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Every time I see news about a new kind of space thruster, especially "electric" one, I'm a little hopeful that it would not require carrying propellant on board

Every time I see news about a new kind of space thruster, especially "electric" one, I'm a little hopeful that it would not require carrying propellant on board and then shooting it out the nozzle.

rout39574 6y ago
Electromagnetic tethers can do this, in an environment with a magnetic field. https://en.wikipedia.org/wiki/Space_tether https://en.wikipedia.org/wiki/Space_tether
- mrfusion 6y ago
  How far away from earth can the operate? Do these only work in low earth orbit or higher orbits too? This would be a cool concept for a solar powered space tug. Just goes to leo and picks up a payload and boosts to geo. Then comes back for the next one. No consumables at all. Just a big solar array and giant wire.
  - marcosdumay 6y ago
    GEO is well within the Earth's magnetosphere, so the question is more "how well does it work at GEO" and not whether it works at all. AFAIK, nobody has managed to make it work well enough to use it at LEO, so nobody will give you an answer to that.
- mlindner 6y ago
  Given that no one is really trying to use them, I think there's some aspect that make them not very practical, like for example the weight required is so high that they can't counteract atmospheric drag. Also you linked the wrong article. https://en.wikipedia.org/wiki/Electrodynamic_tether https://en.wikipedia.org/wiki/Electrodynamic_tether
blensor 6y ago
I've resigned myself to the fact that we are more likely going to have a The Expanse space future than a Star Trek one but I don't think it's too bad either. Because if I understand it correctly those type (not exactl that one) of thrusters propel "stuff" out of the engine not by combustion but by in this case ionizing it and pushing/pulling it along the thruster. That way you can create higher thrust by increasing the speed you shoot it out without the need to increase propellant and it's not something that needs to be refined but you could gather it along the way. So while it's not a reactionless thruster but it's main concern is still more on the energy side than on the reaction mass side
- deleted 6y ago
  [deleted]
mlindner 6y ago
That violates physics and is impossible, so you shouldn't be hopeful for that. Instead you should be looking for new improvements on efficiency (exhaust velocity), cost, and thrust-to-weight-ratio. Continued marginal improvements on those things (and there's a lot to improve upon) causes massive changes in the future.
- grishka 6y ago
  That violates physics as we know it, but there might be effects we don't know about just yet. Marginal improvements are boring. And besides, having to carry propellant is a significant limitation to the travel distance and one of the biggest nuisances of spaceflight. If you only needed electricity or other form of energy, but not matter, it would be much, much easier.

Every time I see news about a new kind of space thruster, especially "electric" one, I'm a little hopeful that it would not require carrying propellant on board and then shooting it out the nozzle.

rout39574 6y ago

Electromagnetic tethers can do this, in an environment with a magnetic field. https://en.wikipedia.org/wiki/Space_tether https://en.wikipedia.org/wiki/Space_tether

mrfusion 6y ago
How far away from earth can the operate? Do these only work in low earth orbit or higher orbits too? This would be a cool concept for a solar powered space tug. Just goes to leo and picks up a payload and boosts to geo. Then comes back for the next one. No consumables at all. Just a big solar array and giant wire.
- marcosdumay 6y ago
  GEO is well within the Earth's magnetosphere, so the question is more "how well does it work at GEO" and not whether it works at all. AFAIK, nobody has managed to make it work well enough to use it at LEO, so nobody will give you an answer to that.
mlindner 6y ago
Given that no one is really trying to use them, I think there's some aspect that make them not very practical, like for example the weight required is so high that they can't counteract atmospheric drag. Also you linked the wrong article. https://en.wikipedia.org/wiki/Electrodynamic_tether https://en.wikipedia.org/wiki/Electrodynamic_tether

blensor 6y ago

I've resigned myself to the fact that we are more likely going to have a The Expanse space future than a Star Trek one but I don't think it's too bad either. Because if I understand it correctly those type (not exactl that one) of thrusters propel "stuff" out of the engine not by combustion but by in this case ionizing it and pushing/pulling it along the thruster. That way you can create higher thrust by increasing the speed you shoot it out without the need to increase propellant and it's not something that needs to be refined but you could gather it along the way. So while it's not a reactionless thruster but it's main concern is still more on the energy side than on the reaction mass side

deleted 6y ago
[deleted]

mlindner 6y ago

That violates physics and is impossible, so you shouldn't be hopeful for that. Instead you should be looking for new improvements on efficiency (exhaust velocity), cost, and thrust-to-weight-ratio. Continued marginal improvements on those things (and there's a lot to improve upon) causes massive changes in the future.

grishka 6y ago
That violates physics as we know it, but there might be effects we don't know about just yet. Marginal improvements are boring. And besides, having to carry propellant is a significant limitation to the travel distance and one of the biggest nuisances of spaceflight. If you only needed electricity or other form of energy, but not matter, it would be much, much easier.