SpaceX Starship : Texas Prototype(s) Thread 8 : Discussion

[envy887]

Mary's pictures this afternoon provide a nice view of the welded shut hatches to the fuel tanks...

Were those hatches into the tanks, or the areas in between the tanks?

The area between the tanks is only 1/4" thick.

[Norm38]

Can a cone be tiled with hexagons and pentagons, like a soccer ball?

[sdub]

Mary's pictures this afternoon provide a nice view of the welded shut hatches to the fuel tanks...

Were those hatches into the tanks, or the areas in between the tanks?

Into the tanks.  The only hatch that does not lead into a tank is the on the mk 1 lawn ornament, I mean, fairing.

[SkyRate]

Mary's pictures this afternoon provide a nice view of the welded shut hatches to the fuel tanks, quite the contrast from the Mk1 design.  I assume at some point that these would move back to a more accessible design for inspections, but the current design is not much more than a plate welded in.  Certainly faster to build and makes sense for a prototype when there is a decent chance you'll never have to open it again.

And an openable hatch would most likely not be circular for the same reason that manhole covers are circular.

[WormPicker959]

Can a cone be tiled with hexagons and pentagons, like a soccer ball?

So, I've been looking into this a little bit, and I'm not a mathematician or rocket scientist, but I believe the shape of the cone is known as a "spherically blunted tangent ogive". If that's the case, the curve of the nose should be that of circle, but only a part of it. This should not pose a problem for tiling, either with a "soccer ball" style or lots of other configurations (though none are only hexagons - they'll have to have another tile shape, it's not mathematically possible to tile a sphere with uniform hexagons, apparently). However, the segment of the circle is rotated around the diameter of the rocket... and the effect that has on the tiling will increase as the radius decreases. Presumably it's not an issue closer to the 9m region, as whatever worked for the other tiles will be acceptable. But near the top... I guess they'll have to have some special tiles?

In short, I've read enough to learn some new words and know that I don't have any idea how this will work, but I'm excited to see what they come up with.

[ShSch]

You cant tile a cone with hexagons... but do you have to?

You certainly can. As long as hexagons are not exactly regular and you don't worry about the very tip of the cone. Start with the bottom of the cone and put a row of hexagons side by side to complete the circumference, just as you would do with bricks. Then put the next row of slightly smaller hexagons on top (as you would do with bricks), and so on. Hexagons will be nearly regular and almost flat, but decrease in size as you progress.

In fact, a circular cone (or rather a part of it, if you care about the seam) can be easily tiled with regular hexagons of the same size: take a piece of paper, draw a regular hexagonal pattern on it, cut out a circular sector of an appropriate size, and roll it into a cone, just like you would construct a paper hat for a kids party. Now, SS fairing is not exactly a cone, so imagine you start with a rubber sheet instead of paper. After you make a rubber cone, stretch it a bit. Hexagons will stretch and deform as well, but remain hexagons.

Can a cone be tiled with hexagons and pentagons, like a soccer ball?

A cone can be tiled with absolutely anything. As long as you don't worry about regularity.

[meekGee]

You cant tile a cone with hexagons... but do you have to?

You certainly can. As long as hexagons are not exactly regular and you don't worry about the very tip of the cone. Start with the bottom of the cone and put a row of hexagons side by side to complete the circumference, just as you would do with bricks. Then put the next row of slightly smaller hexagons on top (as you would do with bricks), and so on. Hexagons will be nearly regular and almost flat, but decrease in size as you progress.

In fact, a circular cone (or rather a part of it, if you care about the seam) can be easily tiled with regular hexagons: take a piece of paper, draw a regular hexagonal pattern on it, cut out a circular sector of an appropriate size, and roll it into a cone, just like one constructs a paper hat for a kids party. Now, SS fairing is not exactly a cone, so imagine you start with a rubber sheet instead of paper. After you make a rubber cone, stretch it a bit. Hexagons will stretch and deform as well, but remain hexagons.

Can a cone be tiled with hexagons and pentagons, like a soccer ball?

A cone can be tiled with absolutely anything. As long as you don't worry about regularity.

If it's a real cone, then you can use regular hexagons, to a good approximation.

As long as the shape can be made from a simply bent sheet of metal (1 axis of curvature), then you can imagine pre-tiling it with regular hexagons, and then bending it...  The hexagons will have to bend out of plane, but they won't have to distort...  And this bending, over the size of tile, doesn't vary much, and can be accommodated by the studs.

Over the cone, the tiles will take on a "spiral" shape...  It will be beautiful.

The transition from cylinder to cone, however, will not be clean, tiling wise.

[Nevyn72]

Getting back to the assembly process, what I'm seeing here is very similar to an automotive production process.

The engine and tank section is the equivalent of the drivetrain.
The nose and cargo/passenger section is the equivalent of the body of a vehicle.

These are each mostly assembled separately and at some point in the manufacturing process are 'married' before final detailed assembly is completed.

Even though each section is largely a separate construction, once married they are not easily or practically split apart again.
The two 'halves' are an artifact of the construction process, not an operational feature. Thus there is no requirement for any type of 'quick connect' junctions between the top and bottom.

[geza]

You cant tile a cone with hexagons... but do you have to?

You certainly can. As long as hexagons are not exactly regular and you don't worry about the very tip of the cone. Start with the bottom of the cone and put a row of hexagons side by side to complete the circumference, just as you would do with bricks. Then put the next row of slightly smaller hexagons on top (as you would do with bricks), and so on. Hexagons will be nearly regular and almost flat, but decrease in size as you progress.

In fact, a circular cone (or rather a part of it, if you care about the seam) can be easily tiled with regular hexagons: take a piece of paper, draw a regular hexagonal pattern on it, cut out a circular sector of an appropriate size, and roll it into a cone, just like one constructs a paper hat for a kids party. Now, SS fairing is not exactly a cone, so imagine you start with a rubber sheet instead of paper. After you make a rubber cone, stretch it a bit. Hexagons will stretch and deform as well, but remain hexagons.

Can a cone be tiled with hexagons and pentagons, like a soccer ball?

A cone can be tiled with absolutely anything. As long as you don't worry about regularity.

If it's a real cone, then you can use regular hexagons, to a good approximation.

As long as the shape can be made from a simply bent sheet of metal (1 axis of curvature), then you can imagine pre-tiling it with regular hexagons, and then bending it...  The hexagons will have to bend out of plane, but they won't have to distort...  And this bending, over the size of tile, doesn't vary much, and can be accommodated by the studs.

Over the cone, the tiles will take on a "spiral" shape...  It will be beautiful.

The transition from cylinder to cone, however, will not be clean, tiling wise.

Unique shape of each tile was a headache for the Shuttle many decades ago. Maybe, it is not today in the era of CAD/CAM.

[sferrin]

You cant tile a cone with hexagons... but do you have to?

You certainly can. As long as hexagons are not exactly regular and you don't worry about the very tip of the cone. Start with the bottom of the cone and put a row of hexagons side by side to complete the circumference, just as you would do with bricks. Then put the next row of slightly smaller hexagons on top (as you would do with bricks), and so on. Hexagons will be nearly regular and almost flat, but decrease in size as you progress.

In fact, a circular cone (or rather a part of it, if you care about the seam) can be easily tiled with regular hexagons: take a piece of paper, draw a regular hexagonal pattern on it, cut out a circular sector of an appropriate size, and roll it into a cone, just like one constructs a paper hat for a kids party. Now, SS fairing is not exactly a cone, so imagine you start with a rubber sheet instead of paper. After you make a rubber cone, stretch it a bit. Hexagons will stretch and deform as well, but remain hexagons.

Can a cone be tiled with hexagons and pentagons, like a soccer ball?

A cone can be tiled with absolutely anything. As long as you don't worry about regularity.

If it's a real cone, then you can use regular hexagons, to a good approximation.

As long as the shape can be made from a simply bent sheet of metal (1 axis of curvature), then you can imagine pre-tiling it with regular hexagons, and then bending it...  The hexagons will have to bend out of plane, but they won't have to distort...  And this bending, over the size of tile, doesn't vary much, and can be accommodated by the studs.

Over the cone, the tiles will take on a "spiral" shape...  It will be beautiful.

The transition from cylinder to cone, however, will not be clean, tiling wise.

Unique shape of each tile was a headache for the Shuttle many decades ago. Maybe, it is not today in the era of CAD/CAM.

You wouldn't need anything like that degree of variety.

[awests]

I would bet that frost on the tanks starting at 12:39 local starship time is most likely from the depressurization from the GN2 test rather than the start of the LN2 test. The frost is very even across the entirety of the length of both tanks rather than starting at the bottom of each tank.

[warp99]

Mary's pictures this afternoon provide a nice view of the welded shut hatches to the fuel tanks...

Were those hatches into the tanks, or the areas in between the tanks?

The area between the tanks is only 1/4" thick.

5/32" or 4.0 mm

[DreamyPickle]

Having a large number of intricate tile shapes might not be a problem by itself as long as they don't require a manual repairs. Unlike on the Shuttle there is no chance of getting hit by debris during launch.

For tiling a rounded cone they could do it using the same slightly warped hexagon at each height point.

But they might eventually go for unique shapes of varying thickness anyway in order to optimize mass.

[Spock1108]

Is it plausible that they are spraying antifreeze to avoid ice formation during cryo tests?

[Slothman]

Is it plausible that they are spraying antifreeze to avoid ice formation during cryo tests?

Doubt it, it's not gonna stick on the surface for too long, especially once they start cryo testing. Water's going to condense on the surface. If it doesn't freeze, it's going to bead up and run off, taking the anti freeze with it. After a short time, ice is going to form anyways in that case.

In very cold conditions, when they spray anti freeze on airplanes, the plane needs to take off quickly after application because it's gonna freeze up if they wait too long without reapplying it.

[Keldor]

Having a large number of intricate tile shapes might not be a problem by itself as long as they don't require a manual repairs. Unlike on the Shuttle there is no chance of getting hit by debris during launch.

For tiling a rounded cone they could do it using the same slightly warped hexagon at each height point.

But they might eventually go for unique shapes of varying thickness anyway in order to optimize mass.

It's actually mathematically impossible to tile a rounded cone with any sort of uniform warped hexagon.  If you try it, you'll find that it works alright at the beginning, but as the surface continues curving, your hexagons will become more and more distorted until you're forced to add pentagons to the mix.  This is a direct consequence of the Euler Identity.

There's just no way to avoid requiring a large number of different tile shapes when trying to tile a surface with non-zero curvature.  (A cylinder has, mathematically speaking, zero curvature, just to be clear on this.  Not so for a rounded cone)

[DusanC]

Having a large number of intricate tile shapes might not be a problem by itself as long as they don't require a manual repairs. Unlike on the Shuttle there is no chance of getting hit by debris during launch.

For tiling a rounded cone they could do it using the same slightly warped hexagon at each height point.

But they might eventually go for unique shapes of varying thickness anyway in order to optimize mass.

It's actually mathematically impossible to tile a rounded cone with any sort of uniform warped hexagon.  If you try it, you'll find that it works alright at the beginning, but as the surface continues curving, your hexagons will become more and more distorted until you're forced to add pentagons to the mix.  This is a direct consequence of the Euler Identity.

There's just no way to avoid requiring a large number of different tile shapes when trying to tile a surface with non-zero curvature.  (A cylinder has, mathematically speaking, zero curvature, just to be clear on this.  Not so for a rounded cone)

Mathematically you're correct.

But engineers like to cheat

1 type of tile in 2 forms, whole and cut in half.

PS: I'd like to emphasize that only 200deg of SS needs to be tiled.

[Slothman]

Having a large number of intricate tile shapes might not be a problem by itself as long as they don't require a manual repairs. Unlike on the Shuttle there is no chance of getting hit by debris during launch.

For tiling a rounded cone they could do it using the same slightly warped hexagon at each height point.

But they might eventually go for unique shapes of varying thickness anyway in order to optimize mass.

It's actually mathematically impossible to tile a rounded cone with any sort of uniform warped hexagon.  If you try it, you'll find that it works alright at the beginning, but as the surface continues curving, your hexagons will become more and more distorted until you're forced to add pentagons to the mix.  This is a direct consequence of the Euler Identity.

There's just no way to avoid requiring a large number of different tile shapes when trying to tile a surface with non-zero curvature.  (A cylinder has, mathematically speaking, zero curvature, just to be clear on this.  Not so for a rounded cone)

Mathematically you're correct.

But engineers like to cheat

1 type of tile in 2 forms, whole and cut in half.

PS: I'd like to emphasize that only 200deg of SS needs to be tiled.

Does that work the same on a stronger curvature near the tip of the nose cone or will the vertical distance between the rows of half tiles be lower than 1 row?

[DusanC]

Having a large number of intricate tile shapes might not be a problem by itself as long as they don't require a manual repairs. Unlike on the Shuttle there is no chance of getting hit by debris during launch.

For tiling a rounded cone they could do it using the same slightly warped hexagon at each height point.

But they might eventually go for unique shapes of varying thickness anyway in order to optimize mass.

It's actually mathematically impossible to tile a rounded cone with any sort of uniform warped hexagon.  If you try it, you'll find that it works alright at the beginning, but as the surface continues curving, your hexagons will become more and more distorted until you're forced to add pentagons to the mix.  This is a direct consequence of the Euler Identity.

There's just no way to avoid requiring a large number of different tile shapes when trying to tile a surface with non-zero curvature.  (A cylinder has, mathematically speaking, zero curvature, just to be clear on this.  Not so for a rounded cone)

Mathematically you're correct.

But engineers like to cheat

1 type of tile in 2 forms, whole and cut in half.

PS: I'd like to emphasize that only 200deg of SS needs to be tiled.

Does that work the same on a stronger curvature near the tip of the nose cone or will the vertical distance between the rows of half tiles be lower than 1 row?

Limits of this "cheat" are defined by:
1. Size of tile
2. Allowed variation of gap between tiles.

So smaller tiles with larger gap can cover stronger curvature (smaller radius)

I'd need those 2 dimensions to say what's that radius but I presume with this cheat more than 95% of surface can be tiled, even more if we introduce  cutting of tiles with waterjet to different widths to cover corner cases.

To solve the problem of stronger curvatures I would introduce  2nd tile of the same type but smaller so that 3 small tiles can be placed on side of 1 larger tile

PS. Correction, 3 tiles on side.

PPS. Added sketch

[Sd-Snatcher]

Nobody remember Mk2