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LOHAN avionics survive 27,700m stratospheric ordeal
Vulture 2 kit refuses to freeze during Edge Research Lab flight
It's beers all round today as we announce a successful final Low Orbit Helium Assisted Navigator (LOHAN) test flight, which saw our Vulture 2 spaceplane's avionics rig sent to 27,700m over Colorado and return to terra firma in fine fettle.
Our US allies at Edge Research Lab kindly volunteered to add our payload to their EDGE17 flight - primarily designed to test the "BEACON e-field sensor" as part of the stormchasing "Balloon Enabled Atmospheric Conditions Observation Network" project.
Our kit comprised Pixhawk autopilot and GPS unit, airspeed sensor (not shown below), full set of servos and the two packs of Energizer Ultimate Lithium AA batteries which power the whole shebang, via a Battery Eliminator Circuit (BEC) in the case of the servos.
Edge's David Patterson undertook to box the rig...
...and here it is ready to go...
...with the airspeed sensor visible here at the left:
Although this set-up works well enough on the ground, there were doubts as to whether the batteries could deliver enough grunt for an entire stratospheric flight in extreme cold. Furthermore, autopilot wranglers Linus Penzlien and Andrew Tridgell wanted to see how the servos and airspeed sensor performed in brass monkeys conditions.
For the purposes of the test, the Pixhawk was in "servo wiggle" mode - a custom LOHAN ArduPilot AUTO mode command (MAV_CMD_NAV_ASCEND_WAIT) which operates the servos every 15 seconds to prevent them freezing as the Vulture 2 ascends to launch altitude. (There's more on Linus and Tridge's Pixhawk brain surgery here.)
So, last Saturday morning, Edge members assembled to dispatch the packages stratowards, having cheekily dubbed our part of the mission "LESTER" (LOHAN Experiment: Stratospheric Test of Energy Reserves), in the spirit of previous ballocket tomfoolery backronyms.
David Patterson reported yesterday: "From an operations perspective, the team and I couldn't be happier with how things went. We were able to utilize a hanger at Colorado Springs East Airport for our fill and pre-flight prep, which enabled us to dial in the ascent rate that we wanted to ensure that the landing zone was conducive to an easy recovery.
"Springs East Airport provided us this space free of charge for this mission, and we certainly appreciate it - it made the fill and release much easier. As you can see from the video, the recovery was almost as easy as it could have been, with the ground team nearly catching the payloads as they descended."
The payloads hit 27,700m before balloon burst...
...and David reported that the servos were still operating after hitting the ground, indicating everything had gone according to plan.
Linus and Tridge have had a quick shufti at the Pixhawk logs, and confirmed all appears to be well at first glance, although they reported voltage spikes on the servo rail which may require the deployment of a zener diode.
We'll bring you a full report on the data next week, including loads of graphs like this demonstration of altitude and temperature, showing that while the external temperature dipped to -50°C, the inside of the payload box was a comparatively balmy 0°C:
Regarding Edge's BEACON e-field sensor, David said: "We're still analyzing the data from our BEACON payload, will keep you posted on the results (it's the intimidating looking black box with the spinning cylinders seen at various places in the video and shortly after burst)".
In summary, then, we're delighted with the results, and we invite readers to raise the traditional glass or two to the Edge team for their fantastic support. We will, of course, be raising a glass with them in person in due course, by which time we hope to have persuaded management that we too need our own pursuit aircraft... ®
More from the lovely LOHAN:
- You can find full LOHAN coverage right here.
- If you're new to LOHAN, seek out our mission summary for enlightenment.
- There are photos our our magnificent Vulture 2 spaceplane here, and detailed structural plans here.
- For your further viewing pleasure, we have all our photographic material stored on Flickr.
- Our LOHAN and Paper Aircraft Released Into Space (PARIS) videos live on YouTube.
- We sometimes indulge in light consensual tweeting, as you can see here.