Re-using rockets is central to SpaceX’s plan to radically reduce the cost of space flight. A Falcon 9 mission is priced at about $60 million, with the rocket’s first stage making up about 3/4ths of launch costs. By contrast, Musk has estimated that fuel and other propellant only makes up about $200,000, or 0.3% of the cost of a mission. That means successful re-use could dramatically drop overall costs.

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That would give SpaceX a huge competitive advantage over other private rocket companies. It would also, as Musk has frequently reiterated, be key to enabling the colonization of Mars.

The only unknown in that plan is the cost and difficulty of refurbishing rockets for re-use. Because launches have such generally low fault tolerance, rockets will have to be brought back up to like-new condition to be safely reusable. That’s a big challenge because the trip back to Earth involves extremely high heat, as well as potential collision with space debris or meteorites. The closest thing to a reusable space flight system that has previously succeeded is the Space Shuttle program, which required several months of refurbishing work between launches.

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Falcon 9’s first stage, though, returns from lower altitudes than the Space Shuttle. This Stack Exchange thread includes some enlightening photos of the first-stage engines of a Falcon 9 clean and shiny before the launch, then blackened and soot-stained—but not noticeably battered—after recovery.

So maybe all SpaceX needs to get the CRS-8 rocket back up and running is a few thousand cans of Comet. If so, we could see the real culmination of their ambitious plans by this Fall.