From the PIC microprocessor list (believe it or not :-) Copied to ARocket for obvious reasons :-) *** The story so far :-) *** Is it "practical" to use rockets to stop a train? *** (each wagon has own rockets) *** (No, I didn't start this thread !) *** *** Now, read on ...... Real world weight penalty would be more like 5 percent, coz: 1g for 5s should be adequate. V= at = 32f/s/s * 5s = 160f/s = 110mph !!!! Ever seen a train stop from 100mph in 5 seconds under brakes alone? :-) (A Porsche will, almost) Isp of around 250 is achievable (HTPB/AP/Al) For 1g accn about 1/(Isp) x total (wagon + load + rocket) mass is burnt per second so Total mass/fuel mass required = 5/250/5 = 1/50th all up mass = 2% Actual motor weighs more than fuel but only about 10% for large solids. So rocket = 2.2% of total mass. If wagon mass = 20% of load mass (Anne ?) then rocket = 2.2% x (120%/100%) = 2.6%ish So 5% should be easily achievable Thrust termination by blowout ports is a standard technique. Multiple rockets per wagon would allow variable thrust levels. But, I agree, it shouldnt be done (obviously). Russell McMahon _____________________________ >From another world - www.easttimor.com What can one train-maniac* do? Help the hungry at no cost to yourself! at http://www.thehungersite.com/ (* - or woman, child or internet enabled intelligent entity :-)) __________________________________________ -----Original Message----- From: Mark Willis To: PICLIST@MITVMA.MIT.EDU Date: Friday, 15 October 1999 21:16 Subject: Re: [OT][PETROCHEMICAL]Train Rockets Yada Yada... >Dave VanHorn wrote: >> >> > Still messy if the solid cored rocket calculated for a full truck >> > fired on an empty one. >> >> @home's sending my email way out of sequence, with dupes. >> >> I said prev, that rockets set for a load of steel would be amusing with a >> load of pigs. >> Pigs Fly! >> >> Basically, there's no way to make that approach go, but it has some amusing >> ways it would not work.. > >I mentioned something about load carrying penalty > >Easy to stop the engine from generating any net thrust forwards or >back; have both forwards & rearwards facing nozzles on each engine. >Blow the "forward" facing one to brake; When this car's empty, blow the >other nozzle cover, so your two thrusts cancel each other. > >Still end up with, what, a 25% cargo weight carrying capacity loss, for >a rocket-assisted braking system? And who'll pay the $100,000 system >refill bill, that driver who ran a crossing gate & then drove away fast >when the conductor pulled the "E-Stop" lanyard and narrowly missed them, >or the people paying to have the train carry their freight? (Isn't >going to be the conductor!) > >Can be done, and shouldn't... > > Mark >