totm nov 2023 SpaceX Discussion Thread

[cubinator]

Per the Inspiration4 raffle rules, Crew Dragon's astronaut height limit seems to be 6'6". This is three inches better than the Shuttle.

[sevenperforce]

This may be how they solve the curvature problem.

21 minutes ago, cubinator said:

Per the Inspiration4 raffle rules, Crew Dragon's astronaut height limit seems to be 6'6". This is three inches better than the Shuttle.

Guess I'm good then.

[RuBisCO]

31 minutes ago, sevenperforce said:

This may be how they solve the curvature problem.

Guess I'm good then.

Yes but only on the tube part, not the nose cone where specially sized parts are need to close the pattern. 

[sevenperforce]

16 minutes ago, RuBisCO said:

Yes but only on the tube part, not the nose cone where specially sized parts are need to close the pattern. 

The "tube" part can be covered entirely with equally-sized hex tiles. The smaller tiles account for the gaps to close the pattern around the cone.

[RuBisCO]

Just now, sevenperforce said:

The "tube" part can be covered entirely with equally-sized hex tiles. The smaller tiles account for the gaps to close the pattern around the cone.

Oh I did not see that there was smaller ones there, neet

[magnemoe]

26 minutes ago, sevenperforce said:

This may be how they solve the curvature problem.

Guess I'm good then.

Don't see how smaller tiles solve it. You will get gaps and as you move up even the smaller tiles will start getting in each other way. 
The benefit of starship shape over the shuttle is that starship is an much simpler geometric. An  cylinder going over to an pointed dome at the front. You also have the joins and the raceway for the flaps.  Downside with the hexagonal is that they are not very good for an pointed dome.  Yes you can make them narrower at the top but then the next layer will not fit and you need an new type of tiles on each layer up. With square tiles in layers upward you don't care much if diameter become shorter you just use fewer tiles until you reach the nose who probably need other times as it curves so much. 

[JoeSchmuckatelli]

1 hour ago, cubinator said:

Per the Inspiration4 raffle rules, Crew Dragon's astronaut height limit seems to be 6'6". This is three inches better than the Shuttle.

Well, I'm out. 

 

 

Tanks are bigger than space ships, it seems 

14 minutes ago, magnemoe said:

Don't see how smaller tiles solve it. You will get gaps and as you move up even the smaller tiles will start getting in each other way. 
The benefit of starship shape over the shuttle is that starship is an much simpler geometric. An  cylinder going over to an pointed dome at the front. You also have the joins and the raceway for the flaps.  Downside with the hexagonal is that they are not very good for an pointed dome.  Yes you can make them narrower at the top but then the next layer will not fit and you need an new type of tiles on each layer up. With square tiles in layers upward you don't care much if diameter become shorter you just use fewer tiles until you reach the nose who probably need other times as it curves so much. 

Yeah - the fish scale tiles I referenced earlier look like an elegant solution - one that preserves a non-linear aspect 

[sevenperforce]

2 minutes ago, JoeSchmuckatelli said:

Yeah - the fish scale tiles I referenced earlier look like an elegant solution - one that preserves a non-linear aspect 

Here's how trapezoidal tiles would look. It works quite well, really.

Spoiler

In the lower, purely conical section, I showed how the tiles can be slightly staggered to avoid any hypersonic flow path between tiles. I didn't stagger them in the properly curved/ogive section because it was waaaaay too complex, but the same thing is also possible there. 

If the gaps in the purely conical section are too severe, you can accomplish the same effect by alternately flipping the trapezoids like this:

Spoiler

 

[magnemoe]

48 minutes ago, sevenperforce said:

In the lower, purely conical section, I showed how the tiles can be slightly staggered to avoid any hypersonic flow path between tiles. I didn't stagger them in the properly curved/ogive section because it was waaaaay too complex, but the same thing is also possible there. 

If the gaps in the purely conical section are too severe, you can accomplish the same effect by alternately flipping the trapezoids like this:

  Hide contents

 

Now this is genial, Simply one piece, as you say you can offset to avoid vertical lines, you get horizontal one but not sure if this is an major problem, if it is its solvable with a bit more complex design and two more tile types. 

[sevenperforce]

39 minutes ago, magnemoe said:

Now this is genial, Simply one piece, as you say you can offset to avoid vertical lines, you get horizontal one but not sure if this is an major problem, if it is its solvable with a bit more complex design and two more tile types. 

There's a horizontal line but it can be fixed by slightly offsetting the upper rings in the same way as the lower ones. It was just too complex a shape to do in Sketchup easily.

[RealKerbal3x]

SN10 did what looked like a cryo proof test. It seemed short, not sure if it was successful or not.

Also, flight TFRs already:

 

[sevenperforce]

2 hours ago, magnemoe said:

Don't see how smaller tiles solve it. You will get gaps and as you move up even the smaller tiles will start getting in each other way. 
The benefit of starship shape over the shuttle is that starship is an much simpler geometric. An  cylinder going over to an pointed dome at the front. You also have the joins and the raceway for the flaps.  Downside with the hexagonal is that they are not very good for an pointed dome.  Yes you can make them narrower at the top but then the next layer will not fit and you need an new type of tiles on each layer up.

If you have two single differently-sized tiles, you can combine them to create dozens of shapes that tesselate around an ogive cone:

Obviously I didn't actually nose-over the curvature here but you can see the principle. 

[kerbiloid]

It should be fractal, to fit the surface perfectly.

Spoiler

 

[EimajOzear]

17 hours ago, tater said:

It needs to be one every few million departures to be "airline level" safety, so it needs to be 10,000X safer than crew Dragon. That's a high %$@#in bar—and SpaceX talks about Point to Point. Mass use of rockets for P2P, or even mass flights of people into space requires a sense of safety that is substantially higher than 1:270.

Refreshing to see this as I just finished explaining to someone on Youtube how airline failure rates are unlikely to be achieved any time soon given the nature of rocket engines.

Here are some excerpts for anyone who wants a more grounded and evidence-based approach to Starship and the current state of reliability in spaceflight:

Spoiler

"...for the simple case of when 1 engine failure is allowed, you would require a Raptor failure rate of 0.535% to achieve the 100 consecutive successful flights (99.01% success rate)"
"Alright, so at a 2% Raptor failure rate, we get a 89.25% success rate if allowing for 1 engine out event for the Super Heavy (28 x Raptor SL) and a 99.88% success rate for the Starship (3 x Raptor vac), multiplying them together gets us 89.15% for the whole launch. At this rate, you would expect around 11 MISSION failures in every 100 launches. Also, keep in mind this does not include the landing burns for both vehicles, but based on a quick analysis I did, this does not incur much of a penalty to the overall success rate, possibly only causing 1-2 extra failures per 100 flights." ~ the 2% Raptor reliability rate came from the other commenter, but is similar to current Merlin reliability, so I didn't change it.

"How Many Engines Should a Rocket Have?" by Geoffrey Landis is a great resource for anyone else wanting to do their own sums relating to engine reliability.

[RCgothic]

With 1 engine out allowed on ascent and landing, at 2% chance of failure per burn the Starship upper stage would have a 99.4% chance of successful ascent (6 failures in 1000) on 6 engines and a 99.9% chance of a successful landing on 3 engines. That's 7 failures in 1000 due to engines.

With 4 engines out allowed on ascent, the Superheavy booster, the Superheavy booster has a 99.98% chance of successful ascent. That's 2 failures in 10,000.

Loss of crew due to engines would therefore be 72 in 10,000 missions.

The booster landing on 4 engines would land successfully (up to 1 engine out) 99.77% of the time. ~25 lost boosters total ascent and landing per 10,000 flights.

 

If the engines are more reliable than 2% chance of failure then things improve a lot. Merlin 1D has flown 110 (990 engines) missions with 2 engine failures on ascent. Failures during static fire/landing are unknown and therefore excluded. That's 0.2%.

If Raptor can achieve Merlin level reliability of 2 failures in 990, then Superheavy might be expected to fail 24 in a million landings and suffer no failed ascents. The Starship upper stage would suffer critical engine related failures on 72 of a million flights.

 

That's not a very long way off where it needs to be TBH. In 1960 Boeing alone suffered over 40 accidents per million flights. Sure, engines are not everything that can go wrong with a rocket, but they are the most critical.

[sevenperforce]

Here's the tesselation pattern to tile an ogive for two hex tiles of the same ratio as the ones on SN10:

You use the smaller tiles to slowly add gaps and then you build the larger tiles back in. The pattern repeats infinitely and gives you a flawless ogive.

[Guest]

I think this might be the place to ask, but does anyone know where this image comes from? It looks like an ITS with three side boosters

[RealKerbal3x]

1 hour ago, The Doodling Astronaut said:

I think this might be the place to ask, but does anyone know where this image comes from? It looks like an ITS with three side boosters

Pretty sure that's from the Axel Springer awards event, when the award was given to Elon. It's not an actual design, just a stage prop designed by someone unfamiliar with rockets.

[mikegarrison]

1 hour ago, The Doodling Astronaut said:

I think this might be the place to ask, but does anyone know where this image comes from? It looks like an ITS with three side boosters

Those *could* be side boosters, I guess. They kind of look more like a certain part of the male anatomy, though.

[kerbiloid]

Launched from a ramp...

[coyotesfrontier]

6 hours ago, The Doodling Astronaut said:

I think this might be the place to ask, but does anyone know where this image comes from? It looks like an ITS with three side boosters

Super Heavy Heavy!

[tater]

6 hours ago, mikegarrison said:

Those *could* be side boosters, I guess. They kind of look more like a certain part of the male anatomy, though.

Maybe their familiarity with rockets came from watching Blue Origin videos?

[kerbiloid]

It looks strangely familiar...

https://translate.google.com/translate?hl=ru&sl=ru&tl=en&u=https://www.buran.ru/htm/str124.htm

Spoiler

MTK-VP, Buran's competitor.

Do they follow all buran.ru illustrations in their tests?

[tater]

17 minutes ago, kerbiloid said:

Do they follow all buran.ru illustrations in their tests?

Some early NASA Shuttle concepts were actually similar to that from the late 60s and early 70s.

Spoiler

1969^

^1969

 

 

 

[RealKerbal3x]

BN1 thrust dome sleeved. It's plumbed in for 4 Raptors.