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I was excited to read several articles about experiments generating anti-matter (production from gold or helium) at what seemed like a rather low energy cost. I thought anti-matter generation was the biggest obstacle to the development of things like pion rockets or other anti-matter-dependent propulsion/power generation devices, however, I didn't see any resurging interest in designing such things and no one seemed particularly excited. Did I misunderstand the importance of these findings?

I've considered the following reasons why these experimental methods might not be useful, and I'd appreciate your input:

  1. Positrons aren't useful, we need antimatter with mass (antiprotons), and these methods cannot be used to generate these
  2. Energy cost is still significantly higher than potential energy yield
  3. Supporting system requirements are still beyond our technical capabilities
  4. These methods still generate amounts far smaller than what would be required to propel theoretical antimatter drives
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  • $\begingroup$ Great question for a new user! It is a challenge to ask an evidence-based question about such speculative technology as anti-matter drives. I hope we get some good answers $\endgroup$ – called2voyage Apr 29 '16 at 1:40
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There are proposed thermal antimatter rocket designs which could work with positrons. I am focusing on these to answer your questions (in reverse order):

  1. The amount of energy generated is (more or less) an engineering problem. Assuming that asteroid mining is feasible, there is no principle limit to scale these operations. Since antimatter is the fuel for a rocket (think of hydrogen in electrical cars), conversion efficiency is "merely" a cost factor.
  2. Indeed this is the major obstacle IMO. The more efficient (liquid or gaseous core) designs of a nuclear fission rocket are already quite beyond our current capabilities. Not to speak of the ambitious plasma core design of an antimatter rocket. Simpler designs yield considerably less ISP and are probably just not worth the effort (of generating the antimatter).
  3. See answer to your last question.
  4. In fact, positrons can be useful. There is no principle reason you could not heat your propellant with them as well. However, positrons are hard to store. Current research is ongoing, but with the cited capacity of 10¹² positrons per trap, you'd end up (with 1.6MeV per annihilation pair) with (roughly) 0.16J per cm³ trap volume. That means you can store the energy to heat 0.16g of water by 0.24K. Not quite a rocket. If you store antihydrogen however, you can not only increase your storage capacity by a factor of 10³, but also relase 10³ times the energy by annihilation (1.8GeV, not counting secondary reactions). This gives you a potential energy of 160J per cm³ trap volume. Bringing a ship to orbit requires (just an estimate) 10¹²J. So you'd end up with 1000m³ volume for fuel!

The bottomline is: You need too much volume to store the antimatter in your spaceship (at least with current storage capacities).

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While it's theoretically possible to use anti-matter, the engineering is just not there.

I recently attended a lecture on nuclear fusion, and the gentleman giving it stressed more than once how difficult is to take something from theoretically possible to real world possible.

We've known fusion to be possible since the 1920s and we still don't have fusion reactors. It's the same with anti-matter. It has no practical applications and it will probably be another 100 or more years before we are anywhere near using it in any practical sense.

Maybe that could change if we make science a priority, but somehow I don't see that happening any time soon.

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    $\begingroup$ Hello Ventsyv, Thank you for your answer, however, I was not proposing that anyone was going to build an anti-matter based system anytime soon, rather I was wondering why no one seems to be trying to design more than a highly theoretical model for one. If I understand where the field is, we know we can make anti-matter (or maybe not the interesting type, I don't know), and I was wondering if no one was pursuing it further due to some technological limitation or some similar issue $\endgroup$ – Ofer Baratz Apr 29 '16 at 3:24
  • $\begingroup$ I believe if antimatter work in reverse then photons emitted from normal matter would destabilizes it. If a photon spun in the opposite direction from anti matter could we actually tell or still see it? $\endgroup$ – Muze the good Troll. Dec 30 '16 at 23:24

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