Archive for January 24th, 2013

Brain Storm

Thursday, January 24th, 2013

Hey All!

So today our team bounced some ideas around to see if we could find a solution to Silbo's predicament.  For the past few months, Silbo has been faced with a strong current ranging from North North-West to North North-East that has slowed us to half of the speed we have flown in the past.  One idea that we had stemmed from an event that happened last week, when Silbo had an error that caused him to only dive to 600m.  When he surfaced he reported that the currents were closer to what the model is telling us: flow to the south west!  So the initial idea thrown around was only having Silbo dive 500m, however this would cause the pump to move twice as often, bleeding the battery.  Another option suggested by Ben from TWR, is to have Silbo dive to a depth we feel would have favorable currents, and maintain that depth and have that favorable current push us for a few hours.

Antonio and I suggested that if we try this 'hover' strategy, we should try for 200m.  It seems that the currents  towards the surface may be closer to what the models are telling us, so we chose a depth that wouldn't take us too far into the unfavorable current.  Another aspect to take into account is that we want to stay out of the productive surface waters.  From our experience and the word of others, the rule of thumb seems to be that barnacles stick to waters >15˚C.  As seen in the temperature time series above from Silbo, 200m keeps us in waters that are roughly 12˚C.  We may not get to this test tomorrow, but I will update you guys on our progress over the weekend.

Down south, Challenger continues to shoot through South African waters on her way towards open ocean.

Tomorrow, we may move the way point more to the north to take better advantage of this northward current we are seeing and ride it out for a few years.  It seems the counter clock wise spinning eddy is slowly moving off shore, so we are trying to bring Challenger towards the outer edge to avoid the possibility of being dragged south when we reach the other side of the eddy.

 

Force Wind Sea & Honor

Some Fine Tuning

Thursday, January 24th, 2013

Hey All,

I just wanted to leave everyone with a quick update before the end of the night.

In the North Atlantic, Silbo is still muscling his way through the northward flux as we brainstorm ideas to find a more favorable route to take.

Tomorrow, we may make the way point change I had mentioned

Although it looks like there is a clear path for us to take based off of the model, this overlay is only of the surface and tomorrow I will focus on getting subsurface currents to see if that picture gets any better.  This subsurface northward flux has plagued Silbo now for months and we really need to figure a way out.  One glimmer of hope was during an oddity that Silbo encountered late last week.  Silbo's mission file reset mid segment resulting in a short dive that prevented Silbo from going the full 1000m.  On the short dive, Silbo recorded currents that were in fact flowing in the general direction of what the model was showing, providing us with the theory that the subsurface currents are what is slowing Silbo's progress.

If we can pin point where these negative currents are, we may be able to adjust the depth Silbo is flying to to try and make some more favorable progress.  This however will cause a trade off with power consumption as we will move the pump more by making shallower inflections so we will have to weight the consequences when there is enough evidence to make a decision.

On the other hand, in the South Atlantic Challenger is still making good progress as she flies towards international waters.

Challenger is now 175 km away from international waters.  Once there and free of the danger of interfering with another countries boundaries, we will expand our view and find the most ideal path onward towards Brazil.

The way point given towards the end of last week is still proving its worth as it now allowing us to fly along the top of this warm eddy that will essentially carry us out of South African waters.

This is also seen in the maps from GeoEye and SeaStar that Antonio has gotten for us that show the warm eddy is similar proximity to the glider, providing that current to the north west that will carry us out to sea.

Over the past couple days, Dave has also been doing some fine tuning to Challenger's flight parameters.  For example, we have been adjusting the cc's on the pump throw to make adjustments to our dive and climb angles, changing the gains on the steering parameters, and testing out the low power mode.  The last one here is key as we will need to conserve power if we want to make it all the way across the Atlantic Basin on these batteries.  She has impressed us so far, but she still has a long road ahead.

Force Wind Sea & Honor