The failure of the “beat the ancestors” attempt to safely drop a motorcycle from a crane makes me wonder.

What is the ideal energy-absorbing material?

Energy absorbing mechanisms include brittle fracture, crumpling, solid-solid friction, torsion and bending (in springs), rubber, high viscosity liquid, low viscosity liquid, water turbulence, thin layer fluid, shock absorber, gas compression, air bags, styrofoam, puffed rice, bubble wrap, gas turbulence, aerogel.

All of these energy absorbing mechanisms have been used in one way or another, for example a tank of water is effective at absorbing the energy of a bullet, and a tank of water is also effective in dissipating the energy of wind-induced skyscraper vibration.

Is there such a thing as an ideal energy-absorbing material?

If there is such a thing as an ideal energy absorbing material then it would be capable of creating a uniform deceleration of ‘n’ Gee over a distance of ‘d’ metres, given an initial mass ‘m’ and velocity ‘v’. The uniform is essential, for example buckling is an energy absorbing mechanism but its energy absorption is very non-uniform, starting with high deceleration and rapidly dropping to zero deceleration.

Let’s take a specific example. Drop a car from an aircraft without a parachute. Say m = 1000 kg at v = 70 m/s that you want to decelerate at ten gees, a = 100 m/s^2. The energy absorbing material has to produce a constant resisting force F = ma = 100 kiloNewtons.

Which material?

(Um, did that problem just require 24 metres of uniform deceleration to stop the car? If so, change numbers to something more reasonable)

Sorbothane?
Maybe not the idea material, but it’s pretty good.

mollwollfumble said:

The failure of the “beat the ancestors” attempt to safely drop a motorcycle from a crane makes me wonder.

What is the ideal energy-absorbing material?

Energy absorbing mechanisms include brittle fracture, crumpling, solid-solid friction, torsion and bending (in springs), rubber, high viscosity liquid, low viscosity liquid, water turbulence, thin layer fluid, shock absorber, gas compression, air bags, styrofoam, puffed rice, bubble wrap, gas turbulence, aerogel.

All of these energy absorbing mechanisms have been used in one way or another, for example a tank of water is effective at absorbing the energy of a bullet, and a tank of water is also effective in dissipating the energy of wind-induced skyscraper vibration.

Is there such a thing as an ideal energy-absorbing material?

If there is such a thing as an ideal energy absorbing material then it would be capable of creating a uniform deceleration of ‘n’ Gee over a distance of ‘d’ metres, given an initial mass ‘m’ and velocity ‘v’. The uniform is essential, for example buckling is an energy absorbing mechanism but its energy absorption is very non-uniform, starting with high deceleration and rapidly dropping to zero deceleration.

Let’s take a specific example. Drop a car from an aircraft without a parachute. Say m = 1000 kg at v = 70 m/s that you want to decelerate at ten gees, a = 100 m/s^2. The energy absorbing material has to produce a constant resisting force F = ma = 100 kiloNewtons.

Which material?

(Um, did that problem just require 24 metres of uniform deceleration to stop the car? If so, change numbers to something more reasonable)

Having given this some thought, I think the ideal energy absorbing material is air. We just need a surface large enough to develop sufficient air resistance, and not call it a parachute.

I saw that episode and think they made a mistake, the rocket thrust equaled the weight of the pallet and equipment but if it is to brake something falling shouldn’t it be more than the weight of the pallet at rest?

As for energy absorption the cardboard or other shock absorbing material should have been under the equipment so crumple zones go pallet first then shock absorbing material then items. Speaking of the pallet I think it was over strength, they needed it to fall apart not remain rigid.

The rocket possibly could have been above the pallet with the pallet swinging of it, that would remove balancing problems, bit like the escape rocket on Saturns.

AwesomeO said:

I saw that episode and think they made a mistake, the rocket thrust equaled the weight of the pallet and equipment but if it is to brake something falling shouldn’t it be more than the weight of the pallet at rest?

pe equals Ke

by rights when the pallet has reached the ground it’s Ke equals the original stationary energy of Pe

you’d need to make sure the rockets weren’t destroyed though

maybe egg shell with a given shape of an egg

ive seen helmets made from cardboard in the past

The Rev Dodgson said:

mollwollfumble said:

The failure of the “beat the ancestors” attempt to safely drop a motorcycle from a crane makes me wonder.

What is the ideal energy-absorbing material?

Energy absorbing mechanisms include brittle fracture, crumpling, solid-solid friction, torsion and bending (in springs), rubber, high viscosity liquid, low viscosity liquid, water turbulence, thin layer fluid, shock absorber, gas compression, air bags, styrofoam, puffed rice, bubble wrap, gas turbulence, aerogel.

All of these energy absorbing mechanisms have been used in one way or another, for example a tank of water is effective at absorbing the energy of a bullet, and a tank of water is also effective in dissipating the energy of wind-induced skyscraper vibration.

Is there such a thing as an ideal energy-absorbing material?

If there is such a thing as an ideal energy absorbing material then it would be capable of creating a uniform deceleration of ‘n’ Gee over a distance of ‘d’ metres, given an initial mass ‘m’ and velocity ‘v’. The uniform is essential, for example buckling is an energy absorbing mechanism but its energy absorption is very non-uniform, starting with high deceleration and rapidly dropping to zero deceleration.

Let’s take a specific example. Drop a car from an aircraft without a parachute. Say m = 1000 kg at v = 70 m/s that you want to decelerate at ten gees, a = 100 m/s^2. The energy absorbing material has to produce a constant resisting force F = ma = 100 kiloNewtons.

Which material?

(Um, did that problem just require 24 metres of uniform deceleration to stop the car? If so, change numbers to something more reasonable)

Having given this some thought, I think the ideal energy absorbing material is air. We just need a surface large enough to develop sufficient air resistance, and not call it a parachute.

I recon the ideal energy absorption material is politicians, and it doesn’t matter which party they are members of.

not a material, but variously electro…. fields too