Re: Re. Cell death from acceleration

As you point out the the human body cannot survive very large acceleration. However this has nothing to do with cell death and the limit can not be generally calculated.

Cells suspended in liquid medium are routinely centrifuged in biology labs to separate them from the liquid. The centrifugal forces used vary between a few hundred g and several thousands of g (1 g = gravitational force on surface of earth).

This is way higher than what the human body can survive. The problem of increased forces is the structural integrety that needs to be maintained. In a cell with small dimensions and contents that have similar specific density in an environment of the same specific densitiy, the acceleration force is similar on all components. That is certainly not the case for the human body, which lives in air, and contains air-filled cavities, fluid filled organs and even heavier bones. NASA has a good web-site [1] describing the effects on the human body and its organs. The effect depend on the orientation of the body: if you stand up, all the blood is going to be accelerated to your feets, resulting in visual symptoms (2.5-7g) and black-out (3.5-8g). This values were experimentally tested and on the range one can see that the effects vary a lot for individual human beings. Therefore it is not feasible to calculate the effects. If I think of the factors involved I would have to consider the tallness of the human being, normal blood pressure, strength of blood vessels, amount of circulation needed for normal brain function?

Laying down, g-forces above 20g were tolerated by some. Please look at the NASA site for more information.

As a site remark, the rule for the maximal acceleration allowed on amusement park roller-coasters is 4.5 g.

[1] Part II.15. "ENVIRONMENT OF MANNED SYSTEMS" of the SPACE HANDBOOK: ASTRONAUTICS AND ITS APPLICATIONS (staff report of the select committee on astronautics and space exploration).
http:/ /www.hq.nasa.gov/office/pao/History/conghand/mannedev.htm
addresses the problem of the gravitational force during acceleration onto the human body.