On the morning of Sat 7/26/2014, Lucas, Paul and Matthew(11) launched NSL-28. This was a test flight of some new gear and an investigation flight into some things we've noted previously.
600g balloon and ~90 cu ft H2
The venerable old "blue box" (9th flight)
Bigredbee 2M APRS transmitter + Spot Tracker
Test: AP510 APRS transceiver [working with developer on a high altitude model]
Video cameras: Mobius looking out. 808 #16 lens D looking down. 808 #16 lens D on top, sideways, and looking up at a 45deg angle.
RF remote tree descender rig
Matthew releasing the payload at launch. Sharron Harris steam plume geysering above the low clouds
We decided to launch early to beat the day's heat. The morning was foggy with two cloud layers below 3000 ft. We originally planned for a 4 m/s ascent, but at the last moment we chose to bump it up to 5 m/s. We expected the extra gas to lower our max altitude, but we were given a nice surprise of an additional 10k ft. It was a predictable flight and we made it to 104,088 feet.
We didn't get a chance to catch it at landing, but we were a few hundred yards away. Ray KC4VTX joined us at recovery.
The chase crew waiting during descent. A nice soft landing in a corn field next to the road. It doesn't get much easier than this.
Lucas tried an idea of leaving a large amount of the balloon's filler neck available to the balloon. That is, we tied off the balloon and secured the payload a good 3-4" below where we usually wire-tie the balloon. The intention is to give a few more cubic inches of expansion area.
The floppy antenna: Stills from video 15mins apart. Paul noticed that his simple APRS antenna was showing up in the view of many of his lower cameras, so he set up this view just to catch the antenna in the act. It's a simple steel wire with a black plastic coating. This happened between 25k-35k ft and the antenna regained its, um..., rigidity again on the way back down while passing through the same altitudes. So does it do this because of the cold of the troposphere, or the heat from the sun? Sounds like we need to play with some dry ice again and a heat lamp.
The RF remote tree descender rig was not needed for recovery, but we set it off in the car on the ride home and it cut the bridle as expected. The nichrome heating LiPo battery is finicky so we need to find a better power source.
We've mentioned that our Mobius/808 cameras give off a lot of heat. During this flight the internal payload temp measured by the AP510 only went as low as 90F. It got as hot as 116F before touchdown and then shot well above that while awaiting our recovery.
The AP510 Tracker with uBlox mod still needs some work. It worked really well up until about 38K ft, then it started acting strangely. We were ready for the possibility that the reported altitude could abruptly max out, but we then started seeing some really strange errors in Lat & Long as well. The unit then went completely silent for 40 minutes. Once the payload dropped back below 38K, it worked great again. We are working directly with the designer and we hope to try again soon with new firmware. This unit could become an inexpensive, feature-rich box for the HAB community. AND it speaks Bluetooth and is a TNC. Lots of cool project ideas come to mind.
APRS WIDE2-1 vs NONE: The Bee was set up with a single APRS path of WIDE2-1. This allows the big digipeaters to relay packets and helps out a lot at low altitudes (pre-flight testing and recovery), but at high altitudes you still run the increased risk of getting some late/duplicate packets injected into APRS -- from hundreds of miles away. These duplicates make it look like you are flying backwards at times.
We set the AP510 with a path of "NON" (sic) that so that digipeaters ignore the packets and it is just received by the few igates in the area. We were at 2400 feet in downtown Raleigh before the first packet reached an igate. Our last packet was 3700 feet on the way down. But there were no duplicate packets. We will test this again once we have the AP510 working at high altitude.
Reminder: Never use a path other than WIDE2-1 or NONE for HAB, or you will cause a packet storm. Also, we turn off 'smart beaconing' algorithms as they often get confused while swinging at the end of a long string.
Again during this flight, we were able to take advantage of having both the projected plot and the live plot both visible within Google Earth (remember to save your Habhub projections as a KML before flight). That's going to be key to being able to catch a payload someday. Also the live updating Excel spreadsheet let us keep an eye on live ascent/descent rates. We didn't see the drop in ascent rate before burst like we see on most flights, but it did start to show up on the on-board data (below) that was sampling every 10 sec.
Screenshot of live plotting of Predicted (yellow) and Actual (green) flights as well as the chase team (pink). The small deviation off of the projected path was partially due to our last minute decision to increase lift gas. We were able to predict the landing zone to within 2 miles just after burst.
Screenshot of live plotting Excel spreadsheet, the stray dots are duplicate APRS packets causing noise.
paul _at_ ncnearspace.org