The remaining contestants are nearly at the end but now they need to fight for their place in the final.
Tonight they face a survival test aimed to reveal weakness in the group, they must abseil down a 30-metre sheer cliff face.
Chris Hadfield and the panel are joined by two guest experts for probing interviews to grill the candidates on whether they have what it takes. Those who make it through this stage head off to the Kennedy Space Centre in Florida and carry out a spacewalk dive in an underwater marine lab.
Astronauts? Do You Have What It Takes, Sunday, 8 pm – BBC Two