I need someone familiar with supercolliders, those things they use to smash matter and antimatter together, to help me explore this. On its "antimatter" page, Wikipedia cites a source (http://www.nasa.gov/exploration/home/antimatter_spaceship.html) claiming that antimatter, in the form of positrons, can be produced at $250million per 10 milligrams. 10 mg is a lot of antimatter! If that were reacted with another 10 mg of normal matter, it would create 1,800 gigajoules of energy! Assuming we could harness that energy into electric power, and assuming we could throttle the collision rate, then we could have for example 1 megawatt of power for almost 21 days. Of course it's not going to be 100% efficient, but even a system efficiency of 25% would still be pretty darn good imo. Here's my concept. Electrons and positrons are held in separate chambers of a device, probably by a magnetic field. Somehow they are made to move out of those chambers at a very small rate, although probably at high speeds, and collide with each other in a collision chamber. This produces gamma rays. The collision chamber walls are lined with solar panels, tuned to absorb gamma rays, and via the photoelectric effect convert it to DC electric power. Some of this power would go back into maintaining the magnetic containment fields so that the device is self-sustaining. To me it seems great: no moving parts and better energy density than nuclear power. Too good to be true? Can anyone vouch for this or explain why it's impractical? I can think of several engineering problems and hopefully we can address most of them. (1) Is it possible to create solar panels that are NOT tuned to absorb visible or infrared light, as normally is the case, but rather gamma rays? Also they would have to have a decent lifetime. (2) How to contain the separate blobs of electrons and positrons in a safe way, yet still have a way to accelerate them out of the chamber so they collide with one another at a small rate? We can accelerate one or the other, or maybe both. (3) Do we even need to contain electrons in their own chamber? Or can we just liberate electrons on demand from normal conducting material? (4) Would the solar panels have to be cooled? (5) Exactly how much electric power is needed to magnetically contain a blob of X grams of positrons? (in a vacuum?) And exactly how much electric power is needed to accelerate them to the collision chamber? (6) Can we ensure that a high percentage of the matter and antimatter, say over 90%, indeed collide within a targeted volume and don't miss? (7) Is there a better choice of matter-antimatter? Ignoring procurement problems, would it be better to use protons and antiprotons? Possibly hydrogen and antihydrogen or helium and antihelium? An isotope of them? (8) Instead of solar panels, is there a better way to convert gamma rays into electric power? Note, im NOT thinking of this as a cheap or renewable energy source of the future. $250M per 1,800 GJ comes out to $500 per killowatt-hour! Im thinking of this as a great power source for spacecraft, maybe submarines as well, or any remote vehicle.
The biggest issue with an anti-matter power supply is the creation of said anti-matter; if I recall, at present it takes millions of shots to get a few molecules of anti-matter.
^ Agreed. Total world production of A-M so far is about 10 nanogrammes. The cost of energy to produce that will be more than any money recouped from selling power using that as a source.
bottling the antimatter isn't easy. might as well use the more massive anti-protons rather than anti-electrons (positrons). Fermilab had a lot of good experience at this, as they ran anti-protons in their ring. they bottled them before injection. http://www.fnal.gov/pub/science/inquiring/questions/antimatterprod.html but it does not look like a feasible method at present. a leaky bottle would be a disaster for a space-ship.
If you mean propulsion, then the next question is how you apply this to develop thrust, which requires the ejection of matter.
No i don't mean propulsion per se. I mean electric power for all systems in general, such as radios, computers, air pumps, etc. It could also include propulsion if you're talking about things like ion drives, hall-effect thrusters, VASIMR, etc. There are plenty of electric rocket concepts out there and i don't want to get into them. What i want to get into is concepts for antimatter-driven electric power. Maybe I should focus on one question for now: Can solar panels be made to receive gamma rays instead of visible light? More specifically, would the photovoltaic effect be the same for such high frequencies? And do we have the right conducter or semi-conductor material for it? Well of course, i never said otherwise, and more to the point i brought up this concept design to serve not as profitable, but as better than other power sources for spacecraft. My posts are usually long, but what more can i do to be clear except a final "note" explaining this: I suppose it's a common misconception that something needs to be profitable. Well, spacecraft are not operated for profit. Nor are nuclear submarines. Yet they've been operating for half a century now. A new power source just has to have at least one good advantage where it becomes desirable, for at least a niche role, or if it has many advantages, it becomes desirable for many roles.
Yeah. Given that I'd already pointed out that the current total of A-M is ~10 nanogrammes and that it cost more to produce than could be retrieved from it don't you think that kinda points to finding a cheaper and more readily available source of power for spacecraft? While they're not operated for financial profit they are certainly subject to cost-benefit analysis. If they cost more than any likely return (of whatever kind) then they aren't built/ put into service. Which leads us back to... finding a much cheaper alternative.
OK, here is what CERN says: Frequently asked Questions about Antimatter 1) Is antimatter a new source of energy? - it is true that the annihilation of 1 kg of antimatter with matter would generate an enormous amount of energy (9 · 1016 J, corresponding to a 1 GW power plant running for 3 years); but: - there is no natural ‘mine’ (on Earth or even in the Universe) where antimatter can be dug out - antiparticles have to be made by using accelerators for concentrating (kinetic) energy in particle beams and then colliding them with a block of matter (E = mc2) - making antiprotons costs about 10 billion times more energy than is finally stored in their mass - to make a kilogram of antimatter would therefore take all the energy produced on Earth for 10 million years. 2) Can antimatter be used for energy storage? - Yes. For storing small amounts of energy in an extremely compact way, antimatter is very useful. The energy density stored in antimatter is about 1 billion times higher than in batteries. - But: the amount of antimatter that is produced each year in big accelerator labs such as CERN or Fermilab corresponds to an energy that would allow a 100 W light bulb shine for 15 minutes. 6) Antimatter as rocket fuel? - There are indeed researchers in the U.S. working with NASA on futuristic concepts for antimatter induced fission engines. Antimatter would not be the main source of energy, but would be used instead to split heavy nuclei (antiprotons would be the ‘matchstick’). However, even for this applications about 1 milli-gram of antiprotons would be needed, about 100,000 times more than the present annual production on Earth. In addition, many serious technical problems (capture, storage, transport) would have to be overcome.
- there is no natural ‘mine’ (on Earth or even in the Universe) where antimatter can be dug out ... Okay how do you make quotes in this new format? But anyway I dispute this antimatter can indeed be mined google: extraction of antiparticles concentrated in planetary magnetic fields Their should be around 10 micrograms of antiprotons in Earths van allen belt alone these doesn't amount to much but it's a start
Equally silly: use current technology to split O off H2O to get H2, and then react it in a fuel cell to make electric power. See my point?
At the present time there are at least three major problems that I can think of, with anti-matter for spacecraft propulsion. First there is the great cost of producing anti-matter. Presently it would seem that positrons are the best bet because of production and storage technologies. Aside from production costs, storage for positrons has not been perfected. It would require a long enough time to fuel up a spacecraft and remain long enough for its usage. Additionally there is the gamma ray exhaust problem which could not be a direct exhaust system since it would be too deadly. Gamma rays would seemingly need to be a secondary fuel supply in a reaction chamber that would result in an acceptable exhaust of some kind. Right now it seems like this is still many years into the future, because of development costs, and if no better technology emerges.
