When His SR-71 Blackbird Disintegrated, This Pilot Free Fell from Space

That was a fascinating read, thank you.

What is correlation?

For low speed flows like in F1 the viscous effects are much larger and this can make flow prediction more difficult. It’s actually pretty easy to predict the shockwave pattern from 1D theory without the need for CFD [0]. The boundary layers are much thinner and you can assume inviscid flow at first. At hypersonic speeds the interactions get more complex however and you’re dealing with a lot more materials science challenges so CFD is important in predicting thermal loads and shock boundary layer interactions.

[0] https://en.m.wikipedia.org/wiki/Oblique_shock

The CFD simulation in F1 isn't really a track simulation. Normally a straight or curved domain (for car in yaw) is used. Computational limits in the rules mean simulating dirty air, like when following a car, is incredibly inefficient.

The test itself wasn't fatally flawed, it snowballed when they had an unrelated engine malfunction.

Several minutes into cruise, the right engine inlet’s automatic control system malfunctioned, requiring a switch to manual control... Without proper scheduling, disturbances inside the inlet could result in the shock wave being expelled forward–a phenomenon known as an “inlet unstart.” That causes an instantaneous loss of engine thrust -- TFA

Weight

Only the pilot and copilot had ejection seats, the rest of the crew couldn't also have ejection seats (I'm not sure if it was specifically weight, volume, or orientation/configuration that was the limiting factor. I think maybe a combination of all three.) STS-1 through STS-4 (all using Columbia) only had a pilot and copilot, no other crew. For STS-5 and STS-9 when there was more crew, they flew with the ejection seats disabled. After STS-9 the seats were removed.

I don't have a source saying it specifically, but I think they weren't keen on operating a shuttle where two of seven crew could survive but the other five had no chance. It must have also saved weight and space too.

They were kinda useless, operationally-speaking. Half the crew members were on the lower deck and surrounded by significant hull structure, and so couldn't eject. The first two shuttles were only designed around a crew of 2 where this design made more sense.

Irrespective of that, the ejection seats only work for a very limited period of the shuttle's operating envelope. IIRC it's something like only the first 2 minutes of flight where the ejection seats could be used. And in most cases where you'd be able to eject, the solid rocket boosters were still firing and it was theorized that as the shuttle passed a pilot who had just ejected, the exhaust gases would ruin the parachute and/or kill an ejecting pilot anyways.

By the time the SRBs burnt out, the shuttle was too high/fast to eject.

I read that at least one shuttle commander thought the ejector seats would've been useless anyway b/c if you used them while the solid rocket boosters were still running you'd get burned up & lose your parachutes from the SRB exhaust - and your altitude & velocity would be too high to eject by the time you'd be safe from the SRBs

Think of the situation that puts the commander and pilot in- they're the ones flying the shuttle; no one else can eject.

If they eject, they are essentially abandoning the rest of the crew to die. It's the antithesis of the captain going down with his ship.

Initial unpowered glide tests were the only flights where ejection was even likely survivable, and this was the reason the seats were ever installed in the first place. (Only on the first two orbiters.) Any other use was an extreme long shot.

Of course all the abort modes ended up being fairly convoluted and unsurvivable to some extent, except abort to orbit.

The "contingency" aborts were especially absurd, which depended on burning off most of the remaining fuel (which would take longer, given it would likely be used in the event of an engine failure), then orienting the shuttle into a position where the crew could attempt a midair bail out. Think about that.

RTLS was a close second, for single SSME loss in the first 4 minutes. It was a 25 minute (!) abort process that involved building up enough speed and altitude so that the shuttle could be flipped around and "put in reverse" to return to the launch site. This involved a certain amount of time at near zero horizontal velocity, so the altitude was needed to permit some time of "free fall" while reversing direction. It also put the orbiter well outside of it's survivable stress envelope, and subjected the crew to extreme g-forces. It was highly questionable that even a perfectly functioning shuttle could have executed the abort, let alone a malfunctioning one.

>Astronaut Mike Mullane referred to the RTLS abort as an "unnatural act of physics"

>John Young:"RTLS requires continuous miracles interspersed with acts of God to be successful"

These were abort modes that were considered survivable. There were another set of scenarios that were considered not survivable: LOCV for Loss of Crew and Vehicle.

It was this level of absurdity that led to the NASA culture of basically ignoring some cherry-picked risks, ultimately leading to Challenger and Columbia.

https://spaceflight.nasa.gov/shuttle/reference/shutref/sts/a...

http://www.nasa.gov/centers/johnson/pdf/383441main_contingen...

https://en.m.wikipedia.org/wiki/Space_Shuttle_abort_modes

Especially on a brand new aircraft during the maiden flight.