CNT or BASALT (whom needs a CNT tether if you've already got BASALT)

On Thu, 2 Oct 2003 01:40:17 +0000 (UTC), Ian Stirling
wrote:

In sci.space.policy Brad Guth wrote:
Obviously basalt fibers alone are not going to cut it for any ESE,
though maybe there's hope yet, as in utilizing a sufficient taper
should more than make the prospect of using basalt fibers at least
worth a consideration of a composite tether of perhaps 10% or even as
little as 1% CNT.

At least attempt to do the numbers, you innumerate ineducatable idiot.
snip
basalt density: a dense mafic rock (Fe and Mg rich silicate, density
2.8g/cm3)
Most sources I can find say 3-3.3
snip
Basalt Continuous Fiber Mechanical Properties
Tensile strength MPa 4840 (4.84 GPa)
Elastic modulus GPa 89
Elongation at break % 3.15

Blows rancid donkey spooge.

The figure of merit is tensile strength/density.
Basalt 4.84/3 = 1.61
Kevlar 4.1/1.76 = 2.32
Spectra 1000 3.27/.97 = 3.37

Spectra 1000 is over twice as good.
And it's way over the knee of the very sharp curve, where the mass/payload
is terrible.
Going from Spectra 1000 to basalt would I suspect increase the mass of a
tether by 5-6 orders of magnitude.

You need to get at least 10 times better than spectra before the curve
starts to get reasonable in terms of payload/mass.

Sure, Basalt may not be useful w/r/t spacecraft building materials,
but what about in body armor?

John

John Penta wrote:
On Thu, 2 Oct 2003 01:40:17 +0000 (UTC), Ian Stirling
wrote:
snip
basalt density: a dense mafic rock (Fe and Mg rich silicate, density
2.8g/cm3)
Most sources I can find say 3-3.3
snip
Basalt Continuous Fiber Mechanical Properties
Tensile strength MPa 4840 (4.84 GPa)
Elastic modulus GPa 89
Elongation at break % 3.15
Sure, Basalt may not be useful w/r/t spacecraft building materials,
but what about in body armor?

There the interesting number is the amount of energy it takes to break
the fiber.
(the weight may also become a factor, as to achieve a given level of
protection you'll need more of a fiber that can absorb less energy)

It looks on that basis better than both Spectra, Kevlar and Zylon,
assuming the elongation and tensile figures are accurate.
It's going to be around twice as heavy for a given protection.

--
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