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NASA to Research Antimatter Rocket
Fraser Cain writes "One of the dozen technologies selected by NASA's Institute for Advanced Concepts (NIAC) this year is Positronics Research's ideas for an antimatter rocket engine. Instead of 3100 kg of propellant on board Cassini, the spacecraft could get by with just 310 micrograms of electrons and positrons. Of course, making the antimatter can be expensive."
But seriously folks...
Many of our upcoming challenges both earthbound and space bound relate to the safe, efficient, portable, and inexpensive generation of HUGE amounts of power. Whether it's antimatter, zero-point energy, fusion, whatever, let's get something off the drawing board and into service.
My laptop is more powerful than a 1975 supercomputer that filled a room, but a D cell battery hasn't changed its size in 30 years and today's best D cell lasts what 2, 3 times as long as one from 1975? We're still running coal-based and oil-based power plants that were built in the '70s. Is everything shooting along while power generation creeps?
Start a happiness pandemic
One of the major problems with antimatter is that you need to be able to contain it very very securely. The actualy weight of the antimatter may be substantially less, but the whole infrastructure to create it and contain it is going to be considerably more complex and expensive.
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According to the Wikipedia producing antimatter is quite expensive. They mention something of $25 billion per gram.
That's around $7'750'000 for these 310 micrograms...
Work out the chemistry on it. The simple truth is that unless there is a fundamental change in energy density of chemical reactions, there just isn't a lot more to ask of chemical storage. That's why there is the shift towards "power generation." This is really just a fancy term for changing from where there is a chemo-eletrical differential (i.e. positive/negative sides) to actively causing a chemical reaction that provides electricity; however, there are two problems with this approach. First, it is usually easier to ask the device to use less power. Second, power generation at a minimum produces heat, sometimes violently and excessively. Batteries are nice because they are generally quite safe, reliable, and (most importantly) currently mass-produced.
On a side note, super atoms seem to be a possibility on "rewriting" our understanding on chemical reactions.
Bel, the mostly sane.. "Of course I can't see anything! I'm standing on the shoulders of idiots." -- Me
Without so much more technological breakthroughts (who will of course make that whole project pointless, because totally new options would arise), building a antimatter rocket will be impossible.
First: containment-> Its hard getting long livetimes in a nice good storage ring that doesnt suffer massive accelerations and other nasty stuff launching from earth brings with itself.
Second: containment part two: To power it, you would need a energy source of such capacity that could feed an ion drive or equivalent just fine without the need for antimatter.
Third: containment part three: if it fails it will give the a real nice flash. ok, with such a small one this doesnt matter (a normal rocked exploding is also devastating, but a bigger one would be like a nuke on steroids).
Fourth: Production of anitmatter: current efficiency of antimatter creation is somewhere around absolute zero... dont know the the exact numbers (the article was a few years old), but with current technology it could very well take the energy production of the whole USA to create that much anitmatter... for a year or so...
All those points dont mean that it wont be possible (or even desirable) to build an antimatter engine, but the needed advancements are THAT far away, that every kind of basic studies now are pointless.
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
I like the idea of trying to push along basic research with incentives.
I think they're called 'grants'.
Speaking as someone who uses antimatter every day, I have to point out that at least now, antimatter is very difficult to make. We expend 100,000 protons (ones that have been accelerated to very high speeds) to make one anti-proton. They get "stored" in a large accelrator complex underground (much bigger and bulkier than a spacecraft). After about half a day of this, we produce about a hundred thousandth of a microgram of antiprotons (which we then smash the hell out of).
Humans like to find new territory and conquer it. We currently have exhausted the Earth's surface, except for the submerged and frozen parts. So we have to go somewhere.
That said,
Space propulsion may end up being a two-fold operation, with a rocket or rail gun used to break free of the earth or moon's gravity well and a deep-space propulsion unit used for the long haul.
Something like a solar sail or ion drive might fill the bill. An ion drive is relatively inexpensive, but doesn't give much push. If a chemical rocket or magnetic accelerator gets you started, an ion drive could work nicely.
You still need "HUGE" amounts of power for a rail gun or rocket, though.
Feel free to ignore the above. I'm just waiting for an rsync to finish so I can shut down the old server and go home.
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The upper end of your scale, 5 kg, amounts to E = m * c^2 = 5 * 9e+16 = 4e+17 Joules.
The Russian Tsar Bomba ---the World's largest nuclear weapon ever detonated on Earth--- yielded 50 Megatons of energy, or about 50e6 * 4e9 = 2e+17 Joules.
That bomb didn't kill us, so 5 kg of antimatter won't kill us all.
To put things in perspective, the Hiroshima bomb (15 kton) destroyed about 1.5 grams of matter. The Tsuami quake on the Pacific, last year, yielded about 30 Gigaton, or 6.4e+19 Joules. That amounts to about 600 to 700 kg of destroyed matter.
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Hold your horses...
You dont seem to know your physics THAT well..
First: 5g antimatter wont destroy the earth. In fact, it would be more like a medium sized hydrogen bomb-> it doesnt even make dent in any bigger mountain.
Second: Antimatter is a storage only device. Every bit of energy created by a detonation has to be produced by other means, first (in fact, 1000 times or more, because of abysmal efficiencies). So to even have the _possibility_ of creating planet_buster or armageddon-device amount of antimatter, you need energy sources that could do it anyway...
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
The posters here missed the mark.
Making positrons is actually much easier than making antiprotons. Pair production on photons produced in accelerators should give efficiencies of 5 to 10% -- and the positrons are much easier to cool.
The big problem with positrons is storing them. Unless these people have a major new idea to get around the Brillouin limit on Penning Traps, the energy stored per mass of equipment will be too small to be interesting (even worse than the energy/mass of chemical propellants.)
nope - you're using grams, not kg, making you 1000x out. its 5*c^2, not 5000*c^2
As someone else on this thread has pointed out, you actually have do double that, because 5kg of normal matter is destroyed as well.
But from the link that someone else provided (http://en.wikipedia.org/wiki/Antimatter_weapon) 60% of the yeild of an antimatter explosion escapes as neutrinos, and most of the rest as gamma rays so its not nearly as dangerous (or practical, if desctruction is your goal...) as a regular H-Bomb.
After years of thinking I knew rocket propulsion -- via SF novels and popular works and, well, building small ones -- I took a policy course on space travel at CMU. Professor Morel (sp?) insisted that we learn the science first. I got all sorts of good stuff, and started poking around the engineering library for more.
I found, while researching my term project, a great book on advanced propulsion topics. This wasn't some popular work, but a collection of hard-core equation-filled research papers. There was stuff on what could be the next generation of fission drives, various fusion drive concepts, and antimatter propulsion.
Beyond the obvious containment issues, there is a BIG problem with antimatter propulsion:
The problem of opacity.
Antimatter / matter reactions produce gamma rays. These are extremely energetic and readily penetrate many materials.
This means that they are very inefficient when it comes to heating up a working fluid. The detail -short linked-to article glibly talks about shooting gamma rays into propellant. They will heat up the hydrogen or water or whatever you are using for a working fluid, but a lot of the energy will simply keep on going, and whiz right through the outside wall of the "combustion" chamber.
The one research paper which described a "pure" antimatter rocket heated the propellant indirectly. The positrons would be shot into a block of tungsten alloy dense enough to intercept an appreciable amount of the energy produced by the matter / antimatter reaction. Working fluid passed through channels in the block would heat up, turn to gas, and produce thrust.
The rated Isp was, as I recall, about 5,000 seconds. This is way more than conventional fluid / chemical rockets (500 seconds) and fission rockets (1,000 seconds) but only a little higher than existing ion thrusters (3,100 seconds for that solar-powered testbed that ran a few years back).
The one advantage this rocket would have over ion thrusters would be the amount of thrust. Ion rockets produce just a trickle of thrust. The antimatter thermal rocket would probably produce a fair amount of thrust, although probably not enough for a ground-to-orbit booster.
Stefan
Look, physicists have this notion of a vacuum state. It's the lowest energy state a system can occupy. You can't extract energy from a vacuum state because then it would be left in a lower state contradicting the fact that it's a vacuum state. So it doesn't matter if a vacuum state has cocktail sipping blue-tongued skinks materializing out of nothing. You can't extract energy from it.
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