posted 02-29-2024 01:25 PM               

There have been a number of them, but they seem to only exist in auction listings.

Can anyone tell me what these were used for, and were they actually part of the shuttle's solid rocket boosters (SRBs)? Where would they have been located? I see that they have several different configurations, so presumably that would determine their location.

Also, on several of the pictures I have found, they often have "EFN ##" (where ## is a varying number) hand written on them. What is the significance of this? The only thing I found that would seem to be related to this is a mention of a "electronic flight notes" in a document related to the German space program, however I haven't found any indication that NASA uses such a notation.

posted 03-03-2024 08:29 PM               

I checked the various photos I could find from auction listings for any identifying writing on the pieces. Here is a listing of all the pieces I found so far with identifiable writing. There are many different "styles" of the items, but all have a similar appearance in regards to the green paint, bolt holes, etc.

? indicates unreadable information:

• EFN 21 - Lower Left Left Side s/n 16 HDP 2
  
• EFN 22 - s/n 16 HDP 2
  
• EFN 59 - s/n 16 Lower left HDP 2
  
• EFN 65 - Outbd right upper ??????
  
• EFN 72 - Lower right s/n 16 HDP 2
  
• EFN 75 - Right upper inboard
  
• EFN 80 - HDP 2 Left UPPER Right
  
• EFN 281 - no other markings
  
• Below items have no EFN number written on them
  
• HPD 3 RT RP
  
• HDP 3 Rib #42 s/n 16 (same form factor as the one marked EFN 281)
  
• s/n 16 HDP 3 R
  
• LP RT HDP3
  
• s/n 16 HDP 3 L
  
• HDP 3 LT LP
  
• (Dogtag type metal tag affixed) "10165-0190-001 A 11 UIC SN 20019"
  
• (Shown in example picture - ink stamped not handwritten "10165 0083 001 ( -? 56406 15 JN 3 ) EO 000014" - (handwritten) - HDP ? upper Rib 9
  
• 12 or 21 (in a circle) L.P RS HDP 5 s/n ????
  
• ??? looks like "2cr" 16 POST 4

posted 02-05-2025 10:20 PM               

It appears that I've found where these are used, narrowed down to a fairly high level of confidence.

I came across a website that has posted pictures of a booster that was received by Marshall Space Flight Center in 2012, and eventually assembled and put on display. In a few images of the aft skirt, there are very similar brackets that have the same machining characteristics/features that my bracket has, although I haven't seen an exact match of my bracket. Based on the size of the hold-down post hole diameter, my bracket compares favorably in size to some of those shown.

I did notice a couple of areas in the image where there is a bolt pattern that's the same as my piece, indicating that the bracket is mounted on the underside of the skirt ring. This is likely how mine was used.