Apollo67

Sunday Nov. 20, 2011, was launch day. We arrived at 7am to make preparations. We checked the weather conditions, re-ran the trajectory prediction calculator, and assembled materials, checking them off of the list as we put them in the car. The hydrogen tank fit snugly in the trunk of the car, and though we looked, we didn’t find regulations regarding the display of hazmat signs for transporting the tank.

A few more modifications to the envelope were made. Namely, addition of a pair of fins painted bright orange, and various signage, including names and phone numbers of responsible parties and this website.

Everything packed into the car. Hydrogen, tarp, and box of materials. The alligator rode in the back seat.

After packing everything into the car, three of us took a ride out to Ridgeway, which had been carefully researched as the best launch site because it was far enough West that the payload should drop before landing in Lake Michigan, but still far enough East that it was still within cell reception, and far from an airport and other tall structures.

We arrived at the site without incident, and it was better than we expected. It was unpopulated, but sported a nice parking lot, with only a single light pole acting as an obstruction, but it was upwind. Downwind was a small valley and fields. It was ideal, except for the wind and temperature. We hastily set out the tarp and materials, and borrowed wood logs to hold the tarp down. Then we assembled the tether and attached streamers to it to increase visibility and act as drag. We set up the regulator and hose, prepared the balloon, and inflated it.

Looking out over the launch site. Notice the wind blowing in that direction, where there are no vertical obstructions at all.

One person wearing latex gloves held the balloon steady as it inflated. The wind made this difficult, and the wind and cold made it painful. When it was ready, the phone was retrieved from the car, where it had been staying charged and warm, and inserted into the envelope and taped closed. Then a text message was sent to the phone, starting the timing, and once it had count down, we released the balloon, then immediately after the payload.

The balloon rose quickly and smoothly up. It wasn’t long before it was up into the clouds and gone. We hurriedly packed everything back in the car, warmed up, sent messages to the other team members, and then fired up our electronics for tracking.

Preparing for launch.

Immediately after we started tracking, we noticed that the app had successfully sent two messages about its whereabouts, so we were confident the app was running successfully. We sent a text message to start instamapper and headed back East. We had originally intended to skip Madison and head directly to the projected landing site, but the realization that we had a tank of hydrogen still in the trunk motivated us to stop back at Sector67.

The only data we captured from the phone:

Another car had gone East as soon as we launched so that they could be closer when the balloon landed. After dropping the tank off, changing cars, and taking on a fourth member in ours, we headed East as well.

At the point where we should have heard from the phone excitement turned to nervousness. No news on any of the three tracking methods. The time came and went, and we continued to perform calculations and come up with reasons for why we hadn’t heard from the phone and the ramifications of not having heard from it yet. Eventually we tried calling it to see if the phone was even in cell range, but it went straight to voice mail. We stopped just outside Milwaukee to eat lunch and continue to wait.

During lunch the other car met up with the first car and we discussed possibilities and next steps. Then we went back to Sector67 and got rest after our long night of work.

On Friday the 18th we met to work on the project. Saturday night we continued our preparations, working late into the night and early into the morning on the design, the software, and the logistics.

Unfortunately, the foam we had originally ordered never showed up. To compound matters, the backup foam we ordered didn’t arrive in time, either. Thanks to Micah, who toured a nearby foam distributor in exchange for a small piece of similar foam, we had a backup piece of foam, but we had to scramble to learn how to use it and get it to adhere. It’s considerably different from the material we used for the cold test, so there’s some concern about its insulating abilities.

After discovering that copious amounts of hot glue in addition to two bolts and sewing would be able to keep the pieces of foam together, we tested the foam’s impact absorption capabilities. We had a hard time with calculations. Our resources and calculations were telling us we needed 2 meters of foam to protect the phone, but logic was telling us that was impossible. Finally we broke down and just started trying it out, first by dropping the thing with the phone inside, then by throwing it, and finally by beating it against the concrete. In all cases the phone performed like a champ, so we were reasonably certain that falling from altitude would not harm the phone.

We spent a significant amount of time on logistics as well. The timing of the competition was less than ideal; with winter fast approaching, the number of acceptable launch days was low, and conditions were not good even on those days. When we decided to launch on Sunday, it was because it was only forecast to be mostly cloudy instead of precipitating. Using the calculator available from habhub, and the ATT coverage tool, we discovered that we would have to travel West to make sure the phone wouldn’t land in the lake, but too far West and we would be completely out of cell range. We settled on a town called Ridgeway, which was just off a highway, not near an airport, at the edge of reception, and had a perfect launch location that was easy to get to, on top of a hill, and had no dangerous tall objects nearby. As for launch time, we wanted to do it early in the morning so that we would have more time to search, and late enough so that we would have enough light for photos.

Design of the app went well, too. Despite a near catastrophic moment that involved the difference between meters and feet, the app came together at the last minute, and even reported data back to a web service on this site while it had signal. In testing it ran for a few hours without issue and successfully made it through the transitions between stages of flight. Just in case it didn’t work, though, we also installed instamapper and wheresmydroid; two applications that could be used to help us get the phone back.

We got a few hours of sleep, then got started on launch day.

Final preparations are underway. Hopefully we will launch in just a few hours. The team is assembling right now to drive West to Ridgeway, which was selected because of an ideal launch site, just on the edge of reception, and far enough that the predictions don’t have the balloon landing in Lake Michigan. If all goes well we will launch at around 10am, ascend for 1 hour, pop near Watertown, and land near Germantown. Of course, we may overfill or underfill the balloon, poorly estimate the weight, or experience different weather than expected. Today’s going to be interesting.

We almost had a NASA moment. The programmer recorded all the altitudes for the different stages of the flight in meters, but thought it was feet. Instead of an altitude of 50000 feet, he was setting it to be 50000 meters, which would have been higher than a balloon can go. Thankfully we caught the problem and were able to fix it, but it’s a very good reminder to communicate your units. Ideally everything should be done in one system (preferably metric), but the reality is that the units between suppliers and systems vary and it’s not always possible to standardize. It’s definitely worth it to be clear, though.

Friday the 11th we performed an experiment with hydrogen to verify that it is possible to handle safely, and that even if it does explode there is relatively little danger.

In this experiment we took small latex balloons and filled them outside with hydrogen. We had a short pipe extending from the regulator attached to the hydrogen tank. We first blew some hydrogen through the pipe to make sure there was no air in it. Then we attached the completely deflated balloon and slowly filled it up. Then we tied a knot in the inflated balloon and tied a weighted string to it. After that, we brought it inside.

We filled the balloon outside because we didn’t want any hydrogen leaking out and potentially accumulating on the ceiling, where it would just stick around as a pocket of mixed flammable gas, which is dangerous.

We also made sure to make the balloon filled completely with hydrogen and no other gases. This is important, as a mixture of air with the hydrogen would facilitate a much faster reaction; a real explosion.

After bringing the filled and sealed balloon inside, we set it down, focused a very bright spotlight on it (the high speed camera requires a lot of light), started the high speed camera, and then touched the balloon with a kerosene-soaked rag on a pole.  This ignited the hydrogen, which burned rapidly. Here’s the first video:

As you can see, there’s a very rapid fire, but the noise is just as loud as a regular balloon, and though we are standing only a few feet away there is no large blast and we only barely felt the heat. We performed the same test a second time with a different framerate and a person in the shot for perspective and context:

There are some important notes from these tests.

1. Hydrogen is VERY flammable, but it can be safely handled.
2. The reaction with hydrogen involves heat, hydrogen, and oxygen. Without all three, it’s very boring.
3. The hydrogen balloon alone is very easy to handle and if it pops the hydrogen will mix into the atmosphere quickly and rise, so it should be done outside, but nothing bad will happen if you handle hydrogen outside without any sources of spark or flame nearby.
4. Even a spark needs to be extremely close to the hydrogen and spark across both hydrogen and oxygen to start the reaction. A flame or spark a few feet away will not cause an explosion, but don’t press your luck.
5. Finally, with a pure hydrogen balloon, if there is a heat source, then the fire will consume the hydrogen from the outside in as the air mixes with the hydrogen. It’s a fast fireball, not an explosion outwards. That’s why we were so comfortable being close to the balloon.
6. BIG IMPORTANT NOTE: Do NOT mix hydrogen with air and then ignite it. That will cause an extremely rapid reaction as all the hydrogen reacts with the oxygen at once and you get an explosion. A pure hydrogen balloon is MUCH safer than one mixed with air. Better yet, just don’t ignite it. We did the experiment so you don’t have to.
7. BIGGER IMPORTANT NOTE: We do NOT assume responsibility or liability for anything you do based on what you’ve read on this site or in any communication with us. While we believe our advice is sound and we have taken precautions to protect ourselves (we didn’t show the tests outside in the dark, we didn’t show the fire extinguisher nearby, and all the other small tests we did to get comfortable enough to make those videos), we don’t know how you will decide to do something stupid and hurt yourself. Hydrogen CAN be very dangerous if not handled properly.

One final bit. We did this experiment because we know a lot of people have some gut reactions to the thought of using hydrogen to fill a balloon around children. We wanted to show that it won’t cause an explosion if done right, and there shouldn’t be any reason for this to go wrong. Even if it did, it probably wouldn’t be a big deal as these videos show. Still, Murphy lurks around every corner, so we strongly recommend that kids stay at a respectable distance during the filling until the balloon is launched, and that you choose a place to fill and launch that is not near any sources of flame or sparks or power lines.  Hydrogen is a reasonable and cheap gas to use for this project and we hope these videos convince you that it can be done in the presence of youngsters.

We performed a cold test to see if the foam cage with a window could protect a phone in -60C weather for 2 hours. This was to make sure that everything would work at altitude. Things got a little frosty, but still worked. See the full writeup on the cold test here.

The group has started. We’ve had an initial and planning meeting, we know who’s working on what, and we have a plan. This is going to be the best balloon launch ever!