R
rfoshaug
Guest
I've tried to do some calculations to determine the liftoff mass of the new shuttle-derived heavy-lift launch vehicle that will get NASA out of low-earth-orbit, by comparing it to Saturn V and the Shuttle.<br /><br />According to wikipedia.org, the mass and thrust of the Saturn V and the STS are as follows (with their thrust-to-weight ratio calculated for those values):<br /><br />Saturn V: Thrust: 7,500,000 lbf<br /> Weight: 6,500,000 lbf<br /> T/W: 1.15<br /><br />Shuttle: Thrust: 7,820,000 lbf<br /> Weight 4,500,000 lbf<br /> T/W: 1.74<br /><br /><br />Of the shuttle's thrust each SSME gives 400,000 lbf, and each SRB gives 3,300,000 lbf thrust.<br /><br />The new heavy-lift launch vehicle will have two 5-segment SRB's and 5 SSME's. That extra segment (and thus extra fuel) on the SRB's could be used for increased thrust over the same 2-minute-6-seconds time, or they could have the same thrust for a longer burn - or something in between.<br /><br />If we assume that they have the same thrust as the current STS SRB's, total thrust of the new launch vehicle would be:<br /><br />(2 x 3,300,000 lbf) + (5 x 400,000 lbf) = 8,600,000 lbf<br /><br />If we instead assume that the 5-segment boosters have 5/4 as much thrust as the 4-segment boosters, each booster gets about 4,125,000 so we get:<br /><br />(2 x 4,125,000 lbf) + (5 x 400,000 lbf) = 10,250,000 lbf<br /><br />So the total thrust of the heavy-lift launch vehicle should be in that range somewhere.<br /><br />It's probable that the thrust-to-weight ratio of the new vehicle will be higher than the Saturn V, but it probably will not jump off the pad quite as rapidly as the shuttle. If we assume the highest of the T/W-ratios with the "version" with the least power in the calculations above and vice versa (ie "worst-case" scenario with the least amount of power combined with a requirement for high T/W compared to "best case" scenario with lots of extra power and a very low T/W), I guess that total launch mass <div class="Discussion_UserSignature"> <p><font color="#ff9900">----------------------------------</font></p><p><font color="#ff9900">My minds have many opinions</font></p> </div>