From NEO to GEO --- an SPS scenario

1.) Transport workers and tools to a suitable NEO.
2.) Construct a solar power satellite (SPS) out of local materials at a
construction site located a few kilometers away from the NEO.
3.) Fly the completed SPS back to Earth geosynchronous orbit using
electrical propulsion (e.g., ion drive a la Deep Space 1, or MHD, or M2P2,
etc.). This is a pretty good proposal, and you make some good points, but I would still tend to favor retrieving resources from the NEO, transporting them back to High Earth Orbit, and building the SPS there. There's no way to obtain asteroidal resources without sending human beings far from Earth, and that can't be helped. But I think there would be advantages to concentrating most of ourother activities, such as ore refinement, parts fabrication, and assembly as close to Earth as possible. For one thing, if telepresence technologies advance sufficiently to come into play, they can be used from Earth at the distance of HEO (or even the moon), but not at the distance of a NEO. And being relatively close to Earth is good in an emergency situation. Two of your advantages, constant sunlight and use of high efficiency drives, would also be applicable if most industrial operations take place in HEO. I'll always have asoft spot for mass driver tugs, but it's conceivable that some of the other high-efficiency/low-thrust drives you mention could also be used to fly resources from a NEO back to HEO. Some thinkers at SSI have recently said it might be better to send your ore refinery/manufacturing center to a NEO and to build a space habitat there rather than in HEO. But here too, I'd tend to favor assembly in HEO. I think initial stocking of the ecosystem would be easier if Earth were nearby, and unanticipated, near-emergency requirements for this kind of decomposition bacteria or that kind of plant might be better met if Earth was 2-3 days away rather than 2-3 months. But I will say this for the "build your settlement next to a NEO" approach. Just about the only undeniable advantage of settlements on the surface of Mars vs. O'Neill settlements is that the resources you need are literally underfoot. Building habitats in HEO will require importation of all raw materials from elsewhere in space. But I think an O'Neill habitat being built next door to a NEO would have the same easy access to resources as a Martian colony, and thus feel that the oneremaining advantageto building settlements on Mars would collapse in that scenario. Long term, I expect far more habitats to be built next door to an asteroid than in HEO. But I still expect the first generation habitats to be built in HEO. I also expect SPS intended for Earth surface service to be manufactured and assembled in HEO, regardless of whether we tap the moon for resources, a NEO, or both at the same time.