totm nov 2023 SpaceX Discussion Thread

[tater]

 

 

 

[tater]

The fact that this thing is a flight article kinda blows my mind.

[sevenperforce]

They are lifting the nose cap into place right now.

Am I the only one rather extremely concerned about the tipping moment on those little legs? The ground spread is even smaller than on the 2017 IAC version.

[KSK]

8 hours ago, RealKerbal3x said:

I don’t understand why NASA are still essentially ignoring Starship when it’s so much more capable and so much cheaper than SLS - a rocket made from Shuttle leftovers that’s politically hanging in the balance. I guess, as @tater said a couple of pages back, that they’ll sit up and take notice when Starship delivers a payload to orbit before a single SLS has been assembled.

Because at the moment it’s a (very pretty) steel sculpture. When it actually reaches space NASA will start paying attention. 

I’m as excited to see the finished shell as the next SpaceX fan but let’s not get ahead of ourselves here.

[tater]

19 minutes ago, sevenperforce said:

They are lifting the nose cap into place right now.

Am I the only one rather extremely concerned about the tipping moment on those little legs? The ground spread is even smaller than on the 2017 IAC version.

Yes.

Very.

 

11 minutes ago, KSK said:

I’m as excited to see the finished shell as the next SpaceX fan but let’s not get ahead of ourselves here.

The lack of a crane means they actually welded it together, so I have to presume that it's more than just a shell. We know the header tanks have batteries, and I saw in one of the livestreams many wires going in the racetrack on one side. Clearly they have to attach all the things (climb inside with ladders?), that or they have to uninstall the nose... We'll see in a few days.

[magnemoe]

3 hours ago, Xd the great said:

What about the reentry aerodynamics? If 1 winglet/airbrake/plasma deflector shield fails, I doubt if Starship can reenter and land.

That part can be simulated well enough, note that loosing one or even both of the prototypes don't say starship don't work

[tater]

There's a bunch of room under the bottom dome/thrust structure, but I can't see how the legs can pop out and have a spread that isn't smaller than the fins and still direct the forces onto something strong.

Honestly, if Mk1 is supposed to fly a few times for data, I would have slapped giant F9 legs on the sides of this testbed vehicle, even if the goal was to remove them and replace with smaller ones later (as training wheels, basically).

[tater]

 

[ThatGuyWithALongUsername]

I rewatched the 2018 presentation and on the first Q&A question I noticed that Wlon actually mentioned the 6 legs/ 2 fins design being built now but went with the other one instead for what really sounded like solely aesthetic purposes. Just an interesting note. Shows that this design- minus stainless steel- isn't new.

10 minutes ago, tater said:

 

Note you can clearly see the landing legs in this picture!

Edited September 28, 2019 by ThatGuyWithALongUsername

[RealKerbal3x]

Anyone got pictures of the legs? I can’t seem to find any.

Thanks for adding that, @ThatGuyWithALongUsername! I’m not particularly familiar with Twitter and the way it crops images.

Edited September 28, 2019 by RealKerbal3x

[tater]

I wonder if the leg fairings get welded, or if the whole fairing moves with the leg...

This would allow a telescoping leg to move more laterally vs drawing a line from the tank bottom or thrust structure that grazes the bottom of that fairing. That would not be able to happen under the fins, however.

 

[RealKerbal3x]

Now that I look at them, those legs aren't too different from what was planned in 2017.

Also, it looks like the nose cap has been fitted:

[CatastrophicFailure]

4 hours ago, Scotius said:

As for the Starship - i fully expect it to fail. Probably in a very spectacular way It's a prototype after all - it's why we build them. Next one will be better.

This is how Starship will beat SLS into space and elsewhere, I think. SpaceX can afford to fail. They can afford to fail hard, and spectacularly, and as such are probably expecting it. And you learn more from failing. 

Regardless of funding, SLS must proceed at its snail’s pace because it absolutely cannot fail. Every single thing must be checked, checked, and umptoople-checked again such that any testing is only verifying whats’s already known. A major failure would be disastrous, a “liberated turbine wheel” on the test stand, even if the core isn’t a complete loss, could set the program back a year, or years. And if the core were lost at any point...

 

 

[CatastrophicFailure]

3 hours ago, tater said:

think that SS has every chance of completely obviating SLS, and I think it has a chance of doing so within the time frame of early Artemis missions. Does that mean SLS is cancelled? Nope. Does it mean that NASA would be fiscally incompetent to not use it for all launches for which it is best, even if it means not launching SLS at all?  Yeah,

See, now I have a very hard time envisioning a world where SLS and Starship coexist for any length of time. More-so SLS, Starship, and New Glenn. Just pulling numbers outta my patoot, Starship can do 90% of what SLS can for 10% of the cost. Even politically, i think it becomes very difficult to keep justifying that, especially if Starship is doing so once a month while SLS flies once a year. 

[tater]

3 minutes ago, CatastrophicFailure said:

See, now I have a very hard time envisioning a world where SLS and Starship coexist for any length of time. More-so SLS, Starship, and New Glenn. Just pulling numbers outta my patoot, Starship can do 90% of what SLS can for 10% of the cost. Even politically, i think it becomes very difficult to keep justifying that, especially if Starship is doing so once a month while SLS flies once a year. 

Starship won't have crew on it for a while, and SLS can launch Orion.

Government programs are not agile, and SLS/Orion is no exception. The only thing that kills SLS is politics. Everyone paying attention could agree 100% that it makes no sense, but if some doofus in Congress doesn't "get it" or doesn't care... it doesn't matter (it's not like politicians are smart).

 

Edited September 28, 2019 by tater

[Guest]

I watched a vid by Tim Dodd (I think I remembered his name) which went over a lot of reasons why the tripod with two windward flaps and one leeward leg was not ideal. Was pretty good and a lot of obvious things when pointed out which I hadn’t thought about before.

this spaceship much cooler imo (and quite possibly more passively stable) 

thank you KSP for giving me the familiarity with this stuff to appreciate irl things like starship better! :3

[Wjolcz]

I honestly didn't think they would have enough time to install those legs.

[tater]

6 minutes ago, Wjolcz said:

I honestly didn't think they would have enough time to install those legs.

Those are just the fairings, right? It sort of depends on how they do them. If fixed fairings, then finishing means cutting out a pass through behind them, then the legs telescope out from the bottom of the tank (look at the Elon tweet of raptors). Alternately, they could allow the legs more spread by not fixing the fairings to the hull, but fixing the fairings to the legs. Then the legs telescope out from the tank bottom, but flatter, taking the fairing with them. That can only really work with geometry that works with the smaller space under the fins doing this for the last 2 legs, however.

Depending on how thick they can make coaxial, telescoping legs, I guess it could be fairly far...

 

 

 

2-3 times the distance between the fairing and tank bottom.

[RCgothic]

I work in nuclear engineering. It's not actually very good engineering. Very reliable, but as far from cutting edge as you get. You get away with a lot of sins with a safety factor of x10 and no consideration of mass penalties. We can't afford to fail and so we don't learn much.

I bet SpaceX learns loads.

Edited September 28, 2019 by RCgothic

[Rakaydos]

8 minutes ago, RCgothic said:

I work in nuclear engineering. It's not actually very good engineering. Very reliable, but as far from cutting edge as you get. You get away with a lot of sins with a safety factor of x10 and no consideration of mass penalties. We can't afford to fail and so we don't learn much.

I bet SpaceX learns loads.

 

[tater]

Wonder if the SS 20km alt hop aims for JRTI, which is being refitted in Louisiana right now? The ASDS ships are about 50x90m, I wonder if they are adding any deck to it. Even in the event of a failure, they could possibly recover it for analysis (as per the failed landing in the video above).

[RealKerbal3x]

45 minutes ago, tater said:

Those are just the fairings, right? It sort of depends on how they do them. If fixed fairings, then finishing means cutting out a pass through behind them, then the legs telescope out from the bottom of the tank (look at the Elon tweet of raptors). Alternately, they could allow the legs more spread by not fixing the fairings to the hull, but fixing the fairings to the legs. Then the legs telescope out from the tank bottom, but flatter, taking the fairing with them. That can only really work with geometry that works with the smaller space under the fins doing this for the last 2 legs, however.

Attaching the fairings to the landing legs would be a good idea, because the legs would be able to spread out more (increasing the tipping moment) while still remaining protected during reentry. There is the downside of slightly increased complexity, but this idea does remind me of the landing legs on the 2016 ITS design, where the landing feet were part of their own aerodynamic fairing.

I guess we’ll have to wait and see what Elon says later.

[Wjolcz]

It's probably much safer to do the whole hop over the water. 

[kerbiloid]

Spoiler

If they put a droppable tank of liquid nitrogen onboard, they can safely land everywhere, on ice.

 

[CatastrophicFailure]

27 minutes ago, tater said:

Wonder if the SS 20km alt hop aims for JRTI, which is being refitted in Louisiana right now? The ASDS ships are about 50x90m, I wonder if they are adding any deck to it. Even in the event of a failure, they could possibly recover it for analysis (as per the failed landing in the video above).

 Eek to that. 

Even if the landing leg spread is much wider than we’ve seen, with something that tall and with great big sails at the very top, that seems like a recipe for disaster. Of the “wow, we really should have seen that coming” sort, not the “no one predicted this and we learned so much” sort. 

5 minutes ago, kerbiloid said:

  Hide contents

If they put a droppable tank of liquid nitrogen onboard, they can safely land everywhere, on ice.

 

Thermodynamics does not work like that. 

 They’d need to use liquid helium.