Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!cornell!uw-beaver!fluke!ssc-vax!eder From: eder@ssc-vax.UUCP (Dani Eder) Newsgroups: sci.space.shuttle Subject: Re: Heavy Lift Capacity Boosters Summary: solid rocket motor design Message-ID: <2247@ssc-vax.UUCP> Date: 24 Sep 88 17:53:26 GMT References: <677@eplrx7.UUCP> <2240@ssc-vax.UUCP> <1402@viper.Lynx.MN.Org> Organization: Boeing Aerospace Corp., Seattle WA Lines: 31 In article dave@viper.Lynx.MN.Org (David Messer) writes: > > How can you vary the number of segments in the SRBs? Wouldn't > that change the combustion-chamber pressure rather > drasticaly? > -- Yes, if that were the only variable you could play with. In tailoring SRBs, you can also change the throat area in the nozzle, which controls how fast combustion gases leave the motor, the shape of the grain (the chunk of solid propellant is called the grain, not the individual propellant grains) which affect how much surface area is exposed to burn, and the amount of burn-rate accelerators (iron oxide in the case of the Shuttle SRBs) mixed into the fuel. With all these parameters to play with, you can pretty much get what you want. For example, the Space Shuttle SRBs have a grain configuration that lowers the thrust during the time of peak aerodynamic pressure on the shuttle stack. Back in 1982 I worked on a study for Boeing for NASA on using all-SRB derived boosters. Thiokol was a subcontractor, and they supplied us with SRB versions ranging from 1 to 5 segments, compared to the 4 segments in the standard motor. -- Dani Eder / Boeing / Space Station Program / uw-beaver!ssc-vax!eder (205)464-4150(w) (205)461-7801(h) 1075 Dockside Drive #905 Huntsville, AL 35824 34 40 N latitude 86 40 W longitude +100m altitude, Earth