Jan. 5, 2008 -- While the Space Shuttle might be up for the highest bidder, engineers at NASA are working hard on the next generation manned spacecraft, the Orion. Part of that work involves testing scaled down models in the world's largest wind tunnel in Buffalo, N.Y., which was recently upgraded to achieve air speeds up to Mach 30, or about 30 times the speed of sound.
"We just got it up and running and started its research life," said Michael Holden, vice president of hypersonics at Cubrc. "The original wind tunnel was developed by NASA, but we have built it much bigger and can get much more information with our new tunnel."
It takes a "one-two punch," as Holden puts it, to create wind speeds of 30,000 miles an hour in the 100-foot-plus long, eight-foot wide tunnel.
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First, helium or hydrogen gas is compressed to 3,000 pounds per square inch (psi) and 1,000 degrees Fahrenheit, which breaks a seal. The shock wave created by the influx of hot gas raises the the pressure inside a second chamber to over 20,000 psi, which breaks a second diaphragm, and releases the compressed air into the expansion chamber, where it flows over the model craft in the chamber.
The wind tunnel doesn't operate for long. At its most powerful state, the tunnel "blows wind," as Holden says, for only two milliseconds. It's not much time, but its enough to simulate 60 feet of airflow. Any longer and the facility would literally melt down; those speeds create temperatures hotter than the sun.
The Cubrc facility might not be able to handle those temperatures, but the next generation U.S. space capsule, the Orion, will have to handle extreme temperatures when it reenters the Earth's atmosphere.
The Orion capsule looks similar to the old Apollo capsules used in moon missions (cone-shaped with a rounded base) but it's about 33 percent larger than Apollo.
"It's basically Apollo on steroids," said Holden. That increase in size passes a significant milestone when it comes to air flow however, which requires entirely new testing to ensure its safety.
The original Apollo design used physics to its advantage; its small size ensured that air flowed around the capsule smoothly, keeping vibration and temperature to a (relative) minimum. The larger Orion capsule breaks up the smooth air flows Apollo took advantage of, creating higher temperatures and more chaotic wind flows that are harder to map across the surface.
Besides providing the facility, mapping temperature and speed across a surface is one of Cubrc's greatest abilities, said Randy Lillard of NASA in Houston. Using tiny camel hair brushes and microscopes, engineers at Cubrc can paint more than 1,000 heat sensors over three square inches to map temperature across very small increments to monitor heat differences.
"I can get great data at very precise location and in a very small area," said Lillard.
Three square inches might not seem like a lot, but the temperature and pressure over that tiny area can vary by entire orders of magnitude. On the leading edge of the space shuttle wing, for example, temperatures within half an inch can have huge variations.
On average NASA runs about one Orion test a month there, said Lillard. The rest of the testing time is devoted mainly to other NASA and Department of Defense projects, like experimental scramjet engines and other plane designs.
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