A human settlement on Mars is rapidly moving from science fiction to fact, with Elon Musk envisioning Battlestar Galactica-style fleets blasting off to the Red Planet in coming decades. That scenario is now one step closer, as engineers from NASA and the University of Michigan have successfully tested the X3, a thruster designed to get us to Mars. And it's broken several records in the process.
The X3 is one of three Mars engine prototypes currently in development. It is what's known as a Hall thruster, which uses electric and magnetic fields to ionize gases like xenon and expels the ions to produce thrust. The technique is much cleaner, safer and more fuel efficient than traditional chemical rockets, but the trade off is relatively low thrust and acceleration.
"Mars missions are just on the horizon, and we already know that Hall thrusters work well in space," says Alec Gallimore, lead engineer on the X3's development. "They can be optimized either for carrying equipment with minimal energy and propellant over the course of a year or so, or for speed — carrying the crew to Mars much more quickly."
In the recent tests, the X3 broke three different records previously set by other Hall thrusters, a very promising step towards manned Mars missions. Most importantly of course is thrust: the X3 blasted off with 5.4 newtons of force, smashing the previous record of 3.3 newtons. On top of that, the engine also managed an operating current of 250 amperes, which is more than double that of the previous record, and ran at 102 kilowatts of power, just edging out the previous record of 98 kW.
The tests were conducted over 25 days in July and August this year in a vacuum chamber at the NASA Glenn Research Center. Since the thruster gives off quite a bit of exhaust, which can then interfere with readings, this particular vacuum chamber is apparently the only one in the US that can properly test the X3. A specially-built stand was also needed to support its 500 lb (227 kg) weight.
Before the thruster can be fired up, it takes about 20 hours to pump the air out of the chamber to achieve a vacuum similar to that in space. The tests are slow-going: if anything goes wrong, air has to be pumped back in gradually before any repairs can be made, and then it takes another 20 hours to get it back to a vacuum to resume testing.
While these tests were conducted using separate power supplies, the X3 will eventually have its own unit, currently being developed by Aerojet Rocketdyne. Once this is up and running, further tests are set to take place at the same facility in the first half of 2018, with the team aiming to run the thruster for 100 hours.
Source: University of Michigan
