On Twitter Friday, Elon Musk announced that version two of his plan to get people to Mars will address what he calls the “most fundamental flaw” in his first plan: how he’s going to pay for it.

Musk’s concept for sending people to Mars, known as SpaceX’s Interplanetary Transport System, has been knocking around for a while now. At the International Astronautical Congress in Guadalajara, Mexico last September, Musk first proposed his idea of a future in which the money from someone selling their home would be enough to finance a relocation to the red planet.

This month, Musk penned a paper for the journal New Space delving further into how the ITS would actually work, and how it would facilitate a million people moving to Mars. Putting technology and habitable surfaces aside, the sheer cost of transporting people to Mars would be theoretically huge; something Musk points out in his paper.

“You cannot create a self sustaining civilization if the ticket price is $10 billion per person. … If we can get the cost of moving to Mars to be roughly equivalent to a median house price in the United States, which is around $200,000, then I think the probability of establishing a self-sustaining civilization is very high.

It is a bit tricky because we have to figure out how to improve the cost of trips to Mars by five million percent.”

A big way Musk envisions we’ll afford to get there is through more efficient and reusable rockets, which he also details in his paper. But apparently that’s not a good enough explanation. The CEO tweeted Friday he will provide more details about how SpaceX will pay to develop and operate their giant rockets very soon.

Like, really soon, according to Musk.

SpaceX’s Falcon 9 rockets are making more and more frequent trips for NASA and the company is continuing to actively develop its reusable technology to make them even more efficient. The more details we can get from Musk about how it’s all going to be payed for down the road, the more legitimate our future as an interplanetary species begins to look.

Photos via Getty Images / Pascal Le Segretain