# Fuel used for electric propulsion?

What kind of fuel do electric propulsion spacecraft and satellites use?

Did any of them get electricity from bateries?

An ion engine creates thrust by accelerating ions using electricity. How is that electricity generated? By solar power?

• There may be a limit to the number and frequency of questions a single user asks whose answers can be easily obtained by searching within this site (or Wikipedia) that the community will accept. At some point "What research have you done?" accompanied by substantial down voting will become the response. – uhoh Aug 9 '20 at 2:13
• -1 for too many "please look this up for me" questions in rapid succession from a single user. – uhoh Aug 9 '20 at 3:53
• it's not so obvious, for non-experts, that spacecrafts are powered by batteries: none ever talks about spacecrafts batteries, everybody always talks about spacecrafts solar panels, if you pay attention to it... – jumpjack Aug 9 '20 at 9:51

Batteries don't have nearly enough power to provide for electrical propulsion. Electrical propulsion is generally powered by solar panels or (in speculative designs) nuclear reactors.

Hydrazine is used as a chemical propulsion fuel, not normally for electrical (though it's not fundamentally impossible).

Propellants (not fuel) for electrical propulsion can be a variety of things, but inert gases and high vapor pressure metals seem to be favored.

• With ion engines I know space x uses Krypton while other groups like NASA use xenon – Lonely Fox Aug 8 '20 at 23:51
• It should be clarified that the issue with batteries isn't enough power, it's that they don't have enough energy density. A lithium-ion battery pack could easily provide enough power, but it'd be exhausted in a matter of minutes, hours at most. The energy requirements are just far beyond what you can store in chemical bonds. If we could build batteries with enough energy density to run an ion thruster, we'd just use the same chemistry to make better chemical rockets. – Christopher James Huff Aug 9 '20 at 0:16
• The inert gas helium seems not to be favored. – Uwe Aug 9 '20 at 0:35
• No, though it might be favorable for some types of electrothermal thrusters. Actually, such a battery would have nuclear or near-nuclear power capacity... I wish I had a nuclear rechargeable battery. – ikrase Aug 9 '20 at 6:08
• The big disadvantage of batteries is not only that their energy density is very low, but also that it keeps getting lower as you use them! With chemical fuels, once you have used them, you shoot them out the back of your spaceship, but with batteries, you still carry their weight around even when they are empty. (Unless you do it like Rocket Lab, attach them to the outside of your rocket, and throw them away once they are empty.) – Jörg W Mittag Aug 9 '20 at 9:22

All spacecrafts get power from batteries, which act as "energy buffer", periodically recharged by solar panels. This allows providing to the onboard electronic a constant power, which may be not possible if the spacecraft is not constantly lit by Sun, like spacecrafts in non-polar orbits.

A battery can also provide an instant power much higher than the one provided by the solar panels: a spacecraft orbiting around Jupiter can collect only low power from Sun, w.r.t. an Earth orbiting spacecraft, but if it collects it into a, say, 100Ah battery, slowly charged by an 1A current for days, then this battery could even provide 1000A of instant current.

• And then solar power charges bateries which in turn are used to shoot electrons at the xenon atoms? That is how ion propulsion works? – Joe Jobs Aug 9 '20 at 10:00
• The first sentence contradicts itself, first stating that the batteries are the power source and then correctly stating that they only buffer the power from solar panels. It also inaccurately claims that all spacecraft are powered this way. They're not common, but several spacecraft have used nuclear power sources instead of solar panels. – Christopher James Huff Aug 10 '20 at 13:51