A spacecraft that could sail through our solar system powered only by beams of sunlight could have its first test by May, its developers say.

Commissioned by Bill Nye's Planetary Society, the LightSail craft will be launched atop Atlas V rocket into space, where it will unfurl silvery Mylar sails that will help the spacecraft move as photons in sunlight bounce off of them.

"Each sail is just 4.5 microns thick--one-fourth the thickness of an average trash bag," the developers say in the project's website.

The tiny spacecraft, about the size of a loaf of bread, will spend around a month in orbit with its sails extended on 13-foot booms while sending images back to Earth.

The total area of the four solar sails when fully extended if almost 350 feet.

The LightSail will still be within our planet's atmospheric drag so it won't demonstrate true sunlight sailing, but the mission will test the spacecraft's system in preparation for a full solar-powered journey in 2016, its developers say.

While the photons in sunlight will only cause minuscule forward movement initially, in the vacuum of space that speed could slowly increase until such a sunlight-powered spacecraft could be moving at an impressive rate, they say.

The Planetary Society, of which Nye is the chief executive, is a nonprofit space-advocacy and exploration group that has developed the LightSail at a cost of under $4 million, funded completely by donations from private citizens.

"We strongly believe this could be a big part of the future of interplanetary missions," says Nye, best known as Bill Nye the Science Guy. "It will ultimately eventually take a lot of missions a long, long way."

After the initial test in May, a second LightSail will be launched next year on a Falcon Heavy rocket from SpaceX, with the aim of demonstrating controlled solar sailing while in a higher orbit.

"The idea ultimately is to be able to tack like a sailboat on each orbit," says Nye.

The main advantage of a solar sail is that is can save the weight and cost of the fuel needed to guide and control conventional spacecraft, suggesting missions could be launched for less than $100 million, around a fifth of the cost of a mission using a conventional spacecraft using fuel-powered thrusters.

The public will have an opportunity to watch the LightSail in action, as it is expected to be visible from Earth when its sails are fully extended, its developers say.