What a monster week! We started Monday with the rotor untested, and today we formally notified CSBF that we’re completely ready for flight! There were quite a few bumps along the way, but stellar effort from everyone on the team got us to the finish line.
Monday we spent some time hanging the rotor, making sure the electronics in it were working correctly. NCT’s pointing system is rather confusing: we use a magnetometer to detect the direction of the local magnetic field, then feed that into a servo loop which turns the gondola until the magnetometer is “nulled”–that is, perpendicular to the magnetic field. Unfortunately, when we hung the gondola on Monday and told it to point, it started spinning in circles! The feedback loop wasn’t working at all…
Tuesday morning, McBride put together a breakout cable so he could inspect the voltages on the magnetometer and the servo loop directly. The cable was very helpful–we quickly determined the magnetometer was performing correctly, but the “torque bridge” that detects the force on the rotor was not zeroed correctly. With some fiddling of a potentiometer, we got that fixed. At that point, we wanted to go outside to test our pointing against some absolute references. Both our differential GPS and the magnetometer have weird readings in the metal hangar, so we hadn’t had a chance to check their offsets. Unfortunately, the winds were too high Tuesday for more than a brief solar panel test, so we decided to go out early Wednesday morning when the winds might be calmer.
Wednesday was the most epic day of our campaign so far. We were up at 4:30 am to get to the hangar by 5. At six we had rolled out to the wooden A frame to test our systems. Unfortunately, the winds were still too strong to actually hang the gondola, but we were able to confirm that our differential GPS was giving us correct attitude solutions. Also, with the help of our theodolite, McBride’s breakout cable, and a true-north reference on the tarmac, we were able to get a very good zero point for the magnetometer encoder. We gave up on the winds dying down at about 8 and headed back inside, ostensibly to take a break for some breakfast.
The final hurdle to clear before the flight readiness meeting was compatibility. This is a simulated launch where we connect up all the pieces of the gondola and hang from CSBF’s launch vehicle. It’s a chance to confirm all the communications electronics are working and verify physical clearances. We ran into a CSBF guy on the way in, who asked if we could be ready to do compatibility that afternoon. (With CSBF trying to launch three gondolas and the winds turning around late this year, they hoped to get everyone to flight ready as soon as possible.) We said we could be. There was one catch–the engineers had to finish testing an electronics isolation box they had built in a marathon effort the day before! With no time for breakfast, they set to work while the CSBF riggers and technicians swarmed the gondola prepping it for the afternoon’s test. After one small hiccup, Jane and McBride got the box working at 11. Justin and Wei-Che ran to Fred’s to get takeout (we thankfully had pictures of the menu on this blog!) while Mark led the rest of us through our flight checkout procedure. We rolled open our hangar doors and pushed out to “Big Bill” at 1:00 p.m., right on schedule.
Compatibility took the rest of the afternoon. We hung the ballast hoppers that allow CSBF to regulate our altitude in flight and fit tested the crush padding which should protect the gondola on landing. We tested our uplinked commands and downlinked telemetry though the tower, just like we will in flight. We stood around in the sun and waited. And, at 5:30, we wearily rolled back in and adjourned to Fred’s for dinner.
The formal final step, the flight readiness briefing, happened today. Prof. Boggs arrived from the airport, and we finalized our flight requirements and specified recovery personnel. Looks like we’ll be second in the flight queue behind Fireball. The weather’s still kind of spotty, but Fireball is planning to show tomorrow morning for a potential launch. We’re just amazed at how fast things came together for us! It’s really been an incredible week.