NuclearTherma Rocket

A
Seminar Report
On
“NUCLEAR THERMAL ROCKET”
(Subject Code: 10AE86)
Submitted to
VISVESVARAYA TECHNOLOGICAL UNIVERSITY
Belgaum-590018
In partial fulfilment of the requirement for award
Of the degree of
BACHELOR OF ENGINEERING
In
AERONAUTICAL ENGINEERING
For the academic year 2014-2015
Submitted By
MANJUNATH RAVI HEGGADE D
USN: 1MJ11AE027
Under the Guidance of
INTERNAL GUIDE:
Mrs Varsha P Hotur
Assistant Professor
Department of Aeronautical Engineering
MVJCE, Bengaluru-560067
MVJ College of Engineering
Bengaluru-560067

Nuclear Thermal Rocket 2
An ISO 9001:2008 Certified Institution
Affiliated to VTU Belgaum, Approved by AICTE, Accredited By NBA
CHANNASANDRA, NEAR ITPB, BANGALORE – 560 067
CERTIFICATE
This is to certify that the seminar report entitled
“NUCLEAR THERMAL ROCKET” is a bonafied work carried out by
MANJUNATH RAVI HEGGADE D bearing USN number 1MJ11AE027 in
partial fulfilment for the award of post graduate degree in Aeronautical
Engineering as prescribed by Visvesvaraya Technological University, Belgaum,
during the academic year 2014–2015.
Signature of Guide Signature of HOD
Mrs Varsha P Hotur Mrs Deepa.M.S
Assistant Professor Assistant Professor
DEPARTMENT OF AERONAUTICAL ENGINEERING

DECLARATION
I hereby declare that entire work presented in this dissertation entitled
“NUCLEAR THERMAL ROCKET”, embodies the report of my seminar work carried out
independently by me during 8th semester at MVJ COLLEGE OF ENGINEERING, Bengaluru,
under the guidance of Mrs. Varsha P Hotur, Assistant Professor, Department of Aeronautical
Engineering, M.V.J College of Engineering, Bengaluru affiliated to Visvesvaraya Technological
University, Belgaum. The work embodied in this dissertation is original and it has not been
submitted in part of full for any other degree in University.
MANJUNATH RAVI HEGGADE D [1MJ11AE027] _____________________
Date: 13/05/2015
Place: Bengaluru

ACKNOWLEDGEMENT
Successful completion of any task is based on guidance, encouragement and support of many
people. I hereby take this opportunity to express my heartfelt gratitude to those people who have
made this seminar successful.
I consider it a privilege to express my deepest gratitude and respect to Mrs. Varsha P Hotur,
Assistant Professor, Department of Aeronautical Engineering, M.V.J College of Engineering,
Bengaluru for her constant support.
I also grateful to Mrs. Deepa M S, H.O.D, Department of Aeronautical Engineering, M.V.J
College of Engineering, Bengaluru, for her continual support throughout the course.
And last but not least, I would like to thank all those members of Aeronautical Department who
have extended their support whenever I had any confusions and encouraging me to do better.

Abstract
Once nuclear energy became commonplace in the 1950s, fairly straightforward engineering
calculations could be made on the design of a nuclear rocket. These showed that designs using
conventional materials might achieve high thrust levels along with high Isp. Values in the range
of 750-950 seconds were typical — roughly three times as high as the best Isp from chemical
rockets.
Especially in the 21st century, the space has become the actual final frontier for mankind. The
possibilities are endless, as there are a lot of frontiers that can be covered in space exploration.
Unfortunately, two main problems prevail in space exploration. The first problem is that the
distances that need to be covered are extremely large and the second problem is the need for
energy for any outpost installation in space. Fortunately, the availability of nuclear technologies
allow for solution of these problems. In this paper, it is demonstrated that by using nuclear
technology, traveling time can be greatly reduced and the energy requirements of the astronauts
onboard a spacecraft or a space station can be met.

CONTENTS
1. Introduction
1.1 Description
2. Basics of Nuclear Propulsion
2.1 Basic Nuclear Physics
2.2 Nuclear Reactor
3. Types of Nuclear Rockets
3.1 Solid Core Nuclear Thermal Rocket
3.2 Gas Core Nuclear Thermal Rocket
3.3 Nuclear Salt Water Rocket
3.4 Nuclear powered Electric Rocket
3.5 Nuclear Pulse Rocket
3.6 Nuclear Fission Fragment Rocket
4. Specific Impulse
5. Advantage and Disadvantage
6. Conclusion
7. Reference

1. INTRODUCTION
1.1 Description
Nuclear rocket systems include thermal propulsion (“NTP”) systems, nuclear electric propulsion
(“NEP”) systems, hybrid NTP/NEP concepts, and nuclear pulse rockets that are propelled by the
force of nuclear explosions. Nuclear thermal propulsion systems provide thrust through the
heating of liquid hydrogen propellant by nuclear fission. There are several designs for nuclear
thermal rockets, including solid, liquid, and gas core nuclear rockets. Solid core nuclear rockets,
a relatively mature propulsion technology, operate by pumping the liquid hydrogen propellant
through narrow channels in a solid nuclear reactor. As liquid hydrogen moves through the
channels, it is heated by the reactor into a high temperature gas, and then ejected from the
exhaust nozzle of the rocket at high speeds. Liquid and gas core nuclear rockets operate
according to a similar principle, but, instead of using a solid fuel core to heat the hydrogen
propellant, they use a liquid or gaseous nuclear fuel, respectively. Solid, liquid, and gas core
nuclear propulsion systems have never been developed into an operational rocket. However, they
offer two potential major advantages over traditional chemical propulsion a substantially larger
specific impulse and a propellant with extremely low molecular weight. First, a large specific
impulse translates into faster travel and the possibility of carrying heavier, more complex, and
more experiment-laden payloads into space. Second, propellants with low molecular weight
increase the propulsive force per unit of propellant flow, allowing for an increased proportion of
a mission’s total weight to be composed of payload rather than propellant. Nuclear electric
propulsion systems, already employed on a number of orbital missions, use superconducting
magnetic cells to ionize gas and a nuclear reactor to heat the gas to high temperatures. The gas is
expelled at very high velocities to provide thrust. Although the total thrust of nuclear electric
propulsion is less than that of nuclear thermal propulsion, an electrical engine can provide
sufficient thrust over long periods of time to propel an unmanned spacecraft to the outer edges of
the Solar System. A different type of nuclear electric propulsion, an electro bombardment ion
engine uses electrical energy, rather than heat energy, to accelerate the exhaust gas to provide
thrust. Energy from the nuclear reactor is converted into electricity and then channeled through
an electrostatic grid to accelerate the ionized gas. Ion engines are considered particularly

promising; they combine high levels of conversion of electric power into thrust with much higher
exhaust velocities than chemical rockets and an extremely long operational lifetime. Perhaps, the
most futuristic and controversial of the nuclear propulsion concepts is a nuclear pulse rocket
propelled by actual nuclear explosions. The nuclear pulse rocket operates by ejecting specially-
constructed low-yield nuclear bombs, which explode some distance behind a large ablative
“pusher plate” at the rear of the spacecraft. The blast from each explosion bounces off the pusher
plate, which thrusts the vehicle forward through a system of special hydraulic shock absorbers.
Although such a vehicle has never been tested, it is one of the more intriguing options for
advanced space travel. It offers an even better utilization of the energy yield from the fission
reaction than a nuclear thermal rocket.
Fig 1.1 Schematic diagram of Nuclear Thermal Rocket

2. BASICS OF NUCLEAR PROPULSION
2.1 Basic Nuclear Physics
Nuclear physics is the field of physics that studies the constituents and interactions of atomic
nuclei.
• An atom consists of a small, positively charged nucleus surrounded by a negatively
charged cloud of electrons
• Nucleus
o Positive protons
o Neutral neutrons
o Bond together by the strong nuclear force
 Stronger than the electrostatic force binding electrons to the nucleus or
repelling protons from one another
 Limited in range to a few x 10
-15
m
• Because neutrons are electrically neutral, they are unaffected by Columbic or nuclear
forces until they reach within 10
-15
m of an atomic nucleus
o Best particles to use for FISSION
2.1.1 Fission
• Fission is a nuclear process in which a heavy nucleus splits into two smaller nuclei
• The Fission Products (FP) can be in any combination (with a given probability) so long
as the number of protons and neutrons in the products sum up to those in the initial
fissioning nucleus
• A great amount of energy can be released in fission because for heavy nuclei, the
summed masses of the lighter product nuclei is less than the mass of the fissioning
nucleus

2.1.2 Fission Reaction Energy
• The binding energy of the nucleus is directly related to the amount of energy released in a
fission reaction
• The energy associated with the difference in mass of the products and the fissioning atom
is the binding energy
  atomnep MmZAmmZ  )()(
2
cE 
2.1.3 Defect Mass and Energy
• Nuclear masses can change due to reactions because this "lost" mass is converted into
energy.
• For example, combining a proton (p) and a neutron (n) will produce a deuteron (d). If we
add up the masses of the proton and the neutron, we get
o mp
+ mn
= 1.00728u + 1.00867u = 2.01595u
o The mass of the deuteron is md
= 2.01355u
o Therefore change in mass = (mp
+ mn
) - md
= (1.00728u + 1.00867u) - (2.01355u)
= 0.00240u
o An atomic mass unit (u) is equal to one-twelfth of the mass of a C-12 atom which
is about 1.66 X 10
-27
kg.
• So, using E=mc
2
gives an energy/u = (1.66 X 10
-27
kg)(3.00 X 10
8
m/s)
2
(1eV/1.6 X 10-19
J) which is about 931 MeV/u. So, our final energy is 2.24 MeV.
• The quantity 2.24MeV is the binding energy of the deuteron.
2.1.4 Fission Probability
• When a neutron passes near to a heavy nucleus, for example uranium-235 (U-235), the
neutron may be captured by the nucleus and this may or may not be followed by fission.

• Capture involves the addition of the neutron to the uranium nucleus to form a new
compound nucleus.
o A simple example is U-238 + n  U-239, which represents formation of the
nucleus U-239.
o The new nucleus may decay into a different nuclide. In this example, U-239
becomes Np-239 after emission of a beta particle (electron).
• In certain cases the initial capture is rapidly followed by the fission of the new nucleus.
• Whether fission takes place, and indeed whether capture occurs at all, depends on the
velocity of the passing neutron and on the particular heavy nucleus involved.
dxdAEnP nffission  )(
• The probability that fission or any another neutron-induced reaction will occur is
described by the cross-section for that reaction.
• The cross-section may be imagined as an area surrounding the target nucleus and within
which the incoming neutron must pass if the reaction is to take place.
• The fission and other cross sections increase greatly as the neutron velocity reduces for
slow reaction fuels.
• For fast reaction fuels, a large activation energy requires high energy neutrons for fission.
2.1.5 Fission Fragments
Using U-235 in a thermal reactor as an example, when a neutron is captured the total energy is
distributed amongst the 236 nucleons (protons & neutrons) now present in the compound
nucleus.
• This nucleus is relatively unstable, and it is likely to break into two fragments of around
half the mass.
o These fragments are nuclei found around the middle of the Periodic Table and the
probabilistic nature of the break-up leads to several hundred possible
combinations.

Fig 2.1.5. Fission Fragments and chain reaction.
2.2 Nuclear Reactor
A nuclear reactor, formerly known as atomic pile, is a device used to initiate and control
a sustained nuclear chain reaction. Nuclear reactors are used at nuclear power plants for
electricity generation, propulsion of ships and also in nuclear thermal Rocket Propulsion system.
Fig.2.2 Schematic diagram of reactor
Components of Nuclear reactor
1. Reflector
 Reflects neutrons produced in the reaction back into the core
 Prevents neutron leakage
 Maintains reaction balance

 Can be used to reduce the size of the reactor
 Typically made of Beryllium
2. Moderator
• Slows down neutrons in the reactor
• Typically made of low atomic mass material
LiH, Graphite, D2
O
H2
O absorbs neutrons (light water reactor
3. Slow (or Thermal) Reactor
• Uses moderator to slow down neutrons for efficient fissioning of low activation energy
fuel.
• Fast Reactor
o No moderator. Uses high kinetic energy neutrons for fissioning of high activation
energy fuels.
4. Fuel Element
• Contains the fissile fuel
• Usually Uranium or Plutonium
• Contains the propellant flow channels
High thrust requires high contact surface area for the propellants
Heat exchange in the flow channels critical in determining efficiency and
performance of the system
5. Control Rods
• Contains material that absorbs neutrons
Decreases and controls neutron population
Controls reaction rate
When fully inserted, they can shut down the reactor

Configuration and placement is driven by the engine power level requirements
Typically made of Boron
• Axial Rods
Raised and lowered into place. Depth of rods in the reactor controls the neutron
population
• Drum Rods
Rotated into place with reflecting and absorbing sides
Fig 2.2. Nuclear reactor

3. TYPES OF NUCLEAR ROCKETS
3.1 Solid Core Nuclear Thermal Rocket
The solid-core NTR is the simplest type (simplest to build, compared to the others, but definitely
not simple in any absolute sense.)
The NERVA engines were of this type. Basically, it just replaces the chemical reaction
which heats up the propellant with a regular fission reactor. Some working fluid (NERVA used
hydrogen) is pumped through it.
The fluid heats up to near the temperature of the core and then is expelled as rocket exhaust.
NERVA is an acronym for Nuclear Engine for Rocket Vehicle Application, a U.S. nuclear
thermal rocket engine development program that ran for roughly two decades. NERVA was a
joint effort of the U.S. Atomic Energy Commission and NASA, managed by the Space Nuclear
Propulsion Office (SNPO) until both the program and the office ended at the end of 1972.
NERVA demonstrated that nuclear thermal rocket engines were a feasible and reliable tool for
space exploration, and at the end of 1968 SNPO certified that the latest NERVA engine, the
NRX/XE, met the requirements for a manned Mars mission. Although NERVA engines were
built and tested as much as possible with flight-certified components and the engine was deemed
ready for integration into a spacecraft, much of the U.S. space program was cancelled by
Congress before a manned visit to Mars could take place.
NERVA was considered by the AEC, SNPO and NASA to be a highly successful program; it
met or exceeded its program goals. Its principal objective was to "establish a technology base for
nuclear rocket engine systems to be utilized in the design and development of propulsion systems
for space mission application”. Virtually all space mission plans that use nuclear thermal rockets
use derivative designs from the NERVA NRX or Pewee.

Fig.3.1 NERVA = Nuclear Engine for Rocket Vehicle Application
The Advantage of Solid core nuclear thermal rocket are that it's simple and straightforward,
produces a lot of thrust and has decently high Isp
.
The Disadvantage is that to maximize Isp
you need to maximize the temperature of solid
materials, which becomes a very difficult problem very rapidly.
3.2 Gas Core Nuclear Thermal Rocket
In these, the core of the NTR (which must be the hottest component of any NTR) is gaseous and
confined within the reactor vessel by clever means (e.g. magnetic fields).
The heated propellant is expelled, and the plumbing can be actively cooled with these designs so
you can achieve very high Isp
while still maintaining the very high thrust (and thrust to weight
ratio) of solid core NTRs.

Fig 3.2.1 Gas core nuclear thermal rocket (closed cycle)
Fig 3.2.2 Gas core nuclear thermal rocket (open cycle)
Advantage
The heated propellant is expelled, and the plumbing can be actively cooled with these designs so
you can achieve very high Isp while still maintaining the very high thrust (and thrust to weight
ratio) of solid core NTRs.
Disadvantage

This design are that it is fairly complex and calls for technical advances. It also emits fairly large
amounts of radioactivity, which makes it unsuitable for use near Earth. Isp ranges are difficult to
peg accurately for gas core NTRs but the best guess would be about 1,500 seconds as a lower
limit up to about 3,000 seconds with probably a fairly substantial amount of headroom beyond
that.
3.3 Nuclear Salt Water Thermal Rocket
The nuclear salt water rocket creates a continuous fission chain reaction in a nuclear salt water
solution within the rocket engine.
The fission chain reaction is kept from spreading back into the fuel lines by the flow of the
nuclear salt solution; the idea (due to Robert Zubrin) is to maintain the flow at a rate which
pushes the fission zone just back of the nozzle, keeping the engine temperatures within tolerable
limits. .
Fig 3.3 Nuclear salt Water rockets
Advantage
There are several advantages relative to conventional NTR designs. As the peak neutron flux and
fission reaction rates would occur outside the vehicle, these activities could be much more
vigorous than they could be if it was necessary to house them in a vessel (which would have
temperature limits due to materials constraints). Additionally, a contained reactor can only allow
a small percentage of its fuel to undergo fission at any given time, otherwise it would overheat
and meltdown (or explode in a runaway fission chain reaction). The fission reaction in an NSWR

is dynamic and because the reaction products are exhausted into space it doesn't have a limit on
the proportion of fission fuel that reacts. In many ways this makes NSWRs like a hybrid between
fission reactors and fission bombs.
Disadvantage
The vessel's exhaust would contain radioactive isotopes, but these would be rapidly dispersed
after travelling only a short distance; the exhaust would also be travelling at high speed (in
Zubrin's scenario, faster than solar escape velocity, allowing it to eventually leave the Solar
System).
3.4 Nuclear Powered Electric Rocket
Electric rockets (such as the ion engine) also have high Isp values. However, they also have low
thrust — typically because to throw large quantities of reaction mass out of an electric rocket,
you need immense amounts of electric power. As of today, we have just one compact, long-
lasting source of such amounts of power, megawatts and above: the nuclear fission reactor. So
the idea is to couple a fission reactor to an ion engine (or another type of electric rocket such as a
Hall-effect thruster or a VASIMR).
Advantage
This gives you very high Isp without putting a lot of stress (meaning high temperatures) on the
reactor design
Disadvantage
The disadvantage is that nearly all conceivable electric rockets are very low thrust designs, even
with nuclear power. This means they cannot launch payloads from Earth; they are only suitable
for use in space and they may not provide much benefit in terms of lower travel times for many
conceivable space missions.

3.5 Nuclear Pulse Rocket
This type is popularly known as Orion. It uses nuclear bombs to provide thrust via a large pusher
plate, or via a leading sail (Medusa).
The Orion Multi-Purpose Crew Vehicle (MPCV) is a spacecraft intended to carry a crew of up
to four astronauts to destinations at or beyond low Earth orbit (LEO). Currently under
development by NASA for launch on the Space Launch System, Orion is currently intended to
facilitate human exploration of asteroids and of Mars, as well as to provide a means of delivering
or retrieving crew or supplies from the ISS if needed.
Fig 3.5 Orion rocket
Advantage
The Orion design is that it provides truly enormous thrust at high Isp.
Disadvantage
It doesn't scale down very well, requires the use of thousands of nuclear bombs, spews
radioactive fallout as "exhaust" (making it unsuitable for use from Earth's surface), and involves
quite a bit of tricky engineering. Designs vary, but achievable Isp values for Orion drives range
upward from about 10,000 seconds.

3.6 Nuclear Fission Fragment Rocket
Finally there is the totally speculative fission fragment rocket design, which uses the fisson
fragments from a highly fissionable isotope (such as Am-242) and directs them to create thrust
(e.g. using magnetic fields).
The advantage of this design is that it can produce very high Isp values.
The disadvantages are that it is very complex, requires enormously expensive6 fuels, and
produces fairly low thrust. The Isp achievable with such a rocket is on the order of 1,000,000
seconds

4 SPECIFIC IMPULSE.
Specific impulse (usually abbreviated Isp) is a measure of the efficiency of rocket and jet
engines. By definition, it is the impulse delivered per unit of propellant consumed, and is
dimensionally equivalent to the thrust generated per unit propellant flow rate.
What Increase Isp?
NP- What it really means ‘to increase Isp’
If J = specific energy (energy/unit mass)
1-D, ideal, propellants acceleration:
J = (1/2) V
e
2
Ve = exhaust velocity = Isp [m/s]
Thus:
Isp = V
e
= (2J)
1/2
 To increase Isp, J must be increased much more
Table.4.1 A brief review of the various types of nuclear (fission) rockets.
TYPE MAX Isp
(seconds)
THRUST
(relative)
Solid Core Nuclear Thermal Rockets 850-1,000 High
Nuclear-powered Electric Rockets 2,000-3,000 Low
Gas Core Nuclear Thermal Rockets 1,500-3,000 High
Nuclear Pulse Rockets >10,000 Extremely High
Nuclear Salt Water Rockets 5,000-100,000 Very High
Nuclear Fission-fragment Rockets 1,000,000 Moderate

5 ADVANTAGES AND DISADVANTAGE OF NUCLEAR PROPULSION
5.1 Advantages
 High Isp (2-10x that of chemical systems)
 Low Specific Mass (kg/kW)
 High Power Allows High Thrust
 High F/W
 Use of Any Propellant
 Safety
 Reduced Radiation for Some Missions
5.2 Disadvantages
 Political Issues
 Social Issues
 Low Technology Readiness Level (Maturity)
 Radiation issues (Shielding)
 High Inert Mass

CONCLUSION
The nuclear rocket is a potentially practical system which offers the combined advantages of
possessing a Specific impulse as high as the best electric propulsion system and a thrust/weight
comparable to the best high thrust chemical engines.
Nuclear salt water rocket system would be enormously beneficial for a host of high energy deep
space missions. What is need is a more detailed analysis utilizing sophiscated computational
fluid dynamics and multi-group neutronics codes to obtain a deeper understanding of the NSWR
and its ultimate potential performance.
.

REFERENCE
[1]. R. Zubrin (1991). "Nuclear Salt Water Rockets: High Thrust at 10,000 sec
I
SP
" (PDF). Journal of the British Interplanetary Society 44: 371–376.
[2]. Dr. David P. Stern (19 November 2003). "Far-out Pathways to Space: Nuclear
Power". From Stargazers to Starships. Retrieved 14 November 2012.
[3]. John G. Cramer (Mid-December-1992). "Nuke Your Way to the Stars (Alternate View
Column AV-56)". Analog Science Fiction and Fact.
[4]. project (Removed — Paste URL into the Way back Machine: 2002-July 2009)
[5]. Project Orion: Its Life, Death, and Possible Rebirth
[6]. Space Exploration and Nuclear Propulsion
[7].Nuclear Space — The Nuclear Space Technology Institute
[8]. Dr. Ralph L. McNutt, Jr. (31 May 1999). "A Realistic Interstellar Explorer" (PDF). Phase
I Final Report NASA Institute for Advanced Concepts.

NuclearTherma Rocket

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to NuclearTherma Rocket

Similar to NuclearTherma Rocket (20)

NuclearTherma Rocket