B. B. Walden

Surveying a subsea lava flow using the Autonomous Benthic Explorer (ABE)

This paper summarizes results from the first science deployment of the Autonomous Benthic Explorer (ABE), conducted on the Juan de Fuca Ridge (46°N, 129°W) at depths between 2200 and 2400 m. Using long baseline acoustic transponders, the ABE descended with precision to a preassigned starting point, then executed dead-reckoned tracklines. It followed the bottom at distances between 7 and 20 m using an acoustic fathometer as a reference sensor. The ABE mapped a new subsea lava flow with a magnetometer, imaged the seafloor with a stereo snapshot video system, and mapped a hydro thermal plume with conductivity and temperature sensors. The ABE completed 7 successful dives and covered over 35 km of tracklines. Detailed power records were logged, which permits extrapolation of the ABEs performance to other missions and higher capacity batteries.

Fine-scale seafloor survey in rugged deep-ocean terrain with an autonomous robot

The rugged, mountainous regions of the deep seafloor hold both great scientific interest as well as a host of difficult challenges for autonomous robots. Exploiting its abilities for precise navigation, trackline following, and bottom-following in rough terrain, the autonomous benthic explorer collected fine-scale bathymetry, magnetic, temperature, optical backscatter and conductivity over a rugged, neo-volcanic and active tectonic zone of the southern east Pacific rise (18/spl deg/S). We combined these data sets to produce a variety of maps showing dramatic terrain in unprecedented detail. We also created the first systematic map view of hydrothermal temperature anomalies over the mid-ocean ridge.

Multisensor mapping of the deep seafloor with the Autonomous Benthic Explorer

We used the Autonomous Benthic Explorer (ABE) to create maps of an active spreading center on the mid-ocean ridge at a depth of 2600 meters. We took advantage of ABEs precise navigation and bottom following capabilities and produced detailed bathymetric maps with a scanning sonar, and photo-mosaics using ABEs video snapshot system, and measured the temperature and optical backscatter of the water. Refinement of ABEs transponder fixes, based on using returns gathered at the vehicle, contributed to the consistency of the results.

Newly developed specification and test methods for syntactic foam buoyancy material for deep ocean manned submersible vehicles

Syntactic foam buoyancy material is a critical item in the performance of deep ocean manned vehicles. The only known specification for syntactic buoyancy material for high hydrostatic pressures is MIL-S-24154A(SHIPS). This MIL spec dates back to 1967 with the last amendment dated 1991 and it does not incorporate the latest advances in the testing of syntactic materials nor the knowledge and experience base which has been obtained as a result of its use over the last 20 years. This paper presents the syntactic buoyancy material specification developed by the Woods Hole Oceanographic Institution for the manned submersible vehicle Alvin. The specification incorporates the best testing practices of syntactic materials for use in submersible vehicles to insure the required performance of deep water buoyancy material. In addition, this paper presents a method for utilizing an acoustic emission testing technique to determine the depth at which structural breakdown of the syntactic material occurs.

ATLANTIS II: A New Support Ship for Alvin

R/V LULU, a small, slow, single purpose catamaran vessel, has been operating as mother ship for the research submersible ALVIN since its construction in 1965. It has covered 136,000 miles in support of 1,300 science dives, exceeding its intended life and demonstrating the need for a more capable support vessel. ATLANTIS II, a 210 ft. research ship selected as LULUs replacement, has been refitted for submersible support. Her general oceanographic capability has been retained, so that future voyages may involve more than one mission. The new submersible handling system utilizes a stern-mounted A-frame with a single point lift. The ALVIN structural frame has been modified to permit lifting from above by a single rope.