David:
Weight. Liquid injection is heavier than a steerable nozzle. But moveable
nozzles are much more expensive; when I looked into steering for an amateur
rocket I concluded Liquid Injection was more achievable than pivoting the
nozzle. Both are much more expensive than fins in the exhaust or moveable
canards which are probably the lowest cost; cold gas jets may be the next
lowest in cost if one wants exoatmopheric steering.
Bill
On Sat, Mar 3, 2018 at 12:13 PM David Summers <dvidsum@xxxxxxxxx> wrote:
Anyone have any thoughts on why liquid injection thrust vectoring has
fallen from favor? I had always thought that seemed simple and effective.
On Sat, Mar 3, 2018, 12:43 PM Henry Spencer <hspencer@xxxxxxxxxxxxx>
wrote:
On Sat, 3 Mar 2018, J Farmer wrote:
Was all directional control during a Shuttle launch done via it'sengines
and none via the SRBs?
No, the SRBs had gimbaled nozzles (and quite a bit of other complexity,
including their own gyros). The solid-rocket guys at Langley, who first
proposed the solid boosters, wanted fixed nozzles with the orbiter engines
doing all the control. They got overruled. "The problem is that the
control people overspecify their requirements by a factor of four or
five." -- Guy Thibodaux.
Yes, a large fraction of the shuttle's takeoff thrust came from the SRBs,
but that isn't necessarily prohibitive -- if memory serves, Delta II Heavy
(the late Delta II configuration that used Delta III's bigger strapons)
had a similar percentage of its takeoff thrust in fixed-nozzle solids.
Have there been working launch vehicles with solid motors that didn't
use some sort of aerodynamic control?
Plenty, starting with Minuteman and all the Western submarine-launched
ballistic missiles. If you take a purist view of "launch vehicles" :-),
there's Taurus, all the Minotaur variants I think, Athena, and Japan's
M-V.
Henry
