Japanese space agency (Jaxa) scientists want to detect a measurable acceleration in the spacecraft as photons - the particles of light - from the Sun fall on the roughly 200-sq-m, ultra-thin sheet.

BBC: Mini-camera pictures Japan's Ikaros solar sail

They are very active now in events nationwide and has the quickest acceleration right now to be a top 3 contender in this space.

FORBES: Top 10 Crowdfunders of 2013

But analysis of the motion of Ulysses, another space probe, has shown that it, too, is affected by the mysterious acceleration.

ECONOMIST: A space oddity

For this jump, the team also worked to create a new generation of space suit for better mobility and visual clarity, studied the effects on the human body of supersonic acceleration and deceleration, developed a new parachute system, and more.

FORBES: Out Of The Stratos: Investing In A Greater Good

Stratram would need to overcome a lot of challenges, particularly if squishy humans were among the things being transported into space: the track would need to be around 1, 000 miles long to avoid the kind of instant acceleration that could crush a human, and the train would need a low-pressure vacuum tube to travel through.

FORBES: Connect