Old fuel, new engine: NASA Space Launch Initiative’s next generation reusable launch vehicle may fly on kerosene

The kerosene that lights your heater or stove might be the same type
of fuel powering the nation’s next space vehicle.

Kerosene – almost as common to American life as gasoline – is being
considered as a fuel for two main engine candidates for a second generation
reusable launch vehicle, now in development by the Space Launch Initiative.
The Initiative is NASA’s technology development program to design a complete
space transportation system with increased safety and reliability at a lower
cost.

Managed by the Marshall Space Flight Center in Huntsville, Ala., the
Space Launch Initiative Propulsion Project Office is developing the
kerosene-fueled RS-84 prototype engine with Boeing Rocketdyne of Canoga
Park, Calif., and the TR107 prototype engine with TRW Space and Electronics
of Redondo Beach, Calif. Two hydrogen-fueled main engine candidates are also
in development.

Kerosene rocket engines are not a new idea. Kerosene was used as a
propellant in the F-1 engines on the Saturn V rockets that took Apollo
astronauts to the Moon back in the late 1960s.

What is new is the design of the engine.

Second generation engines need a more integrated design that is more
reliable, easier to operate, offers fewer components and has a lower cost.
The new, kerosene-fueled engine design will feature a staged combustion
cycle that results in greater fuel efficiency than the F-1’s gas generator
cycle by reusing some of the fuel and oxidizer used in the preburner to
power the main combustion chamber. Preburners heat the propellants to ready
them for the engine’s turbopumps before the propellants are injected into
the main combustion chamber – where the fuels combust to create thrust.

Another difference is overall engine size. To achieve a higher
performance level, the propellant is burned at higher pressure which reduces
the size of the main combustion chamber. That, in turn, increases thrust.

Chamber pressure in the new kerosene engine will be approximately
2,600 pounds per square inch absolute (psia) compared to 965 psia chamber
pressure on the F-1 engine. This increased pressure allows a smaller engine
to provide nearly as much thrust as the larger F-1 engine: The new kerosene
engine will generate a powerful 1.1 million pounds of force – only 400,000
pounds of force lower than the F-1 engine. The most significant difference
between the F-1 engine and a second generation kerosene engine is
reusability.

The F-1 engines were expendable – only capable of use for one
flight. Both the RS-84 and TR107 prototype engines could become the
first-ever reusable engines using kerosene and oxygen-rich gases.

The new, reusable engines would dramatically lower maintenance costs
and allow quicker turn-around time between missions. “A reliable,
low-maintenance, reusable engine is key to affordable space launch,” said
Garry Lyles, Space Launch Initiative propulsion project manager at the
Marshall Center. “Long engine life, whether 50 missions or 100 missions,
will be selected to minimize operational cost.”

Kerosene does have its challenges2