GRAHAM WARWICK / WASHINGTON DC
Agency studies range of launcher concepts, focusing on technology demonstrations
NASA is reporting progress with its Next Generation Launch Technology (NGLT) programme, but admits funding is inadequate to achieve the goal of maturing technology for a Space Shuttle successor. The earliest decision to begin development of a reusable launch vehicle (RLV) to replace the Shuttle could come in 2009.
"The current programme is inadequately funded for what we want to do," says Uwe Hueter, NASA team leader for NGLT within the National Aerospace Initiative (NAI). "We know the funding we need, and we recognise the shortfall is pretty large." NAI is a joint US Department of Defense and NASA programme to develop technology for hypersonic vehicles and space access.
NGLT was created in late 2001 when NASA restructured its Space Launch Initiative to combine second- and third-generation RLV work under a long-term technology programme to parallel near-term development of the Orbital Space Plane (OSP). As structured, NGLT supports three decision dates on starting full-scale development of a Shuttle replacement, says Hueter: 2009, 2015 and 2020.
If NASA decides to go ahead in 2009, the RLV would be rocket-based, says Hueter. A decision around 2015 would allow a choice between a vertical take-off rocket with engine-out capability and a horizontal take-off vehicle with in-flight oxidiser collection. After 2020, a hypersonic air-breathing RLV would be possible, he says. In each case, development would take at least five years from a decision.
NASA is studying a range of launcher concepts, from evolved expendable boosters to partially and fully reusable vehicles. Already the programme has tested rocket engine components and cryogenic fuel tanks. But the goal is to reach a technology readiness level of 6, requiring flight demonstrations.
Boeing's Rocketdyne division is hot-fire testing a subscale preburner for its 1 million lb-thrust (4,450kN) RS-84, a prototype oxidiser-rich, staged-combustion, kerosene-fuelled reusable rocket engine that could enter full-scale testing in 2007. Rocketdyne has also tested a liquid-hydrogen fuel turbopump for a reusable rocket engine with a 200-flight life and 100 flights between refurbishment.
The turbopump test was conducted under the Integrated Powerhead Demonstrator (IPD) project, a joint venture between NGLT and the US Air Force Research Laboratory's Integrated High-Payoff Rocket Propulsion Technologies programme. Aerojet also tested a oxidiser preburner. Both tests are intended to support development of a hydrogen-fuelled, staged-combustion rocket engine.
Northrop Grumman, meanwhile, has tested a subscale composite hydrogen fuel tank built under the NGLT programme. The quarter-scale tank was filled with liquid hydrogen, pressurised and subjected to simulated launch loads. The tank, which will be filled, loaded and drained 40 times to demonstrate reusability, uses a barrier film to prevent hydrogen seeping into the composite walls, which have a perforated honycomb design to safely vent hydrogen to space if fuel does seep past the film.
Source: Flight International
