totm nov 2023 SpaceX Discussion Thread

[sevenperforce]

5 minutes ago, tater said:

For a crew version, I think the payload penalty of a LAS is totally unconcerning.

How many people at once does one need to send to space? Use the abort-capable version to send people to LEO. Dock with a crew vehicle in orbit, and take them to the Moon (wherever). The crew vehicle can aerobrake to LEO, discharge passengers into the abort-capable version, then do EDL.

At least until they get some 100s or 1000s of consecutive, perfect landings.

Yeah, if all these insane plans work and "propellant costs only" is really a thing, then you can totally have an abort-capable Starship separate from your BLEO Starship. 

But it won't work for P2P.

[tater]

9 minutes ago, sevenperforce said:

But it won't work for P2P.

Yeah, but to get people to take a P2P ride, they'll need to have shown a gajillion successful flights. Right now we're more likely to be killed by CNSA booster debris than in an airline crash, getting people to take P2P rides is gonna be hard.

[mikegarrison]

58 minutes ago, sevenperforce said:

But it won't work for P2P.

P2P is never going to happen, so don't worry about it.

[sevenperforce]

37 minutes ago, mikegarrison said:

P2P is never going to happen, so don't worry about it.

I know that, and you know that, and @tater knows that, but apparently neither Elon nor Gwynne know that, so we have to assume they will make decisions based on that.

[tater]

42 minutes ago, mikegarrison said:

P2P is never going to happen, so don't worry about it.

What, people don't think a 1:X-hundred chance of death is not what they want for their family vacation needs?

 

4 minutes ago, sevenperforce said:

I know that, and you know that, and @tater knows that, but apparently neither Elon nor Gwynne know that, so we have to assume they will make decisions based on that.

True enough.

Personally, I'd not only want to see thousands of such flights in a row with no problems, I'd like to see edge case problems happen—and they land OK anyway. Even then, I'd be wary, maybe wait til I was really old anyway, so that the chance of death was not high compared to my chance of death.

Edited March 5, 2021 by tater

[kerbiloid]

Spoiler

If some new virus requires new vaccine to be urgently delivered to many places of the world, a fleet of P2P Starships could be tested in thousands of flights...

Just thoughts, just thoughts...

P.S.
Btw, totally unrelated, do they have a biological research department for the Martian colony?

 

Edited March 5, 2021 by kerbiloid

[GarrisonChisholm]

On 2/25/2021 at 11:03 AM, Dfthu said:

Not even space mountain at disney? 

I still read that in Ahnold's voice.

[Clamp-o-Tron]

31 minutes ago, kerbiloid said:

  Hide contents

 

P.S.
Btw, totally unrelated, do they have a biological research department for the Martian colony?

 

They probably have a little bit of colony dev, but not much. I would assume that they are working on the Sabatier reactor and its power system, as they’re working to produce fuels at Boca Chica, and Shotwell made some offhand comment a while ago about how hard it was to get nuclear material for what I assume was at the time something similar to kilopower.

Probably a good idea not to give SpaceX uranium.

[mikegarrison]

It's not even the safety issue. (Or really, the many, many safety issues.)

It's economics. There is no way that Starship could possibly be economically competitive with something like a 787. Even if it were perfectly safe, it would be so ridiculously expensive that nobody would fly on it. The people who have unlimited money have private planes anyway, and would probably rather spend 12 hours in their plane than fly crammed into a Starship with 100 other people. And the people who don't have unlimited money -- well, they don't have unlimited money.

[tater]

5 hours ago, mikegarrison said:

It's not even the safety issue. (Or really, the many, many safety issues.)

It's economics. There is no way that Starship could possibly be economically competitive with something like a 787. Even if it were perfectly safe, it would be so ridiculously expensive that nobody would fly on it. The people who have unlimited money have private planes anyway, and would probably rather spend 12 hours in their plane than fly crammed into a Starship with 100 other people. And the people who don't have unlimited money -- well, they don't have unlimited money.

Again (to be clear) I'm not in the P2P camp.

It's not 100 people, more like 500-800 people. SS has the habitable volume of an A380. and they don't have any need to move around on a 28 minute flight (particularly when they are contemplating their rapidly approaching disassembly ).

Their math must be that prop costs are in the hundreds of thousands of $ (800k is a number that sticks in my head). If they had 600 passengers, and it cost 6M/flight, that's 10k$/seat cost (tickets are + whatever markup is). If launch cost 2M$, then it's a $3333/seat cost. If the launch cost is $800,000, then the seat cost to SpaceX is ~$1333.

Shotwell has said the cost to passengers would be about like "economy plus." I just checked and LAX/Sydney return is $2800+ for premium economy, so in that ballpark.

And yes, I think they'll land on Mars long before people fly rockets P2P.

 

(that's meant to show how unlikely I think it is )

[kerbiloid]

If the flight costs 6 mln USD, then some crazy billionaire can just spend 1 bln on 150 cargo flights from some poor world region to another one, just to get the safety history to ensure others.

If make the cargo bay pressurized, but leave a secret hatch to it in the gear compartment, he will have a hundred of test volunteers sneaked inside.
It's important to have it sealed, warmed, and with soft airbags inside, to prevent potential injuries.

Then he celebrate the "10 000th passenger" day and start selling tickets.

[sevenperforce]

Okay, so this is definitely my favorite Starship leg concept yet.

More:

Spoiler

 

 

[mikegarrison]

3 hours ago, tater said:

It's not 100 people, more like 500-800 people. SS has the habitable volume of an A380.

I'll believe that when I see it. So far Starship has a "habitable volume" of 0 m³.

Also, the world record for reusable spaceships is still 39 flights. Airplanes fly every day for 20-30 years, and you still can't just ignore capital costs when considering their economics.

[magnemoe]

2 hours ago, tater said:

Again (to be clear) I'm not in the P2P camp.

It's not 100 people, more like 500-800 people. SS has the habitable volume of an A380. and they don't have any need to move around on a 28 minute flight (particularly when they are contemplating their rapidly approaching disassembly ).

Their math must be that prop costs are in the hundreds of thousands of $ (800k is a number that sticks in my head). If they had 600 passengers, and it cost 6M/flight, that's 10k$/seat cost (tickets are + whatever markup is). If launch cost 2M$, then it's a $3333/seat cost. If the launch cost is $800,000, then the seat cost to SpaceX is ~$1333.

Shotwell has said the cost to passengers would be about like "economy plus." I just checked and LAX/Sydney return is $2800+ for premium economy, so in that ballpark.

And yes, I think they'll land on Mars long before people fly rockets P2P.

(that's meant to show how unlikely I think it is )

Main cost is probably not fuel but the launch platform or the aircraft carrier for 120 meter high rockets. Call it aircraft carrier here as it has to do the same functions with starship as an carrier do to its jets. 
One issue might well be filling them, they ending the production of A380 and the 474 will also wind down because point to point flight are more popular, granted starship is fast but you have to get to the port then an boat out, board and strap in, launch, land and reverse the process. Yes probably more comfortable and fun than an 12 hour flight you might well have to fly to the spaceport and to destination. A bit like the concord problem. 
This ignores the safety and that its an ballistic missile. 
Starship would make an very good bomber by the way. 3 times an B 52 payload and payload arrive at orbital velocity. 

[tater]

1 hour ago, mikegarrison said:

I'll believe that when I see it. So far Starship has a "habitable volume" of 0 m³.

Also, the world record for reusable spaceships is still 39 flights. Airplanes fly every day for 20-30 years, and you still can't just ignore capital costs when considering their economics.

Like I said, I don't see P2P as being a thing. I was merely explaining the math they must have done. 100 people aboard was the number they talk about for Mars.

Also, obviously capital costs matter, so you'd have to look at the total number of flights, the actual cost of the vehicle, and factor that in. Shotwell said that it would be less than business class price wise, more than economy, so work backwards from there.

I too will believe it when I see it.

(and not before)

 

[RyanRising]

2 hours ago, sevenperforce said:

Okay, so this is definitely my favorite Starship leg concept yet.

More:

  Hide contents

 

 

Splitting the skirt would require a lot of reinforcement, but if there’s anything to be learned from all the shots people have been giving the landing legs, something’s probably got to give. Splitting the skirt in this way doesn’t necessitate a heatshield seam and provides an alternative path (around the covers) for the load to take. All the moving parts does make me a little nervous, but overall I just wish I had the sort of imagination you do.

Would it be feasible to have six of these, with two coming out from under the rear flaps and the appropriate modifications made to those flaps’ and aerocovers’ shapes? Or does that mean you’ve got a severe gap in the heatshield again? Maybe it would be desirable to have them clocked so that one faces directly windward and leeward?

Edited March 5, 2021 by RyanRising

[sevenperforce]

26 minutes ago, RyanRising said:

Splitting the skirt would require a lot of reinforcement, but if there’s anything to be learned from all the shots people have been giving the landing legs, something’s probably got to give. Splitting the skirt in this way doesn’t necessitate a heatshield seam and provides an alternative path (around the covers) for the load to take.

The current landing legs fold out onto the same points that are used to hold onto Starship while it is sitting on the pad. Presumably if you split the heat shield like this you would make the stowed-position feet themselves the hold-down points.

26 minutes ago, RyanRising said:

Would it be feasible to have six of these, with two coming out from under the rear flaps and the appropriate modifications made to those flaps’ and aerocovers’ shapes? Or does that mean you’ve got a severe gap in the heatshield again? Maybe it would be desirable to have them clocked so that one faces directly windward and leeward?

I don't know if they could manage six or not. Four seems like plenty.

[Meecrob]

3 hours ago, sevenperforce said:

Okay, so this is definitely my favorite Starship leg concept yet.

More:

  Hide contents

 

 

I hate to be a downer, but that looks absolutely massive! I suspect the final design will be much closer to aircraft landing gear with minimal actuators (amount in total, as well as size of) and a lot more straight pieces of metal with control horns on them.  I also suspect the auto-levelling feature will involve a ratcheting design as opposed to active hydraulic control.

Edited to add: No, I do sound like a downer...seriously man, I love that you toss your ideas out there!

Edited March 5, 2021 by Meecrob

[sevenperforce]

2 minutes ago, Meecrob said:

I hate to be a downer, but that looks absolutely massive! I suspect the final design will be much closer to aircraft landing gear with minimal actuators (amount in total, as well as size of) and a lot more straight pieces of metal with control horns on them. 

Oh, it is clearly way, way too large. No question about that. I was just trying to design it in KSP which is inherently difficult since I don't have Tweakscale installed.

3 minutes ago, Meecrob said:

I also suspect the auto-levelling feature will involve a ratcheting design as opposed to active hydraulic control.

Using active hydraulic control for auto-leveling allows shock absorbers to also be the auto-levelers. The best part is no part.

[RyanRising]

3 minutes ago, sevenperforce said:

I don't know if they could manage six or not. Four seems like plenty.

With four legs, if there's a problem with one of them you most likely tip. It's a little more avoidable with active levelling, since you can try to tip it over onto the three remaining, but still less redundant. With six legs there are scenarios in which one just fails to deploy entirely yet you'd be fine on landing, while pointing straight up. It also allows for sixfold or trifold symmetry again, allowing the same three vacuum raptors they've planned for the normal Starship (yeah, not great for pulling the ship off the top in case of an abort, but that's not exactly a confidence-inspiring abort mode anyway), and probably six vacuum raptors for the upgraded refuelling Starship that may or may not come to pass.

[sevenperforce]

14 minutes ago, RyanRising said:

With four legs, if there's a problem with one of them you most likely tip. It's a little more avoidable with active levelling, since you can try to tip it over onto the three remaining, but still less redundant. With six legs there are scenarios in which one just fails to deploy entirely yet you'd be fine on landing, while pointing straight up. It also allows for sixfold or trifold symmetry again, allowing the same three vacuum raptors they've planned for the normal Starship (yeah, not great for pulling the ship off the top in case of an abort, but that's not exactly a confidence-inspiring abort mode anyway), and probably six vacuum raptors for the upgraded refuelling Starship that may or may not come to pass.

There might be enough space for six.

One thing is that with this wide stance, though, you'd have to have a complete failure to not have SOME kind of support on that end.

[sevenperforce]

So I actually went back to the drawing board and rebuilt this in KSP with the proper dimensions (using 3.5 meter parts instead of 5 meter parts) and....

......I cannot believe how well it works.

Like, it works REALLY well. Amazing shock absorption. I put a single Vector underneath and was able to do a 150 meter hop perfectly the first time with no problem whatsoever.

 

[Elthy]

Did anyone figure out how big those bulges on the renders are, e.g. with pixel counting? Its hard to imagine both pistons and the feet themself fitting in there, under a cover of heatshield tiles. But with the huge scale of starship it might be enough...

Actualy, why couldnt they mount such a thin mechanism on the inside of the skirt, thus needing no extra shielding? Seems more simple and i cant imagine that the space is that constrained they have to go on the outside.

[tater]

12 minutes ago, Elthy said:

Actualy, why couldnt they mount such a thin mechanism on the inside of the skirt, thus needing no extra shielding? Seems more simple and i cant imagine that the space is that constrained they have to go on the outside.

Yeah, there could be perforations under the bulges, it need not be an entire break in the skirt.

[sevenperforce]

6 minutes ago, Elthy said:

Did anyone figure out how big those bulges on the renders are, e.g. with pixel counting? Its hard to imagine both pistons and the feet themself fitting in there, under a cover of heatshield tiles. But with the huge scale of starship it might be enough...

Actualy, why couldnt they mount such a thin mechanism on the inside of the skirt, thus needing no extra shielding? Seems more simple and i cant imagine that the space is that constrained they have to go on the outside.

It's a surprisingly compact solution. Like I said, I was able to do it in actual KSP without any clipping.

But trying to move them inside the skirt is actually really tough. There are enough internal parts to make it a challenging fit. And you lose more of the wide stance than you would think.