totm nov 2023 SpaceX Discussion Thread

[Hotel26]

6 hours ago, Exoscientist said:

nytimes.com

There's your major malfunction...

Edited Monday at 10:36 PM by Hotel26

[tater]

Double header tonight, wonder if I will be able to see the VSFB one from here?

[tater]

VSFB NASA launch scrubbed.

[FleshJeb]

10 hours ago, Nuke said:

id also not rule out sabotage either

"Never attribute to malice that which is adequately explained by incompetence." --Hanlon's Razor

[Nuke]

2 hours ago, FleshJeb said:

"Never attribute to malice that which is adequately explained by incompetence." --Hanlon's Razor

i said i wouldnt rule it out, i didnt say it was likely. i can imagine that security at spacex is rather high.

[Meecrob]

On 3/9/2025 at 10:53 PM, darthgently said:

We mostly just watch him pwn himself these days

Good to know! Awesome launch the other day, can't wait to see what fixes are in store

15 hours ago, Exoscientist said:

p. SpaceX needs a true Chief Engineer making the engineering decisions

Sorry, I'm taken designing my cargo pods

[Hotel26]

5 hours ago, FleshJeb said:

"Never attribute to malice that which is adequately explained by incompetence."

I don't want to be "methodical" or anything, but once you've ruled out incompetence (or, at least, "failed to attribute it"), it is clear that Hanlon's Razor does not rule out other possibilities, yes?

You could, for example, apply a maxim from an investigative field, alternatively, and look for "means, Motive and opportunity".  But I think we are far from that yet...

Let's wait and see what facts and determinations are made, why don't we?

Edited 21 hours ago by Hotel26

[Lisias]

6 hours ago, FleshJeb said:

"Never attribute to malice that which is adequately explained by incompetence." --Hanlon's Razor

Once is an accident; twice, a coincidence; thrice is a conspiracy!

[darthgently]

SpaceX seems very certain it is a resonance issue in the new plumbing.  I’m thinking they probably have simulation or sensor data reasons for zeroing in on this.   [snip]

Edited 6 hours ago by Vanamonde
Avoid politics, please.

[darthgently]

Well played

 

[tater]

 

[Minmus Taster]

1 hour ago, darthgently said:

Well played

 

To be fair Saturn V wasn't reusable and was designed almost 60 years ago but they raise a good point, what exactly is the benefit of those downcomers though? They seem like they take up space and can easily fracture under strain.

[darthgently]

3 minutes ago, Minmus Taster said:

To be fair Saturn V wasn't reusable and was designed almost 60 years ago but they raise a good point, what exactly is the benefit of those downcomers though? They seem like they take up space and can easily fracture under strain.

I think they are supposed to better guarantee props flow under strange inertial conditions.  

I’m thinking that if they are going this route they need to have less symmetry in the plumbing so that none of the pipes has the same resonant frequency as any other so any resonance in isn’t amplified  back to it by the others.

This could perhaps be done by welding on various weights at various points along the pipes without much added weight.

 I’m just having armchair fun and am not being critical nor think I have any real answers

[zolotiyeruki]

If you're looking to shift the resonant frequencies of the downcomers, it'd probably be lighter to change the stiffness rather than the weight.

[tater]

 

[darthgently]

18 minutes ago, zolotiyeruki said:

If you're looking to shift the resonant frequencies of the downcomers, it'd probably be lighter to change the stiffness rather than the weight.

Sure, like tightening and loosening guitar strings. Makes sense.

 Tune them such that none of the resonant freqs has a common factor with any other perhaps

Edited 16 hours ago by darthgently

[tater]

Testing this will of course be difficult, has to be simulated because the problem is at a low propellant state (mass), hence at high g.

I guess they should build  test rig/vehicle that somehow mimics 4 g—that's the only way! Even if such a rig requires 10 years and 10s of billions of $, that would clearly make more sense than throwing away a few tens of millions of $ on a Starship over the Gulf!

Edited 15 hours ago by tater

[Exoscientist]

 The suggestion that a Moon landing can be mounted with a launcher at ca. 60 ton payload capacity is derived from a proposal from the early 1990's  for a low cost follow-up to Apollo called Early Lunar Access(ELA):

Moon denied: the 1993 Early Lunar Access proposal.
by Dwayne A. Day
Monday, January 9, 2023

https://www.thespacereview.com/article/4511/1

 It would use a Gemini-sized capsule for a 2-person crew lunar mission at ca. 3 tons dry mass for the capsule. Studies had shown the Gemini capsule could be adapted to carry a crew of two for a lunar mission. Unlike, Apollo there would be only this one crew module that would go all the way to the surface of the Moon and back to Earth, in contrast to the Apollo architecture that had a second smaller, crew module for the lunar lander.

 Interestingly, the hydrolox lunar lander stage would have about the same gross mass as the fully fueled Blue Moon MK1 lander with a 3 ton dry mass crew capsule added, i.e., ca. 25 tons.

The plan was to use only one other additional in-space stage, a Centaur-like stage to perform the translunar injection(TLI) burn. This stage and the lander stage would be launched separately and link up in low Earth orbit. A spaceflight rule-of-thumb is a hydrolox Centaur-like stage can get a payload mass of equal size to its prop load mass to TLI. So a hydrolox stage would be needed at 25 tons or more prop mass. Centaur itself did exist at ca. 20 tons but a slightly larger one would be needed. The ELA plan was proposed in 1993, perhaps they were thinking of an extended Centaur. In any case, a hydrolox stage of the needed size did come into play with the Delta IV Heavy's upper stage, first launched in 2004.

 Besides that problem, the plan was to have the 25 ton hydrolox lander launched on the Space Shuttle. The shuttle then would need its payload capability expanded slightly to 25 tons. Another issue is NASA for safety reasons did not want a hydrolox stage in the shuttle payload bay.

 For these reasons the plan did not progress beyond just the proposal stage. But now we do have a hydrolox upper stage in the DIVH upper stage of the needed size to do the TLI burn. And we do have a launcher at 60+ ton capacity in the Falcon Heavy. The Falcon Heavy would need to be man-rated or Falcon 9 would need to be launched separately to get the crew to orbit.

 The New Glenn at 45 ton payload capability as partially reusable likely could also get ca. 60 tons to orbit expendable.

Edited 8 hours ago by Exoscientist
Clarity

[darthgently]

2 hours ago, tater said:

Testing this will of course be difficult, has to be simulated because the problem is at a low propellant state (mass), hence at high g.

I guess they should build  test rig/vehicle that somehow mimics 4 g—that's the only way! Even if such a rig requires 10 years and 10s of billions of $, that would clearly make more sense than throwing away a few tens of millions of $ on a Starship over the Gulf!

Yep.  Sometimes the cheapest simulation is the real world.  Very often actually

[Vanamonde]

Avoid politics, please. Some commented removed. 

[tater]

 

[tater]