RV Mirai has been working through some weather over the last few days. Winds have been steady from the NE30 gusting 40 kts and the seas, short and choppy in this shallow portion of the Chukchi Sea have been running between 3 and 4 meters. Though air temperatures are consistently below zero, the sea surface temperatures remain above 2ºC so there is no risk of freezing spray. RV Mirai takes the seas well however. There is an occasional toss against a bulkhead, and at times an inopportune roll about your bunk but generally she rides well. There are some that don’t appreciate that however, there have been fewer young technicians showing up for meals lately.
Part of the reason for the good ride is the huge mechanical anti-roll device. In a large compartment abaft the bridge, massive weights are set on arced rails and driven by computer controlled motors that are fed by input from accelerometers to counteract the roll of the ship. Automatic safety mechanisms will centre the weights on the arc and locks will secure it in place if necessary. It is a one of a kind system says the Captain, and though quite effective, is very expensive to replace parts.
Due to her excellent seakeeping abilities combined with heave compensated cranes RV Mirai can conduct over side science in some pretty extreme conditions. The Mirai will comfortably do overside CTD rosette casts in winds up to 33kts and seas to 4 meters. So far during this particular blow no casts have been deferred and they continue 24 hrs day, but that may change.
Capt David (Duke) Snider
Photo: The active anti-roll device fitted on RV Mirai