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Suppose you conceal a small flywheel in a baseball (something that spins very fast with a lot of momentum for its size and weight). The coupling between flywheel and the outer skin of the ball is regulated (with a very light computer-controlled brake) so that it has a constant backspin. Can you use this design to cause the ball to fly for many minutes in a roughly straight line, until the flywheel is exhausted? (The ball does not need to pass an umpire's inspection! But I was hoping for it to make much further than the normal distance expected, using the power in the flywheel)

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    $\begingroup$ This reads like a engineering quiz more than it does a question about worldbuilding. $\endgroup$
    – sphennings
    Feb 25, 2022 at 15:15
  • $\begingroup$ Can you think of any other object without obvious fins or propulsion that can counteract gravity? How is a fairly smooth spherical object going to get lift (never mind maintain horizontal velocity) by rotating against the drag force, which will constantly decrease? The answer is clearly no $\endgroup$ Feb 25, 2022 at 15:31
  • $\begingroup$ While the ball does not need to pass inspection, does the initial throw (or pitch, or whatever) need to be observed? Or can the ball be launched from some kind of device at extraordinary speed, spinning at thousands of rpm? @Punintended is almost certainly correct that the Magnus effect will be insufficient, but let's see how bad it is. $\endgroup$ Feb 25, 2022 at 15:34
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    $\begingroup$ @Punintended, It's well known that putting backspin on a ball gives the ball a bit of lift. This is very obvious if you do it in a game of ping-pong. Less obvious for other balls in other sports. Google for "Magnus Effect" to learn more. $\endgroup$ Feb 25, 2022 at 20:31
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    $\begingroup$ @Punintended, You asked, "How is a fairly smooth spherical object going to get lift...by rotating against the drag force...?" I answered. $\endgroup$ Feb 26, 2022 at 14:21

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No

Note that I am drawing most of my conclusions from this extremely helpful article here. (I'm also gritting my teeth and using imperial units, given that these are used in all the baseball source documents.) The critically important part of the linked article specifies that:

In order to make a pitch really rise, one would have to be superhuman: below is the trajectory of a pitch with:

  • initial speed 110 mph
  • 3500 RPM of pure backspin
  • purely horizontal motion at time of release

So the first problem is that it is not possible to give the ball the initial conditions of velocity and spin required to allow it to defy gravity, the speed is slightly above the fastest recorded and the spin rate is about 25% greater than the fastest recorded. It might be possible for the flywheel to increase the rate of spin post-launch, but I'm not betting on it.

The second and greater problem is that regardless of the flywheel's efforts to maintain spin, the ball's forward motion through the air is going to be decreased by air friction. A helpful table from earlier in the same article gives the decrease in ball speed from release until passing over the plate for a range of initial speeds (apologies for the formatting):

initial horizontal speed final horizontal speed loss

100 mph 88 mph 12 mph

90 mph 80 mph 10 mph

80 mph 71 mph 9 mph

67 mph 59 mph 8 mph

The nice thing about this table is that the "final horizontal speed" of one line tends to be close to the "initial horizontal speed" of the following line. Which makes it clear that within less than two seconds the ball will have dropped to around half the speed that it needs to be moving at in order for the Magnus effect to completely counteract the downwards force of gravity. This is a big problem, especially as one of the conditions for cancelling out gravity in the initial stage of the trajectory was a "purely horizontal motion at the time of release".

Note that I am not even considering the technical aspects of creating the flywheel or ensuring that the ball is thrown so precisely that the entire Magnus effect force is directly in opposition to the gravitational pull. These are significant problems, but it won't help even if they are solved.

TL;DR - no, maintaining the spin rate with a flywheel does not help a baseball fly for sustained periods even if it is thrown with superhuman speed and spin initially unless some other unmentioned force continually accelerates the ball to maintain forward airspeed in the face of air resistance.

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  • $\begingroup$ Hmmm, that article suggests something else ... maybe make it a wiffle ball game. And add air jets pulsed through the holes. Definitely more maneuverable. Have to camouflage the innards slightly. And nobody expects a wiffle ball to expect in a blast of errant flywheel bits. The dreaded wiffle ball sound will haunt raider nightmares for years to come. :) $\endgroup$ Feb 27, 2022 at 23:30
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No

Gyroscopes, despite how mysterious they can be, are not anti-gravity devices.

The amount of lift achieved through backspin is quite minimal through the magnus effect, and is coupled to the speed of the ball. Due to drag, a horizontally thrown (or launched) object will slow down, meaning that even if the ball has an artificial backspin of arbitrary RPM somehow, it won't just magically stay in the air because the lift will decrease with the horizontal velocity.

In fact, the ball will probably fly about as far as it would with a regular, non-gyroscoped backspin pitch because rotational speed isn't what limits throwing distance; most balls with backspin are actually still spinning when they are caught or hit something.

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They can't

To boil it down to the most simple explanation. Without a flywheel inside a ball is already a sort of flywheel. It spins and thus exerts force to the air, causing it to light when backspin is applied under certain conditions.

A flywheel can add to the energy of the backspin, but as you're throwing a ball it would always be less efficient than simply making the ball heavier and giving it spin. The only advantage of the flywheel is storing some of the energy and releasing it later to the outside.

The spin has energy, determined by weight and the speed of the ball. Increasing weight also increases the energy required to stay aloft. So the flywheel should be light. But if it's light it stores little energy for it's rotational speed. Incredibly little energy. To make it worthwhile the flywheel will exceed most physical limitations, whether by the spin itself or the (near vacuum) housing it's in.

Even if you somehow succeed there's one more thing to worry about. The spin gets purchase on the wind, increasing drag. If drag increases the ball will slow down quicker. Slowing down means less distance, as well as decreasing the drag. Decreasing drag means it can't keep in the air through backspin.

It seems impossible to me.

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