Private flights may make space station more expensive

A report from NASA's internal auditor, inspector general Paul Martin, says the space agency has underestimated the cost of keeping the International Space Station running until 2024. In particular, buying flights to the ISS from private companies rather than Russia is expected to increase costs.

NASA expects its annual spend on the ISS to increase from $3 billion to $4 billion over the next 10 years, with the largest increase coming from transportation costs.