On Jul 16, 1:45*pm, Robert Clark wrote:

Anyone know if there has been research on converting the shuttle main
engines to hydrocarbon fueled? I was annoyed that NASA had earlier
canceled a program to develop a heavy-thrust hydrocarbon engine after
the Ares I and V were chosen. We would have a reusable and man-rated
heavy-thrust kerosene engine *now* if it weren't for that.
The SSME's have to operate under severe tolerances using cryogenic
hydrogen since the liquid hydrogen is so cold yet LH2/LOX burns at
such high temperature. I would think using kerosene/LOX for instance
would put less severe conditions on the engine operation.
Note that other liquid hydrogen engines have been successfully run on
other fuels under test conditions:

The RL10 (Bruce Dunn; Gary Hudson; Henry Spencer)http://yarchive.net/space/rocket/rl10.html

And some dense propellant engines have been tested to run on cryogenic
hydrogen:

LR-87 LH2http://www.astronautix.com/engines/lr87lh2.htm



Found this after searching on Astronautix.com:

RD-0120.
"Engine Model: RD-0120-CH. Manufacturer Name: RD-0120-CH. Designer:
Kosberg. Propellants: Lox/LCH4. Thrust(vac): 1,576.000 kN (354,298
lbf). Isp: 363 sec. Mass Engine: 2,370 kg (5,220 lb). Chambers: 1.
Chamber Pressu 172.50 bar. Oxidizer to Fuel Ratio: 3.40. Thrust to
Weight Ratio: 67.80. Country: Russia. Status: Design concept 1990's.
Proposed variant of the RD-0120 engine using liquid methane instead of
hydrogen as propellant."
http://www.astronautix.com/engines/rd0120.htm

The RD-0120 was the hydrogen fueled engine used on the Russian Energia
heavy lift booster, which lifted the Russian Buran space shuttle for
instance. I can't tell from this description though if it was actually
tested with liquid methane or if these were only theoretical studies.
After searching on the NASA Technical Report server I found some
theoretical studies that suggest that the SSME could be converted to
hydrocarbon-fueled at relatively low cost (compared to developing a
new engine.)

Booster engines derived from the Space Shuttle Main Engine.
Sobin, A. J.; Poynor, S. P.; Cross, E
"By using a majority of the current SSME engine components for the LOX/
RE-1 booster engine, engine development time and cost can be
significantly reduced compared to the development of a new engine."
Propulsion Conference, 13th, July 11-13, 1977, Orlando, FL
http://ntrs.nasa.gov/search.jsp?N=0&...=197 70059130
[abstract only]

Tripropellant engine study.
Wheeler, D. B.; Kirby, F. M.
NASA-CR-150808; RI/RD78-215
"SUMMARY.
"The results of these studies have shown that the conversion of an
SSME engine to
a high chamber pressure, dual-mode fuel engine will require major
modifications
to the hardware and/or the addition of a significant number of new
engine cowponents.
However, the study has shown numerous possibilities for the use of
SSME
hardware derivatives in a single-mode LOX/hydrocaxbon engines. It was
also
shown that a reduced chamber pressure version of a staged combustion
SSME is
operationally feasible using the existing fuel-rich preburners and
main chamber
injectors. Certain turbomachinery modifications or additions are
required for
a total low chamber pressure ( 2300 psia) engine system. This study
also has
shown that the engine system concepts applicable to the dual-mode
systems are
somewhat narrowed since the operational constraints of two systems
must be
considered."
http://hdl.handle.net/2060/19780024238 [full text, 145 pages]

Another possibility might be to adapt the hydrogen-fueled aerospike
engines intended for the VentureStar to hydrocarbon-fueled. This
theoretical study from 1977 was on the possibility that an aerospike
engine of the linear configuration later adopted for the VentureStar
could be dual-fueled, i.e., running on both hydrocarbon and hydrogen:

Linear aerospike engine study.
Diem, H. G.; Kirby, F. M.
NASA-CR-135231; RI/RD77-170
http://hdl.handle.net/2060/19780003139 [full text, 246 pages]

This would have the advantage that it would already have altitude
compensation. If the dual-fuel modes are workable this would also
increase performance.
This study was primarily on dual-fuel operation but did also study
hydrogen only operation. It might be useful to compare the predicted
hydrogen only operation with the performance actually found with the
aerospike engines created for the X-33 sub-scale demonstrator. If the
measured performance does correspond to the predicted values that
would give confidence that the dual-fuel version would also be close
to the predicted values.


Bob Clark