Mixed-Mode Rocket engine (tripropellant engines)

[Michel Van]

Mixed-Mode rocket Engines use two propellant with oxidiser
The idea to use dense propellant during Launch then switch to hydrogen for more performance
that why those engines are proposed for SSTO or air launch Shuttles

this document by Aerojet from may 1977
is in depth study of Mixed-Mode Engine under Various propellant with Hydrogene/Lox

Advanced high pressure engine study for mixed-mode vehicle applications

Advanced high pressure engine study for mixed-mode vehicle applications - NASA Technical Reports Server (NTRS)

High pressure liquid rocket engine design, performance, weight, envelope, and operational characteristics were evaluated for a variety of candidate engines for use in mixed-mode, single-stage-to-orbit applications. Propellant property and performance data were obtained for candidate Mode 1 fuels...

ntrs.nasa.gov

 

[OliverSedlacek]

Is it just me that's perplexed by this obsession with SSTO? I can see the sales pitch to venture capitalist who don't really understand the numbers and get seduced by the promise of obvious re-usability. Seeing that re-usable boosters are there for all to see, dragging the bulk of a whole rocket into orbit and then getting it through reentry is a millstone that cripples performance. Two stages let you optimise rocket motor design for two different regimes and you can use different fuels if you want. It looks like a development dead end to me.

 

[publiusr]

Breakthroughs in materials design may make all the difference.... there was a metal that got *stronger* when cold.

 

[Scott Kenny]

Is it just me that's perplexed by this obsession with SSTO? I can see the sales pitch to venture capitalist who don't really understand the numbers and get seduced by the promise of obvious re-usability. Seeing that re-usable boosters are there for all to see, dragging the bulk of a whole rocket into orbit and then getting it through reentry is a millstone that cripples performance. Two stages let you optimise rocket motor design for two different regimes and you can use different fuels if you want. It looks like a development dead end to me.

That was definitely the case before SpaceX and the Falcons.

It may prove more viable now.

Kerosene has some significant advantages over hydrogen or methane for first stage fuel, between small volume and large mass flows for high thrust.

 

[Archibald]

I have a bunch of Salkeld /Beichel/ Bulman papers (1978 / 2008 ) on my HD. Will try to post some of them.

 

[Byeman]

Breakthroughs in materials design may make all the difference.... there was a metal that got *stronger* when cold.

not enough to matter

 

[publiusr]

Article today entitled "Calculating the energy requirements for using moondust to create rocket fuel" at phys.org along with an article concerning "selective combustion."

The use of a catalyst allowed researchers to burn one molecule but not another via chemical looping, as per Matthew Jacob at the University of Minnesota.

This may have some utility in space.