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Prior to the launch, there was media coverage about how the SLS solid rocket boosters were set to expire in December (which could have caused the launch to be delayed).

Was this expiration date based on anything chemical, and if so: Could you smell-check an SRB like I smell-check the milk in my fridge, to see if it's still usable past the expiration date? (Testing a sample for signs of "staleness" would count as a smell-check for this)

On the article for "Solid-propellant rocket" Wikipedia says

Since solid-fuel rockets can remain in storage for an extended period without much propellant degradation...

What does "much" degradation mean, and how is this degradation measured?

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    $\begingroup$ It's not the propellant that expires IIRC. It's things like the O-rings, hydrazine sitting in the TVC system, etc. Certification limits that may or may not be real, just what has been tested. $\endgroup$ Nov 17, 2022 at 15:26
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    $\begingroup$ I was looking for data when I discovered this sentence, "since solid-fuel rockets can remain in storage for an extended period without much propellant degradation and because they almost always launch reliably" and thought... almost? $\endgroup$
    – CGCampbell
    Nov 17, 2022 at 16:55
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    $\begingroup$ @OrganicMarble I saw a comment a few days ago on a similar question which mentioned that the "best before" date runs from the start of the propellant pour, not the end. So there must be a limit on the propellant because the boosters are not immediately stacked, so seals etc only come into play later on. $\endgroup$
    – Moo
    Nov 17, 2022 at 21:29
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    $\begingroup$ @OrganicMarble trying to find it, cant remember it it was here or on Ars... $\endgroup$
    – Moo
    Nov 17, 2022 at 21:40
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    $\begingroup$ Possibly this article, or this one, or this one, or this one might help. There are others. This is not my briar patch or my cup of tea, so I am making this a comment rather than an answer. $\endgroup$ Nov 17, 2022 at 22:29

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The expiration date on the solid rocket booster wasn't actually for the boosters themselves, but assembled product. The clock didn't start with the manufacturing of the booster segments, but when they were combined together near the launch pad.

I can't find a source, but I believe the timer is for the o-rings and connecting hardware. The concern is that the same thing could happen that happened with the Challenger, the seal breaks mid-flight and causes fire to come out the wrong area, leading to the same issues that happened with the Challenger breakup.

If there had been a determination that this timer was expired it would have required disassembling the segments of the solid rockets and rebuilding with fresh connecting hardware. The same segments could have been used with the same fuel.

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    $\begingroup$ "Any kind of sources as to what might actually happen would be of value." $\endgroup$ Nov 19, 2022 at 14:42
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A recent post on NASASpaceflight.com provides backup for my earlier comment

It's not the propellant that expires IIRC. It's things like the O-rings, hydrazine sitting in the TVC system, etc. Certification limits that may or may not be real, just what has been tested.

This article talks about the limit being seal-related.

“Where the stack life comes in is there are some features in the booster that move with time and gravity loads that are temperature dependent [for] how much they move. And we do some rather detailed analysis as to whether, for example, our field joints, where we have some sealing features and thermal barriers in those positions where how they mate together matters to their performance. And over time, their interfaces can change.

This originally led to a one-year stack life, but that didn’t mean the SRBs were only good for one year, just that the initial certification went out one year.

“So as Artemis I was delayed due to various different issues, we were able to go show through some additional data that we had, some additional testing, and some additional analysis that we could extend that well beyond one year,” noted Tobias.

“And the boosters, from a stack life standpoint, were certified to go through the end of the year. And there were additional analyses in work that would have shown that they were good to go into the early part of next year as well.”

(emphasis mine)

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Shuttles Solid rocket boosters use a fuel of slurry paste made of aluminum powder, ammonium perchlorate (oxidizer) and a chemical binder to keep it settled when mixed. The binder has a shelf life and the oxidizer is so powerful it has a propensity to rapidly become caustic in metal containers. Hence fuel is kept in environmentally controlled surroundings to slow its chemical decomposition

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    $\begingroup$ While probably correct would be a much stronger answer with some sources and possibly an edit - for example the last sentence refers to fuel when prior sentences refer to the binder and oxidiser having shelf lives but aluminium powder would seem stable - maybe 'mixed and cast segments?'. $\endgroup$ Nov 19, 2022 at 13:24
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    $\begingroup$ This is the start to an answer, but it doesn't really provide anything. Any kind of sources as to what might actually happen would be of value. $\endgroup$
    – PearsonArtPhoto
    Nov 19, 2022 at 14:27

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