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$2 Million NASA Power Beaming Challenge Heating Up 98

carstene writes "Qualification rounds for the NASA Centennial Challenge Power beaming contest are underway at the Dryden Flight Research Center. The contest uses a scale model of a space elevator as a race track. Entrants must build a robot to climb a cable, suspended by helicopter, 1 km into the sky without any on board energy storage. The teams are using high power laser beams to transmit power from ground stations to photovoltaic arrays on the robots. If a team can accomplish this at 5 meters per second average speed then they could win up to 2 million dollars. One day this technology could be used to power rovers in shadowed areas of the moon or to recharge electric UAV's in-flight or even a space elevator in the far future. A blog of the event can be found here. Full disclosure: I'm a member of the LaserMotive team that you can follow on twitter, or or via blog."

Comment Re:Stopping distance is another big lie. (Score 1) 1167

sorry yim, that's not correct. momentum is not a square of velocity, but a linear function commonly referred to as P where P=mv NOT mv^2.

force is needed to change momentum. the relationship between momentum and force is determined by the time over which the momentum is changing. This is easy to see from the fact that acceleration is the change is velocity over time (a=v/t).

so... F=ma & a=v/t & P=mv
therefore F=mv/t (substitute for a)
and then F=P/t (substitute for mv)
This means force and changes in momentum are related in that a change in momentum requires a certain force, but this is related to the speed of the change (how quickly it happens) and not according to the square of the velocity of the object. It takes just as much force to slow a 10lb weight by 5mph in 5 seconds, regardless of how fast it was going when it started.

learn more about momentum here: http://en.wikibooks.org/wiki/FHSST_Physics_Momentu m:What_is_Momentum

(for all you physics buffs... i know i skipped the deltas - it just got too complicated)

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