Is it scientifically feasible to create a boot that could soften a 30 m fall?

Main Question or Discussion Point

It would probably require some sort of leg attachment to relieve the stress on the knees and ankles. Is it within the realm of possibility?

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256bits
Gold Member
Lets see
v^2 = v0^2 + 2 a d
v^2 = 0 + 2 * 9.81 * 30 m =
v = 24.3 m/s at the ground

Assuming your feet hit the ground and your butt continues for 1 m as the shock is absorbed, your deceleration is:
a = v^2 / (2d ) = 24.3^2 / (2 * 1 ) = 294.3 m/s^2 ( which is 30g )

t = v/a = 24.3 / 294.3 = 1 tenth of a second for deceleration.

I think you would need also braces for your spine and neck after you end up in the hospital, irregardless if you had an extra cushioning shoe.

Be one hell of a damper , and some stiff springs.

How many Gs can the average spine of a fit and physically active person sustain?

How many Gs can the average spine of a fit and physically active person sustain?
Well, modern ejection seats do a bit over 10, and there is a lot of discussion about how ejections are pretty stressful on the pilots, who are of significantly-above-average constitution --so I think its safe to say the answer is something under 10.

The yield strength of bone is between 104-121 MPa, the ultimate tensile strength is 130 MPa. So you would need a damping system to absorb at least that just to keep bones safe

Is it scientifically feasible to create a boot that could soften a 30 m fall?
If you are willing to think outside the box it is feasible. The problem is that we have to reduce the person's speed from some high value obtained from falling to zero without doing any damage. If we decelerate him over a longer time (which means over a longer distance), then you can have a lower (and safer) deceleration rate. For instance if the sole of the boot could instantly inflate to a 3 meter high system of air bags, you could do it. But at that point it's just more practical to have a parachute. Or if the boots had carefully controlled rockets or jets on the bottom (think VTOL aircraft), you could do it. If you are just thinking of a standard half-inch boot sole that is bouncy enough, that's not going to happen.

Ryan_m_b
Staff Emeritus
Assuming your feet hit the ground and your butt continues for 1 m as the shock is absorbed, your deceleration is:
a = v^2 / (2d ) = 24.3^2 / (2 * 1 ) = 294.3 m/s^2 ( which is 30g )
If you are willing to think outside the box it is feasible...
It's going to have to be very outside the box, the average person can take about 5gs vertically before passing out (fighter pilots with acceleration suits still only manage 9). The effects on the body are going to be pretty much impossible to negate with a simple foot landing.

Perhaps if the boots were fitted with sensors to measure acceleration and distance from the ground they could then be made to extend stilts. Perhaps similar to collapsible, long https://www.google.com/search?q=poweriser&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&biw=1366&bih=667&sei=b8XCTtm5OcSW8gPVud26Cw".

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You could also make the boots humongous and out of a light material, that way you could air surf to the ground.

Bandit127
Gold Member
Lets see
v^2 = v0^2 + 2 a d
v^2 = 0 + 2 * 9.81 * 30 m =
v = 24.3 m/s at the ground

Assuming your feet hit the ground and your butt continues for 1 m as the shock is absorbed, your deceleration is:
a = v^2 / (2d ) = 24.3^2 / (2 * 1 ) = 294.3 m/s^2 ( which is 30g )

t = v/a = 24.3 / 294.3 = 1 tenth of a second for deceleration.

I think you would need also braces for your spine and neck after you end up in the hospital, irregardless if you had an extra cushioning shoe.
24.3 m/s is roughly 55 mph. If you could achieve the deceleration that the front of a car achieves over the same 1m distance you would probably survive.

So, boots with crumple zones and airbags.

By definition, they would have to be 1m high as your ankles, legs and knees are not crumple zones and would collapse under the force - coupling your bum with the back of your legs before the crumple zones in the boots would take effect.

What if we reduce the height to 10m?