SpaceX CEO Elon Musk has lifted the lid on why reusing Falcon 9 boosters makes economic sense in the long term. //

This week, NASASpaceflight reporter Michael Baylor explained on Twitter that United Launch Alliance, another player in the new space race, has claimed that a company needs to reuse a rocket 10 times for the economics to make sense. SpaceX, Baylor noted, is up to six landings with a single booster.

In response, Musk wrote:

"Payload reduction due to reusability of booster & fairing is <40% for F9 & recovery & refurb is <10%, so you’re roughly even with 2 flights, definitely ahead with 3." //

In 2018, ahead of a Falcon 9 Block 5 launch, Musk broke down the costs again. The boost stage, he stated, costs around 60 percent of the total costs, with the upper stage 20 percent, the fairing 10 percent, and the final 10 percent associated with the launch itself. This, CNBC noted, would instead place the cost of a booster at around $37 million. //

In terms of the marginal costs, the costs associated with producing just one extra rocket, Musk also recently shed some further light on the figures. In an interview with Aviation Week in May, Musk listed the marginal cost of a Falcon 9 at $15 million in the best case. He also listed the cost of refurbishing a booster at $1 million. This would fit with Musk's most recent claim that the costs of refurbishment make up less than 10 percent of the booster costs. //

"I don’t want be cavalier, but there isn’t an obvious limit. 100+ flights are possible. Some parts will need to be replaced or upgraded. Cleaning all 9 Merlin [Falcon 9 engine] turbines is difficult. Raptor [the engine for the upcoming Starship] is way easier in this regard, despite being a far more complex engine." //

SpaceX's rocket reusability program is a long-term investment, and it can be hard to quantify the overall savings due to the myriad of factors at play. Musk noted in March 2017 that the company had spent over $1 billion in reusable launch technologies, which meant the firm also needs to recoup the development costs from the reuse program rather than directly passing on those savings to the consumer.