totm nov 2023 SpaceX Discussion Thread

[CatastrophicFailure]

55 minutes ago, Motokid600 said:

Its Mars I'm worried about.

First few Ships are one-way, loaded with (among other things) autonomous rovers to build marscrete pads for the two-way Ships. We already know concrete pads can stand up to Ship engines, and Mars would be less punishing. 

[magnemoe]

3 hours ago, tg626 said:

The Everglades would like a word.

That's why 39 is up on man made mounds. I can't fathom how one could plan to build a booster "Bigger than the Saturn 5" and not take the systems built for it (including the revisions after the first launch) and incorporate similar systems.

Ans the Starship pad is lifted above ground so no need for an mound. The issue is an lack of flame deflectors. 
Now having mounds and access ways was essential for shuttle and SLS as you are not lifting their full stack. 

[CBase]

So how is stage seperation actually supposed to happen ? Both regarding movement and release structure. I can't remember if some pictures showed the connections between SH and SS.

I have read something like a spin release, but that would indicate a substantial different stage connection than traditional decouplers.

[magnemoe]

1 minute ago, CBase said:

So how is stage seperation actually supposed to happen ? Both regarding movement and release structure. I can't remember if some pictures showed the connections between SH and SS.

I have read something like a spin release, but that would indicate a substantial different stage connection than traditional decouplers.

As I understand they start to rotate for boostback with SS still attached then release it. I guess to separate the two faster, but the separation did not work. Might be too much tension.
I assume superheavy hold the separation mechanism so they don't have to carry it to orbit and it could be an fail here to and an fail source in the future. 

[tater]

2 hours ago, AVaughan said:

I haven't done the maths, but wouldn't refuelling the lander in Lunar orbit (at/near gateway), then letting the fuel tanker aerobrake into Earth orbit, (or more likely re-enter directly from the Moon) be more fuel efficient than using fuel for the lunar lander to capture to LEO, especially given that under your proposal you need to land that fuel on the Moon, then launch it back into Lunar orbit?   Can't one stretched tanker make an LEO to Lunar Gateway trip with enough fuel in lunar orbit to refuel the lunar orbiter, and still have enough fuel to return to earth.  Possibly even with enough margin for a small cargo hold and some supplies/cargo.  And doesn't refuelling at Gateway allow the option of significantly heavier payloads to the Lunar surface?

If aerobraking is a thing, then yeah, they can do a few passes and not need the 3+ km/s to do EOI.

Bottom line is that there are multiple paths to a LEO to LEO mission profile via the lunar surface that don't need SLS/Orion.

Assuming they get this thing to orbit

 

[kerbiloid]

https://www.independent.co.uk/news/world/americas/spacex-starship-explosion-port-isabel-b2323858.html

Quote

Residents in Port Isabel, Texas, felt the effects of SpaceX's Starship following its highly publicised test launch and subsequent explosion, when sand dust coated the city.

That's a great name for SH: Vesuvius.

[KSK]

3 hours ago, JoeSchmuckatelli said:

Except for the fact that the Flight Report MUST OBSCURE the explosion for it to be KSP2 

Some architects use things like tracks in the grass to know where to put walkways... That theory seems applicable here. 

The best concrete is no concrete?

[Hannu2]

15 hours ago, steve9728 said:

Same thing happened with my gf. $3 billion firework is not something you can see everyday hahaha

Thank you Musk!

I asked my daughter did she see the launch (I knew no). She commented something like "boring" using the most annoying teenager style she could. I said that when largest ever built experimental rocket (about as tall as tallest buildings in Finland) lift off for first test flight it will never be boring event. It may be good or bad depending on your attitude or end result but always with very spectacular non boring way.

[Scotius]

It definitely wasn't boring!

I'd call it majestic.

Also, slightly terrifying while I expected a fireball at every second.

 Yet it flew, and flew for a good long time. As far as test flights go, this one was satisfying.

Congrats SpaceX

[steve9728]

As the saying, people usually don't have the same feeling of sorrows and joys on one thing. It's like some of the weird episodes of certain romance dramas my gf sometimes shares with me: she thinks it's interesting, but I can't get the logic no matter how I think about it.

However, we agreed on the point that the sky-high fireworks couple hours ago were interesting and very Kerbal after she watching me launch one and explode it similarly in KSP.

Edited April 21, 2023 by steve9728

[mikegarrison]

This launch did get me to fire up KSP for the first time in about, I would guess, a year? Something like that,

[Exoscientist]

What they’re discussing at SpaceX right now, “Ok, whose bright idea was it not to have a stage separation mechanism?”

 This article discusses the decision not to have a stage separation mechanism:

https://www.teslarati.com/spacex-starship-new-simplicity-extremes/

 An unfortunate decision because if the stages did separate there might not have been any need to send the destruct signal. Plus you would have gotten far more data by seeing what the Starship upper stage could do.
 

  Bob  Clark

 

[Terwin]

1 hour ago, steve9728 said:

As the saying, people usually don't have the same feeling of sorrows and joys on one thing. It's like some of the weird episodes of certain romance dramas my gf sometimes shares with me: she thinks it's interesting, but I can't get the logic no matter how I think about it.

Relationship dramas are very much a Pathos(emotional reasoning) thing.  

 

1 hour ago, steve9728 said:

However, we agreed on the point that the sky-high fireworks couple hours ago were interesting and very Kerbal after she watching I launch one and explode it similarly in KSP.

A lot of the most impressive parts of Rockets are dependent on Logos(logical reasoning), in part because the sizes and scales do not make a lot of emotional sense.

(a teaspoon and a 5 gallon bucket are easily recognizable sizes, a 5-kiloton rocket is much more abstract, and for the observers, the explosion took up less of the visual field than your average professional firework mortar, so you need a logical understanding of the scales for it to be appropriately impressive) 

[darthgently]

1 minute ago, Terwin said:

Relationship dramas are very much a Pathos(emotional reasoning) thing.  

 

A lot of the most impressive parts of Rockets are dependent on Logos(logical reasoning), in part because the sizes and scales do not make a lot of emotional sense.

(a teaspoon and a 5 gallon bucket are easily recognizable sizes, a 5-kiloton rocket is much more abstract, and for the observers, the explosion took up less of the visual field than your average professional firework mortar, so you need a logical understanding of the scales for it to be appropriately impressive) 

I think that the amount of concrete yeeted and how far it was yeeted is now a new measure of launch "power" that the average person could better relate to.

[magnemoe]

34 minutes ago, Exoscientist said:

What they’re discussing at SpaceX right now, “Ok, whose bright idea was it not to have a stage separation mechanism?”

 This article discusses the decision not to have a stage separation mechanism:

https://www.teslarati.com/spacex-starship-new-simplicity-extremes/

 An unfortunate decision because if the stages did separate there might not have been any need to send the destruct signal. Plus you would have gotten far more data by seeing what the Starship upper stage could do.

  Bob  Clark

They have an separation mechanism, as in latches holding the stages together.
That they plan on is not to have an need to use ullage with thrusters to settle propellant. 

Obviously the latches did not work, they could be under too much tension to physical disconnect, system could have broken or it could be an software issue. 

Now as I'm pretty sure this mechanism is on superheavy to avoid taking it to orbit, it might be issues that if superheavy dies for some reason starship could not separate, it can still use thruster for ullage. 
So moving it to SS or SS having an backup separation system make sense. 

[darthgently]

Hear me out.  Given the massive rate of boil off limits the launch window, how about a pair or more of smaller chopsticks that retract a split cylinder shell of insulation around the booster that pull away at t-60 or t-120 or so.

Either that or go with disposable panels that fall away Chinese style

[mikegarrison]

2 minutes ago, darthgently said:

or go with disposable panels that fall away Chinese style

That's an example of something that can't be done while still meeting the overall goals for the design. If you had to put all those insulation panels on the ship before fueling it, it would completely undermine the turnaround times that they are ultimately trying to achieve. 

[sevenperforce]

20 minutes ago, Exoscientist said:

What they’re discussing at SpaceX right now, “Ok, whose bright idea was it not to have a stage separation mechanism?”

 This article discusses the decision not to have a stage separation mechanism:

https://www.teslarati.com/spacex-starship-new-simplicity-extremes/

 An unfortunate decision because if the stages did separate there might not have been any need to send the destruct signal. Plus you would have gotten far more data by seeing what the Starship upper stage could do.

This article is almost two years old now and has obsolete information.

There is no pusher stage separation mechanism. There is, however, a separation mechanism -- latches holding the booster and the starship together. When it's time to separate, those latches open.

That article talks about a "small but significant" flick. Apparently it's much more than that:

Just before MECO, Superheavy gimbals hard left and places the entire stack into a flat spin, and the spin continues under full gimbal for almost 270 degrees before MECO and separation are commanded simultaneously. Once separation occurs, both vehicles continue to rotate and drift apart. Starship rotates for almost another 90 degrees before igniting its engines and straightening out, while Superheavy does another 270 degrees before starting the boostback. It's a really very aggressive maneuver.

1 hour ago, magnemoe said:

Obviously the latches did not work, they could be under too much tension to physical disconnect, system could have broken or it could be an software issue. 

My working theory is that due to thrust shortfall, the attempted separation happened lower in the atmosphere than planned, resulting in significant aerodynamic torque on the stack during the flat spin, which in turn placed too much shear force on the latches for them to open properly. Separation and MECO happen simultaneously, but MECO is not commanded until latch release is confirmed, and so in this case latch release never happened and so the booster kept pushing through the flat spin because it didn't know what else to do.

The other possibility is that the latches were just fine, but because of the higher drag, the rotation rate never got high enough for the computer to command separation at all.

[sevenperforce]

Holy crap. This does not look good.

Those pilings are 150 feet deep, but still -- that's absolute devastation.

[cubinator]

1 hour ago, magnemoe said:

They have an separation mechanism, as in latches holding the stages together.
That they plan on is not to have an need to use ullage with thrusters to settle propellant. 

Obviously the latches did not work, they could be under too much tension to physical disconnect, system could have broken or it could be an software issue. 

I have heard that the separation was not actually attempted because the vehicle was in such an off-nominal trajectory.

[Lukaszenko]

16 minutes ago, sevenperforce said:

This article is almost two years old now and has obsolete information.

There is no pusher stage separation mechanism. There is, however, a separation mechanism -- latches holding the booster and the starship together. When it's time to separate, those latches open.

That article talks about a "small but significant" flick. Apparently it's much more than that:

Just before MECO, Superheavy gimbals hard left and places the entire stack into a flat spin, and the spin continues under full gimbal for almost 270 degrees before MECO and separation are commanded simultaneously. Once separation occurs, both vehicles continue to rotate and drift apart. Starship rotates for almost another 90 degrees before igniting its engines and straightening out, while Superheavy does another 270 degrees before starting the boostback. It's a really very aggressive maneuver.

My working theory is that due to thrust shortfall, the attempted separation happened lower in the atmosphere than planned, resulting in significant aerodynamic torque on the stack during the flat spin, which in turn placed too much shear force on the latches for them to open properly. Separation and MECO happen simultaneously, but MECO is not commanded until latch release is confirmed, and so in this case latch release never happened and so the booster kept pushing through the flat spin because it didn't know what else to do.

The other possibility is that the latches were just fine, but because of the higher drag, the rotation rate never got high enough for the computer to command separation at all.

This is just absolutely insane. I would guess the whole thing would just brake apart even thinking about trying such a maneuver, especially so low in the atmosphere.

But then, I saw the thing do exactly those cartwheels with my own eyes (on livestream), and it indeed didn't break apart.

My guess would have been wrong.

[Vl3d]

31 minutes ago, sevenperforce said:

MECO is not commanded until latch release is confirmed, and so in this case latch release never happened and so the booster kept pushing through the flat spin because it didn't know what else to do.

That's a huge assumption.

[CBase]

@sevenperforce thank you for this great explanation

35 minutes ago, sevenperforce said:

It's a really very aggressive maneuver.

If this wasn't SpaceX, I would think anyone bringing up this manoveur as being completely nuts

35 minutes ago, sevenperforce said:

My working theory is that due to thrust shortfall, the attempted separation happened lower in the atmosphere than planned, resulting in significant aerodynamic torque on the stack during the flat spin, which in turn placed too much shear force on the latches for them to open properly.

Do you really think this would have been the case on all latches on all sides ? Visually there was no seperation happing at all.

21 minutes ago, cubinator said:

I have heard that the separation was not actually attempted because the vehicle was in such an off-nominal trajectory.

Might be true, but loosing the chance to see latches working if you can still trigger FTS afterwards ? I mean with a off-nominal trajectory it must have been clear to everbody already that they will have to.

43 minutes ago, sevenperforce said:

The other possibility is that the latches were just fine, but ...<for whatever measurement>...  the computer to command separation at all.

Sounds just likely.

[magnemoe]

58 minutes ago, sevenperforce said:

This article is almost two years old now and has obsolete information.

There is no pusher stage separation mechanism. There is, however, a separation mechanism -- latches holding the booster and the starship together. When it's time to separate, those latches open.

That article talks about a "small but significant" flick. Apparently it's much more than that:

Just before MECO, Superheavy gimbals hard left and places the entire stack into a flat spin, and the spin continues under full gimbal for almost 270 degrees before MECO and separation are commanded simultaneously. Once separation occurs, both vehicles continue to rotate and drift apart. Starship rotates for almost another 90 degrees before igniting its engines and straightening out, while Superheavy does another 270 degrees before starting the boostback. It's a really very aggressive maneuver.

My working theory is that due to thrust shortfall, the attempted separation happened lower in the atmosphere than planned, resulting in significant aerodynamic torque on the stack during the flat spin, which in turn placed too much shear force on the latches for them to open properly. Separation and MECO happen simultaneously, but MECO is not commanded until latch release is confirmed, and so in this case latch release never happened and so the booster kept pushing through the flat spin because it didn't know what else to do.

The other possibility is that the latches were just fine, but because of the higher drag, the rotation rate never got high enough for the computer to command separation at all.

As others say that is an very very nutty operation,  is lateral g forces an issue on payloads? 
Flip to 270 degree for engine cutoff and separation, followed by another 270 rotation before boost back. 
Makes me wonder if worth it because of gravity loss and ending up farther downrange. 

And agree that computer probably did not disconnect, who I say was an mistake as it would let them test Starship in flight even if they probably had to blow it up anyway. 
Had they had legs on it they could even have done an boostback burn and landing with SS. That is an unique option SS has, yes the shuttle had this to but much more limited. 

[darthgently]

49 minutes ago, Lukaszenko said:

This is just absolutely insane. I would guess the whole thing would just brake apart even thinking about trying such a maneuver, especially so low in the atmosphere.

But then, I saw the thing do exactly those cartwheels with my own eyes (on livestream), and it indeed didn't break apart.

My guess would have been wrong.

And, significantly, Unity take notes here, the craft did *not* squiggle about like a spaghetti noodle