aerodynamic drag. Atmospheric deceleration at
reentry velocities requires an aeroshell featuring a thermal protection system (TPS) to protect
the payload. The aeroshell has historically been limited in diameter and area by the launch
vehicle shroud. The HIAD, with its inflatable structure and flexible TPS, is an emerging
technology with significant promise. HIAD can be densely packed and inflated exo-
atmospherically to create a heat shield with significantly more area than a traditional rigid
heatshield. Two landing technologies are described: impact attenuation airbags and MAR.
Recent developments in MAR have yielded in a highly reliable and practical technology
which enables an object to be delivered to a precise location with virtually no impact
acceleration. This becomes particularly attractive for returning rocket engines which are
sensitive to impact and contamination (especially salt water).

8.1 RETRO-PROPULSION

Retro-propulsion is probably the most intuitive method of all: just reverse the launch
process. It was used by Herge to land Tintin on the moon in the 1953 comic book; and by the
Apollo program to land man on the moon for real in 1969, and for good reason: the moon has
no atmosphere, which rather limits EDL options. It is also very expensive in the sense that the
fuel required for landing must be carried to space, which erodes the useable payload capacity
of the launch system.

Department of Mechanical Engineering 20 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

Fig.8.1 Landing by Reverse Thrusting

8.2 MID AIR RECOVERY

MAR was developed and used extensively in the 1960s for recovery of payloads (film
canisters) from space for the Corona project. Recent developments in the technology have
demonstrated a technique that is both reliable and scalable up to (and beyond) a 10 ton
payload. MAR utilizes a ram-air main parachute that decelerates the payload. It also provides
a stable and predictable velocity vector that enables a helicopter equipped with a flying
articulated grapple to approach from the rear and capture the in-flight parachute and gently
transfer the payload mass from the parachute to the helicopter. The helicopter then transports
the payload to a precise location on land or sea (e.g., barge or ship) for final recovery. This
approach avoids high impact accelerations and/or emersion in salt water. Figure 9 shows
ULA’s Sensible Modular Autonomous Return Technology (SMART) reuse concept with
HIAD entry, guided parafoil descent and helicopter MAR. The large guided parafoil is a
mature technology used for precision airdrop. MAR has been successfully demonstrated for
1000 lbs class objects with a benign environment less than 1.2g. That technology needs to be
scaled up to the mass required for launch vehicle element recovery. However, the total mass
retrieved will be limited by helicopter capability. For instance, the heavy lift CH-53K
helicopter max external load capability is 36,000 lbs.

Department of Mechanical Engineering 21 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

Fig.8.2 Mid Air Recovery(MAR)

8.3 RECOVERY OF LAUNCH VEHICLE COMPONENTS

The HIAD design consists of an inflatable structure that addresses the drag forces, and
a protective flexible thermal protection system (F-TPS) that combats the thermal loading.
Hypersonic spacecraft entering the atmospheres of planets are traveling so fast that they
create a high-energy pressure wave. This pressure wave entraps and rapidly compresses
atmospheric gases, resulting in drag forces that decelerate the vehicle and thermal loads that
heat the vehicle.

Normally, flexible materials would not be able to withstand the drag forces a
spacecraft would encounter during atmospheric entry; however, the inflatable structure is
constructed out of a fastened series of pressurized concentric tubes, or tori, that form an
exceptionally strong blunt cone-shaped structure. The tori are constructed from braided
synthetic fibers that are 15 times stronger than steel. Though the inflatable structure has the
capability to withstand temperatures be yond 400 °C, the HIAD relies on the F-TPS to
survive entry temperatures

Department of Mechanical Engineering 22 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

Fig.8.3 HIAD

CHAPTER 9

ADVANTAGES AND ECONOMIC BENEFITS

9.1 ADVANTAGES

The rockets which take satellites and other payloads have to carry the fuel and
oxidizer with them as it uses conventional rocket engines. The combined weight of the fuel
and oxidizer is very large due to the fact that a lot of energy is expended pushing the plane
forwards. This is why today's rockets launch vertically as it maximizes the rocket's potential
by allowing all the energy expended to be focused in the direction we want to go - upwards.
With present technology it is the easiest and cheapest method of reaching space.

Clearly then the way forward is to utilize jet engines in some manner. The main
advantages of jet engines over rocket engines are that they do not need to carry their own
oxidizer; instead they suck in air and use the oxygen present in the air as their oxidizer. This
will greatly remove the need to carry oxidizer, as it will only be needed when at an altitude
that the air contains insufficient oxygen for jets to operate. At this point the rocket engines
will fire and burn the much smaller quantity of onboard oxidizer. This will dramatically
reduce the take-off weight and also the cost of the craft. Reduction in take-off weight means
the payload can be increased. Further to this the use of jet engines will make a substantial
saving on the expensive rocket fuel. As a comparison to produce the same thrust, jet (air-
breathing) engines require less than one seventh the propellants (fuel + oxidizer) that rockets
do. For example, the space shuttle needs 143,000 gallons of liquid oxygen, which weighs

Department of Mechanical Engineering 23 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

1,359,000 pounds (616,432 kg). Without the liquid oxygen, the shuttle weighs a mere
165,000 pounds (74,842 kg).

Another advantage of jet-engine craft is that as they rely on aerodynamic forces

rather than on rocket thrust, they have greater maneuverability, which in turn provides better
flexibility and safety, for example missions can be aborted mid-flight if there is a problem.
This is not the case for staged vehicles, which typically have complex "range safety"
requirements as the stages detach and fall back to earth. Range safety is one of the main
reasons that the US launches from Florida, where the rocket's flight path takes it out over
open water almost immediately. The lack of such abort modes on the Shuttle requires
incredible failure avoidance costs and massive overhauls.

The space shuttle used by NASA is partially reusable. It still has to take off vertically
with the help of multistage rocket and solid boosters. The use of rockets increases the cost of
manufacturing parts for each launch as some rocket parts are not reusable. Further more,
using rockets increases the amount of fuel and oxidizer required. Some of the components of
the rocket get added to the space debris and continue orbiting the earth. This causes unwanted
collisions with other debris or satellites. Thus using a jet-engine craft as a reusable launch
vehicle is faster, efficient, and has increased affordability, flexibility and safety for ultra high-
speed flights within the atmosphere and into Earth orbit.

9.2 ECONOMIC BENEFITS

An analysis of cost savings that could be realized on active debris removal (ADR)
missions through the use of reusable launch vehicles (RLVs) has been performed. Launch
vehicle price estimates were established for three levels of RLV development, based on
varying levels of technological development and market competition. An expendable launch
vehicle (ELV) price estimate was also established as a point of comparison. These price
estimates were used to form two separate debris removal mission cost estimates, based on
previously proposed debris removal mission concepts. The results of this analysis indicate
that RLVs could reduce launch prices to levels between 19.6% and 92.8% cheaper than
ELVs, depending on the level of RLV maturity. It was also determined that a RLV could be
used to realize total ADR mission cost savings of between 2.8% (for a partially RLV in an
uncompetitive market) and 21.7% (for a fully RLV in a competitive market).

Department of Mechanical Engineering 24 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

CHAPTER 10

CONCLUSION

A reusable launch vehicle should be constructed in such a way that it can be reused
for several missions whereas an Expendable Launch Vehicle (ELV) can be used only once
and it is very expensive. From the previous experiences and knowledge, a future reusable
launch vehicle should be constructed within low cost. Constructing a reusable launch vehicle
using Integrated Vehicle Health Management (IVHM) technologies and its basic objectives
offers saving in the operation costs. Autonomous reusable launch vehicles are considered to
be low cost alternatives. Future RLV are to be developed through an extensive flight
demonstration. This article provides an overview on what aspects should be concentrated on,
while constructing an RLV such as weight, thermal protection systems, increased propulsion,
propellants, payload capacity etc, gives an idea on design and different working stages of
RLV. Researchers are being done on the development of the Reusable launch vehicles and
the budding students who are interested in this stream; this provides an added advantage to
gain better knowledge, which would open opportunities in building up much advanced
version of RLV. As we all know, to make an advanced version it is very important to anyone,
on understanding the various current advancements in it and having a grip on the basic
aspects of RLV.

Department of Mechanical Engineering 25 Thejus Engineering College, Vellarakkad

Reusable launch vehicle Seminar Report 2020

REFERENCES

1. Bhavana, Y., N. Mani Shankar, and B. K. Prarthana. “Reusable Launch Vehicles:

Evolution Redefined.” Journal of Aeronautics & Aerospace Engineering 2.2 (2013): 1-5.
2. Blosser ML (1997) Development of metallic thermal protection systems for the reusable
launch vehicle. AIP Conf Proc 387: 1125-1144.
3. Bond WH, Yi AC (1994) Air liquefaction and enrichment system propulsion in reusable
launch vehicles. J Propul Power 10: 485-491.
4. Freeman Jr DC, Stanley DO, Camarda CJ, Lepsch RA, Cook SA (1995) Singlestage-to-
orbit-A step closer. Acta Astronaut 37: 87-94.
5. Freeman Jr DC, Talay TA, Austin RE (1997) Reusable launch vehicle technology
6. Kamran D (2001) Thermal Analysis and Design of Multi-Layer Insulation for Re-Entry
Aerodynamic Heating.
7. Kaplan MH (2002) Reusable launch vehicle facts and fantasies. AIP Conf Proc 608:
1181-1185.
8. Nebylov, Alexander, and Vladimir Nebylov. "Reusable space planes challenges and
control problems." IFAC-PapersOnLine 49.17 (2016): 480-485.
program. Acta Astronaut 41: 777-790.
9. Ragab, Mohamed, and F. McNeil Cheatwood. “Launch vehicle recovery and reuse.”
AIAA Space 2015 Conference and Exposition. 2015.
10. Zhong, Ya, Danghui Liu, and Chen Wang. "Research progress of key technologies for
typical reusable launcher vehicles." IOP Conference Series: Materials Science and
Engineering. Vol. 449. 2018.

Department of Mechanical Engineering 26 Thejus Engineering College, Vellarakkad