Today at NASA Dryden Research Center in California, three teams are competing to propel robotic climbers up a vertically tethered cable using high-powered lasers. The competition, called the Power Beaming Challenge, is part of the Space Elevator Games run by the Spaceward Foundation, and is sponsored by NASA's Centennial Challenges program, which will award $2 million in prize money.

According to NASA:

This challenge is a practical demonstration of wireless power transmission. Teams build mechanical devices (climbers) that can propel themselves up a vertical cable. The power supply for the device is not self-contained but remains on the ground. The technical challenge is to transmit the power to the climber and transform it into mechanical motion, efficiently and reliably.

For the competition, a cable will be tethered from a helicopter at a height of one kilometer. Each robotic climbers must weight no more than 50 kilograms and must ascend the cable at a minimum speed of two meters per second.

All three competing teams will use lasers as their power source instead solar power or spotlights, as have been used in the past. Power is limited, so teams must build power dense machines. The best performance to date--competitions were held in 2005, 2006, and 2007--was a robot that travelled at 1.8 meters per second for 100 meters.

The purpose of the competition is to spur development of systems that might ultimately lead to a space elevator--a machine intended to scale a stationary cable from Earth to space. But power beaming also has applications for lunar rovers and space propulsion systems.

This year's competition will run until November 6. You can watch it live here or follow Twitter updates.