DMeyer@mips.csc.ti.com (Dane Meyer) (11/01/88)
Ken Scofield posed the following question regarding the net booster
forces on the Soviet Shuttle with respect to it's center of gravity.
Anyone have your physics book handy?
Dane Meyer (Texas Instruments, Dallas)
ARPA/CSnet: dmeyer@csc.ti.com
UUCP: {convex!smu im4u texsun pollux ihnp4!infoswx rice}!ti-csl!dmeyer
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And speaking of life's great mysteries, here's another one: If the
Soviet shuttle has no onboard main engines, how in the world do they get
a net force that is anywhere close to passing through the center of mass?
Our shuttle essentially sits atop a tripod, with the main engine cluster
comprising one leg and the SRB's the other two. This is a very stable
arrangement, and as has been stated, gimboling of the nozzles can
compensate for virtually any imbalance. But on the Soviet shuttle, all
engines are clustered about the main booster. With the shuttle hanging
on the side of the booster like an inert wart, the system center of mass
is *not* on the centerline of the booster -- it's somewhere between the
belly of the shuttle and the centerline. So how can they compensate for
this? I haven't seen any good pictures of it yet, but my guess is they
move the side-pods (the equivalent of the SRB's) off-center and sort of
"tuck" them under the shuttles' wings. This would shift the C.G. more
toward the belly of the shuttle, but also give sort of a "squashed" tripod.
_____
/ \ Energia
/ \
/ \\ c // \
\_/ \_____/ \_/
-----/ \-----
\_/
| shuttle
|
Does anyone have an explanation
Ken Scofield
UUCP: {smu!convex ut-sally!ames im4u!rutgers rice}!hp-pcd!hpcvic!kas
ARPA: kas@hp-pcd.hp.comsw@whuts.UUCP (WARMINK) (11/01/88)
Re: Why doesn't the Energiya/shuttle combination topple over? Aligning the thrust vector(s) with the centre of mass would do the trick. This is achieved by commanding the rocket engines to swivel, which is necessary for dynamic balancing, changes in centre of mass due to fuel use and engine-out performance anyway. -- ------------------------------------------------------------------------------ There are lies, damned lies | Stuart Warmink, NAPC and statistics... | <att!>whuts!sw Whippany NJ USA -----------> My opinions are not necessarily those of my employer <-----------
knudsen@ihlpl.ATT.COM (Knudsen) (11/02/88)
Funny you should mention that. I was looking at my newspaper photo of Buran/Energiya yesterday, which shows the stack horizontal in the VABski, and it sure looks like the strap-ons are mounted a bit closer to the orbiter, much as in your ASCII artwork. At first I thgought there may be a 3rd booster underneath (3 at 120 degree angles, like shark fins), but of course that's exactly the wrong thing to do to correct the imbalance problem you brought up. You were very astute. BTW, the long repost of the Russian rocket designer's description of Energiya states that either two or four boosters can be strapped on. They are not "zeroth stages" since the central rocket is also ignited at liftoff (after proper strap-on ignition is verified). Also he implies that ALL Energiya payloads are to be carried off-axis on the side like the shuttle. How would the four boosters be fitted? Well, looking down on the stack, if the payload sits at 12 oclock, then the boosters might be at 10 and 2 oclock and the other two at 8:30 and 3:30. I guess that for any given center of mass, you can move the boosters around to compensate. Verry clever, these Russkies! -- Mike Knudsen Bell Labs(AT&T) att!ihlpl!knudsen "Lawyers are like nuclear bombs and PClones. Nobody likes them, but the other guy's got one, so I better get one too."