douglas@reed.UUCP (P Douglas Reeder) (08/26/88)
In article <6204@ihlpl.ATT.COM> knudsen@ihlpl.ATT.COM (Knudsen) writes: > >Robert Goddard used this upside-down design in his early >liquid rockets of the '20s; since the nozzle pulls rather than >pushes the ship, you get free stability without servos, gimbals, >and all that other failure-prone stuff. The problem, as Goddard found out, was that a FIXED nozzle at the top is just as bad as one at the bottom. If the connection is flexible then it works like you expect. This is not obvious, but consider carefully: a nozzle at the front a fixed frame rocket pushes in EXACTLY the same direction as one at the back. An unrelated question: Why is it not possible to use the OMS thrusters to make a powered landing on the shuttle, if unpowered landings are so undesirable? Extra fuel would be required, cutting into payload, unfortunately. -- Doug Reeder USENET: ...!tektronix!reed!douglas 10 Cyclopedia Square from BITNET: douglas@reed.UUCP Terminus City from ARPA: tektronix!reed!douglas@berkley Terminus,The Foundation Box 502 Reed College,Portland,OR 97202
henry@utzoo.uucp (Henry Spencer) (08/28/88)
In article <10142@reed.UUCP> douglas@reed.UUCP (P Douglas Reeder) writes: > ... Why is it not possible to use the OMS thrusters >to make a powered landing on the shuttle, if unpowered landings are so >undesirable? Extra fuel would be required... I *think* they simply aren't powerful enough to be useful in a one-gee environment. There may be other reasons; anybody know for sure? -- Intel CPUs are not defective, | Henry Spencer at U of Toronto Zoology they just act that way. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
dsmith@hplabsb.UUCP (David Smith) (08/29/88)
> > ... Why is it not possible to use the OMS thrusters > >to make a powered landing on the shuttle, if unpowered landings are so > >undesirable? Extra fuel would be required... > > I *think* they simply aren't powerful enough to be useful in a one-gee > environment. There may be other reasons; anybody know for sure? Right. I saw the OMS engines listed at combined 6000 pounds thrust. Not enough for a go-around, or (I would guess) even to make significant difference in gliding range. If the orbiter glides in at a 21 degree slope weighing 175,000 pounds, then it is getting 63,000 pounds of thrust from its weight. If we get that same thrust from 6,000 pounds OMS + 57,000 pounds gravity, we have a 19 degree glide slope. -- David Smith HP Labs dsmith@hplabs.hp.com