Revolutionary Ion Thruster To Be Tested On International Space Station (abc.net.au)

Three Australian researchers have developed "an ion thruster that could replace the current chemical-based rocket propulsion technology, which requires huge volumes of fuel to be loaded onto a spacecraft." Slashdot reader theweatherelectric shares this article from the ABC News: An Australian-designed rocket propulsion system is heading to the International Space Station for a year-long experiment that ultimately could revolutionize space travel. The technology could be used to power a return trip to Mars without refuelling, and use recycled space junk for the fuel... It will be placed in a module outside the ISS, powered, as Dr Neumann describes, by an extension cord from the station. "What we'll be doing with our system is running it for as long as we can, hopefully for the entire year on the space station to measure how much force it's producing for how long."
In the early 2000s "it was basically a machine the size of a fist that spat ions from a very hot plasma ball through a magnetic nozzle at a very high velocity," and the researchers are now hoping to achieve the same effect by recycling the magnesium in space junk.

Comments

Could be dangerous

[LesFerg]

Didn't they watch Space 1999? The entire station could suddenly be thrust into an unknown part of the galaxy.

This is the missing piece

[110010001000]

This is the missing piece we need for our colonization of Mars and the planets and beyond. With this and Musk we are well on our way to Mars. We truly live in exciting times!

Re:This is the missing piece

[ShooterNeo]

No it isn't. TLDR, read atomic rockets, n00b. Or, since you won't be reading it : high specific impulse ion drives have existed in various test forms for years. They are easy to make and they all have high efficiency, albeit some designs are more reliable than others. The problem with all of them is the nasty equation KE = 1/2 m * V^2. That means the higher the exhaust velocity (and thus specific impulse which is the fuel efficiency), energy required goes up with the square of exhaust velocity.

Plenty of ion thruster designs, including VASIMR, have reasonable energy efficiency. The problem is that you still have to pay the bill even if the efficiency were 100%. You still have to supply as much electrical power as the kinetic energy of the escaping propellant.

This is a big problem. Even the most exotic nuclear power generator designs anyone has drawn up, the nuclear generator is a heavy ass piece of equipment being propelled by barely any resulting thrust from the ion drive. It means that you might have great specific impulse but trips to Mars still take months. What you need is also high thrust. That's why the best engine for space travel that currently is feasible is still plain old nuclear-thermal. You only get an ISP of about 1000 (compare to 15k for this particular thruster), but you get thousands of times more thrust. You can complete your Mars injection burn in about half an hour instead of having to run the engine for months. That in turn increases efficiency because there is always 1 optimal point to do your engine burns at.

Re:This is the missing piece

[Anonymous Coward]

Then simply 3D print ion thrusters on Mars and bring Mars closer to the Earth.

Do I have to do *all* the thinking around here?

Re:This is the missing piece

[Ian Whitchurch]

Nahh, he's saying he's a fan of atomic rocket and he doesnt think anything else has the thrust to do what he wants, and so he does the circular firing squad thing that the space sector has been doing for the last fifty years.

Even if he is right, there is still a need for non time sensitive cargos of canned goods, metal powders for your advanced manufacturing printers, copper wire and all the other crap colonists will need, and thats where being able to go 'it'll take 500 days and we dont care' becomes important, even if it isnt the ion drives that are taking the humans to Mars they are still helping.

Re:This is the missing piece

[Lumpy]

100 years of 10 pounds of thrust never stopping, will get you going INSANELY fast in space.

Re:This is the missing piece

[Rei]

We know how Zubrin feels about VASIMR. There's also good reason to disagree with him. For example, his nuclear reactor criticism? He himself proposes building a powerful nuclear reactor to power colonies on Mars, so he's not self-consistent. His power density figures aren't anywhere close to realistic. He talks like 50W/kg is some sort of unachievably optimistic goal, when in reality ATK Ultraflex solar arrays already get 150W/kg (and MegaFlex 200W/kg), figures that have been going up significantly with time; high power nuclear designs for future space missions are measured in kilowatts per kilogram. His complaints about the funding that's gone to VASIMR versus other things are unfair, as VASIMR hasn't received all that much funding - certainly not enough to develop a nuclear reactor as he mentions. And nobody is going to develop a power system for VASIMR without having first validated the propulsion system (something Zubrin apparently doesn't want them to do). He tries to portray its various ion drive competitors as better, without mentioning that the primary reason for choosing VASIMR is its high peak thrust levels. Lastly, Zubrin's dismissal of the dangers of in-transit radiation is not shared by most researchers.

Re:This is the missing piece

[Rei]

It's a stupid comparison that's not to Zubrin's credit. The reason that no powerful space nuclear reactors have been developed is because there hasn't been any demand for them. Nuclear reactor power to weight ratios don't scale up linearly, they scale up vastly higher than linearly. Figures of 1000W/kg aren't just some sort of out-of-a-hat fantasy numbers, they're based on the very real work in the field. More to the point, even solar is already in the low hundreds of watts per kilogram, so again, Zubrin's acting like 10W/kg is the state of the art and 50W/kg overoptimistic is beyond absurd.

Re:This is the missing piece

[ShooterNeo]

1 kw/kg is still a tall order. You end up needing to use things like droplet radiators to even approach a number like that. As it so happens, solar panels are inherently much lighter because they can be a paper thin sheet of layered junctions - you can actually get much higher power/mass with solar than any heat engine nuclear reactor design anyone has drawn up. The only reason it sucks to use a solar-electric spacecraft to go to Mars is the sunlight incidence per square meter plummets to 44% out there.

In any case, Zubrin is basically correct. You may save on radiation shielding and propellant mass even if you _could_ make a nuclear electric thruster work (and you don't need vasimr - a big array of Hall or MPD or 30 other ways would work) but now you have to launch and run in flight that nasty high power nuclear reactor. He's totally right about that in that you're trading off a simple system (some tanks of propellant and/or a simple nuclear thermal rocket) for whatever exotic system you need for that level of power density.

He wants to see someone make it to Mars before he personally dies of old age, and nuclear-electric is not the way to accomplish that. This is understandable.

Re:This is the missing piece

[ShooterNeo]

Ok, so 3 kg / kw electric is 3 times worse than it "needs to be" for a 39 day trip to Mars.

Terrible. And if I actually look at the chart you linked on page 3, that's solid core fusion (0.15 kg/kWout) + Rankine Heat Engine(.14/kg heat IN) + Neutron Shield(1 per kw HEAT) + single phase radiator, 600 K(.98 kg per kilowatt HEAT).

I already know this is going to be terrible? Why? Because it's talking about HEAT kilowatts. With 600 K radiator (efficiency is even shittier at higher radiator temperatures, see the laws of thermodynamics for a source), you get maybe 33% efficiency with the Rankine cycle. I can work out the exact numbers if you demand but it's not going to matter.

so 3 * 0.15 + 3* 0.14 + 3 * 1 + 3*.98.

6.84 kilograms of heavy ass shit per kilowatt of electric power supply, best case, using conventional nuclear generators. Zubrin was right. You were talking out your rectum. Disagree? Prove it with numbers.

Sure, you can do a shit ton better with Aneutronic fusion and TWDEC. Direct conversion is 90% efficient so your heat to reject just plummeted. Go ahead and use a droplet radiator at 1000 K. And use the electricity from direct conversion to run the magnets of _another_ fusion engine where it crushes pellets of fusion fuel and the products of the reaction all escape at high velocities out the exhaust. Now we're talking, an engine that gives a respectable ISP and at the same time is lightweight so (relatively) high thrust. But that's far, far future. Scientists haven't even managed to properly contain fusion plasma yet and have only the vaguest napkin sketches of such a device.

Re:This is the missing piece

[ShooterNeo]

It's a cylinder. Inside it are rods. The rods have channels in between. There is HEU fuel inside the rods and they are made of high temperature alloys.

For a practical Mars mission, your spacecraft would have 2-4 NERVA engines, each a little smaller than the last. On earth departure, you eject the rods that block the fuel channels and dampen the reaction. Engine is cold and has never been run at that point. You run the engine until the burn is complete. Then separate the hot radioactive mess of an engine that is melting down because when the propellant flow stops, so does the cooling.

That's the simplest way to do it. No nuclear power reactor, it's 1 time use. The pumps, radiation shield, and so forth you don't stage separate, you just eject the core and pressure vessel cannister it is. (so it can be extremely light, under a metric ton)

Re:This is the missing piece

[eis2718bob]

If you have an experiment that shows a violation of conservation of momentum, the correct response is to send a grad student down to find out where the mistake is.

Not hold a press conference and start packing your bags for Proxima.

Re:This is the missing piece

[MichaelSmith]

The big problem with fission -> electric -> ion drive is that your fission reactor needs a cold sink which can absorb its entire power output. To do that you will need a lot of radiating surfaces and associated plumbing. It adds up to a lot of mass, perhaps more than the reactor and shielding.

Re:This is the missing piece

[pslytely psycho]

Actually I think he is referring to this when he said read atomic rockets. Instant armchair physicist. It is quite interesting and written so that I could follow at least the concepts, although I lack the math to verify its accuracy:
http://www.projectrho.com/public_html/rocket/engines.php
I was introduced to it a few days ago after buying the video game Children of a Dead Earth. A space battle game using n-body physics.
He certainly could of been more eloquent in stating his case, quite unnecessary. As you replied to him, I thought you might find the site of interest.

Re:This is the missing piece

[lhunath]

I may come off as terribly ignorant now, but would it not be reasonable to use such an engine for a cheap permanent ferry between Mars and Earth that never stops? It could spend a few years gaining velocity before it gets put into use.

Re:This is the missing piece

[St.Creed]

Well, these guys (http://www.deepspace.ucsb.edu/projects/directed-energy-interstellar-precursors) seem to think it may work, at least for small packages.

"As an example, on the eventual upper end, a full scale DE-STAR 4 (50-70 GW) will propel a wafer scale spacecraft with a 1 m laser sail to about 26% the speed of light in about 10 minutes (20 kgo accel), reach Mars (1 AU) in 30 minutes, pass Voyager I in less than 3 days, pass 1,000 AU in 12 days and reach Alpha Centauri in about 20 years. "

Apart from Mars being 0.52 AU away right now, it would take 15 minutes to pass Mars. Unfortunately, if you want to stop you need to put on the brakes after a few minutes. But still. That said, having an orbiting 50GW laser array over our head might make some nations a tad nervous.

Original article: https://arxiv.org/ftp/arxiv/pa...

Here's the calculator: http://www.deepspace.ucsb.edu/...

A russian billionaire is funding this: http://www.sciencemag.org/news...

I've a picture of him at the press conference here: http://i33.photobucket.com/alb...

Interview with Dr Neumann

[SpaceDave]

For those interested, there is a lengthy and interesting interview with Dr Neumann about this on The Space Show. http://thespaceshow.com/show/0...

Some more information

[Ian Whitchurch]

Hi,

I'm Ian Whitchurch, the CEO of Neumann Space.

First of all, if you want more technical information about the Neumann Drive, there's an article in Applied Physics Letters. It may be available here

http://scitation.aip.org/conte...

If that isnt working, then you might know someone with an APL subscription, or it might be somewhere on the internets under "A centre-triggered magnesium fuelled cathodic arc thruster uses sublimation to deliver a record high specific impulse Patrick R. C. Neumann, Marcela Bilek and David R. McKenzie".

Secondly, it's not just the Neumann Drive that's going up to the Bartolomeo platform on the ISS. We're planning on taking a bunch of other peoples small projects, which deserve to go into space, but cant by themselves get a ride into orbit, or an easy method to get power, heating, cooling and communications once they are there. If you're interested, you might want a look at this fine Airbus DS press release.

https://airbusdefenceandspace....

There is also information available about the Facility for Australian Space Tests on our website, at http://neumannspace.com/fast/

Thirdly, Im happy to answer further questions people might have.

Finally, our poor, poor website. Also, the original post lacks a poll, which itself lacks a Cmdr Taco option. What the heck am I supposed to vote for ?

Re:Some more information

[Rei]

Thanks for chiming in and linking the paper, and my apologies for exposing yourself to the comment environment here, which has become rather toxic concerning space issues of late. The fact that the press coverage comes across as "hype-y" doesn't help any.

While I think your premise of using space junk is... let's say "optimistic", in the anywhere-close-to-near-term timeframe.... the engine concept itself seems quite sound and interesting. I can't read the paper (not going to shell out $30 for it... not your fault I know, the publishing world is terrible), but - how sensitive is it to the geometry of the cathode? Is your concept that things would be melted down and cast (or extruded, or any other mechanism) into your desired geometry? I assume that at present you're doing something like feeding in wire off a spool to act as the cathode?

Re:Some more information

[Ian Whitchurch]

It's press coverage - it's going to be hypey, and thats just the world we live in. As indeed is toxic comment environments :)

While running on space junk would be nice, it doesnt need to happen for the drives to be useful. If you're rocking 11 000s of specific impulse, then it's simple enough to bring a shipment of cathodes up from earth, transfer to a SEP tug and take them to where they are needed. The fact they are solid, and therefore dont need to be kept at the correct temperature and pressure helps a lot.

Cathode geometry is something we need to do more science on. At the moment, we've been working with one inch diameter circular cathodes, and the 'star' erosion pattern appears to be a thing. Yes, we're definitely looking at cast/extruded cathodes. We've got some ideas about how to move cathodes forward, and thats on the 'to do' list for the model thats going up to the ISS.

Comparison, please

[Applehu Akbar]

How does the energy input and thrust produced compare to NASA's current operational ion engine, which has been in use on the Dawn mission for the last ten years?

Re:Comparison, please

[Ian Whitchurch]

http://descanso.jpl.nasa.gov/S... is as good a summary as any about NASA's current ion engines, while the APL paper by Neumann, Bilek and McKenzie for the http://scitation.aip.org/conte... has information about the Neumann Drive.

Short version is that xenon drives vary in specific impulse and power efficiency depending on the power levels, while Neumann Drives vary in specific impulse and power efficiency depending on the fuel used, while the power level affects how many pulses per seconds. Higher power levels appear to cause faster wear of the grid in Gridded Ion Thrusters, or the chamber in the case of Hall Effect Thrusters, as well as needing more investment in Power Processing Units and so on. Additionally, there is the issue of tankage, regulators and so on for dealing with the xenon itself, which means it's not a straight 1:1 comparison. That said ...

TLDR : Magnesium in a Neumann Drive runs about 9 uN/watt and 11 000s specific impulse. A NSTAR running at ~1000 watts input has about 32 uN/watt and 2850s of specific impulse.

Re:Comparison, please

[Zelig]

The Neumann thruster is all about saving launch capacity. Most of the ion thrusters we have now work with e.g. Xenon gas; you have to loft their fuel, and your engine mass budget has to include the material handling for the propellant; tanks, valves, etc.

The idea of the neumann thruster is that your reaction mass comes from a simple sold puck which is gradually ionized; so you immediately win on a bunch of hardware you don't have to lift.

And then, you can use as reaction mass the sorts of stuff which is already up there in orbit. Got some excess second stage, which you've lofted to orbit at ruinous cost? Instead of dropping it back into the atmosphere to burn up, melt it into a puck at the focus of some mirrors, and then use it as reaction mass for a few years.

Space junk turned into valuable fuel. Big win. .... IF it works.

Re:Comparison, please

[NEDHead]

Not fuel, reaction mass

The main problem is safely grabbing the space junk

[Gravis Zero]

The problem with space junk is less about getting to it and more about getting to it safely. Everything in orbit is travelling a minimum of 17,000 mph. Have you seen what happens when car into a wall at only a 100 mph difference? Think two flimsy satellites colliding with a 400 mph difference. There will be hypersonic shards of metal everywhere.

EM Drive -v ION drive = 1st space robot wars

[seoras]

I'd like to see an EM Drive put into testing up there too (yes, yes, yes - I know it's defying the [known] laws of science. No reason not to test it in space since it seems to pass all tests on earth)

Hey maybe we could strap the ION Drive face-to-face with an EM Drive, throw them out the hatch and see who pushes who around!

Re: EM Drive -v ION drive = 1st space robot wars

[Ian Whitchurch]

Is this a casual conversation, or are we talking, like *numbers* here ?

If it's the latter, the 1kW is going to be the biggest constraint - you're asking for a lot of power.

As far as costs go, I'd say we're looking at 'not especially ambitious' Kickstarter, especially if you're happy for it to not come back, and to cut that power demand down a little.

Re:EM Drive -v ION drive = 1st space robot wars

[Gavagai80]

Name one breakthrough in science which was made by a crackpot -- someone who was dismissed as not being a real scientist, rather than simply considered to be incorrect by fellow scientists.

Re:EM Drive -v ION drive = 1st space robot wars

[joe_frisch]

Anyone who wants to fund the experiment is of course free to do so. I'd advise against it though,. The EM drive claims to violate conservation of momenum (4-momentum if you are being picky), under conditions that are not in any way outside the range of typical experiments. The theory, at least as presented in the AIP advances doesn't make any sense at all. The experiments are tricky and easy to get wrong. (the thrust is tiny so forces on cables etc could easily distort the measurement).

I know the argument about long shots and Pascal's wager, but there are an infinite number of possible experiments, so trying random ones doesn't make sense.

An earth based measurement with a superconducting cavity (which would allow large fields with very small RF power), would probably be a better / cheaper test.

Probably just making a point

[Okian Warrior]

... There will be hypersonic shards of metal everywhere.

Um, I know this may be a dumb question, but I'm trying to get a handle on how fast those shards would be going.

So, what's the speed of sound in space?

Thanks,

P. Edant.

The speed of sound is dependent on temperature, but doesn't vary all that much - 1200 km/h to 1000 km/h at about -60 C.

Once you get to vacuum, "the mean free path" of the particles becomes so long that the atmosphere begins to act less like a gas and more like individual particles. Changes in pressure are not propagated efficiently in this situation, so the idea of "sound" starts to lose its meaning.

I think the OP was just making a visceral point. If we use the sea-level 1200 km/h speed and note that orbital velocity is about 28000 km/h then depending on the angle the shards could hit anywhere from 0 to twice the orbital speed.

A 1 gram bolt hitting the front of your spaceship at 28000 x 2 = 56000 km/h would deliver an energy of 121,000 joules on impact (if I did the calculations right), equivalent to about 25 grams of TNT.

Roughly 1000 times impact of a sledge hammer. (10 kg hammer going 5 m/s => 125 joules).

Sloppy diagram

[Traf-O-Data-Hater]

How on earth (or halfway to Mars) did the 'Tigger' typo in the diagram slip past checks? Or did no-one at the company look over the 'How it works' page? And that unsecured capacitor in the video makes me shudder.

It's better for cargo then for people

[Required Snark]

This seems to be a very good low acceleration long haul thruster, similar to other competing ion drives. They are all of a type. Neumann seem to have done their homework in figuring out how to match solar panel output to mission profiles.

However, ion thrust technology has some real problems when it comes to moving people around the solar system: transit time. If you look at this description, it turns out that the fastest travel time from Earth to Mars they quote is seven months. That's not from LEO but from a station at L5 to a Mars orbit where there is another orbiting station. Getting out of the gravity well is assigned to chemical rockets. This architecture requires a lot of infrastructure investment. Without these stations it's likely the transit time are much longer, closer to the 9/18 month burn and coast transfer orbits.

Long term exposure to weightlessness is not good for humans. For example, space station cosmonauts (tweaked you on that one) have long term vision problems. Even worse is the radiation exposure outside the Van Allen belts. The manned mission to Mars community, including NASA, seem to be underestimating the seriousness of this problem. It's not just about cancer. There are other long term problems like heart disease and general decline in health and longevity. For example, the long term effects of exposure to radiation from Chernobyl have been terrible in affected areas in Belarus and the Ukraine. (There is a huge coverup over this situation, so you don't hear anything about it. Even the World Health Organization seems to want to sweep it under the rug.)

It's surprising that no one here has made any comparison to the recently released road-map from SpaceX. They propose a 30 day transit time without needing any orbital infrastructure either at Earth or at Mars. They are further along then Neumann, having their first generation hardware already proving itself in space flight, while Neumann is only now doing a flight test. Even so, it's unclear if ion or chemical engines are the best way to send humans to Mars, assuming that is a good idea in the first place,

Looking at the specs, if the Neumann system works as advertised it would be well suited for exploring the outer solar system. If paired with an RTG It would allow significant size missions to the outer planets that could go into orbit and not be limited to flybys. They confidently describe continuous acceleration for years at a time with a single fuel slug weighing in at a few kilograms. Even though manned missions to Mars are more glamorous, exploring the solar system is equally important in the long run.

Re:It's better for cargo then for people

[Required Snark]

Sorry, I mistyped a 30 day trip time for SpaceX when it should have be 90 days.