The last launch attempt was tough. We got so close. Closer than most of us on COSI have ever been to launching a payload that we have worked on. In fact, we got past a point that CSBF said there was no going back from, but then the situation turned a bit dire and we had to back off.
As mentioned many times before, COSI is flying on the super pressure balloon. We’re the first science flight on this type of balloon (although, they’ve flown a science flight on a predecessor many years ago). The super pressure balloon could be the next best thing to happen to scientific ballooning; it promises 100 day flights, which means you get that much closer to mimicking a satellite for a small fraction of the cost. The success of the COSI/SPB flight this season is somewhat pivotal for the SPB progress in the world of science.
But, there’s a catch. Not only do these balloon cost a couple million dollars each, but they are extremely delicate and thus difficult to launch. Looking back at past posts, I realize that we’ve never really described the launch procedure, so here it goes (this is SPB specific).
The total time dedicated to preparing to launch is about 8 hours. First, the science team and the CSBF electronics group does their pre-flight checkout. We visually inspect all of the connections on the gondola, we put up a radioactive source to check if our detector lines widths look good, we send commands through each of our telemetry links… we pretty much check every aspect of our system to make sure it’s working as expected. We’ve done this a few times now so it takes just under an hour to go though the 70 item on the list. Chris Field works in parallel checking the SIP (Science Instrument Package), the termination electronics, the batteries and solar power and a lot of other things that I don’t know about.
After we’ve gone through our respective lists, we inform the riggers that we’re ready to be lifted. We get help from the riggers to roll the gondola out the door of our weatherport and out onto the porch. They come over with the launch vehicle, The Boss, and proceed to pick us up. We end up sitting at the end of the weatherport driveway for about another hour while the parachute is hooked up, the termination is tested, and while we check the rest of our telemetry links (the openport iridium link doesn’t work indoors). Then, we’re ready to be moved to the launch pad (this is where we’re currently at while I write this post. Clio is blogging live about the current launch attempt, but we’re on a weather hold for the moment…).
The Boss starts the slow trudge out to middle of the perfectly groomed launch pad, which has been kept in pristine condition by Fleet Ops here in McMurdo. At this point, the CSBF weather guy, Chris Schwantes, has decided which direction the winds will be consistently coming from and thus has chosen the proper direction to lay out the balloon. The balloon and parachute are laid out behind the launch vehicle upwind of the payload so that once the balloon is inflated and released it will sail up to position itself about 600 ft above the payload.
The laying out of the balloon isn’t so simple. This thing is huge. It measures just under 400 ft in diameter once it’s completely inflated at float. It’s stored in a box where the combined weight is 9000 lbs. The balloon itself is only 1.5 mil thick and weighs 5000 lbs. Taking the balloon out of the box is difficult enough, putting the balloon back in the box (in the event of a scrubbed launch attempt) is even crazier. It’s actually a rule at CSBF: super pressure balloons cannot go back in their box. So when that balloon was laid out last Friday during out last launch attempt, CSBF told us that this was it, there was no going back. We were thrilled.
An added complication of the super pressure balloon is the electronics and valves contained in the top of the balloon. This weight makes this inflation process more involved. A smaller balloon, referred to as the tow balloon, is inflated first and attached to the top of the super pressure for the duration of the inflation. Once the inflation of the tow balloon is compete, then the inflation of the main balloon can begin. The balloon is held down on a spool during the inflation, and only once the inflation is complete and the winds are calm and everything else is right, the balloon will be released from the spool and lift itself above the launch vehicle. Because the winds are never quite perfect, the Boss will have to be maneuvered to stay underneath the balloon before the release of the gondola. Then, up up and away!
Our launch attempt last week got us all the way up to the inflation of the tow balloon. Unfortunately, the winds had changed direction during the few hours that it took to get the launch vehicle, parachute and balloon in position. By the time the tow balloon was inflated, there were cross winds with gusts up to 8 or 9 kts (3-4 kts average is the max for our super pressure launch). The four riggers who were holding the tow balloon in place were doing all they could just to not have it blow away. Seeing the wind direction, the magnitude of the gusts, and the difficulty in just having the tow balloon barely stable, CSBF made the decision that it would be too risky to try and inflate the super pressure. The launch was called off and the tow balloon was released.
At this point, we didn’t really know the significance of the scrubbed launch. The balloon was out, but the launch was cancelled. If we were to take what CSBF said earlier with all seriousness, that would mean that the super pressure balloon was done with (we have no spare). Within the hour, most things were pretty much cleared up. CSBF decided that it would be worth the effort to try and put the balloon back in the box (they got permission from headquarters to attempt to launch with the same balloon again), so not all was lost. It took 10 riggers over an hour of strenuous, delicate work to get the 5000 lbs balloon back. Everyone is crossing their fingers that nothing was damaged in the process and we’re going to go ahead and try to launch again. Today is the day.
If you have a no-wind dance, now’s the time to get moving.