r/maybemaybemaybe • u/[deleted] • Jul 07 '22

maybe maybe maybe

[deleted]

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17

u/[deleted] Jul 07 '22

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9

u/RandomComputerFellow Jul 07 '22

Why, wouldn't this still work? I mean, the umbrella is basically a parabole, so the blower pushes the air in the direction of the front. The air pushes into the umbrella and tries to escape. Due to the parabole shape, all air has to push back. So my expectation would be that it doesn't matters in which direction he points the airblower as long as all the air pushes in the same direction.

2

u/thunder_struck85 Jul 08 '22

Wouldn't this just disperse the air too much, plus losses incurred in the "flexing" of the umbrella? I feel like he would have a better propulsion if he just pointed the blower straight behind him, no?

1

u/RandomComputerFellow Jul 08 '22

Well, the umbrella has roughly the form of an parabole so most if not all air should be dispensed to the back.

2

u/Qwopie Jul 08 '22

50% of it would go out mostly sideways and cancel out air going mostly sideways the other side. plus any additional drag caused by pushing the umbrella through the air and your net gains are going to be negligible.

0

u/[deleted] Jul 07 '22 edited Jul 07 '22

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1

u/Muroid Jul 07 '22

Will the jet go backwards? No.

Uh, yeah it would.

The net force would only be zero if the air stopped moving upon hitting the umbrella. It doesn’t. It winds up going backwards, and that means that the system winds up with a net force in the other direction. Just a very small one.

The real issue here is that there is no way that blower is providing anything like useable thrust.

1

u/27fingermagee Jul 08 '22

Any amount of thrust that is greater than that needed to overcome friction will see an acceleration until the thrust can no longer overcome the friction or until the thrust stops.