29 April 2016Halfway To Summit Station
The crew has surpassed the horrible sastrugi zone, which continued to cause our ARCS (Air ride cargo sled) pouches to detach from the decks. The battens pulled away from the decks so the crews had to improvise a different strapping method.
Before they left the sastrugi behind, the WeatherPort tent sustained additional damage, with several new tears allowing snow to blow into the team's shelter. The crew used a Speedy Stitcher sewing awl to repair the tent, closing it off to the elements. They also moved cargo cages away from the tent wall to prevent further damage.
Left: inside the WeatherPort, patches repair tears in the tent wall. Right, sideview: tears are visible in the white WeatherPort, fabric,. The green helium cage is being moved back on the deck to prevent further damage. Gas cylinders must be enclosed in these cages for safety reasons, but they fill up with snow, adding unwanted weight to the decks. Photos: Robin Davies
Sled Mobility Optimization Tests
A new air manifold system developed this season to reduce the amount of time needed to check and maintain pressure in each airbeam pouch (which underlay and support the decks) has been less than a ringing success. Staff designed a manifold system that fed out of the pouch opening and extended to the side of each deck, allowing the operators to make quick checks to better maintain stable pressure. Unfortunately, several of the valve stems have snapped off, likely due to cold temperatures causing the material to become brittle. Broken stems allow air leaks, causing the pouches to lose pressure. The team has gone back to the original method of checking and filling the pouches directly from the airbeam valves.
Left: the red hose of the manifold at the deck corner was intended to provide easy access to all of the airbeams within the pouch. Right: without the manifold, GrIT operators have to unfold the pouch and access each valve individually. Photos: Robin Davies
In addition to the manifold issues, some of the airbeams migrated backwards, dislodging from under the load. The crew had to pull them forward into place – not uncommon, but undesirable. Finally, one pouch had to be fully replaced with our spare because the broken valve stem could not be fully repaired and continued to leak.
Once all of these repairs were made and the GrIT moved beyond the sastrugi, the loads seemed to settle in and the tractors started to tow them more easily. The D7 was loaded onto its own HMW sled riding on top of tires mounted to the Durabase. Our team reports that this configuration seems to be hauling very well, and may be a new way to approach heavy equipment transport. The tires protect the Durabase, which provides a solid platform to which the equipment may be mounted. The D7 has not shifted and they are happy with this load.
From left: The D7 loaded on its tire/Durabase sled before leaving Thule, and on the road packed with snow. Finally, a Case tractor hauling the cargo sled (seen in rear view mirror) passing the D7 sled . Photo: Robin Davies
More Field Repairs
Next, the Case 500 tractor developed a hydraulic leak when a steel return line cracked at a point where the bracket was welded. Having encountered a similar issue on a previous traverse, the crew carried a spare, but because it was manufactured for another Case model, the crew had to braze the part to fix the leak.
To leverage the advantages of having four crew members, the team decided to add a night shift to "leap frog" loads forward. Three GrIT members move sleds forward through the day while Ben sleeps, and he continues at night. This strategy has helped the GrIT stay on track, literally: at night, Ben packs a trail for the cargo sled to follow during the day. Coupled with improved weather conditions, the team has made steady progress, even gaining 35-40 miles on several days.
Science Support Update
The crew has retrieved several data cards from weather stations installed by Zoe Courville's project, SAGE, an U.S. National Science Foundation (NSF)-funded study of sunlight absorption and firn compaction. Some stations are deeply buried and will require significant effort when it is time to remove them later this season.
Left: The buried weather station. Right: Once we excavate the station, we retrieve the data card. Photos: Robin Davies.
The Arctic Research Support and Logistics Program within the National Science Foundation’s Division of Polar Programs funds the GrIT. CH2MHILL Polar Services and Cold Regions Research and Engineering Laboratories are working together with the NSF to develop the traverse infrastructure and route to Summit Station. The 2016 spring traverse delivers cargo to Summit Station, and continues efforts to optimize mobility, GrIT will provide direct science support to several projects, retrieving instruments for a soon-to-be-completed effort, and laying fuel caches for upcoming projects. Follow GrIT’s progress here: http://datatransport.org/grit.