Can anyone been tell if they are using a common dome or if there are 2 independent tank domes?
"Moreso than any other single part, the most confusing aspect of Starhopper has to be the apparent condition of its steel tank domes, distinctly covered with a patina of impurities like rust, dirt, dust, and grime." https://www.teslarati.com/spacex-starship-hopper-tank-bulkhead-installation-launch-landing-pad-progress/Could they be planning to use cryogenic bladders inside the rough, dirty steel tanks?
Quote from: strato1 on 01/22/2019 10:01 amCan anyone been tell if they are using a common dome or if there are 2 independent tank domes?Images from yesterdays drone footage seem to show a common bulkhead.
This pic was taken on 1-16-19 when the large sections were being moved. A couple sections had some pieces of lumber on them. So perhaps it was a piece of lumber that fell?
Quote from: meekGee on 01/22/2019 03:01 amWell there's still a bunch of stuff laying around.- The top dome (and its cap)- the arced members near the top dome (maybe its interface stiffener to the cylinder?)- Some 3' tubes- anything else?I must have missed something, thats what you get for traveling I guess.1: Do we know its a common bulkhead design to begin with? The hopper doesnt need top notch mass efficiency. I must have missed that info.2: If it is a common bulkhead design, why does everyone assume that whats inside the hopper is a common bulkhead? Wouldnt it make sense to have a few meters of engine space and above that the tanks? Would fit with what we see.
Well there's still a bunch of stuff laying around.- The top dome (and its cap)- the arced members near the top dome (maybe its interface stiffener to the cylinder?)- Some 3' tubes- anything else?
Quote from: Semmel on 01/22/2019 07:41 amQuote from: meekGee on 01/22/2019 03:01 amWell there's still a bunch of stuff laying around.- The top dome (and its cap)- the arced members near the top dome (maybe its interface stiffener to the cylinder?)- Some 3' tubes- anything else?I must have missed something, thats what you get for traveling I guess.1: Do we know its a common bulkhead design to begin with? The hopper doesnt need top notch mass efficiency. I must have missed that info.2: If it is a common bulkhead design, why does everyone assume that whats inside the hopper is a common bulkhead? Wouldnt it make sense to have a few meters of engine space and above that the tanks? Would fit with what we see.We don't know it's a common bulkhead, but pixel counting shows:1. The water tower part of the hopper body is 12m high2. The dome is about 3m high3. The dome inside the water tower has its edge ~3m away from the water tower upper edge4. This leaves 6m between the lowest point of the dome and the lower edge of the water towerSo:1. If it's not common bulkhead design, and we're seeing the lower dome for the upper tank, then the lower tank only has 6m to use, even if we put two dome next to each other for the lower tank, the lower dome of the lower tank would be at level with water tower's lower edge, there wouldn't be space for engines.2. If we're seeing is the lower dome of a common bulkhead design, its lowest point is 6m away from the water tower's lower edge, that seems to be way too much space just for the thrust structure and engines.
Quote from: CuddlyRocket on 01/22/2019 08:08 amQuote from: Semmel on 01/22/2019 07:41 am3. Why build such a large tinfoil hat if there is nothing in it?They're testing the aerodynamics of the shape?I doubt it will ever go fast enough that anything interestingly aerodynamic will ever happen with this rocket. If anything I see it as practise. They can't leave the top open or flat, and if they're going to design some some sort of dome or cone to cover it, it may as well be close to the eventual article.
Quote from: Semmel on 01/22/2019 07:41 am3. Why build such a large tinfoil hat if there is nothing in it?They're testing the aerodynamics of the shape?
3. Why build such a large tinfoil hat if there is nothing in it?
Quote from: meekGee on 01/22/2019 03:01 amWell there's still a bunch of stuff laying around.- The top dome (and its cap)- the arced members near the top dome (maybe its interface stiffener to the cylinder?)- Some 3' tubes- anything else?I must have missed something, thats what you get for traveling I guess.1: Do we know its a common bulkhead design to begin with? The hopper doesnt need top notch mass efficiency. I must have missed that info.2: If it is a common bulkhead design, why does everyone assume that whats inside the hopper is a common bulkhead? Wouldnt it make sense to have a few meters of engine space and above that the tanks? Would fit with what we see.3. Why build such a large tinfoil hat if there is nothing in it?
Quote from: Semmel on 01/22/2019 07:41 amQuote from: meekGee on 01/22/2019 03:01 amWell there's still a bunch of stuff laying around.- The top dome (and its cap)- the arced members near the top dome (maybe its interface stiffener to the cylinder?)- Some 3' tubes- anything else?I must have missed something, thats what you get for traveling I guess.1: Do we know its a common bulkhead design to begin with? The hopper doesnt need top notch mass efficiency. I must have missed that info.2: If it is a common bulkhead design, why does everyone assume that whats inside the hopper is a common bulkhead? Wouldnt it make sense to have a few meters of engine space and above that the tanks? Would fit with what we see.3. Why build such a large tinfoil hat if there is nothing in it?After finding out that the tanks are full diameter, I think it's turning out that as much as practical was made "life like". This is not a minimalist test platform designed to have "most show for the buck".The is a maximalist test platform, subject to certain constraints.I think the entire "ass end" of the rocket - tanks, engines, pressurization system - all of that will be functionally representative of the real thing.I would not be surprised if there are side thrusters.We know that high-speed flight is out, and with it, movable brakerons. We know anything forward of the tanks is just a thin shell.We suspect that nothing much will attach inside the shell, though structurally it may be possible to build a floor or some other construction anchored to the bottom tube and extending into the shell.
Quote from: su27k on 01/22/2019 10:33 amQuote from: Semmel on 01/22/2019 07:41 amQuote from: meekGee on 01/22/2019 03:01 amWell there's still a bunch of stuff laying around.- The top dome (and its cap)- the arced members near the top dome (maybe its interface stiffener to the cylinder?)- Some 3' tubes- anything else?I must have missed something, thats what you get for traveling I guess.1: Do we know its a common bulkhead design to begin with? The hopper doesnt need top notch mass efficiency. I must have missed that info.2: If it is a common bulkhead design, why does everyone assume that whats inside the hopper is a common bulkhead? Wouldnt it make sense to have a few meters of engine space and above that the tanks? Would fit with what we see.We don't know it's a common bulkhead, but pixel counting shows:1. The water tower part of the hopper body is 12m high2. The dome is about 3m high3. The dome inside the water tower has its edge ~3m away from the water tower upper edge4. This leaves 6m between the lowest point of the dome and the lower edge of the water towerSo:1. If it's not common bulkhead design, and we're seeing the lower dome for the upper tank, then the lower tank only has 6m to use, even if we put two dome next to each other for the lower tank, the lower dome of the lower tank would be at level with water tower's lower edge, there wouldn't be space for engines.2. If we're seeing is the lower dome of a common bulkhead design, its lowest point is 6m away from the water tower's lower edge, that seems to be way too much space just for the thrust structure and engines.And the common and separate bulkhead theories both seem to have spacing issues.
The problem is if what we're seeing is the common bulkhead (i.e. lower dome of the LOX tank), and assuming the top dome goes above the triangular support beams, the LOX tank volume would be too large. If the tank height is 2.2m (0.8m between top of the beam to top edge of the hopper), dome volume 92m^3 (truncated cone, h=3, R=4.5, r=1.5 (3m top hole)), this gives total LOX volume of 324m^3, or 369t of LOX. Total propellant load would be 471t, that just leaves 29t of structure mass if we assume liftoff T/W of 1.2.
Do you know if the composite tank in LA was just a test article?https://www.teslarati.com/spacex-bfr-spaceship-prototype-tank-dome-complete-hop-tests/
Quote from: su27k on 01/22/2019 01:09 pmThe problem is if what we're seeing is the common bulkhead (i.e. lower dome of the LOX tank), and assuming the top dome goes above the triangular support beams, the LOX tank volume would be too large. If the tank height is 2.2m (0.8m between top of the beam to top edge of the hopper), dome volume 92m^3 (truncated cone, h=3, R=4.5, r=1.5 (3m top hole)), this gives total LOX volume of 324m^3, or 369t of LOX. Total propellant load would be 471t, that just leaves 29t of structure mass if we assume liftoff T/W of 1.2.What if they don't top off the tanks? You have just established an upper bound for the propellant load, after all.
Quote from: jpo234 on 01/22/2019 01:28 pmQuote from: su27k on 01/22/2019 01:09 pmThe problem is if what we're seeing is the common bulkhead (i.e. lower dome of the LOX tank), and assuming the top dome goes above the triangular support beams, the LOX tank volume would be too large. If the tank height is 2.2m (0.8m between top of the beam to top edge of the hopper), dome volume 92m^3 (truncated cone, h=3, R=4.5, r=1.5 (3m top hole)), this gives total LOX volume of 324m^3, or 369t of LOX. Total propellant load would be 471t, that just leaves 29t of structure mass if we assume liftoff T/W of 1.2.What if they don't top off the tanks? You have just established an upper bound for the propellant load, after all.Yes, they can certainly do that, I guess that's what they did when flying Grasshopper. Although it would be a bit strange if they build a tank without using it to its full potential.