eder@ssc-vax.UUCP (Dani Eder) (12/14/84)
> The biggest problem is why the use of ballutes? > Another problem I saw with the sequence is that ASSUMING the Leonov > could control its attitude finely enough to allow the ballutes up front > (like balancing a broom on your fingertip) and ASSUMING they could be > inflated rigidly enough to not collapse and ASSUMING you could find an > ablative or other heat shielding material flexible enough to be folded > up then don't you think that the ballutes should have been just a little > bit singed at the end of the sequence? You've all seen pictures of the > Apollo capsules after they've re-entered and they were only burning off > a few hundred megajoules coming back from the moon. The Leonov had to get > rid of gigajoules to go into Jovian orbit. What was wrong with a good > old fashioned rigid, ablating, jettisoned-at-the-end heatshield as was > used in the book? > Jack Hagerty, Zehntel Inc. The function of an Aerobrake is to change your velocity using less weight than you need using propellant. A secondary function is to provide thermal protection by keeping heat off the rest of the spacecraft. You are correct that having the aerobrake up front is unstable. So you have to actively control your attitude during the maneuver. This is a big challenge in the real aerobrake program. If the aerobrake is 100 ft in diameter, a guess based on the apparent size of the Leonov, and they encounter a 1 psi 'breeze' in the upper Jovian atmosphere, then the total drag is over 1 million lbs, but the ballute pressure need only be on the order of 1 psi internal. The aerobrake material could have been silicon carbide fiber cloth, backed up by .6 cm Nextel felt (3M trademark), and a Kevlar (duPont trademark) cloth pressure bag. The stuff starts out black and ends up black (singe marks are visible close up). I know this because I am looking at a sample we put in a NASA high velocity wind tunnel. It went up to 3000 degrees and is still flexible. If you want more information about real Aerobrakes, why don't we move the discussion to net.space? or you can netmail direct at: Dani Eder/Boeing Aerospace Company, Advanced Space Transportation Organization/uw-beaver!ssc-vax!eder/(206)773-4545