How long can you survive in a standard space suit in space?

Answer 1

Probably the rate limiting step is going to be your oxygen supply. Does this stranded astronaut have an umbilical supplying him/her with oxygen? Is the astronaut getting oxygen only from their backpack (PLSS)? Often these portable life support systems will supply fresh oxygen and use lithium hydroxide to scrub the exhaled carbon dioxide while recycling the suit's atmosphere. Another consideration is the amount of activity the astronaut is doing. The more active they are, the faster they will burn through their oxygen supplies. So, lets say there are two astronauts stranded on the moon. One is very active and is burning through the oxygen and lithium in his PLSS, he might last 4-6 hours. Let's say his comrade is laying very still--almost sleeping--trying to conserve his oxygen and lithium hydroxide. He might last 6-8 hours. There is an issue of electricity and water used to control the suit's temperature. If the astronauts kept themselves in the shadows (of the Lunar Module) they could save cooling water and electricity. Still, the amount of oxygen astronauts bring with them into space is finite. If they are stranded, they will eventually run out. In a larger space station, it would be possible to grow enough plants to PRODUCE enough oxygen to supply the astronauts with an ~unlimited supply of oxygen. However, if the astronauts became dependent on these plants for oxygen production, any problem with the plants (say, over exposure to sun light, under watering, etc...), could doom the crew.