While great efforts necessarily go into improving the machinery of flight, it is sometimes worth remembering there remains much to be learned about the most important component of all: the human crew.
Speaking to a packed house on 7 February at the Royal Aeronautical Society in London about the training regime he hopes will one day earn him selection for an International Space Station mission, European Space Agency astronaut Tim Peake was asked whether, 50 years into the space age, we fully understand the physiological effects of weightlessness. His answer surprised the crowd.
Just last year, he said, it became evident that about 20% of men who make long-duration space flights - of six months or more - suffer permanent eyesight degradation. That is, after returning to Earth they remain short-sighted and may need to wear glasses or undergo corrective laser surgery.
The theory being considered is that in microgravity, blood and fluid pressure in the legs is necessarily lower than on the ground, and that pressure is distributed elsewhere; astronauts on the ISS tend to have puffy faces, says Peake, and it may be the case that pressure on the retinas flattens them, in some cases permanently. Women are not affected, it appears.
This discovery begs the question, what other effects of spaceflight have we yet to encounter? A typical stay on the ISS is six months and the spaceflight endurance record is 437 days, set on the Russian station, Mir. If a mission to Mars is ever undertaken, the crew would be away for a minimum of 18 months.
Peake, a UK army major who still flies Apache helicopters for the Territorial Army, speculated that genetic screening may become a necessary part of astronaut selection.