I have looked at many similar projects online and one of the things I noticed was that the payload and therefore the camera is tilted vertically and sideways most of the time.
From Alexei Karpenko’s Flight 2.
This payload is pushed by the wind, which is more or less strong depending on the altitude. The Jet Stream for example usually blows from 20,000 to 50,000 feet AGL (About 6,000 – 9,000 meters). At max altitude, the air pressure has dropped so much that I don’t believe there is much wind. Am I wrong?
The payload movements come from its balance, which is usually mediocre.
The good thing about it is that you can get good pictures at different angles (straight down or straight up) and get very valuable information on how the flight went. But that’s only a couple of pictures out of hundreds.
Most people have built it with a regular foam insulated box hanging from a balloon. I don’t think it’s the way to go. To take great shots, I need to keep the camera stable. The camera’s EIS Stabilizer will help, but I can’t just rely only on it.
Now How can I get the camera from moving too much?
This is where Aerial Photography shows its nose. Pierre Picavet invented a greatly used suspension system called after him Picavet. The Picavet suspension or Picavet cross provides a stable, self-leveling platform that resists twisting and swinging movement of a kite/balloon line.
Picavet Suspension Principle
Then for a balloon, I would need a spacer to control the level of the payload.
I don’t think I necessarily need the Picavet cross. I can attach it to the payload directly such as:
Each part must have a specific size for the stabilization system to work at best. It’s pretty easy to build or cheap to buy. You can find some simple kits here and there.
Now my only concern is … once the balloon explodes.
What will happen during the descent?
Have you see all those lines? The payload’s weight will drive the whole system down (picavet, spacer, radar reflector and parachute). I am afraid that this becomes a giant shitty mess during the way down, tangling the parachute and making it crash at full speed.
I think it’s worth the shot and that a problem with it should be easily identifiable during the tests.
What do you guys think?
Picture from Flight 2
A few comments for your project.
First of all good luck!
Regarding the photographs –
I have found from my launches you will want to mount your camera about 12 degrees down relative to the horizon for the best photographs.
Without something like CHDK to adjust the shutter speed and sensitivity of the CCD on your camera most all of the pictures will not turn out good. See http://chdk.setepontos.com/index.php/topic,2877.0.html for some pointers. An HD Video camera is a good option. I has success with the AIPTEK.
Regarding the GPS – Perhaps check out http://www.findmespot.com/en/
Many GPS chips do not work above 18KM due to COCOM limits.
http://en.wikipedia.org/wiki/CoCom
Worth note is that the limit is 60K feet OR 1000 knots (I presume to prevent the GPS from being used with an ICBM
)
Many chips do work above 60K feet so long as you do not exceed 1000 knots.
We used a small computer that radioed real time data over a voice radio to us on the ground. It is a reasonably simple setup and reasonably simple programming.
Files available from – http://shrumfamily.org/balloon2/
FILE0001.MOV – The launch and first hour of flight.
It’s
FI010001.MOV – The balloon pops at 43 minutes 15 seconds. The free fall begins!
FI030001.MOV – This video is from the top of a tree and includes video
of me pulling my ice chest down with a big yellow pole
probably not worth downloading.
You can see a need to address spinning in flight and notice that the big leftover balloon may get tangled in your parachute. It’s probably worht attempting to address thee issues.
Hi Don,
Thank you for your comment and congratulations on your second successful launch. I have looked into many of the problems you described. I will use CHDK with my Canon Camera and I am thinking about a GoPro HD for HD videos.
Unfortunately I don’t think the spot messengers work above 24Kft.
Your issue with the balloon is one of my biggest fear. I don’t really know how the balloon leftovers get tangled in the parachute. I am not sure a longer rope between the parachute and the balloon would be useful. Maybe a tensioner underneath the parachute…
I think that wind is pretty much a non-issue. The balloon is simply too big and too light to do anything other than move at the same speed as the wind.
I think most of the spinning and bouncing around comes because the payload is trailing beneath a huge ballon that’s pushing vertically through the air at a decent pace, and trailing large wake vorticies beneath it.
My pet theory is that you can fix a lot of this by just running a _long_ tether (think 20 meters) to the payload to move it out of the worst of the wake.
Thanks Michael for your comment.
I agree with you that vortices is probably the main component of wake turbulence at high altitude.
After thinking about it, I will probably give up on my Picavet Theory and go for a long tether. But 20 meters is very long and somehow makes me feel uncomfortable. I have seen many examples where such a length caused many problems after the balloon burst. 10 meters sounds good enough but I will look more into it. Thanks for your input!