Cameron to Walsh on Record 8,000-Meter Dive: You’d Have Loved It

The following is an email from James Cameron to Don Walsh, co-pilot of the bathyscaphe Trieste , following Cameron’s successful 8,000-meter dive to the bottom of the New Britain Trench. Don Walsh will be joining the expedition in Guam, prior to Cameron’s dive to the Challenger Deep in the Mariana Trench.

March 7, 2012

Don,

The 8000m dive went very well. Not an unqualified success, since the manip was balky and my push core sediment sample washed out on ascent because the sample door wouldn’t stow all the way, and because of the speed of the flow over the vehicle on ascent (5 knots average). But overall the vehicle performed like a champ. Plenty of power, and even though I lost one thruster, I still had 11 left, so the massive-redundancy approach worked. I never lost functionality. All lights and cameras worked. Sonar was balky… that’s going to need some work.

Bottom time close to 5 hours, range of exploration about 1.5 km horizontal, and about 300m vertical along the trench wall, which was like the Grand Canyon, vertical faces interspersed with angled scree slopes. Dramatic terrain.

The ponded sediment in the center of the trench was the finest I’ve ever seen. When the thrust-wash just barely kissed it, it formed silken veils undulating across the bottom, and then it would rise and hang in tendrils like ectoplasm. Not at all like the typical turbidite plains of abyssal depths. Where I dove the basin of ponded sediment was 1.5 km across, flat as a billiard table, and virtually featureless. It actually ended at a well-defined “beach” where the normal rocks and sediment commenced, terracing upward to the fault scarps. I explored up the scarps onto a plateau.

The small exposed rock faces had large communities of white anemones about 1 foot long. Hanging gardens. It was a completely distinct micro-habitat from the flat basin.

Out on the plain the dominant fauna were 1′ diameter jellies that would lie on the bottom or swim about 2 meters up. When disturbed they would fly off the bottom. There also were large numbers of amphipods in all sizes. The baited lander captured images of incredible aggregations, including individuals close to a foot long. I tried but was unable to rendezvous with the lander because the sonar was not cooperating. Normally the lander is a very bright target, and it should have been easy to find on that flat plain. But without sonar, nor accurate coordinates from the surface, it was a visual search, which is very limited. It might have been 50 meters to my left and I went right by it. I could have done an expanding-square search pattern, but I decided it wasn’t the best use of my power, when there was real exploring to do.

Actual deepest depth for the dive was 26,791′ (8221m). Initial descent speed was 4.5 knots, attenuating near the bottom to about 1.5 kt, before I trimmed neutral with a few small shot dumps totalling about 50lbs. I drove the final 100m down on thrust, very slowly (because I didn’t trust my altimeter yet… we’d just met and were only dating)… and parked on the bottom using about 10% downthrust.

Ascent speed was 5.7 knots slowing in the upper water column to 4.8. The soft ballast system functioned perfectly, giving the sub an additional 400kg of lift. The bag pops out automatically at about 200m depth and inflates slowly after the sub reaches the surface. It is an oil-over-gas system of our own design, which uses a spring-loaded poppet valve to open a bottle of nitrogen at 3500 psi when the external pressure balances on descent. The valve locks open, charging the bag, and a reservoir of silicon oil fills the tank so it doesn’t implode at depth. On ascent, the gas boils out of the silicon, filling the float bag in about 3 minutes after surfacing.

Surfacing at 4.8 knots is dramatic. I point the boom camera and the 1000w spotlight straight up. I can see the surface shimmering from about 100′ down. There’s a real sense of “ground rush” as the shimmering patch grows rapidly bigger, filling the “sky” above the sub. Then BWOOSH! an explosion of foam and bubbles, and the sub pogos back down about 5m, then rises again and comes to rest. I call it “Splash-up”… bastardizing a term from the 60′s space missions.

The only significant problem on the dive is that one of the six battery buses failed without adequate warning as I was making preparations to ascend. Some fault in the battery management system comms inside an external PBOF multi-bus box, probably related to water ingress, but I haven’t gotten a report yet from the electronics guys.

Unfortunately the failure took out the A-comms system, which was on that particular bus, so I lost comms completely. Fortunately the back-up modem, which is powered with its own independent battery, kept transmitting, so they knew I was coming up when the depth numbers started changing. They cleared back about a klick from my last known position and waited. I surfaced about 1500m from the ship, but plainly visible. That’s why I personally like night recoveries. The sub has so many lights and strobes it’s like a UFO mothership, visible to the horizon at night, from the bridge wing of a ship the size of Mermaid Sapphire.

Sitting down there at 27000′, alone in the dark, with no comms, no contact whatsoever with the world so far above, and nothing but the ingenuity of the engineering to get me back… it’s simultaneously scary and exhilarating. It’s the precipice we put ourselves on by choice, to test ourselves and our machines. I configured the cameras to get a good shot of the weights coming off and hitting the seafloor in 3D, but I can’t say I spent an undue amount of time on the lighting. I wanted to see those babies jettisoned as quick as possible. It’s a good feeling when 350kg comes off, with the characteristic “SHOONK” as the weight carriages run down the slide-rails.

Then I pulled the breaker on the shot-hopper magnet, and let the other 150kg of shot pour out, watching on the boom camera as it spiraled down into darkness in the trailing vortices under the sub. Then I just powered down everything I didn’t need and sat hunched in the dark, waiting… watching the numbers on the depth indicator count down toward the surface.

It was an interesting ascent. Virtually silent except for the soft whir of the scrubber fan, and the rustle of water vortexing down across the fairing at 5 knots. There was a slight rhythmic rock to the sub, due to vortex-shedding, which I normally didn’t notice because I’m usually too busy doing things… comms, photography etc. But in this low power contingency, I was just sitting there in the dark listening and feeling the sub. It was fascinating to imagine 8 kilometers of water speeding by vertically. I imagined the pressure coming off slowly as the ocean loosened its iron fisted grip.

You’d have loved it.

More to come…

See you in Guam.