NASA hopes to make a second attempt to fly the hypersonic X-43A Hyper-X test vehicle around September next year and has revealed details of proposed changes to the launch profile.

The test team believes that by modifying the trajectory of the Orbital Sciences-built Pegasus booster, which accelerates the X-43A to its launch condition, it may avoid the problems which caused the first attempt to fail in June 2001. NASA is updating its analysis models of the booster/X-43A flight and says it is "looking at some trajectory changes". These include reducing the fuel load on the Pegasus which "will allow us to launch at a higher altitude [from the B-52 mothership] and will reduce the dynamic profile", says the agency.

NASA is looking at modifying the separation technique of the X-43A from the booster by adding two pistons to eject the vehicle from the Pegasus. The X-43A scramjet (supersonic combustion ramjet) will then light-up for around 7s, thrusting the vehicle to Mach 7 and covering around 500km (270nm) of the Pacific test range. Pending the successful firing of the second X-43A, NASA will attempt a M10 flight with a third hypersonic vehicle in 2004.

The projected target date for the second attempt is at least four months later than NASA's earlier estimate and reflects the extra time required to evaluate the revised launch profile and change the separation mechanism.

Source: Flight International