totm nov 2023 SpaceX Discussion Thread

[kerbiloid]

Spoiler

5 hours ago, tater said:

Am I the only one who keeps trying to use the . key on youtube to accelerate time?

In live streams?

 

[tater]

32 minutes ago, kerbiloid said:

  Hide contents

In live streams?

 

Yes, lol.

PS---on Roscosmos, ULA, and Arianespace launches with CGI instead of live pictures, I try and drag the view around reflexively, as well.

 

[Xd the great]

What will be the delta V of a starship (not the hopper) and the super heavy booster?

[tater]

A lot of fairings lying around.

[sevenperforce]

8 hours ago, tater said:

Roscosmos, ULA, and Arianespace launches with CGI instead of live pictures, I try and drag the view around reflexively, as well.

 

Guilty as charged.

 

In other news...

That was in commentary on this:

 

Spoiler

IT'S HAPPENING

I mean we knew that, but still.

It looks like there's one bulkhead there and another one in construction, with the pieces laying around it. This hopper is so f'in kerballed.

 

5 hours ago, Xd the great said:

What will be the delta V of a starship (not the hopper) and the super heavy booster?

Super Heavy is expected to stage the Starship somewhere between 1.8 and 2.5 km/s, with sufficient reserve to perform boostback, entry, and landing burns. Starship is expected to be able to complete orbital insertion with enough dV remaining for orbital maneuvers, deorbit, and landing. 

[sevenperforce]

If any hopper bulkhead is installed such that it is visible when the "cap" is off, we should be able to get a surprisingly good estimate of dV.

[Racescort666]

9 hours ago, tater said:

PS---on Roscosmos, ULA, and Arianespace launches with CGI instead of live pictures, I try and drag the view around reflexively, as well.

Back when I was playing KSP every day I would confuse KSP view controls with Solidworks/NX view controls

[zolotiyeruki]

41 minutes ago, Racescort666 said:

Back when I was playing KSP every day I would confuse KSP view controls with Solidworks/NX view controls

In my current job, I work with a good half dozen different CAD programs, and I swear every single one has its own unique set of camera controls.  It's really annoying.  Does middle click and drag zoom or pan this time?  Does right click and drag zoom, or does it rotate? Is it shift-middle-click-drag to rotate, or is that in a different program.  Grrr. 

[magnemoe]

3 hours ago, sevenperforce said:

Guilty as charged.

 

In other news...

That was in commentary on this:

 

  Hide contents

IT'S HAPPENING

I mean we knew that, but still.

It looks like there's one bulkhead there and another one in construction, with the pieces laying around it. This hopper is so f'in kerballed.

 

Super Heavy is expected to stage the Starship somewhere between 1.8 and 2.5 km/s, with sufficient reserve to perform boostback, entry, and landing burns. Starship is expected to be able to complete orbital insertion with enough dV remaining for orbital maneuvers, deorbit, and landing. 

This confuses me a bit. First they assemble the rocket then they make the fuel tanks for it. 
I assumed the hopper only had small header tanks. but this tanks are large even if they are just symmetry for bottom part and don't use common bulkhead. 
Did they not weld the thing together. If not its just to lift up the top. 

Piping is another issue, rocket engines uses a lot of fuel so it need serious piping and you need to take the oxidizer trough the fuel tank. Yes the manifold to the engines can be below the tank. not 5 pipes like on the saturn 5 first stage. That would be an bit confusing on the BFR first stage  
 

[sevenperforce]

33 minutes ago, magnemoe said:

This confuses me a bit. First they assemble the rocket then they make the fuel tanks for it. 
I assumed the hopper only had small header tanks. but this tanks are large even if they are just symmetry for bottom part and don't use common bulkhead. 
Did they not weld the thing together. If not its just to lift up the top. 

I assume the top is not welded together. NSF's L2 already confirmed they are using 9M tanks, so all they need are bulkheads. The hopper will have a LOT of dV, likely enough to go suborbital though they will not do so. Will likely use common bulkhead for simplicity.

The bulkhead shown has a hole in the center -- this may be a column for piping of methane down through the center of the LOX tank.

33 minutes ago, magnemoe said:

Piping is another issue, rocket engines uses a lot of fuel so it need serious piping and you need to take the oxidizer trough the fuel tank. Yes the manifold to the engines can be below the tank. not 5 pipes like on the saturn 5 first stage. That would be an bit confusing on the BFR first stage  

Elon said that the three engines currently in place are not flight articles, meaning that they are there only to test pipe fittings. So that implies that the piping is already completed and is simply hidden inside the lower portion of the vehicle.

[Rakaydos]

On 1/11/2019 at 8:41 AM, Xd the great said:

What if the ULA sniper hit it at T+1s?

Extra methane down the throat= more heat = more trouble.

Dont need a heat shield to abort on launch. "Sniper" is grounds for an abort, right?

[magnemoe]

20 minutes ago, sevenperforce said:

I assume the top is not welded together. NSF's L2 already confirmed they are using 9M tanks, so all they need are bulkheads. The hopper will have a LOT of dV, likely enough to go suborbital though they will not do so. Will likely use common bulkhead for simplicity.

The bulkhead shown has a hole in the center -- this may be a column for piping of methane down through the center of the LOX tank.

Elon said that the three engines currently in place are not flight articles, meaning that they are there only to test pipe fittings. So that implies that the piping is already completed and is simply hidden inside the lower portion of the vehicle.

OK tanks inside bulkhead, will the orbital use that or standard single layer hull with common bulkhead. You could run the cooling loops inside the tanks who would just hold gas during landing. But that would be running hot methane trough pipes in a tank holding pressurized and hot oxygen
Still you could add an extra layer on the inside. just in case. 

Read about the engines, they are just for fitting as you say. they might put on the cap to protect the inside also adding control systems and similar. 
But this will imply they will do the 6Km attitude jump with this. A bit weird they did not make it more like the orbital one for better data. A bit longer, fins more like the flight version and a static cancard? 
It should be pretty simple to do compared to that they have done. 

[Racescort666]

32 minutes ago, sevenperforce said:

Will likely use common bulkhead for simplicity.

Considering that Oxygen and Methane are liquid at approximately the same temperature, I'd say it improves simplicity.

[sevenperforce]

12 minutes ago, magnemoe said:

OK tanks inside bulkhead, will the orbital use that or standard single layer hull with common bulkhead.

The bulkhead is the tank. Well, it's the top of the tank. Elon has already confirmed that the Starhopper will use autogenous pressurization and monocoque tanks (i.e., the vehicle wall is the tank wall) just like the Starship. 

The fact that they installed non-flight article engines means they are testing attachments, which means the base of the vehicle is already airtight and plumbed. So they need two bulkheads: one concave-up bulkhead to separate LOX from CH4 (it needs a hole in the bottom to feed CH4 down to the engines) and a concave-down bulkhead to separate the top of the CH4 tank from the "cone" and all the flight computers, etc. 

My guess is that we see the concave-down bulkhead installed just above the level of the cylindrical portion of Starhopper.

12 minutes ago, magnemoe said:

You could run the cooling loops inside the tanks who would just hold gas during landing. But that would be running hot methane trough pipes in a tank holding pressurized and hot oxygen
Still you could add an extra layer on the inside. just in case. 

Starship will have some significant design changes in comparison to the 2017 IAC version and the 2018 #DearMoon version, so it's not yet certain how the header tanks will be arranged. One major LOCV vulnerability for the Starship is a non-catastrophic hull breach during ascent or entry. If SpaceX adds cylindrical tanks with valves between them, then it builds in the capacity to feed the Raptors from multiple tanks, thus reducing LOCV risk dramatically. It also allows for the possibility of using CoM shifts to control pitch during EDL.

12 minutes ago, magnemoe said:

Read about the engines, they are just for fitting as you say. they might put on the cap to protect the inside also adding control systems and similar. 
But this will imply they will do the 6Km attitude jump with this. A bit weird they did not make it more like the orbital one for better data. A bit longer, fins more like the flight version and a static cancard? 
It should be pretty simple to do compared to that they have done. 

They are only validating hover, approach, and landing. They may test pitchover with the Starhopper, but probably only to evaluate recovery modes in the event of a control surface failure a la CRS-16. They will use spent F9 upper stages to test feathered canard entry. Then they put those two datasets together to get what they need for the first Starship test article.

15 minutes ago, Racescort666 said:

Considering that Oxygen and Methane are liquid at approximately the same temperature, I'd say it improves simplicity.

LOX freezes at 54 K and boils at 90 K; CH4 freezes at 91 K and boils at 112 K. Better than kerolox, but still not ideal. 

This is one reason (out of several) why the lower tank will definitely be LOX; this way you can have warm oxygen gas autogenously pressurizing the lower tank just across the bulkhead from the liquid methane. Otherwise you have very warm methane gas in contact with the coldest LOX which is not great.

It does make concentric tanks challenging.

[sh1pman]

5 hours ago, sevenperforce said:

That was in commentary on this:

  

  Reveal hidden contents

IT'S HAPPENING

Mos Eisley Spaceport

[DDE]

40 minutes ago, sevenperforce said:

So they need two bulkheads

Well, they plan on it being reusable, so they can't use the Makeyev approach where there's only one dedicated bulkhead, with the bottom of the UDMH tank ís formed by a engine skirt while the top of the NTO tank is the next stage, engine included. That approach requires... gratuitous explosive separation.

Although it might explain why Makeyev is still chasing the DC-X-style SSTO, they cannot into non-destructive stage sep.

Edited January 14, 2019 by DDE

[magnemoe]

17 minutes ago, sevenperforce said:

The bulkhead is the tank. Well, it's the top of the tank. Elon has already confirmed that the Starhopper will use autogenous pressurization and monocoque tanks (i.e., the vehicle wall is the tank wall) just like the Starship. 

The fact that they installed non-flight article engines means they are testing attachments, which means the base of the vehicle is already airtight and plumbed. So they need two bulkheads: one concave-up bulkhead to separate LOX from CH4 (it needs a hole in the bottom to feed CH4 down to the engines) and a concave-down bulkhead to separate the top of the CH4 tank from the "cone" and all the flight computers, etc. 

My guess is that we see the concave-down bulkhead installed just above the level of the cylindrical portion of Starhopper.

Starship will have some significant design changes in comparison to the 2017 IAC version and the 2018 #DearMoon version, so it's not yet certain how the header tanks will be arranged. One major LOCV vulnerability for the Starship is a non-catastrophic hull breach during ascent or entry. If SpaceX adds cylindrical tanks with valves between them, then it builds in the capacity to feed the Raptors from multiple tanks, thus reducing LOCV risk dramatically. It also allows for the possibility of using CoM shifts to control pitch during EDL.

They are only validating hover, approach, and landing. They may test pitchover with the Starhopper, but probably only to evaluate recovery modes in the event of a control surface failure a la CRS-16. They will use spent F9 upper stages to test feathered canard entry. Then they put those two datasets together to get what they need for the first Starship test article.

LOX freezes at 54 K and boils at 90 K; CH4 freezes at 91 K and boils at 112 K. Better than kerolox, but still not ideal. 

This is one reason (out of several) why the lower tank will definitely be LOX; this way you can have warm oxygen gas autogenously pressurizing the lower tank just across the bulkhead from the liquid methane. Otherwise you have very warm methane gas in contact with the coldest LOX which is not great.

It does make concentric tanks challenging.

Looking at the upper parts it looks like sheet metal, yes the reflections make it look way more crumbled than it is, just as an 1 mm dent in a car shows very well, but still. 
Also they have some ducting on the upper part who includes ventilation tubing but was sealed off, still it can not go far up in the middle section. 
We agree on engines. 
Think they go for header tanks, it make sense for lots of reasons, on long missions you need to keep your your cryogenic fuel cryogenic. Yes tuning the system so you can land if the main tanks is breached also makes sense.
You have the option to aerobrake into orbit and await assistance, in this case being the first manned mission to Mars is an downer. 

[CatastrophicFailure]

18 minutes ago, DDE said:

Well, they plan on it being reusable, so they can't use the Makeyev approach where there's only one dedicated bulkhead, with the bottom of the UDMH tank ís formed by a engine skirt while the top of the NTO tank is the next stage, engine included. That approach requires... gratuitous explosive separation.

Um... source? 

[DDE]

49 minutes ago, CatastrophicFailure said:

Um... source? 

Sutton, backed by their own blueprints.

Believe it or not, there were also two distinct programs for R-29 upgrades, one working with Aluminol gel (UDMH+Al powder), which failed because it didn’t work with the one that fired the engine using ClF5 (according to Ignition!, Al powder doping works only with fluorine).

Edited January 14, 2019 by DDE

[sh1pman]

1 hour ago, DDE said:

Sutton, backed by their own blueprints.

Believe it or not, there were also two distinct programs for R-29 upgrades, one working with Aluminol gel (UDMH+Al powder), which failed because it didn’t work with the one that fired the engine using ClF5 (according to Ignition!, Al powder doping works only with fluorine).

They were doing part clipping before it was cool.

[Reactordrone]

With a common bulkhead you might end up with tanks something like this in the hopper,

That's assuming the upper dome is allowed to protrude into the upper aerodynamic section and a similar engine mount geometry to a Merlin.

 

Edited January 15, 2019 by Reactordrone

[sh1pman]

Does anyone know how they are going to pressurize the LOX tank? Gaseous methane, same as in LNG tank? Or boil some oxygen and use it to pressurize the tank?

Edited January 15, 2019 by sh1pman

[StrandedonEarth]

26 minutes ago, sh1pman said:

Does anyone know how they are going to pressurize the LOX tank? Gaseous methane, same as in LNG tank? Or boil some oxygen and use it to pressurize the tank?

Methane and oxygen in the same tank is a ticking time bomb. The slightest spark would make the Challenger accident look like a bottle rocket. 

I understand autogenous pressurization to mean that each tank will be pressurized with its own gasses, heated by the engines. 

[sh1pman]

15 minutes ago, StrandedonEarth said:

Methane and oxygen in the same tank is a ticking time bomb. The slightest spark would make the Challenger accident look like a bottle rocket. 

Very likely, but not 100% sure about that. At near-cryogenic temperatures, with almost pure gaseous methane over liquid oxygen, it may just not ignite.

There's typically a range of gas proportions that gives explosion when ignited. Outside of that range, the mix can slowly burn or not ignite at all. And at lower temperatures most chemical reactions run slower, or may even become energetically unfavorable and thus not happen at all. That's why I wasn't so sure. You're probably still right, though.

(That's how my Chemistry degree makes me think a bit too heavily about obvious things)

Edited January 15, 2019 by sh1pman

[StrandedonEarth]

7 minutes ago, sh1pman said:

Very likely, but not 100% sure about that. At near-cryogenic temperatures, with almost pure gaseous methane over liquid oxygen, it may just not ignite.

There's typically a range of gas proportions that gives explosion when ignited. Outside of that range, the mix can slowly burn or not ignite at all. And at lower temperatures most chemical reactions run slower, or may even become energetically unfavorable and thus not happen at all. That's why I wasn't so sure. You're probably still right, though.

(That's how my Chemistry degree makes me think a bit too heavily about obvious things)

Well, I would think the gas needs to be fairly hot to provide pressure, which would vaporize some oxygen, although probably not in the right proportions to detonate.

(but hey, I'm only a washed-up failed engineering student, so I could easily be wrong. But then, NASA didn't see anything wrong with pressurizing a capsule with pure oxygen to an absolute pressure of ~19 psi either)