Re: Need Numbers to Complete Crazy Idea Proposal...

In sci.physics, The Translucent Amoebae
<transamoebae@xxxxxxxxxx>
wrote
on Tue, 18 Dec 2007 13:07:52 -0800 (PST)
<2eaba4da-295d-480d-bc43-da891227ed1f@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>:
If you're just going to respond to this to add that this is a stupid
idea,
Then please try to restrain yourself...

OK

The idea is to put a single astronaut in a suit, or very small
capsule, into low Earth Orbit, for 2 or 3 trips around the Earth.
Cost ???

It's been done. We even got 12 men to the Moon (with an
additional 12 or 15 getting to orbit it).


First:
Build a HUGELY HUGE, REALLY HUGE, WITH THE IDEA OF BEING HUGE IN
MIND...
Helium Balloon Shaped like a Donut. Oriented while in use, so that the
Hole in the Donut is Perpendicular to The Earth. So looking up, you
could see Space, looking down, you would see The Earth.

An interesting notion but that would only take care of the height; it
would not take care of accelerating the individual to a speed of
8 km/s as required by low earth orbit.


Second:
You build a Platform under the Balloon with a common Rubber Tube
Slingshot attached,
So that when the Balloon is at it's apogee, which is aided by heating
the helium in the balloon,
You slingshot the astronaut into orbit, through the hole in the
balloon.

Ah, I see.

It would take an extremely large slingshot. At 10 "g"s
(1 g = 9.805 m/s/s; for simplicity I'll take 1 g = 10 m/s/s
here) and the requirement of a velocity of 8000 m/s, assume
a uniform acceleration (which might not be quite possible
with a slingshot, admittedly), and the acceleration time
required can be simply calculated:

v = at
t = v/a
t = 8000 m/s / 100 m/s/s = 80 seconds

and also the distance:

d = 1/2 a t^2
= 1/2 * 100 m/s/s * (80 s)^2 = 320 km

The assumption is that 10 "g"s is the maximum humans can tolerate
without damage (at 10 "g"s fighter pilots tend to take naps -- a
rather bad thing when going at Mach 3). At 1 g one gets 800
seconds (or 13:20) and 3200 km; this thing would be visible
all over the continental US.

Since Hooke's Law applies (a = kd, basically, as opposed
to a constant), these calculations are off, but one gets
the idea.

Of course energy has to be imparted to the band to distend it;
this energy can be approximated by noting that the force
required for 10g acceleration is simply F = ma or 10,000 Newtons
for a 100 kg individual [*]. This 10,000 Newtons (give or take)
is applied over the aforementioned 320 km, for a total energy
requirement of at least 3.2 GJ or 889 kWh. It turns out that
the 1 g slingshot would require the same amount of energy
(ignoring friction).

Compared to a rocket, that's not bad...but one does have
to hoist up the slingshot, and a 320 km slingshot looks to
be a rather massive affair. (Actually, the main problem
might be winching the balloon back *down*.)

One might also contemplate affairs such as electro-magnetic
railguns instead of a rubber-tube slingshot. Without
knowing the mass or the rigidity, I'm not at all sure
what's needed in terms of helium.


Third:
The Balloon is tethered to the Earth by a very strong fishing line, So
that the helium in the Balloon is cooled, and the donut is reeled in,
for reuse.

Cooling the helium has its own set of problems. Of course
one might contemplate simply compressing it into a
cylinder, essentially deflating the balloon (the balloon
cannot be fully inflated at liftoff as the gas expands
with the decrease in pressure) and therefore decreasing
the lift.

---
My original idea, before the fishing line idea, was to add some
shutters to the balloon that would close after use, and on their
surfaces, of the blinds, would accumulate enough space dust that it
would eventually descend to the ground, where the blinds would be
opened, to launch another astronaut into orbit...
But even i thought was stupid.

I'll give it points for innovation, but the engineering looks at
best difficult.


So--
Obviously this is a crazy idea, but i'm much more interested in how
difficult it would be,
That is; Just how much trouble would it be to make it work...
Rather than Negative Nellies just telling me to Shut Up.

Thanx!

[*] I could stand to lose some weight, admittedly. :-)

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