Death by PowerPoint: the slide that killed seven people (2019)

Here's how I would interpret the slide, doing my best to prevent hindsight from biasing my opinion (since we already know what happened, it's tough to do).

Bullet 1: We looked at all the model data

Bullet 2: The model tends to predict deeper penetration than what we see in practice.

Bullet 3: The model penetration is related to particle velocity

Bullet 4: The penetration is related to the particle mass and surface area (they say volume)

Bullet 5: The foam is soft, so it takes a lot of energy to penetrate the hard ceramic tiles

Bullet 6: It is possible for the foam to penetrate the tiles, though, given enough energy

Bullet 7: If the foam does penetrate, it can cause a bad day

Bullet 8: It doesn't take much beyond the penetration energy to cause a bad day

Bullet 9: We haven't run tests that match the conditions of the strike so we don't have good data

Bullet 10: The foam piece is much, much larger than the stuff we tested

Given that, I would summarize it to say "The foam strike is much larger than what we've tested. All we know is this may mean there was significantly more energy involved, and if it's above the penetration threshold it can be bad. But the model seems to be overly conservative regarding penetration"

Now, the difficult decision is in the constraints. The astronauts didn't have the fuel to get to the ISS. They didn't have EVA suits to attempt a repair or evaluate the damage. There was no plan in place for a rescue mission. Atlantis was being prepped in FL, but was not currently ready. The astronauts probably have, at most, 30 days of oxygen.

Option 1: Allow for re-entry. Some had pegged this at about a 30% chance of success, but I have no idea what that is based upon.

Option 2: Scramble Atlantis to try a rescue mission. This is very risky for a number of reasons. Atlantis wasn't ready, meaning it would have to be rushed, increasing the chances that errors occur. Also, this type of mission was never attempted before, where two Shuttles are within spitting distance and astronauts have to migrate from one to the other. In order for the timeline to be feasible, a decision must be made within 1 day, 2 tops. This would then potentially risk two Shuttle crews instead of one, with an inherently risky mission.

I don't know what other options were available. Given when it occurred in launch window and how long it took to understand there was a problem, an abort wasn't possible. Shuttle did not have a launch abort engine like capsules do. Keep in mind, these decisions have to be made under large amounts of uncertainty. The extent of the damage was not fully known. People could scramble to run additional tests to gather data, but by that time the window on Option 2 may have closed. It's easy to arm-chair quarterback this after the fact, but there weren't good, clear options at the moment.

If it hadn’t been one thing it would have been another. The next two missions after STS-51-L were planned to have two shuttles on the pad simultaneously and both of them with thin-skinned liquid fuel upper stages in the cargo bays.

Charles Perron, in the book Normal Accidents warns of the tendency of people to subtract from the safety margin of a successful system in the pursuit of speed, performance, profits, etc.

It does boggle the mind however that with so much documentation for the Shuttle they never thought to specify a minimum launch temperature!

I think blaming the slide/presentation is severely affected by the hindsight bias - of course, knowing the outcomes, we can find loads of issues with the slide. More importantly, it is always easy to declare a "human factor" incident and blame the human for "bad slides". But the very fact that such an important decision (re-entry) was (presumably) made as a result of Boeing engineers presenting to NASA officials/managers is eyebrow raising. The fact that this type of an issue (foam hitting the tiles) was well know in advance and yet not properly addressed indicates a systemic organizational problems. It would be great to study those organizational factors and processes that resulted in both tragedies: how the risk was managed? how NASA "drifted" into failure? I believe focusing on a slide completely misses the point.

Powerpoint doesn't communicate badly. People communicate badly.

Thanks for correcting on the CO2.

>This was the sixth time that exact piece had broken off and hit the vehicle.

That was part of the problem and what is meant by the foam shedding being "in family." They had witnessed it enough (along with foam shedding elsewhere) without consequence that it wasn't really considered a credible risk. Until it happened during a period of the launch where the delta-v made it a different scenario, with an energy that caused unexpected characteristics about the foam.

This is second hand knowledge, but the person I know involved in the testing said they had a really hard time recreating the damage to tiles on the specs they were given after Columbia. By chance, they decided to turn the gun beyond the quoted specs (as I understand it), and all of a sudden the foam acted like a hard chunk of debris. I think it's hard for people to grasp how much is unknown, even after a disaster. Often, it's only in hindsight where it seems obvious.