Out at the Shear Zone
Sorry for the long delay! We just got back from the shear zone, about 30 miles out from McMurdo. Seeing it for the first time really helped put in perspective what we've been working on for the last couple of years. The shear zone is the area where the Ross ice shelf meets the McMurdo ice shelf. The two shelves have different speeds, creating a particularly nasty area riddled with crevasses at the interface between the two. The traverse route crosses perpendicular to the shear zone, but still has to travel over 3.5 miles of heavily crevassed terrain. These cracks change season to season, and often times new ones open up each year. All of them are invisible from the surface, however, and many are hundreds of feet deep.
Jim and I drove a Case tractor to get to the South Pole Traverse camp on the near side of the shear zone. I found out while en route that our vehicle has an excellent fuel efficiency and burns 3 gallons of diesel per mile travelled. The route was covered in dense fog, which made it hard to see the flags marking the ice road. In those conditions out on the sea ice, it's a strangely surreal feeling to be surrounded by absolutely nothing but white, with no visible horizon or visible features of any kind. Luckily, we were able to navigate by GPS between flags, and reached the traverse camp on time.
Our Case, loaded up with Yeti and equipment in tow.
The SPoT camp, with living module (red) on the left, the H2 module (my living space) in blue, and several tractors.
We were initially supposed to have a week to test Yeti in the shear zone, but that got crunched down into 2.5 days. The first day, our goal was to collect radar data over a crevasse and setup the route that we would send it off on for an autonomous run the next day. Zoe and Allan headed out ahead of us in a Cat, and Jim and I followed in a tractor. We were looking for one specific crevasse that would give clean radar signatures so we could collect a data set that will later be used to autonomously detect crevasses. When Allan drove over the snow bridge in the cat, it opened up a small hole on the surface. Jim and I saw the hole just as we were about to drive over it, and weren't able to stop in time. We knew the crevasse was only a meter or two wide, but it was bizarre to look behind us and see the hold widened out to around 5 feet. We had to backup and drive back over the hole again, since the road was the only portion of the ice that had already been surveyed. The Case made an ominous sound clunking in and out of the hole, but we made it back across in one piece.
After successfully 'finding' a decent crevasse to survey with Yeti, we attempted to drive a rosette pattern to approach the crevasse from different angles with the robot. Our only goals were to keep Yeti driving straight and avoid the 5' hole we just made, and I found it absurdly difficult to keep Yeti safely away from the hole. At the time, I decided that this was target fixation, but we would soon find that Yeti has a magnetic affinity to holes in the ice and bamboo flag poles. While driving around autonomously, it seems to lock in with laser precision on the only one or two obstacles around for miles, which I'm sure is a corollary of Murphy's law.
It's almost 2am and I have to get up early for another long day of testing, but I'll write up the rest of the work at the shear zone tomorrow. Rest assured that Yeti did not fall in a hole, but did annihilate many bamboo poles.
Mt. Erebus, an active volcano, from a distance. It's not really nighttime, since the sun stopped setting last week, but it does go low and create very cool lighting conditions.