Technology May Catch Up
Building a first stage of a future launch vehicle with an electromagnetic catapult is an idea that has merit and combines technologies that are already proven, said Leo Holland, director of the Special Projects office in the Advanced Technologies group for General Atomics of San Diego.
General Atomics is a key partner with Dryden in the development of a Highly Reliable Reusable Launch System, which is currently being studied as part of NASA's Innovative Partnerships Program.
The concept of an electromagnetic launcher is one that he has been interested in and working toward for more than 25 years, said Holland, who has a doctorate in electrical engineering. The development of magnetic levitation systems in the 1990s was used to power a train by essentially pulling it along with magnetic waves generated from a track that suspended the vehicle several inches in the air.
The technology is continuing to mature. In fact, General Atomics is under contract to the U.S. Navy to install electromagnetic aircraft launchers on the next new aircraft carrier, he added.
"We are building experience and a technology base to move forward. The Navy program is giving us, in the lower-speed range, a very advanced system and everything you would need to build a launch-assist system. Answering the remaining technical questions will lead to higher speeds," Holland explained.
The technology used to build electromagnetic launchers also is transferable to more everyday uses in items such as inverters for trucks and wind turbines. Each experience moves the technology a step closer, he added.
In its partnership with Dryden, General Atomics staff provides instrumentation for engine hardware provided by the center and runs tests prior to hooking it up to the company's inverter. The next step will be to run one motor with the inverter to test its power and then look for funding to add more of the four motors available for experimentation, Holland said.
"When we hook this up to an inverter, which basically creates three-phase voltage and current that is variable, I can change the frequency and the voltage level and therefore the current that's going into it. By driving a fairly high current through these windings [wiring], I can create a magnetic field that goes through that aluminum plate and moves it," he said.
The principles of this concept can be demonstrated by moving a common rare-earth magnet near a quarter-inch conducting aluminum or copper metal plate. The movement of the magnet will create opposing currents in the metal plate and those opposing currents will cause the plate to be pulled along. In a similar manner, the inverter produces a magnetic field that is moving and the opposing currents will pull the aluminum plate along. In a launch system, the plate is connected to a vehicle, much as the technology is currently used in roller coasters.
"IPP is a good way to highlight technologies and get them in front of people to see if you can get a program going," he said.
Time - and development dollars - will determine how the idea fits in with launch vehicles of the future.