Because 80% of its mass is heavy LOX, from the 720mT.
Yes. LOX is nice and dense... it is actually denser than water.
The ET carries six times as much LOX as it does LH2, but the LH2 tank has nearly three times the volume of the LOX tank.
In short, LH2 is an extremely poor propellant density wise.
Then i would use alltimes air as working fluid.
No. Nuclear jet propulsion is too hard... it requires higher temperatures and worse material conditions, because it is harder to heat a gaseous working fluid. This now makes my nuclear engine far more difficult to build and operate, and is also why building a nuclear airplane is so impractical.
If I go airbreathing, I will use air as a working fluid... but I will just use it as a working fluid in a manner similar to any other jet engine, rather than using nuclear fuel.
Pure nitrogene should although work in a NTR
I don't think the exhaust velocity would be all that good though...
but with the extra O2 in the air it could be a kind of LANTR, for more thrust but im not sure.
I doubt it, considering that O2-N2 isn't exactly the best chemical propellant out there...
And it would be very safe, air is not explosive, for a case of crash landing or when a micrometeorite hits the internal tank and gasses are streaming out.
Frankly, it doesn't really matter when it's cryogenic, liquid air. When you crash it all spills and vaporises and whatnot, and it isn't fun.
MMOD should not be a problem for propellant leakage... small particles will likely be stopped by the double hull that is present on many areas of the vehicle which functions somewhat like a whipple shield. Regardless, on-orbit the propellant will be depleted anyway.
In space the crew could use the "air fuel" for breathing!
Why? That is a real waste, if over a 20 day mission a 6 person crew only uses about 8 kilograms of air, considering all the recycling and whatnot that goes on.
To use a single ton of air they would already be waiting in space for nearly 7 years.
Further you can use it for the RCS, most RCS are runnung by nitrogene.
No. Most RCS systems run on hypergolic propellants, namely oxidizer blends based on
nitrogen tetroxide, and fuel blends based on monomethylhydrazine and unsymmetrical dimethylhydrazine. They are pressure fed, but AFAIK the pressurant is helium, at least predominantly.
These compounds are highly toxic however, and I'm thinking of rather using pressurised gaseous oxygen and kerosene... apparently Buran used this combination, so it must be viable. It'd also be far, far more mundane than those horrible toxic propellants.
its mutch stronger than CO2 for the glass house effect.
It's known as the
greenhouse effect. :thumbup:
Because there is no chemical reaction at a NTR
Not inside the engine as a facet of it's operation, no. But it would be silly to assume that a huge exhaust plume of flammable gas, at hundreds, thousands of degrees, even, would not ignite in the atmosphere. It would be pretty brilliant visually, and I actually worry about any negative effects it could potentially have.
At high altitudes, on the other hand, there's not enough oxygen to burn the methane (see Falcon 1 launch vids, at high altitude you'll see the engine flame fade away). But there is more: at those temperatures, methane starts to disassociate anyway, seperating into it's component parts- something that actually increases the exhaust velocity. So release of methane into the environment might not be that problematic after all.
When you not want nitrogene/air, then use better a similar fuel to methane, but a non-glass-house-effective fuel.
A liquid air fuel is silly. Not only does the high particle mass bring down exhaust velocity, but it has to be kept colder than methane, and has chemical problems with the NTR (I worry about oxygen corrosion). That and obtaining it might be problematic.
Liquid methane already exists, and is an abundant energy source. It's known as Liquified Natural Gas. It's readily available, and if it needs to be, say, further refined, it won't take as much energy or money as liquifying air. And on top of that, I can burn it as well... it opens up use for methane fuel for my airbreathing engines.
Nevertheless, I am still looking for a new propellant... the requirements are that it be dense (the denser the better), yield a good exhaust velocity (the higher the better), easy to handle, cheap, and environmentally friendly (i.e. not toxic or carcinogenic).
