The Search for our Missing Balloon: Closing in on the Landing Zone

In late May, Jared Sabater of Soleil Multimedia and I launched a high altitude balloon from south Chapel Hill, North Carolina. The balloon was carrying three cameras to capture spectacular high resolution video images of North Carolina from 20 miles in the air. We also expect to see the black sky of near space and a slightly curved horizon. However, the satellite tracker package fell off immediately after launch, and the balloon — cameras in tow — disappeared into the sky.

We set off to the expected landing zone — Harnett County, North Carolina. Needless to say, the search made looking for a needle in a haystack sound easy, and we returned home with nothing. I posted a desperate plea on my blog (read it here) and crossed my fingers, hoping someone would find the payload and get in contact with me. A reporter from the Daily Record in Dunn, North Carolina, came across my blog post and wrote a story about it.  A day later, I got a call from a woman living in Coats, North Carolina.

“I saw your balloon,” she said.

I didn’t believe her at first.  The balloon was supposed to pop in the stratosphere, not come down intact.  She said she saw it at sunset, a full twelve hours after launch — I figured it should have been way out in the Atlantic by then.  But as she described what she saw, I realized that there were only two possibilities:
1.  She saw our balloon.

2.  Someone else launched a high altitude balloon that just happened to come down in Coats.

The probability of #2 is vanishingly small — smaller even than #1, so I was forced to conclude that, in fact, our balloon was somewhere by Coats.  Jared, my friend Xiao, and I drive out to Coats to talk with the witness.  She was wonderfully nice and amazingly observant.  We stood by the window from which she saw the balloon, and she started telling me what she saw.  First of all, her pastor had also seen it crossing a road to the north, so we had a bearing.  Second, she said it had something sticking off to the side.  Third, it had remained in the same place for about an hour.

I didn’t know what to make of the second and third statements.  Balloons don’t fly with things sticking sideways, that makes them unbalanced and they tend to rotate so that whatever it is sticks straight down.  Also, even when the wind is imperceptible at the Earth’s surface, it’s strong enough above the surface to move the balloon out of her viewing area in less than an hour.

That’s when I realized what she’d seen:  Our balloon had already landed by the time she glanced out her window!!

It was simple in retrospect.  By the time the witness looked out her window and saw the balloon, the payload was on the ground or snagged in a tree.  The balloon envelope was still buoyant, hanging above the landing site like a giant flag — pulled slightly sideways and hooked over by the wind (hence the thing sticking out) and more or less stationary (why she was able to see it for an hour in the same place).

Here’s what we know right now:

The balloon envelope is cream to reddish colored and probably up to 20′ across.  It’s likely shredded into bits due to UV light and wind action.  The payload is 40′ from the envelope in a red lunch box with cameras attached.  The envelope is likely draped over a tree, and the payload is probably in the upper branches of another tree.

The area visible to the witness starts at 35.389756 N latitude, 78.638441 W longitude, and extends due east.  We can define sight boundaries by using buildings and trees that obscure her view to the east and the west (see figures below).

We searched several fields in the sight line and didn’t find anything, so the payload’s likely in forested areas.

Another witness saw the balloon crossing Red Hill Church Road at very low elevation, heading towards the first witness’ house, so that road defines a hard eastern boundary to the search area.

The first witness says the balloon was west of Black River – this provides another search area boundary, but with less confidence.

Elevation profiles (see below) and distances to the Black River make it even more unlikely that the witness could have seen the balloon on the ground if it were in the Black River valley.

Here are a series of maps of the search area:

view_areaThe red triangle defines the region visible from the first witness’ house, with the east boundary defined from the road which the balloon crossed per the second witness’ description.  Green polygons enclosed regions we were able to search on our first trip out to Coats.  The pale blue arc is 1 mile from the first witness’ house.  It’s hard to imagine being able to make out as much detail as she reported if the balloon is beyond this circle.

Elevation profiles along the north and south sight lines are available here:

north

south

These profiles suggest that the Black River area would be difficult to see from the first witness’ location.

landing_zone

The four yellow polygons show the most likely landing zones based on the analyses described above.  Areas A and B are by far the most probable locations for the payload, based on the witness’ statements and distance from where she saw it.  Any search should carefully investigate these regions.  Area C is also possible, but rather less probable because it is significantly below (and thus probably invisible from) the witness’ house.  Also, it’s quite far away, which would make the details she described hard to see.  Finally Area D cannot be eliminated, but it is the least likely due to elevation and distance.

Our next step is to go out and search.  If you’d like to join, or if you have some other information for us, let us know!

Advertisements

Anyone seen a red lunch box with cameras attached?

Catastrophe!  Yesterday, while launching a hydrogen balloon in Chapel Hill, North Carolina, our satellite tracker fell out of the payload.  The camera box, however, cheerfully continued its ascent into the wild blue yonder.  The result?  There is a red lunch box with three cameras in it somewhere in North Carolina.

Detailed description of payload as it will appear on the ground:

Shreds of mylar and a balloon nozzle, followed by a 40′ string, then a plastic parachute (may look like a plastic bag from far away).  Another length of string approximately 10′ long, followed by a red lunch box with “Solar Balloon Payload” and my phone number written on it.  The lunch box has three cameras, one pointing down, one pointing out the side, and a smaller one pointing up.  A milk jug with a sticker saying “Soleil Multimedia” may also still be attached.

The projected landing zone was in north/northwest Harnett County.  I believe that is reasonably accurate.  So our payload, with spectacular footage, is somewhere out there.  I want it back.

Here’s a couple of potential flight trajectories:

Trajectory 1

Trajectory 2

Trajectory 3

If you have any information or know anyone in the region who might be able to help, please contact us.

A Hydrogen-Filled Weather Balloon Flight into Near Space

We describe a hydrogen-filled weather balloon launch in central North Carolina, and present a video, still images, and data from our GPS data logger.

Launch and Flight Video:

A view from our still camera aboard our weather balloon.

A view from our still camera aboard our weather balloon.

This flight was designated “Jake 7”, as it is our seventh tracked balloon launch attempt (5 successes, 2 failures so far).

Our goals: get video, test using hydrogen instead of helium for lift gas, try launching in close proximity to the ocean without losing the balloon, use a plastic rather than nylon parachute, and have a faster descent rate than on previous launches to cut down on flight distance.  We were also excited to get latitude, longitude, and altitude from launch to landing (our most recent flight before this one was deliberately cut down at 20,000 m, and that time the GPS only started tracking at 10,000 m).  We were not going for a spectacularly high altitude during this launch because the jet stream was blowing towards the Atlantic at 100 miles an hour.

The GPS flight data can be downloaded here:  jake7_flight_data.txt

Results at a glance:

-Hydrogen is great.  It’s cheap-currently 1/3 the price of helium and weighs less, meaning more lift.  I got a 200 cubic foot hydrogen tank for about $70, including 10 days of tank rental.  Hydrogen is also easy to find.  You can pick up a tank at a welding supply shop such as this one in North Carolina.

-Hydrogen is also very flammable and much more dangerous than helium.  Driving with a 200 cubic foot tank in the back seat is nerve wracking to say the least.  This may be a downside for the faint of heart.

-By overfilling our balloon we got a very fast ascent rate.  This cut down on our altitude (we made it to 79,000 ft, in contrast to 88,000 on Jake 2), but the upside is we didn’t lose our payload in the ocean.

-Got video and still images throughout the entire flight, but the payload was spinning very quickly.  The raw video makes one seasick and a lot of the stills are out of focus.  The edited video is the best I can do.  The spinning issue needs to be fixed in the future.

-The plastic parachute was too flimsy and tore apart during the descent, resulting in a pretty hard landing.  More on this later.

-The Arduino Uno and GPS shield recorded data through the entire flight.  Here’s an altitude versus time plot (see the raw data link above):

Ascent and descent of Jake 7.

Ascent and descent of Jake 7.

Equipment List:

a 600 gram weather balloon from Kaymont

a 200 cubic foot tank of hydrogen

one SPOT satellite tracker, so you know where the balloon went

one Arduino Uno flight computer with high altitude GPS data logger

two lunch boxes

tubing to move hydrogen from the tank to the balloon (1 inch inner diameter, if I recall right – measure the tank outlet)

plastic parachute (I will describe how I made it, but it failed! this is a “what not to do”)

Canon still camera, configured using CHDK to take pictures every 10 seconds

Kodak PlaySport video camera

zip ties

rubber bands

string

The Flight

I used a Python script I wrote to predict where the balloon would go based on the weather forecast.  Since we had a strong (~100 mph) jet stream, we found that there was a good chance of a water landing if the balloon ascended or descended slowly.  So we filled the balloon with a lot more gas than usual so it would rise quickly.

2013-03-30 10.17.31You can see two nice bright lunch boxes for the payload.  We had to use two because the SPOT GPS interferes with the Arduino GPS logger.  The launch site was near Saxapahaw, North Carolina.

After release, the payload swung back and forth violently.  Sometimes it was almost parallel to the ground.  This swinging motion was probably because the balloon was rising quickly through a fair amount of wind shear.  We watched the balloon disappear into a partly cloudy sky, and tracked it for about 20 minutes with the SPOT.  After that, it was above the SPOT maximum altitude, so we had to wait and hope it talked to us on the way down.

The black sky of near space.

The black sky of near space.

At high altitudes, the payload box spun rapidly.  This made for some nausea-inducing video!  The burst is audible, however, and the camera swings up briefly just after the pop.  You can see the expanding ball of plastic shreds in the YouTube video.  Pretty neat!

As the payload descended, the video camera swung upwards and pointed at the sky.  The still camera swung down and looked straight at the ground.  This is probably because the still camera was heavier, so the payload was off balance.

The still camera took excellent pictures until it went lens-first through a cloud.  All the pictures are foggy from then on.

Fourteen miles is a long way to fall!

Fourteen miles is a long way to fall!

The last photo before the cloud:

Moments before hitting the cloud.  The shadow of the payload is in the center of the halo.

Moments before hitting the cloud. The shadow of the payload is in the center of the halo.

The payload started falling at about 150 miles per hour.  As it descended, it encountered denser air and slowed to a fifth of its initial velocity.  I designed the parachute to slow everything down to 20 mph – but the thin plastic I used ripped during the descent, so the payload fell 10 mph faster than expected.  Everything survived just fine except for a crack in the Arduino case.  In addition, the lens cover no longer closes on the Canon camera.

We were very fortunate during the landing.  Had the balloon burst any later, the payload would have landed in a forest full of gigantic trees.  Instead, we found our lucky pink lunch boxes lying in a fallow cotton field in Selma, North Carolina –  about 50 feet from the forest margin.

Carrying the payload from the impact site.  The Canon is still taking pictures!

Carrying the payload from the impact site. The Canon is still taking pictures!

The moral of the story is: make a strong parachute.  I used the thinnest paint dropcloth I could find at Lowes (this material is what we use to make our giant solar balloons) to save on weight and also because I had it lying around already.  However, this plastic rips easily in the best of conditions.  Falling at 150 mph through thin, bitter cold air is certainly not a good place for it to be.  Next time, we’re going for the rip stop nylon parachute we used in our first weather balloon launch.

The take home message:

-Hydrogen is cheaper and lifts better.  We will be using it from now on, and thinking non-flammable thoughts as we do.

-Parachutes should not be made of plastic, and should be tested before deployment.  I think I will hold one out the window of the car at 20 or 30 mph.  If it can survive that, it will work (note that it falls 150 mph at 80,000 ft, but the air is thinner so the force is the same).

-A fast ascent seems to lead to bad image and video quality.  In any case, though, we need to think hard about how to make a stable camera platform.

We’ll leave you with a couple more cool plots – one showing ascent and descent rate, another showing the windspeed vs elevation, and a final one showing the flight track.  All of these plots were made using the data set included in this blog post.

The ascent and descent velocity.  The first jump is when we launched.  The switch to negative values is the descent.

The ascent and descent velocity. The first jump is when we launched. The switch to negative values is the descent.  Time should be in seconds, not hours.

This shows why you have to travel through the jet stream quickly if you want to avoid downwind locations.

This shows why you have to travel through the jet stream quickly if you are on the East Coast and the wind’s blowing east.

The balloon flew from the left to the right, starting at Saxapahaw and ending at Selma.  The gap is where the balloon burst.

The balloon flew from the left to the right, starting at Saxapahaw and ending at Selma. The balloon burst at the origin of the plot.