On 3/3/2018 2:58 PM, Henry Spencer wrote:
On Sat, 3 Mar 2018, Henry Vanderbilt wrote:
Small correction: Titan III. One of the changes made for Titan IV, in fact, was development of new improved SRBs... (The first few Titan IVs flew with the old SRBs because the new ones ran late...)
Small correction to the small correction <grin> Indeed, the Titan IV A had the old 7-segment SRM, with liquid injection TVC. The IV B had the new upgraded 3-segment SRMU with gimballed nozzles...
And a small correction to the s.c. to the s.c. :-) Now that you've reminded me of it, I was told at the time (never went digging to confirm) that officially, what *really* made a Titan a IVB was the various changes made to the core -- including bringing it into full conformance with Cape safety rules for the first time (!). That is, it was theoretically possible to have a IVB with the old SRBs, although I don't think that ever actually happened.
(Also -- more background than a correction -- calling the new SRB design "upgraded" was a bit of a euphemism. It was a tip-to-toe redesign, by a different supplier, with different propellant mix, slightly larger size, and longer casing segments made of composites rather than steel, in addition to the gimbaling nozzle. It was also an object lesson in the perils of trying to do a firm-fixed-price development contract with a company long wedded to cost-plus practices: Hercules badly underestimated development costs. In fact, I was told that the explosion of the first prototype was another case of Hubble Mirror Syndrome: "we can't afford the man-hours to figure out exactly what's going on there, so officially the uncertainty does not exist".)
