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Asymmetry of the Atlas V
Watching the NH launch reminded me of a something that's been bothering
me for a while: why is the arrangement of SRBs on the Atlas V asymmetric? How is the asymmetry of the SRB thrust compensated for? By gimballing the RD-180s? By offsetting the RD-180s? In the former case, isn't this inefficient? In the latter case, how does a 40x or 50x model manage to fly straight? |
#2
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Asymmetry of the Atlas V
wrote:
Watching the NH launch reminded me of a something that's been bothering me for a while: why is the arrangement of SRBs on the Atlas V asymmetric? The arrangement is assymetric because there are two external fittings on the Atlas V common booster core, an avionics pod and an LO2 feedline. These are at about the 10:30 and 1:30 positions. Two of the solids are between these fittings at about the 11:30 and 12:30 positions. The other 3 are on the opposite side at the 5, 6, and 7 o'clock positions. How is the asymmetry of the SRB thrust compensated for? By gimballing the RD-180s? Presumably. ...isn't this inefficient? Not really. The shuttle does exactly this. Another possibility is canting the solid booster nozzles differently to compensate for the assymetry. Jim Davis |
#3
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Asymmetry of the Atlas V
" wrote in
oups.com: Watching the NH launch reminded me of a something that's been bothering me for a while: why is the arrangement of SRBs on the Atlas V asymmetric? How is the asymmetry of the SRB thrust compensated for? By gimballing the RD-180s? By offsetting the RD-180s? In the former case, isn't this inefficient? In the latter case, how does a 40x or 50x model manage to fly straight? The asymmetry IS interesting, but apparently the offset isn't severe and the RD-180 has excellent control authority. The Atlas V comes with any number of solids from 0 to 5, but you'll note that the offset is never more than one motor unit. Possibly the solids' nozzles could also be individually adjusted, although they are non-steerable. --Damon |
#4
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Asymmetry of the Atlas V
Am 20 Jan 2006 00:57:43 -0800 schrieb
": Watching the NH launch reminded me of a something that's been bothering me for a while: why is the arrangement of SRBs on the Atlas V asymmetric? How is the asymmetry of the SRB thrust compensated for? By gimballing the RD-180s? By offsetting the RD-180s? In the former case, isn't this inefficient? In the latter case, how does a 40x or 50x model manage to fly straight? The booster nozzles are simply canted a bit outwards, so that their thrust vectors go through the launcher's center of gravity. The tradeoff os a slight decrease in effective thrust compared to a thrust vector in movement direction, but it is the easiest method of using even asymmetrical arrangements. Another well known example of asymmetrical booster arrangements are the Delta-II 7420/7425 boosters, that use the very same concept. cu, ZiLi aka HKZL -- Gib mir die Zahlen die Du hast, und gib mir die Zahlen die Du brauchst - Und ich suche dann die richtigen Tests raus, um aus den einen die anderen Zahlen zu machen. |
#5
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Asymmetry of the Atlas V
wrote:
Watching the NH launch reminded me of a something that's been bothering me for a while: why is the arrangement of SRBs on the Atlas V asymmetric? The Atlas V booster was originally designed with the idea that it would fly in only Medium and Heavy versions without SRBs. At that point, the booster was configured with an external LOX feedline on one side of the tank and an external avionics bay on the other side, but not in 180 degree symmetry probably due to the physical configuration of ground launcher equiment. When the solids were added to the design (this occurred well before the first launch), there were only certain places where they could be positioned. - Ed Kyle |
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