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Author Topic: Sprint Ferry and Falcon 9 Development  (Read 3994 times)
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Posts: 317

Is it Star Trek?

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« on: March 31, 2006, 05:10:23 PM »

Here is where when its time to program again the talk for programming this part of Mars Direct for Orbiter will be.

Good Luck!

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« Reply #1 on: March 31, 2006, 06:23:47 PM »

Based on an estimated need for 300m/s of delta-v for the main maneuver system, 1000kg of hydrazine will be in the Service Module.  The main thrusters will be four REA 20-4 556N engines, which together generate a thrust of 2224N, consume 1kg fuel per second and a total delta-v of 297m/s (275m/s practical, as other thrusters will be used and these fellas will probably be canted for CG alignment, as they will be offset around the BMM nozzle.  That will expend all the fuel over 16min, 40sec, put to the floor.  Isp is estimated at 2224m/s (226.7sec).  Accelleration initially is 0.278m/s2 and at exhaustion is 0.318m/s2.  I'm going to see what the numbers are with the losses associated with a 7deg precant: 2207m/s Isp (225.0sec); 294.7m/s delta-v; 2207N net thrust, 0.276m/s2 initial accelleration, 0.315m/s2.

I'd like about 150m/s in the Backup Maneuver Motor, so I'll go trolling for a Star series motor that'll do it, and still fit in a 1.2m length.  Nope...Star 30BP is the closest to meeting the requirement, but is 1.51m long.  We can either have the nozzle stick below the separation plane or just make the SM longer, say 1.6m.  The Star 30BP shows a thrust of 27000N, an Isp of 2864m/s (292sec), and a burn time of 54sec, should work quite well as a BMM.  It grosses 543 kg and is 38kg empty, for 505kg of props.  Delta-v is 187m/s on a loaded SM and 214m/s on an unloaded one.  The burnout accellerations are 3.602m/s2 loaded and 4.157m/s2 empty.  Here "loaded" and "empty" refer to how much main propellant (hydrazine) is left.

With the Star 30BP and main propellants, about 1457kg is left in the service module for structures, batteries, the solar panels and debris shield.

The descent module fetches about 45m/s of delta-v with a 100kg supply of hyrdazine and 2224m/s specific impulse thrusters.  The alignments for +X translation really suck because there can't be any penetrations through the base heatshield.  -X is much better but this blasts forward, and might be obstructed with the docking port doors open.  That means of course, no docking without the Service Module.
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