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Ready, set ...

The 150-minute clock has started ticking on Armadillo Aerospace's fourth attempt to win $350,000 in the Northrop Grumman Lunar Lander Challenge. The past attempts to get the Mod rocket craft from Point A to Point B and back, as required to win the prize, have been plagued by rocket engine problems. But Armadillo has come up with yet another twist to address the problems.

"We changed our procedure a little bit to flush out the system," said Armadillo team member Russ Blink. Armadillo has had good luck getting the Mod to Point B - it's the return trip that's been difficult. This time around, the team will take more time to clear residual fuel out of the engine system by letting pressurized helium squirt through the main valves.

Blink thinks that's what led to the damaging hard start during the morning run.

"I looked up in there, and the engine was wet," he told me.

Unfortunately, that engine couldn't be repaired in time, but Armadillo took the same type of rocket engine from its Pixel craft and installed it on the Mod. Will all this do the trick? We'll know in two and a half hours.