A thruster that's being developed for a future NASA mission to Mars broke several records during recent tests, suggesting that the technology is on track to take humans to the Red Planet within the next 20 years, project team members said.The X3 thruster, which was designed by researchers at the University of Michigan in cooperation with NASA and the U.S. Air Force, is a Hall thruster — a system that propels spacecraft by accelerating a stream of electrically charged atoms, known as ions. In the recent demonstration conducted at NASA's Glenn Research Center in Ohio, the X3 broke records for the maximum power output, thrust and operating current achieved by a Hall thruster to date, according to the research team at the University of Michigan and representatives from NASA."We have shown that X3 can operate at over 100 kW of power," said Alec Gallimore, who is leading the project, in an interview with Space.com. "It operated at a huge range of power from 5 kW to 102 kW, with electrical current of up to 260 amperes. It generated 5.4 Newtons of thrust, which is the highest level of thrust achieved by any plasma thruster to date," added Gallimore, who is dean of engineering at the University of Michigan. The previous record was 3.3 Newtons, according to the school.
https://www.space.com/38444-mars-thruster-design-breaks-records.html
Quote from: Star One on 10/13/2017 08:09 pmhttps://www.space.com/38444-mars-thruster-design-breaks-records.htmlThat's impressive as a single unit. Previously people have been talking about clusters of ion thrusters to get this, and that can cause problems. On a 400 tonne spacecraft that 5.4N gives an acceleration of about 1.37 micro g. The problem is the 100Kw needed to power the thing.
I think the thrusters should use argon. Mars' atmosphere is about 3% argon. It is also more plentiful on earth. It may not give as high a thrust or it may be a little more bulky than xenon, but a large spacecraft that would fly between earth and Mars could have a pre launched lander pulling argon out of the atmosphere, then launch it up to dock with an incoming ship from earth to refuel for the crew return to earth. If a lot of travel is to eventually be done between earth and Mars, argon may be the way to go. One could use Vasmr thrusters that can use almost any gas, even oxygen to ionize. They take more power and a larger amount of propellant, but, still less mass than chemical brute force.
The problem is the 100Kw needed to power the thing.
Quote from: Star One on 10/13/2017 08:09 pmhttps://www.space.com/38444-mars-thruster-design-breaks-records.htmlThat's impressive as a single unit. Previously people have been talking about clusters of ion thrusters to get this, and that can cause problems. On a 400 tonne spacecraft that 5.4N gives an acceleration of about 1.37 micro g. That's roughly a speed increase of 1 m/s every 74 seconds. The problem is the 100Kw needed to power the thing.
You lost a kilo there somewhere. Either 400 kg craft, or 74,000 sec.
Not really, 100kW arrays are on the radar, with specific power of 150w/kg.
It's 5.4N for 100KW, which is more than double of the 5N for 200KW for VASIMR.
Nuclear power?
Quote from: savuporo on 10/14/2017 02:23 amNot really, 100kW arrays are on the radar, with specific power of 150w/kg.The ISS array is 200Kw but it's also pretty heavy. If that number's real then you have an array below a tonne. That suggests it could still generate significant power even in the outer planets, although solar levels at 30AU are 1/900 that at Earth.
Why would they not quote the Isp?Cheers, Martin
Quote from: MP99 on 10/14/2017 07:10 pmWhy would they not quote the Isp?Cheers, Martin An excellent question.Searching for that value leads to Edward Florenz's 2014 thesis on the X-3 100 kW 5 N Hall Thruster.Skimming the 169 (!) pages failed to produce that value. It is attached. Edit: Figures 6.1 thru 6.8 on page 99-105 show "anode Isp" of ~2370 sec. (The attached image has a purple and yellow circle for the approximate point on the graph)Figure 1.1 shows historical values of IsP vs thrust for all sorts of engines. Hall thrusters top out around 3000 sec, although the highest value for a flight system was ~2000 sec. The Isp for X-3 falls between these values.
Quote from: envy887 on 10/14/2017 02:50 amYou lost a kilo there somewhere. Either 400 kg craft, or 74,000 sec.Ooops. I should have realized that was too good to be true. So 1 m/s faster about every 20 hours. The downside for ITS would be you've basically added 50% to the power requirement
I made a model of one of an advanced ion engine ship with X3 thrusters. It uses mega-rosa arrays.(image)
By the way, one of the ADVANTAGES of Hall Effect thrusters are their lower Isp.Low Isp means you can get more thrust out of the same power, meaning your burn can be much shorter for the same impulse.Too high of an Isp is actually very suboptimal.