Nov 16 2010
I got up rather earlier than usual last Saturday morning (0600 EST5EDT) to get ready for another Spaceblimp launch by HacDC, this time from a location in semi-rural Maryland. I had just enough time to get Windbringer prepped, my doctor's bag packed, and the rest of the stuff I wanted to keep close by into my backpack when I got a phone call from Bjorn in the parking lot outside my apartment building, who would be driving the chase car this time around. We met up with Nick (who rode shotgun in the TARDIS last time) and then struck out for the launch site. We found out the hard way, however, that the map coordinates of the launch site that were posted to the mailing list were incorrect and we wound up in the parking lot of someone's soccer practice fifteen miles off course. We weren't the only ones to wind up in the wrong location, thankfully, so the impact of the delay was distributed across a number of people. Thankfully we still have cell connectivity out there, and thus were able to get the correct location with only a phone call and a quick trip down the highway.
Due to the fact that the Hackerspaces In Space competition is over we were less constrained with regard to how much money we could spend on a given balloon as well as how much we could pack into the chassis (up to the 4 kg limit, anyway). Thus, the doors were thrown open and anyone who wanted to send a module aloft during the launch could do so. Spaceblimp-3 sported a complement of two transmitters, three cameras (two still cams programmed to take pictures every few seconds and a high definition video camera), a geiger counter to assay alpha and beta radiation, an altimeter, and a couple of temperature sensors to monitor conditions inside and outside of the insulated capsule. Most every sensor on board had an independent power supply, mostly to keep the wiring simple but it also made it possible for everyone to work independently to get things done. This time the Spaceblimp had two transmitters operating on different frequencies, the idea being that the first would log Spaceblimp-3's position on aprs.fi and the second would function as a backup for the chase team; on top of that a synthesized voice would report the instrument package's position every so often as the instrument package got closer to the ground. We also had someone posting updates to a Twitter feed so people could chase the balloon vicariously.
The process of filling the weather balloon went about as well as one would expect; the launch team built a pressure regulator and feedline attachment that would mate with standard gas canisters in the summer of 2010 to prepare for the competition. There were three industrial-sized tanks of helium on site, two of which were partially drained from the first two launches. Those two were polished off and we started on the third during the inflation process. I was too busy holding the balloon down (along with six or seven other people) so I didn't pay attention to much else. I was too busy trying to keep the balloon from taking off prematurely or getting popped by something on my person. After the parachute and instrument package were fitted to the balloon, it was noted by several that the balloon went up a bit more jerkily than intended. It wasn't as smooth a launch as some of us had hoped, and this may have had something to do with some of the equipment failures that cropped up during the launch. We stood back and watched it rise out of sight into the oddly calm skies and then assembled our equipment in the chase vehicles: shortwave radios, cellphones, GPS navigation systems, and laptops were unlimbered, plugged in, stuck on, tied down and booted up. Thus, getting into the chase cars and setting off in persuit of Spaceblimp-3 involved tying ourselves down with all of the cables running across the seats as much it did buckling out seatbelts and making sure that no cables got slammed in the doors.
To keep in touch with one another the chase cars in the caravan were all equipped with shortwave radios tuned to the same frequency as well as transceivers to monitor the dasta feed from Spaceblimp-3. As it turned out, even with external antennas attached to the roofs of some cars the backup FRS/GMRS radios worked better then the shortwave transceivers for keeping a radio net in between the chase cars. At one point we ran into someone on the channel we were using by accident, but after politely explaining what we were doing the individual on the other end changed to a different frequency. For our part, Nick sat in the back monitoring the APRS feeds from Spaceblimp-3, Bjorn drove, and I jockeyed the radios and GPS navigation system from the passenger's seat. Our basic plan involved heading for the coordinates of the projected landing zone, determined from a simulation made a couple of hours prior with the most up to date weather data we had from the NOAA. About half an hour into the trip we stopped off for petrol and to talk with the members of another chase car for a bit to make sure everyone was on the same page. Tracking and recovering the instrument package of Spaceblimp-3 largely involved plugging the coordinates for the projected LZ into my GPS, changing course if another location seemed more likely, and closing in on the instrument package the closer it got to the ground.
Of course it's never as straightforward as it sounds. There was an unforseen problem in the primary GPS tracker which stopped it fromm transmitting for reasons I'm unclear on (hey Nick, want to chime in with a comment?). Long story short, we were only able to pick up APRS packets from Spaceblimp-3 on the UHF band; those of us with ham equipment incapable of operating on the UHF bands were unable to maintain contact. There was also a point at which the GPS stopped broadcasting its coordinates; this is actually to be expected due to the limitations of civilian GPS in the United States. Nick's hypothesis was that we'd begin to pick up the probe's coordinates normally after the weather balloon burst and the instrument package fell below 40,000 feet (I think due to a quirk of the backup receiver). As luck would have it, his hypothesis was proven correct shortly thereafter. Bjorn, Nick, and I were within spitting distance of the probe when it landed in a farmer's field somewhere in rural Maryland. We drove past it, turned around, and spotted a familiar white box and crumpled blue parachute laying on the other side of a barbed wire fence in someone's field.
Bjorn pulled over to the side of the road and we dove out of the truck and sprinted across the field to examine the probe. Aside from a few minor dents and dings the instrument package was unharmed. The j-pole antenna was intact (a problem in earlier iterations of the Spaceblimp), the parachute's shroud lines hadn't tangled, and even the corners hadn't been crushed by the landing. I think it was Nick who put the word out that we'd recovered the instrument package. Shortly after we checked out the probe the other chase vehicles converged on our location. It would seem that fifteen hackers crouching in the middle of someone's field dismantling an object laying on the ground must have been quite a sight because passing cars began to slow down to gawk at us and the owner of the farm, an older gentleman, drove up on a tractor to inquire about the reasons for our trespassing. We explained to him that we had launched a weather balloon earlier that day and were verifying that it had gathered information, and oh, by the way, would you like to look at the pictures it took?
The farmer whose land we were trespassing on was most interested to see the results of our efforts. Laptops were procured, SDcards ejected, and beautiful images of the Earth's atmosphere and horizon were shown around. Unfortunately, in the process of dismantling Spaceblimp-3 to get at the data storage we discovered that a couple of problems had cropped up during the flight. As I'd mentioned earlier the GPS which would be broadcasting information over the APRS network had only transmitted the coordinates of the launch site. When Nick, Bjorn, and I were closing in on the instrument package we were picking up signals from the probe's transmitter directly and not through the APRS network. Secondly, the HD video camera cut out while the probe was still on the ground, so we got about three minutes of people's knees and miscellaneous background noise before it shut off. The geiger counter's power supply was bad so we got nothing from that (no entropy from high altitude, oh well). It was determined from the altimeter that the instrument package reached a maximum altitude of 75,262 feet before the weather balloon popped.
After packing everything up, giving the farmer a couple of HacDC stickers, and bundling ourselves back into cars we caravanned to a tiny Italian restaurant in the next town over for dinner. By 'tiny' I mean that the chase team descended upon them like a plague of locusts and wound up taking over much of the restaurant. Laptops were running on tables next to garlic bread and cups of coffee, and we talked about various and sundry matters until people began to head for home in groups of two or three. Unfortunately they'd only had one cook in the kitchen last night so service was extremely slow. A few of us never got our orders, I'm sorry to say. The waitress, whose first night happened to be that night was extremely polite and worked very hard; nothing that happened to them that night was malicious, nor could it have been predicted. How could anyone guess that a horde of hungry hackers would invade their place of business on a Saturday night? On the way back Nick, Bjorn, and I hit up a Waffle House for dinner because neither of them had gotten their orders at the other place, and we sat for a couple of hours talking and relaxing.
I think it's safe to say that we're all very pleased with last week's launch, though a few of the planned experiments didn't go off due to technical difficulties. We got lost a few times but managed to get back on track (after deciding to stop trusting my TomTom GPS and start using Google Maps on my phone instead). It's been suggested that we build a small instrument panel of some kind into Spaceblimp-4 so that we can verify that everything is operating normally by looking at fail-off indicator lights. It's also been suggested that next time we should probably have a pre-flight checklist to verify that modules are operating and certain procedures are followed before anyone lets go of the balloon. I think these are all very good suggestions.
Once again, HacDC has done something amazing. I can't wait for Spaceblimp-4. Maybe this time I'll load my own project to get a glimpse of what it's like to be that far up.