Saturday, May 19, 2012

Chasing the Dragon

[9:19 PM, 5/17/2012] Provided that nothing silly happens, in the wee hours on Saturday morning SpaceX will be launching a Falcon 9 rocket carrying a Dragon cargo spacecraft up to a rendezvous with the International Space Station. My intent is to live-blog the launch, starting at about 3:00 AM or so on Saturday morning. Unless my alarm doesn't wake me up. Or, unless something happens and the launch is cancelled.

It's a non-trivial possibility. The launch window is very tight. The Dragon doesn't have much in the way of out-of-plane fuel reserves, so they have to launch straight into the right orbital inclination. Which means they have one chance to get this right.

I'm fairly confident that they will. Until then, some music while we wait:

[5:33 PM, 5/18/2012] For those of you following along from home, there's a press release from SpaceX here. (Hat tip: Next Big Future.)

[7:16 PM, 5/18/2012] So far, so good. For those tuning in live overnight, SpaceX will probably host a live feed here. Until then, this is what we expect to start happening early tomorrow morning:

[3:13 AM, 5/19/2012] OK, we're up and running. The webcast will be here at about 3:15 or so.

[3:19 AM, 5/19/2012] Nothing out of the ordinary so far. Weather looks good. The initial indications from the webcast are good. According to the timeline, the vehicle was powered on at about 8:30 PM last night. Just before midnight, they began fueling the rocket, which was complete by about 12:30 AM or so. Now, they're running down the clock to the planned 4:55:26 AM EDT launch. That's 3:55:26 AM CDT, or just about 35 minutes from now.

[3:27 AM, 5/19/2012] T-30 minutes and counting. Looks good so far!

[3:28 AM, 5/19/2012] Ha. "Instantaneous launch window," indeed. As I said earlier, Dragon doesn't carry much in the way of out-of-plane capability. They get one chance to launch. If the weather doesn't co-operate, or if there's a hardware glitch, they'll have to scrub, and get a new date from NASA. Which means, by 4:45, they'll either have a go for launch, or an order to start off-loading their fuel.

[3:31 AM, 5/19/2012] And that's a good point ... being the wee hours of the morning, the on-board camera video probably won't be very fascinating once we get up away from the pad. We'll see about that when it happens.

[3:41 AM, 5/19/2012] Some of you might be wondering why rendezvous isn't until Flight Day 4. That's a pretty good question. First-orbit rendezvous isn't impossible, but it imposes so many constraints on your launch time that it's just about never done. They did it on Gemini 11. But you not only have to inject into the right orbital plane, but the target has to be exactly in the right place for you to slide up right alongside it right after orbital insertion. That just about never happens. You get one launch window per day as it is. You'd wait months, if not years, for a direct-ascent rendezvous. So, what you do is inject into an orbit slightly lower than your target, and let the "magic" of differing orbital rates "walk" your way around into proximity over the course of two or three days. Which is why I say that spaceflight is a lot like baseball, in that the participants spend most of their time waiting for something interesting to happen...

[3:43 AM, 5/19/2012] T-15 minutes and counting.

[3:43 AM, 5/19/2012] Latest poll of flight controllers is a GO for launch.

[3:47 AM, 5/19/2012] GO for terminal count. Falcon 9 auto-sequence start. T-10 and counting.

[3:53 AM, 5/19/2012] T-5 minutes and counting. Vehicle is venting LOX. I think I heard that Falcon 9 is on internal power?

[3:53 AM, 5/19/2012] No, I misheard. Now it's on internal power.

[3:54 AM, 5/19/2012] T-4 minutes and counting.

[3:55 AM, 5/19/2012] Interestingly, it looks like they don't switch all of the systems on internal power all at once. Probably a good idea. T-3 minutes and counting.

[3:56 AM, 5/19/2012] Launch Director is GO for launch. T-2 minutes and counting.

[3:57 AM, 5/19/2012] T-1 minute and counting.

[3:58 AM, 5/19/2012] And, terminal launch abort. Why, not exactly clear just yet.

[4:04AM, 5/19/2012] There was a shut-down just after ignition. Which means that, given the tight launch window, no launch today. What's happening on the live feed now is that the launch control team is executing the steps required to "safe" the vehicle, and begin off-loading the fuel. And, I just heard that the abort was due to Engine 5 chamber pressure high. That's a good thing to know while the vehicle is still locked down to the pad, rather than in-flight. And with that, I'm back to bed. I'll check back in later to see if there's more information.

[6:30 AM, 5/19/2012] In hindsight, slamming down an energy drink at 3AM was probably a grievous error. That said, we've got a few updates. First, to expand on what I said above at 4AM: the Falcon 9 launch procedure is to bring the engines up to full thrust, perform a complete engine checkout, then release the vehicle for flight. If anything funky happens during the checkout, the on-board controller automatically shuts the engines off. This way, you know that you've got nine healthy engines when you leap up off the pad. The fact that it shut itself down is a feature, not a bug. We don't know yet exactly why Engine 5 had a slightly high combustion chamber pressure. The actual pressure value might have been just fine, but the software limits had been exceeded. Or that might have been a precursor of something more serious. Something that you don't want to find out about five miles up at Mach 2.

Elon Musk said that they'll "adjust the limits" and try again on Tuesday morning. Why Tuesday? Dunno. There are a lot of possible reasons, from weather forecasts to labor issues, but by far the most likely scenario is that you just can't offload the fuel, do a complete checkout on the vehicle, then re-load the fuel in just 24 hours. Or even 48 hours. Tuesday morning isn't official yet, they'll have to get buy-in from range safety and everyone else, but that's the way to bet.

This is a hard, complicated business to be in. It really is rocket science. The amazing thing is that we can do it at all.

Anyway, no live-blog on Tuesday, since I have to report to my day gig. We'll keep our fingers crossed, though, and probably have a wrap-up report Tuesday evening if all goes well. Until then...

... just remember, it could have been worse.

[8:50 PM, 5/19/2012] And here's the final postscript: SpaceX engineers found a faulty check valve on the #5 engine, which they've replaced. The next attempt will be on Tuesday at 3:44 AM EDT, 2:44 AM Central.

[10:00 AM, 5/26/2012] Launch through docking continues here.