totm nov 2023 SpaceX Discussion Thread

[DAL59]

4 hours ago, tater said:

since I have to hear that awful music

Really?  I thought it was the best movie soundtrack.

6 hours ago, PB666 said:

Lets compare something that exists with something that doesn't exist.

There is nothing wrong with that.  If you make two designs, and the one selected has some problems, and the alternative fixes said problems, yes, there is chance that design will be worse, but the probability of it fixing the existing problems might be higher.

Two birds in a bush are sometimes worth more than 1 in a hand.  

[Bill Phil]

45 minutes ago, DAL59 said:

Really?  I thought it was the best movie soundtrack.

There is nothing wrong with that.  If you make two designs, and the one selected has some problems, and the alternative fixes said problems, yes, there is chance that design will be worse, but the probability of it fixing the existing problems might be higher.

Two birds in a bush are sometimes worth more than 1 in a hand.  

The real problem is that we don't know enough about BFR to compare it to anything...

[ThatGuyWithALongUsername]

32 minutes ago, Bill Phil said:

The real problem is that we don't know enough about BFR to compare it to anything...

Sure we do. There are plenty of details easily available from spacex.com/mars. We can even- for example- figure out the delta-v of the BFS using the ISP, wet mass, and dry mass listed- it's about 9415 m/s with no cargo and a full tank and 5676 m/s with a full 150 tons.

Not sure how useful that statistic is at this moment, but the point remains that we do have plenty of info.

Edited April 8, 2018 by ThatGuyWithALongUsername

[Bill Phil]

Just now, ThatGuyWithALongUsername said:

Sure we do. There are plenty of details easily available from spacex.com/mars. We can even- for example- figure out the delta-v of the BFS using the ISP, wet mass, and dry mass listed- it's about 9415 m/s with no cargo and a full tank and 5676 m/s with a full 150 tons.

Not sure how useful that statistic is at this moment, but the point remains that we do have plenty of info.

Sure. Except that info is not enough to make meaningful comparisons. I could come up with a system just as capable, but comparing it to BFR wouldn't mean anything. We're going to have to wait. At the moment it's barely more than vaporware, and at the most we can make only low level comparisons. Once we have actual hardware (or at least actual engineering), we can start making comparisons based on observed and calculated performance, and not based on power point slides. Until we have a level of detail rivalling this:

https://www.nasa.gov/sites/default/files/files/NASA-SP-2009-566-ADD2.pdf

There isn't much we can compare with. 

I'm sure SpaceX has the details we could use for comparison, at least to decent degrees of accuracy, but they don't want to tell their potential competitors everything.

What you're doing is comparing BFR's design requirements (delta V, payload, and so on), not the actual design. It's supposed to have a delta-V of 9415 with no cargo, but will the final design? What if the requirements change before everything is finalized?

[PB666]

21 minutes ago, Bill Phil said:

Sure. Except that info is not enough to make meaningful comparisons. I could come up with a system just as capable, but comparing it to BFR wouldn't mean anything. We're going to have to wait. At the moment it's barely more than vaporware, and at the most we can make only low level comparisons. Once we have actual hardware (or at least actual engineering), we can start making comparisons based on observed and calculated performance, and not based on power point slides. Until we have a level of detail rivalling this:

https://www.nasa.gov/sites/default/files/files/NASA-SP-2009-566-ADD2.pdf

There isn't much we can compare with. 

I'm sure SpaceX has the details we could use for comparison, at least to decent degrees of accuracy, but they don't want to tell their potential competitors everything.

What you're doing is comparing BFR's design requirements (delta V, payload, and so on), not the actual design. It's supposed to have a delta-V of 9415 with no cargo, but will the final design? What if the requirements change before everything is finalized?

Hah! You know NASA is designed an Aerobraking (inflatable) for future missions to Mars, and they have tested this at least a few times in Earths atmosphere (with failures). SpaceX has not tested any  sounding rockets based on any BFR design, downscaled or otherwise.

"Design subject to change"

The whole rocket design is based on expected aerodynamic performance in Martian atmosphere, and yet they have done no testing. There is a zero percent chance the current design will stick into production. They may not even be able to produce it in the Port of LA and end up having to build a facility to assemble subs in Boca Chica . . . . . thats the current level of planning for BFR.

 

[ThatGuyWithALongUsername]

21 minutes ago, Bill Phil said:

Sure. Except that info is not enough to make meaningful comparisons. I could come up with a system just as capable, but comparing it to BFR wouldn't mean anything. We're going to have to wait. At the moment it's barely more than vaporware, and at the most we can make only low level comparisons. Once we have actual hardware (or at least actual engineering), we can start making comparisons based on observed and calculated performance, and not based on power point slides. Until we have a level of detail rivalling this:

https://www.nasa.gov/sites/default/files/files/NASA-SP-2009-566-ADD2.pdf

There isn't much we can compare with. 

I'm sure SpaceX has the details we could use for comparison, at least to decent degrees of accuracy, but they don't want to tell their potential competitors everything.

What you're doing is comparing BFR's design requirements (delta V, payload, and so on), not the actual design. It's supposed to have a delta-V of 9415 with no cargo, but will the final design? What if the requirements change before everything is finalized?

The BFR isn't quite to the point of having that extensive documentation yet, but it is not "vaporware." Scaled-down Raptor engines have been tested. Early prototypes of the carbon composite tanks have been tested. Yes, the design will slip a bit, but I don't think it will slip that much.

The whole reason for scaling down the rocket was to ensure that it gets developed- not only is it needed to colonize mars, but it is also needed for all future SpaceX missions.

Also, plans can always change, no matter how detailed they are. Even if a thing already exists, that could change, for example the engines could be swapped out after a failure. We know we're speculating, but we at least have something to base our speculations off of.

Remember- that plan you showed was hice and detailed and all... but did it really happen? No.

[ThatGuyWithALongUsername]

25 minutes ago, PB666 said:

Hah! You know NASA is designed an Aerobraking (inflatable) for future missions to Mars, and they have tested this at least a few times in Earths atmosphere (with failures). SpaceX has not tested any  sounding rockets based on any BFR design, downscaled or otherwise.

"Design subject to change"

The whole rocket design is based on expected aerodynamic performance in Martian atmosphere, and yet they have done no testing. There is a zero percent chance the current design will stick into production. They may not even be able to produce it in the Port of LA and end up having to build a facility to assemble subs in Boca Chica . . . . . thats the current level of planning for BFR.

 

Of course the design will change, but likely not to the point of it becoming a completely different architecture. A few tones could be added to the mass, it could be about $1M more than the falcon 1- either way, it's still close enough that the current design estimates can be used as a rough approximation. There has certainly been enough development that if anything SpaceX flies to Mars, it would be some derivative of this design, maybe without some of the less necessary innovations (such as landing back on the launch mount).

Again, speculating.

Also, you seem to be forgetting that we've landed stuff on Mars before. We know plenty about Mars' atmospheric density. Composition may be a bit fuzzier, but we don't need to know that for re-entry.

Edited April 8, 2018 by ThatGuyWithALongUsername

[tater]

From a WSJ article regarding ZUMA:

Quote

But now, these people said, two separate teams of federal and industry investigators have pinpointed reasons for the high-profile loss to problems with a Northrop-modified part -- called a payload adapter -- that failed to operate properly in space.

 

[StrandedonEarth]

So, exactly what everyone was saying immediately after the launch...

Northrop will say it was because it was an unfamiliar-to-them SpaceX adapter they were modifying, instead of the ULA adapters they were used to...

[PB666]

2 hours ago, ThatGuyWithALongUsername said:

Of course the design will change, but likely not to the point of it becoming a completely different architecture. A few tones could be added to the mass, it could be about $1M more than the falcon 1- either way, it's still close enough that the current design estimates can be used as a rough approximation. There has certainly been enough development that if anything SpaceX flies to Mars, it would be some derivative of this design, maybe without some of the less necessary innovations (such as landing back on the launch mount).

Again, speculating.

Also, you seem to be forgetting that we've landed stuff on Mars before. We know plenty about Mars' atmospheric density. Composition may be a bit fuzzier, but we don't need to know that for re-entry.

You seem to be forgetting we've never landed anything over 3 tons and they are trying to land something a magnitude heavier and that there is a long list of Mars cursed mission. The curse of Mars is ignorance. 

[ThatGuyWithALongUsername]

39 minutes ago, PB666 said:

You seem to be forgetting we've never landed anything over 3 tons and they are trying to land something a magnitude heavier and that there is a long list of Mars cursed mission. The curse of Mars is ignorance. 

Ok, I guess I have a little, but that's why they're sending cargo ships first!

If those fail, the design could be tweaked afterwards. I can't see that being that much of a problem, as they would most likely only be adding heat shielding, changing the winglets, etc. That isn't too significant, at least not significant enough to drastically change the design.  Keep in mind that the design itself, while listed as having a dry mass of 85  tons, is actually 75 tons and the 10 tons are reserved for design changes (source: the transcript).

[Ultimate Steve]

And for a bit of positivity, happy second anniversary of the first drone ship landing!

[CatastrophicFailure]

 

yeah, a car’s not gonna cut it for this first flight, they’ll have to launch a semi. Full of cheese wheels. 

[Delay]

IT'S HAPPENING!

[sh1pman]

1 hour ago, Delay said:

IT'S HAPPENING!

Nah, it's vaporware. No point in discussing it, and it'll change a hundred times!

/s

[Nibb31]

That's one hell of a tool.

- Oy, Bob, pass me the main body tool!

- Alright Tom, you want the 9m or the 12m one ?

Edited April 9, 2018 by Nibb31

[PB666]

What happened to building everything from carbon fiber

[Wjolcz]

Just now, PB666 said:

What happened to building everything from carbon fiber

Isn't that cylinder the tool to wrap carbon fiber around it?

[ThatGuyWithALongUsername]

I've never been so excited about a large hollow cylinder in my life! 

Edited April 9, 2018 by ThatGuyWithALongUsername

[NSEP]

I can't wait for them to build the main body using that 'tool'

Thats one hell of a tool!

[tater]

For anyone wondering how this mandrel works:

 

 

[YNM]

That was... huge.

Now I know what the "tool" is also for : Boring Company TBMs !

[tater]

That 787 fuselage is just under 6m in diameter, BTW. Small, lol.

[sh1pman]

10 hours ago, CatastrophicFailure said:

 

yeah, a car’s not gonna cut it for this first flight, they’ll have to launch a semi. Full of cheese wheels. 

Elon is secretly building a giant revolver gun. That shoots cars into space.

[sevenperforce]

Interesting details on TESS:

https://www.nasa.gov/content/goddard/new-explorer-mission-chooses-the-just-right-orbit

That will make for a tricky thing to model in my all-launches KSP save; I may have to break out some classical mechanics. I'm guessing I should go for a zero-eccentricity orbit with the apoapse at 12,000 km and the periapse deep enough that it completes two orbits for every single Mun orbit. Not quite sure where that will be.

Launch to LKO with F9, then burn to TLI (but phased a few orbits off), then use the spacecraft's own engines to adjust for an intercept and slingshot that takes me out to the desired periapse, then a final burn to lower apoapse to 12K km. All while phasing such that the Mun's nearest approach is when the spacecraft is at periapse.

EDIT: Wait a minute, more info. It will launch into a 28.5 degree orbit from the Cape initially, which will NOT reach to the moon, but a subsequent periapsis kick will raise it to the lunar flyby trajectory. The lunar flyby will increase inclination to 40 degrees, where it will stay.

Curiouser and curiouser.