BallastHalo 5 - Flight Success but now in the Sea!
James Coxon
Thank you all for helping out with the flight last night. While
BallastHalo 5 has landed in the sea we got a lot of good data from the
flight. Remember this payload has already visited France and the
Netherlands so its worked well beyond its mission length so we can see
this a seaside retirement.
After a very slow journey up to London we set about setting up our
'control centre' in Churchill and powered on the payload. The weather
was hot and the wind had just started to pick up - the payload managed
to get up to about 40deg internally while we waited for a GPS lock -
this was achieved by taking the payload outside. The rest of the setup
was simple and filling of the balloon didn't take long - because of
the wind it was a challenge to work out neutral buoyancy however a
combination of waiting for the wind to die down and running with the
balloon worked. Once we had filled correctly we attached the payload
string, walked out into the field at this point I found that the
ballast tank had leaked about 10mls however just made sure all the
tubing was attached correctly and then we launched. Visually the
launch the initial ascent rate was nice and slow and other stations
began to pick up the data at 300m or so. The payload weighed 1750g and
we added another 250g of free lift aiming for an ascent rate of
2-3m/s.
After hurrying back indoors and linking up to the yagi tracking seemed
to be working well being able to receive both the main payload and
also the hellschreiber easily. The ascent rate rose a bit up to 3.5m/s
then settled down to a nice 2.2m/s with the external and internal
temperatures remaining surprisingly warm up until quite high. The
balloon gradually rose with a very slow decrease in ascent rate to
around 1.8m/s though it didn't drop below the 1.5m/s threshold for a
small ballast drop (put in place to stop an underfilled flight going
on for ever, this was set up to only occur between 500 and 15000m).
The light sensor reported sunset ~ 1 hour after ground sunset and it
was at this point that the balloon began to float - like in
BallastHalo 2 there was an amazing rapid deceleration over about 5
minutes down to a stable neutral buoyancy. This was detected by the
flight computer and after 10 minutes started to dump ballast however
the pump rotation sensor (photogate) did not register the pump working
so while we were observing a rise in temperature (pump working) and
also a break in the float and rise in ascent rate the flight computer
didn't detect this and continued to pump ballast. Eventually the
sensor began to work and it detected enough rotations for it to decide
it had dumped enough - however by this time we would have dumped all
the ballast and we were rising up very rapidly. The float had been at
23km altitude so we had quite a large amount of altitude left to play
with and while we began to notice a decrease in ascent rate it was
still too fast and it reached its burst altitude and began to descend.
As this point the flight computer recognised this and did an emergency
ballast drop (though the tank was empty and it wouldn't have helped!).
Unfortunately for BallastHalo 5 to have avoided the sea it would have
needed to float for about 2 hours, as we only floated for 19 minutes
it was still quite far out to sea and splashed down.
We had some great tracking yesterday evening - the room we use in
Churchill has excellent west and east views but terrible Northern
views so we struggled to get data however the dl-fldigi/tracker system
excelled with G4FEV rx'ing 901 strings, G3VZV 687 strings and M6LEP
644 strings. Lots of other people contributed and if you managed to rx
a string and submit it pleased send me your postal address in a
separate email and I will send out a Pegasus HAB Project QSL card.
Also an enormous thank you to Alexei (natrium) and Rob (M0RJX) who did
some rapid hacking to overcome my time stamp issue and tracked down
the rogue data. Please not that there is no chase boat - it is just
Alexei messing around!
Now on to the good things and the bad things. With a slow ascent rate
launched to coincide with an altitude sunset at 20km altitude or so
with a small vent in the balloon it will float - we replicated this
with both BH2 and BH5 - this is something to explore as its a very
interesting phenomenon - I'd like to launch a flight with out ballast
just to see how far we could float it - something for the future.
BallastHalo 5 was able to detect this float and triggered a ballast
drop - the pump did seem to work with the noticeable rise in ascent
rate and temperature even if the sensor failed. It therefore seems
that a peristaltic pump is a good choice for ballast dumps. The sensor
was strange, at first it didn't work (-27C) and then as the payload
warmed up a little it began to work more(-22C) and then it worked
properly(-19C) which would suggest something to do with temperature. A
number of theories have been suggested including temperature related
threshold or my construction techniques, this certainly needs some
testing. Because we dumped all our ballast at once we didn't get
enough float to make it back to land, this could have been avoided if
the code had stopped the ballast drop once the ascent rate increased -
again an oversight by me!
Overall it was a really fun launch - the community really helped out
with the tracking, the listener system is a lot of fun and with
flights like these its great that people interpret the data as it
comes in. Finally a big thank you for Ed Moore and Steve Randall for
the help with the flight preparation and launch.
Sure if it hadn't dumped all its ballast then it would have flown all
night but then it would have probably landed in the Irish sea - this
payload did great things, now its floating in the North Sea - with the
remnants of a bottle of ethanol - its probably having a great time!
Thank you again to everyone who helped out.
Pictures of the launch and payload can be found on flickr:
http://www.flickr.com/photos/tags/ballasthalo5/
Launch video: http://www.youtube.com/watch?v=TzsMS7RvChg
Technical Info:
http://www.pegasushabproject.org.uk/wiki/doku.php/missions:ballasthalo:ballasthalo5
Thanks
James
M6JCX
http://www.pegasushabproject.org.uk
p.s Any one decode any hellschreiber?