By THE SILVER INSTITUTE LETTER, VOLUME VI, Number 3, March 1976
Astronauts for the first test flights of the Space Shuttle . . . the vehicle that eventually will commute among orbiting satellites, and between earth and space . . . have been named by the U.S. National Space Administration (NASA).
Water wastes will be recycled in Shuttle flight, and silver's first job will be to treat hydrogen-saturated water coming from Shuttle fuel cells; this water will pass through a tubular device of palladium and silver alloy; tube wails will be 10 mils (0.25 ram. or 0.01 in.) thick. Under pressure of 60 psi at a flow rate of 7 liters/hour, 85% of the hydrogen will diffuse out through the palladium-silver tube walls and be vented in the space vacuum outside the tubes. The device is made by Life Systems, Inc., 24755 High Point Rd. Cleveland, Ohio 44122.
From the silver-palladium tubes, water will flow to a purifying unit where silver will perform its second task. Less than an ounce of silver bromide in a cylinder less than 20 cm. (8 in.) long will eliminate bacteria, including Pseudomonas A and Type IIIA bacteria in 15 minutes or more, NASA scientists report. By establishing 100 parts of silver in a billion parts of water as hygienic for drinking in the Shuttle, NASA eliminates the need for the 1,000 to 1.500 ppb of chlorine generally used for purification.
This compact, efficient water purifier is the Advance Prototype Silver Ion Water Bactericide System, made by Chemtric Inc., 9330 West Willams St., Rosemont, Illinois 60018. The unit will provide Shuttle crews with 120 liters (32 gal.) of pure water daily for all uses within the Shuttle and for backpacks when the astronauts work outside the vehicle in space; eventually, astronauts will leave their Shuttles to provide maintenance to satellites while they are in orbit; and to recapture scientific instruments in space, stow them in the Shuttle's 60x15 ft. (18x5 meters) cargo bays, and return them to earth.
The basic value of the Shuttles is that each vehicle will make repeated launches from earth and many cruises in space, carrying a payload each time. This will be cheaper than the cost of a big expendable launch vehicle for each job to be done.
The Shuttles are being made by the Space Division, Rockwell International, Downey, California 90241. The firm specifies silver for many other functions in the vehicles: a five-kilogram (11 lbs. or 161 tr. oz.) sterling silver ring will serve as the seal in an oxygen turbopump inducer in the main engine; silver bearings on cargo doors' hinges will withstand the 760? C (1400? F) heat that will be experienced as the Shuttle re-enters earth's atmosphere; and silver will be used in electronic circuits. Why?
Silver makes the best seal because it's smooth, ductile, and resists deterioration from oxidation, chemicals and extreme temperatures. It makes the best bearings because it has dry-lubricant properties and diffuses heat. And it makes the best electronic circuits because it is an excellent conductor, and switches slide reliably over the smooth, clean surface.