Fission caused by positrons - in a fission fragment rocket?

In summary, the conversation discusses the potential of using dusty plasma fission fragment rockets for high delta-V exploration and the possibility of using positrons to enhance their efficiency. However, the idea of using positrons for this purpose is deemed unlikely due to the low efficiency of positron production and the lack of a plausible mechanism connecting positrons to fission. The conversation also highlights the importance of approaching scientific questions with a plausible and quantifiable explanation rather than randomly combining unrelated concepts.
  • #1
Al_
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I was fascinated to learn about dusty plasma fission fragment rockets.
https://en.wikipedia.org/wiki/Fission-fragment_rocket
There's talk that they might enable high delta-V exploration like a manned Jupiter mission! However, they need to be surrounded very many tons of neutron moderator material so the neutrons can cause a chain reaction.
If you could save the mass of the neutron moderator, the thrust to mass ratio goes up, and the voyage times come down, as well as the cost of construction. Something said on another thread made me wonder if antimatter (positrons) could be fired at Thorium dusty plasma with similar effects? I found a report that large numbers of positrons were made by bombarding gold with electrons - https://www.llnl.gov/news/billions-particles-anti-matter-created-laboratory
Could this work from a Particle Physics viewpoint?
 
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  • #2
What effect do you expect from the positrons? "Did you try X" is useless without an idea how X could be interesting.

Positron production needs a huge amount of energy, by the way.
 
  • #3
mfb said:
What effect do you expect from the positrons? "Did you try X" is useless without an idea how X could be interesting.

Positron production needs a huge amount of energy, by the way.
I was wondering if Thorium fission could be caused by positrons.
 
  • #4
Al_ said:
I was wondering if Thorium fission could be caused by positrons.

You are not answering the question. Your response is more of a blind shot into a barrel hoping to hit something.

You need to come up with the physics that might support what you are claiming. That is how we do science, and that is how it is done here, not simply make up blind guesses hoping that one would stick.

Zz.
 
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  • #5
Al_ said:
I was wondering if Thorium fission could be caused by positrons.
Or electrons, muons, taus, grains of sand, apples, hitchhiker books...?
That approach doesn't work.
 
  • #6
mfb said:
apples

Very small rocks...cider..grape gravy...cherries...churches...lead
 
  • #7
I'm puzzled at your responses. How would you like the question to be framed?
 
  • #8
The whole type of question does not lead to interesting results.

If you have a reason to expect that X can influence Y, feel free to ask if and how it does. But randomly combining two things in physics does not make a useful question.
 
  • #9
mfb said:
If you have a reason to expect that X can influence Y
I see!
The reason to think that was a post by ProfChuck : https://www.physicsforums.com/threa...may-enable-trips-to-mars.889815/#post-5604600
where he says: " I am currently consulting with a company that is researching a propulsion system based on positron annihilation. There are several promising approaches including a positron powered VASIMR engine and another that involves direct conversion of anti matter reactions to thrust."
Positronium might become more available thanks to : https://www.llnl.gov/news/billions-particles-anti-matter-created-laboratory

But maybe I read his post wrong, he linked to : http://thefutureofthings.com/3031-new-antimatter-engine-design/

If you combine two design ideas - stored Positronium and a rocket with a magnetic nozzle, then is it possible to build a rocket that has both high thrust and a high specific impulse?
I think it depends if the annihilation results in charged fragments.
Would Positronium annihilation in dust particles result in a substantial % of charged dust fragments with velocities of a fraction of c ?
 
  • #10
You do know that matter-antimatter annihilation has nothing to do with what you asked in this thread, don't you?

Zz.
 
  • #11
OK, more thinking required.
 
  • #12
Al_ said:
Would Positronium annihilation in dust particles result in a substantial % of charged dust fragments with velocities of a fraction of c ?
No. And you are doing the same mistake again. You randomly combine two unrelated concepts.

Concerning positron production: Here is the research paper. Scientists used a laser that spreads over multiple rooms to produce 100 billion positrons, annihilating them will release 0.016 J. The laser can probably produce a few shots per second. And even if it could produce more: They need about 60 GeV laser energy per positron/electron pair produced. That is an efficiency of 0.0016%. I didn't find numbers for the laser efficiency, but those pulsed lasers are probably below 1% efficient. Your overall efficiency of electricity to energy released in positron annihilation is now 0.000016%. And where is the point? We still have no connection between positrons and fission.

Do you see the problem? Science is not about randomly mixing concepts. It is about coming up with a plausible mechanism how X can cause Y, and then calculating if that looks reasonable quantitatively.
 

FAQ: Fission caused by positrons - in a fission fragment rocket?

1. What is fission caused by positrons?

Fission caused by positrons is a process in which a positron, a positively charged subatomic particle, collides with a heavy nucleus, causing it to split into smaller fragments. This process is similar to traditional nuclear fission, but instead of using neutrons, positrons are used to induce the splitting of the nucleus.

2. What is a fission fragment rocket?

A fission fragment rocket is a type of propulsion system that uses the energy produced by fission reactions to propel a spacecraft. In this type of rocket, the fission fragments, or the smaller nuclei produced by the splitting of a heavy nucleus, are ejected at high speeds to generate thrust and propel the spacecraft forward.

3. How does fission caused by positrons work in a fission fragment rocket?

In a fission fragment rocket, positrons are used to trigger the fission reaction in a heavy nucleus, such as uranium or plutonium. As the nucleus splits, it releases a large amount of energy, which is used to heat a propellant, such as hydrogen, and create a high-speed jet of fission fragments. These fragments are then directed out of the back of the rocket, generating thrust and propelling the spacecraft forward.

4. What are the potential benefits of using fission caused by positrons in a fission fragment rocket?

Using fission caused by positrons in a fission fragment rocket has several potential benefits. Firstly, this type of propulsion system can generate higher thrust compared to traditional chemical rockets, allowing for faster and more efficient space travel. Additionally, fission fragment rockets have a higher specific impulse, meaning they can produce more thrust using less propellant, making them more cost-effective for long-distance space missions.

5. Are there any potential risks or concerns associated with using fission caused by positrons in a fission fragment rocket?

While fission fragment rockets have many potential benefits, there are also some risks and concerns associated with using fission caused by positrons. One major concern is the potential for radioactive contamination if there is a malfunction or accident during a space mission. Additionally, the development and use of this technology would require strict safety protocols and regulations to prevent any potential dangers to human health and the environment.

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