Can Electron Rockets Revolutionize Interstellar Travel?

AI Thread Summary
The discussion centers on the feasibility of building an electron rocket, proposing that using electrons as propellant could solve the low exhaust velocity problem associated with ion thrusters. The idea suggests that electrons can achieve speeds up to 10% of the speed of light, potentially allowing for interstellar travel within a reasonable timeframe. However, concerns are raised about the challenges of maintaining charge neutrality and the thrust-to-mass ratio, as electrons would create a net positive charge. Additionally, while electron microaccelerators could enhance performance, the practicality of sourcing sufficient electrons remains a significant hurdle. Overall, the concept presents intriguing possibilities but faces substantial theoretical and practical challenges.
dansmith170
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Why not build an electron rocket?
Hi all,

Why not build an electron rocket? Why won't this idea work? Seems like someone could just hitch an electron gun onto a spaceship. Boom! Electron Rocket.

I was thinking about ion thrusters. These use ions to achieve thrust. They are problematic for achieving a high delta V because they have a low exhaust velocity (meaning they would require an enormous amount of fuel for high speeds - see the Rocket equation).

With Newton's Second Law, a = F/m. There are two ways to increase acceleration: 1. increase force 2. decrease mass. So, thinks I, let's just lower the mass by using electrons instead of ions as propellant. And, turns out, electrons in electron guns can achieve speeds of up to 10% the speed of light. Exhaust velocity problem solved.

Note: the application for electron gun rockets would be interstellar travel. Say we want to go to Alpha Centauri (4.2 Lightyears away) in about 50 years. Then we'll need to go 10% the speed of light for most of the trip. I think an electron rocket could achieve this with an amount of fuel that is perhaps not unreasonable (at least not as unreasonable as the amount of fuel needed for an ion thruster for the same trip).

Note 2: there are electron microaccelerators that could be part of the rocket design - this would further increase exhaust velocity and further cut down on the amount of fuel required.

It's true that we would need A LOT of electrons, although that seems like more of a practical problem than a theoretical infelicity.

Anyways, do you think this idea has any merit? And if not, why not?

Thanks.
 
Physics news on Phys.org
The photon rocket is theoretically more efficient than a rocket with massive particles as propellant.
 
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Bystander said:
You might see "coulombic explosion."

dansmith170 said:
Summary:: Why not build an electron rocket?

why not?
See above.
 
dansmith170 said:
Summary:: Why not build an electron rocket?

Anyways, do you think this idea has any merit? And if not, why not?
In our part of the universe, there is usually, for every electron, there is a positively charged nucleus nearby. So if one is shooting off electrons, from some mass, there will be a net positive charge developing.

When ions are used for propulsion, there is a method for exhausting electrons to neutralize the propellant stream.

One also has to consider the available thrust and thrust-to-mass ratio.
 
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dansmith170 said:
I think an electron rocket could achieve this with an amount of fuel that is perhaps not unreasonable
You might calculate this.

You might also compare the thrust from this with the force your spaceship will experience when it enters even a weak electric field.
 
Ion thrusters are already expelling electrons as well to stay neutral.

Ion thrusters can achieve an even higher I_sp without too much difficulty, but that needs more power per thrust. Focusing on the electrons is only making things worse. For an ideal efficiency you would want to eject both at the same speed, in practice the electron speed doesn't matter as long as it's not too high.
 
Due to the constant never ending supply of "cool stuff" happening in Aerospace these days I'm creating this thread to consolidate posts every time something new comes along. Please feel free to add random information if its relevant. So to start things off here is the SpaceX Dragon launch coming up shortly, I'll be following up afterwards to see how it all goes. :smile: https://blogs.nasa.gov/spacex/

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