Conference Session C5
Paper 2136
ELECTROMAGNETIC AIRCRAFT LAUNCH SYSTEM; LAUNCHING INTO THE
FUTURE
Thomas Smyth (tjs79@pitt.edu)
Kevin Link (kel78@pitt.edu)
will be covered, as the system is not perfect. Most
importantly, we will discuss how a several thousand
kilogram aircraft is propelled off an aircraft carrier by the
Electromagnetic Aircraft Launch System.
Abstract- the Electromagnetic Aircraft Launch System is a
catapult that can send an aircraft soaring from a carrier
deck to the air in a matter of seconds utilizing electricity.
This technology has been developed over the years to
replace the steam powered catapults that has been
launching millions of aircraft of carriers for well over 50
years. The military and the government agreed that the
steam powered catapults have nothing left in the tank and
must be replaced with these new launch systems in order to
launch the new aircraft being developed. The EMALS was
developed using electromagnetic technology to launch
aircraft at alarming speeds while keeping the catapult as
light as a big difference from the heavier steam catapults.
There is a big challenge that the military faces when it
comes to using them on the high seas. The new carriers
that the EMALS are supposed to be installed into will soon
ready for them but the system is not fully ready to be placed
in the carriers and time is running out.
If the
Electromagnetic Aircraft Launch System is not ready, then
the military is forced to install the steam catapults which
would not only push the unveiling back even further but
cost the military millions of dollars.
STEAM: THE SYSTEM OF THE PAST
Before EMALS, carriers would use steam powered catapults
in order to launch an aircraft into the air. Steam powered
catapults have been assisting carriers in the launching of
aircraft's for well over 50 years. The idea of using steam to
power things has been around since the 1800s [3]. These
catapults would take steam from the boilers room in the
carrier (modern carriers utilize nuclear power to produce
steam) and store in one of the many sub-systems that exist
throughout the steam catapult system. These subsystems are
known as wet steam accumulators. The steam catapult
consists of eight major systems called steam system,
launching engine system, lubrication system, bridle
tensioning system, hydraulic system, retraction engine and
drive system, and catapult control system. [4] Each of these
systems have many sub-systems that play a major role
going from steam to seeing the aircraft flying off the carrier
in seconds. The steam system, which contains the wet steam
accumulator, heats the piping and values between the steam
plant and catapult up to an operating level. After this is done,
the steam gets released to the launch engine cylinders where
it stays until the crew is ready to launch the aircraft. [4] The
launching engine system’s main function is to apply steam to
the launching engine pistons during the process of launching
the jet off the carrier and even stopping the pistons at the
completion of the launch. The launching system consists of
many values that control the amount of steam that goes
through the system and the entire process of the launch [4].
The lubrication system makes sure that the launching engine
cylinder does not stick at all throughout the process by
injecting the cylinder with lubricating oil. This lubricating
oil is applied throughout the process in order to make sure
the launch is as smooth as possible. The bridle tensioning
system function is to make sure that the aircraft is tightly
connected to the shuttle prior to the catapult being launched
[4]. This steam has a set of components that focuses on
applying a certain amount of force to the shuttle which is
called external tension, while another set of components
focuses on applying an internal tension which causes the
retraction engine motor to slowly turn [4]. The hydraulic
system supplies fluid that has been pressured to all the
hydraulic components of the catapult [4]. Hydraulic means a
force applied at one point is transmitted to another using
Index terms- Electromagnetic Aircraft Launch System,
Steam catapult, electromagnetic, aircraft carriers, launch
science, electromagnetic system
THE NEW CATAPULT
Electromagnetic Aircraft Launch System or EMALS is the
latest technology that the United States government and
military is now developing for use in the next generation of
aircraft carriers. EMALS developers stated that this system
will provide enormous impulse power and energy to launch
various size aircraft off these carriers [1]. This launch
system will also reduce the amount of crew necessary to
maintain the launch system, increase rate at which aircraft
can be launched, reduce topside weight of the carrier, and
reduce the amount of space occupied by the launch system
(as compared to the steam system), among other things [2].
This system is now, finally, after years of testing and
changing first the scale model of the catapult, then a larger
version at a naval test facility will soon be ready to be
developed to fit inside the new carriers and lead the navy
into the future, launching a new generation of aircraft into
the air via a state-of-the-art system. In the coming sections,
we will discuss the previous system that will be replaced by
the EMALS and why this transition is necessary. Also, the
advantages and disadvantages of this new launching system
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some sort of fluid. This force is usually multiplied
throughout the process. The retraction engine and drive
system make use of components needed to return the
launching engine pistons and shuttle back to the battery
position after each and every launch or to maneuver the
grab. The grab is just a spring-loaded latch that is mounted
on a wheel frame and basically brings the shuttle and piston
back to the starting position in order to prepare the system
for the next launch. The last system of the steam catapult is
the catapult control system which is a series of panels, lights,
and switches used by the crew on the carrier to control the
catapult throughout the process. [4] Launching an aircraft
off a carrier by steam catapult is a very simple process to
understand but can seem complicated by all the systems in
the catapult. The process all starts, as stated before, in the
carrier’s boiler room where steam gathers into the steam
system. Once enough steam is collected into steam system,
the steam is then released to launching engine cylinders. The
amount of steam needed for each launch can varied by each
launch and must be control by capacity value which controls
the rate of steam released into the cylinders [4]. All this
steam acts on the set of steam pistons inside the launching
engine cylinders that are connect to a shuttle which is latch
onto the aircraft. The amount of force that the steam is
coming out of the steam accumulator is what causes the
aircraft to be launch off the carrier at enormous speeds [4].
This force being pushed on the pistons not only propels the
piston forward but causes the shuttle and aircraft to hit those
topping speeds in a few seconds until the entire takeoff is
complete. Once the aircraft is launched from the carrier, the
shuttle and pistons are stopped and the grab comes forward
and latches itself to the shuttle so it can all be brought back
to the battery, or starting position, for the next launch. Once
this is brought back, the crew has to determine if the catapult
is in the ready, standby, or shutdown mode. If the catapult is
in the ready mode, then the crew can proceed to moving on
to the next launch on schedule. While if the catapult is in the
standby mode, then there cannot be any launches off it for
12 hours and it must go through a full inspection, but this
only comes after a full day of operations [4]. Finally, the
catapult is determined to be in shutdown whenever it has to
go under maintenance or the carrier is in port [4]. There are a
lot factors and safety measures that the whole crew need to
account for before, during, and after every launch. For
example, they need to make sure that the wind is within the
right limits that have been set as well as making sure that
everyone is on the same page when it comes to the details on
every launch. In the next section, the discussion will be
based on why the steam-powered catapult is being replaced
by the Electromagnetic Aircraft Launch System and the
factors that caused this change.
WHY THE CHANGE?
Like so many other things in today’s world, the steam
powered catapult is on the verge of becoming yesterday’s
news as great strides are made by developers in the past
years several. The steam catapult is quickly becoming
hopelessly outdated and thus the Electromagnetic Aircraft
Launch System is being developed to fill the void and help
to eliminate the problems that will develop if the military
continues to use the steam catapult. The steam powered
catapult went through the same problems that another major
source of transportation that requires lots of steam. This
method of transportation is the steam-powered locomotives
[3]. These systems were similar in the numerous amounts of
assemblies it needed in order to function properly at the all
times such as valves, coils, and pipes, among others. These
assemblies gave the steam catapult problems since
everything needed to be under constant maintenance in order
for the catapult to remain in working order. In addition, the
steam catapult occupies a large amount of space on the
carrier, especially below the deck. This takes ups valuable
space that could be used for other means. Also, having the
extremely heavy catapult system so close to the top of the
carrier affects the ship's stability and ability to turn [3].
Another drawback to using a steam catapult is that once the
launch begins there is no way to make adjustments to the
launch, so if there is too much steam, the catapult could be
destroyed. If there is very little steam, the aircraft would just
tumble into the water, being unable to reach its necessary
takeoff speed [5]. Since today's aircraft are getting much
larger and heavier, they need a catapult or launch system that
can launch these aircraft at the necessary speeds in order for
them to get airborne. The EMALS is able to launch these
new mightier aircraft at their desired speeds in a short
amount of time and then be ready for the next launch in not
minutes but seconds after the launch. This system also has
the capabilities to make adjustments during the launch
process [5], allowing to the aircraft to have a much longer
life service, and crew members to have better control over
the launch, unlike the steam catapult. Not only are there
even more advantages for the new carriers to use the
Electromagnetic Aircraft Launch System but there are also
disadvantages that this launch system has and all this will be
discuss in the next sections.
ADVANTAGES
The EMALS offers several advantages over the past system.
The system itself is more powerful than the steam catapult,
which will allow it to handle to new aircraft (as new aircraft
are usually heavier than previous versions) [6]. The system
also has the ability to “reset” itself more quickly than the
steam version. This means the electromagnetic system can
be ready to launch another aircraft after a launch more
quickly than the previous system. This will allow the aircraft
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carriers to put more aircraft into the air in a smaller amount
of time. [1]
Another important aspect to the EMALS is the reduced
maintenance to the system and the aircraft that utilize the
system. It is designed to utilize “commercial off-the-shelf
components.” [2] This, along with the fact that the system is
made to be modular, meaning it is easy to disassemble or
remove parts of the system, makes maintenance on the
system simpler and less expensive. The system is also
designed to allow control of the speed of the motor as it
travels down the rail, which prevents excess speed, and in
turn strain, from being applied to the aircraft taking off. It
also makes the system more versatile, meaning it will have
the ability to launch both the heavier aircraft mentioned
earlier and the new unmanned drones being developed. The
future of carrier-borne aircraft will be reliant on this system,
as the steam catapult lacks the ability to launch the newer
aircraft being developed for the military.
begin with the energy brought from the prime energy
sources on board, which are the ship’s generators (the
energy there is produced by the ship’s nuclear reactor). This
energy then goes to the storage subsystem, which contains
the energy until it is needed in order to make a launch. When
it comes time to launch, the energy is distributed to the
launch motor, which is also subsystem. It is during this time
the on board systems have the ability to adjust the speed of
the catapult. Once a launch is complete, the shuttle that
carried the aircraft is returned to its original position,
utilizing the same principle that launched the shuttle down
the runway.
These subsystems are constructed using a “modular”
design, [2] meaning that the pieces that make up the system
can be easily removed for maintenance or replacement. This
will allow the subsystems to be easily placed into the carrier,
and greatly reduce maintenance time on the subsystems.
Also, it will allow engineers to easily upgrade the subsystem
as the years go on. In the following sections, the most
crucial subsystems and their roles in the launch process are
discussed in detail.
DISADVANTAGES
While the necessity for change is clear, the EMALS has its
challenges and disadvantages. Currently, its most pressing
issue is time. The system is currently being developed with
the funding from the federal government of the United
States, in order to have it implemented in the new class of
carriers being constructed. However, concerns have been
raised [1] about whether or not the system will be ready in
time to coincide with the carrier construction. If the
government sees the delays as being too expensive, the
funding will be cut and the carriers will be fitted with the old
steam catapult system. The point of no return will be before
it becomes expensive/nearly impossible to adjust the carriers
in order to fit the steam catapults [1]. If the project loses the
United States federal funding for any reason, it is highly
unlikely the development will continue, as it is mainly being
backed by, and is intertwined with the United States
government and military.
A more mechanical threat to the system involves the
fact that you have a large amount of electrical energy being
discharged near sensitive electronics. This electrical
interference is a very real threat to the electrical and
computer systems on board the sensitive “smart” weapons
(missiles and bombs that contain computerized guidance
systems) that the launch aircraft may be carrying [1]. Tests
will be done to see how the pulse from this system affects
each one of these weapons when carried by an aircraft
during launch. Predictions have been made that there will
not be an adverse effect on these systems. However, to fully
understand this threat, an understanding of what occurs
before, during, and after launch is necessary. The next few
sections explain in detail these events.
Energy Storage and Distribution
In order to deliver the several thousands of volts to the motor
in the two to three seconds it takes to launch the aircraft, the
ship requires a system that can store and release this energy
as quickly and efficiently as possible. The decision was
made to use electrical flywheels to store the energy.
Electrical energy from the ship’s main generators (which are
run by a nuclear reactor) is delivered into the large
flywheels. The flywheels then are accelerated to
approximately four thousand revolutions per minute [1]. The
flywheels maintain the rotational velocity, thereby storing
the necessary energy for a launch.
When a launch occurs, the system pulls the energy in
from the flywheel generator out to be used for the launch.
The kinetic energy of the flywheels is transformed into
electrical energy, which is passed to the motor. Since the
flywheels have lost energy, they have slowed down
considerably. In order to maintain the quick reset time, the
flywheels immediately begin accelerating back to the four
thousand rpm mark by taking more energy from the ship’s
generators [4].
Launch Motor
The launch motor is the most crucial and experimental
portion of the system. Its job is to accelerate aircraft that
weigh tens of thousands of kilograms down an
approximately one hundred and six meter runway to speeds
above 200 kilometers per hour in two to three seconds [6].
Then it must return to its original position and be ready to
repeat the process in less than forty-five seconds.
This whole process is made possible by the huge
amount of electrical energy delivered to the launch motor.
The energy is delivered to a system that is known as a
THE SYSTEM
The electromagnetic aircraft launch system can be broken
down into a number of subsystems [2]. These subsystems
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“linear motor.” Because of the large acceleration of a large
mass, a linear motor is similar to the workings of
experimental rail guns, which accelerate small projectiles to
enormous velocities. The linear motor system is so named
because instead of creating rotational motion like common
motors, it creates linear motion along its length. This motion
occurs because of “stators” that run the length of the runway.
There are two parallel rows of these stators side-by-side. In
between them is the mechanism that attaches to the aircraft.
This consists of a piece of aluminum and the “shuttle” that
attaches to the aircraft. When a launch occurs, the energy
from the generators is delivered to the stators on either side
of the shuttle at the beginning of the runway [1]. The electric
current creates a strong magnetic field, which in turn creates
and electric and magnetic field in the aluminum in between
the stators. This secures the shuttle inside a magnetic field.
However, the electrical energy is then passed to the stators
further and further down the runway. A magnetic “wave”
occurs, as each subsequent stator is charged by the electrical
energy. The wave carries the aluminum block and shuttle
down the runway, along with the aircraft that is attached to
the shuttle. The same method is used to stop and reset the
motor; the motor is stopped magnetically, and returned by
the same it was fired, simply by adjusting the amount and
frequency of the electricity being delivered to the stators on
either side of the shuttle [1]. This is a very important fact
about the EMALS, and a large reason why it is being
developed to replace steam; the system offers much more
control over the whole process than the steam catapult
system.
lighter aircraft will include the new unmanned aircraft being
developed, making for a more versatile navy.
Another reason this control is important is the fact
that it will reduce aircraft maintenance. The steam catapult,
being imprecise in its speed, could possibly expose aircraft
to unnecessary force during a launch. The electromagnetic
launch system’s precision will greatly reduce this risk,
meaning the wear and tear on carrier-borne, catapultlaunched aircraft will be reduced, saving crew time and
extending the life of the aircraft themselves [1].
TESTING
A critical part to the development of the Electromagnetic
Aircraft Launch System, as with any technology being
developed, is testing. Testing has been mentioned previously
in passing, however, it is worth mentioning that full scale
testing is happening. Most of it has occurred at the Lakehurst
Naval Air Station in Lakehurst, New Jersey. The first tests
occurred on a 1:12 scale model of the system inside a lab in
2004. After extensive testing with the scale model, it was
time to construct a full scale prototype. Instead of a carrier,
this catapult would be placed in a runway in Lakehurst [1].
This prototype would be built next to two old steam
catapults, which were used for experimenting with the steam
system over the past fifty years. The prototype was supposed
to be completed in 2007; however it was not operational
until 2010 [1]. The first tests involved simple weights being
moved down the runway by the EMALS. This was followed
by tests on the Navy’s F-18 Hornet aircraft. When aircraft
testing began, it was discovered the stators were not
transporting the shuttle smoothly down the runway. This
delayed testing for a few months until the stators were
energized correctly so that the shuttle traveled without
impedance down the runway. Once testing resumed, several
different aircraft were and are being tested, including new
aircraft such as the F-35 Lightning, the newest fighter/strike
aircraft being developed for the United States military.
These tests are not only done to see how well the
system launches aircraft. These tests include exposing the
system to the elements, especially saltwater, which can be
particularly hazardous if it enters the motor. Also, as
previously mentioned, the electromagnetic system involves
an incredibly strong electromagnetic wave near delicate
computer systems [1]. Therefore, tests are being done to see
how much electromagnetic interference, or EMI, occurs
when these systems are placed near the catapult.
Many more tests will be done before the system is
ready to be placed into the carriers. These tests will ensure
that, once installed in the carrier, the system will be
operational. However, as more delays occur, more problems
arise with integrating the system into these carriers. These
issues are discussed in detail in the next section.
Launch Control
The ability to finely-tune the launch sequence is a major
difference between the EMALS and the previous steam
catapult system. Once the button is pushed to initiate a steam
catapult launch, nothing can be done to control the speed at
which it accelerates. Also, the steam catapult is stopped after
launch by entering a water tank, whereby the resistance of
the water slows and stops the shuttle [1]. The
electromagnetic launch system offers a much more precise
launch sequence. This is due to the fact that the system
works by electricity instead of hydraulic pressure. The
amount of electrical energy being sent to the stators that
move the shuttle down the track can be precisely controlled,
along with which stators it the energy is delivered to (recall
the each row consists of several stators in a line). By
adjusting the speed at which the electricity moves down the
rows of stators, the speed of the shuttle can be adjusted.[3]
This portion of adjustment will be done by computers, as the
launch occurs much too quickly for a human to be able to
make proper adjustments. However, this will allow the crew
to pre-program the launch speed. This makes for a much
more versatile system than the steam catapult. It will allow
ships to launch much lighter aircraft, which will not need as
much force applied to them when being launched. These
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and will most likely not allow it to die easily. Although there
have been set backs, it appears that the newest fleet of super
carriers of the United States Navy will be utilizing the
Electromagnetic Aircraft Launch System to propel their
aircraft into the skies.
THE CARRIERS
After years of researching and testing, the Navy, as well as
the government, is eager to have the Electromagnetic
Aircraft Launch System finally ready to take that final
hurdle and be placed inside the new line carriers the military
is currently building. These carriers will be called the
Gerald Ford Class. They are being fitted with several brandnew systems including the EMALS [1]. The Navy has been
looking for a way to go to a completely electric based ship
for a long time and the EMALS replaces one of the few nonelectric systems (the steam catapult) that remain on today’s
carriers. However, as previously mentioned, there is a very
legitimate fear that the system will not be fully developed in
time to be fitted into the Ford carriers. Although the leaders
of the project insist it will work, politicians are worried that
if it does not work, or is not made to work in a reasonable
amount of time, the carrier will need to be fitted with steam
catapults before it becomes too costly to modify the carrier
to fit the steam system into place [1].
Although there are a few political challenges the
system’s integration faces, there’s also some mechanical
challenges. The system’s components, although smaller than
that of the steam catapult system, are still massive, making it
a feat to fit such a large system into the hull of an aircraft.
The runway is a similar size to that of the steam catapults; a
little over one hundred meters. However, the generator (the
system that stores and delivers the electrical energy to the
launch motor) is about 4 meters long and wide and 2 meters
tall, but weighs over 36,000 kilograms [6]. This system will
also be spinning at several thousand revolutions per minute,
and must be airtight to prevent air resistance from affecting
the flywheels [1]. Many considerations will have to be made
when fitting this unique system into the carrier. However,
the engineers are confident they will be able to successfully
integrate the system into the Ford carriers.
Another serious concern for integration of the
electromagnetic launch system into the carriers, as
mentioned previously, is the effect the elements will have on
the system once the carriers put to sea. The system will be
exposed to the saltwater of the sea, rain, wind, and extreme
temperatures. To prepare the system for this, several tests on
the ground-built prototype have been administered to
simulate these conditions. These tests have shown flaws,
which are being investigated [1].
The issue of air- and ground-crew adjustment to the
EMALS was a priority to the developers. The system was
created so that the launch process was very much similar to
that of the steam catapult system. This consideration will
reduce/eliminate the need to change the well-practiced
procedure that occurs on deck when an aircraft is launched.
This means there will not be much need for retraining of
current crews and pilots, which would have been a difficulty
that would arise from the transition [3].
While these challenges may seem a threat to the
project, the government has invested a lot into this program
BRINGING THE NAVY INTO THE FUTURE
Throughout the years, the Electromagnetic Aircraft Launch
System has gone from being an idea to going through a
series of tests as a scale model of 1:12 to being nearly ready
to be placed on the new fleet of aircraft carriers [3]. The
change from steam to electromagnetic catapult will be an
easy transition for the crew members since the military made
sure that the systems were similar in how they work [3]. The
EMALS will continue to do the same operations that the
steam-powered catapult did for the military all these years
but this system will without a question be less of a hassle
that the steam catapult gave the military during its final
years. That does not mean that the EMALS is without its
flaws. The system faces several challenges before it is put
into service on board the carriers of the world. No
technology, application, or idea will be perfect and the ones
that last a long time, such as the steam-powered catapult, are
the ones that find a way to overcome these challenges. As
stated before in the paper, the Electromagnetic Aircraft
Launch System will allow the carriers to hold more aircraft
if necessary to do the catapult being lighter than the steam
powered ones and occupying less space in the carrier. The
system can even launch more aircraft faster than the steam
catapults, making the carrier an even more formidable
military machine. The EMALS will give the United States
military (and those of other nations) a state-of-the-art system
that will be more efficient, more effective, and less
maintenance intensive than the previous system and will
allow naval air power to become an even more powerful tool
of the military.
REFERENCES
[1] (2009, July 16) “Oversight of the Electromagnetic Aircraft Launch
System
(EMALS)”
[Online]
Available:
http://www.gpo.gov/fdsys/pkg/CHRG-111hhrg52945/pdf/CHRG111hhrg52945.pdf
[2] “Electromagnetic Aircraft Launch System (EMALS).” General Atomics.
[Online]. Available: http://atg.ga.com/EM/defense/emals/index.php
[3] B. Schweber. (11 April 2002.) “Electronics poised to replace steampowered aircraft launch system.” EDN Magazine. [Online]. Available:
Engineering Villiage/Compendex.
[4] “Steam-Powered Catapults.” Global Security. [Online]. Available:
http://www.globalsecurity.org/military/library/policy/navy/nrtc/14310_ch4.
pdf
[5] T. Wright. (January 2007.) “How Things Work: Electomagnetic
Catapults.”
Air
&
Space
Magazine.
[Online].
Available:
http://www.airspacemag.com/military-aviation/electromagneticcatapults.html
[6] (2011, November 29) “EMALS: Electro-Magnetic Launch for Carriers”
Defense
Industry
Daily.
[Online]
.
Available:
http://www.defenseindustrydaily.com/EMALS-Electro-Magnetic-Launchfor-Carriers-05220/
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ADDITIONAL SOURCES
R. Bushway (2001, January 1) “Electromagnetic Aircraft Launch System
Development Considerations” IEEE Transactions on Magnetics [article]
H.D. Fair. (17 January 2005.) “Electromagnetic launch science and
technology in the United States enters a new era.” Magnetics. [Online].
Available: Engineering Village/Compendex
ACKNOWLEDGMENTS
I would like to thank the University of Pittsburgh for use of
its library, internet, and facilities. I would also like to
acknowledge Nancy Korbel for explaining the assignment
and answering my classmates’ questions thoroughly.
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