The survival needs of astronauts in space depend on the amount of time in question, but for standard, short missions, they require protection against the frigid temperatures and protection from solar glare and the vacuum. These needs are particularly pressing during spacewalks, when astronauts are outside their ships. As explained by NASA, spacesuits are sophisticated protective garments with oxygen tanks, carbon dioxide scrubbers, active fingertip heaters and other protective measures.
There are many hazards in space, not all of which can be protected against. Anything in space has a small but real risk of being struck by a tiny meteorite traveling thousands of miles per hour, which would penetrate any materials currently used. This is more of a risk the further a ship gets from earth. Another risk that increases with distance is radiation. The Earth's atmosphere and magnetic field protect against cosmic rays and many stellar forms of radiation. Current technologies do not do much to protect astronauts from this risk, which accumulates the longer astronauts are in space.
Another long-term risk of space travel is bone and muscle degradation from weightlessness. Astronauts on the International Space Station do exercises to help compensate, but these are only partially effective. Future technologies may include inertia-based simulated gravity to mitigate this risk.