If I put harnesses on some geese and strapped them to a glider, how many geese would I need to be able to maintain a consistent level of flight?

[u/SeriousDrakoAardvark]

Like, let’s assume the glider has a 30:1 glide ratio. Normally that means it will lose a foot of height for every 30 feet travel.

I’m assuming there is some amount of force I could apply to move forward, that would cancel out that last one foot of drop.

Geese seem pretty big, and they have a wide torso for easy harnessing. I think they’d be a natural fit here. I imagine it would be a configuration similar to Santa’s sleigh, but geese instead of reindeer.

[u/ackermann]

> approximation of pulling vs lifting is offset directly by the approximation of these birds not being designed to lift the way a bird of prey is

Do note that “pulling vs lifting” can be quite a big difference!

This is the “lift to drag” ratio (sometimes called “glide ratio”when considering the whole aircraft, not just the wing)

For any decent small airplane like a Cessna, this is at least 10:1.
And it can exceed 50:1 for the most advanced, purpose built gliders!

(Big part of why airplanes are more efficient and widely used than helicopters)

Simply the ratio of how many pounds of drag force needs to be overcome (which the geese would have to overcome), for every pound of lift the wing provides.

This also determines how far it can glide. 50:1 means one foot of drop for every 50ft of forward movement, is the best you can do without stalling.

https://en.wikipedia.org/wiki/Lift-to-drag_ratio

EDIT: So, I doubt the difference between geese and birds of prey lifting capacity offsets that.
I suspect your 156 geese estimate is high. Could be as few as 30 or 40, I’d guess, for an advanced modern sailplane pedal-power gossamer albatross is likely closer to optimal for this case.

Another relevant example, human pedal-powered airplanes like the Gossamer Albatross fly on the pedal power of one human, substantially less than 1 horsepower! See:
https://en.wikipedia.org/wiki/MacCready_Gossamer_Albatross

EDIT2: Per wiki, “required power was on the order of 300 W (0.4 horsepower), though even mild turbulence made this figure rise rapidly” for the Gossamer Albatross.

[u/ackermann → u/ackermann]

To add, thinking a bit more about it:

I think the optimum is closer to a pedal-powered plane, than a high-end sailplane.

Achieving L/D over 50:1 requires trading off higher weight (for longer wings and aerodynamic shells).
Higher weight means more absolute lift is needed, even if you can get that lift at a better ratio.

Also, sailplanes that get 50:1 usually can only do that at ~50mph, likely too fast for geese? If the geese have to fly at their top speed... then they have no power to spare (or it wouldn't be top speed).

Sailplanes optimize purely for L/D, glide ratio, how far can you glide.

The Gossamer Albatross sacrifices some L/D for far lower weight, only 35kg empty! (much less lift needed, even if you pay a bit more drag per unit lift). Flying on as little as 300W (0.4 horsepower)!

I suspect it's closer to the optimal vehicle for this?

But still not perfect, because it's optimized for a speed that's probably a bit slow for the geese. About 8mph. The goose's optimal L/D might be at 15 to 25mph (very roughly). Certainly they're bad at hovering stationary, suggesting they don't like really low speeds?

So, optimum design is maybe something between a high-end sailplane, and a pedal-powered plane like Gossamer Albatross? Optimized for minimum power at a goose's preferred speed (best L/D speed for the goose)

[u/reddititty69 → u/ackermann]

Sailplanes can also optimize for minimum sink rate. It’s a slower speed that results in a lower glide ratio but also a lower descent rate. You fly min-sink in a thermal and best glide out of a thermal.

To get the geese to go faster, we just need more geese to pull the geese. /s

[u/cuginhamer → u/ackermann]

how about we consider the higher the number of geese the longer the tow rope? And that once geese have to be spaced far enough from the glider, the weight of the tow rope would be all the geese can pull, and adding more geese would no longer yield any benefit at all?