# Interplanetary electron gun

How feasible would it be to use a huge electron gun to pump electrons from a solar array positioned close to the Sun back to Earth or Mars?

My idea is to create a eletrical circuit by means of using electrons discharged from a huge solar array positioned very close to the Sun. Each side would have a electron gun and a electron deceleration/capture plate, forming a closed circuit.

Near the Sun, the electron gun/electron capture plate would be powered by a solar array capturing terawatts of energy. Near Earth another set of a gun and a capture device would close the circuit. The energy would be transformed in space using huge transformers and sent down to earth via a kind of space elevator as a very high voltage link. Same on Mars, Earth's Moon etc.

How feasible would be that?

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How does the electron gets accelerated ? For free ? Or do you spend energy into the speed at wich the electron exits the gun ? If you launch the electron at say 0.5C and it returns at 0.1C then somehow energy was used at the near-earth station and generated at the near-sun station. But if i do so continually, the plates will charge up to a point where i cant add more electrons/remove electrons from the guns thermionic emitter. So i do it in pulses of electrons. Charge up the near-sun station receiving plate positively and the guns emitter negatively, using the solar panels output, multiplied by a transformer (like a big camera flash), bang the electrons free they fly to earth. Near-earth plate becomes charged negatively up to a point thats harder and harder to add electrons. Discharge the plate into the gun via a transformer, using a big inverter. Discharge the near-earth gun back to the sun, where the positively charged near sun plate will become more and more neutral. I know thats something still wrong, but i cant see where.

• Version of the question : worldbuilding.stackexchange.com/questions/3372/… Premise is there...zapping the energy from the earths orbit to the earth can be an issue Commented Mar 2, 2015 at 22:41
• Different answer : He plans to beam electrons from the moon not from the sun and he was unable to create a way to close the circuit via collecting plates/decellerators. Commented Mar 2, 2015 at 22:52
• @user3453518 It's wrong because you're not using the attraction of charges to move the particles, you're firing them from a gun. That means you always have to provide the energy to move the particle rather than taking advantage of the physics. If you don't have a local charge gradient to discharge the particles aren't going to move for free. Commented Mar 3, 2015 at 4:28
• If you want to send power, a better method might be to use a microwave/submillimeter beam aimed at a receiving antenna on Earth, or use a concentrator (think magnifying glass) instead of a solar array to focus a large amount of sunlight onto a gigantic solar array on Earth. Commented Mar 3, 2015 at 4:33

This is not very feasible at all as described. You'd have electron beam coherence problems - the electrons would want to get as far away from one-another as possible, so by the time any of the electrons reached their destination, the other 99.9...% would have gone walkabout...

• Are you sure this is a impossible proposition ? Cant the electrons be collimated enough ? I know the electrons have a tendency to repulse each other because they are electrically charged, but i believe theres a ratio where the electrons disperse enough. How many kilometers away would the beam decoherence would become a problem ? Can this be solved by intermediary stations placed along the path ? Say, a set of multiple guns and collectors spaced at some million kms, enough to prevent much energy loss. Commented Mar 2, 2015 at 22:54
• Atom smashers maintain the coherence of electron beams with powerful magnets every few metres. Unless you can afford huge electromagnetic collimators every kilometre at the most - or a very long wire - you're out of luck. Commented Mar 2, 2015 at 23:14
• How about firing a single electron when the previous is already a km away? The force would, effectively, be entirely along the direction of travel. Of course, the power would be nil :) Commented Mar 3, 2015 at 0:22
• @Samuel, Yes, you could fire a single electron and be reasonably certain of where it would end up, allowing for the effects of the solar wind. However, you would not be able to transfer much energy that way. Commented Mar 3, 2015 at 0:38

I do not see that work.

Lets assume that we want charges be balanced at all points in space and time. So for each electron send to earth by the near-sun electron gun you need one electron sent back from the near-earth electron gun. For that electron to arrive at the same time it needs to travel at the same speed, hence the accelerating voltages and the energy spent per electron at both ends of your system will be the same. Therefore there will be no net gain in this system and no energy transfered.

• What happens if instead of working as a DC system, we charge up a bank of capacitors and use a pulsating system where the return path takes a longer time than the ongoing path ? Commented Mar 2, 2015 at 23:11
• I'd argue that if any path takes longer than the other you'll end up charging both stations. And while you might not literally run out of electrons to transmit this seems undesirable for the setup anyways. How about transmitting uncharged particles one cannot run out of - photons spring to mind ;) This would also solve Monty Wild's issue of beam de-coherence. Commented Mar 2, 2015 at 23:19
• Photons would de-cohere all the same, if only by a much smaller margin due to lack of repulsion forces present on same-sign charged particles like electrons. While electrons can transport a much larger ammount of energy than photons. Commented Mar 3, 2015 at 0:18
• If you allow the return path to have more electrons moving slower, you won't run into this problem (you will still have decoherence problems though) Commented Mar 3, 2015 at 4:27
• An ever increasing number of particles in the system do not sound like a balanced circuit to me. Commented Mar 3, 2015 at 8:24

As others have noted, sending electrons from the Sun to the Earth is not going to work. They won't make it across the space with any precision.

Sending electrons one way is not a closed circuit. This is not an electrical circuit, it's charge transfer. If you are not removing that charge from the receiving plate you will need more and more energy to keep adding electrons.

Additionally, getting an orbit very close to the Sun with the same orbital period as the Earth is not going to be free. The panels will need constant propulsion to keep from falling into the Sun.

• When the plate is sufficiently charged, a batch of electrons is sent back to the sun using the same method. By having the plate charge/discharge rate set at a certain frequency, and having the primary of a transformer set between the plate and the electron gun, there will be a voltage induced into the secondary of the transformer. This voltage would be transported back to earth in a "space elevator" style. Commented Mar 3, 2015 at 0:55
• @user3453518 I fail to see how that nets you any energy. Any energy gained from an electron received will be lost when you send it back. Assuming 100% efficiency, you'll break even. Commented Mar 3, 2015 at 0:58
• Not if the speed at wich the electron comes is bigger than the speed at wich the electron returns. Commented Mar 3, 2015 at 0:59
• @user3453518 You're not getting energy from the arrival speed, only the charge. Why else would you use electrons? If you think you can get energy from arrival speed it's a much better idea to use rocks. You'll avoid all the other problems associated with using charged particles. Commented Mar 3, 2015 at 1:06