Of course, it is all well and good to collect the solar energy in space, but you still need to get it back to Earth. And since hooking a very, very long cable up to a 5 km (3.1 miles)-wide solar farm in space is not practical, most designs envisage wirelessly transferring the energy back via a concentrated microwave or laser beam to a huge receiving antenna (or “rectenna”) spread over several kilometres on Earth.
‘Kill it off’
All of which sounds simple. But two important issues need to be addressed if SBSP is ever to become reality - concerns about the efficiency of wireless power transmission (WPT) and the sheer cost of such ventures.
Even the most “cursory analysis” of SBSP shows that the advantages gained by moving the solar array into space is “not even nearly comparable” to the additional cost of operating in space and transmitting power back to Earth, says radio scientist Prof William A. Coles of UCSD's Jacobs School of Engineering. “No space-based power system would survive a cost-benefit analysis,” he says.
But the rise in the commercial space industry has given SBSP advocates new hope for changing the economic equation. A 2011 report by the International Academy of Astronautics (IAA) found that SBSP could be commercially viable within 30 years, driven in part by the rise of private space companies.
Two names crop up with regularity in discussions about SBSP and commercial space: Planetary Resources –the wannabe asteroid mining company launched earlier this year - and SpaceX, the first commercial space firm to send a cargo to the ISS, founded by South African tech billionaire Elon Musk. If just one of these firms – which have already shown they see the potential return on taking on high risk projects in space – can be persuaded to focus its attention on SBSP, the technology has a fighting chance, advocates say.
They point to the falling costs of launching things into space. It currently costs around $20,000/kg ($10,000/lb) to launch anything into orbit. To send a rig that could be several kilometers across and weigh several thousand tons sets a price tag starting in the billions of dollars. And that is before you have had to assemble the solar panels, an operation that would likely take at least as much skill as assembling the International Space Station – a project that has a price tag of around $100bn.
But Musk has talked openly about how his company plans to build reusable launch vehicles and slash the cost of launching into space to $1,100/kg ($500/lb) or even lower, making the prospect of building giant structures in space seem a less fanciful notion. However, any SBSP firms hoping the entrepreneur may put his financial muscle – as well as his rocket systems – at their disposal may be in for a shock. Musk has previously been hostile towards the idea of SBSP, once saying “stab that bloody thing in the heart” to suggest the idea should be killed off once and for all. SpaceX declined our request for an interview.
Budding entrepreneurs may find more enthusiasm from Planetary Resources co-founder Eric Anderson, who sees its potential, but has no immediate plans to invest in SBSP research or development.
“The only way to get solar energy that is truly plentiful, reliable, and available from anywhere is through SBSP, but the set-up costs are exorbitant,” he says. However, commercially-funded SBSP might take off if it is initially used to deliver power to markets and locations that are “insensitive to price,” such as military positions, disaster scenes, and search and rescue operations, he adds.