|High speeds on the high seas
March 25, 2000
By Dr. Dan Fornari
Sunrise saw RV
Melville steaming at nearly 14 knots through glassy
seas on a heading of 189°, just west of South. The
ships speed overnight was more than 1 knot faster
than normal. Sea swells were low, so the ship did not have
to battle against waves. Whats more, a surface current
moving in our direction actually helped push the ship south.
Scientists on board need to calculate how
long it takes to get to each site where seafloor surveying
will take place. To do this, they need to know the distance
they have to travel (by measuring it on a map) and the speed
the ship is going. They find the ship's speed using the Global
Positioning System of satellites, which calculates ship positions
and speed very accurately.
these two pieces of information, they can use a basic mathematical
formula that everyone needs to know: T=D/V, or Time equals
Distance divided by Velocity. If you know how fast you are
going (your Velocity), and you know the Distance you have to
go, you can always figure out the time it will take you to
get to where you are going!
Onboard Melville this evening at 2200
hours, scientists received information from the ships
bridge that the ship was 130 nautical miles from where it will
stop to test the multibeam sonar system. We must make absolutely
sure that the sonar system will collect extremely precise and
reliable measurements. The ships average speed today
has been 13.3 knots (nautical miles per hour). So we calculated
that we will arrive at our first stopping point in 9 hours
and 48 minutes, or at 0748 hours on Sunday, March 26. You do
the math and see if we are right.
During Expedition 3 we will tell you when
we start transits between our survey sites, what the distances
between sites are, and what we expect the ships velocity,
or speed, will be. We ask students to use the Mail Buoy to
send us their estimates of when we will get to our next survey
sites. We will post replies on the Mail Buoy.
Today there was lots of activity on board.
Scientists began to organize their watch schedules: 4 hours
on watch and 8 hours off watch. At the same time, technicians
were preparing the DSL-120 sonar for survey operations.
Technicians from Scripps Institution of Oceanography were also explaining
the ships different echo sounding systems and how to
keep good logs, or records. Keeping good records is critical
for any experiment, whether it is in a lab or in the ocean.
The ships crew was busy keeping all the systems on board
working well. From the engine room to the galley to the bridge,
everyone was working hard. At a fire and boat drill this afternoon,
scientists learned what to do in case of an emergency at sea.
We will have such drills each week.
Scientists and technicians continued preparing
for the start of survey operations into the night. Everyone
is looking forward to starting the seafloor mapping and seeing
firsthand evidence of volcanic eruptions on the seafloor.