totm nov 2023 SpaceX Discussion Thread

[tater]

5 minutes ago, Exoscientist said:

 Launch and landing is by same vehicle.  SpaceX is still talking about rapid reuse out of Boca Chica, so same issues arise.

Yes, but the offshore idea is still about P2P.

I'll believe multiple flights per day out of Boca Chica when I see it. Currently they are limited to what, 5 a year?

[StrandedonEarth]

26 minutes ago, CatastrophicFailure said:

 

1 hour ago, wumpus said:

You'd also assume that Musk would have tested throwing a ball at cybertruck's glass...

They did. What they did not test, apparently, was hitting the door with a sledgehammer then throwing a ball at the window… 

 

I’m guessing what was not tested was how many times they could throw a steel ball at the window before it broke. Even so-called “bullet proof glass” can only stop so many bullets before it fails. In vehicles, the idea is that you’ve driven away by then

[sevenperforce]

18 hours ago, StrandedonEarth said:

I’m guessing what was not tested was how many times they could throw a steel ball at the window before it broke. Even so-called “bullet proof glass” can only stop so many bullets before it fails. In vehicles, the idea is that you’ve driven away by then

Bullet-resistant glass stops bullets by fracturing in layers. So each successive bullet physically and visibly erodes the glass.

In this instance they had tempered high-toughness laminated glass that was capable of resisting the steel ball completely. So in theory you could throw a steel ball at it 10 or 50 or 100 times, because there's no cumulative damage. However, the sledgehammer strike to the door mechanism evidently fractured the glass below the visible pane, which weakened it dramatically, allowing the ball to break it on the first throw.

Edited May 4, 2023 by sevenperforce
Thanks for correction by @Lukaszenko

[kerbiloid]

58 minutes ago, sevenperforce said:

Egads!

Whatever will we do?

While we're at it, let's investigate ALL the inaccurate depictions of vehicles in ALL purely promotional or webcast material!

You may laugh, but that's where the Kraken lives.

[magnemoe]

4 hours ago, Nuke said:

ive always been a proponent of moon before mars anyway. if we can make a 2 stage reusable we can make a 3-stage reusable. so a reusable 3-stage to the moon, with a local fuel depot might be the way to go. you can not only refuel upper stage enough to return to earth, you can also fuel ships going elsewhere. if you wanted a nuclear engine, you could operate without concern for contaminating the earth if it operates out of the moon base. if i was going on a mars mission i wouldn't mind that infrastructure existing first. you can cut significant time off of delivery of emergency supplies if its on the moon ready to go on a fast transfer trajectory.

Disagree, now I say Starship is way overbuild for an 4 man moon lander even if you bring two rovers an an light drill rig. 
However its probably cheaper to mod starship than building something new and more custom made. 
Starship would be very good for building an base. 

Benefit of moon is that its just 2 days away so you can evacuate or get resupplies fast.  Moon is more hostile but easier to reach. 
3 stages makes little sense, you first outpost is an tanker in LEO, second in moon orbit who probably be moonship for some time.  

Benefit here is that little infrastructure is needed. You need an reusable superheavy, you want reusable tankers to leo but the first tankers going to the moon will not be reusable. 

[Lukaszenko]

53 minutes ago, sevenperforce said:

Bullet-resistant glass stops bullets by fracturing in layers. So each successive bullet physically and visibly erodes the glass.

In this instance they had tempered glass that was capable of resisting the steel ball completely. So in theory you could throw a steel ball at it 10 or 50 or 100 times, because there's no cumulative damage. However, the sledgehammer strike to the door mechanism evidently fractured the glass below the visible pane, which weakened it dramatically, allowing the ball to break it on the first throw.

If you fracture tempered glass, it propagates through the whole pane and shatters it into many pieces, so I don't think that's the explanation

[CatastrophicFailure]

5 hours ago, Exoscientist said:

 Launch and landing is by same vehicle.  SpaceX is still talking about rapid reuse out of Boca Chica, so same issues arise.

   Bob Clark

IIRC Boca is currently limited to like half a dozen orbital launches a year per the existing EIS. For that to change… much would need to change. We would most likely see that kind of reuse in Florida, in the future. 

[darthgently]

My sense of it is that rapid reuse might occur  from offshore platforms, but with stage 0 in the mix now they are "going to need a bigger boat".   They sold off the 2 oil rigs as they were too small.  The logistics of operating from platforms would be a lot of overhead, but maybe refueling from a large specialized tanker ship would be more efficient than 140 tanker truck loads

[Nuke]

10 hours ago, sevenperforce said:

How so?

Two-stage reusable is the sweet spot. The lower stage can boostback to the launch site and the upper stage can loiter on orbit until it's time to initiate a re-entry that will bring it back to the launch site.

A three-stage reusable architecture, on the other hand, is extremely challenging. The second stage won't make it all the way to orbit but will be entering at such high speeds that it needs essentially a full heat shield, and it's going to come down halfway around the world, so how does it get back to the launch site?

The only thing I can think of that might work for a rapidly reusable three-stage architecture would be a RTLS booster with a second stage that brings the third stage to just shy of orbit, then re-enters about 3/4 of the way around and enjoys a hypersonic glide the rest of the way to the launch site. But then there's no real reason to make the third stage reusable.

my thought was the second stage would go to either a very low orbit or a more eccentric orbit such that it can be landed after one orbit. the third stage would be good to complete tli and lunar landing. for reusability it would have to refuel on the moon using isru before return to earth. of course you need to set up a moon base with a fuel plant and storage first (you are going to need first gen starship for this). alternatively your third stage would be something you can break down and utilize on the moon for base/spacecraft construction. for example it might have a large number of smaller rcs units and a cluster of engines, such that they can be removed and used on other outgoing missions to the solar system, tanks could be converted to habitats or fuel storage for the moon base. idea is you would use local materials to build structural components, equip with the salvageable parts and launch missions from the moon base directly.

i dont know how it would work out delta-v wise. but it seems like a natural progression from starship to set up regular earth-moon supply chain. i think the timeline for a lunar base can be greatly accelerated over a mars base. there is also no reason not to build both bases in parallel. once the moon base is bootstrapped then you have two supply lines headed for mars rather than one. 

Edited May 4, 2023 by Nuke

[kerbiloid]

8 hours ago, sevenperforce said:

Bullet-resistant glass stops bullets by fracturing in layers. So each successive bullet physically and visibly erodes the glass.

In this instance they had tempered glass that was capable of resisting the steel ball completely. So in theory you could throw a steel ball at it 10 or 50 or 100 times, because there's no cumulative damage. However, the sledgehammer strike to the door mechanism evidently fractured the glass below the visible pane, which weakened it dramatically, allowing the ball to break it on the first throw.

Having no exhaust trench is like shooting from bazooka standing close to the wall behind.

Impressive but painful.

[mikegarrison]

The offshore starship launch sites (especially in their point-to-point iteration) were always pretty sketchy in terms of how many important details and issues were handwaved away.

[tater]

1 hour ago, Nuke said:

my thought was the second stage would go to either a very low orbit or a more eccentric orbit such that it can be landed after one orbit. the third stage would be good to complete tli and lunar landing. for reusability it would have to refuel on the moon using isru before return to earth. of course you need to set up a moon base with a fuel plant and storage first (you are going to need first gen starship for this). alternatively your third stage would be something you can break down and utilize on the moon for base/spacecraft construction. for example it might have a large number of smaller rcs units and a cluster of engines, such that they can be removed and used on other outgoing missions to the solar system, tanks could be converted to habitats or fuel storage for the moon base. idea is you would use local materials to build structural components, equip with the salvageable parts and launch missions from the moon base directly.

Nuclear shuttle.

That thing was supposed to be 33' in diameter (~10m).

 

[SunlitZelkova]

23 hours ago, tater said:

"Independent review" implies something other than the FAA—which is already tasked with exactly what is needed.

There are no people on this, there can be no "Challenger disaster."

 

NASA would do the review on HLS crew... who else would be the independent reviewer that would be better than NASA? Some random congressman? The VP? LOL.

A Rogers Commission type organization could do the job.

You referred to oversight being a pain in general, not specifically to this launch. When people are on this in the future, there could be another Challenger disaster. People on the ground could be affected too.

The FAA colluding with SpaceX is not a wild possibility. Look at what happened with the 737 MAX between Boeing and the FAA.

Edited May 4, 2023 by SunlitZelkova

[tater]

4 minutes ago, SunlitZelkova said:

A Rogers Commission type organization could do the job.

Right. That makes sense... because a rocket they gave a 50/50 chance of blowing up needed to be blown up. With no people aboard, and no people will be aboard it for a long time—and when they are, NASA will have signed off on it.

[Exoscientist]

 The Angry Astronaut gives an  insightful analysis of the environmental lawsuit against the FAA and suggests it could delay another launch from Boca Chica for another two years. The reason is the extent of the spread of concrete debris is beyond the 700 acres implied in the FAA environmental assessment. This means a more detailed environmental impact report must be written. This takes longer, thus suggesting the longer time for another launch license to be granted:

 

  Bob Clark

Edited May 4, 2023 by Exoscientist
Inadvertent duplicated post.

[kerbiloid]

Spoiler

 

[Spaceception]

So another Falcon 9 launched. No discussion here, it was the middle of the night though, granted. But that makes 7 landings for this booster according to the description.

 

[sevenperforce]

17 hours ago, Lukaszenko said:

If you fracture tempered glass, it propagates through the whole pane and shatters it into many pieces, so I don't think that's the explanation

Yes, correct; I said tempered glass but I meant laminated glass. Good catch.

11 hours ago, Nuke said:

my thought was the second stage would go to either a very low orbit or a more eccentric orbit such that it can be landed after one orbit. the third stage would be good to complete tli and lunar landing. for reusability it would have to refuel on the moon using isru before return to earth. of course you need to set up a moon base with a fuel plant and storage first (you are going to need first gen starship for this). alternatively your third stage would be something you can break down and utilize on the moon for base/spacecraft construction.

Ok, gotcha. So this would still be a reusable two-stage-to-orbit design, just with a third stage that is reusable BLEO.

[Kerwood Floyd]

I think I must be missing something. Much of the discussion up-thread about the FTS seems to be speculating that the charges were undersized. It seems to me that the charges, once they were activated, worked just fine The problem is that the charges didn't go off until ~40s after the command was sent. Or am I misinformed?

 

[Piscator]

As far as I know, the charges worked immediately. It's just that it took the vessel 40 seconds to sufficiently depressurize to finally loose enough rigidity to be torn apart by aero forces.

[Kerwood Floyd]

nevermind

Edited May 4, 2023 by Kerwood Floyd
I'm an idiot

[Terwin]

35 minutes ago, Piscator said:

As far as I know, the charges worked immediately. It's just that it took the vessel 40 seconds to sufficiently depressurize to finally loose enough rigidity to be torn apart by aero forces.

Sounds like we just need a second line of charges then, to allow a pac-man style chunk to be cut loose and allow the depressurization to happen much more quickly.  (or just put it on both sides and cut it in half, which is probably what the FAA would prefer...)

[magnemoe]

14 minutes ago, Terwin said:

Sounds like we just need a second line of charges then, to allow a pac-man style chunk to be cut loose and allow the depressurization to happen much more quickly.  (or just put it on both sides and cut it in half, which is probably what the FAA would prefer...)

For maximum effect put it all around at the seam for the common dome.  That would be spectacular to look at.  But it would be an pain to install and uninstall and would create lots of drags unless you had an intent at the seam.

[wumpus]

1 hour ago, Piscator said:

As far as I know, the charges worked immediately. It's just that it took the vessel 40 seconds to sufficiently depressurize to finally loose enough rigidity to be torn apart by aero forces.

According to the requirements listed in the Scott Manley video, that isn't enough.  You need to burn the fuel/oxidizer as well.  It all but requires a big explosion.  You might get less grief from the FAA if the engines stopped, but maybe not when you have a large bomb doing flips after the automated destruct system fired.

[wumpus]

21 hours ago, sevenperforce said:

Conspiracy theories require more evidence than a bare recitation of possibility.

And generally old space is set up to get an easier path.  I'm wondering when spacex will hire several senior FAA officials as "VP of FAA relations" (and obviously, doing same with the DoD, NASA, and congressional staffers).  That will put them on the path to becoming the new "old space".  I suspect they've already started.

21 hours ago, sevenperforce said:

Egads!

Whatever will we do?

While we're at it, let's investigate ALL the inaccurate depictions of vehicles in ALL purely promotional or webcast material!

/s

Atkins law: number 30. (von Tiesenhausen’s Law of Engineering Design) If you want to have a maximum effect on the design of a new engineering system, learn to draw. Engineers always wind up designing the vehicle to look like the initial artist’s concept.

Unfortunately, you only get "looks like", not an exact match.  Because even if the artists have a good grasp of rocket science, they haven't done enough iterations on the design to grasp all the details.