Over the weekend, SpaceX successfully launched their 5th (fifth!) Falcon 9 and Dragon capsule to resupply the ISS. Company news with some photos is here.
This was the primary and most important criteria for the mission–to resupply the International Space Station. But of course, I and millions of other people were eager to learn the results of their attempt to land the first stage on a floating ocean platform.
According to Elon Musk, the control fins ran out of hydraulic fluid just before touchdown. This fluid is what drives the control mechanisms–changing their position to direct the rocket thrust in the right direction. I don’t know what their failure and safety modes directed would happen next (probably cutting all signals to use the rockets). But the end result was a hard landing. Or splash–I’m not sure which yet, depending on how close to the platform they actually were.
This situation brings me back to graduate school in Penn State University. My advisor, Dr. Mark Maughmer, used a very descriptive and memorable analogy to describe the science and art of aerospace design. (He is a world authority on winglet design, by the way. The evolution of sailplanes and then commercial aircraft to use winglets as a standard configuration item can be traced to his efforts. He also flies sailplanes and plays a mean game of racquetball.)
Anyhoo…aerospace design is a constant challenge of balancing and optimizing a large number of constraints, variables, and objectives. He describes it as trying to squeeze a lump of JELL-O in your hands. Squeeze too hard in one area, and some of it will squirt out on the other side. Just when you think you have a stable, clean solution…oops, some of it starts leaking out somewhere.
For SpaceX on this latest flight, running out of hydraulic fluid was their bit of JELL-O that oozed out first. (Making this more complicated, this JELL-O can be oozing in or out to cause a problem. Because in this case it wasn’t too much hydraulic fluid, it was too little.)
In this sense, any complex engineering and design project is like squeezing JELL-O. It’s not just in rocket science.
We can even think bigger than that. Every time I hear the famous line from Forest Gump, I want to say, “No, life isn’t like a box of chocolates. It’s like squeezing JELL-O!”
One geeky technical term and discipline for this, BTW, is MDO: Multidisciplinary Design Optimization. Maybe that’s your calling in aerospace.
Put this mental image in your head the next time you tackle a complex problem and you’ll be thinking (and working) like a rocket scientist.
My understanding of the hydraulic system is that it uses kerosene from the fuel supply to run the affected actuators. In this case, the margin of fuel for hydraulic purposes was exhausted shortly before final landing, leading to a loss of control. The speculation I’ve seen is that weather conditions at the landing barge were not very good, and the system had to fiddle around more trying to land.
Hopefully, the calculation of the jello for the next flight leaves more margin.
Thanks for more details Craig! I need to provide a big caveat and disclaimer when relying on late-breaking news items. And I know details and nuances often get misreported (from personal experience). Thanks for adding more info for me and the other readers!
Craig, I realized after I wrote this post yesterday that hydraulic fluid can’t “run out.” It operates in a closed system. It won’t run out unless there is a hydraulic system leak, which none of the press reports or company reports mentioned. So what you say makes sense to me–the fuel source that drives the hydraulic system ran out.
BTW, Robert Zimmerman’s blog Behind the Black has a more detailed account of the landing. It was almost at touchdown apparently! It hit the platform. So close…it’s not a complete success but really amazing. And promising for their next attempt.
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