The original Design And History of The FireCat Internal Combustion Catapult
BuAer , in the late 1940"s to early 1950's decided that catapult launched Naval aircraft were becoming heavier and were reaching the upper limits of the current H8 hydraulic catapults which were driven by a dual cross-head hydraulic launch motor . BuAer decided to investigate 3 new technologies to address the increasing demands on the existing catapult technology.
- The first was an electromagnetic catapult called the Electropult, of which two were designed and built by Westinghouse. After two were built and tested, BUAer chose not to pursue this technology.
- The second was the steam catapult. This had a number of drawbacks in that that it was very heavy, space intensive, complex and required significant personnel to maintain and operate along with subjecting the launched aircraft to a heavy shock. The significant and varying additional power drawn from the reactors initial during flight operations.
- Required over 1,300 gallons of distilled water per launch.
- Some components such as the water brake were somewhat fragile.
- It could be seen as a medium range fix to launch the current and some-what heavier aircraft,especially with the projected fuel and weapons load-out. This catapult was seen to be adequate but with considerable drawbacks.
The third was the Internal Combustion catapult which was designed and built by Reaction Motors of New Jersey in 1957 to 1959. and and was installed at the cataput test facility at Naval Air Warfare Center (PMA 251) in Lakehurst ,New Jersey. Here the internal combustion catapult was tested and qualified for installation aboard the USS Enterprise.
. From Bob Hollands web site,
Planes that require flying speed are launched
from an aircraft carrier by a catapult using high pressure steam. The problems
with this are:
§ Fresh water is needed to generate the steam
§ As the catapult moves the pressure drops. The
initial "kick" is very high and then the acceleration drops off. The
plane and pilot may be subjected to as much as 5G's at the start to get enough
speed to get airborne.
This is why aircraft carriers always turn into
the wind and increase speed to launch planes. To conserve fresh water and
reduce stress to pilots and planes.
Reaction Motors designed a system with a rocket
engine that burned jet fuel and added salt water to generate the steam. Both
jet fuel and salt water are readily available at sea. The engine produced
constant pressure throughout the launch and a plane could be launched with as
little as 2G's of constant excelleration.
This means that aircraft could be launched with
less stress and even at flying speed downwind.
Right about now you are probably wondering
"if this thing was so great then why are we still using steam
catapults?". The answer is very simple.
In the latter stage of the project we turned the
catapult operations over to Navy personnel. The arrangement was that if there
were any problems the Navy personel could go home while we fixed it.
Yup, we had problems. Leaks, cut wires, loose
fittings, water in the hydraulics, you name it. Anything the sailors could think
of so they could get off work.
The boys in Washington looked at the numbers (of sailor induced failures) and
in their infinite wisdom decided that the system was too unreliable.
I worked on both catapult systems and believe
me, the Reaction Motors system was far superior, less expensive and more
The FIRECAT catapult takes the 1950's internal combustion catapult and incorporates 2016 technology.. This includes, using oxygen enriched air, modern combustion technology and sensor/control technology to make this modern internal combustion catapult superior to either the C13 steam catapult or EMALS.
One of the significant additions to the FIRECAT, use of oxygen enriched air rather than compressed air as air is 80 percent nitrogen which is inert.
rationale for using oxygen enriched air rather than atmospheric air is that
atmospheric air is comprised of approximately 80% inert nitrogen gas and I saw no
reason for expending the effort to compress the inert nitrogen gas, store it
and then introduce it into the area where combustion was taking place as
nitrogen would dilute the available oxygen and not support the desired non-turbulent combustion By removing the nitrogen, the ancillary equipment is reduced in size, the combustor is
greatly simplified and management of the flame zone for producing launch gasses
is also greatly simplified so that the combustor will be a commercially
available combustor such as is
used for turbine driven power generation by the public utilities.
There are several technical approaches to the task. These vary
according to which evolutionary version of the catapult we are referring to:
The First, the one described in my
catapult patent, 6,007,022, used HAN, Hydroxyl Ammonium Nitrate as the oxidizer, and TEAN, Tetra Ethyl Ammonium
Nitrate with the chemical formula Molecular Formula C8H20NNO3 provides the carbons and hydrogens to act as a fuel.
Hydroxyl Ammonium Nitrate (HAN) is the oxidizer with
the chemical formula NH3OHNO3. The mixed fuel and oxidizer compounds are difficult to lignite as they are in a
water solution. This took a lot of my
and Thiokol’s efforts to get reliable and repeatable ignition. We were successful and demonstrated this to
NAVAIR. Other than sensitivity to
breakdown of the passivity layer of the stainless steel tankage that they are
stowed in, there is no real problem except that the logistics effort to add two
additional fluid streams to the carrier along with the segregated tankage,
pumps and valves for stowage aboard. Transport
by the fuel ships gets a little difficult as all of the fuel tankers have to be
modified with stainless steel tank cladding and stainless steel piping, pumps
and hardware to carry these fluids and deliver them via UNREP to the carrier.
Why did I choose to use such a difficult fuel-oxidizer to drive the catapult?
The reason was that my management had fallen in love with Lockheed
Martin due to some clever LM marketing and LM wanted the same fuel system used
in the catapult as was used in their Crusader field artillery piece. LM detached Dr. John Irizarry temporarily to
work with me and Indian Head Naval Ordinance Lab to develop this. After LM tried to take over the program by
asking our teaam members to join a separate team with LM as the prime and doing briefings all over Washington using my PowerPoint slides with their logo
attached and references to Newport News Shipbuilding and me, excised, I managed to end the relationship with
LM and establish one with Thiokol (now ATK).
Unfortunately, given the greatly increased electrical generating capacity of the new CVANs starting with CVAN 77, there was sufficient electrical power to operate an EMALS catapult. Given this and the representation by General Atomics that their EMALS launcher. was identical to an unrolled electrical motor and little development was required for the launch engine and the opposed alternator energy storage module.. In addition, NASA, was interested in electromagnetic launch and offered to co-fund the EMALS program and help develop it. This resulted in the Advanced Technology Launcher competition being terminated. This, in addition to optimistic marketing by General Atomics, killed my competing $35
million (1999 dollars) ICCALS (FIRECAT) program with Naval Air Warfare System. Note that this was for design, build and initial test of FIRECAT compared to EMALS which is well over two billlion for a catapult which is one quarter the power of FIRECAT, a million pounds lighter, and a tremendous consumer of space within the ship to accommodate the 12 each 80,000 pound motor generators. The EMALS ship does not have sufficient berthing space for the crew, due to the 12 large compartments required by the EMALS energy storage modules and other equipment
second was a jet fuel and
oxygen enriched air system as an evolution of the C14 catapult of the 1950s.
Originally, I looked at
liquid oxygen as an oxidizer for the ICCALS jet fuel combustor. The US Navy had taken on the task of risk
reduction throughout the ship. One of
the areas that they had addressed was the use of a liquid oxygen plant
aboard. In 1999, I was told most
emphatically by Adm Mahr that a liquid oxygen generation plant would not be
allowed on CVN78, the first EMALS ship.
Oddly, in checking recently, I find that there is going to be a liquid
oxygen plant aboard CVN78 after all, but not intended or
sized for supporting an internal combustion catapult. Anyway, the net result is that FIRECAT was not
considered for CVN78.
The third iteration of the ICCALS
as it evolved away from the catapult described in the patent was something that
I undertook in the late 2000s during the period of time when the EMALS
development had hit a rocky patch and there was concern that the CVN78 ship
would be delivered without a catapult.
It had appeared to me that, given the widespread concern about EMALS at
the time with the energy storage system failing, other problems emerging and
the schedule for development slipping more than a year, it would be an
intelligent thing to do to invest some money into the FIRECAT technology (which
fits into the same troughs as EMALS) as a fall-back option in case there was
not a successful conclusion to the EMALS development and test program.
I still feel that there is an serious risk in not exploring this FIRECAT option as there is recognized risk caused by EMALS not only to the ship cost and schedule, but also the ability to consistently perform its mission... Therefore I picked up where I had left off
with FIRECAT development to provide an insurance technology so that the CVN78
would have a catapult, no matter what happened to the EMALS system for the ship. Also, I was investigating a backfit of IFIRECAT
to the Nimitz class carriers to give them all of the benefits of the catapult
capabilities advertised for EMALS and more, as the FIRECAT catapult is
fundamentally a more capable, more reliable, more powerful and more versatile system than
Time and technology having
advanced, I became aware of a new technology called Pressure Swing Adsorption
(PSA) and how it could benefit the FIRECAT by providing what in essence was the
same quality of oxygen that I might get from a liquid oxygen plant without the
risk of cryogenic fluid generation, storage, handling and delivery to the
combustion zone of the FIRECAT combustor.
In essence, this iteration is substituting gaseous oxygen produced by
the PSA process in place of liquid oxygen,
The Oxygen Generating Pressure
Swing Adsorption system is composed of two pressure vessels containing zeolite fibers and a source of
compressed air. This is absolutely off
the shelf technology as described below from Mahler AGS, among others. There are a number of sources for this
hardware and it would not be at all difficult to install it aboard a smaller aircraft carrier such as the Queen
Elizabeth. The thing to remember is that
the maximum need of delivered oxygen is based upon the amount of jet fuel (JP5)
needed for a maximum F18 launch weight of 70,000 lbs which requires 6.5 gallons of JP5 and a roughly 12 pounds
of oxygen which will weigh less than 100 pounds. Thus a mission that requires 50 launches per
day will use 5,000 pounds of oxygen per day. Continuing that line of reasoning, a mission requiring the launch of a 100 pound UAV would readily be accomplishable.
The OXYSWING system below
can deliver up to 200 tons per day, so a significantly (98% downsized) downsized
system should be perfectly adequate to supply all of the non-cryogenic oxygen
required by the FIRECAT Internal Combustion Catapult. in supporting large numbers of launches per day and would not be a limiting factor in any way.
Mahler AGS has over 30 years of experience
and know-how in the design and manufacturing of Pressure Swing Adsorption (PSA) plants. We are in the
forefront of this technology and have the flexibility to provide the right
process, be it PSA, Vacuum Swing Adsorption (VSA), or a combination
of both (VPSA) for the required application.
The OXYSWING® systems are designed to be highly efficient to provide an
economical supply option for the customer and they are able to cover a demand
up to 200 tons per day of oxygen with high reliability, rapid on-line time, full
automation and minimal space requirements aboard ship.
The fourth ICCALS iteration
is based upon the GE 6000 marine propulsion turbine which has a pressure gain
at the HP compressor of 29 and delivers an inlet gas to the combustion part of
the turbine of 14.2 PSI X 29 or 411.7
PSI available as a high pressure bleed to supply the catapult.
The launch pressure
required to deliver a 3G launch to a 70,000 pound loaded plane is 210,000
pounds. Given a catapult cylinder of 18”
inner diameter, that provides a radius of 9” and an area of 9 X 9 X 3.1416 = 254.5 sq
inches. At two tubes, that totals 509 sq
inches. 210,000 / 509 sq inches =412.5 PSI.
This strikes me as an amazing coincidence, given the 411.7
PSI launch pressure available from the GE 6000 as a high pressure bleed is an ideal match for the C13-1 catapult requirement.
This eliminates all of the requirements for
combustors, JP5, water and ancillary hardware, providing the simplest possible
system for launching planes as the only addition would be a throttling valve
that would allow the launch of the full range of manned and unmanned air
Thus, bear this in mind. No
current or planned catapult can maintain the same launch pressure over the
length of the catapult stroke except for the FIRECAT catapult, which allows a
higher end-of-stroke launch speed at a lower initial launch acceleration with large benefits to the
airframes of the launched aircraft as far as reduction in severity of peak launch induced stresses and in reduction in frequency of repair
and extension of the overall life span of the aircraft.
For steam catapults,
the steam pressure in the accumulator falls sharply as the swept volume behind the
catapult pistons increases during the launch, starting off as a 5+ gravity
acceleration and ending at less than one gravity acceleration by the end of the
EMALS experiences much the
same fall-off of launch pressure/energy as the rotational speed of each of the 3 per
catapult launch energy storage (huge)motor generators is dragged down by
switching them from motors to generators and rapidly extracting the mechanical
rotational energy of the motor generator armatures as electrical launch energy. (3 megawatts per launch)
The motor generators need to be switched back to motor function and driven back up to speed using ship reactor power before they
have sufficient launch energy stored to accomplish another launch. This will
take some time. The rapid deceleration
and re-acceleration of the motor generator armatures will most likely result in frequent
servicing of the motor generators which adds to the lifetime cost of the EMALS system.
The FIRECAT system consists of the tried and true C13-1 or C13-2catapult launch
engine found on the USS Enterprise and early Nimitz class carriers with its
power cylinders, pistons, troughs and trough covers with the attendant shuttle assembly
and waterbrake (which is an opportunity for improvement later). Additionally, the combustor is a direct copy
or purchase of the combustors that public utility electrical generation facilities use and
which operate for years with no maintenance required. The oxygen, JP5 and water sources are
standard pressurized accumulator delivery systems with computer driven throttling
valves. The digital control systems may
be adapted from public utility systems which have to deal with varying loads as
they operate. One of the advantage of
using an existing design is that existing surplus equipment can be utilized, such as the catapult launch engines aboard the the USS Enterprise. The catapult systems aboard these ships are
maintained in tip-top shape as the life of the pilot and safety of the plane
being launched depend upon the material condition of the catapult. The gentleman who owns the catapult systems
for NAVSEA assures me that the catapults on the Enterprise would be like-new
and it would be a very smart thing to do to capture the Enterprise catapults
for ships such as the HMS Queen Elizabeth and the Prince of Wales.
The ICCALS catapult meets future Navy needs for carrier launched UAVs and are well described by the below sites. All fall under the simplified set of requirements of full closed loop control of the launch event, minimizing peak to mean acceleration at the start of the launch event and the ability to provide the correct launch energy to a wide range of launch vehicles, from the lightest to the heaviest with considerable capability to upgrade the delivered power while imposing the least possible stress on the airframe of the launched vehicles.
It is the intent of the FIRECAT technology upgrade of the C13 steam catapults to give the existing catapults a greatly expanded range of function and capability, that meets or far exceeds the capability of any current or planned catapult including EMALS.at a significant reduction in:
- required manpower and maintenance,
- volume requirement within the ship,
- weight of the system, particularly topside weight,
- cost of development,
- peak to mean acceleration,
- installed cost.
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