A University of Queensland lab has supersonic success.
- By Luba Vangelova
- Air & Space magazine, November 2002
(Page 3 of 7)
The most advanced wind tunnels can accelerate a scramjet model to the required speeds and temperatures for only a few milliseconds. But actual flight tests are expensive, logistically challenging, and considerably vulnerable to things going wrong.
Just ask NASA. In June 2001, the agency hoped to record the first scramjet-powered hypersonic flight in a much-ballyhooed trial (the first of three in its Hyper-X program) off the California coast. But the rocket booster malfunctioned and, before the scramjet could be released to allow the real experiment to begin, propelled itself and its payload straight into the Pacific Ocean.
Because different scramjet teams have focused on different pieces of the research puzzle and pursued slightly different near-term goals, the question of who can rightfully claim some nominal “first” usually hinges on semantics and nuances; “It’s a bit fuzzy,” Paull says. What is beyond dispute is that until July 30 no one had demonstrated purely supersonic combustion in a scramjet hurtling unaided through the atmosphere.
The scramjet rode as the payload on a Terrier-Orion sounding rocket, which flew into space in a parabolic arc. The scramjet separated from the booster on the upward trajectory, rotated at its apogee toward Earth, and eventually operated for five seconds (at a speed of almost Mach 8) before it hit the ground. Attached instruments measured various parameters and transmitted a stream of data that researchers can now use to calibrate their design, analysis, and test tools to real flight conditions.
The promise of such data prompted researchers on the other side of the world to pay close attention to Paull’s HyShot program—so much so that NASA even became one of its sponsors. “We’re very hungry for flight data,” says Lawrence Huebner, manager of the Hyper-X scramjet propulsion program at NASA’s Langley Research Center in Virginia.
So what crucial decisions did Paull and company make to eventually achieve what Paull himself called their “beautiful” second launch? To start, Paull hired Hans Alesi, a German-Australian aerospace engineer who had read about HyShot and called to offer his services. Together the two men scrutinized potential engine designs, “trying to figure out how they could go wrong,” Paull recalls. “It’s like going out on a first date. There are a lot of ‘what ifs.’ ” They needed something that could withstand high temperatures, conduct heat well and did not bust their budget. They settled on an alloy of silver and copper, then commissioned university technicians to build it. The final result: a scramjet about half the size necessary to generate enough thrust to propel a craft, but large enough for their experiment.
Next they had to design and build the scramjet’s instrumentation module, which would control the flight and collect and transmit data. Several unexpected and time-consuming problems surfaced. Developing and testing a sophisticated attitude control device took a year and proved “a bigger challenge than the scramjet,” Alesi says in a lilting German accent. Paull and Alesi also had to design some of their payload test tools, such as a three-axis gimbal to simulate how the payload might rotate at the height of its trajectory.
The hitch-a-ride-on-a-sounding-rocket strategy was cheap, but was it cheap enough? As the HyShot timetable doubled and then tripled, Paull began to wonder if the team would run out of funds.