New Space Engine Could Turn Tiny CubeSats into Interplanetary Explorers

[nyrath]

http://www.space.com/21867-cubesat-deep-space-propulsion-kickstarter.html

On the surface the CAT thruster looked pretty good. Then I went to the kickstarter to get some real figures.

Alas, the CAT thruster on the CubeSat is so pathetically weak it makes the Kerbal ion engine look like a Ferrari.

The Kerbal ion engine has a thrust of 0.5 kN and an Isp of 4,200.

The CAT thruster has a thrust of 0.00002 kN and an Isp of 2,000.

The main thing the CAT has going for it is a much lower power consumption and a lower mass. All it needs is about 20 watts, which is easily achievable by a small solar cell array.

[NovaSilisko]

Any real-world electric propulsion system makes the kerbal ion engine look like a ferrari. Many ion engines operate in the range of millinewtons, so 20 from something that small is pretty damn good.

[Kryten]

Not too sure how feasible the idea of an 'interplanetary cubesat' is. Wouldn't they be far too small to carry the equipment needed to communicate at those kinds of distances?

[Nuke]

as soon as i read the word kickstarter i closed the page.

i really think the issue isnt engines, its power. more power, more thrust from your engines. if you can provide a steady 200kw, vasimr gives you 5n. mpd thrusters are nice too, and they get you in the tens to hundreds of newton range (at the expense of thousands of kilowatts). there are a dozen high performance engines that would work if we had the power. a 1MW nuclear reactor would allow for some seriously powerful super efficient ion engines. the need to use solar power is why ion engines are so damn slow.

Edited July 8, 2013 by Nuke

[nyrath]

Any real-world electric propulsion system makes the kerbal ion engine look like a ferrari. Many ion engines operate in the range of millinewtons, so 20 from something that small is pretty damn good.

Yes indeed!

On another forum somebody was expressing disappointment with the performance of the Kerbal ion engine. He pointed out the CubeSat CAT engine and said that looked more like what they were looking for.

I tried to gently pop his bubble with hard reality...

[Reddragon]

I read that NASA JPL is working on new ion engines for the asteroid capture mission. In theory the asteroid tractor probe which will bring it to lunar orbit will be propelled by these engines. Interesting is that they, according to the animations and news, want to catch an asteroid about two times bigger than the Orion module. They are in testing phase now but I'm curious if they are going to be powerful enough to bring down a space rock.

[TouhouTorpedo]

Reddragon you're probably thinking of the NEXT ion thruster, they recently shut down an engine that had been running for several years for life testing. Its more or less ready and proven, once they've got a confirmed mission for it to fly on.

This ia really cool engine concept they have here, A neat idea to use pernament magnets to provide the field (since they can get away with it here as the engine is so small) but the power consumption I'm very sceptical about. It seems to be using 5 times less power than comparable large ion engines. Sure its got a pernament magnet rather than an electromagnet, but most of the power goes on the ionization... which won't have changed here. Perhaps the fuel they've been testing with has a lower ionization energy.

[nyrath]

I read that NASA JPL is working on new ion engines for the asteroid capture mission. In theory the asteroid tractor probe which will bring it to lunar orbit will be propelled by these engines. Interesting is that they, according to the animations and news, want to catch an asteroid about two times bigger than the Orion module. They are in testing phase now but I'm curious if they are going to be powerful enough to bring down a space rock.

Well, typically a gravity tractor used to divert an asteroid is going to be hovering above the asteroid on ion drive for about ten years. It does not have to be powerful, it just has to be persistent.

http://en.wikipedia.org/wiki/Gravity_tractor

[nyrath]

i really think the issue isnt engines, its power. more power, more thrust from your engines. if you can provide a steady 200kw, vasimr gives you 5n. mpd thrusters are nice too, and they get you in the tens to hundreds of newton range (at the expense of thousands of kilowatts). there are a dozen high performance engines that would work if we had the power. a 1MW nuclear reactor would allow for some seriously powerful super efficient ion engines. the need to use solar power is why ion engines are so damn slow.

Ummm, you are aware that these engines have to work with CubeStats, are you not?

This means the engine has to fit inside a couple of 10 centimeter cubes, and run off four solar cell arrays that are each 10 cm x 30 cm.

You are not going to fit a VASIMR into that small a box.

[Bunsen]

Not too sure how feasible the idea of an 'interplanetary cubesat' is. Wouldn't they be far too small to carry the equipment needed to communicate at those kinds of distances?

It can be done, but data throughput becomes a major constraint and requires huge amounts of hardware at the Earth end. The plans I've heard of call for buying time on radio telescopes and using very low data rates.

The alternative is to take advantage of large, long-lived spacecraft near the same destinations and use them as repeaters, which is already happening at Mars (not for cubesats, but you get the idea). While that does you no good for exploring totally new places like asteroids or Neptune, it could let you send instruments to places like Saturn or Mars without each one going through the multi-decade development cycle of a major probe.

[Nuke]

Ummm, you are aware that these engines have to work with CubeStats, are you not?

This means the engine has to fit inside a couple of 10 centimeter cubes, and run off four solar cell arrays that are each 10 cm x 30 cm.

You are not going to fit a VASIMR into that small a box.

i wasnt referring to the cat engine at all, but ion engines in general. i dont see how the cubesat concept would work at all beyond leo. i mean its not just the engine and propellant limits, its also the capacity to communicate at distance, which needs a large antennea, and a beefy transmitter and then you still have to get a sensor in there for whatever the mission was. some people like to think small, i like to think big.

Edited July 8, 2013 by Nuke

[Canopus]

Well, typically a gravity tractor used to divert an asteroid is going to be hovering above the asteroid on ion drive for about ten years. It does not have to be powerful, it just has to be persistent.

http://en.wikipedia.org/wiki/Gravity_tractor

The planned asteroid Capturer will trap the asteroid in an inflated bag and retrieve it that way.

[NovaSilisko]

i wasnt referring to the cat engine at all, but ion engines in general. i dont see how the cubesat concept would work at all beyond leo. i mean its not just the engine and propellant limits, its also the capacity to communicate at distance, which needs a large antennea, and a beefy transmitter and then you still have to get a sensor in there for whatever the mission was. some people like to think small, i like to think big.

Well, remember, we were able to communicate with Galileo using its measly low-gain antenna even out to Jupiter, so it doesn't take much to transmit at that distance, it just will be slow. It also doesn't necessarily need to be a cubesat by the time it's reached the level of being ready to fly out to jupiter.

Edited July 8, 2013 by NovaSilisko

[Reddragon]

Reddragon you're probably thinking of the NEXT ion thruster, they recently shut down an engine that had been running for several years for life testing. Its more or less ready and proven, once they've got a confirmed mission for it to fly on.

http://www.ctvnews.ca/sci-tech/can-nasa-s-new-xenon-ion-engine-help-lasso-an-asteroid-1.1300054

Yes, this is what I was thinking about. Btw It's gonna be an awesome mission. I imagine watching it live stream or even on TV as the astronauts arriving in lunar orbit to catch up with the asteroid.

[K^2]

Not too sure how feasible the idea of an 'interplanetary cubesat' is. Wouldn't they be far too small to carry the equipment needed to communicate at those kinds of distances?

You can do high power burst transmissions with very simple/light equipment. Continuous communication is out of the question, of course, so the thing would have to be very autonomous. But it can send back some data, including pictures.

[TouhouTorpedo]

You can do high power burst transmissions with very simple/light equipment. Continuous communication is out of the question, of course, so the thing would have to be very autonomous. But it can send back some data, including pictures.

well the problem I think hes specifically talking about is not just a question of power but literally a question of size. Antenna gain is dependent upon the size. certain design tricks can allow smaller sizes, but you've also got the problem of pointing accuracies and how to control it. End of the day the easiest way is to use omnidirectional on these things, but this needs fairly high power levels even for LOW data rates. (some systems the low gain telemetry system is using comparable power to the high gain system, even though the data rates are worlds apart) The last possible solution is phased array antenna on one side, which should make 180 degrees of view possible in theory. But I've never heard of one on this scale.

[xtremespino]

I think the whole idea of interplanetary cubesats is a great and possible idea, and with new types of solar electric propulsion being developed, and other space technology I think that its only a matter of time. Just imagine a interplanetary spacecraft that fits in a shoe box.

[sgt_flyer]

One of my concerns, is if they send a cubesat near jupiter - will the solar panels provide enough power at these distances to power the various systems ?

Heck, the rosetta probe has oversized solar panels to be able to operate so far away from earth (with chemical engines), and still had to get into sleep mode to minimize power usage before reaching jupiter's orbital altitude. Imagine if you need to operate an electric engine near jupiter in order to do your correction manoeuvers / capture burn.

The Juno probe (en route to jupiter) also has oversized advanced solar panels.

Juno's solar 45m^2 panels could give out 15000w around earth - that will be 428w near jupiter... (Jupiter receive roughly 4% of the sun energy we have here on earth)

Cubesats biggest deployable solar panels can currently output 75w - around earth.

So the same solar panels would provide less than 1w around jupiter...

Cubesats wouldhave big difficulties structurally (and by weight penalty) carrying enough solar panels.

(I don't think those cat probes could be really useful past mars... - where solar panels power effectiveness is already cut in half compared to earth)

Edited July 26, 2014 by sgt_flyer

[Whirligig Girl]

Hey! Atomic Rockets guy! Huge Fan of your website! And I can see how you'd find the Ion engine inadequate. Is it not Atomic enough for you