My own view and approach on this timeline is something of a thought I’ve had for a long while, and one that concerns the matter of the thin line in human spaceflight that can divide between what is seen as a ‘successful’ failure or issue and one that results in a loss of crew. Human spaceflight is something that can be seen as routine, but the danger does lie ever present, and so a significant thought lying here has been ‘what if it was an issue or failure that
didn’t become a loss of crew?’
The Space Shuttle flew 135 missions of which 2 (STS-51-L and STS-107) resulted in the loss of crew. Yet at the same time it was a matter of
chance that led to those events, 51-L suffering the highest winds at altitude for any flight in the program and then with 107 for the strike on the RCC as compared to the tiles underneath. Both which could have very nearly not happened. The Space Shuttle is a vehicle that can often be said as a disaster waiting to happen, yet many other close calls to the program historically didn’t see a loss of crew. STS-27R and STS-93 are the most well-known ‘close calls’ for the program, involving the TPS and SSME respectively. There were cases like STS-37 in which you had a set of circumstances which resulted in the Shuttle landing short at Edwards but depending on the conditions if at another site like Kennedy could’ve had more significant issues (please note this was written before the recent Scott Manley video) [1] or STS-76, where an inability to reopen the payload bay doors following the wave-off of the last landing opportunity of the day nearly led to Honolulu being used for an emergency landing as a result. And then from STS-37, STS-76, or STS-93, there was a flight software issue that was only discovered by chance of a draw from the RSLS abort on STS-41-D. The flight software issue was a case where depending on the timing delay, you could result in a case where the hardware output happened before the command computation, resulting in a failure of either SRB or ET separation; further, it was discovered that there was a limit on the BFS engage window following PASS attempting SRB separation because of the PASS requirement to disconnect power to the SRBs [2].
But the Space Shuttle isn’t the only vehicle that is known to have had these close calls involving humans aboard. The Apollo Program’s close call on human spaceflight is known about for Apollo 13, but there were many other near-misses that were present in the program that didn’t happen. Apollo 16 had a significant issue with the SPS backup gimbal motor control electronics following undocking of the LM from the CSM, which could have necessitated an abort prior to landing, and only realized
following the end of the mission that both primary and backup gimbal control cables went through the same cable bundle and one can only imagine if there had been issues after landing [3] [4]. Then aside from Apollo 16, you had a significant issue present on Apollos 8, 10, and 11, in which during reentry, the Service Module did not skip out as expected (to prevent recontact with the Command Module) and which forced modifications in order to avoid the chance of a recontact from the SM with the CM [5].
And at least from how I approached this, is that you simply have the dice roll ‘right’ for a lack of a better term, and then for the cases where you could’ve had the Loss of Crew and Vehicle (LOCV) events… they simply don’t happen. It in effect goes to toe the line, and so for where there could have been a LOCV event, it simply does not happen and the crew comes out fine. It is such a big
thing to consider where that happens and you don’t see the death of spacefarers.
But the case of where an LOCV event doesn’t happen doesn’t mean that the underlying programmatic issues are resolved or removed. They are still present and arguably festering within the program, able to cause lingering issues until they can be dealt with over time as the efforts to deal with them are resolved. In the case of the Space Shuttle, the biggest aspect on this prior to STS-51-L was the matter of the spare parts program which had been underfunded from the start, and became even more of a growing concern from the lack of underfunding because of higher budgetary concerns within the strict OMB caps set by the Reagan Administration (not even counting the matter of federal hiring freezes and the impact that had). And I think by not having a LOCV event happen, it also helps to showcase issues that were of significant concern during the history of the program that are
not as well known about that could’ve had serious circumstances if it had actually happened during flight, with two examples being the PASS Set Split as we discussed earlier in this timeline, or a bird strike on ascent which posed
significant concern during the program [6].
I think overall something to always remember with the matter of human spaceflight is that it is dangerous. There’s no necessary guarantee that it can be routine, and for each and every human spaceflight comes with its own risks, risks that are known and risks that are simply unknown, lurking and waiting to appear.
[1]
https://ntrs.nasa.gov/citations/19920012134 https://web.archive.org/web/2024031...ress.com/2024/03/10/putting-atlantis-at-risk/
[2] The Legacy of Space Shuttle Flight Software:
https://ntrs.nasa.gov/citations/20110014946
[3]
https://web.archive.org/web/20211005012525/http://www.spacefacts.de/mission/english/apollo-16.htm
[4]
https://www.nasa.gov/wp-content/uploads/static/history/alsj/a16/A16_MissionReport.pdf https://historycollection.jsc.nasa....histories/MattinglyTK/MattinglyTK_11-6-01.htm
[K. Mattingly]: I remember thinking at the time that while I was out working on command modules we’d had a problem with the cable that took the electrical signals to and from the gimbals. The gimbal package for each, for pitch and for yaw, each of those packages had a wire bundle that’s probably the size of this antenna and a connector that went into it. So there’s one connector that carried signals to the gimbal, power to it, signals back, and carried it for both the primary and the backup system in one cable. We had had some trouble where the cables that had been fabricated indicated were too short when the gimbal extended its full travel, and we thought we had replaced them all. But what it did was, it would pull the pins out within this little connector.
I said, oh, jeez. That sounds like—but if it happens, it affects both gimbals and—“Oh, what the heck. They said we could go land. That’s what we came for. And I’m not going to tell John. I’m not going to say anything. I’m not going to ask any questions. We’ll just do it.” Of course, it all worked fine. We got our burn off, and they went down and landed, and everybody lived happily ever after.
[4] Apollo 11 Mission Anomaly Report No. 3 Service Module Entry: '
https://web.archive.org/web/2022110...anomaly-report-no.-3-service-module-entry.pdf'
https://www.nasa.gov/history/alsj/a11/a11tcdb.html
14.42 CM/SM Separation
FCOD Rep.
Did you see the service module?
Collins
Yes. It flew by us.
Aldrin
It flew by to the right and a little above us, straight ahead. It was spinning up. It was first visible in window number 4, then later in window number 2, really spinning.
[6] The matter of a bird strike during SimSup training is mentioned in Before Lift-Off: The Making of a Space Shuttle Crew by Henry S.F. Cooper Jr. as one example of the concern it had in the program.