Spreadsheet calculations for microwave airbreather replacement for first stage

Third post in this series:

Part 1 :  Try lifting on a 747
Part 2:    Use the Stratolaunch concept to lift to 30k feet

Update:

Almost forgot this post.  It is about the nuclear airplane concept from the Cold War, which is being adapted here by eliminating the reactor and beaming the energy via microwave to the aircraft.

This is the "show your work" part of this discussion.  That is, in terms of the rocket equation.

What is being attempted here is to lift an aeroshell based upon the X-33 shape with a separate conventional rocket attached.  It will use a microwave beam as energy to lift to the altitude and velocity that a first stage rocket accomplishes.  Also like the first stage conventional rocket, it will release the second stage to go on to orbit.

This first stage replacement will use Kevin Parkins' doctoral thesis --- it will include a microwave beam that will heat an onboard heat exchanger that will propel the reaction mass for thrust.  The reaction mass will be the atmosphere itself.  ( That part was NOT a part of his thesis--- it is my idea) This will preclude the need for propellant and thus lighten the mass needed to achieve orbit.

The Stratolauncher's purpose is to provide initial velocity and input into the airbreather.  Also to allow for a horizontal launch.

In the spreadsheet, I tried several combinations of isp's and masses in order to calculate the margins for these variables.  I found that the Falcon 9 engines would suffice for orbit, but not necessarily for reusability.  A hydrogen / lox engine, such as a J2X engine, which is postulated here, will be required.

The base stack includes the mass of a s4b rocket plus the J2X.  The capsule will be a Gemini type capsule used in the Apollo program.

As can be seen in the second column titled "ISP", lowering isp from 448 to 437.5 "blows up" the propellant numbers to an unacceptable amount.  The need is to maximize isp so as to make reusability feasible.  The J2X's isp numbers assume a vacuum, which may not be the case.  However, there's plenty of margin for error.

The 26k kg base rocket stack includes capsule, base s4b rocket, plus 40% additional mass for reusability.  The 40% estimate came from my recollection of a discussion on the Space Show.  The name of the guest who gave that estimate eludes me at the moment, and the recollection could be faulty.  But that is what I'm going on.  This estimate provides 7500 kg margin for error on the mass side.  Lowering isp will eat into this margin, but I'm guessing that this number will hold up.

I'm guessing that this part of the analysis can safely conclude that the idea can work.





Update:

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