[757labs] Balloon Record

[Trevor Lewis]

Looks like it would take about 0.35kg/m^3 of hydrogen to reach nearly 90km
(nearly 300k ft) where the mass of the balloon and payload are 10kg, the
balloon is spherical, and the material of the balloon is not stretched. (
http://www.grc.nasa.gov/WWW/k-12/Numbers/Math/Mathematical_Thinking/designing_a_high_altitude.htm)
[sorry, bit.ly is filtered at work...]

Wikipedia says that the edge of space is actually100km (the Karman Line
[respect mah authoritah!]). "Kármán calculated that above an altitude of
roughly 100 kilometers (62 mi), a vehicle would have to fly faster than orbital
velocity <http://en.wikipedia.org/wiki/Orbital_velocity> in order to derive
sufficient aerodynamic lift from the atmosphere to support itself..." (
http://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line)

So yeah, I guess there is a limit. After a certain point you're just not
going to be able to generate enough lift through displacement alone.

On Mon, Oct 24, 2011 at 11:09 AM, Eric Gearhart <eric at nixwizard.net> wrote:

> On Mon, Oct 24, 2011 at 11:01 AM, Angus Hines <3aih at angushines.com> wrote:
> > They were at 119K last time I checked yesterday and somewhere over WARSAW
> > !!!
>
> I wonder if there's some "barrier" at a certain altitude where the air
> gets so thin that it makes it really, really difficult to get past a
> certain altitude... sort of like the sound barrier. If I remember
> right, when they were first trying to break the sound barrier,
> turbulence and whatnot really ramps up as you get close... this was
> the big problem back in the late 1940s/early 1950s:
>
> "The term, which occasionally has other meanings, came into use during
> World War II, when a number of aircraft started to encounter the
> effects of compressibility, a collection of several unrelated
> aerodynamic effects that "struck" their planes like an impediment to
> further acceleration. By the 1950s, new aircraft designs routinely
> "broke" the sound barrier."
>
> --
> Eric
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> If we knew what we were doing it wouldn't be research.
>
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