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.

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9 thoughts on “A Hydrogen-Filled Weather Balloon Flight into Near Space

  1. Hello, have you had any problems with the hydrogen escaping the balloon? I read somewhere that hydrogen’s small molecules passes through the latex. I want to use hydrogen for a lifting gas, but will it effect my end altitude? What if I add a little more than what I need so it escapes but will still lift farther…

    • I have not had a problem specifically. You always lose gas but it is not a big deal unless you just barely have enough to lift off in the first place. Then you can run into trouble. If you are worried just add a little extra. Having it pop a little early is better than never popping at all.

  2. A regulator that monitored pressure difference between the inside and outside of the balloon and released hydrogen will extend time at altitude. That seems like it would be an easy thing to build. At 16,200 m altitude air pressure is 10,000 Pa and we’re well below burst point. Start venting hydrogen at that altitude and reduce internal pressure from 160,000 Pa to 40,000 Pa at that altitude. You’d still be viable at 20,000 m (65,000 ft) – where air pressure is 5,475 Pa and your zero lift altitude would be below burst altitude. Then you’d be able to hover at that altitude for quite a while! To come down you’d merely vent all the hydrogen and use the deflated balloon as a drogue chute.

  3. NPP-301

    Surface Mount Pressure Sensor – NPP-301

    The NPP-301 Series features silicon pressure sensors in surface mount packages. An ultra-small Silicon Fusion Bonded (SFB), ultra-high stability SenStable® piezoresistive chip from NovaSensor is placed in a plastic package that exploits high volume, leadframe package technology to bring forth a low-cost sensor alternative to the OEM user.

    Low-cost surface mount package: SO-8
    Wide operating temperature range: -40°F to 257°F (–40°C to 125°C)
    Static accuracy <0.20% FSO maximum
    Suitable for automated component assembly
    Four element Wheatstone bridge configuration for circuit design flexibility
    Solid-state reliability
    100, 200 and 700 kPa absolute pressure ranges available

    So, the 200 kPa SO-8 package should be possible to integrate into a stopper at the bottom of the balloon, controlling a normally closed pizeoelectric microvalve that opens at 16,000 m and vents a portion of the hydrogen to extend lifetime by reducing peak altitude below burst altitude. Then, upon a pre-programmed time delay, vents the the hydrogen to recover the system in a controlled way.

    I said the balloon could operate as a drogue chute, but a partially filled balloon should provide a controlled descent as well! Providing also an aerodynamic form that may be guided with winglets attached to the instrumented base during descent.

    A glider with a 12:1 glide ratio falling from 30 km should be able to cover 360 km range!

    http://www.udomi.com/downloads/UserManualHydrostikv8.pdf

    Hydrostik – is a 90 gram package that stores 10 NL of hydrogen gas! Its not beyond the realm of possibility that during descent, more hydrogen might be added to slow the descent – or to maintain hydrogen for extended flights! (Circumnavigating the world?) Coming down precisely where it was launched. Or instead of venting, the hydrogen may be stored!

    http://www.gizmag.com/h-cell-20-miniature-hydrogen-fuel-cell/15223/

    Small fuel cells also raise the possibility of producing power for propulsion to assist in guidance or extend battery life.

  4. Dual Axis – Spin Stabilized Platform
    http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080034445.pdf

    Stabilized Rocket

    Gyrostabilized Platform

    Gyrostabilized Camera Platform

    The first reference gives governing equations. The second, shows how a rocket is stabilized with fins. The third shows how a platform is stabilized with gyros providing restoring forces. The fourth shows how to adjust camera position in response to changes in position. The systems operating together should give rock solid performance – whilst providing some measure of directional control during controlled descent.

  5. More camera stabilization hardware! Combined with gyrostabilized platform and fin stabilized air frame, you should be able to get a rock solid image! (and even do astronomy? like take a picture of the moon?)

  6. Hullo from Mauritius…

    Been wanting to do that for some time – but my small island is just 40 km across… seeing your graph with the 30 mile dispersion, I suppose it’s not even worth trying it here?

    I have a phantom 3 – I was thinking may be hook it up to a chute and then weather balloons and somehow take control of the descent and fly back home – Assuming there’s a way to prevent the chute wires from getting into the propellers….

    Lots of stuff to figure out… I certainly don’t want to risk my Phantom 3 pro….

    Your thoughts?

    • Mid latitude winds, like we have here in North Carolina, USA, tend to be a lot different (and stronger) than those in the tropics. Even here there are days where a flight would only go 10 or 20 km. So it’s definitely possible to do what you’re proposing, but you’ll just have to be very conservative as far as winds are concerned. Or, why not make your payload waterproof and buoyant, have it land in the ocean, and hire a fishing boat or whatever to go pick it up? The new SPOT trackers can run several weeks on their battery packs, or you could have some sort of radio beacon on it.

      • Hi,
        Thanks for the prompt reply…
        I actually have a small speedboat… but I just got my license so i wouldn’t risk that right now, but I reckon I could do something like that by the end of the year…

        in that case it will be without the phantom 3… that thing will be dead in water…

        Do you have a checklist of the things I could buy? How much they cost – are there ready made packages out there or smth?

        Thanks,

        Reuben

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