Author Topic: STS-133 ET-137 Intertank (IT) Stringer Cracking Issue  (Read 3307 times)

Online rdale

  • Assistant to the Chief Meteorologist
  • Senior Member
  • *****
  • Posts: 10390
  • Lansing MI
  • Liked: 1415
  • Likes Given: 171
Show of hands for remembering the days when we had to learn what a stringer is? Great pics and analysis.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110023677_2011024985.pdf

Several cracks were detected in stringers located beneath the foam on   
the External Tank (ET) following the launch scrub of Space Transportation System (STS)-133 on November 5, 2010. The stringer material was aluminum-lithium (AL-Li) 2090-T83 fabricated from sheets that were nominally 0.064 inches thick. The mechanical properties of the stringer material were known to vary between different material lots, with the stringers from ET-137 (predominately lots 620853 and 620854) having the highest yield and ultimate stresses. Subsequent testing determined that these same lots also had the lowest fracture toughness properties. The NASA Engineering and Safety Center (NESC) supported the Space Shuttle Program (SSP)-led investigation. The objective of this investigation was to develop a database of test results to provide validation for structural analysis models, independently confirm test results obtained from other investigators, and determine the proximate cause of the anomalous low fracture toughness observed in stringer lots 620853 and 620854. This document contains the outcome of the investigation.

Offline racshot65

  • Senior Member
  • *****
  • Posts: 2577
  • Aaron Kalair
  • Coventry, England
  • Liked: 0
  • Likes Given: 0
Re: STS-133 ET-137 Intertank (IT) Stringer Cracking Issue
« Reply #1 on: 12/16/2011 02:56 pm »
Can't believe this was over a year ago, doesn't seem like that long

Offline Hodapp

Yeah bittersweet.  :D
Having grown up around the astronauts and my dad working as a lab manager at the LRL and working with the apollo 14/15/16/17 rocks, I had always dreamed of seeing a launch, but it never happened until last February!  One of the highlights of my life!!!
STS-133 was a beautiful launch too...just a gorgeous day...got to see the astrovan drive by, see NASA Adm Bolden flying in the helicopter escorting the astrovan, got to see the NASA astronaut flying a T-38 (weather ops) right over my head doing the wing wag just before he got to me!
« Last Edit: 12/16/2011 03:31 pm by Hodapp »
Launches: 133, 134, 135, EFT-1  Space X Falcon Heavy Test  Scrubs: 134
Future: EM-1 & EM-2

Offline DDG40

  • Full Member
  • *
  • Posts: 171
  • Slidell LA.
  • Liked: 30
  • Likes Given: 11
Re: STS-133 ET-137 Intertank (IT) Stringer Cracking Issue
« Reply #3 on: 12/16/2011 03:49 pm »
I was thinking about the stringer repair job this morning. One year ago today I got the best Christmas gift in along time. I got a call from Lockheed Michoud to come back to work. I had been layed off for 2 months.
I updated my KSC certifications and left for Cocoa Beach on Jan 1st.

 We have been told that NASA wanted to throw in the towel on the Shuttle program because of the cracked stringers. Well the rest is history. We met every milestone and date that was presented. A majority of the hourly workforce assigned to this operation had been recalled from layoff.
 The crew came in with skill set needed and met every challenge. I was so proud of my co workers and being part of that team.
I don't know if this ever made it out to the public but we almost drilled a hole in LO2 tank dome. That was so close to being a disaster.

Offline racshot65

  • Senior Member
  • *****
  • Posts: 2577
  • Aaron Kalair
  • Coventry, England
  • Liked: 0
  • Likes Given: 0
Re: STS-133 ET-137 Intertank (IT) Stringer Cracking Issue
« Reply #4 on: 12/16/2011 04:25 pm »

I don't know if this ever made it out to the public but we almost drilled a hole in LO2 tank dome. That was so close to being a disaster.


I don't remember that ever being mentioned even in L2.

If you had drilled into the L02 tank dome were there options to repair it, or would the tank have had to been scrapped ?

Offline DDG40

  • Full Member
  • *
  • Posts: 171
  • Slidell LA.
  • Liked: 30
  • Likes Given: 11
Re: STS-133 ET-137 Intertank (IT) Stringer Cracking Issue
« Reply #5 on: 12/17/2011 12:13 am »

I don't know if this ever made it out to the public but we almost drilled a hole in LO2 tank dome. That was so close to being a disaster.


I don't remember that ever being mentioned even in L2.

If you had drilled into the L02 tank dome were there options to repair it, or would the tank have had to been scrapped ?

More than like it would at the very least we would have to demate from the Intertank. Also Discovery was mated to the ET at that time.
We had to hand drill out andgrind all the stringer fastners securing the stringers.
I stopped them during this process because there were no provison made for drill stops. I got over rode after a 2 hour shut down. At the first hole to be drilled outthe tech said he hit the tank with the drill bit. We were able to get some mold material on to a q tip and get an impression of the damage.
A USA lab group  was then pressed into action to bore scope all holes that we removed fastners from. We got a use as is on the damge.
The guys from USA created a shop aid made from phneolic sheets and foam that could be wedge between the LO2 dome on the internal IT skin panels. This work well.
When we would complete drilling and grinding ops on a stringer we could pull the shop aid out and look for penatration of the phenolic sheet to make sure we had not hit the dome again.

Offline Chris Bergin

Yeah, I don't recall that either....and we've got a ton of presentations on the stringer fun in L2:

http://forum.nasaspaceflight.com/index.php?action=tags&tags=ET
Support NSF via L2 -- Help improve NSF -- Site Rules/Feedback/Updates
**Not a L2 member? Whitelist this forum in your adblocker to support the site and ensure full functionality.**

Offline DDG40

  • Full Member
  • *
  • Posts: 171
  • Slidell LA.
  • Liked: 30
  • Likes Given: 11
Re: STS-133 ET-137 Intertank (IT) Stringer Cracking Issue
« Reply #7 on: 12/17/2011 12:22 am »
Yeah, I don't recall that either....and we've got a ton of presentations on the stringer fun in L2:

http://forum.nasaspaceflight.com/index.php?action=tags&tags=ET
It was something that I would have not mentioned a year ago.
Now that everything is over I don't mind sharing. I was reading your updates back then put not posting. We were scratching our heads as to how you got the information because it was so freaking accurate and real time. We joked that we didn't need to do a tie in with the next shift because every thing we had done on that shift was already posted on NSF.

Offline cneth

  • Full Member
  • **
  • Posts: 259
  • Liked: 2
  • Likes Given: 9
Re: STS-133 ET-137 Intertank (IT) Stringer Cracking Issue
« Reply #8 on: 12/17/2011 12:36 am »
Great story DDG40! 

I also think it's very interesting that the report in the OP basically says "don't make stringers out of that that material".   

Tags:
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
0