Space Launch Initiative

The Space Launch Initiative (SLI) was a NASA and U.S. Department of Defense joint research and technology project to determine the requirements to meet all the nation’s hypersonics, space launch and space technology needs. The program began with the award of reusable launch vehicle study contracts in 2000.

The primary goal of this research was to increase safety and reliability and to reduce overall costs associated with building, flying and maintaining the nation’s next generation of space launch vehicles. NASA anticipated that these advances would revitalize the nation’s space transportation capabilities, and dramatically improve NASA’s ability to conduct science and exploration missions in space. |This program was ended with the cancellation of the X-33 and X-34 and the conclusion of the X-43 programs. NASA changed its focus to Constellation Program.

The Space Launch Initiative Propulsion Office, managed by NASA’s Marshall Space Flight Center in Huntsville, Ala., sought to advance technologies and explore new avenues of space propulsion to develop safer, more reliable and affordable propulsion solutions. Four main engine candidates for a second generation reusable launch vehicle emerged, including two hydrogen-fueled (COBRA, RS-83, TR-106) and two kerosene-fueled (RS-84, TR-107) staged combustion engines.

California Poly Pomona's Professor Steven Dobbs was the Lead Systems Engineer on the project, making significant use of the program as an example for failed systems engineering.

COBRA rocket engine
Propulsion system proposed by Pratt & Whitney-Aerojet Propulsion Associates to cover a wide range of thrust. This LH2/LOX reusable rocket engine was designed in 2003 to produce 4,500 kN thrust. Proposed as a long-life, moderate-to high-thrust, reusable booster engine that incorporated a safe, low-cost, low-risk, LH2/LOX single burner, using a fuel-rich, staged combustion cycle.

RS-83 rocket engine
The RS-83 was a rocket engine design for a reusable LH2/LOX rocket larger and more powerful than any other. The RS-83 was developed by Rocketdyne Propulsion and Power, located in Canoga Park, California to power the launch vehicle as part of the Space Launch Initiative program. This engine was designed to produce a thrust of 664000 lbf at sea level and 750000 lbf in a vacuum with an Isp of 395 and 446 seconds (3.87 and 4.37 kN·s/kg), respectively. The RS-83 is loosely based on the RS-68 that powers the Delta IV expendable launch vehicle. The RS-83 design is more efficient, lighter, slightly stronger, and yet reusable. The RS-83 was designed to last 100 missions, and was intended for use on the first stage of a two-stage-to-orbit reusable launch vehicle.

RS-84 rocket engine
With Rocketplane Kistler unable to meet funding obligations for its K-1 launch vehicle As part of the Space Launch Initiative, Rocketdyne developed a plan for the RS-84 rocket engine. It would have been the first reusable, staged combustion cycle, liquid rocket engine produced by the US to use a hydrocarbon fuel. In contrast, the Soviet Union developed the RD-170 reusable staged combustion hydrocarbon engine for the Energia rocket in the 1980s.

The prototype engine would have 4732 kN at sea level; 5026 kN  in vacuum; an 8-shift turn time; a specific impulse of 305 at sea level and 324 in vacuum. NASA cancelled further development in 2005.

TR-106 / TR-107 rocket engines
The TR-106 or Low Cost Pintle Engine (LCPE) was a developmental LH2/LOX rocket engine designed by TRW under the Space Launch Initiative and tested at NASA John C. Stennis Space Center throughout 2000. The Stennis test stand results demonstrated that the engine was stable over a wide variety of thrust levels and propellant ratios.

Development of the engine was temporarily discontinued with the cancellation of the Space Launch Initiative. Since 2000, TRW has been acquired by Northrop Grumman and development of the TR-107 RP-1/LOX rocket engine began in 2001 for potential use on next-generation launch and space transportation vehicles is continuing under contract to NASA.

Technology lessons from the Low Cost Pintle Engine project assisted subcontractor development of engines by SpaceX.

Air Force Reusable Booster Program
The Air Force Reusable Booster System program may renew interest in further development of these engines.