The last mission carried all the equipment necessary for manned flight and tested life-support systems.

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To that end, NASA will spend billions of dollars developing new engines, propellants, life-support systems and the like.

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Node 3, also known as Tranquility, will house the station's core life-support systems.

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It will develop orbiting fuel depots, rendezvous-and-docking technologies, advanced life-support systems that recycle all of their materials, and better motors for spacecraft.

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They have to be kept alive by expensive and heavy life-support systems, and their relatives tend to make a fuss if, despite these, they get killed.

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SpaceX is eyeing this business as well, and is developing the critical life-support and safety systems that would turn Dragon into a human-rated vehicle.

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These activities could include demonstrations of new robots, inflatable modules in which to live or grow food ("greenhouses"), new life-support technologies, radiation protection systems, communications and sensor technologies, novel telemedicine approaches - anything that would be needed by astronauts on a self-sufficient mission far from Earth.

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