By Geoff Fein
The Navy is confident the Electro Magnetic Aircraft Launch System (EMALS) being designed for CVN-21 will help reduce manning on carriers, increase aircraft sortie rates, and provide a system that will be capable of launching the variety of aircraft planned for the future.
Topside, not much will change with the addition of EMALS. Aircraft will continue to be hooked up to a shuttle, then to the catapult, and shot down the deck to get up to speed for launch.
Catapult operators launching aircraft will probably not notice much of a difference, either. There will be some new displays because they will be looking at different information now, Capt. Stephen Rorke, program manager for aircraft launch and recovery equipment, told Defense Daily in a recent interview.
Operators will still have to worry about the weights of the aircraft and the settings. But now, instead of setting steam selector valve settings based on the weight of the aircraft, they will tell the computer how much power is needed, what the end speed is, and the system has the ability to compensate for all kinds of things to make sure that aircraft achieves that end speed so that it launches and flies safely, he said.
“All the magic, what is going on behind the curtain, is all down below [deck],” Rorke said. “Everything is different. It is not a kind of a band-aid or retrofit on the steam [catapult].”
The basic design is made up of multiple subsystems, he said. “But if you really get right down to it, there is an energy storage subsystem and then there is the launch motor to actually get the aircraft off.”
“There are other subsystems to support all that but if you get down to the basics we store the energy, in this case in rotating machines,” Rorke explained, rather than in steam accumulators, which is how a steam catapult system stores power.
With EMALS, when an operator pushes the button to initiate the launch sequence, the energy from those machines is sent through a distribution network and formed into the correct wave forms to feed the linear motor, Rorke added. “Basically this is an electromagnetic driven linear launch motor.”
The reason the Navy transitioned to EMALS in CVN-21 was to change a lot of the technology on the ship and bring it up to the latest standards, with the idea of making it even simpler, more reliable, with less impact to the ship, Rorke said.
“One of the advantages of this, we no longer have to take steam from the engineering places all the way up to the topside to launch the aircraft. All we have to do is move electricity around,” he said.
Another advantage of EMALS is that it’s a lot more flexible in adapting to the needs of the current aircraft plus what the Navy is projecting in the future, in particular the F-35 Joint Strike Fighter (JSF) and Unmanned Combat Air Systems (UCAS), Rorke added.
“If you think about the fact we are building this carrier that will deliver in 2015, with a 50-year lifecycle, what are we going to be seeing out there in 2085? This is the first of the new class and so the intent is we will build a few more of these things. So if you think about it, this system is going to be out there for a long time 75 to 100 years into the future,” he said “So what is going to be out there in the future?”
EMALS can be tailored to the launch forces better than could be done with steam catapults, Rorke said.
“There is a lot of technology in steam…how the launch valve opens, how much energy is put into the cylinders…but there is only a limit to what you can do without making that system extremely overly complicated, more complex, and therefore more prone to having a failure mode,” he added. “The idea with [EMALS] is that I have inherent flexibility built into this thing. I can tailor my launch forces to the aircraft at hand.”
Moving toward an electro magnetic catapult system will also impact operational capability, Rorke said.
One condition of EMALS is that it had to demonstrate that its availability was at least as good, if not better, than steam catapults, he noted. “That is what we are designing for.”
The mean time between failures, the meantime between repairs, are better than steam, Rorke said.
“All of those are design parameters that have gone into this whole system.”
The Navy is designing CVN-21 to have a crew size that will be approximately 1,200 sailors fewer than a Nimitz-class carrier (Defense Daily, July 10, 2007). In order to attain a smaller crew size, many of the new systems must be able to operate without human intervention. “So the ship itself has a lot of smart technologies being put into it. EMALS is one of them.”
For EMALS to be operated with fewer people, a number of things have to be done, he added.
For example, the system needs to be able to monitor itself and tell maintainers what’s wrong, and point them in the right direction to make repairs.
“Because I have better availability, because I can repair it faster, because the diagnostic system that is being built into it will tell me the status, I can get more sorties per day off the ship. That was one of those other design considerations in the CVN-21 program–increase the sortie generation rate,” Rorke said.
EMALS will first be installed and used on the USS Gerald Ford (CVN-78). The system will not be retrofitted on to other carriers, Rorke noted.
The first delivery of subsystems to the Ford will occur in 2011, Rorke said. Because EMALS is part of the ship, its Initial Operational Capability coincides with the Ford‘s, which is scheduled to be delivered in the 2015 time frame, he added.
Until then, EMALS will undergo years of testing at Naval Air Engineering Station Lakehurst, N.J.
Lakehurst is the center of excellence for aircraft launch and recovery equipment, Rorke said.
“It has been and remains the hub of engineering for aircraft launch and recovery equipment. They have test tracks for arresting gear testing, they have steam catapults on the test runway, and now on the opposite side of the runway they have EMALS going in,” he said.
About four years ago, the Navy held a competition for an electromagnetic launch system. The competitors had to build a full-scale but short length system and demonstrate it using components that were not necessarily militarized or that could fit into a ship, Rorke said. Based on the Preliminary Design System, the Navy awarded General Atomics Aeronautical Systems the EMALS contract. “Their design is essentially what we are building now for full scale.”
Although the catapult track itself was about half the length of what would go on a carrier’s deck and the power available with commercial generators was not what the Navy was going to use on the ship, nonetheless General Atomics was able to demonstrate within the length of track they built that they could get weights up to 100,000 pounds accelerated and they could get dead loads or lightweights up to 180 knots, Rorke said.
Since then the Navy has conducted thousands of shots using dead loads and lightweight loads, at various speeds, to show it can be done.
“That design is what we have spent the last couple of years refining and shipboard ‘navalizing’ it, if you will, making it fit within the available spaces, finalizing all the component selections, scaling it up to the catapult track on the ship, and probably the more interesting of our challenging pieces was the generator itself,” Rorke added.
The ship set will contain 12 generators in a shared arrangement to drive all the catapults, he said.
“That generator system, for its power and size, is a remarkable piece of equipment. Probably one of the most power dense generators ever built,” Rorke said. “That is a big piece, the heart of this…storing that energy so they can release [it] in the two-and-a-half seconds it takes to do a launch. Taking that much energy up to 102 megajoules of energy to get the aircraft off to the highest speed possible. It’s pretty phenomenal.”
Now the plan is to test the system at Lakehurst and make it compatible for the aircraft that currently exist in the Navy’s inventory, he added.
One of the biggest tasks in the test program will be to verify all the models, make sure the assumptions of the design are valid and tailor the profiles–start building the first launch bulletins for the aircraft, Rorke said.
“So part of the full-scale testing up at Lakehurst will be to do live launching in ’09,” he added.