Affordable SPS… Paul Roseman

June 19th, 2007

The International Space Development Conference 2007 was held over the weekend of May 25-28 and was chock-full of ideas. One especially caught my attention because its developer, Paul Roseman, is a Sci-Fi fan like me who dreamt of working in space, and actually has a plan to bring that future about. Paul has graciously allowed me to reproduce his paper here on Crowlspace, and I would like to discuss it in some detail.

Here’s the abstract, to tease you into reading the whole speech,…

It may be possible, now, to build a 5 gigawatt space solar power system for about 10 years revenues at $0.10 per kilowatt hour. This can be done by utilizing an as yet unused materials stream available in low earth orbit (LEO). This method is required to lower the costs of this project due to the massive amount of material to be launched into orbit. The materials stream is used to create both the structure/frame of the solar collecting and microwave transmitter beaming satellite in geosynchronous orbit (GEO), and the shell of the habit/remanufacturing facility in LEO.

That materials stream is spent boosters. For many launches with strap on boosters, like the Space Shuttle or the Ariane V, these main boosters can be launched into LEO at some or little payload weight penalty. For the Shuttle, next to none; for the Ariane V, about half of the payload. In LEO, these boosters can be melted down and remanufactured into structural parts for the solar cells and microwave transmitter elements, manufactured on earth.

These boosters can also be captured and used to create the shell of the variable gravity, closed ecology, remanufacturing facility in LEO. Earth standard manufacturing hardware will be launched to space in containers which will be stuffed inside the booster shells. These booster shells will be connected and rotated with ion engines to induce an artificial martian gravity at the ends, with variable gravity down the spine. The solar power panels will be manufactured inside the structure and assembled on its frame, then connected to unmanned transport and taken to GEO, where they will be joined with the satellite to increase the power sent to earth. The closed ecology of the remanufacturing facility will save significant money by lessening resupply at $5,000 per pound.

The revenues of the project are $40 billion, determined by 10 years of 5 gigawatts of power delivered at $0.10 per kilowatt hour for 8000 hours per year. The costs are primarily determined by the standard launch costs of $5,000 per pound to LEO. They are estimated at $35 billion. Of that, current solar cell costs for 5 gigawatts are $5 billion for the cells and $22.5 billion to launch them to LEO. Ion engines and fuel are used to get the finished modular pieces of the solar power satellite to GEO, so that the costs are also quite reduced.

Optimistic? Of course, but nothing is ever done without taking a risk.

First point of my discussion is the question: How much can launch costs be improved in the short term?

Paul cuts costs by haulling the finished components of the SPS to GEO with solar-powered ion-drives – plus he uses the upper stages of the boosters for structural materials. He bases his cost estimates on the current rates of placing payloads to LEO – between $10,000-$5,000/lb ($22,000-$11,000/kg) – but there is a cheaper option that may be available soon. Elon Musk’s SpaceX is offering haulage to LEO via its Falcon 9 Heavy for a $90 million launch fee. Maximum payload is estimated to be ~ 27,500 kg, thus the per kg cost is $3,300/kg. Musk promises a “modest” discount for long term contracts, so let’s call it $3,000/kg.

Roseman cuts mass-to-orbit cost by using the lower stages of the launchers. On the SpaceX site there’s a technical description of the launcher available and I’m working on just how much a Falcon 9 could push into orbit. So watch this space…