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Aviation History
1999
1999 - 2349.PDF
£f^4t€»£» SMVWtlLS DIE yj^LVrtdaSNlf ¥vfff%n£pfCME At the first Space Shuttle Development Conference, held at the NASA Ames Research Center, California, between 28 and 30 July, the problems which surrounded last month's Columbia STS93 Shuttle mission - together with the threat of massive reductions in NASA's budget - provided an appropriate backdrop for intense debate over the future of the space vehicle. GUY NORRIS REPORTS Ames team looks at glideback booster ANASA AMES team is study ing a novel means of retriev ing the Space Shuttle's solid rocket boosters (SRBs). It would use an oblique wing to enable the boosters to glide back autonomously to Kennedy Space Center for a con trolled landing rather than splash down into the ocean for recovery. The study is an alternative to the fly-back booster options being evaluated by Boeing and Lockheed Martin under contract to NASA Marshall Space Center. Dr Steve Smith, the NASA Ames team leader, believes the glideback op tion could save up to 13,600kg (3 0,0001b) a booster in terms of the equivalent fuel load and engine weight. Given the two current SRBs, this would save "a Space Shuttle payload just in fly-back fuel", he says. The SRBs normally burn out and separate from the Shuttle 42 km downrange at 2 5 2,000ft/min (l,280m/s). "That's goingMach 4 in the wrong direction," says Smith. The study asks: "Can it be turned, can you glide back that far?" The answer, according to pre liminary studies, is yes, he adds. Smith believes the wing- equipped SRBs could glide in from a turnback range of 280km and "make it home with about 2,500ft [760m] to spare". The 37m-span wing would be mounted flush with the casing of the 45.5m-long booster for lift-off and would begin unsweeping at aboutM3 and an altitude of 80,000- 90,000ft (24,400-27,450m), a few seconds after separation. The sweep angle would briefly stabilise at around 70° before open ing up to 65° for the pull-up manoeuvre atMl .7. On the return leg, it would decrease sweep from 45° to 30° as the SRB decelerates through Ml. Sweep angle would quickly be reduced to 0° as the wing extended for maximum lift for the long glide home. • Solid rocket boosters/ Reusable solid rocket motors Proposed Shuttle upgrades Payload and system integration Ground support Advanced technology Orbiter avionics Cockpit Data processing Communications Navigation Power subassemblies Structures and mechanisms FLIGHT Thermal protection NASA maps out plans for Space Shuttle evolution NASA HAS OUTLINED a three-pronged Space Shuttle development roadmap. It will re sult in significant upgrades in the near term, a competition for a sec ond generation spacecraft in 2005, and an ongoing aerospace technol ogy effort for a third and fourth generation reusable launch vehicle to 2020 and beyond. "We will make a decision around 2 00 5 on holding a competition and looking at alternatives to the Shuttle," says NASA associate administrator for spaceflight Jo seph Rothenberg. "We will plan demonstrators to see what needs to be in place technically and, by 2008-9, we will have an indication ofwhat 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 whol e picture" and will analyse technical capabilities, as well as wider issues such as commercialisation, owner ship and liability. For now, NASA is focusing on a wide range of Shuttle upgrades to enhance safety, improve perfor mance and reduce cost. NASA Ames director Dr Henry Mc Donald 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 up grades planned, or under study, include electric auxiliary power units to replace the maintenance- intensive hydrazine-powered aux iliary 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 turn around costs. Another upgrade planned is a switch of the Shuttle's main propulsion system propellant valve from pneumatic to electro mechanical 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 po tential development of fly-back boosters. Together with the current suite of planned enhancements, NASA believes that the revamped Orbiter spacecraft could itself become a leading contender for the second generation Shuttle. • 28 FLIGHT INTERNATIONAL 11 - 17 August 1999
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