I have another idea for docking to a rotating station. Visiting ship approaches the docking port and noses into a de-spun framework which has various clamps that hold the ship in place. The frame then rotates up to match the station spin rate and lines up the ship’s docking port with a crew access arm that attaches to the ship’s hatch. Pressurise and transfer.No rotating seals. Slight adjustments of the ship position by the clamp mechanism could fix any balance problems.If the central hub of the station was actually cup or tube shaped then the ship would be effectively inside the station and in the plane of rotation, on the axis of spin. Would this solve any intermediate axis problems ?
Ok. I apparently wasn’t clear. The approaching ship is not rotating when clamped into the catch frame, which has been de-spun to meet the ship. After the ship has been secured the frame starts spinning up to match the station’s rotation so the ship is now effectively not moving wrt the station but is physically attached to it.Now it would not matter where on the ship the docking hatch was located as the transfer arm would be flexible/ articulated enough to attach to it, within reason. There may be more than one arm if a variety of vehicles visited regularly.
Backtracking to the conversation we were having before the rabbit hole, I've been toying with ways to compare shielding mass for bola/sphere and toroid geometry space stations. If I'm allowed to float an unfinished idea for discussion without being subjected to the Spanish Inquisition, I'd be interested to hear your thoughts.As Twark_Main has often pointed out, toruses have significantly more surface area than a sphere of equivalent volume, so the first figure is my attempt to map out the relationship for a series of toruses of different minor radii. Y axis is of the major radii those toruses have, in order to have equivalent volume to a sphere of radius indicated on the X axis.The second figure maps out the ratio of surface areas between the torus at the equivalent point in the first plot, against that of the sphere of equivalent volume.I think (?) it makes sense to assume that for points on the plot where surface area ratio of torus to equivalent sphere is equal to 2, that means that a toroidal magnetic shield would have to reduce the dose to that achievable by passive shielding, for less than half the mass, to be better than the equivalent sphere.The key thing about a torus geometry that makes it more amenable to magnetic shielding (if I've understood the papers upthread correctly), is that aligning the superconducting cables along the full circumference of the torus allows the magnetic field produced to be much smaller for a given amount of protection, and the structural reinforcement required to restrain the cables is consequently far less massive. A first pass at some very kludgy calcs: A 0.64T field (figure 11 of the Slough paper) seems to substantially reduce dose received, although it isn't quantified anywhere in the paper I can see. Generating that field using commercial grade YBCO superconducting cables (see wikipedia) which can carry 700-2000 amps/mm2. I assumed 1000 Amps/mm2. In this case, my BoE implies cables of 32cm2 cross section, massing ~25kg/m. Not sure how many of them we need, so for my calcs I've assumed 8 of them for the 1m minor radius torus, and scaled up linearly with minor circumference (i.e. 40 cables on the r=5m torus). More is better for protection, but has higher power requirements.As an example, I'm looking at the 4m minor radius torus, and at the point where it has a major radius of 22.92m (so 26.92m-18.92m inner/outer), it's internal volume is equivalent to a sphere of radius 12m. To achieve 20g/cm2 of LH2 shielding (about a halving in exposure) around the sphere, we'd need ~362 ton of LH2 (excluding support structure). Alternatively, for the mass of the superconducting cables, for that torus (which I think also achieves about a halving) I get ~29 tons (excluding support structure). Not exactly apples to apples, but this fits with my intuitive understanding and why I've suggested that torus geometries (plus magnetic shielding) may be more efficient mass-wise than spheres (plus passive shielding).
I know it's a long thread, so maybe I missed it, but why are y'all trying to optimize for such abstract things as volume and surface area?
If Starships costs $10M, then a tube 10-12m long and 9m in diameter costs $10M to LEO.
String about 50 of those together to make a rotating Space Station. Net cost is probably $2B or so, running at 1/3 gravity and less than 2rpm at about 100m diameter.
Line the inside of tube with 1m of plastic for radiation and you've still got 7-8m of internal diameter for your space station, enough for 2 decks. Make the tubes completely standard with compartments, accessways, insulation, and isolation airlocks, etc.
Optimize for what's cheap, not for some abstract geometric principles.
Separate from the point you are making, as of today the Starship volume is only a max of 8m, and the length of a 8m diameter module could only be 8m long. Elon Musk has stated that they plan to extend the length of the ship, and for me I need a 10m long by 8m diameter module for one of my stations, so we'll see. But as of today 8x8m is the most we can count on.
Quote from: Coastal Ron on 06/02/2023 06:14 pmSeparate from the point you are making, as of today the Starship volume is only a max of 8m, and the length of a 8m diameter module could only be 8m long. Elon Musk has stated that they plan to extend the length of the ship, and for me I need a 10m long by 8m diameter module for one of my stations, so we'll see. But as of today 8x8m is the most we can count on.That's internal cargo using reusable Starships. That's a lot of logististical nightmares. So don't do that.
I'm talking about making a batch of 50 or so custom Starships. No heat shields. No header tanks. Separable tank and payload section. Minimal engines. Cost to LEO about $10M each.
Too many times we start engineering solutions before we understand the problem, and rotating space stations is no different. Me included. But I think many of us on this thread have finally started focusing on what the use case is, and using that as the starting point - or backing into it, same difference...
Realistic, near-term, rotating Space Station
Logistical nightmare? If humanity can't perfect the delivery and distribution of large cargo to and thru space, humanity won't be able to expand into space. Luckily we have already shown we have the ability to assemble large cargo in space (i.e. the 450mT ISS), so the vast number of rotating space station designs rely on cargo being delivered on reusable Starship
Quote from: Coastal Ron on 06/02/2023 06:56 pmToo many times we start engineering solutions before we understand the problem, and rotating space stations is no different. Me included. But I think many of us on this thread have finally started focusing on what the use case is, and using that as the starting point - or backing into it, same difference... Alas, the thread title isn't on your side. It saysQuoteRealistic, near-term, rotating Space StationWhich presupposes there's someone who would pay to be in a rotating something in space, presumably without getting dizzy (or we'd just rotate a Starship at 10rpm and be done)
Quote from: Coastal Ron on 06/02/2023 06:56 pmLogistical nightmare? If humanity can't perfect the delivery and distribution of large cargo to and thru space, humanity won't be able to expand into space. Luckily we have already shown we have the ability to assemble large cargo in space (i.e. the 450mT ISS), so the vast number of rotating space station designs rely on cargo being delivered on reusable StarshipThat's completely glossing over the root of any space station problem.Logistics of orbital assembly is the problem to solve esp. with the 'near term' constraint
I know it's a long thread, so maybe I missed it, but why are y'all trying to optimize for such abstract things as volume and surface area?If Starships costs $10M, then a tube 10-12m long and 9m in diameter costs $10M to LEO. String about 50 of those together to make a rotating Space Station. Net cost is probably $2B or so, running at 1/3 gravity and less than 2rpm at about 100m diameter.(Snip)Optimize for what's cheap, not for some abstract geometric principles.
Lastly the thread title is one of those things where we’ve never been able to come to a consensus on what it should be called, but most of us regulars treat it as kind of a “catch-all” thread about AG ideas.
A 0.64T field (figure 11 of the Slough paper) seems to substantially reduce dose received, although it isn't quantified anywhere in the paper I can see.
B00 [relates] the field strength to the shielding effectiveness. B00 ≥ 2.2 T [is characteristic for] scaling, current, and structural requirements.
Quote from: InterestedEngineer on 06/02/2023 04:51 pmOptimize for what's cheap, not for some abstract geometric principles.While I agree that "abstract geometric principles" are sub-optimal in this discussion, your idea of connecting a number of StarShip tubes needs some work. Here's why:Quote from: InterestedEngineer on 06/02/2023 06:32 pmI'm talking about making a batch of 50 or so custom Starships. No heat shields. No header tanks. Separable tank and payload section. Minimal engines. Cost to LEO about $10M each.Clearly these modules would be custom, but you've fogotten the cable that would tie them all together in a ring station. If not cable, then some structural element in tension. There would also have to be pressurized sections where astros could live while they work. There are a number of other requirements that you haven't yet mentioned.Point being: $10M per Lego piece is not sufficient.
$10M was the launch cost. Sorry about the confusion.
They each have airlocks which implies pressurized sections.I also thought airlocks implied docking but it does not, sorry. So yes 3 or 6 docking ports.They are held together by docking.
No humans involved for basic assembly. Humans finish the interiors.
why are y'all trying to optimize for such abstract things as volume and surface area?...Line the inside of tube with 1m of plastic for radiation