Via a story on NPR's All Things Considered (last story on the page: audio link) the intrepid research submarine Alvin is going to be replaced with a larger sub capable of deeper dives and longer stays at depth.

Alvin is a truly storied scientific instrument, one of those few machines that almost singlehandedly revolutionize a scientific field. I'm looking forward to seeing what her successor will do.

This post isn't entirely about the excellence of Alvin - I also have a little bit of an axe to grind. Let me point out that, in this day of submarine ROVs with ever increasing capabilities, the thing that oceanographers and deep ocean biologists want is a machine that will enable them to go in person into the depths. A dive in the new sub will take up to ten hours, cramped up in a space about the size of the interior of a VW beetle, with all manner of projections and angles to increase the discomfort. Internal temperatures during a dive hover in the neighborhood of zero celsius, and if something goes seriously wrong, you die. Much better to send a machine, don't you think? But no: the people best equipped to make the judgement, the people who will be trading sitting in front of a computer in a climate controlled room, sipping fresh brewed coffee for a cramped, cold, dangerous machine that will put them right next to what they want to study - they choose the sub. Why? because you simply do better science on site than you can remotely, and it's going to be that way for the foreseeable future. The lessons for space exploration should be obvious. I'm looking at you, Bob Park.

Dismounting my hobbyhorse and returning to Alvin, there's an interesting story in the book Water Baby. When Alvin was under construction three pressure spheres were made and tested. The best (no. 2) was used on the sub, and sphere no. 1 was to be tested to destruction. The test vessel was a large oil filled tank which could be pressurized to simulate dives to various depths. The 40,000 pound lid of the vessel screwed into place on top. The crush test of sphere no. 1 was also going to be the first test of the pressure tank above 4000 psi. From the book:

At 4300 psi there was an explosion. In the next second the engineers calculated the probable trajectory of the tank's lid, concluding that 40,000 pounds of steel were headed for the tin roof above them. They ran, all of them headed at once to the only other door at the far end of the building. "I remember the instantaneous transport of myself, like a Tibetan monk using the mind to will myself out of that building" Walsh said.
[...]
The super tank looked oddly untouched and its 40,000 pound lid, undamaged, was in place. The deadman was broken and its 40 foot cable was gone. When they removed the cover, they saw that the shrapnel had come from the upper threaded portion of the tank. The lid had shot up at least 40 feet and dropped back onto the tank, driving it about three feet deeper into the ground.

In the tank sat sacrificial sphere no. 1 undamaged.

The test tank failed at a pressure equivalent to 9600 feet, testing the sphere judged to be of the lowest quality.

The most interesting part about Alvin, is that when she was built, nobody really wanted her. She was largely the creation of a single mind (Al Vine) who believed in her utility. Equally, when she sank in 1968, there were few other than her crew and handlers who thought it was worth salving her.

They stand vindicated.

Robert Ballard's Explorations: A Life of Underwater Adventure has an interesting chronicle of his swearing of non manueverable submersibles like Trieste, his faith in Alvin like craft, and his on-again, off-again love affair with ROV's.

That's supposed to be 'swearing of off'. :(

According to my source at Woods Hole, Alvin is booked solid for the next four years. The Alvin II is not to be a replacement, both are to be working at the same time. According to her (http://www.whoi.edu/marops/vehicles/alvin/user_manual.html that's her in the right side of the picture), there is also nothing left of the original Alvin; every part has been replaced over the years, including the main pressure sphere two years ago.

Looks like Alvin will be with us for a while yet.

"This is my grandfather's axe. We've replaced the handle four times, and the head once, but this is my grandfather's axe."

Ed - The launch date for the new sub is 2008 AFAIK. I expect there will be an overlap of a few years at least, but funding realities being what they are it's likely that once the new sub is fully up to speed pressure will mount to retire Alvin. I hope they keep her in use as long as possible, though.

Andrew, me too. It's a heckuva machine. According to my source (wish I knew her name, I only know her from Yahoo chat), there is enough work for ten such vehicles.

"Because you simply do better science on site than you can remotely, and it's going to be that way for the foreseeable future. The lessons for space exploration should be obvious. I'm looking at you, Bob Park."

However, while this is true as an absolute argument, it is not true from a relative sense. The difference between undersea exploration and space exploration is the tremendous cost associated with keeping the humans alive in space. Yes, they can do more than a robot, but they cost far more than a robot too.

In fact, it might be worthwhile for someone to do the cost comparisons--compare the cost of a capable ROV to a piloted submersible. Then compare the costs of a capable Mars rover like MER to a human mission.

... And then we have to take one step back and ask WHY it is so much more expensive for human space exploration versus robot exploration.

It certainly isn't "the tremendous cost of keeping the humans alive in space" - it isn't much more difficult than doing the same in a submarine (and in some ways, easier). The issue is the cost of getting them there. Space will never be cheap when we use expensive throwaway rockets to get there.

Which isn't to say that robots don't have a place in space, under water, and so on - there are places it will continue to be more practical to send robots, especially for initial exploration. Just don't try to justify robot space exploration by the current silly way we get to space.

Well, I hope they use Alvin and Alvin II wisely... and I also hope they don't forget to safeguard their investments, with the Sub Club (tm) :-)

" it isn't much more difficult than doing the same in a submarine (and in some ways, easier)."

Justify this statement.

Submarines do not have to deal with as harsh a thermal environment.

Submarines do not have to deal with as harsh a thermal environment.

...and spacecraft do not have to deal with 2000 psi pressure differentials.

"...and spacecraft do not have to deal with 2000 psi pressure differentials."

Which can be solved by adding steel. Solving the problems of deep submergence is not the same order of magnitude of solving the problems of spaceflight. Bathyscapes, for instance, are relatively crude devices that have been dealing with huge pressure differentials for a long time.

"there is also nothing left of the original Alvin; every part has been replaced over the years, including the main pressure sphere two years ago."

I believe that some of the original parts have been on display at the museum at the Washington Naval Yard for quite awhile. I'm not sure if this includes the original pressure sphere or the original superstructure.