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#1
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Running multiple HET in parallel?
Are there any known issues with running multiple HET
(Hall Effect Thruster) in parallel to get increased performance? Is it being already used somewhere? -- Sander +++ Out of cheese error +++ |
#2
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Sander Vesik wrote:
Are there any known issues with running multiple HET (Hall Effect Thruster) in parallel to get increased performance? Is it being already used somewhere? As long as you seperate them enough, sure. |
#3
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On Wed, 9 Feb 2005 07:46:49 +0000 (UTC)
Sander Vesik wrote: Are there any known issues with running multiple HET (Hall Effect Thruster) in parallel to get increased performance? Is it being already used somewhere? Just the energy cost, I think. It would be interesting to work out how much of a spacecraft you would have with a couple of submarine style fission reactors and as many ion or hall thrusters as you had power for. Given the lack of enthusiasm for this approach I can only assume that it doesn't deliver transit times short enough to be safe for humans. -- Michael Smith Network Applications www.netapps.com.au | +61 (0) 416 062 898 Web Hosting | Internet Services |
#4
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Sander Vesik :
Are there any known issues with running multiple HET (Hall Effect Thruster) in parallel to get increased performance? Is it being already used somewhere? More thrusters, more power needed. E.C.P. -- I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos, SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to the time? http://webhome.idirect.com/~earlcp |
#5
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Sander Vesik wrote:
Are there any known issues with running multiple HET (Hall Effect Thruster) in parallel to get increased performance? Is it being already used somewhere? I've seen it done, and it seems to work just fine. Ground tests only, so far. And I happen to have the paper on my desk. "The Air Force Clustered Hall Thruster Program", W.A. Hargus Jr and G. Reed, AIAA-2002-3678, 38th AIAA Joint Propulsion Conference, 2002 -- *John Schilling * "Anything worth doing, * *Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" * *Chief Scientist & General Partner * -13th Rule of Acquisition * *White Elephant Research, LLC * "There is no substitute * * for success" * *661-718-0955 or 661-275-6795 * -58th Rule of Acquisition * |
#6
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Michael Smith wrote:
It would be interesting to work out how much of a spacecraft you would have with a couple of submarine style fission reactors and as many ion or hall thrusters as you had power for. Given the lack of enthusiasm for this approach I can only assume that it doesn't deliver transit times short enough to be safe for humans. It would be interesting to know if there is currently any propulsion approach available that would allow significantly faster than Hohmann trips for humans to other planets/moons/major asteroids. (Our moon excepted, of course.) "Currently available" can be interpreted to mean "available by 2025 at a development + procurement cost of no more than $10G in 2004 dollars per year between now and then." Equally intresting would be to know about the technology for life support systems that would reasonably reliably sustain a half-dozen people for two or more years in space without help from Earth. |
#7
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In article .com,
Allen Thomson wrote: It would be interesting to know if there is currently any propulsion approach available that would allow significantly faster than Hohmann trips for humans to other planets/moons/major asteroids... "Currently available" can be interpreted to mean "available by 2025 at a development + procurement cost of no more than $10G in 2004 dollars per year between now and then." Yes: orbital assembly/fueling will let you do faster-than-Hohmann trips for small expeditions with chemical propulsion. You need an orbital fuel depot, and lots of fuel launches, but the former is fairly straightforward if you don't insist on using LH2, and the latter provides high flight rates for RLVs and a large competitive market for launchers of all sorts. Double yes: if you're willing to spend a bunch on R&D to reduce launch rates -- which is probably a bad deal, but is undeniably attractive to organizations that specialize in R&D -- solid-core nuclear rockets can considerably improve the picture, speeding things up further or permitting larger expeditions or both. Rover/NERVA solved most of the major technical problems of a first-cut version in the 60s, and demonstrated that a fast-paced program could improve the state of the art remarkably quickly in this area. You can start with NERVA derivatives, and pursue more ambitious designs in parallel with the first expeditions. The one big hassle is low-emissions test facilities, and it's one that should yield quickly to substantial amounts of money -- no breakthroughs are required. Liquid-core or nuclear-lightbulb is substantially better, and gas-core is much better, although they are longer-term options with significant development issues. Equally intresting would be to know about the technology for life support systems that would reasonably reliably sustain a half-dozen people for two or more years in space without help from Earth. Adequate water recycling -- the big issue -- has been demonstrated, on a modest scale. (Air is a minor side issue by comparison.) The simplest way to address the food loop is not to try, given that freeze-dried food weighs less than half a ton per man-year. Generally, much the simplest and most reliable way to tackle a lot of the smaller recycling/repair issues is brute force: more mass, and more fuel to push it, is cheaper than major engineering R&D. Of course, trying to sell that approach to R&D-oriented organizations is a bit of a challenge. "Anything which they do not wish to do is always lacking in technology. Whether single stage to orbit or Mars missions, the technology is never quite ready..." (Jim French) -- "Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | |
#8
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Allen Thomson wrote:
[...] Equally intresting would be to know about the technology for life support systems that would reasonably reliably sustain a half-dozen people for two or more years in space without help from Earth. Which leads me down the path to wondering about life support in large "cycler hotels"; it is easy to imagine that such a venue would have more repair resources than a small station (ISS, for example). More tools, a machine shop (wonder what a 0g machine shop would look like!), spare parts, etc. But on the flip side, it isn't clear yet that all the ELCS could be scaled up for a larger venue; would you need to have 15 Elektron units for a 50 person hotel? Or could you do it with 2 or 3 units (enough overcapacity that if one unit is offline, the other could cover for a reasonable repair period)? /dps -- Using Opera's revolutionary e-mail client: http://www.opera.com/m2/ |
#9
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In recent years, Hall thruster clusters (i.e., running in parallel)
have been investigated by the Air Force and the University of Michigan. As a first stab, there have been no show stoppers identified with operating Hall thrusters together. Brian Beal's Ph.D. dissertation was concerned with a cluster of four 200 W thrusters and Mitch Walker also devoted portions of his dissertation on a pair of 5kW thrusters. You can find both of these at: http://www.engin.umich.edu/dept/aero...ertations.html For a while now, the Air Force has been focussed on clusters as a means to achieve high-power operation, while NASA has continued with monolithic thrusters. This was for a variety of reasons, not the least of which is that NASA is looking at using Hall thrusters at several hundred kilowatts, while the Air Force will probably stay below 100 kW for quite a while. As NASA continues to push to higher powers, there will be a logical point where Hall thruster clusters become necessary. This is for a variety of reasons, not the least of which are thrust density, limitations on the magnetic circuits, vacuum facility limitations, and redundancy. One concept for using Hall thrusters in the Moon/Mars initiative is to attach them to cargo tugs that go back and forth from LEO to some higher orbit, or even all the way to the destination. The crew shows up much later after making a "quick" trip on a chemical rocket. These types of missions require, at least, several hundred kilowatts. |
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