Aluminium and magnesium are both available on the Moon.
The problem with aluminum is the exhaust product is the same stuff they make sandpaper out of. A good way to sabotage an internal combustion engine is to throw sand in it. I am skeptical. Pure H2O2 could be useful though.
Rockets can use aluminium as a fuel, aluminium-oxide is pushed out the back by the jet steam. It id internal combustion engines that will have problems.
Quote from: A_M_Swallow on 02/23/2014 07:16 pmRockets can use aluminium as a fuel, aluminium-oxide is pushed out the back by the jet steam. It id internal combustion engines that will have problems.Please cite some sources for your conclusion ICEs run on a H2O2/nano aluminum particle mono-propellant" will have problems". Some types of rockets, including SRBs and ALICE types, depend on the internal combustion of aluminum. ICE's have internal combustion. Adding a piston and using the smallest possible nano particles of aluminum mixed with H2O2 shouldn't be a show stopper.
Quote from: HappyMartian on 02/23/2014 11:04 pmQuote from: A_M_Swallow on 02/23/2014 07:16 pmRockets can use aluminium as a fuel, aluminium-oxide is pushed out the back by the jet steam. It id internal combustion engines that will have problems.Please cite some sources for your conclusion ICEs run on a H2O2/nano aluminum particle mono-propellant" will have problems". Some types of rockets, including SRBs and ALICE types, depend on the internal combustion of aluminum. ICE's have internal combustion. Adding a piston and using the smallest possible nano particles of aluminum mixed with H2O2 shouldn't be a show stopper.That is an extreme form of coking.http://www.exxonmobil.com%2Flubes%2Fexxonmobil%2Femal%2Ffiles%2FTTopic6_OilCoking1.pdfFew ICE are designed to handle solid and liquid products.
That is interesting: a Catherine Wheel generator. Could take advantage of the higher theoretical thermodynamic efficiency of rocket engines (that are technically a type of ICE). No air resistance on the Moon. Depending on the radius, you could generate amazing amounts of torque.... I like it! Good call Hap! Better slap a patent on that one!As for AL/H2O2 engines, I see your point about the polishing effect. And in any case the engine would only need to last a couple hundred hours at most. However, density isn't the prime consideration: specific energy--how many Joules can be packed into a kilogram--is the main determinant for loiter time of an ICESIP prospecting rover. Density does help in that your tankage requirements are less. I'd be curious to know the Al/H2O2 specific energy.
....Thus, for H2/O2, specific energy is 13 MJ/kg. Assuming an ICE-hybrid system with 50% efficiency, that's still 6.5 MJ/kg. Throw in 10% for tankage, and you're still looking at 5.9 MJ/kg. Yes, I know that 50% is probably not going to be the systems thermal efficiency (i.e., the stored energy converted to rotational energy), but if you can make use of the "waste" heat for heating and cooling purposes, that's got to count for the overall efficiency of the system.....
....Very interesting paper, albeit a bit dated: states the specific energy of batteries for a Honda EV are 0.25 MJ/kg, whereas the Tesla Model S has got it up to a whopping 0.475 MJ/kg.
Attached is a very interesting paper on a H2O2 ICE that is proposed as a nice "anaerobic" (and, I might add, a nice "heterotrophic") power supply for robots. There's been some talk the proposed RPM/RESOLVE lunar rover might be landed by a MoonEx lander running H2O2. Presumably they will land with a certain amount of margin; perhaps the residual propellant could be leveraged to power a small 25 cc ICE that would last longer within the PSR than the battery it's currently configured to use?