Tim Furniss/LONDON
NASA's Space Shuttle is catching up with the space age. Honeywell Space Systems of Arizona has delivered 11 flat panel displays for the Space Shuttle Atlantis, the first of NASA's fleet of four orbiters to undergo a cockpit display upgrade.
Honeywell's Multifunction Electronic Display Subsystem (MEDS) has a similar design to the company's liquid crystal flat panel displays technology on the Boeing 777. The system will replace the Shuttle's electro-mechanical and cathode ray tube displays.
The MEDS displays are being tested in the Shuttle Avionics Integration Laboratory (SAIL) in Houston. They will be used for the first time in 1999, when the STS92/Atlantis, commanded by US Air Force Col Brian Duffy, takes off on an International Space Station (ISS) assembly mission.
The Shuttle first flew in 1981 and a glass cockpit was proposed for it more than 10 years ago. Its belated introduction has resulted in the unusual case of pilot astronaut recruits, trained with glass cockpits, joining NASA and having to learn the old displays before their first missions.
The MEDS is being installed in the Atlantis during its $70 million refurbishment at Boeing in Palmdale, California, which also includes the addition of a satellite based navigation system.
Each orbiter is modified and refurbished every three years. The Atlantis - subject to the most extensive modification yet - is receiving a comprehensive structural inspection and more than 100 modifications designed to reduce programme maintenance costs and improve operations, safety and reliability.
Under contract to United Space Alliance, a team of more than 350 Boeing technicians and engineers will take the vehicle apart and re-assemble it.
The MEDS is the only space-qualified flat panel display in the world. It will provide Shuttle crews with information such as attitude display, Mach speed and horizontal situation indicators. When the MEDS is installed, the Atlantis forward flightdeck will have nine displays, while two MEDS displays will be installed in the aft flightdeck to support payload operations. Information will be interchangeable between screens, depending upon mission needs, allowing crews to select the display format that best suits their needs.
"The change to MEDS is necessary because present electromechanical devices are becoming obsolete and increasingly expensive to maintain," says Russ Turner, Boeing Reusable Space Systems vice-president and general manager. "Besides reducing maintenance costs, the MEDS will reduce vehicle weight and power consumption, improve Shuttle reliability and performance and be capable of expansion for future applications," he adds.
MEDS hardware consists of 11 identical full colour liquid crystal multifunction display units (MDUs). Four of these directly replace the four monochrome units of the old system. Two MDUs each replace the commander (CDR) and pilot (PLT) flight instruments; one MDU replaces the on orbit manoeuvring instruments at the aft flightdeck and the remaining two replace the CDR and PLT status displays. A fault tolerant architecture is used to drive these displays under the control of four integrated display processors, which replace the four original display electronics units. Four analogue to digital converters and 16 databus couplers complete the MEDS. The command and data entry keyboards, as well as the rotational and translational hand controllers, and most of the other cockpit switches, remain unchanged.
The SAIL is running extensive integration and verification testing of the MEDS to confirm that its operation with the rest of the Shuttle avionics in a simulated flight environment is functionally identical to that of the old displays.
The MEDS could also assume other roles, such as showing system or circuit diagrams, and providing graphic displays of rendezvous and docking situations.
The Atlantis is also set to become the first orbiter to be guided solely by satellite based navigation. The current TACAN navigation system will be removed and replaced with a triple redundant system that operates through signals from the Boeing Navstar global positioning system (GPS) satellites.
The GPS will provide accurate vehicle attitude and location data. It promises to reduce Shuttle programme costs by eventually allowing removal of several ground stations at NASA's Kennedy Space Center in Florida as well as at the transatlantic abort landing sites, which are becoming obsolete and costly to maintain. Together with other planned navigation enhancements, the GPS could one day enable Shuttle landings in poor visibility.
An additional series of modifications will enable the Atlantis to join sister ships Discovery and Endeavour in supporting ISS construction, which begins in September. The docking system which the Atlantis has used for seven missions to Russia's Mir space station will be modified to become a fully functional airlock, complete with spacesuit services and crew communications capabilities.
Source: Flight International
