TODAY   |  April 14, 2014

Expert explains challenges facing search sub

Dr. Ellen Prager, a marine scientist and oceanographer, joins TODAY to discuss the submarine that has being deployed in the search for the Flight 370 black boxes.

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This content comes from Closed Captioning that was broadcast along with this program.

>> to ellen prager. good morning to you.

>> good morning.

>> so we now have these four solid pings. they've narrowed the search area to i think a size of about los angeles , about 500 square miles . i know it's not ideal. they'd like a smaller area. but is this doable for that mini sub, the bluefin-21?

>> well, for this autonomous underwater vehicle , it's certainly doable. the only issue is going to be time. it takes time to map the seabed. so they can definitely do it. it's a little bit on the edge of the depth capabilities. but it can do it.

>> let's look at a couple things. first of all, what is this technology? how exactly does it map the ocean floor ?

>> right. well, they will essentially send the auv down and it will guide or be powered over the sea floor and send pulses of sound down and then it will record the echoes. the echoes that are strong will give you something that's sort of light or sticking up from the sea floor , and the echoes that are weak or shadows or low spots, and then in a computer they will process all that information and you essentially get a map of the sea floor . and then what you do is you look for something that doesn't look natural. you're looking for something that doesn't look like a rock or the sea floor , and then they're going to go investigate that further.

>> and that leads me right to my question, because how can you distinguish the terrain down there, the topography in the ocean in that area is kind of rugged. could you mistake rugged terrain for something sharp-angled that you might suspect to be plane wreckage?

>> well, that's a great question. and that's one of the problems. they're going to have to go down and see what the bottom topography looks like, and hopefully there will be enough silt and things that it won't have covered any wreckage if it's there and you'll get things that have angles that just don't look natural. but it's not an easy task.

>> very quickly, you mentioned this. this bluefin-21 mini sub is at the limits of what it can do in terms of depth, almost three miles down. so what problems might that raise?

>> well, the problems with depth -- i mean, once you get down that deep in the ocean, the pressures are crushing. so they have to worry about problems mechanically with the bluefin-21. can it withstand those sort of pressures? so if it's on the edge, it should be okay. but you have to worry about starting to get technical problems when you get too deep.

>> thank you, always good to get your perspective. appreciate it.