ESA and ANU make space propulsion breakthrough

[tocqueville]

11 January 2006

The European Space Agency and the Australian National University have successfully tested a new design of spacecraft ion engine that dramatically improves performance over present thrusters and marks a major step forward in space propulsion capability.

Ion engines are a form of electric propulsion and work by accelerating a beam of positively charged particles (or ions) away from the spacecraft using an electric field. ESA is currently using electric propulsion on its Moon mission, SMART-1. The new engine is over ten times more fuel efficient than the one used on SMART-1. “Using a similar amount of propellant as SMART-1, with the right power supply, a future spacecraft using our new engine design wouldn’t just reach the Moon, it would be able to leave the Solar System entirely,” says Dr Roger Walker of ESA’s Advanced Concepts Team, Research Fellow in Advanced Propulsion and Technical Manager of the project.
The new experimental engine, called the Dual-Stage 4-Grid (DS4G) ion thruster, was designed and built under a contract with ESA in the extremely short time of four months by a dedicated team at the Australian National University. “The success of the DS4G prototype shows what can be achieved with the passion and drive of a capable and committed team. It was an incredible experience to work with ESA to transform such an elegant idea into a record-breaking reality”, says Dr. Orson Sutherland, the engine’s designer and head of the development team at the ANU. During November 2005, the DS4G engine was tested for the first time in ESA’s Electric Propulsion Laboratory at ESTEC in the Netherlands, with support from Dr Sutherland and ESA test engineers.
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Once ready, these engines will be able to propel spacecraft to the outermost planets, the newly discovered planetoids beyond Pluto and even further, into the unknown realm of interstellar space beyond the Solar System. Closer to home, these supercharged ion engines could figure prominently in the human exploration of space. With an adequate supply of electrical power, a small cluster of larger, high power versions of the new engine design would provide enough thrust to propel a crewed spacecraft to Mars and back.

“This is an ultra-ion engine. It has exceeded the current crop by many times and opens up a whole new frontier of exploration possibilities,” says Dr Walker.

http://www.esa.int/esaCP/SEMOSTG23IE_index_0.html

[LisaM]

1. Does it pollute less than what we have now?

That is an important factor.

[tocqueville]

2. it's basically non-polluting at all

the problem is the supply of electric energy to start the ion propulsion. For high-effect versions solar batteries might no be enough, specially for missions far away. Then we are left with atomic batteries to "ignite" the process.

[don954]

3. BTW, its not a launch thruster

its a long term thruster designed to get many times more energy out of the same amount of fuel, for deep space probes and such.

As far as boost engines, the solid boosters are pretty bad due to the binder epoxy, but the liquid shuttle main engines only output water vapor as they use LOX and liquid Hydrogen as fuel. the solid boosters are aluminum powder and epoxy binder.

[phantom power]

5. There are better solid boosters.

Here's a design that uses either rubber or plexiglass, oxidized by N20 (the old pressurizer for whipped cream)
http://www.spacedev.com/newsite/templates/subpage3.php?pid=185

[eppur_se_muova]

7. Only operates in high vacuum, outside the atmosphere.

And the exhaust is likely to end up getting blown out of the solar system by the solar wind. Not really an issue.

[crizzo5137]

4. Europe will plant an EU flag on Pluto....

While the wingnuts here are wasting our money on iraq and scaring the fundies about the eVils of gay marrage... GASP!...


jeeeez i wish i could move to europe

[NNadir]

6. This is exciting. They don't say what kind of plasma they are using.

Previous ion engines used xenon, which I found surprising, given its high ionization energy.

Once in space, cesium or rubidium would be superior, owing to their low ionization energy, particularly the former, owing to its higher mass. However I think these metals were problematic on space craft, since they immediately explode into flame upon contact with air. This would not be a good thing if the spacecraft were sitting on a launch pad.

An intriguing idea, where justfied, would be to generate these metals in situ in space from appropriate salts or oxides. I have not calculated however if any such salts would justify the added launch weight and the energy expended in converting such salts or oxides into metals. I suspect some one has already calculated this, which is why xenon is used.

The heaviest (meta)stable isotope of cesium, is cesium-135, which is readily available in ton quantities. However it is only 1% as heavy as the heaviest isotope of xenon available, Xe-134. On the other hand, xenon is very expensive and cesium-135 is not.

[muriel_volestrangler]

8. It still seems to be xenon

according to this Google cache of the project diaries (complete with pictures of celebrating scientists!)

http://64.233.183.104/search?q=cache:W3pk38pXA_MJ:www.esa.int/gsp/ACT/propulsion/safe_test_diaries_wk4.htm+DS4G+xenon&hl=en&client=firefox-a

"1% as heavy as"? Do you mean "1% heavier than" - ie per atom?

I think the ionization energy may not be an important consideration for ion engines - they are always wasteful of energy, but very efficient in terms of reaction mass. Since they expel the exhaust at such high speeds, nearly all of the kinetic energy goes to the exhaust, rather than the craft. But the advantage of using so little mass it worth it if you have an energy source outside the reaction mass - solar, or nuclear. So taking up a compound as the reaction mass would mean either a waste product, or a second element to ionize - possibly needing a second ion engine.