HUNTSVILLE, Alabama - The thinner and lighter the rocket skin, the less power needed to lift the rocket into orbit. Or, the thinner and lighter the skin, the more cargo the rocket can carry.
This Rocketry 101 lesson is behind a test at Huntsville's Marshall Space Flight Center this week on a device some NASA wags are calling "the world's biggest can cruncher." During Wednesday's test, a 20-foot-tall, 27-foot-wide cylinder simulating a rocket's shell and made of aluminum and lithium will be squeezed between two platforms with a million pounds of force until it buckles.
If that sounds as much fun to you as it does to NASA engineers and news reporters, you can watch on NASA-TV (http://www.nasa.gov/ntv) or on Ustream (http://www.ustream.tv/channel/nasa-msfc) Wednesday at 9:30 a.m.
For the engineers, high-speed cameras will record every micro-change in the cylinder. Then, they will match the results against computer-generated predictions.
"We think we understand the physics (now), and then we don't have to pile on a lot of margin," said Mark Hilburger, principal investigator and senior research engineer at NASA's Langley Research in Hampton, Va. "Margin" is when rocket engineers say something like, "Let's just double that thickness to be safe." Engineers hate to say things like that. Margin is imprecise, and margin costs money.
A lot has changed - think composites and computer models for starters - since NASA wrote a book on rocket design in 1968 that was full of margins. But Hilburger said rockets worldwide are still built from that 1968 manual.
NASA VIPs will be there Wednesday hoping to see a step toward rewriting the manual, and so will representatives from the major commercial space manufacturers competing to build the next-generation space shuttle. It'll be a crammed control room in Marshall's Engineering Test Laboratory.
Only at NASA would a "test lab" include a high bay 169 feet tall. The lab was built in the 1960s for Wernher von Braun and the Saturn rocket team and has tested parts of the International Space Station and space shuttle.
Engineers walking around the building today point out the "spare no expense" moon race hardware, including four telephone-pole-thick screws that raise and lower the 3-ton top of the test platform. "This is the only facility where you could stack something this high all the way around in a controlled environment," says Marshall lead test engineer Mike Roberts. "There is no other place at NASA - maybe nowhere - this can be done."
Wednesday's big day begins with pre-test briefings much like a rocket launch countdown to make sure every system is ready. The test is scheduled to begin at 9:30 a.m. CDT.
What does a test like this cost? Not as much as you might think. The cylinder being crunched is made up of leftover external fuel tank segments. It was welded together at another Marshall facility.
And this won't be a sumo wrestler crunch, either. "It's not like a Coke can going flat," Roberts said. "We're going to catch it at buckling." If they do it just right, Roberts said, the cylinder should just pop back into shape when the pressure's off.