Author Topic: SpaceX Starship/Super Heavy Engineering General Thread 5  (Read 93182 times)

Online Lee Jay

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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #120 on: 12/04/2023 07:44 pm »
They could also jack up the top section and insert more tower under the top.  (Much the same way as they build some tower cranes)

Still have the 400ft issue.

But then there's the Elon way.  Just build it up and wait for the FAA to challenge him and Elon will eventually get his way and the FAA will change their rule to satisfy NASA's needs to get this ship flying.   ::)
Can you explain the issue?  Just getting a permit?  It's not like taller buildings are rare...

The tower is already 480 feet, right?

I've personally installed 435 foot towers, about 5 miles from an airport.  You just fill out an application, answer so questions and light it.  No big deal.

Online Lee Jay

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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #121 on: 12/04/2023 07:46 pm »
They could also jack up the top section and insert more tower under the top.  (Much the same way as they build some tower cranes)

Still have the 400ft issue.

But then there's the Elon way.  Just build it up and wait for the FAA to challenge him and Elon will eventually get his way and the FAA will change their rule to satisfy NASA's needs to get this ship flying.   ::)
Can you explain the issue?  Just getting a permit?  It's not like taller buildings are rare...

FAA prohibits mounted structures above 399 feet, otherwise, it impacts air traffic (la,la,la).  I'm looking for a reference. 

Most modern wind turbines are much taller than that to the top of the rotor.

There's no such rule.  There are just rules about what you have to do at certain heights.  The cutoffs I remember are 200 (below which you don't need lighting) and 500 (above which you need another process).

Online catdlr

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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #122 on: 12/04/2023 07:54 pm »
They could also jack up the top section and insert more tower under the top.  (Much the same way as they build some tower cranes)

Still have the 400ft issue.

But then there's the Elon way.  Just build it up and wait for the FAA to challenge him and Elon will eventually get his way and the FAA will change their rule to satisfy NASA's needs to get this ship flying.   ::)
Can you explain the issue?  Just getting a permit?  It's not like taller buildings are rare...

The tower is already 480 feet, right?

I've personally installed 435 foot towers, about 5 miles from an airport.  You just fill out an application, answer so questions and light it.  No big deal.

Sorry, it's 499 feet. I made a correction to my previous post. It's being discussed in L2.

So the proposal to add an additional 10 meters would pass the 499 rule from the current 480 ft (Thanks LeeJay).
« Last Edit: 12/04/2023 07:56 pm by catdlr »
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Offline meekGee

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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #123 on: 12/04/2023 07:55 pm »


Sorry it's 499 feet. I made a correction to my previous post. It's being discussed in L2.

quote]Can you explain the issue?  Just getting a permit?  It's not like taller buildings are rare...
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Online catdlr

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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #124 on: 12/04/2023 08:00 pm »


Sorry it's 499 feet. I made a correction to my previous post. It's being discussed in L2.

quote]Can you explain the issue?  Just getting a permit?  It's not like taller buildings are rare...

You would think, right? I'm not the one involved in the discussion on the other thread. I simply recall the conversation; I'm just relaying the message. Let's refocus on SH engineering and address the tower issue where it should be discussed. Apologies for bringing it up here.
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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #125 on: 12/04/2023 08:12 pm »
Regarding making the tower taller - I'm not sure that it's even possible to do that. The columns are all filled with concrete, and I believe they were filled from the bottom up in segments. Really doubt that they're going to do this.

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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #126 on: 12/04/2023 08:33 pm »
Regarding making the tower taller - I'm not sure that it's even possible to do that. The columns are all filled with concrete, and I believe they were filled from the bottom up in segments. Really doubt that they're going to do this.

Good point. 

I had initially suggested that the top section of the tower, which was delivered from Robert's Road, should be assembled on top of the existing tower. Then, at an appropriate time, the draw works holding the chopsticks would be reconfigured to utilize the pulleys on the new upper section. The pulleys and the structure supporting them from the current tower top would be removed, resulting in a taller tower. This process would be carried out gradually, except for the final re-cabling. This approach would avoid the need to dismantle the existing tower top and insert another level, especially considering that a section of it has already been encased in cement.

There is also the chain cable encasing all the electrical wiring from the tower to the chopsticks that travel up and down with it. I have no idea if that can be stretched out further than it goes out now or if it means adding additional links and rewiring for the extra length it needs to travel and the guideway for the trollies may need to be extended. So many considerations for a tower expansion, that's why I decided to drop and go to moving the ball and socket using the chopsticks catching the SS be lowered to accommodate the current tower height and chopsticks limitations. But lowering the SS catch points may prove to be problematic with lowering the SS center of Gravity.
« Last Edit: 12/04/2023 08:42 pm by catdlr »
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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #127 on: 12/05/2023 02:09 am »
Surely moving the catch/attachment point lower down would have a negligible effect on the CG, no? Those attachment points can't weigh very much. Unless you're referring to more instability while lifting and catching? Even then, the CG is going to be lower than halfway down due to the heavy engines. Making this modification to Starship vs raising the tower seems almost like a no-brainer to me.

Offline Nomadd

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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #128 on: 12/05/2023 02:25 am »
Sorry it's 499 feet. I made a correction to my previous post. It's being discussed in L2.

Can you explain the issue?  Just getting a permit?  It's not like taller buildings are rare...

 It's about assumptions. The 499' tower was assumed to be not a problem, but somebody could have contested it if it would have caused trouble. 500' feet, and the assumption goes away. SpaceX has to go through extra paperwork and studies to prove it won't be a problem.
 It's similar to the oft quoted, inaccurate claim that you can't build over 2,000 feet. You can, but the burden of proof shifts. And it's a whole lot harder to prove that something is safe than to prove it's dangerous.
 That was poorly worded, but talkin purdy never was my strong point.
« Last Edit: 12/06/2023 02:17 pm by Nomadd »
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Online DanClemmensen

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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #129 on: 12/05/2023 02:33 am »
Surely moving the catch/attachment point lower down would have a negligible effect on the CG, no? Those attachment points can't weigh very much. Unless you're referring to more instability while lifting and catching? Even then, the CG is going to be lower than halfway down due to the heavy engines. Making this modification to Starship vs raising the tower seems almost like a no-brainer to me.
Yes, the CoM will surely be below the lift points sufficiently to assure stability, but you you must at least consider it. I think the assumption is that you need to consider an SS with a pre-loaded maximum cargo, which for an expended launch can be as high as 250 tonne, and probably higher since stretching the SS will probably allow for heavier payload. This won't be a problem for the two primary candidates for stretch: Tanker and Depot, because their cargo gets loaded after stacking.

Online FutureSpaceTourist

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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #130 on: 12/16/2023 08:35 pm »
twitter.com/ringwatchers/status/1736134983750688948

Quote
Supplying the 33 Raptors on Super Heavy with propellant is not a small task, and our new article explains in detail how the propellant distribution system works, featuring real photos and renders. Check it out!

🔗->

https://ringwatchers.com/article/booster-prop-distribution

https://twitter.com/ringwatchers/status/1736134985365492070

Quote
Below is a cutaway diagram of the distribution system.
« Last Edit: 12/16/2023 09:52 pm by FutureSpaceTourist »

Offline litton4

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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #131 on: 12/17/2023 04:58 pm »
Fantastic read - only possible since so many of the components have been photographed just "lying around outside".

I'm guessing that in the not too distant future, a lot of this will happen out of sight inside Starfactory......:(
« Last Edit: 12/17/2023 04:58 pm by litton4 »
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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #132 on: 12/19/2023 06:59 pm »
I like downcommer idea so much. :D Appeared almost instantly in Chica i imagined in mine head. Yeah at least 1 yr behind space X engineers haha

Online TheRadicalModerate

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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #133 on: 12/19/2023 08:50 pm »

Quote from: Ringwatchers
Supplying the 33 Raptors on Super Heavy with propellant is not a small task, and our new article explains in detail how the propellant distribution system works, featuring real photos and renders. Check it out!

https://ringwatchers.com/article/booster-prop-distribution


Has anyone at SpaceX used the term "landing tank" for the headers, or is that just Ringwatchers' assumption?  ISTM that the header makes more sense for staging, flip, and early boostback, but as soon as the prop is settled, they'd go back to using the mains.  Landing should occur with the prop well-settled, and should also be doable using the mains.

One thing they didn't describe is how the LOX header gets ullage pressurization.  If they're confident that ullage collapse isn't a problem in the mains, then just venting the top of the header to the main works fine.  If post-slosh ullage collapse is a problem, then things have to be a bit more exotic.

The other issue is how to keep prop in the downcomer during the flip.  They either need a funny baffle or a big honkin' check valve.

Update:  One piece of evidence that the headers actually are landing tanks is that the LOX feeders for the middle 10 engines exit the header so high up.  If the header were for staging / rotation / early boostback, you'd want to use all the header prop to get all 13 engines running before switching back to the mains.  But that can't happen with those feeders where they are.  (Why are they there?  Surely they're not structural, are they?)

On the other hand, you don't care about the middle 10 engines at landing.

Not sure if this kills my theory, but it sure puts a dent in it.
« Last Edit: 12/20/2023 05:13 am by TheRadicalModerate »

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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #134 on: 12/20/2023 06:45 am »
https://twitter.com/tibininin/status/1737285726704726123

Quote
now guess which one is more powerfull

https://twitter.com/tibininin/status/1737320752494338398

Quote
The original purpose of making it was to show the size difference between n-1 and starship, i just ended up putting more in

Offline Robotbeat

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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #135 on: 12/20/2023 07:09 am »
N-1 is indeed huge, but I think perspective is messing with the Saturn V comparison. Plus, starship’s engine section is more like 10m in diameter.
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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #136 on: 12/20/2023 07:14 am »
N-1 is indeed huge, but I think perspective is messing with the Saturn V comparison. Plus, starship’s engine section is more like 10m in diameter.

I can hear Elon saying that N-1 has room for a lot more engines.

« Last Edit: 12/21/2023 04:56 am by catdlr »
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Online TheRadicalModerate

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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #137 on: 12/21/2023 04:51 am »
It would've been nice if the Ringwatchers article or diagrams had come with some dimensions and volumes.  Since it didn't, I did a horrible set of glorified pixel-counting. (I used Powerpoint to overlay rectangles to find the inner and outer dimensions of the actual tankage at various points, then turned them into "washer-like" volumes.  Yes, I am aware that I'm a dinosaur.)

The results, assuming I didn't mess something up, are kinda weird.

Downcomer¹ + sump volume:  19.0m³
LOX header volume: 32.4m³

LCH4 mass, assuming subcooled density of 448kg/m³:  8.5t
LOX mass, assuming subcooled density of 1232kg/m³: 39.9t
O:F mixture:  4.7

The mixture is obviously wrong. 

A good reason why that might be the case is that, while the LOX header is a genuine header, the LCH4 sump + downcomer isn't.  As such, it will refill as soon as the prop settles, providing enough fuel to completely use the LOX.

If we take the 39.9t of "headerized" LOX, O:F=3.6 means that we need 11.1t of LCH4 to go with it, which gives us a nice round number of 50.0t of total prop.  That's nowhere near enough delta-v to handle staging, flip, mains setting, boostback, and landing.  But it is enough to handle everything but the bulk of boostback, which can be handled from the (settled) mains.

Another way to gain some insight into this is to think of how many engine-seconds of flight 50t of prop will provide.  If we assume Raptor 2 performance (230tf @ Isp=327), each engine will consume about 700kg/s of prop.²  Our 50t of prop will therefore provide 71 engine-seconds of propulsion at 100% throttle.

Let's make a guess at how many engine-seconds the following header-based maneuvers require:

Throttledown to staging:  3 engines @ 50% for 5 seconds:  7.5 engine-seconds
Flip / mains settling: 3 engines @ 100% for 10 seconds: 15 engine-seconds
Boostback:  Handled by mains
Landing: 3 engines @ 50% for 30 seconds:  45 engine-seconds
Total: 67.5 engine-seconds

These are obviously SWAGs, but they come out pretty close to the actual mass flow that the LOX header can provide.  Not exactly conclusive evidence, but worth thinking about.

_______
¹Based on the dimensions in the picture, the downcomer, from main sump to the bottom of the "header" sump, appears to be 36.8m x 0.6m.  Also, note that I didn't measure the volume of the feeder lines coming out of the tanks.  They're probably non-trivial, but the errors will be fairly small.

I'm maybe 85% confident I did the volume computation right.  I'd love it if somebody could confirm it.


²These numbers are good for computing mass flow, but remember that everything but landing occurs in near-vacuum conditions, which will goose both the thrust and Isp.  But the mass flow should stay roughly constant.

Offline edzieba

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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #138 on: 12/21/2023 12:54 pm »
Alternatively, the diagrams are illustrative and not to scale. Drawing volumetric conclusions from non-dimensioned fan-art is rarely going to produce results that reflect reality.

Offline wannamoonbase

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Re: SpaceX Starship/Super Heavy Engineering General Thread 5
« Reply #139 on: 12/21/2023 02:00 pm »
N-1 is indeed huge, but I think perspective is messing with the Saturn V comparison. Plus, starship’s engine section is more like 10m in diameter.

I can hear Elon saying that N-1 has room for a lot more engines.



Or, there should be a 17 meter Starship.
Wildly optimistic prediction, Superheavy recovery on IFT-4 or IFT-5

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