A version of this article appears in the June 9 edition of Aviation Week & Space Technology.
John Mankins, a prominent U.S. space solar power (SSP) guru who has toiled in the fields of government for decades to study and promote ways to beam down the Sun’s energy to feed Earth’s power grid, has hit on a new way to get from SSP Version 0 to space collectors kilometers across. Start small, and go for a commercial payoff from the beginning.
Starting small has always been the plan. But instead of a billion-dollar prototype solar power satellite (SPS) system delivering electricity at five or 10 times the cost of coal, Mankins wants to start with a new kind of SSP collector and use it to power broadband communications satellites. “Imagine a satellite which costs no more than today’s communications satellites, but has 10 times more bandwidth, 10 times more power, 10 times more revenue for the same spacecraft,” Mankins says. “It’s T-2 lines for all mobile devices, everywhere.”
Mankins and a core group of investors have set up a new company, Mankins Space Technology, to market the idea to investors in Silicon Valley and elsewhere. The broadband application would use an early version of a robotically assembled, modular solar-power collector in space that Mankins calls SPS-Alpha, building on technology advances in everything from high-temperature electronics to warehouse inventory systems. As larger collectors are built, the opportunities for profits and other benefits also increase.
“Every step on the way to the space solar power of the future is a step forward toward more and more capable spacecraft for communications, for direct broadcast, for radars, for the future science missions, before you ever get to solar-power satellites,” Mankins says. “For the next half a dozen years, we’re not even working on solar-power satellites. We’re working on a completely new approach to space systems.”
Mankins describes that approach in a new book that provides great detail on the technical, economic and marketing aspects of its title, The Case for Space Solar Power. To gain an early cash flow, SPS-Alpha starts with a mass-produced “HexBus” and links it into larger and larger structures, each with its own power application, before reaching the distinctive goblet-shaped collectors that concentrate sunlight for conversion into a microwave beam pointed at a huge rectenna on the ground.
“[Even] a very small-scale demonstration of the systems for space solar power is a huge new capability for communications satellites,” he says. “A small demo of a solar-power satellite system concept would be maybe 200 kilowatts of onboard power, and the largest commercial communications satellite today is about 20 kilowatts.”
Even skeptics of SSP find the idea of boosting satcom power intriguing. “Communications from space [are] the only thing that ever has so far sold at a profit,” says formerAdministrator Michael Griffin, who does not believe the benefits of power from space ever will outweigh the cost of getting the necessary hardware into orbit (see page 42). “So until I see the particular idea, I can’t comment, but I would tend to be favorably disposed toward the idea that you can make money selling communications from space, or better communications from space.”
Robotics and mass production are also key to the SPS-Alpha concept. Mankins has whittled the whole space-based portion of his system down to eight “generic” modules, all of which could generate terrestrial jobs in factories that would manufacture them in bulk at low cost. In addition to the HexBus—essentially an empty hexagonal frame with wireless communications capability—an SPS would be built up with 1-kg (2.2-lb.) “interconnects” to hold the structure together; “HexFrame” deployable beams to hold the collectors and transmitter in the proper configuration; thin-film “reflector deployment modules” that redirect sunlight to “solar power-generation” modules using photovoltaics to produce electricity; and “wireless power-transmission” modules that convert the electricity into microwave beams.
Launch remains a major stumbling block to a full-scale system, which Griffin suggests could only be built reasonably using material collected in space to avoid lifting it out of Earth’s gravity well. But Mankins believes that reusable launch systems such as the Falcon 9R in early development atcan cut the price of orbiting a kilogram of mass to $500-1,000—“all that SPS requires during initial deployments.”
Ultimately, Mankins has calculated that his modular approach “with continuing technology improvements” can lower the cost of a kilowatt-hour of space-generated electricity on Earth to 9 cents. Spot-beam technology can deliver it where it is needed on Earth, and SPS systems in orbit around the Moon or Mars could beam power to outposts on those surfaces for $20-40 per kilowatt hour.
Critics who worry about birds in flight being “cooked” by microwave beams, or other disasters, just have not kept up with the technology, he says. “The techniques we’re looking at—low power density, highly controlled microwave transmission—represent less danger than almost any other energy source in use today,” Mankins says.
Tap the icon in the digital edition of AW&ST for an interactive look at the SPS-Alpha concept, or go to AviationWeek.com/ssp