Performance evaluation and design review will pave the way for full-up "powerhead" tests during next year

Pratt & Whitney and Aerojet will hold a crucial preliminary design review on 31 March of the Cobra second-generation reusable launch vehicle (RLV) rocket engine as part of a build-up to a complete test of the engine's heart, called the powerhead, next year.

The test run, which will evaluate the performance of the Cobra's main case, turbopumps and pre-burner, will mark the end of the first, two-year phase of the project which is funded under NASA's Space Launch Initiative. This is aimed at substantially reducing launch costs relative to the Space Shuttle, and dramatically improving safety. The first technology demonstration phase will be followed by a second in which a full-scale prototype engine will be demonstrated and a third phase covering full-scale development.

Although the focus is on Cobra - a moderate- to high-thrust engine aimed at the 500,000lb (2,225kN) to 800,000lb power bracket - P&W says a lower thrust proposal, the RLX, is "also getting a lot of attention" as NASA approaches the downselect decision for the second two.

Although the RLX is initially aimed at the lower 100,000lb- to 300,000lb-thrust bracket, Aerojet and P&W are studying technology demonstrations to prove that the split-expander liquid hydrogen and liquid oxygen cycle can be scaled up to higher thrust. "A lot of feelers are being put out to find out if RLX will do that," the company adds.

A third booster option, dubbed AJAX, is also being studied under Aerojet's lead. This is a US-based single pre-burner design using a staged combustion hydrocarbon fuel concept.

"Once we get through the powerhead test, then we plan to go to core tests and a prototype test," says P&W, adding that the evaluation of Cobra in parallel with technology for RLX and AJAX is part of a "stepping-stone process over the next five years". As the technology evolves, NASA could "change direction" and adopt any of the booster technology options, it adds. The current timescale does not call for first flight of the second-generation RLV until 2010 to 2012.

Before attempting the powerhead test, P&W plans a partial pressure test of the Cobra pre-burner, to around 50%, at its West Palm Beach site in Florida, before a full pressure test is later attempted at NASA's John Stennis Space Center rocket propulsion test-site in Mississippi.

Source: Flight International