June 5, 2008 -- Engines explode all the time. They usually have fuel in them when they do though.
During what was essentially a wind-tunnel test of an experimental satellite propulsion system that would use Earth's magnetic field instead of chemical propellants to zip around our planet, the test satellite exploded, sending hot chunks of metal flying.
Despite the explosion, the NASA-funded device has since been improved and represents a new breed of satellites that could alter satellite physics and economies. The idea is to create millions of cheap satellites the size of corn kernels (and smaller) to augment today's multi-million dollar, car-sized satellite armada.
"The test wasn't a catastrophic failure," said Mason Peck, a scientist at Cornell University and coauthor of a study on the satellite that appeared recently on arXiv.org.
Since that recent trial, Peck and his colleagues at the University of Michigan and State University of New York, Binghamton, have successfully tested (but not yet published) their propulsion system, which could speed satellites along at more than four and a half miles a second.
Peck and his colleagues argue this new kind of mini device could make satellite missions more affordable and feasible.
"You could launch a million of these things and if only one of them reached the goal the mission would be a success," said Peck.
The propellant-less satellite idea works a lot like a TV. A 'gun' at the back of the TV shoots out negatively charged electrons. As they speed towards the viewer, a magnet changes their direction.
On a planetary scale, the electron would be the satellite zooming around the magnet, in this case the Earth. As the satellite zooms around the spinning Earth it would experience a force (known as the Lorentz force) pushing it at an angle perpendicular to its direction. The satellite would steal a tiny bit of the Earth's energy to propel it forward.
"The Earth would essentially push the satellite along," said Peck.
Other designs using the same principle, including the Electro Dynamic Tether, have been successfully used in orbit. One difference between the EDT and the new system is that the tether has to be aligned in a specific direction, where the new satellites wouldn't need to be.
To test their idea, the researchers put a test satellite into a vacuum chamber at SUNY Binghamton and then shot charged ions at the spacecraft, simulating conditions in outer space.
Just because it doesn't use chemical propellants doesn't mean the satellite is fuel-less. Radioactive material, such as Americium 241, which emits charged particles, or electricity from solar panels or a battery, would be necessary to maintain the satellite's charge.
As the charged ions flowed around the test satellite, its charged particles were whipped off "like wet paint off an aircraft," said Peck.
Meanwhile different electrical charges built up on the two metals used in the satellite, eventually causing an electrical arc to blow off the solder.
More recent tests of solder-less satellites at the University of Michigan have been successful, said Peck.
Not everyone thinks the new propulsion system will fly though.
"I don't think this is going to make satellite designers very excited," said Manuel Martinez-Sanchez, Director of the Space Propulsion Laboratory of the Massachusetts Institute of Technology.
Such a technology could be useful in changing satellite orbit, which doesn't require an energy change, said Martinez-Sanchez, but not for propelling a satellite.
The only real test of a tiny satellite magnetic propulsion system will be an actual flight in outer space. Peck and his colleagues hope to perform a Sputnik-style test in a few years, where a small radio beep from space would signal success.
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