Night Flight Round Up

It sounds like quite a few “watched” our flight live on so many of you know some of the story. We only achieved a maximum altitude of 10,352 feet through a 3 hour flight. The flight became a valuable lesson on neutral buoyancy. On to the good news. Our goals were to:

  • Perform a successful open field launch. Check!
  • Run a series of cameras hacked to shoot astronomical images. Check!
  • Capture images of the conjunction of Venus, Jupiter and the Moon. Check!
  • Do a night flight with a successful recovery. Check!

Jupiter and the Crescent Moon over Illinois from 8,000 feet

We launched on time at 7:04pm from a site in West Aurora with the help of Chas, Mrs. Chas, Arpan and his parents, Rebecca and Mike. Moments after the release we realized things were not going according to plan. We’ve seen a lot of ascents and knew this was way slower than our usual 350meters/min goal. For a time, we thought that the balloon achieved neutral buoyancy at an altitude near 600 meters. As the sun set, the balloon rose slowly. This was probably due to the fact that as the atmosphere cools it becomes more dense. This would mean the density of the helium in the balloon would rise to find a natural level of balance. We were worried that if the condition did not change, our payload could float for hours or even days. Why it began to slowly descend after 2 hours is a different question. Eventually, our payload returned to Earth southwest of Joliet in Channahon, IL just shy of the Des Plaines river. Whew! The payload was visible mere yards from the side of the road in an open field thanks to the flashing lights mounted along the frame.

The stabilized payload frame had five cameras mounted to it. There were four still cameras set to shoot once every 8 seconds and a GoPro video camera. I’m happy to report all the cameras did their job. They were all still operating on recovery. We captured over 3000 images and more than 3 hours of video. We’ll need to process the images but for now I’m posting a relatively unprocessed snapshot from the flight. I’ll put up some selected video and more images as soon as possible.

The challenge now is how to determine lift in an open field launch. While doing the balloon fill we held the balloon down with cloth draped over the balloon to contain it from the effects of the wind. It worked well yet it doesn’t allow checking the lift by our usual method of using an inverted fish scale. Geza has suggested designing a flow meter attachment to the fill tube so we can calculate lift via absolute amount of helium pumped into the balloon.

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  1. Chas

    Whew! When I saw that the last location from the trackers was right! on a 130KV powerline, I feared the worst!

    Chas. and Barbara

  2. Chas

    Additional: Was the balloon still attached and intact when it grounded, and how far from the power lines was it? Is somebody going to edit the Go Pro video?

    1. kwalczak

      I’ll post a short “best of” video soon – probably later this evening.

      If you or anyone else is interested, Geza says he has a flow meter we can try out. He said it is not calibrated for helium yet it should be able to give us a relative quantity from which we should be able to correlate lift.

      Ah yes, Barbara… Pardon that.

      1. Chas

        RE Barbara, It’s OK — you had other things on your mind. Thanx for the shoutout.

  3. spencer

    Still a fantastic image!

    Why not use a pressure gauge? We know that the full capacity of a K cylinder should be 217 cubic feet, and if it’s delivered at 4500 psi (which I think is the standard), then you should be able to do a pretty simple pressure ratio to figure out the amount of helium released.

    That’s assuming you don’t get your hands on a flow meter.

    1. Spencer

      One issue I see already — the pressure will drop with the temperature as the tank is decompressed.


  4. mhammergren

    I agree with Spencer. We should be able to use the starting and ending tank pressure to calculate how much helium we put in the balloon. (In practice, we’d make the calculation before filling, to know when to stop). This method won’t require any new hardware, and we can test it at the next few launches.

    1. spencer

      I suppose one way to reduce the impacts of pressure change would be to do the calculations beforehand for an adiabatic decompression, and then wrap the tank in some kind of insulation.

      Then again, I’m not sure how much heat is stored in the metal of the tank, compared to how much is used in the expansion of the gas. If it’s a lot (which is probably is), that model is shot. since it would probably conduct in pretty quickly. Maybe we could assume the temperature of the gas restores back to room temperature after a few minutes?

      1. spencer

        Correction: tempeature* change.

        1. spencer


          Hey Ken, where’s the edit button?

          1. kwalczak

            In your mind ;-)

            I think you’re over thinking this. If we’re looking for a lift calculation with an error of +-10grams, we probably would need to take into account the temperature/pressure relationship. To get within the error bars as the NWS suggest (re: NWS Radiosonde and Sounding Procedures) ballpark pressure from the regulator or a flow meter will probably do the trick.

            Update: I corrected the link to go directly to the NWS pdf

  5. mhammergren

    The path of the descent on this mission was a real nail biter! The ending was highly charged with suspense, literally buzzing with excitement — a real high tension situation!

  6. Chas

    What i’d like to try: Capture the balloon in another parachute, that being a piece of smooth fabric, shaped correctly, with lines at the corners. Rig a system that brings the lines to a single point, where they are attached to our annoying fish scale or equivalent. Tension in all 4 lines equals lift. Pop (Ow–bad choice of words) two lines and up goes the flight. Sketch to follow.

    1. gezagyuk

      But wouldn’t that suffer from the same problem of getting uncertain values of the total lift when we are filling outdoors and there is wind tugging the balloon around? But it might make handling the balloon easier otherwise.

      1. Chas

        Yeah, Geza, but I’m thinking* that averaging the load on all 4 lines would damp that effect out. The advantage is we get a direct readout of the actual lift. (“This is how deep it is, General”)

        I also wondered about a simple windbreak of a tarp on vertical posts upwind — but that’s only going to work in moderate breezes, any substantial wind is going to blow it over and kill us all.

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