ET Project - Tin Can Uses This section considers what is blithely refered to as Tin Can Uses. In spite of being less than technical, this title is the best overall classification of these type External Tank Applications. The following section will discuss uses of the ET as the basis of orbital habitats, storage facilities, hangars, and other ’can' type uses. This class of tank applications is likely where the ET can be put to the first use and possibly best advantage by the future space program. I. Storage containers As mentioned previously, the External Tank contains two separate tanks designed to hold liquid hydrogen and oxygen before and during STS launch. The respective capacities of 53,500 and 19,500 cubic feet are important in this context. NASA has a need for storage of some sort of volatiles on orbit to fuel Orbital Transfer Vehicles (OTVs), supply Space Station needs, and refuel existing and planned satellites. The current (Sept 1985) requirement for volatiles storage does not yet require a large storage facility on orbit. There is also a NASA projected requirement to supply 2.5 million pounds of cryogenic propellent in a ten-year period that a scenario which utilizes the External Tank can fill far quicker and cheaper than any other plan (69). A. Cryogenic storage On-orbit storage of cryogenics in the ET is possible. The tank can be wrapped with mylar reflective blankets to retard boiloff. This technique should be quite effective giving untended storage times of both residuals and additional stored cryogenics on the order of months (46). A single ET can provide all the volume required for storage of volatiles on-orbit for a space station or an OTV servicing operation. The tank can be stabilized in a gravity gradient mode either free or attached to a tether to keep the liquid on the 'bottom' available for use (30). Cryogenics are also useful in providing backup power. A set of fuel cells designed for emergency operation can use residual or stored cryogenics as a separate backup power supply for the station. Fuel cells are mature technology with which we have extensive experience in space. The problem with the on-orbit storage of cryogenics in the ET is that there is simply too much volume available in the ET oxygen and
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