#### Science Forum

sonhouse
Science 01 Feb '11 21:04
1. sonhouse
Fast and Curious
01 Feb '11 21:044 edits
I was doing back of the envelope calculations about the energy content in anti-matter and worked out it to have 26 Kwhr/Microgram.

Anyone want to verify that? That would be the typical power to run an electric vehicle for about an hour, that would represent about 100 km/microgram if we could use antimatter in a car!

100,000 km/Milligram, 100,000,000 km/gram! God knows what it would be in miles per gallonðŸ™‚

well, a gallon weighs in at about 7 pounds, call it about 3000 grams/gallon, so that would be about 300 billion miles per gallon!

Can you even SEE a microgram of antimatter if it was lumped together safely like in a magnetic bottle?
2. 01 Feb '11 21:47
Originally posted by sonhouse
I was doing back of the envelope calculations about the energy content in anti-matter and worked out it to have 26 Kwhr/Microgram.

Anyone want to verify that? That would be the typical power to run an electric vehicle for about an hour, that would represent about 100 km/microgram if we could use antimatter in a car!

100,000 km/Milligram, 100,000,000 k ...[text shortened]... u even SEE a microgram of antimatter if it was lumped together safely like in a magnetic bottle?
What would a microgram of antimatter cost with the technology available today? More or less than gold?
3. sonhouse
Fast and Curious
01 Feb '11 22:02
Originally posted by FabianFnas
What would a microgram of antimatter cost with the technology available today? More or less than gold?
well considering we make antimatter a few atoms at a time in this century anyway, it is something like a trillion dollars a gramðŸ™‚
Of course if you get 300 billion miles per gallon, that makes it only about 3 bucks a gallon. For one car anywayðŸ™‚

There are plans and theories that says there are ways to collect antimatter in space with big (1000 meter wide spheres basically of chicken wire pumped up to about 100 million volts and a magnetic antimatter trap in the center, supposed to be able to collect relatively large amounts of the stuff. My guess is if that turns out to be a viable project, it would be a 22nd century project.
4. 02 Feb '11 07:59
Originally posted by sonhouse
I was doing back of the envelope calculations about the energy content in anti-matter and worked out it to have 26 Kwhr/Microgram.
Sounds like a very compact energy storage solution (battery).
Presumably, making the stuff uses as much energy as we get out, plus some that is lost. Do you know approximately how much energy is lost ie how efficient the process is (with current technology).

It does sound like the sort of thing we need to power spaceships, as the biggest problem they have is the mass of the fuel.

Another possibility is power storage (for power stations).

It also sounds like the sort of thing that could make a pretty big bomb - possibly without the downsides of nuclear bombs.
5. 02 Feb '11 11:35
There is no one-to-one relationship between mass and energy.
6. 02 Feb '11 12:54
Originally posted by KazetNagorra
There is no one-to-one relationship between mass and energy.
Is sonhouse assuming that antimatter can be made to react with ordinary matter in such a way that both particles are converted into pure energy? If so, is he wrong?
My understanding was that other particles are created.
7. 02 Feb '11 13:165 edits
Originally posted by sonhouse
I was doing back of the envelope calculations about the energy content in anti-matter and worked out it to have 26 Kwhr/Microgram.

Anyone want to verify that? That would be the typical power to run an electric vehicle for about an hour, that would represent about 100 km/microgram if we could use antimatter in a car!

100,000 km/Milligram, 100,000,000 k ...[text shortened]... u even SEE a microgram of antimatter if it was lumped together safely like in a magnetic bottle?
I worked out the amount of joules of energy from a microgram of anti-matter, but how did you work out the kilowatt-hours?

E=mc^2

m = 1 microgram = 1x10^-3 gram = 1x10^-6 kg

E = 1x10^-6 x 299792458^2 = 89,875,517,873.681764 J

EDIT: Of course, assuming that ALL the matter gets converted to energy. I am presuming the figure will be twice this much considering you will be also converting matter.

EDIT 2: Ok, found out that 1 kWh = 3.6 megajoules, so calculated it to be 49.9 kWh/microgram.
8. 02 Feb '11 14:47
Is sonhouse assuming that antimatter can be made to react with ordinary matter in such a way that both particles are converted into pure energy? If so, is he wrong?
My understanding was that other particles are created.
It depends on the type of collision you're regarding. A positron and electron for example (usually) annihilate into pure energy (in the form of photons).
9. 02 Feb '11 15:381 edit
Originally posted by KazetNagorra
It depends on the type of collision you're regarding. A positron and electron for example (usually) annihilate into pure energy (in the form of photons).
And would you know how the positrons are created? Is pure energy used to create a positron and electron pair, or is there possibly some saving somewhere - eg ordinary matter being used for the input side of the energy equation?

It seems both are possible.
10. sonhouse
Fast and Curious
02 Feb '11 16:40
And would you know how the positrons are created? Is pure energy used to create a positron and electron pair, or is there possibly some saving somewhere - eg ordinary matter being used for the input side of the energy equation?

It seems both are possible.
Also, anti protons and protons annihilate to photon energy as well. Any particle and its counterpart goes to photons after collision. So my back of the envelope number was at least in the right order of magnitude, off by a factor of 2. I was using a number given somewhere that said one kilogram would power a 100 watt bulb for 30 million years, something like that. So it would follow that it would power a 30 million watt bulb for 100 years and 3 gigawatts for 1 year which is about 31 million seconds so 3 gigawatts times 31 million gives the watt seconds or joules from one KG of matter, and it seems I was off by two because it has to recombine with ordinary matter, actually making it 2 kg of reaction mass.

From what I read, the engineering of the anti-matter rocket is further along than the fusion rocket. That is to say, IF you had a supply of anti-matter held in a magnetic bottle safely, you could actually make an anti-matter rocket using today's technology.

The anti-matter would be guided to a reaction chamber nanograms at a time to simply heat up a propellant and expel that out the rear end, instant rocket but a heck of a lot more powerful than any chemical rocket.

I imagine the heat would be so severe as to make the propellant go to relativistic speeds and that alone would increase the mass of the thrust.
11. 02 Feb '11 17:17
Originally posted by sonhouse
I imagine the heat would be so severe as to make the propellant go to relativistic speeds and that alone would increase the mass of the thrust.
or vapourise the rocket. ðŸ˜‰
12. sonhouse
Fast and Curious
02 Feb '11 18:27
Originally posted by lausey
or vapourise the rocket. ðŸ˜‰
No, the exhaust is shaped and guided by a magnetic field, the plasma never touches a wall.
That has the bonus of being able to modulate the specific thrust, high thrust for max accel or opening up the magnetic throat for slower exhaust but longer drive times.
13. 03 Feb '11 10:24
And would you know how the positrons are created? Is pure energy used to create a positron and electron pair, or is there possibly some saving somewhere - eg ordinary matter being used for the input side of the energy equation?

It seems both are possible.
Indeed, the inverse process, where two photons annihilate to form an electron-positron-pair is also possible (and there are many other ways to generate positrons, usually from radioactive decay such as beta+ decay). But these have to be very high energy photons, obviously.