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Re: [Balloon_Sked] achived height vs balloon type and filling

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  • Mike Manes
    Hello Thomas, HEre s a link to all of EOSS s balloon-related software: http://www.eoss.org/balsoft.htm LiftWin is quite handy for computing a fill for a
    Message 1 of 2 , Nov 26, 2008
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      Hello Thomas,

      HEre's a link to all of EOSS's balloon-related software:

      http://www.eoss.org/balsoft.htm

      LiftWin is quite handy for computing a fill for a variety of balloons
      based on the weight suspended from the balloon neck. Both He and H2
      are supported. As a rule of thumb, one should aim for about 1000 ft/min
      ascent rate to avoid stalling when flow separation occurs at high
      altitude.

      A latex balloon can "stall" either due to an inadequate fill, cooling
      after sunset or a gas leak. It's an excellent idea to include a
      commandable release device to bring the payload string down before
      it soars out of sight and its batteries die.

      It's also possible to get a substandard fill if there is over about
      10 kt wind over the balloon during the fill; this creates "false
      lift" due to the top of the balloon acting like an airfoil. Best
      plan is to avoid filling under such conditions; winds are typically
      calmest shortly after sunrise.

      And yes, the long-duration fligths typically use "zero-pressure" plastic
      balloons which have vents at the bottom. But it's also possible to
      cause a latex balloon to float at some desired altitude by controlling a
      dump valve in the neck. Another scheme is the super-pressure balloon
      which has a fixed, sealed volume - but it must withstand the excessive
      pressure of the fill gas during the day.

      73 de Mike W5VSI

      Thomas Scherrer wrote:
      > can you direct me to calculators ?
      > and or tables where I can see the most common ways how to predict or
      > calculate the peak altitude.
      >
      > it is clear to me that a lighter weight payload will go highter,
      > and the balloon needs to be as light weight as possible,
      > and also be able to expand so it dont burst too erly.
      >
      > is it possible to fill a balloon in such an unlucky way that it with
      > its payload, can stabilce at 10k ft or something like that, and just
      > stays there until the gas run out ?
      >
      > the idea is to make it continue until it bursts and then return with
      > parachute, but if the filled gas is too little, I guess it can not
      > burst it, or if the payload is too big for the selected balloon and
      > fill level.
      >
      > I guess long durations flights are made not using weather ballongs ??
      > but some other large light weight plastic with also vents mounted to
      > prevent bursting, and keep it longer lasting.
      >
      > -Thomas Scherrer OZ2CPU - www.webx.dk/bal
      >
      >
      > ------------------------------------
      >
      > Yahoo! Groups Links
      >
      >
      >
      >

      --
      Mike Manes mrmanes@... Tel: 303-979-4899
      "Things should be made as simple as possible, but not more so."
      A. Einstein
    • Mike Manes
      Hi Thomas, Apologies on behalf of us Yanks for desperately clinging to the English system, ironically abandoned long ago by the Brits. I expect that sometime
      Message 2 of 2 , Nov 27, 2008
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        Hi Thomas,

        Apologies on behalf of us Yanks for desperately clinging to the English
        system, ironically abandoned long ago by the Brits. I expect that sometime
        in this millenium, we'll join the rest of the civilized world in fully
        adopting the metric system, perhaps even before the only other hanger-on,
        Liberia!

        By "stalling", I mean a significant loss of ascent rate to the extent that
        burst and descent may be delayed until the flight is much farther downrange
        than planned.

        I pointed out the most effective measures to avoid stalling, but I must
        emphasize the importance of carrying a commandable cutdown device if all
        else fails. This device has been used even on otherwise normal flight to
        avoid landing in an unaccessible area. The EOSS cutdown device also
        incorporates a DF beacon - it transmits a DF signal for 30 sec every
        minute, and listens for a DTMF cutdown command for the remaining 30
        sec. The DF beacon has paid for itself many times where the APRS beacon
        has failed - most recently on our last flight.

        IF you have run LiftWin, you may have noticed that for a given balloon and
        payload weight, one may fill for a range of ascent rates. A more generous
        fill will yield a faster ascent rate due to greater lift, and will result
        in burst at a lower altitude due to the greater volume of fill gas; the
        envelope will burst at a fairly predictable expanded maximum diameter.

        EOSS has achieved its 100% recovery rate largely because we deploy the
        tracking and recovery teams out to the vicinity of predicted landing before
        we even start the fill. This has allowed the teams to witness the descent
        and landing on nearly all flight in recent years. During the summer, the
        upper winds are easterly, which causes the balloon to return towards the
        launch site, sometimes even passing directly overhead. On those flights,
        the trackers typically will deploy from the launch site after assisting the
        launch team. Winter flights, however, can be expected to travel at least
        100 km downrange.

        I'm not aware of any amateur balloon group who have successfully flown a
        latex release valve, but a company in New Mexico, US, Space Data, uses that
        method to float mobile phone cell sites in the stratosphere for up to 3 days.

        Both latex and plastic balloon envelopes must be as light as possible, and
        thus rarely survive a flight and landing intact. And latex deteriorates
        rapidly in solar UV radiation - and often to the extent that a lightly-filled
        and slow-ascending balloon may burst at a lower altitude than a faster one,
        contrary to the assumption of a fixed burst diameter noted above.
        Accordingly, re-use of balloons is hardly worth a second thought.

        In the US, Kaymont Inc in New York distributes the Japanese Kaysam line of
        latex balloons. A 1200 gm balloon, suitable for flights under 5 kg, costs
        about US$65.00 plus shipping. You might check with some of the other EU
        balloon groups listed on Ralph Wallio's web site for their sources. Beware
        of bargain basement latex balloons which may not have been stored properly
        or have exceeded their expiry date. They may have deteriorated to the
        extent that they won't survive a fill, or may burst much earlier than
        expected. But there are some valid bargains out there. Caveat emtor.

        I've cc'd this to the GPSL reflector, which has become the ad hoc forum for
        technical issues related to ARHAB.

        73 de Mike W5VSI
        CTO EOSS


        Thomas Scherrer wrote:
        > Hi mike, thanks for getting back to me,
        >
        >> HEre's a link to all of EOSS's balloon-related software:
        >> http://www.eoss.org/balsoft.htm
        >
        > super thanks !
        >
        >> LiftWin is quite handy for computing a fill for a variety of balloons
        >> based on the weight suspended from the balloon neck.
        >
        > great, I am just a bit sad about it dont handle metric mode :-)
        >
        >> Both He and H2
        >> are supported. As a rule of thumb, one should aim for about 1000 ft/min
        >> ascent rate to avoid stalling when flow separation occurs at high
        >> altitude.
        >
        > aha ok, stalling, you mean stabelicing at a height under the burst height
        > so I get a problem ?!
        >
        >
        >> A latex balloon can "stall" either due to an inadequate fill, cooling
        >> after sunset or a gas leak. It's an excellent idea to include a
        >> commandable release device to bring the payload string down before
        >> it soars out of sight and its batteries die.
        >
        > exactly what I am affraight of, first of all I need to understand all
        > fundamentals into full datail,
        > to first prevent getting any issues, and then also add safety devices,
        > a commandable feature will need a two way radio, and add more weight,
        >
        > something I dont understand, using the LiftWin:
        > changing a payload weight I dont see the peak height change soo much ?!?!
        > that is wierd to me..
        > it is clear the time to get up goes much slower when the payload gets bigger,
        > but I would expect a much heavier payload to go much lower,
        > that is not the fact with that program.
        >
        >> It's also possible to get a substandard fill if there is over about
        >> 10 kt wind over the balloon during the fill; this creates "false
        >> lift" due to the top of the balloon acting like an airfoil. Best
        >> plan is to avoid filling under such conditions; winds are typically
        >> calmest shortly after sunrise.
        >
        > yes I see, I expect to perform my flight an erly morning with as low
        > wind ad possible
        > so I get long time to find it again, and also make my car hunt for it,
        > as short as possible.
        >
        >> And yes, the long-duration fligths typically use "zero-pressure" plastic
        >> balloons which have vents at the bottom. But it's also possible to
        >> cause a latex balloon to float at some desired altitude by controlling a
        >> dump valve in the neck. Another scheme is the super-pressure balloon
        >> which has a fixed, sealed volume - but it must withstand the excessive
        >> pressure of the fill gas during the day.
        >
        > have anyone tried to mount a pressure sensor inside a weather balloon ?
        > and an electronic controlled valve to let the gas out again?
        > with this added bursting can be avoided,
        > and it can even be commanded down again, and even reused ?
        > and then you can save the parachute, is this a bad idea ?
        > I think the large balloons are quite expensive so reusing them seems
        > like a cool idea, or not ?
        >
        > have you any idea where I get the 800gr to 1200gr large size weather
        > balloons cheap ?
        >
        > (maybe we should copy some of this into the balloon skeed forum as well ?
        > might help others too)
        >

        --
        Mike Manes mrmanes@... Tel: 303-979-4899
        "Things should be made as simple as possible, but not more so."
        A. Einstein
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