RGClark - 14/10/2007 5:34 PMIonization energies of the elements. http://en.wikipedia.org/wiki/Ionization_energies_of_the_elements You see for hydrogen it's 1312 kilojoules per mole. Since the atomic weight of hydrogen is 1, this is 1,312,000 joules per gram or 1.3 billion joules per kilo.
vanilla - 14/10/2007 2:26 PMSalts are nice ways to store ions at room temperature and pressure without net electric charge.
GraphGuy - 15/10/2007 11:42 AMQuotevanilla - 14/10/2007 2:26 PMSalts are nice ways to store ions at room temperature and pressure without net electric charge.Yes, but last time I checked you can't get the ions out of a salt without putting alot of energy in. The net charge of the salt is zero which is why salt doesn't zap you when you touch it.
pfdietz - 16/10/2007 9:22 AM... If the ion is also fairly massive, this will have the beneficial effect of increasing the mass/charge ratio of the ions -- and the maximum thrust/area of an ion engine scales as the square of this ratio, for fixed grid spacing and exhaust velocity.
RGClark - 23/10/2007 5:14 AMQuotekhallow - 14/10/2007 3:20 PMSo you can recycle some of the original ionization energy with minor drop in ISP (from part of the ion beam hitting the plates).Thanks for the serious responses.This page shows that the energy content from antimatter-matter combination is tremendous:Energy density in energy storage and in fuel.http://en.wikipedia.org/wiki/Energy_density#Energy_density_in_energy_storage_and_in_fuelIt's on the order of a billion times higher per kilogram than the energy of burning hydrogen in air. So even if the containment for the kilogram of say charged antimatter particles was a ton that would still be a million times better than the energy content of hydrogen. To put that in perspective, the space shuttle external tank holds about 100,000 kg of hydrogen and 600,000 kg of oxygen. The energy content of that 700,000 kg total of hydrogen and oxygen would be matched by about 1/10th of a kilo, 100 grams, of antimatter storage, *including the weight of the containment system*.
khallow - 14/10/2007 3:20 PMSo you can recycle some of the original ionization energy with minor drop in ISP (from part of the ion beam hitting the plates).
If you do a web search on non neutral plasmas you'll find there has been extensive research on storage of positrons as well as electrons. I believe the storage density of the positrons now is close to that of the electrons.
500 watts per square meter, this would require less that 30 square meters for solar cells. Not terribly bad for this. But the greatest amount of energy would be required to drive the protons at the high exhaust speeds. The power required to drive a propellant at mass flow rate m and velocity v is (1/2)mv^2. So to drive the protons at a flow rate of 10 milligrams per second at 1,000,000 m/s would take (1/2) x (10^-5kg/s) x (1,000,000m/s)^2 = 5 megawatts. At 500 watts per square meter of power using solar cells, this would take 10,000 meters or 100m by 100m. Someone will give me the weight for solar cells nowadays but I think that would be prohibitive for a small unmanned spacecraft. One weight I've seen for space solar cells was 4 kg per square meter. So for 10,000 square meters this would be 40,000 kg. The thrust produced is the mass flow times the exhaust velocity so in this case would be (10^-5kg/s) x 1,000,000m/s = 10N, so appropriate only for small to medium sized unmanned craft in this case.Bob Clark
kkattula - 24/10/2007 3:07 PMNasa have a study for a positron propulsion system. Basically using positron annihilation to heat up H2 to NERVA temperatures and Isp (900). But without the heavy and radioactive reactor core. An advanced ablative engine might hit 5000 Isp. Of course you would need a heavy confinement system.They say $US 250 million for 100 grams of positrons. Enough for a Mars mission.http://www.nasa.gov/mission_pages/exploration/mmb/antimatter_spaceship.html
sticksux - 24/10/2007 8:21 AMNo, they say "A rough estimate to produce the 10 milligrams of positrons needed for a human Mars mission is about 250 million dollars using technology that is currently under development"In other sources (http://www.engr.psu.edu/antimatter/Papers/NASA_anti.pdf) I find $25 million per milligram cost for antiprotons, which is is agreement with above.
khallow - 24/10/2007 11:09 AMHmmm, given how much positrons are necessary, I wonder if it might be possible to fire a cloud of positrons at a vehicle and have some sort of electromagnetic catcher system on board direct them into the propellant? Depends on whether it's any more efficient than other means of heating H2 to the necessary temperature, I guess.
sticksux - 25/10/2007 3:21 AMQuotekkattula - 24/10/2007 3:07 PM...They say $US 250 million for 100 grams of positrons. Enough for a Mars mission.No, they say "A rough estimate to produce the 10 milligrams of positrons needed for a human Mars mission is about 250 million dollars using technology that is currently under development"In other sources (http://www.engr.psu.edu/antimatter/Papers/NASA_anti.pdf) I find $25 million per milligram cost for antiprotons, which is is agreement with above.
kkattula - 24/10/2007 3:07 PM...They say $US 250 million for 100 grams of positrons. Enough for a Mars mission.
khallow - 24/10/2007 5:09 PMQuotesticksux - 24/10/2007 8:21 AMIn other sources (http://www.engr.psu.edu/antimatter/Papers/NASA_anti.pdf) I find $25 million per milligram cost for antiprotons, which is is agreement with above.Hmmm, given how much positrons are necessary, I wonder if it might be possible to fire a cloud of positrons at a vehicle and have some sort of electromagnetic catcher system on board direct them into the propellant?
sticksux - 24/10/2007 8:21 AMIn other sources (http://www.engr.psu.edu/antimatter/Papers/NASA_anti.pdf) I find $25 million per milligram cost for antiprotons, which is is agreement with above.
GraphGuy - 24/10/2007 11:09 AMQuotekhallow - 24/10/2007 11:09 AMHmmm, given how much positrons are necessary, I wonder if it might be possible to fire a cloud of positrons at a vehicle and have some sort of electromagnetic catcher system on board direct them into the propellant? Depends on whether it's any more efficient than other means of heating H2 to the necessary temperature, I guess.Translation into English please? It sounds like you are wondering if you could fire a microgram of antimatter at a spaceship and have it divert it to the fuel.
A couple of obvious problems with this:Earth's magentic fields deflect charged particles, positrons have chargeMagic positron gun doesn't exist (none that could fire that much antimatter and not melt)Little room for error, hope the crew cabin doesn't get hit by a few micrograms of anitmatter
sticksux - 25/10/2007 6:45 AMVery unlikely. I'm afraid you will just mini-nuke the LV in the "best" case.Far more workable solution with some resemblance of the above is laser launch. With all megawatt range laser beam tracking / focusing R&D done in ABL program, it becomes actually feasible. Especially that you can start small by doing experimental boost phase laser assist on existing LVs. Maybe. I'm no expert.