We got up this morning and everything seemed fine on Autosub, so it hit the water just after 7am. The mission plan was to do the deep test – descend in a series of steps to 5600m, checking the buoyancy on the way. Then do a lawnmower survey, and then a series of passes back and forth progressively closer to the bottom, with the last one at just 20m altitude. Finally slowly ascend back to the surface with a few more buoyancy tests on the way, partly to check that the syntactic foam really can survive almost 600 bar of pressure.
Everything looked fine at first, Autosub began its long dive, and we went for breakfast. However, shortly after we got back things started looking less positive, and shortly afterwards the sub was back on the surface having aborted the mission.
At this point the lightning that had been rolling around all morning got rather closer, and as the team attempted to retrieve the sub we were treated to torrential rain and lightning strikes all around the ship.
Retrieving the sub is a fairly challenging task: The sub has a line across the top and the trick is to catch that line with a grapnel, pull the recovery lines out of the sub, attach them to the lines from the winch and haul the sub on board. All of that is rather easier said than done on a pitching ship that needs to get close enough to the sub for it to be grappled without the propellor sucking it under. To make it even more fun, the grapnel is launched from a compressed air gun and the direction of flight isn’t all that predictable. The first attempt didn’t go all that well – the team might have been a touch distracted by the lightning! However, on the second go, just as the rain eased off, the grapnel caught the line and Autosub came back on board.
It’s always a bit awkward being the guy who does fault detection. While everyone else is hoping their mission goes smoothly, you’re secretly hoping that some fault will develop that you can then try to model and detect. In this case, however, we were all disappointed. It appears Autosub got to 1500m depth but then lost power for around five minutes. The result is that there’s no data logged – everything looks completely normal right up to the point that data stops. That means there’s no way we could have diagnosed the problem.
The rest of the day has been spent trying to figure out what went wrong, and coming up with solutions. Autosub is once again on its way to being tested first thing in the morning, and it appears that the Deep Tow winch has also been repaired, so as I write this, Hybis has just gone over the side for its trip to 5600m. We’ll all be hoping for things to go better overnight!
You call that a field?
Just how buoyant is Autosub? The picture shows Miles aiming but nowhere near the water π
Very good π π π
Yeah, nice one. π
If field robotics was actually done in fields, it would be a heck of a lot easier!
not where I was to go in the field!