PEACE through Superior Firepower
Posted on 11/11/2004 3:43:17 PM PST by BenLurkin
EDWARDS AFB - Already holding the world speed record for an air-breathing engine, NASA's X-43A hypersonic research aircraft will aim to top itself with a flight to nearly 10 times the speed of sound next week. The unmanned aircraft's record-setting March flight to Mach 7 - about 5,000 mph - was the first flight test of a supersonic combustion ramjet - or scramjet - engine integrated with an airframe.
"We set one (world record) in March, and we're going to do it again next week," said Vince Rauch, Hyper-X program manager at NASA's Langley Flight Research Center in Virginia.
The Monday flight marks the culmination of NASA's eight-year, $230 million Hyper-X program, a joint program with the agency's Dryden Flight Research Center at Edwards Air Force Base and the Langley center.
The program is intended to provide actual flight test data of a working scramjet engine, data that will be used to validate computer and ground test models to be used in future engine designs.
In ramjet and scramjet engines, air is scooped into the engine duct then forced through a combustion chamber, where fuel is mixed in and ignited. This produces energy, which is forced out the rear of the engine as thrust.
Scramjets have an advantage over conventional rocket and turbojet engines in that they are more efficient. These air-breathing engines do not have to carry oxidizers on board to mix with fuel, instead using oxygen from the air. For space launch purposes, this means lighter launch vehicles with more payload capacity.
Only 12 feet long and weighing approximately 3,000 pounds, the X-43A is shaped like a flat wedge with fins. The small research aircraft consists largely of the scramjet engine and supporting systems.
To get the X-43A to the hypersonic speeds necessary to test the scramjet engine, the research vehicle is propelled by an Orbital Sciences Corp. Pegasus rocket booster.
The research vehicle is attached to the nose of the rocket booster via an adapter. The entire assembly, known collectively as "the stack," is carried aloft beneath the wing of NASA's workhorse B-52, the same carrier aircraft that launched the X-15 rocket planes.
This will be the last research mission for the venerable bomber, a staple of NASA's flight research programs since it first arrived at Dryden in 1959.
With the success of the March flight behind them, the Hyper-X team faced challenges in preparing a new vehicle and engine for the higher speed flight.
While the Mach 7 flight successfully validated ground test data collected in wind tunnels for the scramjet, no such data is available for Mach 10.
Ground tests are capable only of very short engine runs - along the lines of 10 milliseconds - for the higher speeds, said Laurie Marshall, X-43A chief engineer.
"The challenge is to take limited ground test data and design a vehicle that can perform the test successfully," she said.
The earlier flight validated ground test data, providing information and a basis for further development, she said.
The earlier flight also gave the team confidence in the tricky boost and separation of the research vehicle, said Joel Sitz, Dryden X-43 program manager.
This flight will follow essentially the same flight path, although it will separate about 15,000 feet higher than before.
Heating is a major concern, requiring additional shielding on the most vulnerable areas of the vehicle, the front - or leading - edges of the wings and vertical tails.
Even at the somewhat lower speeds of Mach 7, the X-43A faces extreme temperatures on these areas. The hottest spots on the earlier flight recorded 2,600 degrees Fahrenheit. For comparison, the hottest form of molten lava registers temperatures between 2,000 and 2,140 degrees Fahrenheit.
For the faster Mach 10 flight, researchers predict temperatures of 3,600 degrees Fahrenheit at the hottest points.
Despite the success of the earlier flight and similarities between the two missions, officials stress that this is a research mission, with all the risks inherent in tackling the unknown.
"We wouldn't be doing this if it was a slam dunk," Rauch said.
The jump to Mach 10 is a step in the progression of speeds thought possible for scramjet engines, but not to the extreme end of the envelope, thought to be about Mach 15.
"This is a good, comfortable push," said Lowell Keel, vice president of X-vehicle programs for ATK, the company responsible for the scramjet engine.
Mach 10 is seen as something of a "sweet spot" for operating these kinds of engines, he said.
The engines of each X-43A vehicle are specifically designed for a set target speed. Future engines likely would be designed to move through multiple speeds, Keel said.
From the booster standpoint, this Mach 10 flight is in many ways a more conventional mission for the Pegasus rocket.
The Mach 7 flight required boring out some 3,500 pounds of the solid rocket fuel from the Pegasus, a procedure that never had been done before, said Phillip Joyce, Orbital Sciences program director.
For this higher-speed flight, the conventional full load of fuel - 29,000 pounds - is used.
Some accommodations have been made, such as the greater thermal protection for the leading edges of the booster's wings and fins to protect against the extreme heating at hypersonic speeds.
For a conventional Pegasus mission, the rocket is designed to reach the nearly Mach 10 speeds required of this mission. However, it does so flying a vertical trajectory that takes it to high altitudes, where the thinner air produces less heating from friction.
For the X-43A flight, the booster levels off at a lower altitude in order to launch the research vehicle, exposing itself to heating, Joyce said.
The X-43A flight also requires changes to the Pegasus in terms of shape and aerodynamic qualities, resulting in software changes for control.
"From a controls and vehicle design standpoint, it is definitely flight research," Joyce said. "We've known since day one this is a challenge, so it's gotten a lot of attention."
The Mach 10 flight is scheduled for Monday afternoon, weather permitting. Wet weather at the Edwards AFB take-off point is a concern, as the X-43A is not an all-weather vehicle and may be damaged by rain on the flightline ramp or in take-off.
The B-52 and its payload will take off from Edwards AFB and head for the test area over the Pacific Ocean, the Naval Air Warfare Center Weapons Division Sea Range.
The B-52 will carry the research and launch vehicles to approximately 40,000 feet altitude before dropping the payload. Once free of the mother ship, the rocket booster will light and carry the X-43A to roughly 110,000 feet and approach Mach 10, or 7,000 mph.
Using rocket-powered push rods, the X-43A will separate from the booster and fly on its own for 10 to 12 seconds using the scramjet engine.
Finally, the X-43A will splash down in the Pacific, some 850 miles offshore. Neither it nor the Pegasus rocket booster are intended to be retrieved.
Next week's mission is the third and final flight for an X-43A vehicle.
Sitz confessed to mixed emotions regarding the flight, excitement about what may be accomplished, but also sadness at the end of a program and years of hard work.
"It's like watching a son go off to college," he said.
To mark the end of the program, the Hyper-X team has dedicated this final flight to their families for their support over years of late nights and early mornings.
During the first flight of the X-43A, in June 2001, the Pegasus rocket booster and X-43A went out of control before separating. The vehicles intentionally were destroyed by controllers, with the rocket booster and research vehicle dropping into the ocean without completing the experiment.
The ensuing investigation found problems in the models used in predicting the vehicles' aerodynamic characteristics and the rocket's fin actuator system.
Modifications were made to the fins' system and propellant was removed from the rocket booster to allow a more typical Pegasus launch at 40,000 feet.
This mission marks the end of the Hyper-X program, with no follow-on hypersonic research currently planned within NASA. However, agency officials are working on a proposal for a future "modest but aggressive program" of hypersonic research, Rauch said.
This may result in a scramjet-powered first stage of a two-stage launch system and ultimately a single-stage-to-orbit system, he said.
Interest in scramjet systems exists within the aerospace industry and the Pentagon, which has its own hypersonic research in the FALCON program.
ping a ling
The X-15 made it to 4,520 MPH (Mach 6.7), 50 years ago now. I wonder what technology will be used to keep the fuselage cool or heat-resistant. This was the element that prevented the X-15 from being pushed to go faster. It could have.
Can't see Saving Private Ryan going cross country. It's a conspiracy.
A little off topic, but I think what we're seeing is the lefties in media showing that they are sore losers.
Ping.
Makes you wonder what those boys knew that long ago that our supercomputers aren't cooking up equally impressives leaps in the field. ( SR-71 also)
I can't help but think ceramic hybrids will help in the heat dissipation equation.
bump
Yeah baby!
Alloys and composites have come pretty far too. I'm thinking this technology will probably find its way into cruise missiles first. Think about it, a warhead that can't be easily tracked or shot down by any existing air defense system.
Just from reading the title, it doesn't sound safe to me. Aren't three blades enough?
I'll bet they have already had the Mach 10 aircraft working for a few years.
Peace through superior technology.
Those damn greys.
Thanks miss Wise.
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