The main runway 22 at Edwards Air Force Base (EDW) in California has been removed as a landing option for STS-124, through to STS-126.
A refurbishment of the main strip means orbiters – should they require the alternative landing site at the end of their upcoming missions – will use the new temporary runway 22, which will also require new braking and rollout techniques.
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New Edwards Runway:
Edwards is home to the US Air Force’s 412th Test Wing and is currently operated by the 95th Air Base Wing. The base is strategically situated next to Rogers Lake, an endorheic desert salt pan, and is the home to NASA’s Dryden Flight Research Center (DFRC).
The new 12,000 x 200 ft runway is shorter and narrower, and runs parallel to the main runway (15,000 X 300 ft). The temporary use of the new, smaller runway is required while the primary runway is under repair. Flight specific rules will take affect, beginning with STS-124, which will govern the use of the new runway.
Though 3,000 feet shorter than the primary runway, an orbiter will still have lots of margins for her rollout. However, as a precaution, engineers have been looking into the design upper limits on the amount of heat reacted in the carbon-carbon brakes, should there be a problem with the brakes during rollout.
‘The overall increase in risk to the SSP (Space Shuttle Program) is assessed as low,’ noted one of several presentations on the change. ‘There are no rollout margin issues. Brake assemblies are certified to 82M ft-lb for one-time use.’
The previous landing – with Endeavour at the Kennedy Space Center’s Shuttle Landing Facility (SLF) at the end of STS-123 – only used brake loads of 17 MFt-lbs, though rollout was one of the longest in shuttle history.
Such is the margin with a 15,000 ft runway, an orbiter could land and come to a stop even without the deployment of the drag chute. More braking would be required should that failure occur on the new 12,000 ft runway, noted as causing the potential for ‘melted fuse plugs, and damaged brake actuator, wheel and axle assemblies.’
Should, in the unlikely event, the orbiter suffer brake damage, engineers back at KSC have spares in supply.
‘Main Landing Gear (MLG) Axle: 2 MLG axles in Logistics, 1 piston/axle assembly in Logistics. Brake Assembly: 4 brake assemblies (2 ready for use, 2 in process). Brakes are sent for refurbishment after 8 landings.
‘Wheel Assembly: 30 total flight assets available for use. Wheels are flown 10 times before they are sent back to Goodrich for refurbishment. New improved wheel assemblies in service since STS-121.’
One of the changes to landing will be a delay of braking from 5,000 ft remaining to 4,000 ft remaining. This will reduces brake energy by allowing vehicle drag to decelerate vehicle for additional 1,000 ft of rollout.
The highest risk to an orbiter on landing via excessive use of the brakes is the dramatically titled ‘Fire/Explosion caused by orbiter’s hot brakes,’ caused by ‘brake pressures applied by the crew due to environment, abort landings and/or crew error after rollout resulting in high brake energies.’
However, this risk is deemed ‘improbable’ – with the likelihood of experiencing worst-case critical damage is assessed as ‘extremely remote’ in the life of the program. ‘The cause remains improbable/critical (Controlled).’
Discovery will be landing much lighter than she’ll be launching, after her huge JAXA Pressurized Module is handed over for installation to the International Space Station (ISS). However, the main area of interest is with STS-125 (Hubble) and STS-126 (Logistics), both returning with the bulk of their payload.
‘Greatest concern is for heavyweight landings (STS-125 and STS-126),’ confirmed one of the presentations. However, this should still remain no issue for Atlantis and Endeavour respectively. ‘Assess overall increase in risk to the SSP as low based on the high reliability of the drag parachute and delayed braking procedures.’
Edwards is classed the primary back-up landing site for the shuttle, with KSC always preferred, and White Sands deemed as distant third choice. The previous Edwards landing for an orbiter was with Atlantis after STS-117.
The new landing strip is an asphalt/concrete runway – with the First 1000 ft after threshold are concrete (Air Force requirement). Existing concrete taxiways A, B, and C bisect runway.
It also has an additional 1,000 ft over/under runs are shuttle load bearing. In Sept 2006, Space Shuttle Program decided against an additional 1,000 ft of usable runway due to funding.
The new runway is still undergoing some of the final touches before becoming fully operational, which will mark the handover from the old runway – which will then begin its refurbishment process.
“Runway status: Runway concrete work is complete. Aim point markings are complete. PAPI lights are installed and checked out. Ball/bar lights have been fabricated,” added one of the presentations, confirming work will be fully completed in time to support STS-124 – should it be required.
“Week of April 21: DFRC completes installation of EDW Temporary runway landing aids. Complete runway asphalt work. Begin runway striping.”
Shuttle landings have been simulated at all previously available runways via the Shuttle Training Aircraft (STA), which includes runways 4, 15, 22 and 33.