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How SpaceX Used Tin Snips to Fix a Rocket Just Days Before Launch

No rocket launch is free of complications. With countless moving parts and harsh operating environments, rockets are miracles of human engineering sprinkled with a bit of luck. Something can always go wrong – especially for young companies and new rockets. With SpaceX’s first rocket, the Falcon 1, faults were discovered too late. Its first three launches ended in rapid unplanned disassemblies.

Luckily, Falcon 9 was a different story. On the new rocket’s second mission, SpaceX would launch the first complete Dragon capsule, a few cubesats, and a wheel of cheese. Needless to say, the launch was important. But just days before liftoff, SpaceX noticed a fault.

A fault that involves tin snips, a few cracks, and the laws of physics.

wheel of cheese inside an aluminum sealed container with a movie poster on the lid

I'd tell you which movie it's from, but it's Top Secret!

There were cracks in the second stage engine nozzle - the 9 ft. long, 8 ft. diameter niobium nozzle extension that guides the exhaust gases out of the rocket to produce thrust. According to SpaceX, the cracks weren’t a serious problem. Because the cracks were near the nozzle’s exit, they wouldn’t experience much stress. However, SpaceX decided not to risk it. They worked to fix the problem.

The expected fix was to completely replace the engine bell - a time consuming but proven solution. SpaceX, displaying its unconventional nature, didn’t do this. A company that sends wheels of cheese to space could find a better solution. They did. Elon Musk proposed just cutting off the cracked portion like a fingernail. Since the cracked nozzle portion was thinner than the average fingernail, the analogy was somewhat applicable. However, most humans don’t grow fingernails made of a niobium-alloy that can withstand steel-boiling temperatures.

original falcon 9 second stage with interior and nozzle extension showing

Rocketry is typically a cautious field that normally follows lengthy manuals, so a proposal like this was met with skepticism. Then the gathered workers started thinking about it. They went through every subsystem analyzing how trimming the engine bell would affect the rocket, and every person agreed the change was acceptable. The only drawbacks would be decreased thrust and engine efficiency. Yet, since the payloads were relatively light, the rocket still would have enough thrust to fulfill the mission. Snipping the rocket nozzle would work - the Falcon 9 second stage would get a manicure.

To do the job, they flew an aviophobic technician from California to Cape Canaveral. He crawled into the interstage where the second stage nozzle rests and used ordinary tin snips to trim the nozzle. The rocket flew successfully the next day.

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All told, the repair process took two days - a much shorter turnaround than a full replacement. And in perfect SpaceX fashion, the Dragon with a belly full of cheese and cubesats launched to orbit. It’s amazing that science allows us to tell stories like this outside of science fiction. A few two legged creatures with fancy calculators used a household tool to fix a complex piece of metal - all of this to launch a few conductive bits and a wheel of cheese to space.

Isn't science fantastic?

If you'd like to learn more about how the exit area affects rocket thrust, then check out this interactive graph.

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