More on infrastructure

 With the wonderful suggestions of some friends, I've developed some additional ideas about interworld travel, with an emphasis on some infrastructure stuff. For context, we know the Rosa system features a number of large interworld spaceliners on cycler orbits, tethered by long cables to slag counterweights so they can be spun up to produce gravity. The size and mass of these liners (I'm imagining up to 500m in length, for the largest) suggests in-space construction - and I mean real in-space construction. Not modules being docked together, but rivets being driven by actual people in space. This further implies the existence of big orbital shipyards where this stuff can be built, as well as additional space infrastructure like tugs and such for moving cargo between orbits.

The big addition to the lore here is going to be a dedicated skyhook (or multiple!) in orbit of Orus. Since the vast majority of the system's heavy metal resources are mined and processed here, it's long been the focus of infrastructure (take a shot) for shipping and handling lots of cargo. The sustained need to hurl huge amounts of mass skyward will spur the construction of this as-of-yet unnamed megastructure.

As a quick recap, a skyhook is sort of like a partial space elevator. Instead of being affixed to the ground, such a structure is placed in a low orbit and only extends partially down into the upper atmosphere, and equally doesn't stretch too much higher - a total length on the order of hundreds of kilometers. The key is that the structure rotates - tumbling end-over-end much like the cyclers do. The idea is that the end swings backwards relative to its own orbit as it approaches the planet's surface, reducing the relative speed. So, you have a skyhook dangling from space and moving relatively slowly, which can be intercepted by a vehicle launched from the ground. As the tether rotates, payloads attached to the end get flung up and out of the atmosphere. Detaching at the highest point will send you into a still-higher elliptical orbit, since you're moving faster and higher than the CG of the tether.

The motion of the skyhook over a planet's surface would look something like this; rotating as it orbits, the endpoint comes nearly to a standstill as it approaches the ground:

Boeing studied a concept like this for Earth, and concluded that, unlike a space elevator,

We don't need magic materials like "Buckminster-fuller-carbon-nanotubes" […] Existing materials will do.

Their concept involved a tether that only skimmed the upper atmosphere and whose endpoint still traveled at Mach 10, but I think I can stretch this with a bit of handwaving.

For Orus, the skyhook(s) would extend nearly to the surface - maybe 10km or lower, accessible by non-rocket means. I would also prefer for their endpoints to move quite slowly at their lowest point, perhaps being able to hook payloads that are stationary (with the help of an intermediate trapeze, at least).

My vision for heavy cargo infrastructure on Orus looks like this: Cargo is loaded into a large spacecraft, similar to the passenger tenders we discussed earlier but substantially bigger. These spacecraft are then airlifted by huge hybrid airships: using bulk lifting gas for enormous lift capacity, but leveraging dynamic lift to extend their altitude range, flying at some significant airspeed to climb to their service ceiling. These carrier airships would likely be double-hulled like a catamaran, with a structural segment in the middle on which the cargo vehicles would be carried. Flying along the ground track of the tether, they'd hit their peak altitude while tracking to the endpoint hook, with a dynamic trapeze to bridge the final gap. Once secured to the tether, the airships would release their payload, and the cargo vehicles would be lifted up and out of the atmosphere. Once in their high transfer orbit, the cargo vehicles would use onboard propulsion to circularize, perform other orbital maneuvers, and even propel themselves on interworld trajectories. Finding no similar tethers at their destinations, they would be equipped to perform reentry and envelope-arrested descent much like the passenger tenders.

The tether(s) could also be used to return inbound interworld cargo to the surface, but this requires vehicles to perform part of the capture themselves - propulsively or aerodynamically - before they can interface with the tether at its highest point in space. Vehicles would also need to be cast off slightly ahead of the tether collecting new cargo at both extremes.

I think a tether like this would be made large enough to carry a significant batch of cargo at once - multiple vehicles in formation, perhaps. Or, it might be interesting to make the tether more of a multi-spoked wheel, With many cargo exchanges per rotation period. That could certainly lend itself to some cool imagery. Also, I figure the g-loading that cargo endures during the tether-flinging process probably amounts to significantly more than is considered suitable for passenger transport, so these vehicles are crewed only by trained personnel....normally.

This actually has some fun implications for plot ideas, which I'm already forming in my brain but would like to keep from publishing here until I've posted more of the plot overview. When we last left off, Noira was preparing for her first night voyage aboard Ark Royal, and we've a long way to go from there already! Continuing the plot overview will likely be one of the next posts here.