Request: 156inch SRM

[JacobB094]

A large SRM proposed for some Titan, Saturn and early Space Shuttle configurations. A single segment motor of this diameter was actually tested, this document goes into some detail:
https://ntrs.nasa.gov/api/citations/19730021088/downloads/19730021088.pdf
In actual vehicles, 4 or 5 segments would likely have been utilized. Note, this is not the SSRM, but its predecessor, it's noticeably fatter and would work out to 2.5m diameter in KSP.

It would probably need a specialized decoupler, but perhaps it could use some separation hardware from Titan. Notably, this decoupler (as well as any nosecones and separation hardware) would potentially have great "off-label" utility, as 2.5m is an incredibly common diameter in KSP.

[Pappystein]

Dylan has in his Photon mod the Shuttle SRM... which is in fact the the 156" SRM you are referring to (granted it shrunk to 146" )

Early drawings of the SRM showed a non flared bell shape like the Shuttle gets (which is for 360 degree vectoring. ) It would be nice if we had a side vectored version.

[JacobB094]

I would argue that the reduced diameter and other changes it got along the way make SSRB a different motor. They're also not 2.5m in diameter. Besides the Thiokol one, there were also other 156" SRM proposals (such as from CSD, the guys who made UA series boosters), but I was unable to find out much about them, presumably because Thiokol design was the one that won the bid. Some of those designs were monolithic.

[Pappystein]

Thiokol, Aerojet (Monohull unsegmented) Lockheed Space and Missile AND CSD had 156" designs for MLV/Titan. The 156" test section that was made by Lockheed IIRC was used as a test article by Thiokol, CSD and Aerojet. I cover this in my article on it published a couple years ago.
https://github.com/Pappystein/Space_History/blob/main/PDFs/Large%20Solid%20SRMs%20for%20Saturn%20Rockets.pdf
Click the download button on the top right and choose Raw

The change to a smaller diameter has to do with the logistics of getting segments to the launch site. At 156" diameter you could carry One segment per train car due to mass and physical size (this would be 156x156" segments.) I am not certain but I think the rail to Vandenberg can not handle 156" diameter

However, through the distribution of mass, 2x 156" conjoined segments were a little too heavy for the rail system and made the Train too tall. But shrinking down those segments to 146-148" with a better fuel composition (burn design and composition itself), a conjoined or fused dual segment ~146x240" segment could be shipped on a single train car. Hence why you see dual "Fixed" segments on the Shuttle SRM/RSRM. The SRM/RSRM has 8 segments, Grouped into 4 "Factory fused" segments See here: https://upload.wikimedia.org/wikipedia/commons/d/d8/Space_Shuttle_SRB_diagram.png

This was done to get the Rocket to the Cape/Vandenberg. While I get that what we have is not an Ideal (and I 100% agree), I do think what we have is GOOD ENOUGH until such a time that one of the modelers wants to get to building a new 154-156" SRM for MLV.

Personally, I think the Mono-hull Aerojet is the best concept to build.