An engineer worthy of the title would always test an alien environment on another mammal first before risking human lives. Quoting: Skeptic the First
Actually, NASA did this in early July 1969--with horrifying results:
[link to lis.arc.nasa.gov
The last mission in the U.S. biosatellite program was Biosatellite III, launched on June 28, 1969. The intent had been to fly a pigtailed monkey in Earth-orbit for 30 days. However, after only 8.8 days in orbit, the mission was terminated because of the monkey's deteriorating health.
When it became evident that the primate's condition was continuing to decline, the biosatellite was recalled. Immediately after the biosatellite was recovered, attempts were made to revive the primate but there was no response to remedial measures.
The flight subject died about eight hours after the capsule was recovered. The acute cause of death was ventricular fibrillation. At the time of death, body weight was 4.4 kg. Weight loss may have been due to the marginally palatable food pellets that had to be used to accommodate experimental requirements. Marked dehydration was evident. The cause of death is still controversial. At the time it was speculated that the changes noted in the animal were an effect of microgravity alone
In other words, the experiment convinced NASA that microgravity was itself fatal to mammals. (Whether or not this later turned out to be true is irrelevant here.)
So NASA immediately sends up humans into the same environment? Would any good engineer do such a thing? Would a celebrity "astronaut" agree to it?