CAPE CANAVERAL, Fla. -- NASA is moving closer to another return to flight, this one already more than two-and-a-half years in the making.
An X-43A scramjet test vehicle, part of the space agency's Hyper-X program, is being readied for a captive carry flight beneath the wing of a B-52 as early as Saturday.
Staged from Edwards Air Force Base, Calif., the exercise will serve as a dress rehearsal for the targeted Feb. 21 air launch of the combination X-43A and Orbital Sciences Pegasus booster over the Pacific Ocean.
Rain showers forecast for Saturday over the Antelope Valley may prevent the weekend captive carry flight, but the test team was moving forward on Friday with their plans, officials said.
If a review of the dress rehearsal shows all went well, managers likely will give a go for the launch -- an event that will mark the first flight of an X-43A since June 2, 2001, when the vehicle was lost moments after the Pegasus booster was ignited.According to a NASA investigation there was no single root cause of the failure. Engineers have since modified the control system of the booster and adjusted the flight plan -- for example, dropping the vehicle at 40,000 feet instead of 20,000 feet as was done in 2001.
After the vehicle is dropped, the modified Pegasus booster is to loft the X-43A to a top altitude of about 95,000 feet and moving at a speed of Mach 7 -- or seven times the speed of sound.
Moving at hypersonic speed, the X-43A will separate from its booster and fly under its own power on a preprogrammed path that ultimately will send it gliding to impact in the ocean.
The X-plane's power is expected to come from the operation of a supersonic combustion ramjet engine, better known as a scramjet.
The basic idea of a scramjet is that by moving the essentially hollow engine at such speeds, enough of the thin air of the upper atmosphere will be forced into the chamber, pressurized and then ignited with the help of hydrogen fuel.
If it works the X-43A will become the first air-breathing hypersonic vehicle in free flight.
The vehicle being tested now is the second of three planned. The first was lost in the 2001 incident, while the third is to be flown up to Mach 10.
NASA hopes the technology could lead to new vehicles that will provide faster, more reliable and less expensive trips into Earth orbit.
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