Regarding the saltwater submersion: I think your scenario is not correct.

The whole orange thing displayed on that page will be have to be in contact with saltwater. Otherwise the ultrasound pinger (the cylindrical aluminum thing) doesn't even start emitting pulses... (conductive liquid on sensor pads is how they normally detect that they have to turn on)

The "lifetime" of 30 years, or 17'000 operating hours is for how long it's certified to run in a non-crashing normally operated airplane.

The 30 days in saltwater probably means that no moisture will have crept in through the covers and seals: You can rinse the power-connector and Ethernet with deionized water, let it dry, connect to the computer and read it out.

{A assume that these devices are read out much more often in cases of non-fatal crashes where they weren't subject to the elements that much.}

The block diagram they show has an separate component for the nonvolatile memory, in a "Crash Survivable Housing". Also I assume that the company at least has some plan for accessing data given a complete disintegration of the memory module, probably by contacting single flash chips.

EDIT/ADDED:

http://edition.cnn.com/2014/04/23/world/asia/malaysia-370-bl... says: """A lot of our work is with undamaged recorders and it's very easy to download them, much as you would a USB memory stick,(...)""" and """One of the most challenging scenarios is when the board itself is damaged: "We could take each individual chip off the circuit board, read those out individually, and then with the help of the manufacturer, piece all that information together,"""

> {A assume that these devices are read out much more often in cases of non-fatal crashes where they weren't subject to the elements that much.}

They're read frequently during maintenance. They are required to be checked to be operable.

Which is really only relevant if it's ever found. The ocean is HUGE.

Ever is longer than the ocean is huge :)

It may be practically impossible to find with today's technology, but if the next 100 years of progress is anything like the last, there'll be large scale hobbyist exploration of the sea floor.

The surface area of the world is 510,072,000 km², 70% of which is ocean. That's absurdly large if you're exploring it with 8 figure submarines, but not at all if you're exploring it with the 2114 equivalents of 2014 $100 aerial drones, especially given a larger, wealthier society with more leisure time.

"especially given a larger, wealthier society with more leisure time."

Didn't technology promise that to us 50 years ago? Now we're busier than ever.

This suggests that's not the case:

http://en.wikipedia.org/wiki/Working_time#Gradual_decrease_i...

And work aside, think about living life without modern conveniences such as washing machines, dishwashers, fridges and freezers, vacuum cleaners, electric/gas ovens, microwaves, kettles and air conditioning.

Running a household a hundred years ago (or fifty years ago depending on wealth) would have been a much more time consuming affair for a significantly lower standard of living. I expect that trend to continue.

Well, if we assume that we're looking for an aircraft with a few large pieces, and it's only a matter of time before cheap autonomous submersible vehicles become common, then it probably will be found some day. Might take a decade or two, but at some point we'll extensively map the rest of the oceans.

I guess the question becomes who is going to pay for these robots? They'll need the ability to dive deep, explore, and then come up for "air" (a recharge). Those aren't going to come cheap. Perhaps the undersea cable conglomerates but it's hard to imagine the use-case for mapping inaccessible areas.

Extend past a few decades. A post-scarcity society would almost certainly search every square metre of the ocean for this airplane, assuming humans are still making decisions.

You say "post-scarcity" like it's an inevitable scenario. Resources are finite. Energy is finite. Exponential growth doesn't last forever.

> Energy is finite.

With enough renewable energy from the sun, there is very little we're constrained by

http://www.sandia.gov/~jytsao/Solar%20FAQs.pdf

"All together, the technical potentials can be estimated to be: Solar electricity: 89,000 TWc · (1-0.708) · (1-0.0345) · (0.3) = 7,500 TWc Solar fuels: 89,000 TWc · (1-0.708) · (1-0.0345) · (0.1) = 2,500 TWc Solar thermal: 89,000 TWc · (1-0.708) · (1-0.0345) · (0.225) = 5,600 TWc

These are huge potentials, dwarfing by many orders of magnitude those of the other."

Extend past a few decades and you're beyond the lifetime of the black box, sadly. It would be really frustrating to finally find the plane only to never actually find out what happened.

Well, the U.S. Navy for one. Just like the air force uses drones, I expect underwater drones to come in quite handy. Submarine tracking, for example.

It might be covered by sediment by then.

Obviously there will be huge differences between different parts of the huge oceans, but as a single data point: I've seen photographs taken of the Titanic wreck, where still single shoes can be seen laying uncovered on the ocean floor in the vincinity...

"Equivalent to finding a pen in San Francisco" - http://www.cockeyed.com/science/flight_370/flight_370.html

I don't like that comparison, because when I think of San Francisco I think of lots of buildings complicating the search by requiring you to go floor to floor, but the comparison is just looking at land area, so it's easier than it sounds (but still really tough).

For mine, the topographical variations of the ocean floor (combined with the fact they're largely unknown, at least to any level of detail) are probably similar to a floor-by-floor search, but you're right than basing it just on area makes for flawed comparisons.