I was thinking for maybe up to 12 people or so - not multiple "Dragons" on one SS. Not substantially bigger than the Dragon that already exists, since it gets a bit tricky with having high acceleration for the ejection.
I'm a little confused: Are we talking about specific phases of abort (pad, boost, in-flight) or the entire profile? And what would be considered adequate for each phase?
Quote from: chopsticks on 05/27/2023 07:07 pmI was thinking for maybe up to 12 people or so - not multiple "Dragons" on one SS. Not substantially bigger than the Dragon that already exists, since it gets a bit tricky with having high acceleration for the ejection.That would be substantially different, both volume and mass. Suggest starting from scratch as it will not look like Dragon or current SS--at least from the tanks up. (And no, was not suggesting multiple Dragons; quite the opposite.) You have ~150t and ~1000m3 to work with. Optimize for people transport. If you have excess volume-mass beyond what is required for the projected number of passengers, feel free to allocate that to cargo.
Realistically within the next 10 years, say, how many people would you expect to fly on Starship at once? My assumption would be max 20 people. That doesn't make an ejectable capsule so hard, and should leave a decent amount of space in the rest of payload section for crew to do stuff....
Quote from: chopsticks on 05/27/2023 07:38 pmRealistically within the next 10 years, say, how many people would you expect to fly on Starship at once? My assumption would be max 20 people. That doesn't make an ejectable capsule so hard, and should leave a decent amount of space in the rest of payload section for crew to do stuff....Dunno. See assumptions-conjectures but little more. Please articulate why "That doesn't make an ejectable capsule so hard". Apologies, but this conversation is worthless unless you start bringing some facts to the table. Why do you think that and what is the basis for your opinion?
Quote from: joek on 05/27/2023 07:54 pmQuote from: chopsticks on 05/27/2023 07:38 pmRealistically within the next 10 years, say, how many people would you expect to fly on Starship at once? My assumption would be max 20 people. That doesn't make an ejectable capsule so hard, and should leave a decent amount of space in the rest of payload section for crew to do stuff....Dunno. See assumptions-conjectures but little more. Please articulate why "That doesn't make an ejectable capsule so hard". Apologies, but this conversation is worthless unless you start bringing some facts to the table. Why do you think that and what is the basis for your opinion?the burden of proof is on the proposer.Where's the math for the 6Gs of acceleration needed by the ~100t capsule, 10x bigger than prior capsules? How much solid propellant? How is it going to eject sideways in some scenarios and vertically in others?
\It's not 10x bigger than other capsules or 100 tonnes. As I said above, it's not fundamentally different from other capsules with LAS. It might have to be a bit bigger depending on the number of PAX (assuming max 12), but not that big.
Quote from: chopsticks on 05/27/2023 08:51 pm\It's not 10x bigger than other capsules or 100 tonnes. As I said above, it's not fundamentally different from other capsules with LAS. It might have to be a bit bigger depending on the number of PAX (assuming max 12), but not that big.If it is not 10x bigger than other capsules then you are wasting all the Starship mass potential for something that takes about $6B to develop and will have a market lifetime of less than 7 years.That is simply untenable. It's not even budgeted by SpaceX.
Also, I don't know that I agree with the idea that an abort system such as used by Dragon brings more complexity than it's worth. Obviously having any kind of an extra system is by definition more complex but is it really that much more? It might be subject to personal interpretation as to how one defines what is an okay level of complexity and what is too much. On Dragon for example, it uses hypergolics anyway for on orbit maneuvering. Tying in the superdracos into the same propellant system theoretically shouldn't be that much more complicated, no? (D2 explosion notwithstanding).Applying the same principle to my idea of an abort capsule on Starship would make it essentially a spacecraft that never separates (in nominal situations) from the second stage.Backing up a little—if TPS and hypergolic RCS are not needed and you forgo the lifeboat feature—you could probably get away with with some SRMs to activate the ejection and forego hypergolics entirely. Reorientation and control could use cold gas thrusters.
Quote from: Robotbeat on 05/26/2023 09:45 pm...So for low flight rate and unreliable launch vehicles, like every launch vehicle up until this point (with possible exception of the Falcon 9, especially if it actually continued flying at 100 times per year for another half decade or so without serious failures that would necessitate a high thrust LAS), LAS would improve overall safety, and be a clear safety advantage....Yes, thanks, got all that. Question still remains (to @Lee Jay's) point: What is safe enough?
...So for low flight rate and unreliable launch vehicles, like every launch vehicle up until this point (with possible exception of the Falcon 9, especially if it actually continued flying at 100 times per year for another half decade or so without serious failures that would necessitate a high thrust LAS), LAS would improve overall safety, and be a clear safety advantage....
Quote from: joek on 05/26/2023 10:15 pmQuote from: Robotbeat on 05/26/2023 09:45 pm...So for low flight rate and unreliable launch vehicles, like every launch vehicle up until this point (with possible exception of the Falcon 9, especially if it actually continued flying at 100 times per year for another half decade or so without serious failures that would necessitate a high thrust LAS), LAS would improve overall safety, and be a clear safety advantage....Yes, thanks, got all that. Question still remains (to @Lee Jay's) point: What is safe enough?1 in 500 for professional astronauts. 1 in 10 million for the general public.
Quote from: Lee Jay on 05/28/2023 03:12 am1 in 500 for professional astronauts. 1 in 10 million for the general public.GeneralPublic rides motorcycles and helicopters. We might be able to pick a public activity that’s a little more bold . For acceptable risk numbers.
1 in 500 for professional astronauts. 1 in 10 million for the general public.
Where did you come up with the 6 billion and why do think it would have a lifetime less than 7 years?
To match motorcycles you can have 30 fatalities per 100 million miles travelled. So around 4000 orbits. Or 250 days in orbit continuously.Or a fatality every 10 days.That seems achievable.
Quote from: MichaelBlackbourn on 05/28/2023 03:41 amTo match motorcycles you can have 30 fatalities per 100 million miles travelled. So around 4000 orbits. Or 250 days in orbit continuously.Or a fatality every 10 days.That seems achievable.The correct metric is fatalities per trip started, not per mile.All y'all posting random numbers need to do as nearly every science teacher and engineering teacher I've had has said: State your units.1:500 trips is good to start with, but for long term 1:10,000 trips is a reasonable expectation.
