totm nov 2023 SpaceX Discussion Thread

[zolotiyeruki]

7 minutes ago, SpaceFace545 said:

So all of y’all just said that spacex is able to do it and that’s the reply I have gotten on most of my criticism but that doesn’t prove anything. 

What we'all are saying is that SpaceX have a history of taking ideas that sound a bit on the far side of crazy to doubters like you, and then making them happen, while you consistently post doubts that appear to be founded on nothing but intuition.

The shoulder analogy fails on even a superficial level.  It'll be a hinge, not a ball and socket joint.  It'll be made from steel or titanium, not bone and cartilage.  Super heavy can hover, or nearly hover, when empty, while the human body does not have that ability.  The catching tower will have shock absorption, if not outright active suspension, while the steel beams in your analogy do not.

[RealKerbal3x]

2 minutes ago, SpaceFace545 said:

So all of y’all just said that spacex is able to do it and that’s the reply I have gotten on most of my criticism but that doesn’t prove anything. 

SpaceX have done a lot of things previously considered 'impossible'. Landing a first stage propulsively on a barge in the middle of the ocean was impossible. A commercial vehicle flying crew to the ISS was impossible. Cost-effective reuse was impossible. The bellyflop and flip maneuver were also impossible.

They've successfully done all of these things that were impossible, and made them look easy. Clearly the engineers at SpaceX are good at solving extremely difficult problems. So when they announce another plan that sounds crazy, I think we should trust them to figure out a way to do it, given their track record. They would have dropped the tower catch idea long ago if they figured it wouldn't work or just wasn't worth it.

[tater]

42 minutes ago, SpaceFace545 said:

If you are falling you usually stick your legs out and catch yourself like a normal person. Now imagine you are falling but their are two parallel beams on each side of you, instead of using your legs to land like a normal person, you grab these beams and try to support your weight. Turns out nobody’s arms are that strong to catch them while falling so they end up bending upwards and dislocate. This is what I fear will happen to superheavy if it tries such a feat, it’s gridfns will simply bend upwards and shear. 

The grid fins already effectively do this, but grab onto the air.

The vehicle needs hardpoints to lift it with a crane as well—lifted from the top, hanging.

Then add that given the much larger mass, SH might well be able to hover or nearly hover, and it looks far more plausible.

[kerbiloid]

The Starship now needs ledges around the hull.

Spoiler

To match the space between the rails.

 

Edited May 26, 2021 by kerbiloid

[cubinator]

56 minutes ago, SpaceFace545 said:

If you are falling you usually stick your legs out and catch yourself like a normal person. Now imagine you are falling but their are two parallel beams on each side of you, instead of using your legs to land like a normal person, you grab these beams and try to support your weight. Turns out nobody’s arms are that strong to catch them while falling so they end up bending upwards and dislocate. This is what I fear will happen to superheavy if it tries such a feat, it’s gridfns will simply bend upwards and shear. 

Starship isn't built like a human, though. Maybe it's more like a Dug, whose arms are stronger than their legs.

I think it's reasonable that the booster could be built to hang from the griffins, considering they already carry a similar stress while falling and there is a bulkhead nearby for the second stage attachment point. What makes me skeptical is the fact that the machine needed to grab the booster is basically a robot as big as a skyscraper, which sounds very difficult to pull off and ripe with unforseen issues.

[RCgothic]

55 minutes ago, SpaceFace545 said:

But in reality it makes 0 sense

What doesn't make sense?

Superheavy will come in pretty slowly. It can probably hover. Relative velocity will be low. We can see from F9 landings that accuracy will be good.

Superheavy doesn't weigh that much,  a small fraction of the ~1450t it has to support above. Suspending a weight is easier than supporting it. It already needs hardpoints for lifting purposes. The grid fins are already hardpoints.

Mechanical stresses are well understood. It's not a fuzzy science like "where do the cavitations form when tons of cryogenic liquid in a long distribution system are suddenly rotated."

Robotic grabs are also well understood, if not quite built at this scale before. 

All of these are just taking existing engineering knowledge and applying it to a new application. This is categorically not the hardest problem SpaceX has ever solved. I doubt it makes the top 10.

 

And if it doesn't work, so what? Booster gets a little more dry mass for legs and takes a little longer to get back to the pad. No big deal. Doesn't break the system.

[SpaceFace545]

5 minutes ago, cubinator said:

Starship isn't built like a human, though. Maybe it's more like a Dug, whose arms are stronger than their legs.

I think it's reasonable that the booster could be built to hang from the griffins, considering they already carry a similar stress while falling and there is a bulkhead nearby for the second stage attachment point. What makes me skeptical is the fact that the machine needed to grab the booster is basically a robot as big as a skyscraper, which sounds very difficult to pull off and ripe with unforseen issues.

I get that and it isn’t implausible that it could support it’s weight from the gridfins. I still find it questionable how the impact on the gridfins will be dealt with, that momentary force is where I get my shearing force from. Even if the shocks where in the catching tower there would be a momentary impact before the shocks start to compress. 

[RCgothic]

4 minutes ago, SpaceFace545 said:

I get that and it isn’t implausible that it could support it’s weight from the gridfins. I still find it questionable how the impact on the gridfins will be dealt with, that momentary force is where I get my shearing force from. Even if the shocks where in the catching tower there would be a momentary impact before the shocks start to compress. 

Depends on the inertia and velocity of the grab heads to Superheavy.

If they design them to track Superheavy's motion before engaging, no shock.

If Superheavy hovers motionless, no relative motion, no shock.

If they design the active portion of the grabs with low inertia, low shock even with relative motion. The tower system can then progressively apply resistance so as not to cause excessive shock.

 

[Terwin]

5 minutes ago, SpaceFace545 said:

I get that and it isn’t implausible that it could support it’s weight from the gridfins. I still find it questionable how the impact on the gridfins will be dealt with, that momentary force is where I get my shearing force from. Even if the shocks where in the catching tower there would be a momentary impact before the shocks start to compress. 

1) the system need not be static, it could easily accelerate to closely match the current speed of SH

2) SH can hover, so there need not be any significant velocity at initial contact, nor any significant initial load, as they can reduce thrust after initial contact until the last engine shuts down.(sort of like one parent letting go of the baby after the other parent has a firm grip)

[Lukaszenko]

1 hour ago, SpaceFace545 said:

So all of y’all just said that spacex is able to do it and that’s the reply I have gotten on most of my criticism but that doesn’t prove anything. 

Because many of your posts are dismissing SpaceX's ability to do basically anything, sometimes (as in this case) solving the most simple of engineering  problems. Yeah, how or whether they can catch the thing will be interesting to see. But, questioning their ability to essentially calculate how much steel is needed to carry a known load is frankly annoying to even consider, much less compose a thorough response to.

This thread is meant to discuss how SpaceX plans to achieve(d) their crazy-ass claims, but in order to do that constructively we have to give them a little benefit-of-doubt. Wasting time on discussing their competence in moving an engine a few meters across the ground, when they've been routinely flying them to orbit (and back) for over a decade, is just not why most of us are here. 

Edited May 26, 2021 by Lukaszenko

[RealKerbal3x]

SN15 is being lifted off the pad. Looks like it's on the way back to the production site today.

 

[NFUN]

please stop feeding the concern troll thank you

[SOXBLOX]

2 hours ago, SpaceFace545 said:

I get that and it isn’t implausible that it could support it’s weight from the gridfins. I still find it questionable how the impact on the gridfins will be dealt with, that momentary force is where I get my shearing force from. Even if the shocks where in the catching tower there would be a momentary impact before the shocks start to compress. 

So, what is the magnitude of that shear force? Did you calculate it? I'll bet SpaceX did. And they probably know a lot about how they plan to build their own rocket.

3 hours ago, SpaceFace545 said:

So all of y’all just said that spacex is able to do it and that’s the reply I have gotten on most of my criticism but that doesn’t prove anything. 

You're correct. It doesn't "prove" anything. Neither does your criticism, for the exact same reason. So, given the choice between a roomful of qualified engineers and, no offense, some guy on the Internet, I'll take the engineers.

[JoeSchmuckatelli]

3 hours ago, kerbiloid said:

The Starship now needs ledges around the hull.

  Hide contents

To match the space between the rails.

 

That looks like a sand casted explosive shell - from the early part of last century or the latter part of the previous.  Am I correct - or is it something else? 

[kerbiloid]

2 minutes ago, JoeSchmuckatelli said:

That looks like a sand casted explosive shell - from the early part of last century or the latter part of the previous.  Am I correct - or is it something else? 

Yes, some old shells for spirally cut barrels.

[CatastrophicFailure]

4 hours ago, SpaceFace545 said:

Turns out nobody’s arms are that strong to catch them while falling so they end up bending upwards and dislocate

:48

 

Douglass A-3 controlled crashing landing on a carrier. 40,000lbs doing well over a hundred mph all stopped without damage by a chunk of metal not much bigger than, well, your arm. 

Turns out, metal is really strong. And engineers are really smart. 

SpaceX has lots of both. 
 

3 hours ago, cubinator said:

What makes me skeptical is the fact that the machine needed to grab the booster is basically a robot as big as a skyscraper,

Humanity has made moving building-sized things before:

The rest is just details at thus point. 

[JoeSchmuckatelli]

1 minute ago, CatastrophicFailure said:

Turns out, metal is really strong. And engineers are really smart. 

SpaceX has lots of both

You win the internet today. ;D

[tater]

The table that goes on the pad, with launch hold down clamps (red).

 

 

[Silavite]

I'm in Orlando today for a connecting flight which is scheduled to take off at 1:45, and the Starlink launch is scheduled for 3. Never more have I wanted a flight to be delayed.

[Beccab]

If this starlink flight goes well, this should be the 100th consecutive successful falcon 9 flight!

[SpaceFace545]

48 minutes ago, Beccab said:

If this starlink flight goes well, this should be the 100th consecutive successful falcon 9 flight!

chances are that it will

[tater]

26 min

 

[kerbiloid]

1 hour ago, tater said:

 

They will forget that forklift inside.
A typical surgeon mistake.

[JoeSchmuckatelli]

6 minutes ago, kerbiloid said:

They will forget that forklift inside.
A typical surgeon mistake.

Not a mistake... the plan.  How else do you expect them to unload the corpsicles at Mars?

 

Sheesh.

Edited May 26, 2021 by JoeSchmuckatelli

[RealKerbal3x]

Starlink stream is live.