Speculation: Segmented Spin gravity habitat sized for launch in 2017 BFR Cargos

[MikeAtkinson]

Building the structure, whether by 3D printing, bolting together plates, or other means, is only solving the easiest problem.

After the structure is completed then it needs to be kitted out with mechanics, data and power cabling,plumbing, life support and many other systems. Then there is the QA, testing, faultfinding and repair. All much more expensive and time consuming.

[TrevorMonty]

Shorter term, for minimum assembly:

What about a telescoping nested set of cylinders? The thing expands to a long truncated cone instead of a long cylinder, but so what? This would fit arbitrarily well inside the Cargo BFS bay, because the inner cylinders could be longer than the outer ones.

Each truncated cone could be engineered with a slight curve so that a handful of them could fit together to form a torus. The tube radius would have bulges approaching 9m but go down to say 3m. Straight versions of the truncated cones could be used to reach the hub where docking takes place.

The whole idea of Oneil Cylinders is to have large enough diameter to create artifical gravity when rotating around 2-4rpm. To get a useful gravity even 0.1g the diameter needs to be 10s of meters.

[TrevorMonty]

3D printing has its place but printing 100m3 of alloy plate strong enough to hold breathable atomsphere is not realistic. I not sure 3d print can match high tensile plate manufactured by tradition methods, if not then printed structure will be heavier.

[TrevorMonty]

Building the structure, whether by 3D printing, bolting together plates, or other means, is only solving the easiest problem.

After the structure is completed then it needs to be kitted out with mechanics, data and power cabling,plumbing, life support and many other systems. Then there is the QA, testing, faultfinding and repair. All much more expensive and time consuming.

Nanoracks and their partners are trying to do just this with Centuar US, they think it can be done robotically.

If it works out then maybe Oneil Cylinders 10s meters in diameter are possible and affordable in near future using earth launched materials.

[KelvinZero]

The whole idea of Oneil Cylinders is to have large enough diameter to create artifical gravity when rotating around 2-4rpm. To get a useful gravity even 0.1g the diameter needs to be 10s of meters.

To clarify, I was discussing a torus with 9m only referring to the tube radius.

[Nomadd]

To clarify, I was discussing a torus with 9m only referring to the tube radius.

I've always thought of that with smaller, concentric rings inside, or large enough spokes to have living and work areas at varying gravities for rehab or research.

[lamontagne]

Here is a station design more appropriate for this thread.

The modules are 8m in diameter and all brought up by BFS.  Is is an assembled station, I have doubts 3D printing will be fast enough at first.  Probably eventually though, then larger stations will be possible.

The two docking ports can be brought down to 0 RPM for docking, but spend most of their time turning with the station.  This reduces the wear and tear on the rotating joint to a minimum.
This version is 60 m in radius, so 0,5g at 3 rpm. 0r 1/4g at 2 rpm.
At this stage there are only 4 modules, but eventually the ring could be completed.  Each module is separated from its neighbor by an airlock.  There are only 2 tubes to the center  this early in construction. As the station is built 2 more tubes could be added.
The structure is mainly thin cables that work in tension, attached to central rings, very close to a bicycle structure.  The 4 large spokes are structural and work in compression with added wires, not shown, and serve to dissipate vibration energy.  Lots of wires.
I must admit I worry about collision for this type of design, that is why I extended the ports far from the rotating hub.
Could modules be added while the station is in rotation?  Seems unsafe, so I expect they would be added by batches, after a few were accumulated in orbit nearby.

[blasphemer]

Bigelow BA 2100 is around 100 tons (some sources say 65 tons), reusable BFR can lift 150 tons. Maybe a Bigelow module built specifically for BFR will make sense.

BA 5000? 

[lamontagne]

Bigelow BA 2100 is around 100 tons (some sources say 65 tons), reusable BFR can lift 150 tons. Maybe a Bigelow module built specifically for BFR will make sense.

BA 5000? 

More likely Bigelowe 1200.  They are rated by internal volume and the expansion factor is about 1.5.  Musk stated about 850m3 internal volume for BFS.

The Bigelowe module is much heavier than 16 tonnes because is has much thicker walls and includes all the fittings.  My mass is for a simple carbon fiber shell, with little else.  Outfitted, it would be much heavier.

[lamontagne]

Complete station.  48 modules.  About 36 000 m3 of space. 

[speedevil]

Building the structure, whether by 3D printing, bolting together plates, or other means, is only solving the easiest problem.

After the structure is completed then it needs to be kitted out with mechanics, data and power cabling,plumbing, life support and many other systems. Then there is the QA, testing, faultfinding and repair. All much more expensive and time consuming.

'All much more expensive'.

Hmm.
Taking the somewhat extreme case that we have a dark pressure vessel with O2/N2 in it, indifferent thermal control, and that we are not going to use it other than as an emergency backup, what are the costs of outfitting?

You need a rebreather, (1) and a gas-tight suit (2). Neither is life-critical, as it only needs to work 99% or so, in order to reduce the offgassing from the humans to easily managable levels. Add dessicant to take 1kg of water. (

You need a thermal managment package (3) in case you get a bit warm, and you need a head-torch and portable lights.
Supplies for the above of course, and you have a functioning human that may grumble a bit about its suit, but is quite able to work for 8h/day.

Cost $10K or so for initial outfit, and $2K for launch.
$750 a day for supplies, $900 a day with one-use rechargeable batteries, with some left over for tools and stuff.

Assume a three week life for all of the outfit, and that's $1500 approximately per day, or $200/hr.

$200/hr is the initial price before we have any lights, power, and when we are actually throwing overboard (or deorbiting) ice after unfreezing it for thermal control, and rechargeable batteries after using them once.

A simple spinning drum, with a hose to vacuum which you put the water in with ice-cube trays around the outside will drastically reduce ice shipments, dropping it by $300/day to $1200/day.

Similary, a cupboard with a simple water-heat-exchange loop going from the inside to outside and many closely fitting shelves to place the bags of dessicant in, with a hose to vacuum drops that from $50/day to $0 or so. Minor repairs on the suit with duct tape, another $75/day.
$1075/day.

Notice that the rebreather is quite expensive, and get it serviced (on earth) and shipped back for $1000/21 days.
$750/day.

This is beyond the point that you can very easily start trading labour for complex machinery.
It becomes literally possible to employ someone to go round to everyone and swap out their cannisters, and duct-tape up any small leaks in their suits.

At this point, you actually have to start counting the pay of the astronaut, as it gets significant. ($200-300/day or so).

If you have rebreathers, and you can use them in this manner worst case, life support development becomes lots less risky.

Llife support development is made much easier by the fact that - even absent the possibility of multiple crew able to work on it and fix it, and the fact it's mass unconstrained, you can ship it back to earth almost free.
 
I am not quite saying that life-support should be made from stuff from home depot.
But you actually pretty much could.

1) https://www.oceanenterprises.com/scuba-gear/poseidon-mkvi-discovery-rebreather-system-en.html $7K
2) https://www.allpipe.co.uk/products/detail/heavy-duty-chemical-suits/trellchem-freeflow-chemical-suit ($1500)
3) http://www.veskimo.com/why-best-cooling-vest.php ($1000)
4) wherever, $100
5) https://www.shootingandscuba.co.uk/store/8-pack-co2-absorber-cartridge-for-poseidon-mkvi-from-tal-shootingandscuba $200/24h.
6) Ice, 50kg a day. ($500, assuming it is all disposed of after one use)
7) Oxygen 1kg a day, $10.
Silica gel dessicant, 3kg to 30% weight in water. $50/day. https://www.ebay.co.uk/itm/3-8L-Kitty-Sand-Silica-Gel-Cat-Litter-Buy-1-3-or-8-Bags-Value-Bulk-Deal-Natural/231510190134

[mikelepage]

So the BFR will offer a whole new level of payload to orbit. Is it enough to build a pre-assembled Oneill Colony? Spin gravity and all?

I hate to be a pedant, but an "O'neill cylinder" very specifically refers to a cylinder of 8km diameter and 32km length: So the answer is a pretty simple no.
https://en.wikipedia.org/wiki/O%27Neill_cylinder

If you're talking about using BFR to deliver smaller scale spin-gravity habitats to orbit, I whole-heartedly agree, but MODS can we please rename the thread?     Loose use of terminology does no one any favours.

[QuantumG]

If you're talking about using BFR to deliver smaller scale spin-gravity habitats to orbit, I whole-heartedly agree, but MODS can we please rename the thread?     Loose use of terminology does no one any favours.

Changing the thread title on the first post is all you need to do to rename the thread.

[mikelepage]

Complete station.  48 modules.  About 36 000 m3 of space.

Nice work.  Hopefully you'll put it in a higher orbit than that or else you'll lose it to atmospheric drag before you finish building it (just being cheeky - I know it's a concept ) For something that big you'd want to be up around the 800km altitude range, or else you'd spend a ridiculous amount of fuel reboosting it.

This is a graph of the lifetime - until drag brings it down into the atmosphere - versus altitude.  (Van Allen Belts start around 1000km)

[KelvinZero]

Complete 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.

[rakaydos]

So the BFR will offer a whole new level of payload to orbit. Is it enough to build a pre-assembled Oneill Colony? Spin gravity and all?

I hate to be a pedant, but an "O'neill cylinder" very specifically refers to a cylinder of 8km diameter and 32km length: So the answer is a pretty simple no.
https://en.wikipedia.org/wiki/O%27Neill_cylinder

If you're talking about using BFR to deliver smaller scale spin-gravity habitats to orbit, I whole-heartedly agree, but MODS can we please rename the thread?     Loose use of terminology does no one any favours.

Pedantry acknowledged. :p

[rakaydos]

Complete 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.

I doubt BE inflatables are stressed to handle 1g (or even 1/3g) while inflated, certiantly not on a permanant basis with people moving around in them.
I would expect it would require a new design.

[DreamyPickle]

There is an older thread for a "realistic near-term rotating space station".

One proposal to simplify docking was to have just two ports in the center and put vehicles in a constant roll as they dock. This requires the center of mass of the visiting spacecraft to be aligned with the docking port and will very likely be false for the BFS. Most other craft dock with their nose but for BFS this would require a flexible cover in the most sensitive area of the heat shield.

In order for the BFS to dock the station would need a constantly rotating joint around a central non-rotating docking spike. Smaller vehicles could dock on the sides of the spike but the BFS would either have to dock in the plane of rotation (2 ports only) or otherwise the spike would have to be extend at least ~10-15 meters away from any rotating spokes.

[rakaydos]

In order for the BFS to dock the station would need a constantly rotating joint around a central non-rotating docking spike. Smaller vehicles could dock on the sides of the spike but the BFS would either have to dock in the plane of rotation (2 ports only) or otherwise the spike would have to be extend at least ~10-15 meters away from any rotating spokes.

What about an airlock/"spinlock" combo?

That is, a module that can alternate between loosely bearing'd to the station, non spinning and attached to a non-spinning spacecraft with an airtight seal... to only loosely bound to the non-spinning spacecraft, spinning with the space station, with an airtight seal with the station?

It would  bypass the usual problems of making an airtight bearing with minimal friction, because it is spun up and down each time it's used, and only sealed with the side it matches rotation with.

[KelvinZero]

I doubt BE inflatables are stressed to handle 1g (or even 1/3g) while inflated, certiantly not on a permanant basis with people moving around in them.
I would expect it would require a new design.

Nah, just google a few pictures of it being used, on the moon and so on. This is exactly how it is meant to be used. This orientation is fine. All forces handled through the two rigid ends is exactly what they are designed for.

When it is sitting on a test stand on earth, under one gravity, that is exactly the final stresses it is intended for. No hair raising difficult to test optimisation of a few pounds. A hugely more convenient scenario.