Space-based solar power returns: China, Japan, US and UK race to test it

China, Japan, the US and the UK are developing space-based solar power (SBSP) projects, from China's ZhuRi to Japan's OHISAMA and the UK's Space Solar. Test launches are targeted within five years, but critics point to exorbitant costs and untested assumptions.

• China, Japan, the UK and the US target SBSP test launches within five years
• Projects include ZhuRi, OHISAMA, Space Solar, Caltech and AFRL experiments
• Satellites in geostationary orbit 36,000 km would beam power via microwaves
• Critics say the technology is too costly and unproven