Path: utzoo!attcan!uunet!husc6!bloom-beacon!tut.cis.ohio-state.edu!mailrus!ames!pasteur!ucbvax!hplabs!hplabsb!dsmith From: dsmith@hplabsb.UUCP (David Smith) Newsgroups: sci.space.shuttle Subject: Re: Orbiter/SRB separation Message-ID: <4741@hplabsb.UUCP> Date: 31 May 88 18:39:42 GMT References: <1869@bigtex.uucp> <4706@hplabsb.UUCP> <1934@ssc-vax.UUCP> <478@uniq.UUCP> Organization: Hewlett-Packard Laboratories Lines: 45 In article <478@uniq.UUCP>, rjnoe@uniq.UUCP (Roger J. Noe) writes: > In article <4712@hplabsb.UUCP>, dsmith@hplabsb.UUCP (David Smith) writes: > > Thank you for the weight of the core (orbiter+ET). Now let's look at > > weights of the SRB's. According to AW&ST, each SRB weighs 1.82 million > > pounds empty, and is loaded with 1.11 million pounds of propellant (note 1). > > Each SRB produces 3.3 million pounds of thrust at liftoff, "throttles" down > > AW&ST said this? My figures (which I admit are somewhat old, but at least > they're ballpark correct) are 181000 lbs. for an inert SRB. The amount of > reactant looks about right; I show a gross liftoff weight of 1.287e6 lbs. > But can that thrust be right? I've got 2.67e6 lbs. sea-level thrust per > SRB. AW&ST said this in their coverage of Challenger's problem with the SRB, Feb. 10, 1986, p.55. If they messed up and slipped a decimal point on the weight, it wasn't in final printing, as they spelled out "million". Actually, I'd prefer to believe AW&ST made a mistake (it wouldn't be the first) than that the SRB is such a stupid design (ahh, well, ...) I'm less willing to believe they made a mistake on the thrust, since they made a point about performance improvements introduced on the 8th shuttle flight that raised liftoff thrust by 200,000 lb. from 3.1e6 to 3.3e6. > Now back to the original question: > > > In article <4706@hplabsb.UUCP>, dsmith@hplabsb.UUCP (David Smith) writes: > > > > True, but since the orbiter is pushing forward on the tank, and not > > > > vice-versa, might it be feasible to throttle down the SSME's to the > > > > point that the loads are manageable? > > The fact that the OV is exerting a net force on the ET is not the problem. > Consider what would happen if you tried separating the orbiter vehicle > from the rest of the system while everything's running. First you have to > shut down the SSME's and disconnect the OV from the ET propellant lines. > In that time, all the thrust is from the SRB's and both the ET and the OV > are dead weight. I had in mind chopping the attachments and fuel lines while the engines were still running: just let them shut down when the propellant in the pipes runs out in a few seconds. I have continued this topic as the devil's advocate, but will probably not say more. David Smith HP Labs