On-Orbit Crew: what might've been

In 1978, Boeing cranked out a whole lot of information – reports, presentations, artwork, etc. – on the Solar power Satellite concept. The idea was that giant satellites covered on photovoltaic arrays would be built in low Earth orbit, then moved up to geosynchronous, where the power generated would be converted to microwaves, beamed to Earth, captured and  converted back into electricity. The idea was grand, it was bold, it was forward thinking and it was doomed. In the early 1980′s the price of oil collapsed from its OPEC Oil Embargo days, and the support for such vastly expensive schemes as SPS vanished.

It was not inevitable, of course. A few minor tweaks to the timeline, and the Arab oil producing states might have kept the cost high: either through simply controlling the price, or by the simple expedient of warfare blasting the crap out of the oil fields. Had oil stayed high, who knows… SPS might’ve become the growth industry of the 1990′s.

Boeing was one of the major companies looking at the SPS concept. Each SPS would be roughly the size of Manhattan, and would produce around ten gigawatts. Hundreds of launches would be required to transport the raw materials to orbital construction bases… and hundreds of workers would be needed in both low Earth orbit and geosynchronous to oversee construction.  Boeing mapped out the probable timeline of populations on-orbit. The assumption was that two SPS’s would be built per year; this constant rate of construction is reflected in fairly constant numbers for the construction bases in LEO and GEO; the constantly increasing number of satellites explains the increasing number of maintenance crew. 20 SPS’s would require 1000 crew; 40 would need 1400 and 60 would need 1800.

A whole lot of the assumptions regarding SPS seem sadly laughable from the vantage point of the post-Shuttle years. For example space transport was seen as needing to be incredibly  cheap, with blisteringly fast turnaround times and a launch of a heavy lift booster (such as the Space Freighter) every 21 hours or so, for decades on end. Even had those succeeded, the crew numbers are almost certainly far too low. Not only would construction and maintenance have turned out to be a lot harder than hoped… there would be a lot of people not considered in these simple analyses. If you have a construction base that lasts for years… you are going to have families. And people who provide goods and services not only to the crew, but to their families. And the tourists. And the scientists, engineers, bureaucrats and everything else. Without setting out to do so, the SPS concept could easily and necessarily have led to populations in Earth orbit measurable in the thousands to tens of thousands.

Had work begun on SPS in earnest in 1980, the first flights might have started in 1990 or so. By which point we’d be two decades into the project. Assuming they kept on schedule (ha!), we’d now have at least 40 SPS satellites, each providing 2.5 gigawatts of net electrical power. That’s 100 gigawatts; over a year, 876,000 gigawatt-hours. Energy usage in the US today is about 29 petawatt-hours = 29,000,000 gigawatt-hours. Thus… a whopping 3% of todays American energy needs could be filled by twenty years worth of solar power satellite construction. Meh. One could always assume that twenty years of technological advancement might’ve improved the efficiency of the solar cells and the transmission systems, bumping up the net power produced by a satellite; still, it’d take a whole lot of satellites to make a real dent in Americas energy needs.