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Altitude Control System, part I

In just 5 short months we will be launching the Adler’s most sophisticated (and complex) mission yet: the 2017 Total Solar Eclipse Mission. With TSEM we are hoping to place a camera in the path of totality at 80-90,000 ft, well above the clouds. This is nothing new for us… we have put cameras up many dozens of times… What will be special about this flight, however, will be that only will we be streaming the camera’s live, but we will be actively pointing it at the eclipse! To accomplish this we are going to need an exceptionally stable platform. If you look at our usual video you can see that maintaining pointing while the payload is undergoing its usual gyrations would be crazy!

So how are we going to stabilize our payload? To figure this out we first have to understand where most of the payload motion is coming from. Something must be pushing on the balloon/payload to keep it moving/turning/bobbing/swaying. Otherwise the motions would die out over the course of a few minutes. What could be pushing on the balloon/payload? The only thing it could be is the surrounding air… Our first thought was that it might be coming from wind… but that doesn’t make a lot of sense… The balloon is floating *with* the wind so the relative movement to the air is zero, or at least very close to it.

So what is it? Turns out there is a motion of the balloon through the air: upwards! As the balloon rises it pushes through the air at a goodly clip. It is just like a vertical wind! Our typical mission rises at a rate of 10-15 mph. If you’ve ever held a balloon of that size in a 10-15 mph wind you’ll appreciate just what a buffeting that can provide. It is no wonder that our cameras sway around like crazy for most of the flight.

So what we really need is to reduce our ascent (or descent) rate to a much lower number. If we could limit it to 1 mph we’d experience 100x less buffeting. Luckily we have a system to do just that. Last Summer David Abramov and Jay Yu helped to design and test a system to vent helium during a high altitude balloon flight. The video below shows the spectacular results of a test where we vented just enough helium to reach neutral buoyancy. That is, we were neither ascending nor descending. The section at the end… the camera wasn’t stopped for that, it is at full speed!

 

This prototype system was a nozzle insert that opened at a given time and then closed again when the vertical velocity was reduced to zero or near zero. It worked nicely, but it is heavy and bulky, difficult to set up, and requires an independent cutdown system. We want to do better! In Part II I’ll describe the new design David and Ken worked on this past autumn.

 

 

 

 

 

 

Permanent link to this article: http://farhorizonsproject.com/blog/altitude-control-system-part-i/

1 comment

  1. Dan Jakubik

    Impressive results achieved reaching neutral buoyancy. Keep up the good work!

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