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."

Comments

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: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.