totm nov 2023 SpaceX Discussion Thread

[RCgothic]

My puzzle is that an engine would need to run LOX rich for quite a while to fall catastrophically. Surely they could just... turn the engine off? Which begs the question why didn't they?

Also whilst it's probably worth trying, low lox levels in the tank for a static fire probably wouldn't be sufficient to replicate the long duration and high G environment that may be causing harmonic vibration issues in flight in the ground.

[GuessingEveryDay]

Crew-10 delayed

[darthgently]

3 hours ago, RCgothic said:

 

My puzzle is that an engine would need to run LOX rich for quite a while to fall catastrophically. Surely they could just... turn the engine off? Which begs the question why didn't they?

 

The remaining engines not shutting off really is a puzzler.  But that assumes the software has a totally clear idea of what was happening back in the engine bay.  If it assumed some vectoring engines were still operating the goal may have been to regain attitude, keep chugging, and get the debris field out into the mid Atlantic instead of in the islands.

 It broke one of my KSP rules:  never thrust in the wrong direction.  My kOS scripts typically taper the throttle as attitude error goes up as a safety net.  No throttle, or just enough for vectoring steerage, if error is greater than 20 degrees or so on ascent.  This code typically only kicks in when I’m doing something new but it allows me to keep playing and testing for awhile rather than crashing and starting over.  Anyway, the point is that I’m not sure why they didn’t shut the remaining engines off, or at least throttle them down when pointed in the wrong direction.  They may have made it well past the islands, even doing endos, if they only throttled up when pointed down range with a positive pitch and tapered throttle down when not.  And maybe the engines were on for an reason but the software was confused about the attitude and available control authority

[tater]

 

[Exoscientist]

 
 Repeated engineering failures stem from the top. What SpaceX needs to do first is hire a true  Chief Engineer. Then follow standard industry practice of doing full-up(all engines), full mission duration, full thrust static tests.

  Bob Clark

[AckSed]

What is a true Chief Engineer?

Do they have aerospace experience?

Are they a respected expert in their field?

Do they have at least ten years of working at a rocket company?

Are they experienced with a high-pressure environment as they work with a team to push boundaries?

And are they also sensible and know when not to push the boundaries?

[Hotel26]

"The definition of insanity is doing the same thing over and over again and expecting different results",  Albert Einstein

[Lisias]

4 hours ago, AckSed said:

What is a true Chief Engineer?

Do they have aerospace experience?

Are they a respected expert in their field?

Do they have at least ten years of working at a rocket company?

Are they experienced with a high-pressure environment as they work with a team to push boundaries?

And are they also sensible and know when not to push the boundaries?

Are you saying that SpaceX put thousands of StarLink satellites in orbit, is launching resupply missions to ISS and created the first fully reusable 1st stage rocket (Falcon 9) without one?

[Hotel26]

Definition: "a true Chief Engineer has a pocket protector and is never seen without his slide rule."

[darthgently]

2 hours ago, Lisias said:

Are you saying that SpaceX put thousands of StarLink satellites in orbit, is launching resupply missions to ISS and created the first fully reusable 1st stage rocket (Falcon 9) without one?

I read it as meaning they couldn’t have done it without one.

[AckSed]

Nuance: I was trying to reframe the question but tired 3AM thinking turned it into a CV of what an imagined Chief Engineer 'should' be.

[Deddly]

5 hours ago, Hotel26 said:

"The definition of insanity is doing the same thing over and over again and expecting different results",  Albert Einstein

I thought that was the definition of KSP.

[Exoscientist]

5 hours ago, Lisias said:

Are you saying that SpaceX put thousands of StarLink satellites in orbit, is launching resupply missions to ISS and created the first fully reusable 1st stage rocket (Falcon 9) without one?

 

 6 out of 8 explosions of your rocket in flight is indicative of bad engineering. Making the same mistake again after your vehicle explodes causing it to explode twice in a row is indicative of bad engineering. For any other space company such poor engineering would result in severe questioning of the Chief Engineer.

 Unfortunately for SpaceX, the Chief Engineer is the owner of the company. Questioning him results in YOU being the one getting fired.

  Bob Clark

[.50calBMG]

That "poor chief engineer" must be the same reason they are:

1 utterly dominating the world launch market with a vehicle that "true experts" said would be impossible for years right up until it worked,

2 developing the world's first fully reusable rocket with a meaningful payload far faster and for a fraction of the cost of any other program,

3 putting into service the world's first LEO communications network,

4 the only American company that can send astronauts to orbit and actually bring them home.

[snip] We get that you don't like him, but you cannot reasonably expect someone who has had this much impact and caused more than one paradigm shift in spaceflight to actually be incompetent.

Edited 4 minutes ago by Vanamonde

[grawl]

36 minutes ago, Exoscientist said:

indicative of bad engineering

I don't think so. It's more of an inherent symptom of the "move fast & break things" moto. In the same time, other companies not embracing this way of doing (BO I'm looking at you !) have yet to repeat a successful launch.

BO launch might look more polished as nothing RUDed, but SpaceX definitely has way more expertise on the reusability side of a very big first stage, And don't forget that, at some point, they DID make a perfectly controlled Starship re-entry and landing.

Only time will tell which of the 2 approaches will get to full success first.

[Terwin]

Unless and until there is a loss of paid cargo or a loss of life, starship failures are just a development cost, and entirely reasonable. 

They may have known that there was a  >50% chance of the problem happening again, but this time with better instrumentation to better pin down the cause and that would be a perfectly reasonable test scenario, especially if it is the cheapest way to get that data.

Until there is a paid cargo onboard, they are expecting vehicle failures, so vehicle failures are not program failures.

[Hotel26]

I did not know this: SpaceX was founded in 2002 by the current CEO.  I did not realize that this company had operated this long in such a difficult field.

Twenty three years (this week!) and under one management.  Outstanding!!

Edited 5 hours ago by Hotel26

[Lisias]

1 hour ago, Exoscientist said:

For any other space company such poor engineering would result in severe questioning of the Chief Engineer.

It's a bit hard to fire the guy that built the Starship Booster, that huge building sized thingy that lands on a pair of mecha chopsticks.

Every single professional on Technology tends to be promoted until reaching their level of incompetence - unless they die first. Every single one of us is doomed to this destiny, it's almost as inescapable as taxes.

So, it's not impossible that the current Chief Enginner had finally reached that point.

However, we are still talking about the guy that built that chopstics landing flying building, aren't we?

[darthgently]

45 minutes ago, Hotel26 said:

I did not know this: SpaceX was founded in 2002 by the current CEO.  I did not realize that this company had operated this long in such a difficult field.

Twenty three years (this week!) and under one management.  Outstanding!!

Exactly.  This longevity has to put them in the top 1% of space startups even ignoring all the other firsts they’ve achieved.  But don’t you dare believe your lying eyes!  Oh no!  That would be incorrect.  /sarcasm

[Exoscientist]

250 Tonnes to Orbit!?: SpaceX's New Expendable Starship Option.
https://m.youtube.com/watch?v=UutHG8Y2UuQ

 Elon has spoken of a flaw in engineering design of “doubling down on a bad design”. He is committing that error with the Starship. Requiring that the Starship must be fully reusable before it is operational was a bad design choice from the start. The Falcon 9 was spectacularly successful by first aiming for an expendable rocket, then proceeding to reusability. 

 However, Elon wants the Starship to be fully reusable first. This is becoming increasingly difficult. If you think about it, it is this requirement that is a major cause of the difficulties. The need for reusability of Starship drastically increased its dry mass. Elon once estimated its dry mass as low as 40 tons as expendable. Now requiring it to be reusable at least quadruples that dry mass to 160 tons or likely even more.

 That radical increase in dry mass requires to make the Starship larger to get their desired payload. But then heavier mass already means more difficult thermal protection. And in fact the one they had used for several test flights had to be abandoned. At this point they don’t even know what thermal protection they’ll use. They don’t even know if they’ll even be able to find one that works at sufficient light weight that at the same time allows rapid reuse.

 SpaceX had stunning success in developing the Falcon 9 yet they chose to ignore that success. If they had followed that model they would already be flying the Starship as expendable at a profit.

We would already have an operational rocket capable of both Moon and Mars missions NOW.

   Bob Clark

 

 

[Nuke]

i see this as more of a temporary setback. if booster can do its mission with its ungodly huge engine array i dont see why starship cant do the same with six. the less complex design should be simpler and less prone to failure. at least the problem has been firmly pinned down this time. in retrospect it seems if you want more fire suppression and vent capacity, you probibly should figure out whats burning, how it got that way and how to prevent it from happening again. they addressed the issue too far down the failure chain and need to go back a few links. now that we know the next step is doing something different (hopefully something less failure prone).

[magnemoe]

34 minutes ago, Nuke said:

i see this as more of a temporary setback. if booster can do its mission with its ungodly huge engine array i dont see why starship cant do the same with six. the less complex design should be simpler and less prone to failure. at least the problem has been firmly pinned down this time. in retrospect it seems if you want more fire suppression and vent capacity, you probibly should figure out whats burning, how it got that way and how to prevent it from happening again. they addressed the issue too far down the failure chain and need to go back a few links. now that we know the next step is doing something different (hopefully something less failure prone).

Agree with you, the three extra feed lines is likely the issue. We know they want to add 3 more vacuum engines and 7 feed lines feels to much but they are more experienced than me who only made an starship in KSP for the special asteroid mission. 
 

[Cuky]

3 hours ago, Exoscientist said:

250 Tonnes to Orbit!?: SpaceX's New Expendable Starship Option.
https://m.youtube.com/watch?v=UutHG8Y2UuQ

 Elon has spoken of a flaw in engineering design of “doubling down on a bad design”. He is committing that error with the Starship. Requiring that the Starship must be fully reusable before it is operational was a bad design choice from the start. The Falcon 9 was spectacularly successful by first aiming for an expendable rocket, then proceeding to reusability. 

 However, Elon wants the Starship to be fully reusable first. This is becoming increasingly difficult. If you think about it, it is this requirement that is a major cause of the difficulties. The need for reusability of Starship drastically increased its dry mass. Elon once estimated its dry mass as low as 40 tons as expendable. Now requiring it to be reusable at least quadruples that dry mass to 160 tons or likely even more.

 That radical increase in dry mass requires to make the Starship larger to get their desired payload. But then heavier mass already means more difficult thermal protection. And in fact the one they had used for several test flights had to be abandoned. At this point they don’t even know what thermal protection they’ll use. They don’t even know if they’ll even be able to find one that works at sufficient light weight that at the same time allows rapid reuse.

 SpaceX had stunning success in developing the Falcon 9 yet they chose to ignore that success. If they had followed that model they would already be flying the Starship as expendable at a profit.

We would already have an operational rocket capable of both Moon and Mars missions NOW.

   Bob Clark

 

 

Just because you are repeating that same thing every few pages in this thread doesn't make it correct. SpaceX wants reausable rocket to have higher profits because they can launch it often and multiple times without need to builed a new one. They are still making revenue from Falcon 9 and Falcon Heavy launches and Starlink and investing that into R&D for Starship/Superheavy. They don't have to follow the same route they took with Falcon 9. When they made Falcon 9 they didn't have any revenue source. So they needed a rocket that could bring them in much needed cash they need to develop a reusable rocket. Now they don't need to waste time makin a disposable rocket when they have revenue from Falcon 9 lauches and they can from a get go do whatever they can afford.

And what good would it be to have an operational rocket when it would cost a lot to fly? The whole point of developing Starship/Superheavy is to reduce launch cost as much as possible. You don't get that by discarding it after a single use.

[darthgently]

2 hours ago, Nuke said:

i see this as more of a temporary setback. if booster can do its mission with its ungodly huge engine array i dont see why starship cant do the same with six. the less complex design should be simpler and less prone to failure. at least the problem has been firmly pinned down this time. in retrospect it seems if you want more fire suppression and vent capacity, you probibly should figure out whats burning, how it got that way and how to prevent it from happening again. they addressed the issue too far down the failure chain and need to go back a few links. now that we know the next step is doing something different (hopefully something less failure prone).

I’m wondering if they lost or obscured the source of the fire because of the extent of the fire and the additional suppression may be a partially to be able to see the problem better.  I dunno.  

1 hour ago, magnemoe said:

Agree with you, the three extra feed lines is likely the issue. We know they want to add 3 more vacuum engines and 7 feed lines feels to much but they are more experienced than me who only made an starship in KSP for the special asteroid mission. 
 

Too exact a symmetry in the new plumbing could really exacerbate a resonance issue.  A cylindrical vehicle with the curved walls and common centerline doesn’t help and can amplify resonances also, but that is somewhat unavoidable.   Break the plumbing symmetry wrt resonance perhaps

[Vanamonde]

Disagreement is fine but please do not accuse each other of trolling. Some comments removed.