Part of the development of off-world colonies will be transfer platforms where interplanetary and inter-orbit vehicles will meet. The role of the vehicles will change over time and there will be a critical need for flexibility in whatever vehicles are deployed. This will enable high cadence and scaleable inter-planetary travel in the near term, and a sophisticated off-world human presence in the longer term.
If we consider the logistics required - the 'customer' requirement - then work back from there, we can start to understand where and what it would make sense to deploy in terms of orbital stations.
Firstly, there are human manned missions - these, in the short term, will be direct there-and-back runs to Mars - there will be no need for stop-overs. Indeed there will be no infrastructure for this anyway.
Of course there are fore-runner unmanned missions to deploy equipment and test the landing ability of starship on un-prepared surfaces, but these will also be independent. They will not require orbital infrastructure to proceed. That is not to say we do not have the technology for remote independent docking - SpaceX CRS-21 resupply mission demonstrated that capsules are already able to self dock with the ISS.
Space Warehouse
Then there are cargo, and fuel runs. If we consider cargo runs to-from the ISS at the moment, payload is carefully packed in a methodical manner - with pack sizes appropriate to ensure that they can be easily loaded into/ out of the capsule. Once organised, the cargo is strapped down and launched.
On arrival the capsules are docked, opened up, unpacked. The crew carefully stow the new supplies and again - methodically - pack up waste and used, nonfunctional items and return them to Earth via the returning capsule. As capsules are mostly reused, it makes sense to return the waste to take care of in a responsible manner.
Having said this, it was recently noted, from a safety perspective, that the ISS has jettisoned - sans-capsule - direct to space, 2.9 tons of used batteries, associated with the station's power management system. These batteries were used to store sufficient power while the station undergoes its average 16 daily day-night cycles. The intent is that these cells will enter the atmosphere in the next 2 - 4 years and burn up harmlessly.
Extending this logic to orbital outposts, as the payload is packed and stowed with human hands on the outbound and return journeys, it would suggest that any orbital cargo depot would also be manned, making it similar to an extension of the existing ISS.
The concept of removable load packs which can be interchanged between starship vehicles was explored by artists on Twitter.
However, adding pack containers to containerise cargo which can be trans-shipped adds greater weight to the craft. Already the economics of getting material to orbit is fraught with high prices. I think this concept - while useful, does represent an obstacle in the short term. And the concept does not address the manual handling aspect. This would suggest that - in the near-term, it could be feasible to launch a significant 'warehouse' section of the ISS - extend the station and use that real-estate as a depot, equipment/ material handling area.
As the ISS is modular, it could make sense to continue expanding/ adapting. However, with the facility nearing end-of-life, this could be a less and less attractive prospect for NASA - from a liability perspective, and and buyers - from a cost/ maintenance perspective.
Orbital Gas Station
The opportunity which speaks louder than these others is the prospect of orbital fuel depot. The cost to deliver tons of fuel to orbit is so high right now, and will continue to be so, even with declining freight cost curves with the advent of successful starship cargo missions.
With such high costs, it makes sense to utilise in-situ, resource utilisation. But there are no resources in the vacuum of Earth orbit. As a result, it makes sense to pick up inflows from the Moon - shuttling autonomous tanker Starships back and forward, filling and refilling a cryogenic storage bunkering station.
Elon himself recently tweeted tacit support for such a facility. One content creator happened upon this and gave their thoughts:
How to get there from Here?
Human transport buses can operate on a fixed route, going backward and forward because - when carrying human cargo, there is only really space for humans and the required equipment and resources to keep them alive and well on transit to Mars.
It must be considered that, certainly in the short term, what the impact of the harsh environments are in which these vehicles will operate.
Just like the run of Starship SN8, SN9, SN10 and shortly, the SN11 prototype, this fast iteration of construction and testing is also accompanied by thorough assurance - post flight check, and in the case of all these prototypes which have landed with Rapid Unscheduled Dissassembly.
Markings, Lights, Identification
Longer term, when there are fleets of hundreds of starships, both taking off and landing on Earth for point-to-point transport, and for off-world transport. There will be a need for traffic control, similar to that at an airport. This also implies that there will be tail numbers, transponders, black box recorders and lights associated with the vehicle.
Let us compare and contrast this with the form and expression of these features on the Space Shuttle. That great vehicle is probably the closest example which could be readily compared to the concept of Starship, as reusable orbital vehicles go.
In a pinch, we could also consider the Russian Cosmonaut transport and Crew Dragon capsules. As we can see in the visuals below, they are clearly marked with individual vehicle markers, helping distinguish them for the much more common “airlock hop” missions - leaving the station for around 30 minutes, then re-docking at another airlock. Leaving the original airlock dock free for another imminent arrival. Because of the greater frequency of space vehicle launches, the need for such missions to move capsules around the ISS, akin to making parking spaces available is increasingly common.
I could suggest that an extension of the ISS to include a dock with multiple air locks could be a good idea, enabling multiple capsule docks in the same area, yet retaining the existing air locks as well. Some artists impression below.
This way the crew can spend less time conducting vehicle move missions, and more time on the science, engineering and technological, biological development, material science works, etc.
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