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| | Office of Space Operations |
 | | When humans start out into deep space, e.g., on expeditions to Mars, their ships will carry elaborate health maintenance stations and one or more of the crewmembers will be medically trained because a quick return to Earth would then not be possible. |
 | | To navigate and maneuver in space, our three coordinates are usually given the designation X, Y and Z. Then, everyone involved agrees on a "reference system", i.e., a location and orientation of the coordinate system from which all measurements and determinations are universally made. |
 | | In the longer run, too, the Space Station is necessary as a "spaceport" for more advanced space missions by humans out into deep space, a staging point, springboard and launch platform moving at a speed (23,000 feet per second) which is already close to what it takes to embark on interplanetary flights (37,000 ft/sec). |
| www.hq.nasa.gov /osf/qanda.html (4051 words) |
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