totm nov 2023 SpaceX Discussion Thread

[Ultimate Steve]

Everyone on Reddit is saying that all the holes for the bolts are there because they haven't been filled in yet, the final version will look sleeker.

[Wjolcz]

Not as smooth looking as I expected but if it gets the job done then I don't care.

Edit: are they planning to bring the trunk back too? It would probably be possible to do with what they are planning for the second stage. Except the trunk has less mass and more space to put ballutes and chutes in it. They could "grasshopper" it first before doing bigger and heavier stuff (second stage) later. I mean, they are both cylidrical and the same diameter, right?

Edited May 21, 2018 by Wjolcz

[sevenperforce]

12 hours ago, IncongruousGoat said:

It's entirely possible the engines physically can't run on non-densified propellants anymore. Rocket engines are finicky things when it comes to fuel.

This is not the case.

I mean, it's possible. But it's not accurate. The uprated Merlin 1Ds can still run on LOX and RP-1 at boiling point. They do in every mission; by the time that the entry and landing burns roll around, the tank temperature has increased enough that the propellants are no longer as densified as when they started.

Plus, Word of Elon. They can run on the non-densified propellants. Payload decreases slightly, but sending D2 to the ISS is a sandbag for Falcon 9 Block 5.

17 hours ago, mikegarrison said:

And if R₁ is by far the biggest probability of disaster, which to me seems very likely, then you understand the concern.

If R₃* R₁ is on the order of R₂, then it's not a concern. R₃ is very very low, and so R₂ would have to be nearly as low (or R₁ would have to be ridiculously high) in order for the risk analysis to preclude load-and-go.

2 hours ago, Wjolcz said:

Are they planning to bring the trunk back too? It would probably be possible to do with what they are planning for the second stage. Except the trunk has less mass and more space to put ballutes and chutes in it. They could "grasshopper" it first before doing bigger and heavier stuff (second stage) later. I mean, they are both cylidrical and the same diameter, right?

No, the trunk burns up.

4 hours ago, Ultimate Steve said:

Everyone on Reddit is saying that all the holes for the bolts are there because they haven't been filled in yet, the final version will look sleeker.

That's a relief.

8 hours ago, Brotoro said:

The arrangement of the RCS thrusters intrigues me.

Cosine losses during orbit adjustment maneuvers look like they would be really high.

[magnemoe]

4 hours ago, NSEP said:

Mmmmm.... yes....

Looks like its made out of wood by someone with too much time in their hands, Let's hope that is not the truth.

The capsule look normal as in an metal structure with lots of screw holes to hold thing like rcs blocks hatches and other stuff in place. 
The trunk look like its made of wood. 
Its weird I thought the trunk was basically an aluminum tube with fins / solar panels bolted on an internal framework for holding external cargo and I believe it has radiators on inside 

[sevenperforce]

10 hours ago, CatastrophicFailure said:

 

 

I wonder if pressure-testing includes sequential removal of bolts to test failure. That would explain why they are as-yet uncovered.

I doubt it, of course, because it would be very difficult to ensure non-destructive failure testing.

[zolotiyeruki]

50 minutes ago, sevenperforce said:

I wonder if pressure-testing includes sequential removal of bolts to test failure. That would explain why they are as-yet uncovered.

I doubt it, of course, because it would be very difficult to ensure non-destructive failure testing.

There's also the small issue of finding a volunteer to go remove the bolts one at a time

[StrandedonEarth]

10 minutes ago, zolotiyeruki said:

There's also the small issue of finding a volunteer to go remove the bolts one at a time

Got your volunteer right here...

Er, wait, that's the wrong R2. I meant Robonaut 2:

Edited May 21, 2018 by StrandedonEarth

[CatastrophicFailure]

I think the made-of-wood look to the trunk is to accommodate the solar panels. Either they haven’t been installed yet (most likely, they’re fragile), or those long white strips are protective covers. 

This is still a very much unfinished product. 

[Jaff]

On 5/19/2018 at 2:20 PM, magnemoe said:

Looks like they use the Boeing suits with soft helmets, but that is the lady in front has on her head? Look weird, I could understand an hard hat but it looks weird. 

 

It’s a bump cap...

https://www.google.co.uk/search?q=bump+cap&ie=UTF-8&oe=UTF-8&hl=en-gb&client=safari&dlnr=1&sei=XwgDW5mPEcfQgAbL1o6YCw

 

 

Use them hem in work when hard hats are a bit of a pain

[mikegarrison]

8 hours ago, sevenperforce said:

If R₃* R₁ is on the order of R₂, then it's not a concern. R₃ is very very low, and so R₂ would have to be nearly as low (or R₁ would have to be ridiculously high) in order for the risk analysis to preclude load-and-go.

You are counting your chickens before the eggs are even laid, IMO. There has only once ever been a case where a LES was actually used. And yet, by blithely referring to "R3*R1" you are really saying, "it's OK if the rocket blows up under them, because the LES will save them". That's pretty sketchy as a safety philosophy, IMO.

[sevenperforce]

34 minutes ago, mikegarrison said:

You are counting your chickens before the eggs are even laid, IMO. There has only once ever been a case where a LES was actually used. And yet, by blithely referring to "R3*R1" you are really saying, "it's OK if the rocket blows up under them, because the LES will save them". That's pretty sketchy as a safety philosophy, IMO.

LES has only been activated in a live launch once. LES systems have been tested dozens if not hundreds of times, and every single man-rated vehicle launch (other than the Shuttle) has been a test of the back end of an LES event.

You seem to be setting R₂ equal to 0, which isn't at all warranted. IIRC, rockets have blown up on the pad while fully fueled before, even if it was only in the early stages of orbital rocketry. The equation is quite simple: if the risk of pad RUD while fully fueled is greater than the risk of injury during LES activation times the risk of pad RUD while fueling, you are better off with load-and-go. 

Load-and-go provides 100% protection to ingress assist personnel. 

[mikegarrison]

2 minutes ago, sevenperforce said:

LES has only been activated in a live launch once. LES systems have been tested dozens if not hundreds of times, and every single man-rated vehicle launch (other than the Shuttle) has been a test of the back end of an LES event.

You seem to be setting R₂ equal to 0, which isn't at all warranted. IIRC, rockets have blown up on the pad while fully fueled before, even if it was only in the early stages of orbital rocketry. The equation is quite simple: if the risk of pad RUD while fully fueled is greater than the risk of injury during LES activation times the risk of pad RUD while fueling, you are better off with load-and-go. 

Load-and-go provides 100% protection to ingress assist personnel. 

I think you are arguing from a bias that if SpaceX wants to do it this way, it must be better.

We have already seen a Falcon rocket blow up during fueling. I'm not aware of any rocket that has ever blown up while people were getting on board it.

There is a long history now of ejection seats, which is a very similar technology to LES. They are certainly better than no ejection seat, and they have saved many lives. But they also don't always work, and even if they do work they often result in injuries.

I'm not saying that it's out of the question that it might turn out to be safer to load the crew before the fuel, but it's certainly not a slam dunk that it is. In fact, current experience suggests it's not going to be safer to do that.

I am willing to let the experts decide on this, but I'm more than a little afraid from what I've already seen that it's going to come down to manipulating the safety analysis until it gives the answer that people want it to give. That's the same way of working safety that got NASA into trouble with the Space Shuttle.

[Wjolcz]

18 minutes ago, mikegarrison said:

I think you are arguing from a bias that if SpaceX wants to do it this way, it must be better.

Alright! So @sevenperforce is a fanboy because @mikegarrison says so so he will never be right no matter what therefore he lost this argument.

@mikegarrison gets +1 to fake internet argument points. Well done! Can we be done now?

To contribute to the thread (watch out SpaceX fanboy speaking now!): Now I don't know everything but IMO it's not a 1 or 0 thing. It's more of a "more risk vs less risk" or "more dead vs less dead" problem. You either have 3 people in the capsule while the rocket is being fuelled or you have the crew AND ground crew walking around a fully fuelled rocket that is (AFAIK) being topped all the time they are there.

What is less risky? Me thinks 3 people in the capsule with working LES on a rocket that is being fuelled. But I'm not to decide how to do space stuff so who cares?

Edited May 21, 2018 by Wjolcz

[sh1pman]

Can’t they just do an additional WDR just before launch? Fill it with RP1/LOX, wait for a couple of minutes, make sure everything is fine and nothing tends to explode, empty the tanks, then let the crew in. Fill it up once again and ignite the Merlins. 

Even this is excessive, IMO, because they already do static fire, so that any problems of explosive nature would show up long before there are people sitting on top of the rocket.

[sevenperforce]

13 hours ago, mikegarrison said:

I think you are arguing from a bias that if SpaceX wants to do it this way, it must be better.

Well, no, I am arguing from the "bias" that if I'm the ground support personnel helping Behnken, Boe, Hurley, and Williams into the capsule, I damn well would prefer that the rocket I'm standing inches away from NOT be fueled during the process.

And if I'm Behnken, Boe, Hurley, or Williams, I would damn well prefer to take my chances with LES (which is no more violent than a typical Soyuz EDL, something I would have experienced multiple times already) than climb into a fully-fueled rocket with no safety net. Better the devil you know.

13 hours ago, mikegarrison said:

I'm not saying that it's out of the question that it might turn out to be safer to load the crew before the fuel, but it's certainly not a slam dunk that it is. In fact, current experience suggests it's not going to be safer to do that.

That's your opinion. 

If load-and-go was the only option, and SpaceX was fighting to avoid a complete redesign of their vehicle, then perhaps my analysis would be subject to suspicions of bias. But that's not the case. SpaceX can easily throw Dragon 2 to the ISS without using densified propellants.

12 hours ago, sh1pman said:

Can’t they just do an additional WDR just before launch? Fill it with RP1/LOX, wait for a couple of minutes, make sure everything is fine and nothing tends to explode, empty the tanks, then let the crew in. Fill it up once again and ignite the Merlins. 

Even this is excessive, IMO, because they already do static fire, so that any problems of explosive nature would show up long before there are people sitting on top of the rocket.

This also would fail to certify safety, due to non-destructive testing fatigue.

I used to be part of the US oil and gas pipeline regulatory agency. One concept in high-pressure pipeline safety is the hydrostatic pressure test: you purge the lines of their product, then fill it up with water, cap it at both ends, and pump it up to several times greater than its operating pressure. The theory is that if the pipeline has any defects, flaws, cracks, or leaks, they will rupture during the hydrotest rather than bursting during oil pumping operations.

However, hydrostatic pressure testing has a flaw. Metal pipelines are ductile. If a pipe has small cracks, the hydrostatic pressure test could conceivably cause those cracks to grow via ductile expansion without actually rupturing them. The result is an intact pipeline that will fail the next time at a lower pressure than it otherwise would have. So they declare it safe, pump it full of oil again, and the next time someone switches pressure heads upstream and a transient pressure wave races down the pipeline at the speed of sound, those cracks burst and dump 20,000 gallons of dilbit into someone's backyard.

The same concern exists with any wet dress rehearsal or static fire. All things considered, it is probably safer to perform a WDR or a static fire than it would be to forgo it. But an operator cannot ignore the possibility that a test induces stress fatigues that will cause the next engine or structure to fail under subsequent loads. For example, if you did a WDR, drained the tanks, loaded the crew, and then loaded again, the first WDR could cause thermal contraction in a COPV flaw which would open up cracks, allowing LOX encroachment during the second fuel load.

[sevenperforce]

15 hours ago, mikegarrison said:

We have already seen a Falcon rocket blow up during fueling. I'm not aware of any rocket that has ever blown up while people were getting on board it.

Not while people were actively getting on board. But there have been numerous instances of rockets blowing up while fully fueled, on the pad. Numerous ground support injuries and fatalities as well. Damascus Titan, Soyuz 7K-OK No.1, Soyuz T-10a, Atlas Agena, the Brazilian VLS-3, Nedelin...there are quite a few. 

More people have been killed by fully-fueled rockets on the pad than have been killed in actual launch failures.

Granted, these were all fairly nascent launch programs. But the precedent is there.

[Ultimate Steve]

 

1 hour ago, sevenperforce said:

Soyuz 7K-OK No.1

For the curious, there was a launch abort which resulted in the vehicle still being on the pad, fully fueled. The crews approached the pad, but all the computers and stuff were still on. Because the Earth rotates, after a while the computers said "Hey! We're several degrees off trajectory!" and fired the LES, setting the rocket on fire, killing one person.

[sevenperforce]

15 minutes ago, Ultimate Steve said:

For the curious, there was a launch abort which resulted in the vehicle still being on the pad, fully fueled. The crews approached the pad, but all the computers and stuff were still on. Because the Earth rotates, after a while the computers said "Hey! We're several degrees off trajectory!" and fired the LES, setting the rocket on fire, killing one person.

Craziest sort of error...but makes total sense.

[tater]

 

 

[Ultimate Steve]

Speaking of the launch... Anyone got a mirror/alternate stream? School again... although my last day is Friday, so it won't be a problem soon!

[Wjolcz]

23 minutes ago, Ultimate Steve said:

Speaking of the launch... Anyone got a mirror/alternate stream? School again... although my last day is Friday, so it won't be a problem soon!

The stream is saved on YT.

[Ultimate Steve]

2 minutes ago, Wjolcz said:

The stream is saved on YT.

Yeah, but what if I'm not that patient and want to watch it live but it's blocked?  It's just study hall, for anyone wondering, and this close to the end of the school year we're not doing much of importance anyway.

[Wjolcz]

Just now, Ultimate Steve said:

Yeah, but what if I'm not that patient and want to watch it live but it's blocked?  It's just study hall, for anyone wondering, and this close to the end of the school year we're not doing much of importance anyway.

Oh, I see. Not much will happen during the launch though. The stage won't even land on the barge.

[insert_name]

37 minutes ago, Ultimate Steve said:

Speaking of the launch... Anyone got a mirror/alternate stream? School again... although my last day is Friday, so it won't be a problem soon!

NASA TV may air it since it is carrying a nasa mission

[DAL59]

58 minutes ago, Ultimate Steve said:

Yeah, but what if I'm not that patient and want to watch it live but it's blocked?  It's just study hall, for anyone wondering, and this close to the end of the school year we're not doing much of importance anyway.

Yep its on NASA TV