GRAHAM WARWICK / WASHINGTON DC
Capsule or lifting body would meet crew rescue vehicle requirements, but modifying launch facilities will be challenge
NASA plans to accelerate development of a simplified Orbital Space Plane (OSP) to support the International Space Station (ISS). Requirements issued to industry bring forward the initial crew-rescue capability from 2010 to "as early as 2008 or sooner", with the aim of starting two-way crew transfer operations in 2010, but no later than 2012.
Either a capsule or lifting-body design could meet the schedule requirement, says OSP programme manager Dennis Smith. "The outer mould line is not the driver," he says, adding that modifying commercial launch facilities to handle the OSP is likely to be the greatest challenge to the accelerated schedule.
Smith says the timetable is driven by the need to increase the science performed on the ISS and to improve the safety of its crew. The Level 2 requirements released to industry call for a vehicle able to carry four crew, which, combined with the three-person Russian Soyuz, would allow a seven-strong ISS crew. "Above seven, a Space Shuttle would be attached to the Station," he says.
The Level 2 requirements narrow the scope of the OSP design and address guidelines for safety, launch, emergency-return and crew-rescue missions, mission frequency, on-orbit duration, contingency cargo, and docking with the ISS. A request for proposals will be issued to OSP bidders Boeing, Lockheed Martin and Northrop Grumman/Orbital Sciences in late November, with a contract award due in early August.
Smith says the contract will cover development and production of crew return and crew transfer vehicles, and the first two years of operations. NASA has yet to release its budget estimate for the OSP programme, which still requires approval from the White House and Congress. "It will take more money to do the acceleration," he says.
The Level 2 requirements do not dictate an OSP configuration, but "drive towards a simple, focused design", says Smith. "They are focused on safety, getting to the ISS as quickly as we can, and being autonomous without a crew but with manual control giving a crew override." The goal is to reach the ISS within a day, with a two-day margin for successful docking.
While a lifting body would provide greater cross-range capability on re-entry, a capsule may be safer, Smith says. "If we lose control of a winged vehicle, how do we protect the crew? Can we remove the wings and have the fuselage stay intact?"
The initial rescue vehicle, to be launched umanned, will require a crew escape capability for the descent phase. The evolved crew transfer vehicle will require an abort capability for the launch and ascent phase. "The bidder cannot use escape as a level of redundancy. They need at least one abort scenario available, for ascent and re-entry," says Smith.
NASA says the next Space Shuttle launch will not be made before the third quarter of next year, possibly later, and the STS 114 Atlantis mission will not be able to demonstrate all the return-to-flight requirements recommended by the Columbia accident investigation board. A second mission may be necessary to refine the safety measures. It is likely Atlantis will dock at the ISS but not conduct any assembly work, which could be delayed to mid-2005 if a second orbiter inspection and repair demonstration flight is required. About 47.7t of ISS components are awaiting launch.Source: Flight International
