Notes on fabrication of spacecraft, Part IX

Speculation alert:   Series continued from last post.

The discussion moves into more shaky ground here, as I am thinking up a lot of new stuff here.  Stuff that hasn't been done before ( as far as I know ), and stuff that may never be done for whatever reason.

As I discussed in the last post, an idea occurred to me to use the MAB concept discussed in a series I did on this blog back in 2012.  A problem occurred to me, and that is this:  atmospheric oxygen will harm the heat exchangers for the MAB, which will have to double as a heat exchanger with onboard  hydrogen when you get out of the atmosphere.  So, the trick here is to do what the SABRE engine does.  Pre-cool the incoming airstream all the way down to the condensation point for oxygen.  Separate the oxygen, then run the remaining gases through the heat exchanger.  The remaining gases shouldn't be too troublesome.

While you are doing this, you will have to use some hydrogen for the removal of the oxygen.  Here's an idea to deal with that:  You could reinject the oxygen and the hydrogen into the exhaust as a type of afterburner in order to get more thrust.  There was an idea to do that with nuclear thermal engines (NTR), so this shouldn't be too crazy an idea.

In the SABRE engine, helium is used to transfer heat from atmospheric gases to the hydrogen.  That means that the helium will have to be reconstituted somehow.  The SABRE is somehow able to do this, so I figure this system will employ a similar technique.  Since we are not using hydrogen at this stage, the hydrogen itself also has to be used.  I think the SABRE engine dumps the hydrogen or burns it somehow.  At any rate, the burning of the hydrogen with the separated oxygen is worth some energy that can be tapped somehow.  This energy can run some of the systems on board the way the SABRE does it.

As a result, we will be expending some fuel even though we don't use hydrogen as a primary reaction mass.

That amount of fuel can be considered in the ISP calculations.  How to obtain that is a bit beyond me at this point.  At any rate, if it isn't superior to using the SABRE engines and hydrogen, it won't be worth doing.  But it should be worth doing because the primary engine for driving the system is coming from the Microwave Beam.

That should give an ISP well north of the 3500 range of the SABRE.

I wrote "Infinite ISP" in the series title.  That is not accurate.  Consider this to be a correction.

Now the system will have the MAB as first stage, which will take the vehicle up Mach 5.5 as the SABRE would have, and up to the Karman line as in the original configuration.  The twist would be that it would use Microwave Beam for energy instead of burning hydrogen in a conventional rocket mode of the SABRE engine.  From the Karman line, it will release the NTR and that will go on up into space.

The system should mass at considerably less weight than the 285k lbs figured for the configuration up to this point.  Now, since we may want more capability, we will have more design flexibility so that additional capabilities could be put back in.  Capabilities that should make the entire system safer and more reliable.