Titan SRB's had 2 configurations, 1.5MF and 1.7MF which had a half segment
added.
F-1 nominal thrust ~1.5MF and F-1a was ~1.7-1.8MF, just increased Pc, same
TCA.
Physical sizes of the above and the Hercules 10.5' carbon composite case
motors not included in the discussion.
On Fri, Mar 27, 2020 at 8:17 PM Henry Spencer <hspencer@xxxxxxxxxxxxx>
wrote:
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