totm nov 2023 SpaceX Discussion Thread

[StupidAndy]

14 hours ago, Mitchz95 said:

I didn't even know there was another launch this year!

if you want to see all the next (and previous) launches you can go to this wikipedia page and see when the next launches are

[sevenperforce]

34 minutes ago, sh1pman said:

Is there any info on FH max payload to LEO with full reusability? Excluding S2, obviously.

I mean they say it’s 63t in fully expendable variant, so I wonder how much it’s going to lift with three reusable cores.

Probably around 35-40 tonnes to LEO, with the two boosters returning to the landing pads and the core landing on the ASDS. Fully-reusable throw to GTO is around 8 tonnes, though I think that's for all three boosters RTLS. 

There is a huge gulf between FH's LEO performance and its GTO performance, because LEO can make better use of its low-isp, high-thrust upper stage than GTO. Anything going beyond LEO really either needs a low-mass kick stage or a very high-energy propellant, for maximum mass efficiency.

51 minutes ago, tater said:

Yeah, I thought that looked different as well. Using paid launches to test stuff is what they do, after all.

FH is going to be stunningly cool.

According to the experts over at NSF, that camera is rotated 90 degrees so it was a normal flip.

It does get me thinking, though. Ideally, they'd want as much separation between the two side boosters as possible, to prevent any possible interactions. Flipping horizontally and firing up the three boostback engines mid-flip would push the boosters as far away from each other as possible; then they'd be following a trajectory such that their closest approach would be the landing burn itself.

[tater]

Y'all need some SpaceX rocket porn:

 

 

(my bad, looks like it's a shortened version of the one posted up thread... but who cares.)

[Jaelommiss]

1 hour ago, StupidAndy said:

if you want to see all the next (and previous) launches you can go to this wikipedia page and see when the next launches are

It's interesting to look back at previous flights. I didn't realize that they hadn't failed a mission in 15 months (17 consecutive successes), or that it's been 18 months since they last failed to land a booster, or that a quarter of this year's flights were on reused boosters.

[sevenperforce]

29 minutes ago, Jaelommiss said:

It's interesting to look back at previous flights. I didn't realize that they hadn't failed a mission in 15 months (17 consecutive successes), or that it's been 18 months since they last failed to land a booster, or that a quarter of this year's flights were on reused boosters.

And of course they've never had a launch failure on a flight-proven booster.

Wonder how long that will last.

I also wonder if the failure rate for new boosters (as in, all orbital launches from October 4, 1957 through the present, apart from the three reflown ones) will ever be lower than the failure rate for flight-proven boosters.

[PB666]

1 hour ago, sevenperforce said:

And of course they've never had a launch failure on a flight-proven booster.

Wonder how long that will last.

I also wonder if the failure rate for new boosters (as in, all orbital launches from October 4, 1957 through the present, apart from the three reflown ones) will ever be lower than the failure rate for flight-proven boosters.

They have a nine-engine first stage, slightly before Max Q that is pretty much fail-proof because they can loose any engine and they have enough thrust from the remaining engines to complete the task. it would have to be something catastrophic, like the blowing up of a turbo pump. Of course the second stage could fail to fire, in which case it will fall back to earth.

There is a marginal utility of extending the life of the non-expendable version of the rocket at present, once you have recycled it 4 or 5 times you could pretty much write off the hull as its recycling value.

[magnemoe]

1 hour ago, PB666 said:

They have a nine-engine first stage, slightly before Max Q that is pretty much fail-proof because they can loose any engine and they have enough thrust from the remaining engines to complete the task. it would have to be something catastrophic, like the blowing up of a turbo pump. Of course the second stage could fail to fire, in which case it will fall back to earth.

There is a marginal utility of extending the life of the non-expendable version of the rocket at present, once you have recycled it 4 or 5 times you could pretty much write off the hull as its recycling value.

Remember they have spare fuel because of landing. Loosing an engine unless late and they probably lose the first stage. 
Thinking of the first dragon mission who lost an engine, now it would have enough margin but they would lose first stage. 

You have other failure points, structure and tanks has been the cause for the two fails so far. Would not be surprised if something like this pops up later especially with repeated reuse. 
Landing is also dangerous and we are probably more likely to get crash landings than failed launches. 

As I understand the new version would be more reusable. 

[tater]

Loosing the first stage is sort of an opportunity cost for future use, but they are charging enough that they make money even if S1 takes a swim. Losing S1 to get a customer to orbit is a price they'd pay every day, which would just make them like every other launch provider on Earth.

Some interesting questions answered here (sorry if it was already posted):

 

[PB666]

24 minutes ago, magnemoe said:

Remember they have spare fuel because of landing. Loosing an engine unless late and they probably lose the first stage. 
Thinking of the first dragon mission who lost an engine, now it would have enough margin but they would lose first stage. 

You have other failure points, structure and tanks has been the cause for the two fails so far. Would not be surprised if something like this pops up later especially with repeated reuse. 
Landing is also dangerous and we are probably more likely to get crash landings than failed launches. 

As I understand the new version would be more reusable. 

I have mapped the power output of the F9 based on its accelerations, just before Max Q it drops power by about 20% but it never increases power afterwards, it continues past MaxQ with about 70% of its power and throttles down toward the end of flight. In theory with a loss of one engine (unless it was the center engine) they would have to kill one more engine, meaning they lost 22% of their maximum power; however, given that they still have  a reserve of about 20% and so just operate the remaining engines at full thrust and you can still recover the first stage.

 

[CatastrophicFailure]

14 minutes ago, PB666 said:

In theory with a loss of one engine (unless it was the center engine) they would have to kill one more engine

Don’t the other engines automatically gimbal to compensate, like the Saturn V? On the Dragon flight when the engine went bang, I recall all eight of the rest still running the whole time. 

[PB666]

1 minute ago, CatastrophicFailure said:

Don’t the other engines automatically gimbal to compensate, like the Saturn V? On the Dragon flight when the engine went bang, I recall all eight of the rest still running the whole time. 

They can do that also, and in fact if you lost an engine close to launch that is what you would have to do, but after 50 seconds, you can just balance your thrusters. There are steer problems with gimballing over time. Its sort of like turning an aircraft without using the horizontal stabilizer. Not that its a big problem because as soon as the second stage fires you can compensate, but on the re-land part of the mission you probably want to use a balance of thrusters.

[CatastrophicFailure]

2 minutes ago, PB666 said:

but on the re-land part of the mission you probably want to use a balance of thrusters

I was only thinking ascent, but now that you mention it, I wonder what the pre-programmed flight protocols are for landing? If they loose an engine during boostback or reentry (or one of those three-engine GTO barge landings), I wonder if the flight computer will try to save it or just go FTS...

(I’m guessing human responses are out of the loop at that point, ‘cept for the range guy with the big red button.)

[KSK]

1 hour ago, CatastrophicFailure said:

I was only thinking ascent, but now that you mention it, I wonder what the pre-programmed flight protocols are for landing? If they loose an engine during boostback or reentry (or one of those three-engine GTO barge landings), I wonder if the flight computer will try to save it or just go FTS...

Good effort on the deliberately misspelled last word there. Nice to see forum sensibiliies being upheld.

Ahem. FTS I would have thought. Burning longer with fewer engines wouldn't be an option for boostback or reentry burns I wouldn't think?

Edited December 19, 2017 by KSK

[CatastrophicFailure]

3 minutes ago, KSK said:

Good effort on the deliberately misspelled last word there. Nice to see forum sensibiliies being upheld.

 

Wha? FTS = Flight Termination System.

Wait, what did you think I said? 

On second thought, you probably can’t say. 

[KSK]

1 minute ago, CatastrophicFailure said:

Wha? FTS = Flight Termination System.

Wait, what did you think I said? 

On second thought, you probably can’t say. 

Just my wee jest. I'm 100% sure you meant to say exactly what you said. I just thought the resemblance to a common three-letter acronym denoting impatience, resignation or anger (depending on intensity) was too good to miss. Plus I could just imagine the flight computer talking to itself on the way down.

"Aaaaand - pop! And spin and wheeeeeee - that was a close one! Bet that looked good on the tracking camera. Right - boooooooostback. Watch out LZ1 - I'm a coming in *hot*!'

"And re-entr.... *KABLAM*.."

"Oh F...

[magnemoe]

2 hours ago, CatastrophicFailure said:

I was only thinking ascent, but now that you mention it, I wonder what the pre-programmed flight protocols are for landing? If they loose an engine during boostback or reentry (or one of those three-engine GTO barge landings), I wonder if the flight computer will try to save it or just go FTS...

(I’m guessing human responses are out of the loop at that point, ‘cept for the range guy with the big red button.)

I guess they can rotate who of the outer 8 engines to use, not only fail but also engines with issues. 

[CatastrophicFailure]

52 minutes ago, magnemoe said:

I guess they can rotate who of the outer 8 engines to use, not only fail but also engines with issues. 

As I understand it, only 3 engines are equipped for in-flight restart. So if one of those goes out, the flight software might have to get... creative...

Or as @KSK said, colorful... 

[PB666]

5 hours ago, CatastrophicFailure said:

As I understand it, only 3 engines are equipped for in-flight restart. So if one of those goes out, the flight software might have to get... creative...

Or as @KSK said, colorful... 

Hmm, looks like we have identified a flaw in the booster return program, you should right up a report and submit it to spaceX along with a bill.

BTW, the have more than enough thrust to land with two engines. The only problem is the LZ would need to be quite large, since the rocket will drift. You would have to start the burn sooner. However if the engine failed and the burnback program was not aware, or the failure was progressive, it probably would not have time to compensate.

It could just plop onto the LZ after zero fuel and a large 'popping' sound.

 

[NSEP]

LEAKED: USAF launches top secret satellite using Falcon Heavy!

 

[sevenperforce]

23 hours ago, PB666 said:

Hmm, looks like we have identified a flaw in the booster return program, you should right up a report and submit it to spaceX along with a bill.

BTW, the have more than enough thrust to land with two engines. The only problem is the LZ would need to be quite large, since the rocket will drift. You would have to start the burn sooner. However if the engine failed and the burnback program was not aware, or the failure was progressive, it probably would not have time to compensate.

It could just plop onto the LZ after zero fuel and a large 'popping' sound.

If there is anything that SpaceX has robustly programmed for, you better believe it's single-engine-out. I daresay the F9S1 has a specific routine for each engine-out at every possible point of the flight envelope.

I do not know whether the two edge return engines can fire without the center engine, though. So center-engine-out may FUBAR recovery. If not, then the landing might be two-engine, which we haven't seen.

On 12/18/2017 at 7:09 PM, PB666 said:

They have a nine-engine first stage, slightly before Max Q that is pretty much fail-proof because they can loose any engine and they have enough thrust from the remaining engines to complete the task. it would have to be something catastrophic, like the blowing up of a turbo pump. Of course the second stage could fail to fire, in which case it will fall back to earth.

There is a marginal utility of extending the life of the non-expendable version of the rocket at present, once you have recycled it 4 or 5 times you could pretty much write off the hull as its recycling value.

Engine-outs aren't a problem, even with RUD, because of the Octaweb. But the stage can still have structural failures.

I wonder -- if a major problem happened in the first few seconds after launch, is there a contingency to simply fly over to LZ-1 and land?

Edited December 20, 2017 by sevenperforce

[tater]

This is pretty interesting...

 

That's the fairing recovery ship.

Big net, perhaps?

[sevenperforce]

3 minutes ago, tater said:

This is pretty interesting...

 

That's the fairing recovery ship.

Big net, perhaps?

HOLY MOTHER OF

[CatastrophicFailure]

1 hour ago, sevenperforce said:

I wonder -- if a major problem happened in the first few seconds after launch, is there a contingency to simply fly over to LZ-1 and land?

Seriously doubt that. The rocket was never designed to land near its full weight like that, gear can’t take it, then you have the instability from having the loaded second stage on top (grid fins and thrusters are now too close to COM...).

[sevenperforce]

42 minutes ago, CatastrophicFailure said:

Seriously doubt that. The rocket was never designed to land near its full weight like that, gear can’t take it, then you have the instability from having the loaded second stage on top (grid fins and thrusters are now too close to COM...).

I dunno. With nine engines burning and a full fuel tank, the F9 should be able to hover for quite a while.

Though you're right; the landing legs would not be happy.

[CastleKSide]

Too bad its not KSP... stage early, fire up the 2nd, and then manover over and land