totm nov 2023 SpaceX Discussion Thread

[magnemoe]

12 minutes ago, zolotiyeruki said:

If you're going to catch SS in a net, you could also add parachutes to slow the descent.  Since stopping distance is proportional to the square of the starting speed, assuming constant deceleration, dropping the terminal velocity, say, in half would reduce the stopping distance by 75%.

The approach seems a bit odd to me, given SpaceX's decision to scrap a similar approach with the fairings.  Of course, the fairings have a much lower vertical velocity, and are presumably much more susceptible to wind, and SpaceX have figured out how to fish them out of the ocean without damage.

I *would* be concerned about potential damage to heat shield tiles with a Giant Net approach.

How much lighter would SS be without the propellant needed for the flip, hover, and landing?  How much would that affect its terminal velocity?

Problem with parachutes is that you are very affected by wind. The fairings are also very affected by wind and assume this is why they gave up catching them. 

As I understand they will catch on the upper fins like the plan for superheavy and the grind fins probably using the same system perhaps a bit different grab surface. 

Note that this is something they plan to do later. First they need to be able to land reliable first. Then they need to be able to land very accurate as in much less an meter margin and do this reliable. 
They are not very interested in crashing into the launch pad or tower, they will need methane / lox gas trusters working well for even considering this. 
For an sea launch platform this method makes some sense as you are landing over the side of the platform, the catch crane then rotates and put it on an trolley. The top crane can then move it to the pad or you can roll the stage back for servicing. 
 

23 minutes ago, sevenperforce said:

The fairings did not have control surfaces, and so there was no way to guide them down to the net without a steerable chute. The steerable chute allowed them to guide the fairings into the net...but also allowed the fairings to touch down gently in the water, so they realized they didn't need the net at all.

The probably also redesigned the fairings to require much less refurbishing after splashdown. 

[kerbiloid]

No need in parachuting until touchdown.

A pack of much smaller drogue chutes can slow the descent down to 20 m/s for free.

Then at 50 m or so they ignite the landing engines and decouple the chutes.

Thus the wind effect  will be minimized.

[tater]

Apparently SN15 did ambient pressure testing this morning.

[Brotoro]

[tater]

Orbital SS thrust structure, I presume?

 

And... <shrug>

I had initially thought it was some way to move this safety—perhaps to Houston. The fake flap things threw me, though.

It's clear the black nose cap has just a single access hole from this angle.

 

[tater]

Aero forces and/or g-load  simulator?

 

[tater]

[Clamp-o-Tron]

44 minutes ago, tater said:

Aero forces and/or g-load  simulator?

 

I think he means the simulation he claims we might live in...

(on a more philosophical note, how would we know? Why would we care, especially if there is no difference between a simulated and “real” world?)

[tater]

1 hour ago, Clamp-o-Tron said:

I think he means the simulation he claims we might live in...

Sorry, I posted that comment assuming it would be appended to the post just above, not as a reply to his tweet.

I mean, is the "mystery structure" around that blunt nosecone a aero/g-load simulator.

[RyanRising]

We sure do need some legs, Elon. We sure do. Maybe not on the tower though.

[JcoolTheShipbuilder]

Imagine a tower with giant legs running past you to catch a falling rocket

[kerbiloid]

Two of them: "Catch Up!" and "Go Catch!"

[RealKerbal3x]

(Quoting this here as it's offtopic for the other thread)

2 hours ago, SpaceFace545 said:

Every single starship prototype has failed in one way or another but never in the same way.

So? That's good, it means that they're making progress. That's how rapid iterative testing works.

(also, technically, SN5 and 6 didn't fail)

2 hours ago, SpaceFace545 said:

SpaceX isn't really American or with NASA.

They're an American company, and have several NASA contracts. Does them being a private company rather than a government organisation somehow make them not American?

2 hours ago, SpaceFace545 said:

SpaceX just wants to "colonize mars" for some reason not explore space for the American people.

Setting aside the challenges it entails for now, colonising Mars is meant to benefit the entire human race, not just Americans. Aside from providing jobs and showing the United States' prowess in space, I don't see the Artemis program providing that great of a benefit compared to protecting human life by building a colony on another planet.

[derega16]

So...this is how SS/SH will recovered 8f everything go as Elon wanted. Just waiting for him to fund a biotech company and discover some gigantic alien to clone.

 https://youtu.be/mQsL1YA6z_U

 

 

Edited April 10, 2021 by derega16

[kerbiloid]

Spoiler

They need LK / 7K-LOK docking adaptor way to land.

Legs, an on-ground honeycomb plate to land on, and a sting to stick in.

They could drop such honeycomb on Mars and anchor it.

 

Edited April 10, 2021 by kerbiloid

[wumpus]

On 4/9/2021 at 11:32 AM, magnemoe said:

Problem with parachutes is that you are very affected by wind. The fairings are also very affected by wind and assume this is why they gave up catching them. 

As I understand they will catch on the upper fins like the plan for superheavy and the grind fins probably using the same system perhaps a bit different grab surface. 

Note that this is something they plan to do later. First they need to be able to land reliable first. Then they need to be able to land very accurate as in much less an meter margin and do this reliable. 
They are not very interested in crashing into the launch pad or tower, they will need methane / lox gas trusters working well for even considering this. 
For an sea launch platform this method makes some sense as you are landing over the side of the platform, the catch crane then rotates and put it on an trolley. The top crane can then move it to the pad or you can roll the stage back for servicing. 
 

The probably also redesigned the fairings to require much less refurbishing after splashdown. 

I'd have to assume the whole scaling issue would be a bigger problem than the wind.  The shuttle SRBs splashed down over 44 m/s (I remember reading >100mph), although it is possible that Starship will be lighter.

If you are planning on falling through the upper atmosphere, I'd still think  you could use drogue chutes to cut your delta-v.  You'd still need retro-rockets, but far less fuel (and thus more mass going up, assuming the parachutes were lighter than the propellant mass.  Which isn't a guaranteed thing).

[magnemoe]

1 hour ago, wumpus said:

I'd have to assume the whole scaling issue would be a bigger problem than the wind.  The shuttle SRBs splashed down over 44 m/s (I remember reading >100mph), although it is possible that Starship will be lighter.

If you are planning on falling through the upper atmosphere, I'd still think  you could use drogue chutes to cut your delta-v.  You'd still need retro-rockets, but far less fuel (and thus more mass going up, assuming the parachutes were lighter than the propellant mass.  Which isn't a guaranteed thing).

However starship is falling pretty slowly then vertical because its huge cross section anyway and this is controlled flight.
Yes you have self guiding parachutes its used by the military to resupply forces. I assume this is used then flying low is dangerous and the force might be behind enemy lines, here the accuracy only need to be in the hundreds of meter.
I guess the falcon 8 fairings uses an versions of this but here the parachute and ship talk, this did not work well as the fairing is also very affected by wind. an container to support an unit would be much more dense.  

[wumpus]

3 minutes ago, magnemoe said:

However starship is falling pretty slowly then vertical because its huge cross section anyway and this is controlled flight.
Yes you have self guiding parachutes its used by the military to resupply forces. I assume this is used then flying low is dangerous and the force might be behind enemy lines, here the accuracy only need to be in the hundreds of meter.
I guess the falcon 8 fairings uses an versions of this but here the parachute and ship talk, this did not work well as the fairing is also very affected by wind. an container to support an unit would be much more dense.  

In other news, SpaceX has given up on catching fairings in nets, showing that they realize that the wind is just to variable to control.    Then there's the issue of "do you just release the parachutes and make them disposable", which might rub Elon the wrong way.  When I first joined this forum I was convinced that parachutes were the way to go (something KSP teaches badly), but now I'm highly skeptical of combining parachutes with landing in exact locations (one or the other is fine).

[magnemoe]

23 hours ago, tater said:

Orbital SS thrust structure, I presume?

 

And... <shrug>

I had initially thought it was some way to move this safety—perhaps to Houston. The fake flap things threw me, though.

It's clear the black nose cap has just a single access hole from this angle.

 

What is the purpose of the structure here? keeping is stable during mating? why don' add some scaffolding on the top is welded manual. 

The top one looks like an test object, only holes on one side and why the 2 large hole and the bottom right part, now it could be for mounting an vacuum engine for SS. 

[JoeSchmuckatelli]

18 hours ago, magnemoe said:

What is the purpose of the structure here? keeping is stable during mating? why don' add some scaffolding on the top is welded manual. 

The top one looks like an test object, only holes on one side and why the 2 large hole and the bottom right part, now it could be for mounting an vacuum engine for SS. 

From the bottom photo - it looks like they are getting close to finally summoning Gozer, Scourge of the Glethestements. 

 

The source of Elon's power is thus revealed 

Edited April 11, 2021 by JoeSchmuckatelli

[StrandedonEarth]

From looking at this, I start to wonder if they want to do some sort of structural testing with the forward flap actuators,  to better understand the dynamics and verify simulations/calculations, including checking for fatigue?

Edited April 11, 2021 by StrandedonEarth

[kerbiloid]

It's incomplete. One bar is absent,

If remove another one, but add two  chevrons (or four other bars), it will be unicursal.

Is this mirror dome a trap for what should appear in the portal?

Edited April 11, 2021 by kerbiloid

[tater]

There is apparently a hydraulic ram inside as well (it was spotted being lowered inside the nose before the black cap).

I suppose they can pull down on it and simulate whatever the max g-load is. I would imagine there is a substantial difference between how pressurized tanks deal with that axial loading, vs a hollow cargo fairing.

[tater]

[Flying dutchman]

But why?