totm nov 2023 SpaceX Discussion Thread

[JoeSchmuckatelli]

47 minutes ago, tater said:

Undocking:

 

They're doing a fly-around photography tour of the ISS; first that's been done in a while.

[tater]

Go for deorbit.

WB57 airborne.

Burn at 8:41 CST, splashdown at 9:33 CST.

[tater]

AOS

 

Drogues.

Mains.

[mikegarrison]

Looks like one main has failed to open.

[tater]

1 looks partial

 

Inflated now

[mikegarrison]

1 minute ago, mikegarrison said:

Looks like one main has failed to open.

OK, now it has opened up.

 

[tater]

Welcome home, Crew-2.

3 minutes ago, mikegarrison said:

OK, now it has opened up.

Yeah, it was slow to get there, then stayed reefed a little long—I guess with the other 3 fully open, the forces pulling the reefs out would be lower.

[Meecrob]

6 minutes ago, mikegarrison said:

OK, now it has opened up.

There's still going to be a meeting later on about it, I bet.

[mikegarrison]

4 minutes ago, tater said:

I guess with the other 3 fully open, the forces pulling the reefs out would be lower.

Makes sense.

[JoeSchmuckatelli]

8 minutes ago, tater said:

Welcome home, Crew-2.

Yeah, it was slow to get there, then stayed reefed a little long—I guess with the other 3 fully open, the forces pulling the reefs out would be lower.

'chutes can steal air from one another. 

The phenomenon can get interesting in a mass drop of troops (where the guy below you can steal your air and abruptly drop you... Only to have you uncontrollably return the favor in a' race to the bottom'.) 

With air dropped loads - two out of three 'chutes filled usually = a good drop. 

Not sure whether NASA would agree - but they usually like precision 

Edited November 9, 2021 by JoeSchmuckatelli

[tater]

2 minutes ago, Meecrob said:

There's still going to be a meeting later on about it, I bet.

Yeah. For sure.

3/4 of the chutes need to work, every time. (think they are designed for 3 chutes being OK, just not optimal)

[Brotoro]

2 hours ago, JoeSchmuckatelli said:

With air dropped loads - two out of three 'chutes filled usually = a good drop. 

Not sure whether NASA would agree - but they usually like precision 

*cough*Apollo15*cough*

[JoeSchmuckatelli]

7 hours ago, Brotoro said:

*cough*Apollo15*cough*

I'd have to look that up.  

So before I do - let me hazard a guess that NASA stuff is so engineered and weight focused that there is / was little wiggle room. 

 

[magnemoe]

8 hours ago, JoeSchmuckatelli said:

'chutes can steal air from one another. 

The phenomenon can get interesting in a mass drop of troops (where the guy below you can steal your air and abruptly drop you... Only to have you uncontrollably return the favor in a' race to the bottom'.) 

With air dropped loads - two out of three 'chutes filled usually = a good drop. 

Not sure whether NASA would agree - but they usually like precision 

Was it what who happened here? 
As I understand parachutes like this uses an sheer line who stop the parachutes from fully inflated. 
Parachutes will be ejected but will only open partial like in KSP, benefit is that you do not get full drag at high velocity, I assume it also reduce the chance of parachutes tangles as all will be full out before they inflates. 

Now I'm not sure how the sheer lines work, I assume they snap as drag increase and the force on the parachutes lines increase. 
In this case yes if the three parachutes stole air from the last this can explain why that parachute opened late.  
It will also make it an very minor thing as increased drag should snap the cheer line sooner or later. 

[JoeSchmuckatelli]

11 hours ago, Brotoro said:

*cough*Apollo15*cough*

So this was an interesting read: apollo-15-mission-anomaly-report-no.-1-main-parachute-failure.pdf (nasa.gov)

My first thought at seeing the image on page 4 of the report was 'that's a parachute with cut risers'.  

Indeed, that's what they found, too "The most probable cause of the anomaly was the burning of raw fuel (monomethyl hydrazine) being expelled during the latter portion of the depletion firing and this resulted in exceeding the parachute-riser and suspension-line temperature limits." (although melted, rather than cut).

So - not at all what I speculated about, above with stolen air.  

Anyway - it was a good drop: everyone survived.

...

Of note: had it been one of the steel cable risers - the chute would have flown free.  Failure in a fabric riser basically eliminates whole sections of suspension lines - which is where you get that weird, half deflated look.

Also - found this funny:  Page 13 notes the presence of a pesky Russian ship (presumably doing nefarious, Cold War things). 

I say we blame them.

Case closed.

 

Edited November 9, 2021 by JoeSchmuckatelli

[mikegarrison]

The point was more that there was a disconnect between the comments on the video coverage "four healthy mains" and what we could clearly see was one main struggling to open.

However, they must have noticed that themselves, because eventually one of the commentators finally said something like "one of the mains is opening slowly, but we are told it is still within nominal tolerances".

[RCgothic]

Potential static fire tomorrow:

 

 

 

[tater]

Live in 20 hours.

[tater]

 

 

[mikegarrison]

From what I can gather quickly off the web, it seems that "lagging" parachutes is a known issue with multi-chute clusters. It's not considered an ideal outcome, because it places more stress on the non-lagging chutes, but neither is it an "OMG what just happened?!" thing either.

[sevenperforce]

3 hours ago, mikegarrison said:

From what I can gather quickly off the web, it seems that "lagging" parachutes is a known issue with multi-chute clusters. It's not considered an ideal outcome, because it places more stress on the non-lagging chutes, but neither is it an "OMG what just happened?!" thing either.

Makes sense. I was worried when I was watching it, but they kept insisting “four healthy chutes” and evidently they were right.

Does anyone know how many chutes are necessary to make the impact survivable?

[cubinator]

22 minutes ago, sevenperforce said:

Does anyone know how many chutes are necessary to make the impact survivable?

I know they can get by with three. I think they might even be able to go with two.

[Beccab]

13 minutes ago, cubinator said:

I know they can get by with three. I think they might even be able to go with two.

As far as I remember, in an emergency 2 chutes make for a harder landing but still survivable. Like a soyuz landing without the solid rocket I think

[mikegarrison]

39 minutes ago, cubinator said:

I know they can get by with three. I think they might even be able to go with two.

The thing is, with parachute landings, if you have only two chutes, well then I guess you try to survive it. It's not like you have any other choice at that point.

People have survived going over waterfalls in a barrel. Of course, some have also not survived.

[Brotoro]

SpaceX launch coverage is live.

But no need to get too excited yet... launch is in 4 hours and 15 minutes.