totm nov 2023 SpaceX Discussion Thread

[mikegarrison]

Turns out the forum server was so surprised the "catch" worked that it melted down.

Edited October 29 by mikegarrison

[Exoscientist]

Commercial
Starship Super Heavy booster came within one second of aborting first “catch” landing.
Jeff Foust
October 25, 2024
https://spacenews.com/starship-super-heavy-booster-came-within-one-second-of-aborting-first-catch-landing/ 

 This illuminates why I argue it’s likely SpaceX will ultimately decide to go with landing legs and landing on a landing pad anyway. Landing legs can be optimally designed to be lightweight to add only a small amount to the dry mass. Then it won’t be worth risking a launch tower worth hundreds of millions of dollars for such a small loss in payload. The loss of revenue from missed launches of the operational Starship over the months when the tower is being rebuilt can amount to billions in lost revenue. 

 Also it’s mentioned there wasn’t the expected amount of pressure in the Raptor. This could have been due to a fuel leak. Fuel leaks and the resulting fires have been a recurring problem with the Raptor:

What Happened to Starship SN11? | SpaceX Starship SN11 Test Flight & Explosion Cause Analysis.
https://youtube.com/clip/UgkxziHi2GsiVoF9v_DAa1YYQuU6fDskrWQU?si=qx0I7p_ussOY9bhT

 Then the giant plume of flame seen shooting up the side of the booster may in fact have been due to a fuel leak.

 Additionally, its mentioned one of the chine covers blew off exposing valves that are sources of single-point failure if they had been damaged. Notably the landing video shows the cover blew off before the engine restart began. It was speculated it was due to atmospheric forces, but it may have been due to a fire within the engine compartment releasing pressurized gas.

   Bob Clark

Edited October 29 by Exoscientist
Clarity

[.50calBMG]

We're back to fuel leaks again, and here I thought that had been proven not to be the case after the last 2 flights showed no indication of it. If you listen to the video, the engineer says they misconfigured the startup on the engines, not that it was a fuel leak. Also, with the chine cover, the engineer literally says in the video that it was aero forces, not a fire, and there are no scorch marks on the clearly visible copv and internal structure of the chine. 

You can't just say fuel leak every time something goes off nominal, especially when the people with all of the data say it's something entirely different. Raptor reliability is being proven before our very eyes, both on the test stands and during the flights, and they still haven't shown us any real footage of the further improved Raptor 3s putting in work either. 

As for the legs, do you really think having to restructure the booster to withstand further compression forces on landing rather than some tension, and that legs tough enough to survive a plasma sheath seconds before supporting a few hundred tons of booster will be lighter than a set of pins?

[Lukaszenko]

1 second to an abort? On a space rocket??? Sound engineering practice dictates that they should have at least 15 minutes of margin for anything on a space rocket! I can't even fathom the types of risks these people are taking. What kind of outfit are these clows running here?? /s  

[Exoscientist]

On 10/13/2024 at 3:27 PM, AckSed said:

I may be wrong about it being reentry heating, or only reentry heating: rewatching the ED stream, at 2 hours 30 minutes, when it's 38-32km up and moving 4330km/h, the glow of a fire spreads through the internal engine bay. This may just be trapped methane from engine chilldown.

 The glowing base on the booster during reentry prior to the landing burn has been described as reentry heating. But closer examination suggests fire in the engine compartment:

https://youtube.com/clip/UgkxfnFwF67GBwv4ItsloQPyL-XOTQSYz723?si=iOlffJRajEGCMDE8

This may have been due to the leaks that have been a recurring problem for the Raptor.

  Bob Clark

[Gargamel]

12 minutes ago, Lukaszenko said:

1 second to an abort? On a space rocket??? Sound engineering practice dictates that they should have at least 15 minutes of margin for anything on a space rocket! I can't even fathom the types of risks these people are taking. What kind of outfit are these clows running here?? /s  

Yeah, 1 second margin for a go/no go call by an automated system during a maneuver that is happening really fast is an eternity.   There was obviously a guy with their hand on the button, but once the flight director made the go call shortly after re-entry, it was completely automated.   

[.50calBMG]

2 hours ago, Exoscientist said:

 The glowing base on the booster during reentry prior to the landing burn has been described as reentry heating. But closer examination suggests fire in the engine compartment:

https://youtube.com/clip/UgkxfnFwF67GBwv4ItsloQPyL-XOTQSYz723?si=iOlffJRajEGCMDE8

This may have been due to the leaks that have been a recurring problem for the Raptor.

  Bob Clark

Or maybe it's the liquid oxygen/methane that they flow through the engines to thermally condition them that comes out of the engine bells... The famously flammable oxygen/methane that then gets compressed and superheated in the skirt when the booster comes back at near hypersonic speeds.

And the flame that came up the side of the booster during the landing burn was definitely a leak. It couldn't possibly be that it came from the liquid methane vent for the QD on the bottom of the booster where they vent the pressurized flammable gases from...

Seriously, you might as well point to an LNG flare stack and say that methane is just leaky and impossible to use.

Edited October 29 by .50calBMG

[magnemoe]

2 hours ago, .50calBMG said:

Or maybe it's the liquid oxygen/methane that they flow through the engines to thermally condition them that comes out of the engine bells... The famously flammable oxygen/methane that then gets compressed and superheated in the skirt when the booster comes back at near hypersonic speeds.

And the flame that came up the side of the booster during the landing burn was definitely a leak. It couldn't possibly be that it came from the liquid methane vent for the QD on the bottom of the booster where they vent the pressurized flammable gases from...

Seriously, you might as well point to an LNG flare stack and say that methane is just leaky and impossible to use.

Thought about this myself, they might bleed fuel and oxidizer to cool engines in case of an abort burn. the top engine in center ring did not have this so I assumed it was inactive. 
Or simply you did not want that lit for an abort burn who would either crash close by or kick it back into the sea. 

[tater]

Success.

[darthgently]

On 10/29/2024 at 12:25 PM, Gargamel said:

Yeah, 1 second margin for a go/no go call by an automated system during a maneuver that is happening really fast is an eternity.   There was obviously a guy with their hand on the button, but once the flight director made the go call shortly after re-entry, it was completely automated.   

Musk stated that 1 second is 50 control loop iterations, which is a looong time.   And coincidentally is about the same ballpark frequency of the physics frame in KSP on many machines

Edited October 30 by darthgently

[darthgently]

On 10/15/2024 at 3:00 PM, JoeSchmuckatelli said:

Much as I love the idea (and we've been over this ground before...) I don't see Asteroid Mining being profitable except for off-planet manufacturing.  Even if you brought back solid gold / diamond the cost per ton won't really shift the needle much on utility.

Sorry if I didn’t make it clear: this would be for developing the technology, R&D and such.   Under no circumstances other than practice, training, and testing would it make financial sense to wrangle a 20 meter rock

[tater]

 

Will Robinson Smith is the reporter... now I'm thinking about these two:

[mikegarrison]

41 minutes ago, tater said:

Will Robinson Smith is the reporter... now I'm thinking about these two:

Highly likely that whoever gave him that name was thinking about that too.

[darthgently]

42 minutes ago, tater said:

now I'm thinking about these two

Danger Will Robinson!  Move away from Dr. Smith!

[Flavio hc16]

On 10/29/2024 at 2:05 PM, Exoscientist said:

Commercial
Starship Super Heavy booster came within one second of aborting first “catch” landing.
Jeff Foust
October 25, 2024
https://spacenews.com/starship-super-heavy-booster-came-within-one-second-of-aborting-first-catch-landing/ 

Are you a programmer?

 

Because I'm and industrial programmer, and I can tell you that in "machine language", especially low level languages, 1 second is an eternity. We have machines that checks for errors in phisical objects that have total runtimes in the microseconds.

On 10/29/2024 at 2:05 PM, Exoscientist said:

 

 

[Exoscientist]

On 9/21/2024 at 3:02 PM, tater said:

Zubrin's ideas have been fairly useless for a long time, his "mini Starship" nonsense is more of the same, as SpaceX are going to do what they are going to do. He has a simple mechanism to put his money  (and presumably someone else's who has very deep pockets) where his mouth is, he could commission such a variant, then fly a test mission.

…

 I don’t agree with that. Note that SpaceX also wants to use his idea of using ISRU on Mars to generate the propellant for the return trip.

 Zubrin is just using standard spaceflight engineering practice that for high delta- v missions like to the Moon or Mars you use progressively smaller additional stages.  Instead of using additional stages, SpaceX wants to use that same single large size Starship to go all the way to the Moon or Mars. This requires multiple refuelings. Plus, because of its large amount of propellant the ISRU requirements on Mars become large also. Zubrin estimates 10 football fields worth of solar cells for the power to run the ISRU.

  Bob Clark

 

[Ultimate Steve]

You would need a LOT of hardware to do a manned Mars mission. Enough that SpaceX's plans back when they had the 12m ITS called for at least four ships during the window and a few presupply ships. The number is likely higher since the switch to smaller ships.

Granted some of that can be alleviated by not sending as many people, but you get diminishing returns for every person you remove. If you used mini starship you would have to have a much larger ship to person ratio than you would with a larger ship.

[tater]

51 minutes ago, Ultimate Steve said:

You would need a LOT of hardware to do a manned Mars mission. Enough that SpaceX's plans back when they had the 12m ITS called for at least four ships during the window and a few presupply ships. The number is likely higher since the switch to smaller ships.

Granted some of that can be alleviated by not sending as many people, but you get diminishing returns for every person you remove. If you used mini starship you would have to have a much larger ship to person ratio than you would with a larger ship.

At this point, I'd leverage Optimus and send bots ahead to build out infrastructure.

[Ultimate Steve]

2 minutes ago, tater said:

At this point, I'd leverage Optimus and send bots ahead to build out infrastructure.

I think robots of some sort to pre-emptively set up the solar farm is a good idea, but the idea of arriving to Mars only to be greeted by a field of dead humanoid robots in the sand probably isn't reassuring and probably isn't an image SpaceX would want to send. But maybe this is just be being too emotional and not technical enough. I generally don't think the human factors stuff gets talked about enough.

[AckSed]

A question for Exoscientist, because that alt. Shuttle brought it to mind: how would you design the payload bay doors of Starship?

Assume that, no matter what, the stretched version with heatshield will be built; I don't think SpaceX's course will be changed no matter the merit of an expendable version.

What shape would it be? Double door vs. single-door? Where would you put the hinge(s)?

I imagine the double-door with longitudinal split might retain some of the stiffness.

[tater]

1 hour ago, Ultimate Steve said:

I think robots of some sort to pre-emptively set up the solar farm is a good idea, but the idea of arriving to Mars only to be greeted by a field of dead humanoid robots in the sand probably isn't reassuring and probably isn't an image SpaceX would want to send. But maybe this is just be being too emotional and not technical enough. I generally don't think the human factors stuff gets talked about enough.

I think that building an environment where humans would want to live is profoundly difficult. That's ignoring the technical challenge of making "forever" life support. So we're on the same page. I would assume that any group aiming to stay would have a very detailed plan in advance. First live in ships, then use cargo to build the prefab habitats... the latter is where I see robots, both humanoid and vehicles versions (construction eqp). I see no reason why these robots cannot build the same prefab habs humans would build.

[Cuky]

 

[Exoscientist]

9 hours ago, AckSed said:

A question for Exoscientist, because that alt. Shuttle brought it to mind: how would you design the payload bay doors of Starship?

Assume that, no matter what, the stretched version with heatshield will be built; I don't think SpaceX's course will be changed no matter the merit of an expendable version.

What shape would it be? Double door vs. single-door? Where would you put the hinge(s)?

I imagine the double-door with longitudinal split might retain some of the stiffness.

 

 I haven’t seen the discussion on the best payload bay doors to use. Is there some reason why the SpaceX  “clamshell” version is non-optimal:

https://i.sstatic.net/D3MYv.png

  Bob Clark

[AckSed]

4 hours ago, Exoscientist said:

 I haven’t seen the discussion on the best payload bay doors to use. Is there some reason why the SpaceX  “clamshell” version is non-optimal:

https://i.sstatic.net/D3MYv.png

  Bob Clark

I am not an authoritative source.

I will say it again.

I am not an authoritative source. I have a third-class degree in Internet Computing that's 15 years out of date. I only know what I have read on the Internet, tasted and sniffed it to see if it's reasonably plausible, then regurgitated it to a small audience so I can be excited over it with like-minded people. That's why I'm here.

Asking whether it wouldn't or would work was secondary. I was trying to engage you, ask the opinion of a smarter person than I and maybe see if you had any insights, read any past research like from the Shuttle era. (And maybe head off any combatitiveness. Hate that stuff.)

[tater]

15 hours ago, AckSed said:

What shape would it be? Double door vs. single-door? Where would you put the hinge(s)?

Decades ago the Boeing "Big Onion" had this:

This maintains the inherent strength of the ring construction (with bracing, obviously). The downside of this type of bay door for SS would be that it separates through the heatshield. This seems to me to be the lowest mass option—but the heatshield issue is serious.

Any system they come up with will require substantial bracing to deal with loads on the vehicle during ascent and descent. It's doable, like everything else it will be a mass trade—large opening will eat into payload mass due to substantial bracing.