totm nov 2023 SpaceX Discussion Thread

[Beccab]

https://fcc.report/IBFS/SAT-AMD-20210818-00105

SpaceX changes with the FCC the future starship launches, V2.0 will be done with starship starting next year and V1.5 will be done with Falcon 9 later in 2021

[Dfthu]

"SpaceX Starlink satellites responsible for over half of close encounters in orbit"

  https://www.space.com/spacex-starlink-satellite-collision-alerts-on-the-rise

[tater]

26 minutes ago, Dfthu said:

"SpaceX Starlink satellites responsible for over half of close encounters in orbit"

  https://www.space.com/spacex-starlink-satellite-collision-alerts-on-the-rise

OneWeb only has 80 such encounters per week vs SpaceX with 500 (from the article).

OneWeb has 250 sats per article. SpaceX has 1700 per article. 250/80 is 3.125 per sat. Times 1700 sats that's 544. So I guess SpaceX is doing slightly better than OneWeb?

Obviously any of these large constellations is going to have loads of encounters. The more sats, the more encounters.

Edited August 19, 2021 by tater

[magnemoe]

3 hours ago, Beccab said:

It's not exactly an error in S20 to be like that, SN15 and previous proved that it can work; it is just an improvement that we will see in future iterations, perhaps not even in S21. Once it is implemented it should probably reduce the amount of heat shield tiles required and make the flaps more effective, but there's nothing keeping S20 from flying given how much stuff needs to be verified even before the flaps start making any difference

This, first test is primarily to get it to orbit.  Then to have superheavy do its boostback and probably how accurate they can land it in the ocean. 
They don't really expect it to survive reentry but it will be set up for an soft landing if it can. 

Make me think, for later versions will they try for an west coast landing? Not for reuse, landing it on land make it easy to check out the condition of it. 

[Deddly]

1 hour ago, magnemoe said:

They don't really expect it to survive reentry

I thought the main purpose of the orbital launch was to test its ability to re-enter and land safely.

[Beccab]

26 minutes ago, Deddly said:

I thought the main purpose of the orbital launch was to test its ability to re-enter and land safely.

To quote musk, "If it clears the tower it's a success". Flight will be full of unknowns, even if we as armchair scientists do believe completing the ascent profile will be likely

 

But as magnemoe said, S20 surviving reentry is between very unlikely and impossible. Musk said many times that they expect to blow up a lot of them before reentry is successful

Edited August 19, 2021 by Beccab

[tater]

 

 

 

 

[MKI]

If you could bet on SN20+B4 chances of failure, what stage do you think would be the most likely to fail?

(this honestly could be a poll but meh)

 

I'm debating between re-entry and landing. I have a hard time seeing it fail during ascent, but the heat shield tiling is looking worrisome unless they update large portions of it before the launch. Landing has already had a questionable record, and SN20, if it gets that far, will be going through the gauntlet and I wonder what that will do to its landing chances. 

 

There is also the possibility it actually makes the whole trip, would be completely insane. 

Edited August 19, 2021 by MKI
typos/grammars

[Beccab]

1 minute ago, MKI said:

If you could be on SN20+B4 chances on failure, what part do you think would be the most likely stage to fail?

(this honestly could be a poll but meh)

 

I'm debating between re-entry and landing. I have a hard time seeing it fail during ascent, but the heat shield tiling is looking worrisome unless they update large portions of it before the launch. Landing has already had a questionable record, and SN20, if it gets that far, will be going through the gauntlet and I wonder what that will do to its landing chances. 

 

There is also the possibility it actually makes the whole trip, would be completely insane. 

Hmmm, I bet on reentry. We wouldn't see it do a bellyflop and land in the sea, but at least we will have pics of S20 in orbit

[RealKerbal3x]

4 minutes ago, MKI said:

If you could be on SN20+B4 chances on failure, what part do you think would be the most likely stage to fail?

(this honestly could be a poll but meh)

 

I'm debating between re-entry and landing. I have a hard time seeing it fail during ascent, but the heat shield tiling is looking worrisome unless they update large portions of it before the launch. Landing has already had a questionable record, and SN20, if it gets that far, will be going through the gauntlet and I wonder what that will do to its landing chances. 

 

There is also the possibility it actually makes the whole trip, would be completely insane. 

Definitely re-entry. The launch should go fine - re-entry is the big unknown. I know Elon was talking about leaving the pad without exploding already being a success in Tim Dodd's interview, but he said similar things before Falcon Heavy's first launch and we know how much of a success that was.

[Lukaszenko]

I'd bet on or close to launchpad, and I'd bet lots of money. Not because I think it will explode there, but because that would be the worst outcome. I often like to bet on the worst outcome, because then if it comes to be, at least some good comes out of it! 

[Elthy]

Im not sure about the separation using just rotation of the combined rocket which afaik has never been done before. Lots of stuff that can go wrong, we have also seen that SpaceX had issues with ullage before. And they lost a Falcon1 during this.

[CatastrophicFailure]

1 hour ago, MKI said:

If you could bet on SN20+B4 chances of failure, what stage do you think would be the most likely to fail?

 

Been mulling this over myself for a while, I think I give it 50/50 odds of surging to/through staging (that’s a LOT of plumbing), 50/50 that Starship makes it to SECO (Rvacs remain “untested”), then maybe 25% chance of surviving reentry intact enough to even try landing. So many unknowns here, but up til reentry SpaceX at least has a lot of data on things. 
 

41 minutes ago, Elthy said:

Im not sure about the separation using just rotation of the combined rocket which afaik has never been done before. Lots of stuff that can go wrong, we have also seen that SpaceX had issues with ullage before. And they lost a Falcon1 during this.

Great opportunities to learn from those failures.  That whole stagey-flippy thing sounded nuts to me til I saw the animation a couple pages back, I think it will seem much less extreme in the flesh, as it were. 

[Kerwood Floyd]

Well, there's no way it survives re-entry. So, like @Elthy I think I'd put my money on staging. Like @Lukaszenko this is mostly to protect myself from too much disappointment. 

[magnemoe]

27 minutes ago, Elthy said:

Im not sure about the separation using just rotation of the combined rocket which afaik has never been done before. Lots of stuff that can go wrong, we have also seen that SpaceX had issues with ullage before. And they lost a Falcon1 during this.

Yes, however its something who is fairly easy to simulate and the skirt has to survive max-q so an small bump will be nothing. 
Main issue is that the connecting lugs on superheavy might hit an engine, or even the edge of superheavy could easy hit the central engines. Now you could decouple all the lugs than the one closest to earth and have SH try to tilt up who will force SH tail and SS nose down. 
It sounds weird to me but I guess the math work out. 
Falcon 1 ullage issues is kind of dated at this point, but guess ullage is part of this, they don't want to have all the first stage liquids move up to the top of tanks and then have to wait for it to settle before starting boost back. 

[Beccab]

Netflix Inspiration 4 documentary trailer is out, part 1 and 2 will come out 6 september

If we ignore the Ariane 5 and Saturn V separation footage it doesn't seem bad. Hopefully whoever chose those shots for the trailer wasn't involved in anything else

[tater]

Falcon 1, like Falcon 9 had the vacuum engine bell inside the interstage. Residual thrust on the booster after MECO resulted in the stage colliding with the delicate engine bell. Seems pretty unlikely with SS as the engines are inside the skirt.

[tater]

These are mirrored on both sides:

 

[CatastrophicFailure]

22 minutes ago, tater said:

These are mirrored on both sides:

Test patch for that whole "methane bleeding" thing maybe?

[JoeSchmuckatelli]

3 hours ago, Kerwood Floyd said:

Well, there's no way it survives re-entry. So, like @Elthy I think I'd put my money on staging. Like @Lukaszenko this is mostly to protect myself from too much disappointment. 

I think odds are maybe 50/50 of the ship making it through the plasma.  From what I've read the hull steel is thicker than most - and we all know about space junk that's survived reentry intact enough to leave a dent in the dirt. 

If that happens - I'd again give them odds on engine start (presumes it is autonomous / doesn't need a radio command to initiate the landing attempt).. But I'm confident (after reading the stuff about changing the front flaps) that it will splash hard rather than hoover. 

My hope is that they have some way of filming the end of the reentry (and they share it). 

[mikegarrison]

13 hours ago, Beccab said:

To quote musk, "If it clears the tower it's a success". Flight will be full of unknowns, even if we as armchair scientists do believe completing the ascent profile will be likely

It's always nice to set the bar as low as possible, because that makes it so much easier to declare success.

I'm just once again struck by what seems to be a double standard among SpaceX fans. Anything that doesn't go perfectly in a test flight for somebody else is an abject failure, but if it's SpaceX, it's "a great learning experience".

2 hours ago, CatastrophicFailure said:

Test patch for that whole "methane bleeding" thing maybe?

Test patch for something, anyway. Maybe just a control to see what would happen if tiles fail?

[CatastrophicFailure]

13 minutes ago, mikegarrison said:

I'm just once again struck by what seems to be a double standard among SpaceX fans. Anything that doesn't go perfectly in a test flight for somebody else is an abject failure, but if it's SpaceX, it's "a great learning experience".

There's very clear differences that, ahem, non-SpaceX fans tend to ignore when pointing this out: 

Starship is not an operational vehicle, it's not even close to being operational. Ship 20's test flight is at best a proof of concept, from the very outset its not expected to go perfectly, or even go well, it's purpose is to gather data, anything at all beyond that is just icing. 

That's very different from, say, a verification test flight of a vehicle that's supposed to be "ready," that's intended to carry people on the very next flight, or is otherwise validating systems that are expected to be "finished."

[Terwin]

4 minutes ago, mikegarrison said:

It's always nice to set the bar as low as possible, because that makes it so much easier to declare success.

I'm just once again struck by what seems to be a double standard among SpaceX fans. Anything that doesn't go perfectly in a test flight for somebody else is an abject failure, but if it's SpaceX, it's "a great learning experience".

 

When the stated and contractually obligated goal is to dock with the ISS and your can't even get into a high enough orbit to do so, it is hard to call that a success, especially when you spend huge amounts of money on each launch.

When launching a new rocket that is already out of date with a publicly stated goal of 'clearing the launch tower', then the entire stack exploding at MECO is a success by the stated objective of the launch.

Just like if the CEO of Ford says they will make $1.2B in profit this year, then they only manage to make $900M, then that is a failure, even if they only made $800M last year.

and Tesla saying they will make $10M in profit this year, then just squeaking by at $10.2M would be a success.

 

When an appropriate authority figure publicly states the goal of a launch and that goal is achieved, then that is clearly a success, even if said goals are not what we might wish them to be.

Unless you want to call Apollo 8 a failure for not landing on the moon when their mission objective was just to enter lunar orbit and return safely?

 

SpaceX can have such low goals because they repeatedly state that they are taking a 'fail-fast' approach with rapid iterations, and it is easy to see that they are pumping out new rockets and engines at a break-neck speed(even faster than they can get permissions to launch them, such that unneeded rockets need to be scrapped so that they don't take up too much space)

[mikegarrison]

9 minutes ago, CatastrophicFailure said:

There's very clear differences that, ahem, non-SpaceX fans tend to ignore when pointing this out: 

Starship is not an operational vehicle, it's not even close to being operational. Ship 20's test flight is at best a proof of concept, from the very outset its not expected to go perfectly, or even go well, it's purpose is to gather data, anything at all beyond that is just icing. 

That's very different from, say, a verification test flight of a vehicle that's supposed to be "ready," that's intended to carry people on the very next flight, or is otherwise validating systems that are expected to be "finished."

True enough, but you know that if a crew had been on the Starliner first flight they would have survived just fine. In fact, actually they probably could have fixed the issue, because they would not have had the problem of losing contact with the spacecraft when it passed out of range of the ground-based controllers. That being said, it doesn't mean there was no issue. There was.

Anyway, I'm not here to claim the Starliner hasn't had some embarrassing problems. But I still think there is a double-standard in this forum where SpaceX problems are, if anything, celebrated -- "move fast and break things!" -- while anybody else's problems are attacked.

Maybe it's just a disconnect in experience. I've been part of this industry for more than 30 years, and I know that internally the attitude toward competitors, while fierce, is quite different from the rather partisan nature of discussions in this forum. And it's hard not to react to partisan attacks with partisan counterattacks.

[tater]

48 minutes ago, mikegarrison said:

I'm just once again struck by what seems to be a double standard among SpaceX fans. Anything that doesn't go perfectly in a test flight for somebody else is an abject failure, but if it's SpaceX, it's "a great learning experience".

Because they are building these things specifically to test? If it's a test flight, data.

F9 booster recovery was destructive, but only after the booster had done its job anyway.

If SLS failed in the Green Run in some catastrophic way, it would not have just been a data point, but likely a multi-year delay—because that was a mission flight article.

I think the methodology matters. If the method is to component test, then build a flight article you 100% expect to work, then a failure is a problem. If your test article is cheap, and replacing it is fast?