THE next generation of spacecraft propulsion systems could be dead in the water before they are even launched. A physicist is claiming that solar sailing – the idea of using sunlight to blow spacecraft across the solar system – is at odds with the laws of thermal physics.
Both NASA and the European Space Agency are developing solar sails and, although never tested, the concept is quite simple. A solar sail is essentially a giant mirror that reflects photons of sunlight back in the direction they came from. Although photons do not have mass, they are considered to have momentum, so according…
