totm nov 2023 SpaceX Discussion Thread

[JoeSchmuckatelli]

1 hour ago, sevenperforce said:

What evidence do you have to suggest that any engines exploded on relight during either Superheavy booster landing burn?

 

6 minutes ago, Ultimate Steve said:

Probably the video footage of an engine exploding on relight during the IFT-4 Superheavy booster landing burn, a giant mass of fire remaining where the engine was, and chunks flying off.

Yeah - that happened.  Quibble that we don't know Fer Shure, but it's the most likely thing. 

Oh - Booster landing.  No info vis SS

Despite this - it pretty much 'stuck the landing' - maybe what they need is a landing platform with some deep water /a deluge system to put out the fire? 

[Exoscientist]

  So as I argued before SpaceX should investigate an expendable version of Superheavy/Starship. The Raptor has been in development since 2016 and it is still experiencing  explosions  during relights. The Falcon 9 was spectacularly successful by first developing it as an expendable, doing several profitable, commercial flights in the expendable form, then progressing to the reusable form. Note all those successful, expendable flights gave good information on the Merlins reliability.

 A majorly important advantage of going first with the  expendable form of the SH/SS is that we can do both single launch Moon and Mars missions now  by using the Falcon 9 upper stage as a 3rd stage/lander stage and the Dragon as the crew module. (The Orion capsule is overbloated both in cost and mass.) Going with the expendable form of the SH/SS means you get greatly increased payload to LEO now , probably in the 250 to 300 ton range, by not having to keep the large amount propellant on reserve for the SH for return to launch site, and you wouldn't get the tripling of the dry mass of the SS  for reusability systems we have now.

For either of those manned flights to the Moon or Mars, this would be around the cost of a SH/SS single launch, $95 million. Compare this to the likely $7+ billion per mission cost of Artemis when you add up all of SLS, Orion, Starship HLS, Boeing EUS, advanced booster upgrade, and Gateway costs. And compare it to $500 billion(!) cost NASA once estimated for the full development costs of a manned Mars program.

 Quite importantly also, we could do it, literally, like, tomorrow. Not by 2028 for going to the Moon by the Artemis architecture, and not by the 2030's for Mars by the most optimistic estimates by Elon Musk.

   Bob Clark

Edited Wednesday at 03:27 PM by Exoscientist

[JoeSchmuckatelli]

3 hours ago, Exoscientist said:

...expendable Superheavy/Starship

Has anyone looked at or seen the numbers vis Booster performance and projected it as what its expendable first stage capability actually might be? 

Because thus far they've both gone slower than Saturn's first stage 

[Nuke]

always wondered about using falcon first stage as extra side boosters for starship. in fact i bet that was the reasoning for the offset grid fin placement on sh. turning a 2-stage reusable into a 3 stage might improve efficiency.

Edited Friday at 01:21 AM by Nuke

[mikegarrison]

1 hour ago, Nuke said:

always wondered about using falcon first stage as extra side boosters for starship. in fact i bet that was the reasoning for the offset grid fin placement on sh. turning a 2-stage reusable into a 3 stage might improve efficiency.

One of the ways KSP lies to you is that it is not easy to just MOAR BOOSTERS onto the side of a rocket. The structure of a typical rocket is designed to carry loads axially, but adding side boosters moves the load paths.

[magnemoe]

13 hours ago, mikegarrison said:

One of the ways KSP lies to you is that it is not easy to just MOAR BOOSTERS onto the side of a rocket. The structure of a typical rocket is designed to carry loads axially, but adding side boosters moves the load paths.

This, it best has to be designed in from the start,  This is why falcon heavy was so delayed. 

[gfdgfherytrey]

Because spacex does not want to recover booster 11 and ship 29, does that mean that anyone can grab the ship and bring it home with them or is it still their property?

[darthgently]

17 hours ago, mikegarrison said:

One of the ways KSP lies to you is that it is not easy to just MOAR BOOSTERS onto the side of a rocket. The structure of a typical rocket is designed to carry loads axially, but adding side boosters moves the load paths.

Any Kerbal knows that this is why you always add 16 or more side boosters so as to more smoothly and evenly space the added load via the circumferential squeezing theorem.  You want the center core to crowdsurf on a plethora of boosters.

 

[Ultimate Steve]

3 hours ago, gfdgfherytrey said:

Because spacex does not want to recover booster 11 and ship 29, does that mean that anyone can grab the ship and bring it home with them or is it still their property?

Presumably they are at the bottom of the ocean by now. If you can get them, you probably deserve them.

There is some precedent for that, Jeff Bezos funded a submarine mission to recover engines from the Saturn V. Unsure what exactly the law is there. Probably classified as some sort of salvage, but ITAR might have something to say about the fiddly bits of the engines. F1 was an obsolete design and Raptor is cutting edge.

[Jacke]

1 hour ago, Ultimate Steve said:

Presumably they are at the bottom of the ocean by now. If you can get them, you probably deserve them.

There is some precedent for that, Jeff Bezos funded a submarine mission to recover engines from the Saturn V. Unsure what exactly the law is there. Probably classified as some sort of salvage, but ITAR might have something to say about the fiddly bits of the engines. F1 was an obsolete design and Raptor is cutting edge.

It's not just ITAR (but that's rather serious).  It's also the Outer Space Treaty.  Components and debris from a launch or spacecraft aren't just Salvage, they're still under the jurisdiction of the signatory Nation who created or licenced them.

[Lisias]

6 hours ago, Ultimate Steve said:

Presumably they are at the bottom of the ocean by now. If you can get them, you probably deserve them.

Risk management: knowing Musk, he had already assessed the situation. I would not be surprised if the engines have some self-destruction mechanism - perhaps some of the engine's failures Spaceship had may due they ironing out these devices being triggered prematurely by accident.

At the time of the Apollo Missions, no one (besides Jules Verne and, perhaps, the Military) had the technology to do deep ocean recoveries, but nowadays even civilians are being able (with deadly reserves) to reach huge deepness in the ocean.

 

6 hours ago, Ultimate Steve said:

There is some precedent for that, Jeff Bezos funded a submarine mission to recover engines from the Saturn V.

Exactly my point.

 

6 hours ago, Ultimate Steve said:

Unsure what exactly the law is there. Probably classified as some sort of salvage, but ITAR might have something to say about the fiddly bits of the engines. F1 was an obsolete design and Raptor is cutting edge.

There're adversarial players in the scene nowadays with wider backs than Bezos. You don't need to care about these details if no one will have the guts to bring them to your attention.

I risk speculate that the reason we don't have footage of the engines at touch down may be related to whatever safety mechanism the engines (hypothetically) have.

Assuming, of course, that the mere contact from the engine's bells with the water would not do the trick itself - I wonder what would happen if all the engines would lighten up with the bells' mouths touching the water, the pressure would be enough to tear everything apart.

Edited Saturday at 04:24 AM by Lisias
Tyops, as usulla...

[JoeSchmuckatelli]

On 6/14/2024 at 8:19 PM, Lisias said:

mere contact from the engine's bells with the water

They don't want the hot, rapidly cooled bells... They want all the fiddly bits above the bell. 

Given that SX had a video of the Booster landing... I'm guessing they had the ability to recover or ensure sinkage. 

The big unknown is SS itself. 

 

[Lisias]

1 hour ago, JoeSchmuckatelli said:

They don't want the hot, rapidly cooled bells... They want all the fiddly bits above the bell. 

Humm... Yeah, reading now what I wrote, this is a possible interpretation. Language barrier is a sun on our beaches...

Allow me to try again.

Water is way more dense than air (obviously), so the pressure of the exhaust would eventually not be able to break free from the bell's mouth.

Something will have to give in, probably the bell's wall.

But this wall is probably stronger near the combustion chamber, right? 

If we have water enough in the bell, the water will protect the weaker parts of the wall from breaking. If the upper part of the bell is strong enough, the engine itself will be the one giving in - destroying exactly the interesting bits.

Edited Sunday at 05:47 AM by Lisias
tyops. as usulla.

[AckSed]

Robert Truax, designer of the famous Sea Dragon, did the Sea Horse tests as a prelude. Thanks to that, we know that rockets can be fired under water. The normal Raptors would probably survive their dunking. The Vacuum Raptors' bells might break off, as I'd imagine they'd be more fragile.

[darthgently]

7 minutes ago, AckSed said:

Robert Truax, designer of the famous Sea Dragon, did the Sea Horse tests as a prelude. Thanks to that, we know that rockets can be fired under water. The normal Raptors would probably survive their dunking. The Vacuum Raptors' bells might break off, as I'd imagine they'd be more fragile.

It would be interesting to know if they made any modifications to the engine or bell to accommodate the test.  If they had it would probably been classified given the era