TheExtended Duration Orbiter (EDO) program was a project byNASA to prepare for long-term (months)microgravity research aboardSpace Station Freedom, which later evolved into theInternational Space Station. Scientists and NASA needed practical experience in managing progressively longer times for their experiments. The originalSpace Shuttle configuration usually provided a week to ten days ofspaceflight. Several research projects and hardware components were part of the project, of which the EDO-pallet was one of the most visible, contracted byRockwell International.^[1]

The first orbiter outfitted with the EDO hardware configuration wasEndeavour, during its construction, and its last EDO flight wasSTS-67, in 1995.^[1][2]Endeavour's EDO modifications were removed in 1996 as part ofroutine maintenance, to reduce the orbiter's weight prior toSTS-89.^[1]Columbia was outfitted for EDO flight during its maintenance period from August 10, 1991, through February 9, 1992, prior toSTS-50, which was the first EDO flight.^[2][3] From 1992, through 1994,Atlantis went through a maintenance period, during whichAtlantis was modified to have the provisions needed for EDO capability, but NASA chose not to proceed with the final modifications, andAtlantis never had EDO capability.^[1] The EDO-pallet used in these orbiter configurations was destroyed in the 2003Columbia disaster.

The Extended Duration Orbiter Cryogenic kit (EDO-pallet or CRYO) was a 15-foot-diameter (4.6 m) equipment assembly which attached vertically to the payload bay rear bulkhead of anorbiter, and allowed the orbiter to support a flight of up to 16 days duration.^[1] The equipment included cryogenic tanks, associated control panels, and avionics equipment. AlthoughAtlantis was partially upgraded to accommodate the EDO, onlyColumbia andEndeavour actually flew with the pallet. The pallet made its debut onSTS-50, and was lost onSTS-107 in 2003.^[4]

Initially, NASA considered adding a second EDO pallet toEndeavour, placed in front of the first, for a total of thirteen tank sets, that would have allowed an orbiter to remain in space for 28 days, but managers decided against it when the International Space Station assembly began, and instead removed the EDO capability from the orbiter, to reduce its weight and allow it to carry more cargo to the ISS.^[1][5]

No replacement for the pallet was planned, since theStation-to-Shuttle Power Transfer System provided much of the same abilities, and the 2011 retirement of the shuttle fleet made it unnecessary.

The EDO tanks stored 368 pounds (167 kg) ofliquid hydrogen at −418 degrees Fahrenheit (−250.0 °C), and 3,124 pounds (1,417 kg) ofliquid oxygen at −285 degrees Fahrenheit (−176.1 °C). Total empty weight of the system was 3,571 pounds (1,620 kg). When filled with cryogens, the system weight was approximately 7,000 pounds (3.2t).^[1][6]

The EDO pallet was designed to augment the orbiter's endurance for prolonged missions by supplying additional hydrogen and oxygen for itsfuel cells. These fuel cells, in turn, convertedhydrogen andoxygen into electrical energy essential for the orbiter's operations.^[7] For instance, during STS-80, 5,856 kWh was produced from 3,989 lb of oxygen and 502 lb of hydrogen.^[8]: 24 For STS-50, 6,204.7 kWh was generated from 4,367 lb of oxygen and 550 lb of hydrogen.^[9]: 12 In comparison,STS-77, a mission without the EDO pallet, yielded 3,924 kWh from 2,745 lb of oxygen and 346 lb of hydrogen.^[10]: 20

Another byproduct of the fuel cell operation was potable water. STS-77 produced 3,091 lb,^[10]: 20 while missions utilizing the EDO pallet, such as STS-50 and STS-80, yielded 4,914.6 lb^[9]: 12 and 4,492 lb,^[8]: 24 respectively.

Missions incorporating the EDO pallet provided extended opportunities for scientific research. They enabled detailed studies in areas likemicrogravity,life sciences,terrestrial observations, andastronomical observations. They also facilitated an understanding of human adaptability in reduced gravity conditions.^[7]

The following missions used the EDO pallet:

Prior to the EDO project, no shuttle had flown a mission longer than 10 days. Since space travelers may faint when they stand up (orthostatic intolerance) after returning to normal gravity even after short flights, and muscle strength may be reduced, the EDOMP project focused on ensuring that the crew could land the orbiter, and exit from it without help after a 16-day flight. Astronauts on 40 shuttle flights (STS-32 throughSTS-72) participated in 36 EDOMP investigations. The results of these investigations were used to make rules and recommendations for 16-day flights. Several types ofexercise devices (i.e. atreadmill, acycle ergometer, and arower) were among the devices and procedures developed to prevent the de-conditioning of the body that occurs during space flight. The crew transport vehicles, in which astronauts were transported after landing, were built to enhance medical capabilities at the landing site, as well as crew comfort and safety. A database of 125 formal publications, and 299 abstracts, technical papers, and presentations, also resulted from the EDOMP.^[12] The project saw its successor in theISS Medical Project.^[13]

• Manual Apparel Cleaning System - A system for laundering selected items of clothing.^[14]
• An automatedFault Detection, Isolation, and Reconfiguration-system (FDIR) that would support the shuttles for up to 28 days.^[15]
• Extended Duration Orbiter Waste Collection System.^[16] A similar system was later added to ISS as the ISS Waste Collector Subsystem.^[17]
• Extended Duration Orbiter Regenerable CO₂ Removal System.^[16]
• Medical Extended Medical Enterprise (MEME).^[18]

• List of Space Shuttle missions

• "Extended Duration Missions". NASA.

• Space Shuttle program
• Spacecraft components

• Articles with short description
• Short description matches Wikidata
• Use American English from January 2014
• All Wikipedia articles written in American English