totm nov 2023 SpaceX Discussion Thread

[darthgently]

  On 8/6/2024 at 12:31 PM, Exoscientist said:

 

 I didn't say he was wrong, only that we couldn't know if he was knowledgeable in the area. But we can see that he was being disingenuous in implying the difference was sizable. The difference is relatively small so the conclusions still hold.

  Bob Clark

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You are just telling me you don't understand why an Appeal to Authority is a logical fallacy.

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Given previous fumbles, I don't trust your take on either the definition of "relatively small" or your ability to judge in an unbiased manner whether the conclusions hold.  And given the validly noted errors in the paper I don't trust, on the surface, their conclusions.  As they have demonstrated a lack of care

One thing that stands out is their high guesstimated 200m/s DV for TCM seems a bit baseless given that corrections early on are typically quite inexpensive and accuracy of landing position will be largely aerodynamically determined during capture and possible subsequent aero passes.

Another that stands out is that after capture they assume subsequent lowering of apoapsis will not be via repeated aero passes, which is an option at both Mars and Earth.  Each of those passes would use aero forces to fine tune eventual landing position. 

Mostly, while the authors start out by correctly stating that much still needs to be figured out, they then go on to assert that things that haven't been figured out yet won't work.  I'm not sure how one evaluates in detail what hasn't been figured out, but that doesn't slow them down. 

I'm not certain, of course, but it looks to me like they are overestimating the payloads both to, and from, Mars, which would obviously tilt the fuel and lox requirements towards their biased preconclusions.  But the calcs where they start at 100MT and increase seem to assume a max payload while maximum payload is not only unnecessary, but probably undesirable for both going and coming home.

And the things that can be evaluated, like the some of the DV boundaries, they fumble and err on the side of fulfilling their bias.  They don't know enough about future solutions to be evaluating at the detail level they are claiming to be validly criticizing at this level

 

Edited August 6, 2024 by darthgently

[Pthigrivi]

  On 8/5/2024 at 11:05 PM, darthgently said:

Not sure this is official, but if they are really going for the catch, it is perfect

 

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Thats pretty fun. Trying the catch on IFT5 seems really risky but we'll see. Man and Raptor 3 further up in the thread is looking incredible. What are the rumors on a date?

[darthgently]

  On 8/6/2024 at 3:12 PM, Pthigrivi said:

Thats pretty fun. Trying the catch on IFT5 seems really risky but we'll see. Man and Raptor 3 further up in the thread is looking incredible. What are the rumors on a date?

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Grok says:

According to the latest information, Starship test flight 5 could launch as soon as late August or early September, depending on how quickly the FAA grants the modified launch license.

[CBase]

Elon gives end of august or early september estimate in an video interview during teslaowner meeting:

https://youtu.be/tEkRY8TG2BU?t=62

 

[tater]

 

[tater]

 

[tater]

F9 takes ~18 months to build (including long lead items, so in the "I, Pencil" sense).

Reuse incredibly important, launch is now profitable.

Learn about vehicles from reflight (reliability).

Stage 2 of F9 costs $10-12M.

 

Edited August 7, 2024 by tater

[Exoscientist]

  On 8/6/2024 at 2:24 PM, darthgently said:

You are just telling me you don't understand why an Appeal to Authority is a logical fallacy.

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Given previous fumbles, I don't trust your take on either the definition of "relatively small" or your ability to judge in an unbiased manner whether the conclusions hold.  And given the validly noted errors in the paper I don't trust, on the surface, their conclusions.  As they have demonstrated a lack of care

One thing that stands out is their high guesstimated 200m/s DV for TCM seems a bit baseless given that corrections early on are typically quite inexpensive and accuracy of landing position will be largely aerodynamically determined during capture and possible subsequent aero passes.

Another that stands out is that after capture they assume subsequent lowering of apoapsis will not be via repeated aero passes, which is an option at both Mars and Earth.  Each of those passes would use aero forces to fine tune eventual landing position. 

Mostly, while the authors start out by correctly stating that much still needs to be figured out, they then go on to assert that things that haven't been figured out yet won't work.  I'm not sure how one evaluates in detail what hasn't been figured out, but that doesn't slow them down. 

I'm not certain, of course, but it looks to me like they are overestimating the payloads both to, and from, Mars, which would obviously tilt the fuel and lox requirements towards their biased preconclusions.  But the calcs where they start at 100MT and increase seem to assume a max payload while maximum payload is not only unnecessary, but probably undesirable for both going and coming home.

And the things that can be evaluated, like the some of the DV boundaries, they fumble and err on the side of fulfilling their bias.  They don't know enough about future solutions to be evaluating at the detail level they are claiming to be validly criticizing at this level

 

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  EVERYONE uses appeal to authority but it should be recognized that is no guarantee of the validity of one side of an argument. For instance, a team of cardiologists with decades of experience recommends someone should get open heart surgery versus some guy who just read on the internet you can cure heart disease by drinking lemon juice.

 I’m suspicious that this guy who posted this comment posted anonymously from a social media account. Nature is the most prestigious science journal in the world. Most people would proudly give their real name and industry or university affiliation when making a contribution to that journal even if only for a comment on a published research paper. I suspect if he gave his real name and affiliation it would be revealed he was connected to SpaceX, or his knowledge is in fact in an unrelated field.

 About the relatively small difference in delta-v noted by that commenter, it should be kept in mind the authors of the paper argue the specifications SpaceX has provided make it infeasible it could accomplish a round trip for even 12 crew members let alone something of the nature of a passenger ship to carry 100 passengers: 

Conclusion
This paper has compiled a feasibility analysis for Starship based on a published mission scenario and extrapolation of existing systems, where information about Starship had gaps. Using typical analysis methods, a mass budget for the system and subsystems was established. A Lambert solver was applied to identify the minimum ToF and Δv. It has been shown that there are currently several gaps in the available technology to conduct a Mars mission as sketched by SpaceX, e.g. concerning ISRU capability, power supply and the performance of Starship itself, which based on the mass estimate presented here, is incapable to conduct the mission as proposed by SpaceX. Especially, the ToF limits published by SpaceX are found to be unrealistic and cannot be held with the current design, requiring at least further improvement of the performance, some are outright physically impossible (i.e. Mars cannot be reached within 30 days with such a transfer vehicle). The current estimate does also not allow the return flight of Starship. Even with an unrealistic 100% recovery rate of consumables, the mission was not feasible for a 12 person crew per Starship, let alone for the SpaceX published 100 person crew. Further technology development is required, to supplement this launch and transfer vehicle and enable Mars missions. This is affecting Starship itself, but also infrastructure elements needed for the SpaceX proposed mission, especially those required for ISRU-based production of propellant. With the information currently available a Mars mission with Starship is not feasible.

 A small difference in delta-v of about 100 m/s out of 3,400 m/s is not likely to be allow a vehicle that can’t reasonably manage a round trip for 12 to be able to do one for 100 people.

  Robert Clark

Edited August 8, 2024 by Exoscientist

[darthgently]

  On 8/8/2024 at 1:26 PM, Exoscientist said:

  EVERYONE uses appeal to authority but it should be recognized that is no guarantee of the validity of one side of an argument. For instance, a team of cardiologists with decades of experience recommends someone should get open heart surgery versus some guy who just read on the internet you can cure heart disease by drinking lemon juice.

 I’m suspicious that this guy who posted this comment posted anonymously from a social media account. Nature is the most prestigious science journal in the world. Most people would proudly give their real name and industry or university affiliation when making a contribution to that journal even if only for a comment on a published research paper. I suspect if he gave his real name and affiliation it would be revealed he was connected to SpaceX, or his knowledge is in fact in an unrelated field.

 About the relatively small difference in delta-v noted by that commenter, it should be kept in mind the authors of the paper argue the specifications SpaceX has provided make it infeasible it could accomplish a round trip for even 12 crew members let alone something of the nature of a passenger ship to carry 100 passengers: 

Conclusion
This paper has compiled a feasibility analysis for Starship based on a published mission scenario and extrapolation of existing systems, where information about Starship had gaps. Using typical analysis methods, a mass budget for the system and subsystems was established. A Lambert solver was applied to identify the minimum ToF and Δv. It has been shown that there are currently several gaps in the available technology to conduct a Mars mission as sketched by SpaceX, e.g. concerning ISRU capability, power supply and the performance of Starship itself, which based on the mass estimate presented here, is incapable to conduct the mission as proposed by SpaceX. Especially, the ToF limits published by SpaceX are found to be unrealistic and cannot be held with the current design, requiring at least further improvement of the performance, some are outright physically impossible (i.e. Mars cannot be reached within 30 days with such a transfer vehicle). The current estimate does also not allow the return flight of Starship. Even with an unrealistic 100% recovery rate of consumables, the mission was not feasible for a 12 person crew per Starship, let alone for the SpaceX published 100 person crew. Further technology development is required, to supplement this launch and transfer vehicle and enable Mars missions. This is affecting Starship itself, but also infrastructure elements needed for the SpaceX proposed mission, especially those required for ISRU-based production of propellant. With the information currently available a Mars mission with Starship is not feasible.

 A small difference in delta-v of about 100 m/s out of 3,400 m/s is not likely to be allow a vehicle that can’t reasonably manage a round trip for 12 to be able to do one for 100 people.

  Robert Clark

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My last post on this.  No one has ever proposed a round trip to Mars for 100 people on Starship.  Ever.  Please don't respond, just don't.

[tater]

 

[magnemoe]

  On 8/6/2024 at 3:12 PM, Pthigrivi said:

Thats pretty fun. Trying the catch on IFT5 seems really risky but we'll see. Man and Raptor 3 further up in the thread is looking incredible. What are the rumors on a date?

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Agree, as they have spare first stages, works on an second tower and an major upgrade to rocket and engines I would probably splash this too rater than risk damaging the tower or get regulatory problems after an failed catch or simply crashing in an nature preserve. 
The current first stages will be obsolete soon anyway. 
 

[tater]

 

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Edited August 8, 2024 by tater

[Ultimate Steve]

Shots fired!

Something about Raptor 3 just makes it look so unreal... I can't quite put my finger on it.

[AckSed]

  On 8/8/2024 at 10:48 PM, Ultimate Steve said:

Shots fired!

Something about Raptor 3 just makes it look so unreal... I can't quite put my finger on it.

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Maybe it's the frost on the injector head. That's usually a hydrolox speciality.

But yeah, it does seem to be incomplete and yet it works.

[tater]

Tory will no doubt express that he is impressed. He's the opposite of a scrub, he thought it really was not fully assembled.

[Pthigrivi]

  On 8/8/2024 at 10:36 PM, tater said:

 

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You see this engine and its like seeing what engines should look like. 

[tater]

 

Love the frost

[Kartoffelkuchen]

So the Kerbal engines from Jebs Junkyard really are super high-tech and streamlined after all, with the lack of plumbing and cables.

[Flavio hc16]

  On 8/8/2024 at 10:48 PM, Ultimate Steve said:

Shots fired!

Something about Raptor 3 just makes it look so unreal... I can't quite put my finger on it.

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It's the simplicity of it, it looks like magic.

 

" Any technology that is advanced enough will look like magic"

 

This is magic to us ( and Tory Bruno)

[darthgently]

  On 8/9/2024 at 6:41 AM, Flavio hc16 said:

 

" Any technology that is advanced enough will look like magic"

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Paraphrasing Arthur C. Clarke

[tater]

Launch today moved to 11:17 EDT.

[magnemoe]

Not think I seen this mentioned here. 
https://www.reuters.com/technology/space/spacex-talks-land-recover-starship-rocket-off-australias-coast-2024-07-29/
Now, this should also work for US controlled islands in the Pacific, but think most are either have high population or next to none and if you land in an bay you get calmer sea and most of northern Australia has little population. 

Think it was Ellie in space who speculated about future landing on land there and perhaps an launch site, its much closer to equator  than other site but the French launch site. But again US has islands in the Pacific who would also work for both landing and probably an pad. 

[tater]

 

[CatastrophicFailure]

  On 8/8/2024 at 10:48 PM, Ultimate Steve said:

Shots fired!

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One might even say shot… well. 

Gwynne just then:

[tater]

First F9 today. The second one was moved to tomorrow morning.

 

Edited August 10, 2024 by tater