totm nov 2023 SpaceX Discussion Thread

[JoeSchmuckatelli]

31 minutes ago, tater said:

SN20 is supposedly the first orbital flight article SS.

Musk said July 1 as an aspirational launch date (51 days from now, not 416 days from now, lol). Seems unlikely, but later in the summer?

Do you think they would try for a controlled reentry and landing with that?  I'm trying to picture where they might reasonably attempt a landing, and the only thing I can come up with is 'they might try the landing sequence over water, knowing they're ditching the craft - but just to practice / gather data'.

[sevenperforce]

On 5/8/2021 at 11:22 PM, tater said:

The assumption is hot gas rcs for starship.

**have been waiting for this**

What a lovely sound.

23 hours ago, StrandedonEarth said:

Thanks!

Oh yeah, and HUZZAH! for number 10!

See, these F9 launches and landings all the time are starting to get routine and boring, which is a good thing, really. Which is why the Starship program is going, to keep things spicy. Hopefully, SS/SH ops will become routine and boring in five more years. But the spicy must flow, in the form of Mun, Duna, Moon, Mars, and asteroid ops.

They said it couldn't be done.

Ten flights for a single booster.

Just incredible.

21 hours ago, magnemoe said:

On 5/8/2021 at 5:08 PM, RCgothic said:

We think that in order to go from up to belly down in a controlled manner a kick from the raptors is required. Therefore they can't just coast to apogee, which means they have to keep the speed down so as not to exceed the altitude limit.

Now this makes some sense, yes they could restart at AP,  but if under trust they have more control, and yes I get why they don't want to go supersonic. 

If they cut the engines entirely and tried to coast to apogee at any significant speed, the whole stage would probably start to tumble. Probably end up inverted with the heavy engines pointing skyward.

[tater]

1 hour ago, sevenperforce said:

Ten flights for a single booster.

Since that booster flew its first mission, it has flown 90.9% as many missions as ULA has flown in the same time frame (10 vs 11 flights).

Edited May 10, 2021 by tater

[Flavio hc16]

5 minutes ago, tater said:

Since that booster flew its first mission, it has flown 90.9% as many missions as ULA has flown in the same time frame (10 vs 11 flights).

"But but but but reusing rockets is useless"

[Xd the great]

15 hours ago, tater said:

SN20 is supposedly the first orbital flight article SS.

Musk said July 1 as an aspirational launch date (51 days from now, not 416 days from now, lol). Seems unlikely, but later in the summer?

Would it be wise to do a BN3 test fire/launch without SN20 on top?

[Beccab]

49 minutes ago, Xd the great said:

Would it be wise to do a BN3 test fire/launch without SN20 on top?

It would be possibile, but it would also delay the orbital flight for not very useful data (everything they would get from the hop they would very likely get from the orbital flight)

[Xd the great]

Just now, Beccab said:

It would be possibile, but it would also delay the orbital flight for not very useful data (everything they would get from the hop they would very likely get from the orbital flight)

I mean, you need to test the vibration/acoustic loads of 31(?) raptors firing, as well as the different control software of landing a bigger booster. Might be a better idea to not risk a Starship prototype in case of BN3 going RUD.

[tseitsei89]

23 minutes ago, Xd the great said:

I mean, you need to test the vibration/acoustic loads of 31(?) raptors firing, as well as the different control software of landing a bigger booster. Might be a better idea to not risk a Starship prototype in case of BN3 going RUD.

Vibrations are probably different with and without starship on top of the booster so it is better to test with starship. They have a very good idea how to land boosters since they already have a great software for F9 (superheavy is really similar in landing) so software is probably least of their worries. Plus they seem to be producing starship prototypes faster than they can actually fly them so exploding one wouldnt really hurt all that much

 

[Beccab]

27 minutes ago, Xd the great said:

I mean, you need to test the vibration/acoustic loads of 31(?) raptors firing, as well as the different control software of landing a bigger booster. Might be a better idea to not risk a Starship prototype in case of BN3 going RUD.

That's true, but the first one can probably be adequately tested with one (or probably, more than one bc raptors swap) static fire and the landing will be attempted without a starship on the top either case, no matter if it started with or without one 

[magnemoe]

14 minutes ago, tseitsei89 said:

Vibrations are probably different with and without starship on top of the booster so it is better to test with starship. They have a very good idea how to land boosters since they already have a great software for F9 (superheavy is really similar in landing) so software is probably least of their worries. Plus they seem to be producing starship prototypes faster than they can actually fly them so exploding one wouldnt really hurt all that much

 

Yes, they will definitely do multiple static fires with superheavy. But launching it alone will add other issues you don't get with SS on top so its probably just as well to do the real thing. 

[mikegarrison]

16 hours ago, Flavio hc16 said:

"But but but but reusing rockets is useless"

I think the key is actually the Starlink. SpaceX is making all these launches for mostly an internal customer. There is good synergy there -- they have a business where they need to make a *lot* of launches, and they have a rocket that needs a lot of launches to pay off the investment in making it reusable.

If they didn't have this endless number of Starlink launches, they wouldn't be making up on volume what it presumably cost to develop the capability.

Of course, whether that's all good for the business in the end depends on whether Starlink can make back the money for all the launches.

[RCgothic]

I would expect BN3 to be static fired without SN20, but flown with. If BN3 RUDs then the next test needs to wait for BN4 anyway, by which time SN21 will probably be ready. So it won't matter too much if SN20 was on top of BN3 or not. But if SN20 is up top, they get more data.

[SunlitZelkova]

19 hours ago, tater said:

SN20 is supposedly the first orbital flight article SS.

Musk said July 1 as an aspirational launch date (51 days from now, not 416 days from now, lol). Seems unlikely, but later in the summer?

I hope it happens sometime in July. My b-day is the 22nd, orbital launch would make a lovely treat.

[Kerwood Floyd]

Did I miss something? It seems to me that SpaceX need to keep doing the SS 10k hops until they figure out what's up with the fires inside the skirt after landing.

[tater]

1 minute ago, Kerwood Floyd said:

Did I miss something? It seems to me that SpaceX need to keep doing the SS 10k hops until they figure out what's up with the fires inside the skirt after landing.

Well, if something got knocked loose, for the first time they have one to look at to see what it was.

[Beccab]

7 minutes ago, Kerwood Floyd said:

It seems to me that SpaceX need to keep doing the SS 10k hops until they figure out what's up with the fires inside the skirt after landing.

They already know what's up with the fire afaik, it's just what happens when the engines turning off. Rocket engines are turned off by stopping to send oxidizer to them, which means the engine stops and the thrust ceases. That has the possible side effect of a little methane continuing to come out of engine, which can ignite and cause the fire post landing

Edited May 11, 2021 by Beccab

[magnemoe]

4 hours ago, mikegarrison said:

I think the key is actually the Starlink. SpaceX is making all these launches for mostly an internal customer. There is good synergy there -- they have a business where they need to make a *lot* of launches, and they have a rocket that needs a lot of launches to pay off the investment in making it reusable.

If they didn't have this endless number of Starlink launches, they wouldn't be making up on volume what it presumably cost to develop the capability.

Of course, whether that's all good for the business in the end depends on whether Starlink can make back the money for all the launches.

I read the ULA reuse is to expensive as true for ULA. their problem is that they has to design and build an entirely new rocket to reuse the first stage. 
SpaceX was lucky with their Falcon 9, as it was pretty easy to set up for reuse.  9 engines with an center one and as one vacuum version is used in the upper stage is was created to be restarted, their testing strategy also involves multiple test burns so engines was kind of designed for reuse from the start. 
And they could develop reuse on the cheap testing on stages after they was used for paid missions. 

[zolotiyeruki]

15 minutes ago, magnemoe said:

I read the ULA reuse is to expensive as true for ULA. their problem is that they has to design and build an entirely new rocket to reuse the first stage. 
SpaceX was lucky with their Falcon 9, as it was pretty easy to set up for reuse.  9 engines with an center one and as one vacuum version is used in the upper stage is was created to be restarted, their testing strategy also involves multiple test burns so engines was kind of designed for reuse from the start. 
And they could develop reuse on the cheap testing on stages after they was used for paid missions. 

You're right that ULA would likely have to do a whole bunch of redesign in order to recover their boosters, but I wouldn't call SpaceX "lucky."  Reusability was a primary goal from Day 1 for Falcon, and a whole lot of engineering (and money, and explosions) went into making that happen.  As a disposable launch vehicle, F9 has been pretty doggone reliable from the beginning. 

[tater]

 

[SpaceFace545]

9 minutes ago, zolotiyeruki said:

You're right that ULA would likely have to do a whole bunch of redesign in order to recover their boosters, but I wouldn't call SpaceX "lucky."  Reusability was a primary goal from Day 1 for Falcon, and a whole lot of engineering (and money, and explosions) went into making that happen.  As a disposable launch vehicle, F9 has been pretty doggone reliable from the beginning. 

I think SMART reuse is a great choice for ULA to pursue in the future. ULA really doesn't need to focus on recoverability as they focus on DOD and NASA missions and those people could really care less about launch costs and more about launch vehicle capabilities. And ULA really is much better at the specific orbits necessary for interplanetary probes and spy satellites. On the other hand SpaceX focuses in the private sector where recoverability brings their launch costs down so it is easier for private companies to launch their satellites.

[tater]

29 minutes ago, SpaceFace545 said:

I think SMART reuse is a great choice for ULA to pursue in the future. ULA really doesn't need to focus on recoverability as they focus on DOD and NASA missions and those people could really care less about launch costs and more about launch vehicle capabilities. And ULA really is much better at the specific orbits necessary for interplanetary probes and spy satellites. On the other hand SpaceX focuses in the private sector where recoverability brings their launch costs down so it is easier for private companies to launch their satellites.

SpaceX has won most (all?) of the recent NASA contracts.

ULA got 60% of the AF contracts in that last round (for Vulcan of all things).

Until Amazon bought 9 Atlas V launches, I think the last commercial launch by ULA was what, 2016?

Right now the only really good thing ULA has is Centaur—which is a decent thing to have, Centaur is arguably the best rocket stage, ever. It's too ULA has the parents it has, they clearly have really good people there (they had all kinds of evolved Atlas ideas, ACES, cislunar, etc, but crippled by the "this can be yours for just $XB" requirements of having shareholders to have to satisfy. It;s like when the former Boeing CEO said they'd beat SpaceX to Mars with humans, and Musk said, "Do it". ULA can't dev something without a customer in place, then offer it (sadly).

[SpaceFace545]

2 minutes ago, tater said:

SpaceX has won most (all?) of the recent NASA contracts.

ULA got 60% of the AF contracts in that last round (for Vulcan of all things).

Until Amazon bought 9 Atlas V launches, I think the last commercial launch by ULA was what, 2016?

Right now the only really good thing ULA has is Centaur—which is a decent thing to have, Centaur is arguably the best rocket stage, ever. It's too ULA has the parents it has, they clearly have really good people there (they had all kinds of evolved Atlas ideas, ACES, cislunar, etc, but crippled by the "this can be yours for just $XB" requirements of having shareholders to have to satisfy. It;s like when the former Boeing CEO said they'd beat SpaceX to Mars with humans, and Musk said, "Do it". ULA can't dev something without a customer in place, then offer it (sadly).

Okay? I don’t really know if your trying to start a debate or just giving me a bunch of statistics?

[wumpus]

48 minutes ago, zolotiyeruki said:

You're right that ULA would likely have to do a whole bunch of redesign in order to recover their boosters, but I wouldn't call SpaceX "lucky."  Reusability was a primary goal from Day 1 for Falcon, and a whole lot of engineering (and money, and explosions) went into making that happen.  As a disposable launch vehicle, F9 has been pretty doggone reliable from the beginning. 

That's mostly true, but the merlin engine was designed for Falcon [1], which they never really attempted to recover.  Future plans for both Falcon [1] and Falcon 9 were based around parachutes.  Oddly enough, the merlin engine doesn't appear to have had issues lighting while falling with air blasting into  the nozzle  while the raptor engine (which was designed with retropropulsion in mind) has crashed a few times thanks to failing to ignite while falling.

Granted, we don't know what "plan C" was for recovering the rocket, and if it would work.

Don't forget, "plan A" not only failed for recovering boosters (parachutes), it also failed for fairing recovery (catching it in nets).  Plan B (fishing it out of the water) is working well enough that plan A was scrapped.

So while you might claim that Spacex was "lucky" that merlins have a property that was never a design goal, recovery appears to be more due to a dogged insistence of solving the problem than pure luck.  The original recovery plans wouldn't work (although presumably merlins *were* designed for long enough working life for reuse), and they simply kept at it.  You shouldn't be surprised if some parts are eventually found to have the properties needed to solve the problem in *some* way (if not the original plan, i.e. parachutes).

[tater]

1 minute ago, SpaceFace545 said:

Okay? I don’t really know if your trying to start a debate or just giving me a bunch of statistics?

I'm saying you're right WRT them not seeking commercial success (Amazon sat launch buy was a bone thrown by BO since NG will absolutely cannibalize Vulcan's market), and instead get AF contracts.

I like ULA, but they need to be given some ability to innovate by LockMart/Boeing, IMO.

SMART reuse might be a thing, but I'm not sure how it pays off. We know Be-4 engines are under $7M/ea (per Bruno math on launch costs). So while $14M is a good savings, you have to wonder how much effort has to go into grabbing them, then re-mounting them. I assume that Bruno's internal math is that it pays off after 10 flights (since that's where he thinks F9 reuse paid off (I'd bet it's far fewer flights)). So they make a few million more per launch.

[SpaceFace545]

What’s the minimum amount of raptors needed on superheavy to lift the whole starship stack?

Edited May 11, 2021 by SpaceFace545