TL9 Antimatter pion rockets

[thrash]

http://www.technologyreview.com/blog/arxiv/27847/
http://arxiv.org/abs/1205.2281

Beamed Core Antimatter Propulsion: Engine Design and Optimization
Ronan Keane, Wei-Ming Zhang

A conceptual design for beamed core antimatter propulsion is reported, where electrically charged annihilation products directly generate thrust after being deflected and collimated by a magnetic nozzle... The main finding is that effective exhaust speeds Ve ~ 0.69c (where c is the speed of light) are feasible for charged pions in beamed core propulsion, a major improvement over the Ve ~ 0.33c estimate based on prior simulations... Moreover, this improved performance is realized using a magnetic field on the order of 10 T at the location of its highest magnitude. Such a field could be produced with today's technology, whereas prior nozzle designs anticipated and required major advances in this area. The paper also briefly reviews prospects for production of the fuel needed for a beamed core engine.

This paper seems to suggest that non-superscience antimatter pion rockets are possible at TL9. Would David Pulver or one of the original playtesters be able to comment on whether the Isp would improve as well?

Of course, antimatter production is always the most difficult part of this technology. Even so, this points to the possibility of hard sf interstellar missions much sooner than previously thought.

[Fred Brackin]

Originally Posted by thrash

http://www.technologyreview.com/blog/arxiv/27847/
http://arxiv.org/abs/1205.2281

Beamed Core Antimatter Propulsion: Engine Design and Optimization
Ronan Keane, Wei-Ming Zhang
This paper seems to suggest that non-superscience antimatter pion rockets are possible at TL9. Would David Pulver or one of the original playtesters be able to comment on whether the Isp would improve as well?

Of course, antimatter production is always the most difficult part of this technology. Even so, this points to the possibility of hard sf interstellar missions much sooner than previously thought.

Antimatter pion was listed at TL9 in Ve2. David would have tyo say why it's a TL11 tech in Spaceships.

At a guess it might have been the antimatter storage. I don't think the non^ numbers used in UT are that friendly to storage of large quantities of antimatter and I beleive it to be a very significant problem in the Real World..

The distinction between superscience and non wasn't as formal in 3e but antimatter pion was generally considerd hard science in 3e to the best of my memory.

The technobabble in Spaceships describes the exhaust as "near light speed" so no, there'd be no real imporvement over that.

The babble in Ve2 is less specific but I never heard that apion exhaust wasn't goign to be near c so that .33 C simulation probably missed the Gurps community even if it was contemporaneous with Ve2 and/or Spaceships

That said, I haven't reverse engineered the Isp used in any Gurps books.

[Anthony]

Originally Posted by Fred Brackin

Antimatter pion was listed at TL9 in Ve2. David would have tyo say why it's a TL11 tech in Spaceships.

I believe the TL 11 part is having sufficient quantities of antimatter, with low enough storage mass, to make antimatter-pion remotely useful.

[thrash]

Originally Posted by Fred Brackin

The babble in Ve2 is less specific but I never heard that apion exhaust wasn't goign to be near c so that .33 C simulation probably missed the Gurps community even if it was contemporaneous with Ve2 and/or Spaceships

That said, I haven't reverse engineered the Isp used in any Gurps books.

The effective exhaust velocity for the antimatter pion rocket in Spaceships appears to be 0.35c, which is consistent with previous state of the art. That is, the exhaust particles themselves may be "near c," but the inefficiencies in focusing the stream lead to the lower effective velocity.

Taken with the results of the paper cited above, this implies that a delta-V of 6700 mps per tank may be possible.

Originally Posted by Anthony

I believe the TL 11 part is having sufficient quantities of antimatter, with low enough storage mass, to make antimatter-pion remotely useful.

"Tank" mass is a valid concern. For the rest, however, hideously expensive is not the same as impossible. Unless the technology to create antimatter improves at higher tech levels (which isn't indicated by, e.g., the Reaction Mass Cost Table), the only improvement in cost from TL9 is relative to the greater overall wealth at TL11.

[Langy]

Tank mass isn't just a valid concern - it's what makes the antimatter engines in Spaceships completely and fully superscience, rather than anything even resembling realistic. You'd need magic fields that can hold antimatter without utilizing any actual mass in order to get the efficiencies listed in Spaceships.

[Flyndaran]

Even super advanced production facilities keep antimatter so expensive as to be useless for nearly any plausible ship even without taking storage difficulty into consideration, in my opinion.

[Sunrunners_Fire]

Originally Posted by Flyndaran

Even super advanced production facilities keep antimatter so expensive as to be useless for nearly any plausible ship even without taking storage difficulty into consideration, in my opinion.

Well ...

1kg of anti-matter should produce about 9E16 joules. One sun-second (assuming Sol) is 4E25 watts. I suspect one sun-second would produce quite a lot of anti-matter (nearly 450 million kilograms of the stuff at perfect efficiency if my notes are right).

[Flyndaran]

So you imagine a Dyson sphere's output, if even for only a couple of seconds, to power one antimatter's worth of ship fuel?

Well, that is one way to spread to the stars.

[lexington]

Originally Posted by Sunrunners_Fire

Well ...

1kg of anti-matter should produce about 9E16 joules. One sun-second (assuming Sol) is 4E25 watts. I suspect one sun-second would produce quite a lot of anti-matter (nearly 450 million kilograms of the stuff at perfect efficiency if my notes are right).

Yes, if you trapped 100% of the energy coming out of the sun and turned it into anti-matter with 100% efficiency you'd have a nice supply. You'd also be extremely far into TL11, probably TL11^.

I'll try to make things more reasonable. Lets say you make the machine a disk as wide as the Earth. Now you collect 4.3e-10 times as much energy. I believe the most efficient way to make antimatter from pure energy is by causing pair-production, which should be limited to an absolute limit of 50% efficiency. So you could make .1 kg per second or so. That's fast enough to fill up the smallest possible tank in Spaceships in around four hours.

[Sunrunners_Fire]

Originally Posted by lexington

Yes, if you trapped 100% of the energy coming out of the sun and turned it into anti-matter with 100% efficiency you'd have a nice supply. You'd also be extremely far into superscience territory.

Trapping the entire solar output isn't super-science. Its' a high-TL thing, as any other mega-structure project is, but it isn't super-science.

Doing it with a 100% efficiency is super-science, I agree. Adjust the unrealistically optimistic numbers downward; I don't have enough information at my disposal to figure out what a realistic efficiency would be ... as such, adjust the numbers downwards as you feel appropriate. :grins:

My point was that advanced production facilities can produce antimatter in sufficient quantities to make an antimatter rocket viable.