cargo bay. This image is from STS-91. The front of the Shuttle is to the left of the picture. There were no stringent requirements to qualify for participation in the GAS program. However, each
payload was required to meet specific safety criteria, have been screened for its propriety, as well as being evaluated for its educational, scientific or technological objectives. These guidelines preclude commemorative items, such as medallions, that are intended for sale as objects that have flown in space.
NASA's
Space Shuttle program had specific standards and conditions relating to GAS payloads. Payloads were required to have fit into NASA standard containers and weigh no more than . Two or more experiments could have been included in a single container if they fit while not exceeding weight limitations. The payload must have been self-powered, as experiments could not draw on the Shuttle orbiter's electricity. In addition, the crew's involvement with GAS payloads was limited to six simple activities (such as turning on and off up to three payload switches), due to the fact that crew activity schedules do not provide opportunities to either monitor or service GAS payloads in flight. The cost of this unique service depended on the size and weight of the experiment. Getaway specials of and cost
$10,000; and , $5,000; and and , $3,000. The weight of the GAS container, experiment mounting plate and its attachment screws, and all hardware regularly supplied by NASA was not charged to the experimenter's weight allowance. The GAS container provided internal
pressure, which could be varied from near
vacuum to about one
atmosphere. The bottom and sides of the container were always
thermally insulated, and the top may have been insulated or not, depending on the specific experiment. A lid that could be opened, or one with a window, may be required, and were offered as options at additional cost. The GAS containers were made of
aluminum, and the circular end plates are 5⁄8 inch (16 mm) thick aluminum. The bottom of the container were reserved for NASA interface equipment, such as
command decoders and
pressure regulating systems. The container was a pressure vessel that could be evacuated before or during launch, or on orbit, and could be re-pressurized during re-entry, or on orbit, as required by the experimenter. The getaway bridge, which was capable of holding 12 canisters, made its maiden flight on
STS-61-C. The aluminum bridge fit across the payload bay of the orbiter and offered a convenient and economic way of flying several GAS canisters. == Example of GAS experiments ==