Now that the rocket flight was over it was time for another adventurous flight, this time via helicopter.
Rockets launched from White Sands land far uprange, about 40-60 miles (60-90 km) from the launch rail. The payload sheds all its accessories during the flight: the two motor stages that give the payload its boost into space fall off after burnout and the nose cone (the tip of the rocket) falls away during the descent to allow the parachute to open. These components (or what's left of them) also land somewhere in the desert.
Our mission was to find the payload, split it into two sections, and bring these back via two helicopters. Besides the Navy helicopter pilots and photographer, there was room for four of us. The team ended up as Ed (Wallops electrical engineer), Paul, Steven, and me (after Säm graciously turned down a seat in order to let Steven or I go). We were warned that this could be quite strenuous work -- each of the payload sections weighs 200-300 pounds, and the landing site could be a small ravine or a difficult incline. Luckily, FOXSI made this easy for us by picking a nice flat stretch of desert to settle on!
Even without the rollercoaster emotions of the flight and the anticipation of recovering FOXSI, the helicopter ride (my first ever!) would have been memorable. It took about a half hour to reach the landing site, during which we were treated to a spectacular view of the desert. 200 feet below us the sand dunes and vegetation created strange geometrical patterns on the desert floor. I was able to see for the first time how vast the famous white sands really are, the peculiar fine white gypsum powder giving the illusion of a giant salt basin. I saw tracks that looked like lake/river beds and creeks, obviously long dried but perhaps occasionally bursting back to life during rare desert rainstorms.
And then we found FOXSI.
I am sure that the mesquite bush our payload chose to land in is the thorniest one in the desert. It looked innocent enough, until we dove in to clip the parachute cords, and then its spines cut us at every move. I like to think of it as sneaky little FOXSI getting in a few last jabs!
But the landing was perfect! After FOXSI was finished observing the Sun, a shutter door closed over the telescope. The door carries a metal honeycomb structure that acts as a crush bumper, and it is this structure that the payload lands on. FOXSI landed on end on its crush bumper and then fell over on one side, snuggling itself into the thorny mesquite bush for us to find. (If the parachute had not opened as expected we would have found a hole in the ground instead of a happily resting payload.)
The work was straightforward: Ed vented the compressed gas carried in the payload for fine pointing maneuvers, we unbolted the two halves of the payload and broke all the electrical connections between them, and one by one we loaded the halves onto the helicopters using the large rocket cradles we had brought with us. We covered the open ends with large tarps taped to the rocket skins, and then we were on our way!
Except we needed a pit stop. The payload sections were so long that they stuck out the sides of the helicopter. The high air turbulence outside the helicopter ripped one of our protective tarps to shreds, exposing the detector end of our telescope and causing electrical connectors to fly around wildly. We landed again in the desert and used an entire roll of heavy-duty tape to tape directly over the end of the payload, creating a protective cover. This proved good enough to make it back to the launch complex with no further damage.
Back at the vehicle assembly building, the triage began. We were jubilant about the success of our payload, but now was the time (with all equipment, people, and memories present and intact) to figure out what things had gone wrong. We checked our alignment with the rocket pointing system to see if we could have been horribly off target, and found that this was unlikely.
We examined our telescopes and electronics for damage…and found a little. One of the seven optics modules stuck out a little farther than the others. This happened because a glue joint holding that optic in place had failed, allowing the module to move. Of course, with any payload damage a big question is whether it was the launch or the landing (a huge shock!) that caused it. In this case we *think* the shift happened at launch, although it's difficult to be sure.
The other optics modules all looked just fine, and the next day we did one last X-ray alignment test to check that everything was still functioning. With the exception of the one shifted module, everything looked exactly the same as it had before the flight. This is fantastic news, because it means we have a mostly intact payload which could be used again for future flights!
…which brings us to the big question of what's next! FOXSI has a second flight funded, tentatively scheduled for 2014. For that flight we have planned some upgrades to the instrument, but those plans did rely on recovering the payload in one piece (which it mostly is).
As we begin to look at the data I'll attempt to post some updates about our progress. First, though, is a big push to finish my dissertation in time to graduate this semester! And one more piece of exciting news -- I'm told that the official launch photos and videos are on their way to us soon. I will post these as soon as I get them!
Thanks again for all the warm wishes and support from all our FOXSI friends!
No comments:
Post a Comment