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).

[David L Pulver]

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.

If the assumptions are correct, then increasing the exhaust velocity as specified would approximately double the Isp (and in Spaceships give a value of about 6600 mps per fuel tank, I guess).

I'd think increasing the exhaust velocity would quite likely reduce the acceleration, though, by at least half and possibly more. (High-impulse antimatter pion rocket?)

On TL, while making antimatter is a big problem, it can be dealt with with appropriate engineering projects (cover mercury with solar collectors, whatever). But the biggest problem is the storage of antimatter.

A pion drive relies on 1-1 ratio mix of matter-antimatter. However, storage facilities for antimatter currently mass a great deal to hold even sub-nanogram levels, and even the future generation versions quoted are things like "mass of a space shuttle tank to hold a few micrograms."

Since half your fuel is antimatter, if your fuel tank ends up weighing vastly more, or even a little more, than your fuel, you are utterly out of luck. You'll have to get the fuel tank mass from a future speculative "tons per microgram"
down to "micrograms per microgram" if you don't want your starship to have the acceleration of a flashlight. (There are possible ways to do this, maybe, like antihydrogen ice storage, but the road to them is probably TL10+).
.
Also, it's not just the storage - you have to find a way of moving the antimatter from whatever tank you have to the engine, which means the engine has to incorporate this technology. The most sensible approach I saw had the antimatter hydrogen stored as solid pellets and the hydrogen liquid.

(Incidentally, while the 3e version was TL9 - but in 3e TL scale. Most 3e technologies specified as TL9 became either TL10 or TL11 in 4e (blasters, for example)).

[Trachmyr]

@ David Pulver: So when's the next Spaceships book coming out ;-), I got the $$ right here!

Seriously, I would love a Spaceships treatment on Current & Expected Tech in the next few decades, and fiddly numbers on things like Vasmir, M2P2, NERVA/LANTRN... broken down in Experimental through Mature TECH crunchy numbers.

Anyways, got the $$$ right here... just sayin' :)

[dataweaver]

That strikes me as being in the domain of the Vehicle Design System rather than the Spaceships series.