Creating Reaction Mass with Electron-Positron Pair Production for Rocket Thrust

In summary, a nuclear reaction can create high energy photons which can be used to create thrust. You need an energy source (nuclear?), a system which produces only high energy photons near nuclei, and a way to get the electrons and positrons to the nozzle without much interaction with anything else.
  • #1
metastable
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Given a large enough energy source (nuclear?)... can I build a rocket that creates its own reaction mass via electron-positron pair production, and then derive thrust by accelerating the charged particles out the back with a magnetic nozzle?
 
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  • #2
For pair production you need at least the following minimum conditions.
https://en.wikipedia.org/wiki/Pair_production said:
The photon must have higher energy than the sum of the rest mass energies of an electron and positron (2 × 0.511 MeV = 1.022 MeV) for the production to occur. The photon must be near a nucleus in order to satisfy conservation of momentum, as an electron-positron pair producing in free space cannot both satisfy conservation of energy and momentum. Because of this, when pair production occurs, the atomic nucleus receives some recoil.

Although a nuclear reaction might produce some such photons, it also produces lots of heat that just serves to melt the spacecraft . You not only need an energy source, you need a system which produces only high energy photons near nuclei, and does not do much else. You also need a way to get the electrons and positrons to the nozzle without much interaction with anything else.

So, with my engineer's hat on, I think energy is the least difficult part of the problem.
 
  • #3
Can I recover some of the energy spent creating the pairs by accelerating them out the back at a slightly converging angle into some sort of bell / chamber, which is designed such that when the annihilations occur, there is a high probability of the gamma rays interacting with the walls of the chamber?
 
  • #4
There have been speculative propulsion systems using a very high power particle accelerator as the impulse generator.
Obviously there are a few engineering concerns when trying to shrink a more powerful than CERN device into a spacecraft , but conceptually, it does offer tremendous specific impulse from all electric propulsion.,
 
  • #5
metastable said:
Given a large enough energy source (nuclear?)...
That energy source will be about converting mass to energy. You want to convert that energy back to mass. Try guessing the efficiency...
 
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  • #6
The OP question has been patiently and adequately answered.

Thread closed.
 
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1. How does electron-positron pair production create reaction mass for rocket thrust?

Electron-positron pair production is a process in which a high-energy photon splits into an electron and a positron. These particles have mass, and when they are accelerated in opposite directions, they create a reaction force that can be used for rocket thrust.

2. What are the benefits of using electron-positron pair production for rocket propulsion?

Using electron-positron pair production for rocket propulsion has several benefits. It allows for a higher specific impulse, which means the rocket can travel farther and faster. It also produces a cleaner exhaust, reducing the environmental impact of space travel.

3. What is the energy requirement for electron-positron pair production?

The energy requirement for electron-positron pair production depends on the mass of the particles and their acceleration. Generally, a high-energy photon is required, which can be produced by a variety of methods, such as particle accelerators or nuclear reactions.

4. Are there any potential drawbacks or limitations to using electron-positron pair production for rocket thrust?

One potential drawback of using electron-positron pair production for rocket thrust is the high energy requirement, which can make it difficult to implement in practical applications. Additionally, the production of these particles can also result in the creation of other particles, which may complicate the propulsion process.

5. How does the efficiency of electron-positron pair production compare to other forms of rocket propulsion?

The efficiency of electron-positron pair production for rocket propulsion is still being researched and developed. However, it has the potential to be more efficient than traditional chemical rockets and even some forms of nuclear propulsion. It also has the advantage of producing a cleaner exhaust compared to these other methods.

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