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."

Comments

Expensive to produce

[rssc]

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...

hard to make

[n0mad6]

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).

Re:hard to make

[n0mad6]

I wanted to add this.

Re:so much stupidity

[imsabbel]

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...

Re:But, if I give'r any more she'll explode!

[iced_773]

Here

Whenever I need to know something, I just check Wikipedia.

Storage, not production, is the problem

[pfdietz]

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.)

Re:Scotty, we... need... more... power!

[zzz1357]

In 1865, Stanley Jevons argued that Britain would run out of coal in a few short years' time. In 1914, the US Bureau of Mines estimated that supplies would last only 10 more years.

In 1939, the US department of the interior predicted that oil would last only 13 more years. In 1951, it made the same projection: oil had only 13 more years. As Professor Frank Notestein of Princeton said in his later years: "We've been running out of oil ever since I was a boy." Regular gasoline costs the same in real terms as it did in 1950. In the 1960s overpopulation was going to cause massive worldwide famine around 1980. A decade later we were being told the world would be out of oil by the 1990s.

I have this sinking feeling that in 20 years, someone will post on /. that "the crude oil reserves will be exhausted in about 20-30 years."

Re:Scotty, we... need... more... power!

[zerus]

The reactors used on submarines are a very special case though. Firstly, they use highly enriched which isn't good for public consumption because runaway reactors with HEU would be very, very bad. Second, since a submarine has the requirement that is has to go from no power to full power in seconds, it has a very, very, very large, active neutron source (on the order of a few curies if memory serves correctly, but it's been quite a while since I worked on anything nuclear that ran on earth ;-) ). The k-effective of a nuclear sub that isn't "on" is usually at about .90~.95. Which means that all it needs is to remove the control rods ever so slightly to start producing power. Also the cooling mechanism of nuclear subs uses seawater as a secondary coolant since it's so abundant. The primary coolant doesn't leave the core obvious, but it's the secondary which directs where that heat will go. So for a small scale reactor, this isn't the way to go, but more towards an RTG, which is what's used in satellites. They aren't exactly small, but they run on the Seebeck effect (reverse of the peltier effect for you computer people). The fuel in an RTG doesn't create the heat/energy by fissioning, but rather by natural alpha decay (heavy,unstable isotope releasing ionized helium atom). The helium atom has a certain amount of energy, usually in the 5+MeV range since the fuel is usually a plutonium isotope. So with that amount of energy being released at a near-constant amount for 25+ years, the benefit would be great; however, shielding and non-proliferation issues persist and render using this as a mainstream, use-at-home reactor as impossible. But one of the things beind worked on by the IAEA along with a few of the US nat'l labs and other is a large RTG that can be safely deployed to areas to use as a portable power plant. It'd be cool, but huge, and expensive until better materials are worked out for shielding.

Re:Bad math!

[Johnno74]

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.

Re:But, if I give'r any more she'll explode!

[AKAImBatman]

There are a couple of ways it could be useful:

1. Nuclear Steam Ships can have a relatively high Isp (compared to chemical rockets) while using a fuel that's easily obtainable from a nearby body such as the moon.

2. Magnetoplasmadymanic thrusters are based on MHD theory, and have some of the HIGHEST Isp of any rocket engine. In addition, they have a relatively high thrust to weight ratio as well. (Very rare in engines with such a high Isp.)

Re:zero-point energy no chance!

[exp(pi*sqrt(163))]

BTW, purely empty space is not empty. there are constant creations of particles and their anti particles (thus servicing thermodynamics) popping in and out of existence in empty space. this causes a pressure to form and this pressure causes a force which can be used to extract energy

You know physicists read /. too? Don't you feel embarassed about what you just wrote?

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.