Methane powered RS-25 (SSME) proposal for SLS and EELV 2.0
Here is an early study of a methane powered SSME for the shuttle program that we advocate should be looked at again for the SLS and EELV programs
19780006151 (1)
This paper discusses dual mode SSME operations so this encourages my idea that you could cross feed LCH4 into a LH2 core stage on SLS or an EELV and the possibility of researching Gelled LHC4 systems
http://www.grc.nasa.gov/WWW/Fuels-And-Space-Propellants/GELLED.htm (2)
The above paper on methane gels in LH2 suggest that the 1978 paper could be modified to incorporate duel fuels with fewer modifications to the hardware and less R&D costs
the idea in more detail in an earlier post below
https://yellowdragonblog.com/2014/11/04/methane-powered-rs-25e-1-5/
my thoughts are you use a dual fuel engine with methane gels in LH2 as suggested in the paper above (Gelled Methane) and that we can use a “dial a fuel” by varying the Mix and or flow rates of gelled LH2 into a LH2 core stage
Yellow Dragon, a mission to repurpose existing ideas into new ideas 
Thanks for the great find. Adapting an already existing engine should provide a faster, cheaper route to a hydrocarbon fueled engine that could be used to replace the Russian engines on the Atlas V and Antares as well as for high performance liquid-fueled boosters for the SLS.
Note also a high-performance engine such as the SSME able to run on hydrocarbon or hydrogen would be ideal for an SSTO.
Bob Clark
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