|Seriously, go check it out. It has pictures.|
First is that I'm not sure about having the spin rails out on pylons from the sides as they are above. They're going to be fairly beefy, and then they have to also support the modules going around the track. Why is this an issue? Time for a structures lesson. Imagine a ship under thrust, consisting of an engine, a support truss (A&B) and two spin rings on pylons (C&D). Essentially, this is a simplified version of Ray's IPV design.
|Might look something like this|
In this configuration, the majority of the forces are now compressive, and the only shear-loaded members are the actual spin rail supports, which are shorter and can be more numerous, reducing the stress on any individual beam.
The other thing that bugged me about the concept was the sidetrack concept Ray introduces. On the one hand, it's nice since it allows people to move from the spin sections to the stationary sections (including radiation-shielded shelters for solar storms) without leaving their modules, which is very nice and worth having--it's an innovative thing, and one reason I like the concept. On the other hand, it means more complexity, and this requires consideration. First, since the rail section needs to keep it's center of mass placed properly, every car must be balanced by the other cars (two cars 180 degrees apart, 3 cars at 120 degrees, 4 at 90, ect....), and it makes sense to have the ability to take off or add two cars at a time from opposite sides to be able to maintain this balance. So instead of just one switch in the spin rail, you need two 180 degrees apart.
These switches will also need to be quick-cycling. If you have several cars going around your spin rail and you want to take off only one of them (or two, for balance), then you need to be able to cycle the switch to get the car off and cycle it back to the straight position before the next car comes through. To get an idea of just how fast they need to cycle, you need to know how fast the cars are moving and the number of cars on the rails. By my analysis of his drawings (like the one above), the life modules are about 4 m in diameter, and the spin ring track is about 28 m in diameter, for a spin radius of 18 m. Using SpinCalc, this gives the following figures for 1 G:
|Run with Ray's size and 1g generated|
|Run with Ray's size and 5 RPM|
|Size required for 1 g with 5 RPM|
At 7 RPM, it takes about 8.57 seconds for a car to go around the track. With 4 cars on the track, the time between cars is only 1/4 that time, or 2.14 seconds. This is the margin that the switches have to cycle within. Even at only 5 RPM, the window with 4 cars on the rails is only 3 seconds-still very short. Can a switch be made for this? Maybe, but it's going to be tricky.
Anyway, moving on from the question of how the switches need to operate to how rails would need to be run. The track layout Ray shows on his example here basically can be though of as translating to the following diagram.
|Diagram of Ray's basic tracks|
|Modified Track Diagram|
I also looked at possible track arrangements for axially-located spin rail like I suggested at the start. The best I came up with was the below. Note that the system is modular--it works for one, two, three, or more spin rings.
|Track diagram for axial spin rail|
So, I stopped for a closer look. The cubes were 1 ft cubes of aluminum honeycomb, lots of little cells connected together. Apparently they were being prepared for some experiments involving flight data recorder crash survival, as targets. We've used honeycomb material in Aero team a little, but never metal, and never this thick (our would be more like a sheet, with the cells only about 0.125 to 0.25 inches deep). Anyway, it was nifty stuff, and I'm glad the guy was willing to stop and let me have a look.