Thread: How cool is VL2
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Old February 26th 07, 02:51 AM posted to uk.sci.astronomy,sci.space.history,sci.physics,sci.astro
The Ghost In The Machine
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Default How cool is VL2

In sci.physics, Brad Guth

wrote
on Sun, 25 Feb 2007 21:47:22 +0000 (UTC)
lgate.org:
"The Ghost In The Machine" wrote in
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Um...forgive me for asking such a stupid question, but since space is so
tenuous anyway how does one measure the temperature of a point therein?
A better measurement is insolation or irradiation, especially if
something is trapped in a bubble (e.g., a spacecraft with some air,
water, etc. in it).


It's all basic physics and math, either of which I'm not terribly good
at, but supposedly you folks are. So, why don't you tell us what a POOF
space station at VL2 is in for?

At VL2 you've got roughly upon the spectrum average of 2550~2600 w/m2,
less whatever's the shade provided by Venus (which is a serious bunch
of shade).


Somehow, I seriously doubt the VL2 point would get all that much shade.
But lessee.

http://en.wikipedia.org/wiki/Lagrangian_point

mentions the concept of a Hill Sphere, which has radius

r =~ R * cuberoot(M2/3M1)

where M1 is presumably 1.998435 * 10^30 kg, M2 4.8685 * 10^24 kg,
and R 1.08208926000 * 10^11 m. This gives r = 1.01 * 10^9 m.
At that distance the angular displacement of Venus, which has
diameter about 1.2 * 10^4 m, will be 1.2 * 10^-5 radian.
The angular displacement of Sol, which has diameter 1.392 * 10^9 m,
will be 1.286 * 10^-2 radian.

One should see Venus as a dot against the Sun, but that's about it.

Looks to me to be about a 0.0001% reduction in insolation -- which
is basically nothing.



Also, I'm not entirely sure but presumably the Venus L2 point is much
farther away than low Earth orbit, or the Moon, making for certain
logistics difficulties (and higher expense).


Each and every 19 months, your the same face of Venus that comes to
within roughly 100 fold the distance of our moon. Therefore, you could
damn near toss a moon rock at Venus, and expect that rock to eventually
hit that big sucker (though perhaps not until the next 19 month cycle).


Moon distance: 3.85 * 10^8 m
Venusian distance: maybe 4.2 * 10^10 m


Whatever the logistics wouldn't be at most 10% of accomplishing Mars,
perhaps not 1% of our actually accomplishing any viable base camp upon
our own nasty and otherwise global warming moon, and to think that you
wouldn't have to pack along hardly any spare amounts of shielding or
energy for surviving within your composite rigid waverider airship, or
otherwise for the 19 month stay within the relatively cool VL2 POOF, nor
would your mission be having need of all that much spare energy for your
return trip from VL2 to Earth because, your exit energy demand from VL2
would be next to nothing, other than the wussy gravity pull of the sun,
that's you're leaving behind at good velocity.

Put any one of our spendy orbital do-everything supercomputers to work
on it, and then give us that fully 3D animated GOOGLE/NOVA production
quality run-through.
-
Brad Guth




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