High Altitude Balloon Flight 2

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With a fresh cylinder of helium on hand and the payload ready to fly again, I was waiting for a nice weekend day so Joel and John could get in on this flight. While the forecast had called for clear skies, the wind was predicted to be a bit brisk. Providing we could handle the inflated balloon on the ground, there weren't really any wind restrictions once the balloon was released. So on Friday night I called everyone letting them know I was planning a dawn launch on Saturday morning.

I wanted to try to make 75,000' on this flight, that's the official start of what's known as "Near Space". This balloon was another one of my 20 year old surplus balloons, so getting peak altitude out them was likely going to mean doing all I could to push the last few thousand feet out of the old balloon. With that in mind, I decided to drop the payload weight. Dropping payload weight means less balloon volume on the ground, so it has more expansion capacity to get higher in the atmosphere. I could also get by with a little less free lift, causing the balloon to go up slower, but again, allowing for more expansion at altitude.

I didn't use the cut down system for this flight, and I dropped the VHSC camcorder as well. That lowered my payload weight to about 4.8 pounds. What I did add to the payload, was a small end of a willow tree branch for Ryland, who wanted to know what would happen to a living plant. And I added three quarters taped to the inside as souvenirs, providing a successful flight...

John was the first to arrive, I had already set up the tarp and blanket to work on, and had the helium tank and fill line set up. So John and I donned our latex gloves, and started filling the balloon. Having done this once before really helped, and the fill process went quickly and smoothly. Joel showed up just before filling was completed. While Joel and John finished filling, I set up the payload, tested the homing beacon transmitter and the GPS radio modem transmitter. Once the filling was complete, the last thing to do was to turn on the camera. For some unknown reason, the camera shutter release wasn't working very well, it was triggering the solenoid, but wasn't always triggering the shutter on the camera. So at the last minute I decided to run the camera in video mode, at least getting the better part of the ascent before the memory card filled.

I did overfill the balloon again. I intended to stop filling at a measured nozzle lift of 6.8 pounds. Considering the fill line adds about 1/2 pound, that would give me a true nozzle lift of 7.3 pounds and 2.5 pounds of free lift. I ended up filling to 8 pounds of measured lift. I'm sure that extra 1.2 pounds of lift cost me some altitude, but it does make for a faster flight. I decided to attach the parachute to the payload suspension lines, rather than at the apex of the chute like I did in the last flight. I've seen it done both ways, and just wanted to see for myself how it worked. I was also a little concerned the weight of the balloon remains after burst would dump the small 36" parachute. So it seemed a little safer just to dangle the chute over the side of the payload for this flight.

The balloon was somewhat unwieldy in the 10 to 15 mph winds, but still it was manageable with two people handling it.

John at the end of the fill process.

Just about ready to release the balloon.

Away goes HAB2!

As the balloon takes off in the brisk wind, you can see the chute opened up and trailing under the payload.

Click Here for a 7 minute edited video of the launch, a couple of minutes at altitude then a couple minutes of the landing. Watch for a time frame of 4 minutes 20 seconds, that's the moment the balloon burst. The in flight video is very poor quality, and take care you have a good stomach because it does a lot of spinning.

I had checked the upper level winds before we launched. While there was a ground breeze, the wind was calm around 9,000'. So we weren't in a big hurry to chase it down. In fact, we dropped off Joel's car at a repair shop, then stopped at a convenience store for a quick breakfast before leaving town. By the time we got on the highway, the balloon was about 5 miles out, but I had a strong signal and all looked well. We rather leisurely followed the balloon track as best we could. At one point, with the balloon at some 60,000' we had to do an end around as the balloon changed course and we needed to find a good road. That put us about 7 miles down range, but I never lost the signal from the radio modem.

Once we were back on track, we stopped about 2 miles from the balloon and watched the data coming in. We had exceeded the last flight already, as we were over 65,000'. I watched as the thousands of feet increased. We all tried to guess the burst altitude. Joel said 72 thousand. I said no, it has to make to at least 75,000'. I have to make my "Near Space" on this flight. The computer read out 73,000', Joel was wrong, I started getting a little nervous, we might just make it yet... Then 74,000'... Then we passed 75,000', hurray we made it! Not by much though, just after the GPS reported 76,000' I noticed the altitude dropping.

One thing I did notice, the descent was decidedly faster than the first flight. Joel was driving, and he was driving at the leisurely pace he had on the way out, I told him to kick it just a little as we wanted to be as close as possible to the landing site. We stopped a couple of times and tried to pick up the homing beacon, but didn't get anything the first couple of tries. Then at about 25,000' I picked up the homing beacon. According to the GPS and map on my computer, the payload should have been almost parallel to the road we were on. So we sped down the road to get closer, from the back seat I announced we should be able to see it now, and told the guys in the front seat where to look. Sure enough, after a few seconds John sighted the payload and chute. That was really cool, being able to get under it and see it land! I did use the beacon to home in on it. But it wasn't really even needed, the payload had landed about 20' from a dead end road, and we pulled right up to it.

Here's the payload as it was found.

So it was another nice landing and this time an easy recovery. We were getting close to a rough area again though. If you look into the distance in the above picture, that's the same area as the first balloon landed, only about 3 miles to the Southwest.

Here's the map overlay of the balloon flight. The green is the first flight, this flight is the pink track.

Here's some details of the flight:

Launch Time: 6:16:59

Burst Time: 7:26:12

Landing Time: 8:00:24

Time to Burst: 1:09:13

Time from Burst to Landing: 34:12

Peak Recorded Altitude: 75,950'

Average Ascent Rate: 1,087 fpm

Average Descent Rate: 2,227 fpm

So ends my first series of high altitude balloon flights. The GPS radio system works better than I could have hoped for. I'm confident now of flying this system in a large rocket. Ryland's plant was, as expected, frozen solid. Everything inside the payload felt like it had been in a deep freeze for days. I had, just to see if it would help, thrown a couple of hand warmers in the payload box. The thing is, they are air activated, or oxygen activated I suppose. And there isn't much of either up at 75,000'. As soon as I opened the payload I grabbed one of the hand warmers, not only was it not warm, it was ice cold! I do have my quarter souvenir from near space though!

As for the video recorder, on the way home I watched the first 30 minutes or so on the camera itself. So I knew I had some video at least. But when I tried loading the video into my computer, the file was corrupted. So I didn't know for sure how much video was recorded. My guess was that at some point something happened to stop the recorder, and it didn't get to write the info to end the file. So I download a some free index repair software off the net, and quickly had the file repaired and now readable by my PC. I was pleased to find the entire flight and landing had been recorded. The camera turned off at the moment of landing. I suppose the battery contacts lost connection for a moment. That is one problem I've had with these cameras. For extra security, you really need to solder an external battery pack to them. I'm not going to post the entire video file, it's way too big and such poor quality no one would want to watch it all anyway. I edited it to just the highlights and posted it earlier.

I don't have any more balloon flights planned at this time, that's not to say I won't do more down the road. This really is pretty easy to do, and a lot of fun. So I'm sure by next Spring I'll have the itch to fly another one. With a new balloon I should be able to push 100,000'.

I thought it would be interesting to plot out the ascent rate of the balloon. The trend seems to indicate the balloon picks up speed as it ascends into thinner atmosphere, then slows down above 40,000'. I suppose that's due to the balloon stretching and the increasing resistance of the material itself, and due to the fact that the change in pressure is less the higher the altitude.

Here we have a plot of the descent rate. As expected, as air density increases the descent rate decreases. The payload weighed 4.8 pounds, and I weighed the remains of the balloon that stayed with the payload at 2.6 pounds. Of course the Styrofoam cooler had surface area to slow it's descent, and the balloon remains would have had an additional slight drag force. The chute was a flat circular and 36" flat diameter. Upon landing the payload was traveling at 22.16 fps.

The GPS Trackmaker software can convert files in many different formats for exporting into other applications. Here I've exported the data to a format Google Earth can read, you can see the flight path plotted over a satellite view of the area.

Here's one more image showing my map faded over the Google Earth map. You can see how accurate my map is compared to the terrain. You can see the blue track of the balloon as plotted by Google Earth, with my plot inside it as a darker line. Just amazing isn't it?

Thanks to Greg Burnett for showing me how to get a 3D view from Google Earth! HAB1 is again in green, HAB2 in pink.