New Ion Engine Being Tested

Dr Cool writes "A new design of spacecraft ion engine has been tested by the European Space Agency which 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."

cool but

[ShaneThePain]

Ion engines are high impulse, low torque, so they are appropriate only once your already IN space. even then, there is extremely slow acceleration. I think the construction of a space elevator http://en.wikipedia.org/wiki/Space_Elevator [wikipedia.org] would be a much greater step towards "casual" space flight. even so, very cool.

Deep Space 1

[saskboy]

I remember reading about Deep Space 1 and it's Ion engine about 8 years ago. I was most impressed that the thrust is about that felt on your hand by a piece of paper when held on Earth. The key is that it accelerates the ship to a speed much greater than traditional rockets, not how quickly it does that. Besides, you don't want to go from 0 to 60 in .058 seconds, unless you want to be a smear on the bulkhead.

Increase in the number of grids

[Verloc]

This innovation came from the addition of another grid (from TFA) used in the process of accelerating the ions. Is there any reason that they couldn't just keep adding grids with varying voltages? And why are the last two voltages both low? Wouldn't it make sense to alternate them?

IANAPP (I am not a plasma physicist), but...

[Tsar]

The test model achieved voltage differences as high as 30kV and produced an ion exhaust plume that travelled at 210,000 m/s, over four times faster than state-of-the-art ion engine designs achieve. This makes it four times more fuel efficient, and also enables an engine design which is many times more compact than present thrusters, allowing the design to be scaled up in size to operate at high power and thrust.

Since KE=(mv^2)/2, wouldn't an ion engine with over four times the exhaust velocity have over 16 times the efficiency, all other factors being equal? And wouldn't an increase in ion KE produce a proportional increase in the erosion rate of the dual low-voltage grids, along with a concomitant shortening of the engine's usable service life?

Tandem accelerators

[jd]

The technique is used in tandem accelerators. You have a grid that is negatively charged (so it attracts the ions) immediately prior to the grid that is positively charged (that repels the ions, once they are through the negatively-charged grid).

Whether this is efficient to do depends on the speed of the ions. As the velocity of the ions increases, the mass increases and therefore the energy required to achieve the same level of acceleration also increases. Of course, the grids have mass, as does the energy source, so you increase the amount of force needed to achieve the same acceleration.

The ESA are a lot of things - many of them unprintable - but I am prepared to believe they're smart enough to have done studies on multi-stage accelerators as most European physicists have worked on them. (Many particle accelerators in Europe were of this kind, at one point.) If they're only using one grid for acceleration, there's a good chance they'll have crunched the numbers and decided that a single grid was the best bet.

Unfortunately, politics in European space research is (almost) as bad as in NASA, so it cannot be automatically assumed that the solution adopted actually is the option the engineers and ion engine scientists would have preferred. For that reason, I would certainly encourage anyone who knows the science to offer up guesstimates on what different configurations would be like. I would ALSO encourage CmdrTaco and the Slashdot team to see if they can pester someone at the ESA into giving an interview.

Why increase grids?

[Darkman, Walkin Dude]

Why not just increase the number of ion engines? If one gives for example a 1 m/s thrust, wouldn't 20 of them combined give a 20 m/s thrust? I know its not that simple, but you will see significant increases in acceleration, I am sure. Put together a platform with 50 of them, slap on a crew compartment and storage spage, and you have your first in-system exploration ship to go gadding about in! I'd probably throw in a nuclear plant for the giant frickin lasers myself (purely to clear debris, naturally ;)), but we could build all that right now...

Dumb health question

[Jeremi]

Okay, here's a dumb question for you: I've got a pretty good idea what would happen to me if I stood right behind a traditional rocket while it was lit. But what would happen to me if I stood right behind one of these while it was running? Instant death? Intense pain? A refreshing tingly sensation?

Got an idea

[dascandy]

What if you view the speed you're going at as a 4-dimensional vector with the basic 3 axis of space and the axis of time. That way, speed would (should) be a constant, where, if you accelerate more in the space domain in any direction, your speed in the time domain would decrease. Now, if you could accept that travelling faster than the speed of light is impossible only due to this vector being constant in size, you could accelerate until it is on the other side of the timeplane, thereby allowing you to travel through time.

Didn't think about what paradoxes you'd need, and you'd probably bump into yourself at the moment of turnaround, but aside from that...

No research done whether this could be true, but it's an idea I've been playing with.

Mars vs Outer Planets

[sanman2]

I realize these ion engines have a low thrust/acceleration as a tradeoff against their better fuel economy, which means they're really meant for the long-duration missions such as to the outer planets, etc. Yet I wonder if this new ion thruster design, and also the Double Layer Helicon Thruster that was also recently tested, will result in ion engines that could take man to Mars?

It would be nice if upcoming unmanned space missions could put these new ion engines through their paces, to see how much performance we can squeeze out of this technology. Let's see how high they can make the thrust go. I read on the newsgroups that ion engines could one day emulate the VASIMR concept which can achieve a wide variety of thrust characteristics.

Or what about a 2-stage rocket design? Just have a regular chemical rocket first-stage with high thrust to escape the earth's gravity, and then from there use ion engines to power the 2nd-stage.

Re:Old News

[anno1602]

These ideas have been floating around NASA and the defense industry for years.

Ion engines, yes. Dual-Stage ones? I was under the impression that they were new.

So why haven't these engines been put into use?

What are you talking about? Dual-Stage ion engines are just being developed, and conventional ion engines are/were in use both on NASA and ESA probes.

As a result the only projects suggested were either unmanned deep space probes

You seem to be implying that unmanned space exploration is useless. It is anything but. If at all, the presence of humans in space is of questionable scientific value.

they provide very little acceleartion

If you had RTFA, you'ld have seen that this new technology remedies exactly that problem and woud lend itself for Mars missions.

Not so dumb.

[imsabbel]

Well... on earth, nothing would happen, as this kind of engine only works in vaccuum... The mean free travel lenght of those ions in air would be meassured in mircrometers...

In vaccuum, you would die rather violently, due to shortage of air....

So i dont think this is a practical concern...

Of course, if you were in a spacesuit, there would be an issue...

The process (hitting an object with high energy noble gas ions) is also used on earth, where to precess is used to alter surfaces of materials. Its called "sputtering", or "plasma etching". So i guess you can get a general idea of what it does... It cant penetrate your spacesuit, but will happily kick layer by layer of atoms from its surface.

If you waited long enough, it would open holes/ect, but it you be very damaging to sensor equipment/solar cells even with short exposures.

Think of a very low power slaver desintegrator from the ringworld novels :D

Re:Don't go getting any ideas

[Anonymous Coward]

"ButFTL acceleration is not impossible. It is completely meaningless as it simply violates causality. If FTL accn is possible, then our entire understanding of physics is almost completely wrong, and there is ample tangible evidence to suggest that is not so."

I wouldn't say that. What about Quatum tunneling?

http://www.npl.washington.edu/AV/altvw75.html [washington.edu]

"In particular, Aichmann and Nimtz have recently transmitted Mozart's 40th Symphony as frequency modulated microwaves through an 11.4 cm length of barrier wave guide at an FTL group velocity of 4.7 c, receiving audibly recognizable music from the microwave photons that survived their barrier passage. The transit time through the barrier was about 81 picoseconds and was observed to be constant for barriers with widths varying from 4.0 cm to 11.4 cm."

Not more fuel efficient

[Anonymous Coward]

LESS fuel efficient, the fuel is the energy source (solar or nuclear in ion engines case). It's a shitload more mass efficient though...

Re:cool but

[heavy snowfall]

Wasn't there some movie where they put the rocket miles under water and used the buoyancy to accelerate it? Cool idea.

Charge accumulation?

[JourneyExpertApe]

Does anyone know how these engines avoid accumulating a net charge over time? If you're emitting a stream of positive ions for a long time, and you're not taking in any negative ions, you would have an increasingly large negative charge. It seems that this would decrease the thrust over time, not to mention electrocuting the vessel upon re-entering an atmosphere.