https://www.cnbc.com/2017/10/17/astronaut-scott-kelly-says-dont-doubt-elon-musk.html

Elon Musk is racing to land SpaceX on Mars in five years, a vision he unveiled late last month at the 2017 International Astronautical Congress.

One man not among Musk's critics is Scott Kelly, a retired astronaut who set the record in 2015 for total accumulated days in space, during the single longest mission by an American.