There is an older thread for a "realistic near-term rotating space station".
Quote from: DreamyPickle on 11/07/2017 05:10 pmThere is an older thread for a "realistic near-term rotating space station".blerg... I got halfway through the thread before I got fed up with the arguments about NASA, artificial gravity research, and mars programs.The earlier argument about needing a rigid (compressed) component to dampen oscillation in a tensioned tether was at least useful.
Quote from: rakaydos on 11/08/2017 03:47 amQuote from: DreamyPickle on 11/07/2017 05:10 pmThere is an older thread for a "realistic near-term rotating space station".blerg... I got halfway through the thread before I got fed up with the arguments about NASA, artificial gravity research, and mars programs.The earlier argument about needing a rigid (compressed) component to dampen oscillation in a tensioned tether was at least useful.I'm happy to let the older threads die, since BFR seems like a much more likely vehicle (and SpaceX a much more likely partner company) to facilitate spin-gravity habitat research. I've been somewhat quieter of late because I've been working on Exodus Space Systems, the Australian space startup company I co-founded to deal with exactly these problems.I'm attaching here an excerpt from our vision/strategy document, which I think provides a good summary of the various considerations that spin gravity proposals should take into account. Hopefully it should be useful to some of the newer participants, but I'd also appreciate feedback - particularly if you think I've missed anything.
Quote from: mikelepage on 11/09/2017 03:41 amQuote from: rakaydos on 11/08/2017 03:47 amQuote from: DreamyPickle on 11/07/2017 05:10 pmThere is an older thread for a "realistic near-term rotating space station".blerg... I got halfway through the thread before I got fed up with the arguments about NASA, artificial gravity research, and mars programs.The earlier argument about needing a rigid (compressed) component to dampen oscillation in a tensioned tether was at least useful.I'm happy to let the older threads die, since BFR seems like a much more likely vehicle (and SpaceX a much more likely partner company) to facilitate spin-gravity habitat research. I've been somewhat quieter of late because I've been working on Exodus Space Systems, the Australian space startup company I co-founded to deal with exactly these problems.I'm attaching here an excerpt from our vision/strategy document, which I think provides a good summary of the various considerations that spin gravity proposals should take into account. Hopefully it should be useful to some of the newer participants, but I'd also appreciate feedback - particularly if you think I've missed anything.One order of magnitude reduction in cost can be expected in the next 5-10 years. Not multiple orders of magnitude. 2 at most a long time from now.John
One order of magnitude reduction in cost can be expected in the next 5-10 years. Not multiple orders of magnitude. 2 at most a long time from now.
Quote from: livingjw on 11/11/2017 02:50 pmOne order of magnitude reduction in cost can be expected in the next 5-10 years. Not multiple orders of magnitude. 2 at most a long time from now.I assume this means you don't believe that passenger transport at close to the stated goals will come about ever?
Quote from: lamontagne on 11/05/2017 03:31 pmComplete station. 48 modules. About 36 000 m3 of space. Hi is that based on https://en.wikipedia.org/wiki/BA_2100 or similar?It looks like you are putting new doors through the inflatable section and including a sizeable new cylindrical join to that section.IMO you would use the two doors that come at each end of the BA2100, connected to the central rigid part. You would only need a small adaption to one end so that when they joined end to end they formed a curve. Cables to the center could connect to this adaption also.
Complete station. 48 modules. About 36 000 m3 of space.
Quote from: KelvinZero on 11/07/2017 08:42 amQuote from: lamontagne on 11/05/2017 03:31 pmComplete station. 48 modules. About 36 000 m3 of space. Hi is that based on https://en.wikipedia.org/wiki/BA_2100 or similar?It looks like you are putting new doors through the inflatable section and including a sizeable new cylindrical join to that section.IMO you would use the two doors that come at each end of the BA2100, connected to the central rigid part. You would only need a small adaption to one end so that when they joined end to end they formed a curve. Cables to the center could connect to this adaption also.No its based on a rigid module optimized to fit inside the BFS fairing.
I was just thinking about estimating some values for my telescoping idea.I think I can work out the basic mass per volume from something like thishttps://en.wikipedia.org/wiki/Pressure_vessel#Cylindrical_vessel_with_hemispherical_endsWhat is a sensible, non Sci-Fi material choice? What should I use for density and maximum working stress? What should I use for pressure?
Quote from: speedevil on 11/11/2017 06:42 pmQuote from: livingjw on 11/11/2017 02:50 pmOne order of magnitude reduction in cost can be expected in the next 5-10 years. Not multiple orders of magnitude. 2 at most a long time from now.I assume this means you don't believe that passenger transport at close to the stated goals will come about ever?Maybe, a long time from now. Going from $60,000,000 to $6,000,000 to $600,000 will take time. That's all I'm saying.John
Quote from: KelvinZero on 11/12/2017 06:15 amI was just thinking about estimating some values for my telescoping idea.I think I can work out the basic mass per volume from something like thishttps://en.wikipedia.org/wiki/Pressure_vessel#Cylindrical_vessel_with_hemispherical_endsWhat is a sensible, non Sci-Fi material choice? What should I use for density and maximum working stress? What should I use for pressure?Even using quite modest materials allows really ridiculous volumes.For example, aluminum as used in scaffolding poles can support ~290MPa of stress.A 1mm skin can in theory support around 290MPa/75kPa = 3900 times its area = 3.9m. (75kPa chosen as it is the pressure at the first highest city in the USA I'd heard of, Flagstaff).So, a 1mm skin can (just) support an 8m diameter cylindrical atmospheric load, only considering one axis.You probably don't in fact want to work close to the limit, and 75% is a sane maximum ever load. Even really, really large structural margins lead to quite large structures. Consider a nesting series of cylinders 8.5m or so in diameter and 8m or so long, 1" thick, for example.With 150 tons of launch, you get 60m^3 of aluminium, or enough to make a one inch approximately cylindrical structure 8m diameter and 100m long. (three times the B2100), for something you can order inexpensively constructed tomorrow, with rapid delivery.This is with a naive safety factor of 25 or so.Bolting this together will get you at worst 50% safe working cyclic load, with a factor of 12 safety.The proper design needs to consider launch costs, and if you're at more than double launch costs for your entire construction, you may not be doing things cheaply enough.It is reasonably arguable that you should for a system like BFR, even for initial launches, you should be aiming to design not for todays launch cost, but tomorrows.The volume and mass potentially available on orbit means that multiple approaches can be tried on orbit at once, inexpensively.You don't spend seven years and five billion dollars developing robot arms, you go to the market, and buy the twenty most popular robotic arms for a million or so, lightly modify them so they can probably cope with a vacuum, and try them in orbit.I am not saying that complex payloads are bad, but that we need to look carefully at the environment that shaped the payloads, and consider carefully if that's what we want to do.The B2100 is a great example of a payload designed for todays launchers.It is enormously highly engineered and optimised.But how much would it cost to buy 50 of them.It's not optimised for a launch cost of $100/kg, never mind $30 or $10.
What's the thinking on maintaining pressure in a telescoping tube? I'm picturing that each end of each tube segment has some kind of inflatable rubber gasket that abuts the next/previous tube (similar to those on the hatch covers in the ISS cupola), but that kind of arrangement wouldn't be able to hold pressure whilst tubes are sliding against each other. I guess it's a related problem to that of trying to hold pressure against a rotating bearing (as in a habitat with rotating and stationary parts). It's easier if you don't try to hold an atmosphere against moving parts, but parts that move can have several set positions which can hold pressure. Telescoping tubes will only be used in either contracted or extended forms - i.e. you extend it out first, then you bring it up to pressure.
btw, a full torus is a reasonable pressure vessel, but what about half or quarter torus? Would the pressure attempt to straighten it?