totm nov 2023 SpaceX Discussion Thread

[tater]

Looked normal.

[sevenperforce]

23 minutes ago, tater said:

Looked normal.

Agreed. They’re hitting the water at 15 mph; the capsule is going to displace approximately half its volume in water and the displaced water is going to be ejected tangentially at impact speed.

This looked substantially the same as past Crew Dragon landings as well as Apollo landings. 

[Beccab]

Raptor was brought on the installation stand to replace the one removed earlier today. This is confirmed as new raptor, the one brought down was RC 67 while this is RC 64

Edited September 19, 2021 by Beccab

[JoeSchmuckatelli]

6 hours ago, Beccab said:

raptor without plumbing

I saw that last night!

Love that it basically says 'hey, we have a lot of people focusing on the tourist / PR / fundraiser flight.. But we have work to do' 

Mind you, we had guests over - and I interrupted everyone's watching of the Auburn / Florida game to watch the splash on the big screen. 

 

Worth it 

[wumpus]

23 hours ago, tater said:

Rockets ARE tanks. Testing "tanks" to me sounds like test articles, vs testing spacecraft/boosters.

There is no way they plan on losing 10% of the vehicles they cryo-proof, static fire, etc. They have lost exactly none in that way since what SN?

While this doesn't apply to SpaceX, I have to wonder just how much the semiconductor example I used for "manufacturing where 10% failures would be a godsend" will apply to the companies that are 3d printing entire rockets.  The main reason that yields are what they are in semiconductors is that there is simply no way to test a chip from the moment the wafer goes in the fab until the chips are all baked on the wafers (before they are sliced and diced).  3d printing will have a similar issue, and probably require some sort of constant visual inspection, with likely other forms of RF (X-ray?) inspection done during printing.

[Beccab]

Raptor installation ongoing on B4

[JoeSchmuckatelli]

They look to be adding more tiles, too 

[mikegarrison]

15 miles per hour is about the speed you would hit the water from a 2.3 meter fall. So if you have ever jumped off of a 3 meter (10-ft) diving board, you have hit the water faster than that.

But when people dive (or jump) into the water, they try not to land flat ("belly flop"). Going in long-wise means a slower deceleration. You go further under the water, but you don't hit as hard. These capsules can't do that, so it's more like belly-flopping into the water.

Edited September 19, 2021 by mikegarrison

[RealKerbal3x]

4 minutes ago, JoeSchmuckatelli said:

They look to be adding more tiles, too 

That's just the thumbnail which is a photo from a few weeks ago. On other cams I don't see any activity adding tiles to S20, the heatshield seems to be largely complete.

[JoeSchmuckatelli]

Interesting article on SX and I4 and the risks of space flight (especially commercial spaceflight). 

Re: the first crewed Dragon flight:

'That first flight test, which Hurley and fellow NASA astronaut Bob Behnken completed last year, was quickly declared a success. The real assessment came well after the astronauts were out of the water, when engineers looked at the data and inspected the hardware. It turned out that during Hurley and Behnken’s descent through the atmosphere, the heat shield, the hardware that protects the capsule from the scorching conditions of reentry, eroded more than SpaceX had expected'

https://www.theatlantic.com/science/archive/2021/09/spacex-inspiration-4-splashdown/620128/

They don't explain why the Crew Dragon ablation was different from what they saw on the Cargo variant unfortunately. 

About the dangers:

'Complacency kills. “Ten flights down the line, when it becomes routine, that’s when you really have to be careful "' 

... 'it’s always a shock. “The public never expects people to die,” ' 

[AHHans]

56 minutes ago, JoeSchmuckatelli said:

Interesting article on SX and I4 and the risks of space flight (especially commercial spaceflight). 

Well, yes. But reading a bit between the lines that article also tells me that commercial space travel is needed to get spaceflight from it current high-risk status to the low-risk status that air travel has today.

Off-topic: anyone who wants to listen how today's plane safety was written in blood can have a look at this youtube channel: https://www.youtube.com/c/MiniAirCrashInvestigation

[mikegarrison]

5 minutes ago, AHHans said:

how today's plane safety was written in blood

I hate that phrase, because it misses the crucial element.

Aviation safety works because it's not about BLAME. It's about ROOT CAUSES. So many people don't understand this. Politicians especially love to find someone to blame.

The idea is that if you look for causes, rather than looking to assign blame, you can find things that are useful to fix going forward. If you just want to find someone to blame, all you end up doing is punishing people for actions in the past. It's not nearly as effective.

That's not to say there is never any blame to found, but a search for blame tends to make people to hide things. A search for causes tends to make people show things.

[tater]

2 hours ago, mikegarrison said:

15 miles per hour is about the speed you would hit the water from a 2.3 meter fall. So if you have ever jumped off of a 3 meter (10-ft) diving board, you have hit the water faster than that.

But when people dive (or jump) into the water, they try not to land flat ("belly flop"). Going in long-wise means a slower deceleration. You go further under the water, but you don't hit as hard. These capsules can't do that, so it's more like belly-flopping into the water.

You'll note that the Dragon intentionally enters the water at an angle for that reason (and the seats are on the water entry side, and tilted (with shock absorbers)—just like Orion, and Apollo:

Still closer to belly flop than a human dive, but a little better than dead flat.

[JoeSchmuckatelli]

43 minutes ago, mikegarrison said:

Aviation safety works because it's not about BLAME. It's about ROOT CAUSES

This is the hardest thing to communicate to the public 

[tater]

That Atlantic author... meh.

Obviously spaceflight carries risk, and we know the risk requirements for commercial crew LOC, which are ~3X more safe than they retrospectively decided the last Shuttle missions were (by the end ~1:90, right?).

 

[mikegarrison]

1 minute ago, tater said:

That Atlantic author... meh.

Obviously spaceflight carries risk, and we know the risk requirements for commercial crew LOC, which are ~3X more safe than they retrospectively decided the last Shuttle missions were (by the end ~1:90, right?).

The Atlantic article is dead on, in at least one respect. The biggest issue is "risk normalization". That's essentially what got BOTH space shuttles. They knew they had problems with the o-rings and the foam, but the more times it happened without a catastrophe, the more they decided it was just normal.

[tater]

I meant her in general, I think I found her twitter... not to my taste.

WRT to risk, sure, safety has to be an ongoing concern. FWIW, they seem appropriately concerned—Musk himself said in that Tim Dodd tour/interview that crew flights were completely different than Starship testing, that everything on crew flights needs to be perfect, every time. That's certainly what I'd want to hear if I was flying... and even then, it's a non-zero risk.

[mikegarrison]

40 minutes ago, tater said:

I meant her in general, I think I found her twitter... not to my taste.

I got curious about this and looked up her name and her twitter feed. I saw nothing unusual or objectionable.

[tater]

4 minutes ago, mikegarrison said:

I got curious about this and looked up her name and her twitter feed. I saw nothing unusual or objectionable.

I might be misremembering. That article seems OK. My space news comes from NSF or spaceflightnow primarily, I have a tendency to ignore anything from the normal press.

(maybe I'm confusing her with the reporter at the verge?)

Edited September 19, 2021 by tater

[mikegarrison]

She apparently has a harassing Twitter stalker, but that's sadly not at all unusual for women.

[tater]

11 minutes ago, mikegarrison said:

She apparently has a harassing Twitter stalker, but that's sadly not at all unusual for women.

It was nothing like that... I think I mixed up reporters.

[magnemoe]

51 minutes ago, tater said:

I meant her in general, I think I found her twitter... not to my taste.

WRT to risk, sure, safety has to be an ongoing concern. FWIW, they seem appropriately concerned—Musk himself said in that Tim Dodd tour/interview that crew flights were completely different than Starship testing, that everything on crew flights needs to be perfect, every time. That's certainly what I'd want to hear if I was flying... and even then, it's a non-zero risk.

Twitter has an bad reputation because all the crazy people there, but they tend to focus on  pop culture stuff like movies or games, probably also sport. Now spaceX start to become pop culture.
And I expect Twitter to hate bate people into treads because it give  more clicks. Facebook has done this a lot. 
 

[mikegarrison]

It does seem that her Twitter stalker was attacking her for being not sufficient complementary (i.e. "a hater") of Musk and SpaceX.

But most often people who stalk women on Twitter mainly do so because they are women. Whatever they use as their excuse for it is usually only of secondary importance.

Edited September 19, 2021 by mikegarrison

[Codraroll]

3 hours ago, JoeSchmuckatelli said:

It turned out that during Hurley and Behnken’s descent through the atmosphere, the heat shield, the hardware that protects the capsule from the scorching conditions of reentry, eroded more than SpaceX had expected'

The article doesn't say how much more, though, or what the margins were. That's kinda crucial for assessing the overall safety of the solution. If SpaceX had expected to burn away 10-15% and 80% was eroded upon landing, it would be a giant fricking problem, but if it had been 16%, there would still have been a safety margin of 525% (instead of the expected 567). It's still a bit of an issue if the heat shield erodes more than expected, but that's also why the designs have margins - so that even if something turns unexpected, the system is strong enough to withstand it. I would guess the heatshield in particular to have a really high safety margin, since it's such a critical component. It's probably built to withstand a few times more battering than the designers expect it to encounter, just in case.

[cubinator]

1 hour ago, Codraroll said:

The article doesn't say how much more, though, or what the margins were. That's kinda crucial for assessing the overall safety of the solution. If SpaceX had expected to burn away 10-15% and 80% was eroded upon landing, it would be a giant fricking problem, but if it had been 16%, there would still have been a safety margin of 525% (instead of the expected 567). It's still a bit of an issue if the heat shield erodes more than expected, but that's also why the designs have margins - so that even if something turns unexpected, the system is strong enough to withstand it. I would guess the heatshield in particular to have a really high safety margin, since it's such a critical component. It's probably built to withstand a few times more battering than the designers expect it to encounter, just in case.

The Dragon heat shield is definitely designed to fly multiple times without being replaced. It should be thick enough for a few reentries.