Can anti-hydrogen spacecraft explosions be safely contained?

[plum]

How could the explosion (re: http://arxiv.org/abs/astro-ph/0410511 ) be contained/ funneled out (without blowing up the actual spacecraft )?

 

[russ_watters]

Well, I'm not exactly sure what a matter-antimatter explosion looks like - an extremely high energy black-body? Just plain gamma rays?

Basically, you just make the explosion happen outside the ship and use a shield to reflect the energy away from the ship, driving it forward.

 

[Clausius2]

Well, I'm not exactly sure what a matter-antimatter explosion looks like - an extremely high energy black-body? Just plain gamma rays?

Basically, you just make the explosion happen outside the ship and use a shield to reflect the energy away from the ship, driving it forward.

I thought that the Antimatter-Matter reaction occurs inside a chamber, and the heat released heat up in some way a gas which is ultimately exhausted by a nozzle. But I am not sure.

 

[Astronuc]

How could the explosion (re: http://arxiv.org/abs/astro-ph/0410511 ) be contained/ funneled out (without blowing up the actual spacecraft )?

The energy release rate (power) depends on the rate of antimatter-matter annihilations. By controlling the release (current or flow rate) of anti-protons from whatever trap (storage system) which contains the Bose-Einstein Condensate (which is discussed in the paper), the reaction rate is controlled. Afterall, the title of the paper is "Controlled Antihydrogen Propulsion . . . ".

One annihilation will transform the rest mass of proton and anti-proton pair (2 * 938.27 MeV = 1.8765 GeV) into other charged particles, namely pions (2 * ~139 or 2 * ~134 MeV), but possibly Kaons(2 * ~494 MeV), and both types of mesons decay. Presumably, the anti-protons will be close to rest, i.e. not accelerated appreciably.

Suppose the annhiliation produces recoverable energy of 1 GeV (1.6022E-10 J) per annihilation. Consider that the annual production rate is on the order of 1014[/url] anti-protons, which means about 16 KJ of stored energy is produced per year, and this excludes losses during the deceleration and storage. One then must ask, what amount of energy is necessary to accelerate a spacecraft to 0.10c, for example.

The reaction chamber will presumably be magnetically confined to direct the annihilation products in the opposite direction of the rocket trajectory. More than likely, the anti-protons will be directed into an excess of protons, e.g. hydrogen. This will dilute the energy production, so the claims of 3 orders of magnitude (per nucleon) greater energy release as compared to fission, while true, are somewhat misleading - there is more to it.

For a reasonably good paper on p \bar{p} interactions, see - http://arxiv.org/PS_cache/hep-ex/pdf/9708/9708025.pdf

For a reference on Anti-Matter Propulsion, see http://www.transorbital.net/Library/D001_S01.html

We estimate that, starting with the present level of knowledge and multi-agency support, the goal of using antihydrogen for propulsion purposes may be accomplished in ~50 years.

That's what some fusion experts said about fusion.

 

[izzie]

now, i am dull but explain this to me. how is this idea feasable, isn't our universe constructed of matter and darkmatter, so how are we possibly ever going to be able to contain anti-matter. the only way would be to somehow create anti-matter right "on the spot".

 

[professor]

antimatter can be created...on the spot...and has been, this has been done using an electron accelerator in a vacuum, smashong electons togther until they split them selves up and start creating little bits of anti matter basically...anyway, these bits are then manipulated with magnets in a vacuum again, into small vaccumed magnitised chambers, where they are removed from all non-anti matter. also there is a theory that the inverse of a swarzchild black hole of which you spoke of earlier could contain some sort of gate through a singularity allowing antimatter to exist in great quantities, without on-the-spot creation...and correct me if I am wrong, but i believe this is a valid explination. ( i think its spelled swarzchild...)

 

[izzie]

thanks for that - still think if they do do it it will be catastrophic

 

[professor]

yeah, there is a real possibility for extreme danger, as well as potential energy...definetly

 

[professor]

ohh.. and as far as directing the explosion out of the craft i have heard of cooled niobium being used as a superconductor to direct such things...this (or a similar means) may be used in the outward direction of the annihilation process (the niobium allows a charge to pass through it, shooting the antimatter out of a vacuumed chamber, and into somewhere it can annihilate ( a strong, possibly mirriored chamber before where the muffler might be) in this chamber hopefully, an equal piece of matter could be propelled (on a path of similar in velocity to the antimatter) that would connect to the antimatter and then release the energy as mainly light, or in this case a hydrogen atom or two, and some light).

 

[plum]

Apparently, we may someday be able to send antimatter powered probes costing billions if not trillions of dollars to interstellar destinations, but barring miraculous technological breakthroughs for creating and then storing tons of antimatter, using it for manned interstellar travel will be impractical for the foreseeable future. It's far too expensive to create and far too hazardous to store (if copious amounts can be created) in significant quantities. Also, once the mass of the propellant becomes larger than the mass of the craft, the fact that the propellant has to push it's own mass leads to an asymptotic energy function that no amount of mass in the universe can overcome. This, at least, is according to what I've learned and understood so far. I'd still like to expand this discussion if anyone thinks that it can offer hope for long-term interstellar travel.

 

[Danger]

barring miraculous technological breakthroughs for creating and then storing tons of antimatter, using it for manned interstellar travel will be impractical for the foreseeable future.

It's pretty much the only practical means of interstellar travel if you want any significant thrust. (Ion propulsion is far more efficient, but gives a very low impetus. It's still a better bet in the long-run, though.)
As for the amount of antimatter needed, do you really have any concept of how powerful this stuff is? Annihilation of matter and antimatter is 100% energy conversion. Hydrogen fusion, in contrast, is somewhat less than 1%. One half gram of antimatter reacting with one half gram of matter releases 25,000,000 kilowatt-hours of energy. For a trip that will primarily be ballistic, you don't need tons of it.

 

[plum]

As for the amount of antimatter needed, do you really have any concept of how powerful this stuff is?

Yes, I do. At a speed of .1c, approximately 250,000 kg of antimatter would be required to get to the nearest star, at a cost of $625 trillion. Total Kinetic energy: 2.26 X 10~22 Joules. Do some more research before you disagree.

 

[Danger]

Do some more research before you disagree.

Nothing in my arsenal can read the link that you posted, but I would certainly suggest that you study up on 'Ion Compressed Antimatter Nuclear' propulsion as is being developed at the Pennsylvania State University Center for Space Propulsion Engineering in association with the Marshall Space Flight Center. You'll see that the proposed mission requires less than 10mg of antiprotons for a trip to Barnard's Star.

 

[Astronuc]

This is a bit dated but I just found it.

HOW TO BUILD AN ANTIMATTER ROCKET FOR INTERSTELLAR MISSIONS

SYSTEMS LEVEL CONSIDERATIONS IN DESIGNING ADVANCED PROPULSION TECHNOLOGY VEHICLES

http://www.aiaa.org/Participate/Uploads/2003-4676.pdf

 

[LURCH]

As far as generation is concerned, it will be a long time before we can produce and store antimatter in appreciable quantities. In the distant, future, we learn harvest it from stars. A couple years ago, I read an article stating that some form of solar disturbance (a flare, I think) had produced more than a pound of antimatter in just a few moments.

 

[Danger]

Wow! I never heard of that one before, Lurch. Can you manage to remember where you read it? (That's not an insult, by the way; I can almost never do that.)

 

[LURCH]

LOL! Well, I Google^TM Searched it, (Solar flare antimatter), and turned up a conversation right here in the Forums wherein I had posted this link to the story at NASA.Gov...

http://www.nasa.gov/centers/goddard/news/topstory/2003/0903rhessi.html

...the post was from 2003!

Ah, good times!

 

[LURCH]

Oh yeah, and here's the thread...

https://www.physicsforums.com/showthread.php?t=9122

 

[Danger]

Fascinating. Thanks, Lurch