Building a parachute is boggling

Regarding the missing pin in Boeing's test last month, I find it quite strange that a physical verification "touch test" wasn't performed by default if it was/is possible.

This is obviously based on extremely limited information, but given that the pin seems to be possible to check physically, and wasn't checked, I don't think I'm speculating too much, as it constrains the issue greatly.

In as mundane activities as rock climbing, adventure courses, and while working at height it's basically a mantra to physically check anything that you can check physically, regardless of if it's been checked in some other way previously. At least in my circles.

Not that physical verification is a panacea, but doesn't it seem borderline arrogant to not include it wherever possible when it comes to something like a parachute system?

I am assuming that the cause for omitting a physical check is that it was decided previous checks - whatever they were - would've been enough.

If failing to check a pin in a parachute system was an actual oversight, I can only assume the project is under very intense pressured to deliver on schedule rather than quality. Not a great look for Boeing if that's the case.

I knew some people who worked near this specialty in aerospace.

From what I remember, it's highly guarded and sensitive due to the rarity of skills and knowledge required.

The problem is highly nonlinear from both an aerodynamics and structural perspective. The fabric changes shape, can only really support a load in tension, and updates of the geometry then feed back into aerodynamics.

I'm trying to imagine how they deal with vibrations/flutter related issues (they may not even be called that on flexible fabric, I haven't checked) where everything has to be solved in the time domain to get Real Answers. We're talking modern day supercomputers and constantly having to reduce time step size to keep solutions faster than the Nyquist frequency on a huge problem set where you have to save a lot of the intermediate results somewhere. Then there are all kinds of other things to worry about that someone more experienced with compressible flow can talk about, and its associated nondimensional simulation parameters and issues...

It's hard enough with incompressible liquids in confined spaces with metals that can only bend and deflect so much. That is an area I'm more familiar with, and know where to look in handbooks to get initial solutions.

But parachutes? Whew. Complex.

SpaceX has been conducting parachute tests for as long as I can remember, they are finicky beasts. Besides, there's only a handful (literally) of manufacturers in the world, perhaps one or two in the US. It is no coincidence that both Boeing and SpaceX are using the same provider.

Elon Musk originally planned for Crew Dragon to land with rockets instead of parachutes. That way the same spacecraft design could land on Mars and Earth. Also, it is "how a rocket should land". Then they discovered that NASA safety concerns were going to slow things down a lot and that a Mars landing craft could be a lot better with a different design. SpaceX's in-development Starship is now the craft that will be able to land on any small planet in the system.

A quote from[1]:

SpaceX now favors another type of recovery.

"The reason we decided not to pursue (powered landings) heavily is it would have taken a tremendous amount of effort to qualify that for safety, particularly for crew transport,” Musk said. “And then there was a time when I thought that the Dragon approach to landing on Mars, where you’ve got a base heat shield and side-mounted thrusters, would be the right way to land on Mars, but now I’m pretty confident that is not the right way, and that there’s a far better approach.”

Musk did not elaborate on the new concept for landing on Mars.

“That’s what the next generation of SpaceX rockets and spacecraft is going to do, so just the difficulty of safely qualifying Dragon for propulsive landings, and the fact, from a technology evolution standpoint, it was no longer in line with what we were confident was the optimal way to land on Mars,” Musk said. “That’s why we’re not pursuing it.

[1]https://spaceflightnow.com/2017/07/19/propulsive-landings-ni...

SpaceX: “You always learn,” [Shotwell] said. “That’s why we test as much as we do.”

Boeing: ...The company is confident in its parachutes, Barrett said.

In the case of Boeing's mission, the chutes ended up working but they set the clock wrong so the mission primary was a fail: https://www.nytimes.com/2019/12/22/science/boeing-starliner-...

Considering all of these stories of how hard parachutes seem to be, it seems surprising that everyone seemed to be against SpaceX's initial plan to do propulsive landings of their capsules. I'd like to see them get that worked out soon, even if only for the cargo capsules at first.