A sad day for our underwater cousins:
"The ABE (Autonomous Benthic Explorer) has used its on-board acoustic transponders and five thrusters to scan the seafloor for over 15 years - locating, mapping, and photographing hydrothermal vents, volcanoes, and other features of the great deep. Marked with "NCC1701" due to its resemblance to Captain Kirk's ship, ABE has performed more than 200 missions collecting valuable data for researchers worldwide. But something went wrong last Friday on an expedition off the coast of Chile and ABE just stopped - nothing was ever heard again. No word yet on whether ABE can be located or recovered."
I can't imagine the amount of engineering that went into a UUV built decades ago. It's a shame it was lost, I would have loved to look at it, if it had ever made it into a museum.
OMG!!! They found R'lyeh!
The glass spheres were in the upper two pods (3 17", 1 10" on each side, two of those housed the acoustic transponders). We also had two 10" spheres in the tail, one for buoyancy, the other housed the camera strobe.
In terms of failsafes, ABE had several layers. ABE carried about 70 lb of ascent weights. If anything went wrong, they were released (conversely, they only stayed on if all was right) and ABE would rise to the surface. Of course none of that mattered when the vehicle got hit by the equivalent of several sticks of dynamite. Imploding spheres at 4500 psi release lots of energy, most likely there was a "zipper" effect and they all imploded.
We often operated ABE in a risky manner (knowingly). We went on expeditions to remote places on any ship available with no backup ROV or submersible. If ABE got in trouble, no rescue would be possible. These were the expeditions where we made our greatest discoveries.
ABE died as it lived, on the edge. We're regretful but proud of what it accomplished. We discovered new hydrothermal vent sites all over the world, mapped coral habitats on remote seamounts, mapped the calderas of a subsea volcano. Dozens of scientists, engineers, and students used data from ABE to advance their research. It was a heck of a ride.
The decision to use glass spheres was made with a full understanding of the risks. For deep operations, glass spheres provide much more efficient buoyancy than syntactic foam or buoyancy from pressure housings. It's a two-edged sword. By using glass, ABE was much smaller and lighter than it would have been. This was an informed risk that worked out fine for us many times (221 successful deep sea dives). Our newer AUV, Sentry, has no glass spheres. Our latest hybrid AUV, Nereus, uses ceramic buoyancy spheres. Its the only way to get really deep. Take the risk or don't bother trying. Nereus successfully dove to the bottom of the Marianas Trench last summer. We have never been naive to these risks.
Also, the REMUS you show above is a shallow water vehicle. ABE was rated to 4500m. The deep sea REMI are fatter and heavier.