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Link....<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p><b>NASA Insists It Can Fix Flaw in Rocket Design</b><br /><br />Published: February 19, 2008<br /><br />Preliminary calculations by NASA last summer suggested that the rocket it had on the drawing board to replace the space shuttle possessed a design flaw: vibrations in the booster might shake the top of the rocket so violently that any astronauts riding aboard would suffer severe, perhaps fatal, injuries.<br /><br />That sounds alarming, but NASA officials insist it is just a step in the process of designing and engineering — identifying problems and solving them. And they say the vibrations — “thrust oscillations” in the language of rocket scientists — are understood and will be fixed well before astronauts fly.<br /><br />Michael D. Griffin, NASA’s administrator, said the oscillation “is not a significant problem, and to the extent that it needs solutions, we’ve got three or four ways to go after it.”<br /><br />In 2004, NASA announced plans to develop a family of rockets, collectively known as the Constellation program, to replace the three-decade-old shuttles, due to be retired in 2010. The first, Ares I, is to have its first test flight next year.<br /><br />To understand the engineering challenge, here is the key thing to know: Unlike most space-bound rockets that use liquid oxygen and hydrogen for fuel, Ares’ first stage will use solid rocket propellant, borrowing the design of the shuttle’s solid fuel boosters.<br /><br />With a solid fuel rocket, the fuel starts burning at the bottom and combusts toward the top. When the fuel is gone, what is left is a hollow metal tube — one that behaves remarkably like an organ pipe.<br /><br />The rich sounds of an organ result from the blowing of air through the pipes. When the wavelength of the vibrations equals the length o</p></blockquote> <div class="Discussion_UserSignature"> </div>