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It's a fascinating problem. I'd like to see the lunar version go very wide stance to be honest.

heck, initial Mars versions as well, though yesterday's hard landing was surprisingly stable minus legs at all (unless the ~3 that deployed stabbed into the concrete like lawn darts :D).

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7 minutes ago, tater said:

It's a fascinating problem. I'd like to see the lunar version go very wide stance to be honest.

heck, initial Mars versions as well, though yesterday's hard landing was surprisingly stable minus legs at all (unless the ~3 that deployed stabbed into the concrete like lawn darts :D).

I think the spreading of the aft flaps helped with stability actually.

Here's how a three-piston ITS-style solution might work.

 

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I watched the LabPadre and Everyday Astronaut footage. I wonder, how much pressure is that fuel and LOX under? Cause SS was really thrown into the air.

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9 minutes ago, sevenperforce said:

Here's how a three-piston ITS-style solution might work.

For the narrow stance versions, I like that one a lot. But I mean a WIDE stance.

1970s_boeing_lunar_ferry_by_paul_lloyd_d

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10 minutes ago, SOXBLOX said:

I watched the LabPadre and Everyday Astronaut footage. I wonder, how much pressure is that fuel and LOX under? Cause SS was really thrown into the air.

It was the kaboom that launched it in the air, not the 3 bar of ullage pressure. The kaboom was probably 100 bar or more.

2 minutes ago, tater said:

For the narrow stance versions, I like that one a lot. But I mean a WIDE stance.

 

Spoiler

1970s_boeing_lunar_ferry_by_paul_lloyd_d

 

Beautiful, but for Starship definitely a non-starter.

Over at NSF people are discussing launch abort systems for Starship, which has always been an issue because despite the vehicle's excellent payload, the nose section is SO large that a functioning abort system would really cut into your mass budget.

And then someone came up with what has to be the best solution I have heard yet.

Quote

What if you had launch escape in the form of hybrid puller rockets in the nose which drew from the LOX header tank but were otherwise made of a storable solid rubber fuel?

That's.......tremendous.

Rubber or plasticized petrol for the fuel, the existing LOX header tank for the oxidizer, pyro torches for instant ignition. Hybrids have remarkably good TWR and can use differential throttling, vectored nozzles, or both to provide pointing. Detcord just above the top of the methane tank for separation. It separates with its forward flaps, which assist in maintaining a heading until escape engine shutoff.

Multiple large chutes deploy from explosively-jettisoned panels under the LOX head tank and the aft of the fairing provides several meters of crumple zone for a survivable, if unpleasant, landing.

Not good enough for P2P, of course.......but absolutely good enough for a 10-person crew.

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16 minutes ago, sevenperforce said:

Beautiful, but for Starship definitely a non-starter.

Sorry, I meant Lunar Starship.

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22 minutes ago, Brotoro said:

Will the final versions of Starship have the LOX header tank in the tip of the nose, or is that just an arrangement for the protypes?

I think it was up there to pull the centre of mass towards the nose a bit, so if that's right then you'd still want it for at least cargo and refuelling Starships that land empty. But I don't have any sources for that.

 

56 minutes ago, sevenperforce said:

It was the kaboom that launched it in the air, not the 3 bar of ullage pressure. The kaboom was probably 100 bar or more.

Beautiful, but for Starship definitely a non-starter.

Over at NSF people are discussing launch abort systems for Starship, which has always been an issue because despite the vehicle's excellent payload, the nose section is SO large that a functioning abort system would really cut into your mass budget.

And then someone came up with what has to be the best solution I have heard yet.

"What if you had launch escape in the form of hybrid puller rockets in the nose which drew from the LOX header tank but were otherwise made of a storable solid rubber fuel? "

That's.......tremendous.

Rubber or plasticized petrol for the fuel, the existing LOX header tank for the oxidizer, pyro torches for instant ignition. Hybrids have remarkably good TWR and can use differential throttling, vectored nozzles, or both to provide pointing. Detcord just above the top of the methane tank for separation. It separates with its forward flaps, which assist in maintaining a heading until escape engine shutoff.

Multiple large chutes deploy from explosively-jettisoned panels under the LOX head tank and the aft of the fairing provides several meters of crumple zone for a survivable, if unpleasant, landing.

Not good enough for P2P, of course.......but absolutely good enough for a 10-person crew.

Ooooh, I love that. Quick, someone tell me why it's unworkable!

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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.

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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.

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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.

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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.

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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 by tater
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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 by kerbiloid
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31 minutes ago, kerbiloid said:
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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.

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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.

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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 ;) )

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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.

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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.

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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. 

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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)

 

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2 hours ago, sevenperforce said:

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

More:

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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 by RyanRising
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