Update: My series of questions honoring the 50th anniversary of Apollo 13 is now complete. An index of the questions in the series are as follows:

See also for more questions about the mission. I hope you have enjoyed the series and have found the discussion useful.

Gene Kranz celebrates success

Original meta question: We are approaching the 50th anniversary of the Apollo 13 mission, also known as "NASA's finest hour". I have a series of questions related to Apollo 13, and was planning on asking 1 or 2 per day during the anniversary dates (April 11 to 17).

Are there any objections to my doing this?

  • 1
    $\begingroup$ as long as they're good questions $\endgroup$
    – user20636
    Mar 21, 2020 at 17:20

3 Answers 3


Sounds like a perfectly fine thing to do, just make sure each question is mostly stand-alone.

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    $\begingroup$ The questions I have right now are stand-alone. However, as I often do, I was going to add links to older questions. $\endgroup$
    – DrSheldon
    Mar 19, 2020 at 23:18
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    $\begingroup$ Unless the previous question is closely related, I wouldn't. $\endgroup$
    – PearsonArtPhoto Mod
    Mar 20, 2020 at 14:25

Okay, I am going to go ahead with the project. The first post will be Saturday, the 50th anniversary of the launch. The plan is to post two questions per day, for each of the seven mission days. The expected posting time is noon in Houston (17:00 UTC). I have a considerable list of questions, and have picked the ones I think people will find most interesting and fun.

For the majority of the questions, I already know the answer. My personal belief is that others should get the opportunity to write the answers, and I don't like answering my own questions unless absolutely necessary.

I've had a few questions in the past which have an interesting premise, but a difficult-to-find answer, and it's clear that I already know the answer. People complain "why don't you just post the answer", and once I do that, the question is then well-received. There are two questions like this, so I'm just going to immediately post those two answers myself.

However, there are a small number of questions that I don't personally know the answer, but I'm sure one of the regulars here can answer it.

There was one vote, in favor of posting those questions in advance. So here are the questions that I don't already have the answer:

  1. Why was 65 volts used for ground support equipment? (the O2 tank heater switch was not rated for this voltage)
  2. Had Lovell's entire crew been grounded, who would have flown Apollo 13? (I believe the answer is in Deke Slayton's autobiography, but I don't own a copy.)

  3. Without the accident, would Apollo 13 still have been the farthest manned mission?

  4. What trajectory would Apollo 13 have taken if the descent engine also failed? (what's shown in the movie doesn't count)
  5. How much delta-V would an Apollo 13 direct abort have taken? (if immediately done after the explosion)
  6. Did any part of the Apollo 13 LiOH adapter return to Earth?

Orbital mechanics (#3, 4, 5) is particularly an area where I need help.

If you're able to help answering one of these questions, let me know which number(s). I have a slight surplus of questions, so knowing which ones can be answered helps. Thanks.

  • $\begingroup$ I would prefer to know which ones need answers. Answering ones where the answer is known is a waste of my time IMHO. $\endgroup$ Apr 7, 2020 at 1:33
  • $\begingroup$ @OrganicMarble: There are some people who feel the same way you do, and there are others who get upset if I always answer my own questions. I'm doing my best to accommodate both groups. $\endgroup$
    – DrSheldon
    Apr 7, 2020 at 1:46
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    $\begingroup$ I get it, just voicing an opinion as you asked. $\endgroup$ Apr 7, 2020 at 1:52

Can you post them around 6-8am Pacific? ;)


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