Anything that will fit in a 30ft diameter faring weighing less than 150 metric tonnes. I’d love to see commercial space stations that can house large numbers of people in comfortable cabins so it’s more like a cruise ship than a submarine. Gotta power all those amenities somehow without diesel generators. But you could also put things like datacenters in orbit if the cost savings on power production made it worth while. Longer term you need a lot of power for resource extraction and processing and manufacturing. Would also make light sail propulsion of probes or deep space missions possible using lasers or beamed microwave power for ion thrusters so you don’t have to sacrifice mass for nuclear and aren’t constrained by how much wattage you can produce on board.
Is there any realistic way to dissipate the heat from a datacenter in space, even ignoring the transport costs?
Also, the limitations of being in an extreme hostile environment make it completely impossible to get cruise ship levels of comfort in outer space, at least with currently known technologies. The huge amounts of radiation and the bone density loss from being in low-g for any weight of time, coupled with the extreme acceleration on the way up and the way down, will also severely limit space tourism regardless of transport costs.
