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I
A
SEMINAR REPORT
ON
“Magnetically Launching of Space Vehicle in
Earth’s Lower Orbit”
In partial fulfilment of requirements for the degree of
Master of Technology
In
Instrumentation and Control Engineering
(Specialization - Process Instrumentation)
Submitted By:
BHASE PRASAD SHASHIKANT
MIS NO: 121416017
Under the Guidance of
Dr. S.B. PHADKE
DEPARTMENT OF INSTRUMENTATION AND CONTROL
ENGINEERING
COLLEGE OF ENGINEERING
SHIVAJINAGAR, PUNE-411005
2014 - 2015
II
CERTIFICATE
This is to certify that the Seminar titled “Magnetically Launching of Space Vehicle in
Earth’s Lower Orbit” has been submitted by BHASE PRASAD S. under my guidance in
partial fulfilment of the degree of Master of Technology in Instrumentation and Control
Engineering with specialization in “PROCESS INSTRUMENTATION” of College of
Engineering, Pune during the academic year 2014-2015 (Sem-I) .
Date:
Place: Pune
Guide Head, Instrumentation Department
(Dr. S.B.Phadke) (Dr. S. L. Patil)
III
ACKNOWLEDGMENT
I would like to thank all those who have contributed to the completion of the
seminar and helped me with valuable suggestions for improvement. I would like to
thank Dr. S. B. Phadke, my guide and Dr. S.L. Pati l , Head, Department of
Instrumentation and Control, College of Engineering, Pune, for all help and support
extend to me.
I am extremely grateful to Dr. S.B. Phadke, for providing me with best
facilities and atmosphere for the creative work guidance and encouragement. I
thank all staff members of my college and friends for extending their cooperation
during my seminar. Above all I would like to thank my parents without whose
blessings I would not have been able to accomplish my goal.
IV
ABSTRACT
A Maglev system uses magnetic fields to levitate and accelerate objects along
a track, potentially providing initial vertical velocity prior to rocket ignition allowing
for smaller, lighter rockets. Previous tests have demonstrated that Maglev
technology could accelerate a spacecraft up to 600 mph, and then switch to a
conventional rocket propulsion system near the endpoint of the track. Maglev launch
assist provides many advantages over the conventional rocket launch and the report
presents a system approach documenting the launch assist and compares both
systems, essentially asking the question “would the investment be feasible compared
to conventional solid/liquid rockets?” The report continues analysing the system by
considering engineering challenges of construction, maintenance and power supply.
A case study is performed comparing conventional rocket launch to Maglev launch
assist on the basis of payload lifting capabilities, cost and environmental impacts.
V
CONTENTS
1. Introduction ………………………………………………….….. 1
2. Maglev Technology ………………………………………………3
2.1. Basic Terms ……………………………………………..3
2.1.1. Permanent Magnet ………………………………..3
2.1.2. Electromagnet ……………………………………..4
2.1.3. Superconductive Magnet …………….....................5
2.2. Maglev Principle ………………………………………..6
2.3. Working of Maglev Vehicle …………………………...7
2.3.1. Propulsion Force…………………………………..7
2.3.2. Levitating Force…………………………………...9
2.3.3. Lateral Guidance………………………………….11
3. Design Concepts of Maglev Launch Assist……………………..12
3.1. StarTram Gen-I ………………………………………...12
3.2. StarTram Gen-II ………………………………………..13
3.3. Maglifter ………………………………………………..15
4. Cost Analysis…………………………………………………….17
5. Environmental Impact ……………………………......................19
6. Summary & Conclusion …………………………………………20
7. References ……………………………………….........................21
VI
LIST OF FIGURES
2.1 Permanent Magnetic Field…………………………………3
2.2 Electromagnet……………………………………………...5
2.3 Propulsion Force…………………………………………...8
2.4 EDS System………………………………………………..9
2.5 EMS System……………………………………………….10
2.6 Combined Sketch of Propulsion, Levitation
and Lateral Guidance……………………………………...11
3.1 StarTram Gen-II Levitation Tube…………………………14
3.2 StarTram Gen-II Launch ………………………………….14
3.3 Maglifter Launch Assist Designed at NASA...……………16
LIST OF TABLES
4.1 Cost Analysis of Gen-I,II, Maglifter and Space Shuttle…..17
1
CHAPTER -1
INTRODUCTION
Achieving orbit in space, for both cargo and people is still considered a
great achievement, but in a time of limited budgets the use of conventional rockets
might not be the most efficient method. Placing a kilogram of payload into space
can reach $10, 000[1]. Considering the global economic crisis, space exploration
will be reduced if lower cost technologies fail to replace the current ones. There
are multiple technologies being proposed for space transportation and one of the
most realistic options is magnetic levitation (maglev) launch assist. A maglev
system uses a spacecraft that is magnetically levitated on a track to reduce
friction, and is propelled along the track to high speeds. A maglev train in Japan,
used for passenger transportation can achieve top speeds registered at 581
kilometres per hour (kph). The train’s success demonstrates that the technology
is available, and has the potential to provide an alternative for space exploration.
Compared to conventional rocket launch, the maglev spacecraft launch assist
seems to offer numerous advantages; this report examines the following three:
1) It works on electricity, which significantly reduces the operating costs.
2) It locates its equipment on the ground, which allows placing more payloads
into space.
3) It releases very few chemicals in the atmosphere.
The report presents three existing maglev designs, two developed by
StarTram and NASA’s MagLifter. The report then continues with a comparative
case study of maglev spacecraft system vs. conventional rocket launch. The report
compares these systems based on cost efficiency and environmental footprint. It
then discusses which system is the preferred based on these criteria. The analysis
is not just theoretical, but also describes the exact criteria for a practical maglev
system. The report touches the current global problems: the economic crises and
2
the alarming negative environmental situation. This type of analysis is important
for space exploration because it can demonstrate whether the maglev launch assist
approach is cost feasible compared to traditional rocket launch, and how it meets
the challenges of current environmental challenges.
3
CHAPTER-2
MAGLEV TECHNOLOGY
The creation of magnetic forces is the basis of all magnetic levitation. The
creation of a magnetic field can be caused by a number of things. The first thing
that it can be caused by is a permanent magnet. These magnets are a solid
material in which there is an induced North and South Pole. These will be
described further a little later. The second way that magnetic field can be created
is through an electric field changing linearly with time. The third and final way
to create a magnetic field is through the use of direct current.
2.1 Basic Terms
2.1.1 Permanent Magnet: -
The first type of levitation is the implementation through permanent
magnets. These magnets are made of a material that creates a north and a
south pole on them.
Fig.2.1 Permanent Magnet Field
4
The formal definition of a permanent magnet is “a material that
retains its magnetic properties after and external magnetic field is
removed.”
The whole idea behind permanent magnets is that like ends will
repels and opposite ends will attract. Permanent magnets require very little
if any maintenance. These magnets do not require cryogens or a large
power supply for operation. The magnetic field is measured vertically
within the bore of the magnet.
Disadvantages: -
1. Cost of the magnet is very high when put into large scale systems
2. Varying changes in the magnetic field
3. The ability to control is a constant magnetic force from a permanent
magnet is an ongoing problem
Different applications that use these types of magnets can be found
in a number of different areas. Examples of these applications are
compasses, DC motor drives, clocks, hearing aids, microphones,
speedometers, and many more.
2.1.2 Electro Magnet: -
The basic idea behind an electromagnet is extremely simple. By running
electric current through a wire, you can create a magnetic field. When this wire
is coiled around a magnetic material (i.e. metal), a current is passed through this
wire. In doing this, the electric current will magnetize the metallic core.
5
Fig.2.2 Electromagnet
By using this simple principle, you can create all sorts of things including
motors, solenoids, heads for hard disks, speakers, and so on. An electromagnet
is one that uses the same type of principles as the permanent magnet but only on
a temporary scale. This means that only when the current is flowing is there going
to be an induced magnet. This type of magnet is an improvement to the
permanent magnet because it allows somebody to select when and for how long
the magnetic field lasts. It also gives a person control over how strong the magnet
will be depending on the amount of current that is passed through the wire.
2.1.3 Superconductive Magnet: -
Superconductive magnets are the most common of all the magnets, and are
sometimes called ‘cryomagnets’. The idea behind the superconducting magnets
is that there is a material which presents no electrical resistivity to electrical
current. Once a current has been fed into the coils of this material, it will
indefinitely flow without requiring the input of any additional current. The way
that a material is able to have such a low resistivity to current is that it is brought
to very low temperatures. The temperatures that are commonly found in
superconducting magnets are around -258oC. This is done by immersing the coils
that are holding the current into liquid Helium; this also helps in maintaining a
homogenous magnetic field over time. The advantage to the superconducting
magnet is that they don’t require constant power from a source to keep up the
6
value of the current in the coils. Although a disadvantage is that they require an
expensive cryogen such as helium to operate correctly. The magnetic field is in
the direction of the long axis of the cylinder or bore of the magnet. Since the
resistance in the coils can cause the current to decay, cryogens reduce the
resistance to almost zero, which will help maintain a homogenous magnetic field
over time.
2.2 Maglev Principle: -
Maglev is short for magnetic levitation, which means that these trains will
float over a guide way using the basic principles of magnets.
There are two types of Maglev's: ones that use like magnets which repel
each other and ones that use opposing magnets that attract with each other. Ones
that use repelling magnets are called Superconducting Maglev's. The magnets
allow the train to float. Electromagnetic Maglevs use opposing magnets.
Superconducting Maglevs use very cold temperature magnets in order to
make electricity without any opposition. The magnets are then put on the bottom
of the train. When the train moves, it forms currents from the magnets in the
aluminium sheets placed in the guide way. Because of the repelling force, the
vehicle rises. Also in the guide way, separate electric currents pass through which
push the train forward. This system is also called as ‘ElectroDynamic System.’
Electromagnetic Maglev's go under the guide way. They use opposing
magnets that attract with each other. This allows the Maglev to pull upward
towards the guide way. Like the superconducting Maglev's, separate currents
make magnetic fields shift which allows the train to move forward. These
Maglev's travel about 3/8's of an inch away from the guide way. In order for the
magnets from not hitting the guide way, the lifting current must keep being fixed.
This system also called as ‘ElectroMagnetic System.’
7
The main parts of the Maglev:
1. Guide way and guide rails - keep the train to on track
2. Landing wheels
3. levitation coils - run along the base of the guide way (used in
superconducting maglevs)
4. Emergency landing wheel
5. superconducting magnets and propulsion coils - run along the base of guide
way (used in electromagnetic maglev's)
6. Linear induction motor - moves and brakes the vehicle on the track.
2.3 Working of Magnetic vehicle: -
Basically the construction depends on 3 different working forces.
i. Propulsion Force
ii. Levitating Force
iii. Lateral Guiding Force
2.3.1 Propulsion Force
This is a horizontal force which causes the movement of train. It requires 3
parameters.
i. Large electric power supply
ii. Metal coil lining, a guide way or track.
iii. Large magnet attached under the vehicle.
8
Fig.2.3 Propulsion Force
A linear motor or linear induction motor is essentially a multi-phase
alternating current (AC) electric motor that has had its stator "unrolled" so that
instead of producing a torque (rotation) it produces a linear force along its length.
Many designs have been put forward for linear motors, falling into two major
categories, low-acceleration and high- acceleration linear motors. Low-
acceleration linear motors are suitable for maglev trains and other ground-based
transportation applications. High-acceleration linear motors are normally quite
short, and are designed to accelerate an object up to a very high speed and then
release the object, like roller coasters.
Maglev vehicles are propelled primarily by one of the following three options:
a. Linear synchronous motor (LSM) in which coils in the guide way are
excited by a three phase winding to produce a traveling wave at the speed
desired; Trans Rapid in Germany employs such a system.
b. Linear Induction Motor (LIM) in which an electromagnet underneath the
vehicle induces current in an aluminium sheet on the guide way.
c. Reluctance motor is employed in which active coils on the vehicle are
pulsed at the proper time to realize thrust.
9
2.3.2 Levitating Force
The levitating force is the upward thrust which lifts the object/vehicle in
the air.
There are 3 types of levitating systems
i. EDS system
ii. EMS system
iii. INDUCTRACK system
Levitating force is produced due to the eddy current in the conducting ladder
by the electromagnetic interaction. At low speed the force due to induced poles
cancel each other. At high speed a repulsive force is taken place as the magnet is
shifted over a particular pole.
A. EDS System: -
In EDS both the rail and the train exert a magnetic field, and the train
is levitated by the repulsive force between these magnetic fields. At slow
speeds, the current induced in these coils and the resultant magnetic flux is
not large enough to support the weight of the train. For this reason the train
must have wheels or some other form of landing gear to support the train
until it reaches a speed that can sustain levitation.
Fig.2.4 EDS System
10
On board magnets and large margin between rail and train enable
highest recorded train speeds (581 km/h).This system is inherently stable.
Magnetic shielding for suppression of strong magnetic fields and wheels
for travel at low speed are required. It can’t produce the propulsion force.
So, LIM system is required.
B. EMS System: -
Maglev concepts using electro -magnetic suspension employ
attractive forces. Magnetic fields inside and outside the vehicle are
insignificant; proven, commercially available technology that can attain
very high speeds (500 km/h); no wheels or secondary propulsion system
needed.
Fig.2.5 EMS System
The separation between the vehicle and the guideway must be
constantly monitored and corrected by computer systems to avoid collision
due to the unstable nature of electromagnetic attraction.
C. Inductrack System: -
The inductrack guide way would contain two rows of tightly packed
levitation coils, which would act as the rails. Each of these “rails” would
be lined by two Halbach arrays carried underneath the maglev vehicle: one
positioned directly above the “rail” and one along the inner side of the
“rail”.
11
The Halbach arrays above the coils would provide levitation while
the Halbach arrays on the sides would provide lateral guidance that keeps
the train in a fixed position on the track.
The track is actually an array of electrically-shorted circuits
containing insulated wire. In one design, these circuits are aligned like
rungs in a ladder. As the train moves, a magnetic field repels the magnets,
causing the train to levitate.
2.3.3 Lateral Guidance Force: -
Guidance or steering refers to the sideward forces that are required to make
the vehicle follow the guideway. The necessary forces are supplied in an exactly
analogous fashion to the suspension forces, either attractive or repulsive. The
same magnets on board the vehicle, which supply lift, can be used concurrently
for guidance or separate guidance magnets can be used. It requires the following
arrangements:
• Guideway levitating coil
• Moving magnet
Fig.2.6 combined sketch of Propulsion, Levitation and Lateral Guidance
12
CHAPTER-3
DESIGN CONCEPTS OF MAGLEV LAUNCH ASSIST
The two developed concepts of maglev launch assist are StarTram and
MagLifter.
StartTram is an innovative lunch concept that proposes levitating the
launching track tube high above the earth surface where the air has low density
and allows for lower air drag. The spacecraft placed inside the tube will accelerate
at 8 km per second (kps) enough to place it into the Lower Earth Orbit (LEO).
This is the second generation of StarTram – Gen II – which transports passenger
into space. Gen I is theoretically designed for cargo transportation, and it does
not require a launch tube. Instead it uses a track to be launched from the top of a
mountain at velocities greater than Mach 8. Because Gen II transports passengers
it takes into account the high heating and increased friction, and requires
launching the vehicle at high attitude in a long magnetically levitated tube.
Estimated an elevation of approximately 18 km. [1]
MagLifter is another maglev launch assist concept and was part of the
NASA reusable launch vehicle system. Small scale experiments were conducted
at the NASA Marshall Space Flight Center in Huntsville, USA (Figure I). The
MagLifter spacecraft is escalated on a magnetically levitated sled on a track, and
like Gen I it does not require a tube. The two concepts are described in more detail
below.[3]
3.1 StarTram Gen-I
Gen I system is designed for cargo only, and as mentioned it requires an
acceleration tunnel only. The cargo craft is 2 meters in diameter, 13 meters long
and with a 40 metric ton weight. It is intended to accelerate the craft at 30 G in a
13
~ 100-km length tunnel that is evacuated of air with the help of Magnetic Hydro
Dynamic “window”. The high G level allows building a short acceleration tunnel
and therefore reduces the cost of building the system. The biggest challenge with
operating a short tunnel to high acceleration of 8 kps is the large power storing
and quick power delivery. A good system for electricity operation that allows
both a very short delay between charge and discharge and high power generation
is the superconducting magnetic energy storage (SMES) system. This system can
be designed to include 60 loops of 250 meters in diameter that will allow the
storage of 3,000 Gigajoules (GJ), more than enough to accelerate the 40 metric
ton craft of 1280 GJ. [1]
According to Powell and Maise(Scientists), the potential launch sites for
Gen I have to be close to a low populated area with the minimum flight over land.
This will create a more secure area and less noise disturbance. They also suggest
that the launch attitude is preferable to be at least at an attitude of 4 km in order
to contribute to lower air drag and heating. The last criteria proposed by the author
is a launch into the polar orbits that allows high resolution environmental
monitoring and better survey of all areas around the Earth. The potential launch
site that would meet all the above criteria would be Antarctica.[1]
3.2 StarTram Gen-II
Gen II vehicle is launched from an elevated tube at an altitude of 18 km.
Superconducting wires are buried into the ground and placed on the launch tube.
The repulsive force levitates the tube attached to the Kevlar cables as shown in
the Figure II. The level of 2-3 G is significantly lower than the cargo craft G level
and allows passenger transportation. Because of the slow acceleration Gen II
requires a long track of up to 1600 km as sketched in Figure III. The accelerating
track tube seven meters in diameter consists of the acceleration tube (1280 km
long) at the ground level and the elevated launch tube (281 km long). The current
14
required to levitate four tons per meter is 14 Mega-amps (MA) in the levitated
cables and 280 amps (A) in the ground cables [5]. At a first glance, Gen II seams
to face more engineering challenges then Gen I considering the elevation of a
long tube above the ground. Nevertheless, using Ampere’s force law, the amount
of current needed in the ground superconductors to elevate the tube (around 280
x 106 A) at an attitude of 20-km is 20 times more than current on the tube.
Niobium-titanium superconductors can be resistant enough to deliver this amount
of current with its conventional critical current density of 5 x 105 A/cm2. Because
the power supply required is more than the usual power grid, a power generation
facility is located nearby. The reusable vehicle would return on a horizontal
guideway in the same manner like the Space Shuttle.[7]
Fig.3.1 StarTram Gen-II Levitated tube supported by Kevlar Cable [5]
Fig.3.2 StarTram Gen-II Launch System sketch divided into the long
acceleration tube located on the ground and the elevated part tube 18 km above
the ground [7]
15
3.3 Maglifter: -
The MagLifter is a spacecraft launch system to the LEO created by the
NASA program on Highly Reusable Space Transportation. Compared to other
maglev launch concepts MagLifter does not require extremely high accelerations
and high rates to achieve economical operations. The MagLifter is the next
generation of many “gun” assists ideas, and it consists of launching the vehicle
from a sled that is accelerated on a three to four mile track. The design was
invented, as mentioned, by Mankins who was the manager of Advanced Concept
Studies at NASA in 1994. The architecture of MagLifter system consists of the
following major substructures: the catapult, power systems, structural support
systems and supporting systems:
i. Catapult: - The catapult includes the maglev guideway, the accelerator-
vehicles and the accelerator-carrier staging facility. The accelerator will be
enclosed in a tunnel and will be filled with a helium gas that would allow
low drag forces.
ii. Structural Support: - The structural support will require complicated
engineering design and will depend on whether the guideway is placed on
the exterior of the mountain, on the side of the mountain or in a tunnel
inside the mountain.
iii. Power System: - A substantial local power supply system is needed to
provide enough launch energy that would charge from the local power grid.
16
Fig. 3.3 MagLifter Launch Assist designed at NASA
Marshall Space Flight Center, Huntsville, USA[4]
The reusable vehicle accelerates at 550 miles per hour (885 kph) and at the
end of the guideway, ascends to the Earth orbit and separates from the sled. The
3 G acceleration will allow passenger transportation similar to Gen II. The vehicle
is accelerated efficiently because of the absence of friction between the sled and
the guideway created by the superconducting magnets lined on the sled bottom
and the conductive plates on the guideway. After the launch the sled returns to
the starting point and is reused again for the next launch. Argus, the MagLifter
vehicle is powered by two supercharged ramjet and rocket-based combined-cycle
engines that use liquid hydrogen and liquid oxygen fuels. Argus can be designed
from 170 to 225 feet (52 to 67 m) in length with a 51 to 60 foot (16 to 18 m)
wingspan. The vehicles weights run from 600,000 to 1 million pounds (273,000
kg to 455,000 kg) and can deliver up to 20,000 pounds (9, 000 kg) into the LEO.
Argus returns back as a glider in the same way as the Space Shuttle. The possible
location for the launch facility of MagLifter is the Kennedy Space Center since it
one of the closest U.S. locations to the equator and facing East to the Ocean. [3],
[4]
17
CHAPTER-4
COST ANALYSIS
One primary element of these studies is comparing the investment budget
and the operational costs associated with placing a kilogram of payload into
space. This cost comparison is essential to possible future investment due to the
current global economy.
A detailed cost for StarTram system is proposed by Powell and it is
important to mention that the cost for Gen I includes building two acceleration
tunnels (operational and reserve). The length of both tunnels is twice as long (260
km), therefore the budget for excavating the tunnel will double. In the Gen I
system the spacecraft and the Magnesium diboride (MgB2) are non-recoverable,
so we will move the cost of the MgB2 superconductors to the operational costs
for the final calculations. The detailed budget description of Gen I and Gen II
estimated by Powell is presented in Table I. The MagLifter program estimates a
cost of 2 billion for a large scale project. [6],[7]
The payload delivered to LEO by Endeavour is 24,400 kg and will be used as the
average payload for U.S. Space Shuttle in further calculations.
Table 4.1: Gen I, Gen II, MagLifter and Space Shuttle
Launch Cost/kg of Payload.
18
The investments cost for building MagLifter system seem very low so it is
hard to make any conclusions. Gen I has high operational costs because of the
non-reusable MgB2 superconductors that cost the project around 3 billion extra
each launch. Gen II launch cost is the most convenient because of low operational
costs which is the basic idea of potentially using the magnetic levitation launch
system. Space Shuttle Launch is eight times more expensive than Gen II.
However, this rate is not high enough for a big scale project like spacecraft
launch, and it does not necessarily conclude the cost efficiency of one project
over another. The cost predictions for maglev launch projects are very low, and
so were the NASA initial predictions of Space Shuttle costs. Since Maglev is still
a theoretical concept and it faces many engineering challenges, more research
needs to be performed in order to make accurate final conclusions.
19
CHAPTER-5
ENVIRONMENTAL IMPACT
The maglev spacecraft system’s carbon emissions occur from energy
consumption at the launch stage where the power supply is vast in order to lift the
tube and/or accelerate the spacecraft. Therefore, the most negative impact on the
environment occurs from the emissions produced by the power source.
StarTram does not use engines for launch and so it doesn’t burn fuels [14], while
MagLifter and the Space Shuttle require engines that use liquid hydrogen and
liquid oxygen fuels.
20
SUMMARY AND CONCLUSION
All three systems are similar and different in regards to their engineering
structure and costs. Gen I launched its spacecraft from a track and is accelerated
to 8 kps. The 30 G acceleration does not allow passenger transportation, therefore
the spacecraft is non-reusable. Gen II is a very well though concept that can be
compared to Space Shuttle best since it creates a 3 G acceleration allowing
passenger transportation. The low acceleration and human transportation requires
building a longer tunnel at higher attitudes. The Gen II tube is magnetically
levitated 20 km above the ground where the air is less dense allowing lower
heating and lower air drag. The investment costs for Gen II are higher but the
operational costs lower since the spacecraft is reusable. MagLifter spacecraft is
launched from a sled on a short track (3 km) at a speed of 885 kph, but it uses its
engines for further ascending stages. The concept was experimented before on
small scales at NASA Marshall Space Flight Center, Huntsville, USA.
The costs analysis was done assuming 135 spacecraft launches for the
Space Shuttle. Gen I is a more expensive concept then Gen II because of its higher
operational costs due to the non-reusable spacecraft and MgB2 superconductors
Gen II is a theoretical concept and will require further research of the engineering
challenges.
Based on costs and the environmental impact Gen II is an excellent design
and potentially better than the Space Shuttle. While the cost of maintaining and
operating Gen II are very low.
21
REFERENCES
1. Powell, J.; Maise, G., "StarTram: The Magnetic Launch Path to Very Low
Cost, Very High Volume Launch to Space," Electromagnetic Launch
Technology, 2008 14th Symposium on , vol., no., pp.1,7, 10-13 June 2008
2. J. R. Hull and T. M. Mulcahy, “Magnetically levitated space elevator to
low earth orbit,” in Proc. 3rd International Symposium on Linear Drives
for Industrial Applications, Nagano, Japan, October 2001, pp.42–47.
3. J. H. Schultz, A. Radovinsky, R. J. Thome, B. Smith, J. V. Minervini, R.
L. Myatt, R. Meinke, and M. Senti, “Superconducting magnets for
maglifter launch assist sleds,” IEEE Trans. Appl. Supercond., vol. 11, pp.
1749–1752, 2001.
4. NASA Marshall Space Flight Center
http://www.nasa.gov/centers/marshall/news/background/facts/astp.html_p
rt.htm
5. Spacedaily
http://www.spacedaily.com/news/rlv-99y.html
6. Powell, James, et al. "Maglev Launch: Ultra-low Cost, Ultra-high Volume
Access to Space for Cargo and Humans." Aip Conference Proceedings.
Vol. 1208. No. 1. 2010.
7. Powell, J., George Maise, and John Paniagua. "StarTram: An Ultra-Low
Cost Launch System for Large Scale Exploration and Commercialization
of Space."55th International Astronautical Congress 2004.