to use the ET in orbit must address this problem. A quick solution would be to install small thrusters that use the boiloff of residual cryogenics to insert the ET in a very long lived (200 - 500 nm higher) orbit. Other solutions to this problem are possible and vary depending on the planned on-orbit use of the ET. They are also not particularly expensive. The second problem is possible contamination due to outgassing of the Spray-On Foam Insulation (SOFI). This may prove to be a pollution problem for a small number of proposed space based operations. However, it will require further study. There are several relatively inexpensive enhancements to the ET that can be purchased that will enhance STS operations. The most important of these is the AFT Cargo Carrier (ACC). The ACC is constructed using ET tooling and attaches to the aft end of the hydrogen tank. Cost of the ACC is between $150 - 250 million and it can fly three years after the go-ahead is given. The ACC is designed for minimal impact to the ET, orbiter, and operations. It provides an additional cargo volume measuring 27.5 feet by 20 feet for payloads. This is valuable to operations because it deals with the volume restriction imposed by the orbiter payload bay. In other words, there is normally additional mass to orbit capability available in each STS launch. A typical example would be a Spacelab flight. The ACC can carry additional payload or primary payload to orbit. This gives the orbiter additional payload capability that can be sold to paying customers for minimal cost. II. Tin Can Uses The ET can be used as a ’tin can’ in orbit for a number of applications. These include storage facilities for liquids, gases, and prepositioned vehicles. The ET/ACC combination can be launched with the ACC as a fully functioning manned space station. This type vehicle has an enormous expansion space inside and outside the ET itself for a variety of orbital applications. The ET/ACC as a space station can also be flown with a single shuttle launch. This capability will allow any number of potential customers to purchase independent space stations for the cost of two or three generic commmunication staellites. Potential customers for this capability include DOD, corporations, foreign nations, and private consortiums.
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