New Ion Engine Enters Space Race

Bibek Paudel brings us a BBC report on the development and testing of an new ion engine by a security firm named Qinetiq. The engine will be used in an ESA spacecraft tasked with mapping the Earth's gravitational field from orbit. Only a handful of ion drives have been used for space missions before, some of which we have discussed. Quoting: "Cryogenic pumps can be heard in the background, whistling away like tiny steam engines. Using helium gas as a coolant, they can bring down the temperature in the vacuum chamber to an incredibly chilly 20 Kelvin (-253C). The pressure, meanwhile, can drop to a millionth of an atmosphere. Ion engines ... make use of the fact that a current flowing across a magnetic field creates an electric field directed sideways to the current. This is used to accelerate a beam of ions (charged atoms) of xenon away from the spacecraft, thereby providing thrust."

bad idea

[ILuvRamen]

Xenon isn't exactly in great supply. I think they might want to rethink that and design it with a more common material. But sweet that they're finally testing an actual ion drive.

Still just a curiosity...

[OldFish]

As long as the ion drive has to carry all the mass it'll ever use it will never be useful for seriously long trips. It would need to vacuum up stray particles as a mass source for that. But it's mildly interesting anyway.

No no no. Faraday effect!

[Ungrounded Lightning]

Ion engines ... make use of the fact that a current flowing across a magnetic field creates an electric field directed sideways to the current.

No it doesn't. It creates a MECHANICAL FORCE directed sideways to the current. It's the Faraday effect, which is what drives electric motors.

It's also how you can use the Hall effect to determine whether the majority current carrier is positive or negative: The carriers are accelerated toward the same side of the conductor, so the sign of the hall voltage tells you whether you have more + or - charge carriers.

(IIRC It's how they showed that Franklin guessed wrong when he assigned + and - to charges, leading to the sign of "classical current" and the points of arrows on semiconductor diagrams being opposite to the direction of electron flow.)

Re:why xenon?

[doctor_nation]

No, mass is important. The fact that xenon is so massive is exactly why it's used- that and the fact that it has a very low ionization potential. The only better material is mercury, but they stopped using that several years ago for obvious reasons.

Re:bad idea

[doctor_nation]

It is expensive, but it has great performance compared to almost all other materials (the one better is mercury...). Sure, you can use other materials, but the efficiency drops like a rock. I think the use of Krypton or Argon is being looked at for some thrusters (maybe not ion thrusters). Oh, and ion thrusters have been around since the 60's, and Hall thrusters before that (made by the Russians). They've flown on a lot of missions already- this one isn't at all remarkable to be honest. Deep Space 1 was a lot more impressive.

Re:bad idea

[CastrTroy]

What about Radon. According to my periodic table [wikipedia.org] Radon would be the heaviest noble gas. Not countijng Ununoctium of course, but that's a synthetic element.

Re:why xenon?

[Anonymous Coward]

You also don't appear to be a fan of significant figures.

Re:bad idea

[Anonymous Coward]

Well, Radon has some, let's say, unusual side effects, including a strange tendency to make your neon sign glow mysteriously without turning the power on....

Re:why xenon?

[jollyreaper]

So...you're proposing that we propel spacecraft with baseballs?

No, we're propelling our baseballs with spacecraft, depending on your frame of reference.

Mach 1 in space...

[clbyjack81]

...this would mean that a 5000 KG spaceship would be travelling at 320 m/s, which is 1152 KM/h, which is just under Mach 1.

A minor point, to be sure, but mach numbers relate speed with the speed of sound in the same medium. Since sound does not travel in a vacuum, using mach as a unit of speed in space is meaningless.

Cheers!