RadioBanter - View Single Post

November 20th 04, 06:24 AM

In article ,
(William) writes:

Len, so one part of the project, the corner cube reflector, is easily
fabricated using inexpensive materials. Excellent. No need to bother
Kelly. I'm sure he's much too busy gearing up for field day or the
sweeps.

That "corner-cube" type of retroflector was once part of survival
rafts on USAF aircraft. Light enough to be lifted by kite (also part
of the raft).

Corner cubes can be highly irritating. At Rockwell, the optics
designer's mini-bull-pen had one made by one of the drafts people
from three flat mirrors. Whenever you were there and looked at
that one wall, regardless of position or at which table, you found
yourself looking back at you. :-)

Regarding the latex balloons, the little PIBAL balloons are not going
to get there, if those are the balloons that Mike is referring to.

Tsk. The ROI (Rules Of Engagement) in this newsgrope is that
everyone MUST do something they say. :-)

Well, I've told Mike that them surplus-store "latex weather
balloons" ain't going to do it, Kelly implied as much. But, if he
gets negative comments he goes all pouty and sniffly and
condemns the dastardly (if an NCTA) negative commenters as
trying to discourage him or that "it is impossible."

I
don't know what kind of fabric the rawinsonde balloons are made from,
but they routinely get to 100mb, and often get to 10mb (~30km). Mike
just needs to get whatever is currently available and go with it. It
will work.

Of course they will work. But, Mike (if he wants to be grande
"concept manager") should memorize the public info on Standard
Atmosphere tables before stepping into the self-declared CEO
(Creative Efficiency Officer) spot. CO$T is involved with this whole
thing...it ain't just filling cute party balloons at some state fair.
Just considering the Standard Atmosphere -

1. Atmosphere density decreases remarkably at altitudes above
around 10 kilofeet. A closed balloon envelope displaces only
so much atmosphere despite its size and the density (or
"weight") remains essentially the same. That provides one of
the upper-altitude maxima for the project...when related to the
payload weight.

2. Atmospheric pressure also decreases with increasing altitude.
A closed balloon envelope has to take that into account, either
by being only partly filled at launch altitude (envelope weight is
dependent on expansion capability, the unfilled part being just
dead weight at launch). Balloon envelope maximum size will
establish the maximum payload lift, having to correspond with
item (1.) and the lower of either altitude will be the limit.

3. Atmospheric temperature gets remarkably cold at altitude and
there's a roughly 70 C drop between altitudes of 10K feet and
100K feet. As temperature goes down, gas pressure will go
down and that impacts on both envelope structure strength
and displacement, thus a fine point on lifting capability.

4. There's been inadequate mention of the "lifting gas" availability
handling, and cost. Only one mention was made of a "typical
cost" at one locality...but not by the "concept manager."
Helium gas in heavy cannisters/tanks (high cost if not returned
to vendor) is readily avilable for welders' use (Heliarc welding).
That stuff is "safe" except that, as is, it is under a lot of
pressure which must be reduced somehow for filling relatively
delicate balloon envelopes. Hydrogen gas is available in the
same cannister/tanks but is highly flammable and may be
subject to some local rules on hazard materials' handling.
Low-pressure hydrogen can be produced easily by high school
science electrolysis very cheaply but large balloon envelope
sizes need a lot more of it than is done in classroom
experiments..

5. The slightest mention of BASICS involved in getting the balloon
and payload up at all is "discouraging the concept."

I think planning several launches, each with increasing difficulty, is
a way to tackle the problems and see what works and ~who~ works.

Concept managers don't have to concern themselves with
details. That's up to the serfs who do all the work, foot their
own bills, and have some idea of Standard Atmosphere data.
Concept managers have their CONCEPTS and that is the end
in itself. snort

Nothing sent aloft should be so valuable that it cannot be lost, and
expect losses. A receiver for the command burst, a beacon transmitter
for tracking and recovery, and a telemetry recorder (internal temp,
external temp, and pressure) will verify the attained altitude. He
can play with the cross-band repeaters, atv cameras, and hyperspectral
imaging during a later launch.

Absolutely so. Just the same, an off-the-cuff estimate of costs
per launch could go from $200 to even $500. depending on the
payload "science." As I said, this isn't inflating some party
balloons at a fair. Three words: Sponsors, sponsors, sponsors.

The problem of congested airways is still there. He might consider
having a trained group of DFers locally/College Station to recover the
package, and move his launch site and crew to Indiana to tame that
problem. If he does it with the Scouts, they are always mobile, and
actually like going places for a purpose. And Scouting opens doors
that might otherwise be closed.

All highly do-able if he gets the right volunteers and sponsorship.

Sponsors aren't going to buy into the "concept manager" stuff
unless there's something in it for the sponsor.

Now watch all the "noble" PCTAs chime in with "cockroach" humor
and the resident Gas Bag try to call others for one. Way to much
DREAMING of glories in here and not enough practicality.