Whilst reading A Technical History of the External Tank I ran across this comment:

Although the problem has not recurred, John Young, in his famous top ten Shuttle risk letter published after the Challenger accident, listed stiction as a significant risk.

What were the top ten risks listed by Young1? Preferably, with the full text of the "letter".

I remember him being famous for issuing memos about Shuttle safety, but I don't remember this one.

1Ok, the other nine.

An acceptable answer to this question must include all three of the following elements:

  • Be a list of shuttle risks
  • Be written, or at least sent out, by John Young
  • Include ET pressure transducer stiction as one of the risks
  • 4
    $\begingroup$ Haven't found the document, but footnote 63 here gives a possible title: Memorandum from CB/Chief, Astronaut Office to CA/Director, Flight Crew Operations, "One Part of the 51-L Accident-Space Shuttle Program Flight Safety". $\endgroup$ Commented May 24, 2019 at 21:01
  • 1
    $\begingroup$ I found several contemporary news articles about it - Truly released the memo in March 1986 - but the 'top ten list' seems to have been an attachment that is mentioned, but not shown in the articles. Here's one such that mentions a few issues: apnews.com/ccb0ae4d23f23b581d9b601fd833fcf8 $\endgroup$ Commented May 24, 2019 at 23:17
  • 6
    $\begingroup$ I have found the original memo you're talking about. No "top ten" list. See history.nasa.gov/SP-4407/vol4/cover.pdf page 378 has the memo. Also, stiction is not mentioned in the memo. There is a list of safety questions that Young raised that are interesting, but not set out as a list I'm afraid. It seems that another document is the one that contains the list... $\endgroup$ Commented May 25, 2019 at 13:27
  • 2
    $\begingroup$ Indeed. To clarify, I was talking about the memo mentioned in the comments, so yes, it looks like it isn't the one you were looking for $\endgroup$ Commented May 25, 2019 at 13:37
  • 5
    $\begingroup$ @user16338 apparently it was published in the now defunct newspaper the Houston Post. The downtown Houston library has archives of the paper on microfiche, once they open back up (currently closed for pandemic) I plan to go look for it. $\endgroup$ Commented May 12, 2021 at 18:39

1 Answer 1


I managed to find a news article that addresses some of this.

Booster rocket seal conditions

... Challenger flight that exploded and killed its crew of seven, Young said, ″There is only one driving reason that such a potentially dangerous system would ever be allowed to fly - launch schedule pressure.″

Space shuttle launch rate

we should not allow any increase in the inherent risk of operating the space shuttle just to increase the launch rate, or reduce operating costs, or fly unsafe payloads.

Flapper valves

October-December 1984 - Flapper valves on fittings between the shuttle and its huge liquid fuel tank were ″extremely sensitive.″ If any of the four flapper valves close, the memo said, ″the result is loss of vehicle and crew.″

Adverse weather and tile damage

August 1985 - The shuttle Discovery was launched at a time when there was moderate turbulence and rain on an emergency landing runway at the Kennedy Space Center. ″If the tile damage assessment was realistic, winds in storms plus tile damage drag might lose the vehicle and crew in an abort″ .

Lock up of maneuvering jets

October 1985 - A regulator on one of Challenger’s maneuvering jets locked up. ″The cause of the lockup was not known,″ according to the memo. NASA decided to fly anyway, relying on another backup regulator, which also ″indicated failed″ as it reached orbit.

Failure of a liquid oxygen prevalve

January 1986 - A delay in launching Columbia revealed a critical failure of a liquid oxygen prevalve.

  • $\begingroup$ I'm not sure if this is the one or another one. $\endgroup$
    – Fred
    Commented Oct 4, 2021 at 16:15
  • $\begingroup$ I'm glad you posted this because it reminded me to check on the status of the 2 downtown Houston libraries that have Houston Post archives. It seems that they are open to the public now, so perhaps I can get down there later this week. $\endgroup$ Commented Oct 4, 2021 at 16:30

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