Re: minsky vs solar sails

Ron Kean (
Mon, 26 Jul 1999 08:31:27 -0400

On Sun, 25 Jul 1999 19:02:13 -0400 "Michael S. Lorrey" <> writes:

The gravitational attraction is only important if sailmass X gravitationalacceleration > solarwindmass X windvelocity^2. The lighter the mass of your sail versus the area, the better.

Mike Lorrey

Mass X acceleration equates to units of force, but mass X velocity^2 equates to units of energy. Since 'impulse', which is force X time, equates to momentum, which is mass X velocity, force equates to [mass X velocity] / time.

So, would it not be more correct to express the inequality as

sailmass X gravitationalacceleration > [solarwindmass / time] X windvelocity,

so that the units balance?

In other words, if mass is impacting a target at the rate of one kilogram per second with a relative velocity of one meter per second, and if the collision is non-elastic such that all the momentum of the impacting mass (relative to the target) is transferred to the target, the force imparted to the target is one Newton.

Ron Kean




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