LOXLEO, Part V

As usual, this will be a speculative post.

The last post explored the possibility of using the nitrogen to make nitric acid.  But what if this is not practical?

If such be the case, what could be done with the nitrogen besides just dumping it?

It so happens that there are themalization issues with the VASIMR design, which is to be used as propulsion in this design.  Lets say that the nitrogen could be used to cool down the engine and then expelled under pressure for additional thrust.  This would be the simplest solution, and it may not be impractical to boot.

Assuming that is successful, what next?

Perhaps this is getting ahead of the game too much.  Let's go back to how we get the nitrogen separated from the oxygen in the first place.  

The truth is, the use of the atmospheric gases at sea level, which include nearly 20% oxygen, would be sufficient to run the hydrogen fuel cells.  This will make the electricity for the VASIMR while giving water as a product.

The resultant gases remaining should be significantly higher in nitrogen.  It is already nearly 80% nitrogen to begin with.  After using the oxygen for the fuel cells, it should be even higher than that in concentration.

Couldn't you just burn some hydrogen directly in this atmosphere and thereby remove the rest of the oxygen?  If so, the remainder should be close to zero percent oxygen, which then could be routed toward VASIMR and used to cool it down, and then expelled as exhaust.

As stated before, the basic idea here is to avoid using so much energy in order to collect oxygen.  The edge of space will still have some oxygen that can be collected as well as the other atmospheric gases.  The thought occurs though, is this: was the original design for collecting the oxygen energy intensive by necessity?  Or was the assumption that nuclear power would be available and that would be able to supply the energy required for the collection of atmospheric oxygen?

If nuclear power isn't available, there has to be a different approach.  Is there an approach to collect the gases which doesn't require a great deal of energy expenditure?  To answer that question could take you all of the way back to the drawing board.

Here's a brief thought on that.  In order to initially collect the gases, could it not be funneled into a smaller space, which will have the effect of creating higher pressures?  After all, this should be our goal- to build up from a near vacuum to a usable atmospheric pressure.  This proposition would entail a funnel type device that narrows down to the size that is, let say 1 millionth the size of the opening.  The ratio as such could be enough to pressurize the gas so that we can use it for our purposes.

The downside of this approach could be amount of drag induced upon the spacecraft.  If the drag is not too much, and could be handled by the VASIMR, we are in business.  Another possibility is heat.  At orbital speeds, the velocity of the gas will be considerable.  As it compresses, it will have to slow down.  As it does that, it is likely to get hot.  Cooling systems will have to be devised to handle that outcome.

That may not be an insurmountable problem.  Just route the liquid hydrogen around the funnel and it will cool it down, as is done in modern rocket engines.  This will have to be done anyway, as hydrogen needs to be brought out of cryogenic storage for use in fuel cells.