# Why does the Minotaur I wear a yellow jacket that "banana-peels" off as it launches?

Videos available of the recent Minotaur I launch at Wallops for NROL-111 show a yellow jacket on most of the four stage SRB-to-orbit launch vehicle. I read or heard somewhere that wires attached to the ground "banana-peel" the yellow jacket off the rocket as it launches.

I could imagine an insulating jacket on a rocket with cryopropellants, perhaps with clean dry air blown underneath to prevent ice build up, but I can't imagine why this cover would be necessary on an SRB whose heritage is a (presumably) robust ICBM.

Question: Why does the Minotaur I wear a yellow jacket that "banana-peels" off as it launches?

NASA Wallops video "NRO L-111 Launch" cued at about 12 seconds before launch, with a lot of introductory information:

cued at 28:15 There is a lot of cogent discussion in the video before the launch which may be helpful; for some inexplicable reason the NASA Spaceflight narrators suddenly and temporarily loose composure just moments before launch:

Source

The Near Field Infrared Experiment (NFIRE) military satellite in April 2007 with a Minotaur-1 missile

• That last photo is really nice. Jun 16 at 1:04
• @OrganicMarble ya, after the fact I happened to notice the flexible ducting connecting to the bottom of the jacket(s).
– uhoh
Jun 16 at 1:53
• Your second video explains the history/design and reason for the jacket (which is as Organic Marble says below) from approximately 5:50. Jun 17 at 11:09
• @RobGilliam lol! Maybe I should start watching the videos in the questions. Jun 17 at 13:11

The jacket is to control the Propellant Mean Bulk Temperature, a critical factor in solid rocket motor performance.

The silos for the missiles that the launcher was derived from were air-conditioned for this reason.

the Minuteman boosters in the Lower Stack were designed to be launch (sic) from a climate controlled silo with virtually no outside weather effects until launch.

Therefore, continuous temperature control was required.... ...the tight booster temperature constraints could easily be broken. It was decided that whatever system was used it had to be quickly removable - to ensure the availability of the full launch window - and quickly replaced - in case of launch abort. After trading off various options, the approach finally implemented was an inflated, insulated thermal blanket. The blanket can be seen in Figure 16 as the yellow cover over the lower portion of the Launch Vehicle.

(emphasis mine. figure 16 omitted, it was very low res, the picture in the question is far superior)

Demonstration of a New Smallsat Launch Vehicle: The Orbital/Suborbital Program (OSP) Space Launch Vehicle Inaugural Mission Results

• What was the tolerable temperature range for the booster? I didn't see any numbers from skimming the linked paper. (Main reason I ask is because requiring a very specific temperature range seems different from the SLS SRBs, and I'm curious if the latter are more tolerant for some reason) Jun 16 at 1:48
• @DylanSp for a time I worked on shuttle day of launch, and we were constantly dealing with PMBT on the boosters. We got L-12 day and L-3 day predictions from Thiokol on what the PMBT would be at launch to run our sims. A major reason for the shuttle's adaptive throttle in the thrust bucket was because of SRB performance changes due to PMBT. This experience is why I knew what the blanket had to be for although I know nothing about Minotaur. Jun 16 at 1:51
• @DylanSp It sounds like there's a new question or two there!
– uhoh
Jun 16 at 1:52
• @uhoh There's an existing unanswered question, space.stackexchange.com/q/12008/13208. I'll probably post an additional question or two when I can. Jun 16 at 11:17