Once in space, unobstructed views make solar power the perfect source of continuous energy, but to move around still requires propellant.
One common aspect of all space flight, whether sending microbes, monkeys, men, or machines, into space, is the exorbitant fuel expenditures just to get the stuff up there. Currently, to get any material to break the grip of the planet’s gravitational field, it takes some 980 MJ (mega-joules), or about the same amount of energy in 21 gallons of gasoline, to launch one kilogram into low earth orbit. Don’t forget that this amount of energy expenditure also has to include the weight of the vehicle itself, the payload, and the propellant itself, one can see that a lot of propellant is required to just get to the edge of the atmosphere.
Once in orbit, solar power can be used for onboard systems, but it’s interesting to note that plenty of propellant needs to be used just to establish and maintain orbit. Anything more, such as getting to the Moon or beyond, requires exponentially more propellant just to get that propellant into orbit for use in the vehicle. A new solar power space engine could change at least the post-orbit propellant requirements, because it require none. Actually, it sounds kind of Isaac Asimov, creators of the EmDrive describing its operation as “bouncing microwaves around an enclosed cavity” or, as the website puts it, “Thrust is produced by the amplification of the radiation pressure of an electromagnetic wave propagated through a resonant waveguide assembly.”
This may sound like science fiction, but scientists have developed a space engine that runs on solar power and uses no propellant, which limits weight to the device itself. Scientists aren’t even sure how to explain how the quantum vacuum plasma thruster works, but it does. The engine is deceptively simple, the one particular demonstrator weighing just 3 kg, generating a mere 326 mN/kW (micronewtons per kilowatt). That may not sound like much, but if you have plenty of time in the vacuum of space, where drag and gravity is a non-issue, pure solar power space flight could be a distinct possibility, and we wouldn’t have to send any propellant up to power the craft. On the other hand, 326 mN/kW might be enough to keep satellites in their orbits.
Image © EmDrive
I wonder how that level of thrust compares to the solar “wind” pressure exerted on the solar collectors required to power the engine? In other words, can it sail into the wind?