Brief. "All models are wrong. Some models are useful." ~~~=3D George Box. Voltage is pumping pressure =3D head of water equivalent. Current is current flow. If the pressure is supported by an infinitely strong pump then using larger and larger pipes gives more flow limited only by the pressure drop in the pipes. Analogy breaks down if you start looking at wall resistance, boundary layers, turbulence etc - just consider a pipe has "resistance to flow". Energy is water mass you can pump to a given head or flow from a given head. Power is rate of pumping a given mass. V =3D pressure =3D head. I =3D current =3D current =3D mass per time. R =3D resistance =3D resistance. Power =3D V x I =3D Head x (mass per time) Energy =3D V x I x t =3D Head x mass per time x time =3D head x mass (=3D m= gh) There is a very solid finite upper limit on chemical efficiency based on the bond energies. Actual can approach theoretical for thermal release. Useable in engines is lower. Most hydrocarbons have around 10 kWh/kg bond energy LPG about 14 kWh/kg. Hydrogen gives about 40 kWh/kg. High explosives are in the same approximate range as hydrocarbons - they are just "better" at breaking all their bonds at once than is eg petrol. Fortunately. A cup of petrol and a stick of dynamite are of about same energy content. Petrol (as usually used) needs to be vaporised and mixed with air to liberate its energy. Do this "in the open" and you have a FAE - fuel air explosive. Flour does it too! (grain milling plants sometimes manage to explosively decompose due solely to grain dust and air igniting). Hydrogen is low density (as gas or liquid and not much better as a solid) so getting a Hydrogen store to have energy densities that are useful requires pressures beyond reasonableness, or liquid Hydrogen (which is still rather un-dense). (Hydrogen at many MPa pressure diffuses through steel. The steel "embrittles". Hydrogen at MPa pressure in embrittled steel containers is not usually good for your health. Armstrong et al went to the Moon on liquid Hydrogen fuel. LH is not a friendly substance for a pocket battery. In an unfinished SciFi story I wrote long ago I posited personal power packs that used matter / antimatter annihilation as the energy source. That gives you densities as useful as you want if you can make the antimatter containment pocket weight and deal with the reaction products. The likely ranges of "if" seems quite limited. Energy available approaches E =3D m.c^2 (which formula you may have met :-)= ). For mere milligrams of antimatter you get useful power for a lifetime. On grams you can fly as required. 1 gram gives you about 20 kilotonne of fuel or explosives equivalent. I can dig the notes out sometime maybe. Below are a few notes from a 10 year old file. There will be MUCH more on web about this. Russell McMahon __________________________________________________ Below: eg 1m3 =3D 10^-3 ANTIMATTER "AMAT" =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D ** ENERGY CONTENT OF AMAT: 1 gram of amat is energy equivalent to 20,000 tonnes of chemical fuel ie ratio of energies is (2e4 x 1e3) Kg / (1m3) Kg =3D 2e10 ie Antimatter is about 2E10 (20 billion) times more "energetic" than chemical fuel. 1.8E14 joules/gram (?=3D 6e20 antiprotons) ie 6e20/2e14 ap's/joule =3D 3e6 antiprotons/joule or minimum energy release per particle is about 0.3 microjoule ** COST OF AMAT: $10 billion / gram is amat breakeven cost with chemical fuels Proton/Antiproton --> pions and gamma rays. (?3 types of pions made) ?2 pions are charged and therefore trappable and 1 is uncharged 20 Ktonne Hiroshima bomb >< 1gram amat (20 megatonne / kilogram?) 10m6 gram amat suitable for bullet source 10m9 gram per bullet for neutral particle beam ? A universal space plane would have a mass ratio of 3 (?e) to use the minimum amount of amat for a given mission. As the mission gets more energetic the % of "fuel" which is amat grows. --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .