# Features seen on the Space Shuttle's solid booster; what does "LOADED" mean exactly?

The question Please explain the time reference shown in Shuttle launch engineering video links to the very cool video Ascent - Commemorating Shuttle. After about 22:25 in the video there is footage from "Camera 33" showing the external fuel tank and one solid booster.

As the booster passes by on the right side of the image, I noticed the following sequence of things pass by, superimposed on the otherwise smooth white matte surface of the booster.

Question: What are these, and what exactly does "LOADED" mean?

BLACK band
BLACK band
WHITE band
(small writing)
BLACK band
WHITE band
BLACK band
(small writing)
(Bottom, nozzle)


• youtu.be/maSP1YfNZLc?t=246 shows that LOADED is still used by ATK for SLS. I can't verify, but seems it just indicates that the segment is loaded with propellant (useful during transport from Utah ?)
– amI
Sep 7, 2019 at 8:09
• @Makyen thank you for the edit, but by providing the screen shots with the time codes visible my intention is to provide all of the information to the reader without them having to proceed to YouTube. The modification you made sends them to YouTube without warning (by clicking on the image to see it in full size, the would be unwittingly sent off-site). It's a cool trick, but people viewing in mobile with low bandwidth connections or expensive data plans will be unhappy about it. I've seen several complaints from people like that so I try to be sensitive to other readers.
– uhoh
Sep 8, 2019 at 2:30
• It may mean it has wads of dosh
– user20636
Sep 8, 2019 at 8:32

Image source

The booster has two kinds of joints between its segments, field joints and factory joints. The booster parts shipped to KSC were made up of two segments joined by factory joints. At KSC, these parts were put together using the field joints. There are three field joints and seven factory joints in a Shuttle SRB.

Image Source

Both kinds of joints are pinned joints. As shown in this picture, there are a large number of holes around the joint. Once the segments are aligned, pins are inserted into the holes. Then a retainer band goes around the outside of the joint to hold the pins in.

Here is a cutaway drawing of the factory joint.

Image Source

That's it for the factory joints. These are the black bands you see.

The field joints are assembled basically the same way, but after the retainer band goes around them, electrical joint heaters are attached, to keep the joint O-rings nice and warm and help prevent another Challenger-like failure. (Mechanical features of the field joints are different now from what they were in Challenger days as well.) The white bands are field joints and are bigger because they incorporate insulation and the joint heaters.

Here's a cutaway drawing of the field joints showing the heaters, insulation, retaining band and pins.

Image source

LOADED just means the casing has propellant in it. I haven't found a reference for that one either. But, here is a segment with the counterexample: INERT

Rotated and cropped from this KSC flickr image

LOADED is a segment with real propellant in it, INERT does not have real propellant in it.

Bonus SRB labeling fact: the SRB segment railcars are labeled with DO NOT HUMP.

Image source

That means they should not be subjected to "humping", a process where "rail cars are pushed up a hill (hump), uncoupled, and then rolled downhill into remotely controlled sorting tracks." (source: Union Pacific glossary)

• I expect there has been some creative graffiti on those railcars Sep 8, 2019 at 4:21
• I would suspect security being exceptionally tight around those cars. I would be deeply concerned about someone's ability to get close enough to one of those to spray paint it. That said, I've heard stories about those cars arriving at KSC with bullet holes in them... Sep 10, 2019 at 13:51
• @Tristan I'm dating myself a bit, but when I was young my father told me that when he was young either he and his friends or some other local kids threw rocks at the primary mirror of the 200 inch Hale telescope on its way from Corning NY to California. Things have changed over the last century in the US, so perhaps those are roughly historically equivalent. :-)
– uhoh
Sep 12, 2020 at 15:22

'Loaded' means it's loaded with propellant (as opposed to something like 'inert' or no marking at all, for casings that have not been loaded). It's used to make it easy to distinguish which casing segments have been loaded with propellant and which ones haven't. Loaded segments require different handling procedures than non-loaded segments.

In the military, color codes are used for the same purpose: to make it easy to distinguish between live missiles (with propellant and explosives on board) and training rounds (without explosives, used to train people in missile handling).

The black bands are a rubber coating over the joints between sections. The white bands are another joint cover, I think. The black ones are applied in the factory, which means the white ones are applied on the launch site when the 4 booster segments are joined. Each segments consists of smaller barrel sections that are joined at the factory before the propellant is cast into the section.

The much wider black band at the top was painted on the left-side booster only to make it easier to distinguish between them during descent and splashdown.

• a quick search didn't turn up anything, but I'll have another look later. Sep 7, 2019 at 8:02
• see this comment. I think a screen shot will do it! i.stack.imgur.com/VmzWb.jpg
– uhoh
Sep 7, 2019 at 8:14