Rocks and Stars with Amy: It’s Time to Go
Now that we are just days from launch (wow!), the team is making final decisions and preparations. We’ve just held our Flight Readiness Review, at which the final commitment to launch was made by NASA, the United Launch Alliance (the rocket folks) and the WISE project. It turns out that fueling our Delta II rocket’s second stage engine is an irreversible process — once we fuel the second stage, we have 34 days to launch the rocket. If we don’t launch within 34 days of fueling it, we have to replace the second stage completely — and that would mean taking WISE off the rocket. So we needed to be really sure that we were “go for launch” before we decided to fuel up the second stage. That is now done, and we are in the process of putting the final finishing touches on cooling down our solid hydrogen tanks.
These last few weeks and days before launch require a lot of flexibility of the team, since the schedule can change on a dime. There are about a million things having nothing to do with the launch vehicle or the spacecraft that can delay a launch — winds, too much fog, too many clouds, lightning and even something as mundane as a fishing boat or aircraft straying into the “keepout” zone that’s established around the launch site. You would think that the prospect of running into a giant, 330,000-pound rocket loaded with fuel would be enough to make people move out of the way, but sometimes they don’t seem to get the message! Any of these items is enough to scrub a launch attempt.
But that’s why we’ve built in the ability to make two consecutive launch attempts with WISE, separated by 24 hours. We get two tries. After that, our tank full of frozen hydrogen starts to warm up too much, and it takes two days for us to cool it back down. To keep the tank of frozen hydrogen a frosty 7 degrees above absolute zero (minus 447 Fahrenheit), we circulate an even colder refrigerant, liquid helium, around the outside of the tank. But the process of re-cooling takes two days; we have to hook all the hoses back up, cool everything down, then disconnect the hoses again before the next launch attempt.
So we have to be flexible. We’ve all put our lives on hold for the duration, since we have to be ready for anything that happens. Meanwhile, I’ve frantically tried to take care of stuff like cleaning the house and laying in supplies, because once WISE launches, things will go into overdrive. Needless to say, our families have all been very patient with us!