calius@SU-STAR.ARPA (Emilio Calius) (12/24/85)
The idea of venting away the residual fluids in the ET is an almost criminal waste of what may be (in the near-term) a precious resource. Fortunately, Martin Marietta, which is responsible of the ET, has a NASA contract to study ways of reclaiming the unused propellants. From SPACEFLIGHT, Nov. 85, p. 391: "... capable of reclaiming up to 11,400 kg of propellant per mission depending upon the Orbiter's payload. Unused propellant on missions to date has ranged from 4300 kg to 12,800 kg of the total 726,000 kg carried aloft by each tank. Under current estimates, the Space Station would require about 114,000 kg of LH2 and LO2 per year". That means that recovering the fluids from 10 launches/year (out of the 14 planned) would be enough. "The system includes 2 to 4 propellant collecting tanks in an aft cargo carrier that would be attached to the rear of the ET. After the Shuttle's main engines cut off, residual liquid oxygen and hydrogen would drain from the ET into the collection tanks with the help of a thrust system designed for the weightlessness of orbit. Once filled, the scavenging tank assembly would separate from the aft cargo carrier as a self-contained, remote-controlled vehicle with it own propulsion system. Once this fuel-laden vehicle has moved into position along- side the Space Station, technicians aboard the station would send an Orbital Maneuvering Vehicle to shepherd it to the station's fuel depot for transfer of the reclaimed propellant to permanent tanks. The scavenger vehicle would return to Earth in the cargo bay of the Shuttle for reuse on later missions. The ET and the aft cargo carrier would reenter the atmosphere to break apart and fall harmlessly into an ocean orea, as is the case for the tank on current Shuttle flights." Well, I don't like the last part of their plans, but it is at least a hopeful sign. However, it 's a long way from flight hardware. Emilio P. Calius Aero/Astro Dept. Stanford Univ. ------