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Lost in space
It set me wondering when that female astronaut lost her tool box while making repairs to the outside of the ISS. I notice now that when doing a spacewalk they attach themselves with a restraining hook.
What would happen if the astronaut was not attached and wandered off like the toolbox. Would they easily be able by their own efforts to get back to the spaceship?
What would happen if the astronaut was not attached and wandered off like the toolbox. Would they easily be able by their own efforts to get back to the spaceship?
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1 All spacewalkers are connected to their work station by two tethers. This allows for the astronaut always to be connected by one tether while the other is repositioned.
2 The flexible arms attached to the ISS and to the shuttle are frequently used as additional workstations allowing the astronauts to use foot restraints to make moving and working simpler.
3 While the shuttle is attached to the ISS all spacewalkers must use the SAFER backpack system to give them a capacity for independent flight. The fuel supply is limited (around 13 minutes at normal usage rates) but should permit an untethered astronaut to regain the station should they become detatched.
4 Eltelioni's idea of 'pushing' themselves by throwing something in the opposite direction would work. Unfortunately they aren't carrying a lot that they might consider as dispensible. It is also surprisingly difficult to make this work. You have to line the item up with your centre of gravity and push "through" your CoG. If you don't then only a proportion of the effect will be to push you in the right direction and the remainder will result in your rotating about your CoG. Rapid spinning will tend to disorientate you and make a second attempt next to impossible.
2 The flexible arms attached to the ISS and to the shuttle are frequently used as additional workstations allowing the astronauts to use foot restraints to make moving and working simpler.
3 While the shuttle is attached to the ISS all spacewalkers must use the SAFER backpack system to give them a capacity for independent flight. The fuel supply is limited (around 13 minutes at normal usage rates) but should permit an untethered astronaut to regain the station should they become detatched.
4 Eltelioni's idea of 'pushing' themselves by throwing something in the opposite direction would work. Unfortunately they aren't carrying a lot that they might consider as dispensible. It is also surprisingly difficult to make this work. You have to line the item up with your centre of gravity and push "through" your CoG. If you don't then only a proportion of the effect will be to push you in the right direction and the remainder will result in your rotating about your CoG. Rapid spinning will tend to disorientate you and make a second attempt next to impossible.
Ok, the questioner asked how an untethered astronaut could get back "by their own efforts", so we can forget tethers, booms, rocket packs or any assistance from the crew of the space station. I realise now that my earlier answer was simplistic. The best course of action depends on the direction the astronaut is moving relative to the space station and how fast. Assuming the mishap was similar to the loss of the toolbox, then the astronaut is moving away as a result of their own action and so their velocity relative to the space station is small.
Case 1: If they have been propelled directly towards the Earth or directly away from the Earth then they will move into a more elliptical orbit which will cross the orbit of the space station 4 times per rotation around the Earth. Given that the orbits are only slightly different and the space station is large, the astronaut and the space station will meet at the intersection points (at least on the first few times round), so the astronaut just has to wait then grab hold at the next intersection.
Case 2: If they have been propelled "sideways", that is perpendicular to the space station's orbit but maintaining the same height above the Earth, then the orbits will cross twice per rotation around the Earth. Again, they just need to grab hold at the next intersection.
(continued in next post)
Case 1: If they have been propelled directly towards the Earth or directly away from the Earth then they will move into a more elliptical orbit which will cross the orbit of the space station 4 times per rotation around the Earth. Given that the orbits are only slightly different and the space station is large, the astronaut and the space station will meet at the intersection points (at least on the first few times round), so the astronaut just has to wait then grab hold at the next intersection.
Case 2: If they have been propelled "sideways", that is perpendicular to the space station's orbit but maintaining the same height above the Earth, then the orbits will cross twice per rotation around the Earth. Again, they just need to grab hold at the next intersection.
(continued in next post)
(continued from previous post)
Case 3: If they have been propelled directly forwards (or backwards) then they are moving faster (or slower) than the space station so will move into a higher (or lower) orbit. In that case they have to lose (or gain) orbital speed by throwing an object forwards (or backwards) along their path. Note that they should not throw the object in a line away from the space station, that will just confuse things.
In practice their motion is likely to be a combination of the above 3 cases, so the astronaut needs to think carefully before taking any action.
If the astronaut has been propelled with a lot of force, by an explosion for example, then it gets much trickier. In the first 2 cases, the orbits will cross but the astronaut and the space station may not reach the intersection points simultaneously for many rotations around the Earth and, when they do, they will have relative velocity similar to their initial relative velocity, so it is going to hurt. For the 3rd case they are unlikely to be able to impart enough force to an object to adjust their orbital speed sufficiently.
Case 3: If they have been propelled directly forwards (or backwards) then they are moving faster (or slower) than the space station so will move into a higher (or lower) orbit. In that case they have to lose (or gain) orbital speed by throwing an object forwards (or backwards) along their path. Note that they should not throw the object in a line away from the space station, that will just confuse things.
In practice their motion is likely to be a combination of the above 3 cases, so the astronaut needs to think carefully before taking any action.
If the astronaut has been propelled with a lot of force, by an explosion for example, then it gets much trickier. In the first 2 cases, the orbits will cross but the astronaut and the space station may not reach the intersection points simultaneously for many rotations around the Earth and, when they do, they will have relative velocity similar to their initial relative velocity, so it is going to hurt. For the 3rd case they are unlikely to be able to impart enough force to an object to adjust their orbital speed sufficiently.
LOL wildwood.
Using eltelioni's last scenario where the astronaut is flung away by explosion, would he travel at the same speed he gained in the explosion or would he eventually slow down?
How far into space would he likely get before dying of lack of water? Or say he had a bottle of Evian with him, how far would he get before dying of starvation? Can you imagine the things he'd see?!
Using eltelioni's last scenario where the astronaut is flung away by explosion, would he travel at the same speed he gained in the explosion or would he eventually slow down?
How far into space would he likely get before dying of lack of water? Or say he had a bottle of Evian with him, how far would he get before dying of starvation? Can you imagine the things he'd see?!
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I assumed the velocity relative to the space station is small. In cases 1 & 2, both the space station and the astronaut are moving very quickly but in very similar orbits. The orbital period of the space station is about 90 minutes, so the astronaut would not have to wait long for the orbits to intersect.
Based on this video I estimate the tool bag velocity (relative to the ISS) at about one foot per second, easily well in excess of 100 times escape velocity of the ISS. It is highly unlikely that it will ever be seen at the space station or by anyone else again . . .
Enter your location here for your chance to observe an ISS Tool Bag fly bye.
Enter your location here for your chance to observe an ISS Tool Bag fly bye.
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