Why hasn’t COSI launched yet?

We’ve been waiting for a good launch day since April 1, and two weeks later we’ve only had one launch attempt that got canceled due to weather. A common question from friends and family back home is: what’s wrong with the weather?

We don’t just need a good day to launch; we need a perfect day. Here’s a better question to ask: why do we have such stringent launch conditions? There are a couple of reasons for that, but before I get into those, I’ll briefly remind you what happens during a balloon launch (for a more detailed description, check out one of Carolyn’s earlier posts: http://cosi.ssl.berkeley.edu/its-a-harsh-continent/).

The payload (COSI) gets suspended from the launch vehicle. The parachute and balloon are laid out upwind of the launch vehicle. Unlike a regular balloon, the super pressure balloon has heavy electronics on its top. For the super pressure balloon to be inflated, a small balloon, called the tow balloon, is inflated first. The tow balloon lifts up the top of the super pressure balloon so that the super pressure balloon can be inflated. Once the super pressure balloon is inflated and the winds are just right, it gets released and floats up over the launch vehicle until it’s directly above the payload. (Usually the launch vehicle has to do some maneuvering to get directly under the balloon, as the winds are never quite perfect.) At this point, the payload is released and the whole system keeps floating up.

The first reason that we need such perfect weather is the tow balloon. If there’s too much wind, it’s difficult to keep the tow balloon directly above the super pressure balloon (this is an issue we ran into once last year–again, see Carolyn’s earlier post). Because of the added complication of the tow balloon, the wind has to be extremely low to launch a super pressure balloon: less than ~5 knots.

Another reason for the stringent launch conditions is that we’re launching at a populated airport. This launch site is very different from the isolated long duration balloon base outside McMurdo in Antarctica. Because of all the stuff at the airport, we can only launch the balloon along the runway, which means that the wind can only blow in two directions (along the runway both ways). So as well as needing extremely low wind, we need the wind to be in a very specific direction.

That’s why it’s more than just needing a nice day. We really need a perfect day. It’s been beautiful out today, and has been many days in the past two weeks, but not launch condition beautiful. If we were flying on a regular balloon and / or launching from a totally isolated spot, we would have more launch opportunities and maybe we would have launched already. But hopefully the super pressure will pay off with a long (100 day?!) flight, and I’d much rather be stuck here than in Antarctica! (I can’t speak for the rest of the team, but I bet most of them would agree.) And so, we wait.

While waiting, we’ve been fine tuning some analysis software and taking tons of calibration data. We’ve taken some half days, during which we’ve caught up on sleep, enjoyed the lake, and gone wine tasting. The arts and crafts have come out: Carolyn’s been cross stitching a picture of a moon and I’ve been doing some watercolor painting. We saw a cute New Zealand-made movie, Hunt for the Wilderpeople, at the local movie theater (there are couches instead of regular seats and they sell hot cookies at intermission). There’s talk of a possible helicopter trip in the next couple of days. Even so, we’re all hoping to launch soon (especially COSI itself, who is claiming boredom on its twitter feed).

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