[AR] Re: Valley Tech throttleable restartable solids (!)
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Fri, 27 Mar 2020 23:16:44 -0400 (EDT)
On Fri, 27 Mar 2020, roxanna Mason wrote:
Those "little" Titan SRB strap-ons generate the same thrust as an
F-1/F-1b,only. 10ft vs 33ft.
Actually about the same size -- a single F-1 nozzle is a bit over 12ft
across, and produces about 25% more thrust than the 10ft Titan SRB
(1.5Mlbf vs. about 1.2, if I recall correctly).
I once saw a discussion of general issues for Saturn V strap-ons: "the
most cost-effective use of solids is to get more liquid fuel off the
ground". It's easy for tank stretches in the S-IC stage to outrun engine
improvements, resulting in a takeoff T/W that's too low. The problem is
short-term -- it doesn't take that long to burn off a substantial mass of
fuel, plus T/W is less critical once you're well clear of the ground with
substantial upward velocity -- so off-the-shelf hardware that can briefly
supply significant extra takeoff thrust is appealing.
And of course it was the same story for Thor/Delta. The first-stage tanks
got stretched repeatedly, to the point where (as I recall) the core T/W
ended up being less than 1 at takeoff. Even little strap-ons helped.
Henry
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