Slashdot Mirror
Antimatter Space Drive
sckienle writes "Space.com has an article on using anti-matter for propulsion in space. It isn't true Star Trek warp stuff, in fact it is a variation on an fusion based pellet design I saw in the late 70's, but interesting concept. The concept is still somewhat of a dream, as stated in the article: 'The real hub is the storage [of antimatter]. There's a lot of technology between here and there.' Later on it also mentions that we can't produce a lot of antimatter efficiently yet. Still it might be worth the effort if the theoretical acceleration proves out." The BBC has a story about studying antimatter in a lab.
I don't think anyone is arguing that antimatter would be just unbelievably useful to spacecraft, but the cost needs to be taken down by something like nine orders of magnitude -- the currently going rate for antiprotons is something like a million dollars per nanogram.
The cooling ring only helps you once you have antiprotons to cool down to antihydrogen. Right now the production of antiprotons itself is just too expensive.
Would it kill them to be a little more precise on:
- the distance from the Sun to the Oort cloud (about 250AU)
- the distance from the Sun to Pluto (about 40AU)
- the ratio of those two distances (apparently about 5)
?--
E_NOSIG
This is the basis for the "containment field" of Star Trek fame.
In a DS9 novel, they talk about transferring antimatter between holding tanks by using tightly confined magnetic field beams and piping the antimatter through their magnetic pipes from one place to the other.
Any physicists out there? Why is antimatter so hard to produce? What I know about the matter is limited to the following - (please correct me if you have the appropriate knowledge)
1. The amount of antimatter currently visible in the known universe is negligible compared to the amount of matter.
2. However, in the big bang, antimatter and matter are supposed to have been created in equal amounts. So where did antimatter go?
3. QED equations for antiparticles are exactly the same as those for normal ones if you reverse the direction of time.
The only conclusion that *I* can draw from this is that there is no antimatter left nowadays because it is travelling in the opposite direction in time, whatever that means.
That in turn gives a simplistic explanation of why it is hard to create antimatter - there is no causal relationship normally. According to my weird intuition, you can only create antimatter in a material universe by violating 'normal' causality.
PS. I am *not* a physicist.
I miss my rubber keyboard.(Homepage)
No.
The protons and antiprotons would react, producing two photons. Figure out how to reflect the gamma rays in one direction, and the ship will be accelerated in the other direction. Light has momentum (E=pc).
This is why they are using a sail on this design. Spread the reaction out over a large surface and the the radiation intensity won't be as bad.
CfkRAp1041vYQVbFY1aIwA== RV/hBCLKKcSTP5UFK3kqsg==
Last time i checked, it took megawatt-hours of electricity and an expensive atom-smasher to make one microwatt-hour worth of antimatter. Without a fantastic advance in antimatter production technology, talking about *any* use for non-microscopic quantities of antimatter is just blowin' smoke.
It would be workable to pump the megawatts into a bank of lasers and let the lasers push on the probe's small light sail. (And you could tap the military budget for a good hunk of the cost of those space-based laser batteries.)
It's easy to make up & spread cool- and credible-sounding stuff. Finding & checking hard facts is hard work.
Nothing so interesting, IMHO -- it's just a garden case of someone not reading what someone else said very carefully, or possibly not understanding it well. <wry grin>
A scientist or engineer who claims that there is a "lot of technology" between here and there is merely saying that we can't do it now, with today's technology. Given the rate of change in technology over the past hundred years, saying that something can't be done today is hardly the same as saying it can't be done at all.
While no physicist expects Star Trek-like warp drive any time soon (or at all), we've known that anti-matter exists since the late 1920s, when Paul Dirac developed the equations that showed that it had to exist. We first "saw" real anti-matter in the mid-1930s, when Carl Anderson observed a positron, or anti-electron. Both of these men won Nobel prizes for their work -- this is not exactly news to anyone who keeps up with science and especially physics.
Antimatter isn't the brainchild of some writer with lots of imagination and little grasp of science. It exists. It is real. Further, its properties are widely understood -- we know how it behaves.
More to the point, we know that, to produce and keep large quantities of it, we must determine how to isolate it from regular matter. We know that, to use it in an engine, we must expose it to regular matter in a controlled fashion, and harness the energy released when it and the regular matter annhilate each other.
In other words, we already have the basic science in hand. What we haven't figured out yet is how to do what needs to be done economically and reliably -- we don't have the technology in hand.
This doesn't sound impossible to me. It sounds like it will take time and effort, probably quite a bit of time and effort, but as technology goes it isn't sufficiently advanced to be indistinguishable from magic. (Five mod points to anyone who identifies that reference.) ;>
Catherine
...it would seem to me that they have the right idea. They used a crystal of sorts(dilithium) to regulate the matter/antimatter reaction. Here's the reality check:
Since matter/antimatter reactions cause 2 gamma-frequency photons to be thrown off at right predictable angles to the impact vectors of the original matter and antimatter particles, an engine could be designed that ensured that one of the 2 photons always exited from the engine exhaust port to propel the ship. What of the other one? Position a crystal in the appropriate location to catch the second photon. Depending on the structure of the crystal, the result would either be mechanical (heat or vibration) or electrical energy which could be converted and/or stored as needed.
Here's what he said so you don't have to click the links
Voyager is not travelling all that fast, and we could go faster with sufficient time and engineering effort.
First cab off the rank is probably the Orion drive. Build a really big plate, attach it with really big springs and dampers to a heavily radiation-shielded spacecraft, and detonate atom bombs behind the plate. The basic technology exists right now, all you need is a pile of cash and be prepared to violate the space weapons treaty. Maximum speed is about 1-2% of the speed of light, so you're still taking a couple of centuries to Proxima Centauri.
Next option is a fusion engine. We can't generate power with controlled fusion yet, but ITER probably will if and when it gets built. ITER is, er, rather large and heavy, and doesn't really produce much net power, so a practical space fusion power plant is a fair bit of engineering development down the road. Anyway, the idea is quite simple. Release the "exhaust" of the reaction out the back of the engine, just like a normal rocket except the exhuast is a hell of a lot hotter and travelling a lot faster. Maximum speed maybe 10-12% of the speed of light.
Alternatively, use a light sail powered by a really big laser. All you need is to scale up laser and telescope technology a crapload (so, again, considerable engineering development required). Maximum speed? Somewhere between 10 and maybe 30% of the speed of light, depending on just how big you can make your mirror (and consequently how far you can keep accelerating).
The other big issue with interstellar spacecraft is the question of how much debris is out there. If there's a lot, as you go faster you'll need one hell of a shield to protect you.
Finally, there's there's also the possibility of using antimatter-matter reactions to power a ship. Antimatter is kinda powerful stuff to have around, and you could theoretically use it to power a ship to near the speed of light. However, there is no known natural source, and manufacturing it requires milllions of times more energy put in than you get back when you "burn" it. It, therefore, is a really long-term option from when humanity has such astounding energy generation capacity it can afford to use it to power antimatter-powered spaceships.
All in all, there are some possibilities, but most are still a fair bit of technological development away. Let's get to the rest of the solar system first :)
"Only one thing, is impossible for god: to find any sense in any copyright law on the planet." Mark Twain
wouldn't it take just as much force to bring one of these babies to a stop? At the type of speeds they are talking about, wouldn't deceleration be a couple of month process?
I don't think there's any avoiding a mechanical effect, because momentum must be preserved. In fact, in your scheme it's the photon you catch that propels the ship. The one that goes out the "exhaust" carries away the useless wrong-way momentum. Now the problem is: What can absorb those photons without quickly becoming hot enough to vaporize?
You say that nothing is impossible--try slamming a revolving door. :)
According to the article, a vessel using this antimatter engine could reach a speed of 260,000 mph in four months. This converts to an acceleration of roughly 0.0112 meters per second^2.
I think the goal should be for the interstellar starship to accelerate at 9.8 meters per second^2. This would allow to craft to simulate Earth's gravity for its occupants. Once the ship reached the halfway point, they could turn around and accelerated at 9.8 meters per second^2 in the other direction, thus coming to a complete stop upon reaching the destination.
-Jason