craig at craigturner.id.au
Wed Jul 19 15:09:42 EST 2006
I'll try to answer some of your questions below. I'm going around to
Al's place tonight to do our 'systems integration' and discuss some of
the issues you raised below.
Al (who is the balloon designer) believes that 40'000 feet is quite
achievable. The balloon will remain aloft as long as it receives heat
from the sun. The higher it goes the longer it will receive the suns
rays. At 40'000 feet, that could be an hour or so after sunset at ground
Al thinks that even after the balloon begins to loose heat, its descent
will be quite gradual and could take another hour or so from
commencement of descent to actual landing.
Apparently the low altitude winds from our launch site will take the
balloon N/NW during ideal launch conditions. Unfortunately there is
generally only one kind of prevailing wind at the higher altitude, and
that is to the East (and out to sea!) Apparently winds in excess of
50kph are to be expected.
For this flight I want to launch quite late in the day, to reduce the
amount of time the balloon will head East, and the distance that we have
to drive to retrieve it.
We do expect the payload to land gently, as the balloon envelope will
cool slowly, and even if the balloon rips, its a fairly large piece of
plastic, so it should act as a parachute. My main concern here is a
problem with how the payload is attached to the balloon (ie the mouth of
the balloon tearing.
As for the power budget,
The manual for the Maxon claims that it has a standby draw of 35ma, a
receive of 150ma and a transmit of 1100ma for 5w. Mine is currently set
for low power, which is below 2 watts, not sure what transmit draw is
for 2 watts, 450ma?
Using a Tinytrack3 and a Deluo GPS. I am using two 1.2ah battery's in
parallel. Using a single 1.2 ah battery I was getting about 5 1/2 hours
with a beacon every 2 minutes. My real concern is battery performance at
altitude. I have read that using a clear container actuall helps to keep
the load warm. There appears to be two schools of thought. Insulate the
load and let the internal power consumption help keep the payload warm,
or let the sun heat up the interior by using a clear container.
I really wanted to have a second beacon of some form operating on
independent power, but study/work comittements and time have intervened,
and we are going to go for it as it stands, weather depending!
Richard Hoskin wrote:
> Gday Craig,
> This is a great project!
> I have a few questions on some of the details that you may be able to
> What do you expect the direction of flight to be?
> What distance do you think the balloon may travel?
> What is you estimated flight time?
> Do you expect the balloon to land gently?
> What's the standby current of the Maxon and your power budget?
> There is some talk of another balloon project in VK3 latter in the year.
> would be great to learn a bit from your project.
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