Spike Jones wrote:
>
> > Amara Graps wrote: Misner, Thorne, and Wheeler in _Gravitation_ ,
> > use "c=1 units" throughout their text, I think. (I don't have that book...
>
> I wish to propose a metric: tensile strength as a function of density, call
> it specific strength. Strangely enough, the units come out to the square
> of velocity, m^2/sec^2:
>
> pa/{kg/m^3}={N/m^2}/{kg/m^3=Nm/kg=kg*m^2/kg*sec^2=m^2/sec^2
>
> Nowthen, we want to make a table of specific strengths* of various
> materials in terms of m^2/sec^2. Question: has anybody heard of
> such a technique before? I cant find it in any of my materials science
> texts, but it seems obviously useful for topics like the space cable and
> such. Doug? Anybody?
Hmmm... the only other concept with those units that I'm familiar with
is excess escape energy per mass, for spacecraft on a hyperbolic
trajectory, C3 in the nomenclature. It's typically quoted in km^2/s^2
to get convenient sized units without too many zeroes, or need for
exponents.
As for specific strength, it's more sensible to quote it in unreduced
units- pressure per density is the "significance" of the unit, while v^2
is accurate but obfuscatory. I think I've seen tables of specific
strength in a handbook of engineering materials.
> * strengths: theres a world with 9 letters and only 1 vowel. Is that the
> only word like that? spike
ISTR that that word is the record for an overworked vowel in English.
-- Doug Jones Rocket Plumber, XCOR Aerospace http://www.xcor-aerospace.com
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