Astronauts, and indeed even fighter-jet pilots, wear G-suits - sometimes “Anti-G Suits” - where a network of pipes cover the surface, and are pressurised, constricting the body. This stops blood from moving away from the brain, thus preventing G-LOC. The redoubtable Calculus seems to have neglected giving his crew such suits, so they were likely to black out.
There is a description of a Canadian pilot’s suit
here, which protects up to 7.5G. An astronaut’s suit would be made to withstand more.
You can easily withstand brief bursts of G-force if you are in reasonable health, even if you aren’t a trained astronaut or pilot; there are roller-coasters and thrill rides which pull quite severe G-force. The “Incredible Hulk” at Universal Islands of Adventure in Florida pulls 4G, and the Aerosmith Rock‘n’Roller Coaster at the Disney Studio Parks in Florida and Paris pull 5G (at 0-58 miles per hour in 2.3 seconds…