Steering with wind versus sunlight
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Q: A sailboat crew wants to reach a barrier reef around an island directly upwind, so the crew tacks the sailboat into the wind and follows a zigzag pattern to reach the reef. Now imagine that you are controlling a solar sail in space, and instead of wind the force available to you is sunlight. Is there any way you can move closer to the sun?
We developed this question with Bruce Betts, manager of The Planetary Society’s LightSail 2 program.
Draft a response of no more than 250 words and email it by 5 p.m. Eastern March 16 to email@example.com for a chance to have it published in the April issue.
INVERTED HELICOPTER FLIGHT:
We asked you to edit a screenplay passage about inverted helicopter flight.
WINNER: Unless the design is a full rigid rotor coaxial with negative pitch, it is unlikely the coaxial can remain in inverted flight more than a few seconds at best. R/C [radio-controlled] helicopters that are coaxial modify their rotor systems for this trick and do not have a mass such that the inverted flight condition causes coning of the blades. So an R/C model for the movie might work. Any current coaxial machine large enough to pick up a SEAL team would be subject to inverse coning, likely rotor strike to the tail structure, and only a minimal amount of negative rotor blade pitch. A Kamov helicopter might be able to pull it off for seconds before engine and transmission lubrication systems quit doing their jobs and the system would lock up. To date, the Sikorsky S-97 Raider has yet to demonstrate a full roll, let alone inverted flight. I worked with Red Bull pilot Chuck Aaron on engine issues for his BO-105 helicopter tricks — we worked out how many seconds he could stay inverted before the M250 oil system (highly modified for this machine) would dry up. But that one is not coaxial, so it might do the job for a few seconds.
David Newill, Associate Fellow
Newill has been a consultant to aerospace companies since retiring from the U.S. subsidiary of Rolls-Royce Defence in 2016. He leads the Indiana branch of the Rolls-Royce Heritage Trust, which restores and displays the company’s legacy engines and other artifacts.