NASA has outlined a three-pronged Space Shuttle development roadmap. It will result in significant upgrades in the near term, a competition for a second generation spacecraft in 2005, and an ongoing aerospace technology effort for a third and fourth generation reusable launch vehicle to 2020 and beyond.

"We will make a decision around 2005 on holding a competition and looking at alternatives to the Shuttle," says NASA associate administrator for spaceflight Joseph Rothenberg. "We will plan demonstrators to see what needs to be in place technically and, by 2008-9, we will have an indication of what will be possible to replace the Shuttle, or whether to keep it going. At that point, we will begin to discuss phasing out the Shuttle."

Rothenberg says the NASA competition will "look at the whole picture" and will analyse technical capabilities, as well as wider issues such as commercialisation, ownership and liability.

For now, NASA is focusing on a wide range of Shuttle upgrades to enhance safety, improve performance and reduce cost. NASA Ames director Dr Henry McDonald says: "The fact remains there is no replacement on the horizon and we are looking at 10, maybe 20, years of future life for the Shuttle." The Shuttles were originally certificated for 100 flights each and, on average, they have made about 25, according to NASA.

The upgrades will come out of the fiscal year 2000 budget, and will be in place by 2005. Major upgrades planned, or under study, include electric auxiliary power units to replace the maintenance-intensive hydrazine-powered auxiliary power unit, and the replacement of the alkaline fuel cells with more powerful proton exchange membrane fuel cells.

A Space Shuttle Main Engine Advanced Health Management system is also being proposed, to increase safety and reduce turnaround costs. Another upgrade planned is a switch of the Shuttle's main propulsion system propellant valve from pneumatic to electromechanical actuation.

Other areas fighting for budget allocation include those of avionics and cockpit safety improvements, a more durable belly tile, changes to the main landing gear tyres and studies of improved abort systems.

Even more ambitious upgrades are envisioned, including the potential development of fly-back boosters. Together with the current suite of planned enhancements, NASA believes that the revamped spacecraft could itself become a leading contender for the second generation Shuttle.

Source: Flight International