Sunday, March 23, 2008

SDG-9 update and European timeline

So far, I have only heard back from one individual in Newfoundland and, as noted in my previous entry, he did not hear the beacon. It seems we've come up with a twist to the old "tree falls" riddle: "If a beacon flies on a balloon and no one is around to hear it, does it make any sound?"

There are three distinct possibilities as to what has happened to SDG-9:

1. It had pinholes or other defects and subsequently lost gas, causing it to descend.

2. Radiative losses during the night cooled the gas sufficiently to offset the initial superpressure and decrease the balloon's volume, causing it to descend.

3. It is still flying.

The first alternative is certainly possible, but earlier SDG flights have demonstrated that our three-layer film is capable of holding gas under pressure for at least 32 hours (our previous flight record). It could have lost gas due to a mechanical defect, but I doubt it.

The second alternative is what most likely cut many of our earlier flights short. In particular, SDG-6, the 32 hour flight, almost certainly suffered from radiative losses and subsequent contraction of the gas (and loss of lift) when it descended the first night. I believe that we have corrected this problem, however, by almost doubling our initial superpressure compared to our earlier balloons (from 5% to 10%).

The third possibility - that it is still flying - is certainly my fondest hope and it is entirely likely. If so, then, save any possible listeners in Greenland (are there amateur radio ops in Greenland?), the next place where it might be heard is Iceland and, thereafter, Scotland.

Assuming that the balloon reached stable float at 9km, it should pass Iceland between 1800z today and 0000z on the 24th. It should then reach Scotland about four hours later, at 0400z on 24 March.

If stable float was indeed at 10km - which I doubt - then it will be a bit behind that schedule, nearing Iceland at 0400z on the 24th and Scotland several hours later.

The accompanying HYSPLIT projection (click it to see a larger image) shows trajectories for 8, 9 and 10km altitudes to battery exhaustion, about 96 hours after launch. Note that the 8km trajectory still leads to Europe, but quite a bit later. (Note the time scale along the bottom of the image.)

Please, if you can spare any time at all this Easter to monitor 29.499 Mhz for our CW signal, please do so! Without listeners, the balloon could easily fly over continental Europe and no one would even know! Note that the frequency tends to drop a bit after local sunset for the balloon, so keep this in mind when listening.

We gratefully acknowledge the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dispersion model and/or READY website ( used in the accompanying trajectory projection.

1 comment:

Anonymous said...

Hi, am currebtly listening 29.499 cw. east coast Ireland (20 west of Dublin) nothing heard but will monitor for a couple of days to see if anything pops up
73 de Rod ei7df