NASA's Kennedy Space Center Shuttle landing runway has been modified to reduce launch delays
Tim Furniss/KENNEDY SPACE CENTER
Space Shuttle launch delays may be reduced by more than 50% because of extensive modifications to the 4,570m (15,000ft)-long grooved-concrete runway at NASA's Kennedy Space Center (KSC) in Florida. The changes may increase the present 15kt (28km/h) cross-wind constraint, to 20kt for return-to-launch-site (RTLS) aborts, in the event of a problem soon after launch.
Weather restrictions, which call for a cancellation if the cloud deck over the KSC for an abort landing is below 8,000ft, may also be reduced to a deck level of 5,000ft. Improving the chances of lifting off on time will be especially useful for international space station launches, which will require 5min launch windows.
The resurfacing of the Shuttle Landing Facility runway follows successful tests, using NASA's CV-990 Landing Systems Research Aircraft (LSRA) with Shuttle tyres and a new runway-surfacing technique.
The 2,500m-long roll out portion of the 90m-wide KSC runway is cross-grooved heavily, to prevent aquaplaning and to promote the rapid draining of heavy Florida rain. The runway slopes downwards either side from the centreline by 600mm.
CROSS-GROOVES
The 1,000m-long stretches at each end of the runway had already been smoothed to remove the cross-grooves, following recommendations by the commission, which investigated the Challenger failure. The commission also called for improvements to the Shuttle landing gear. The modified "corduroy" ridges are smaller, than those they replaced and run along the length of each end of the runway, rather than across its width. The runway also has a 300m-long safety overrun at each end.
The routine 190kt landings by the Shuttle orbiters Columbia, Discovery, Atlantis and Endeavour within the 15kt crosswind limit already cause heavy wear on the tyres, mainly those on the main gear.
Smoothing the runway will reduce this natural wear, but raising the crosswind limit could also increase the potential for wear, particularly during steering and braking. The ridges and grooves have been smoothed in the hope that 20kt crosswind landings will not increase tyre wear.
"Shuttle launches involve complicated choreography," says Space Shuttle operations director Brewster Shaw. "This includes not only the conditions that apply to launching out of the atmosphere and into space, but also weather and winds at several locations around the world in case problems force us to make an immediate landing," adds the three-time Shuttle astronaut.
Computer and simulator engineering analysis of the whole system - not just crosswinds - has still to be completed to ascertain the extent of the increased crosswind limit. In addition, 15kt crosswind limits may remain for end-of-mission landings in which the commander and pilot may be physically and mentally fatigued.
The CV-990 LSRA was highly modified to duplicate the landing weight, speed and side slip of the Space Shuttle. The converted aircraft carries a landing-gear test fixture, which can be used to test orbiter tyres at up to 63,500kg of load. It was developed originally as a Space Shuttle systems testbed, but it can be used to test a variety of aircraft-landing systems.
During the KSC tests, the LRSA team studied three different runway surfaces to determine the best landing conditions. Test strips, using different smoothing techniques, were ground into the runway and evaluated to determine wear, water drainage and overall texture.
A re-surfacing technique using a Skidabrader machine was chosen and the KSC runway was re-surfaced. The Skidabrader - resembling an ice-rink resurfacer - propels tiny steel shot on to the runway to pulverise the rough surface and create a much smoother finish, but still maintains the runway's ability to drain rainwater quickly.
The CV-990 tests are part of a comprehensive effort by the Shuttle programme to evaluate crosswind limits within which an orbiter can safely land and complement data collected during actual Shuttle landings. These data are being used to obtain a better understanding of orbiter handling-characteristics at landing speeds in various crosswind conditions.
"If we can save the Shuttle programme eight days of delay, we have paid for the entire LSRA programme," says Christopher Nagy, chief CV-990 engineer. The cost to modify the aircraft into a test vehicle and operate it through this fiscal year was $12 million.
"The orbiter and all of its systems, with the exception of the tyres, were designed and built to handle a 20kt crosswind," says CV-990 programme manager, Robert Baron. NASA has logged 101 flights of the CV-990 during testing at the KSC since the aircraft was modified. Along with improving orbiter landing-capabilities, the CV-990 test team produced data to help update Space Shuttle simulators used by NASA's Johnson Space Center, Houston, Texas, and Rockwell International, the Shuttle orbiter main contractor.
Although testing at the KSC is complete, additional flights are planned at Edwards to test Shuttle tyres at low air pressures and on the lakebed runway.
Source: Flight International
