3 ms·

I always kinda wonder how much wiggle it has. I mean, like, if you bounce off a wall, how much does the thing vibrate?

by IvyMike 12y ago

nialo 12y ago
This is actually a straightforward question to answer, I think: By conservation of momentum, the center of gravity of the entire ISS + astronaut system needs to stay on the same path before and after your wall bounce. So, the momentum change for the ISS is equal in magnitude but opposite in direction to the momentum change for the astronaut, and the velocity change will be the velocity change for the astronaut times astronaut mass/ISS mass Getting actual numbers to plug in left as an exercise for the reader.
- Thrymr 12y ago
  That doesn't tell you whether you will start the station oscillating in some mode of vibration. For that you'd need a model of the stiffness and structure of the station.
outworlder 12y ago
I thought wobbly stations were a Kerbal problem.
- TeMPOraL 12y ago
  Not really. In fact, Kerbals can just bruteforce the problem with boatloads of struts. But then again, we don't get to meet the Space Kraken.
sitharus 12y ago
Vibrations are a constant worry for the ISS. The structure is pretty stiff - each module is connected with a series of bolts (20 I think) and very stiff steel rings. One of the long term fatigue problems they have to worry about is the impact of space ship docking - the existing APAS-95 docking ports require a significant force to initiate mating which causes the whole structure to flex, especially the truss as it's perpendicular to most docking ports. NASA are planning to solve this with the low impact docking system (LIDS), but that's not going to be deployed until the Orion capsule flies, or perhaps the SpaceX crewed Dragon. Day-to-day all the exercise stations are mounted on special vibration reducing mounts, even the treadmill. Back in the Space Shuttle days there would be blackout periods for exercise to reduce the vibrations transmitted through the docking port to the shuttle. Space is a harsh mistress.

I always kinda wonder how much wiggle it has. I mean, like, if you bounce off a wall, how much does the thing vibrate?

by IvyMike 12y ago

I always kinda wonder how much wiggle it has. I mean, like, if you bounce off a wall, how much does the thing vibrate?

nialo 12y ago

This is actually a straightforward question to answer, I think: By conservation of momentum, the center of gravity of the entire ISS + astronaut system needs to stay on the same path before and after your wall bounce. So, the momentum change for the ISS is equal in magnitude but opposite in direction to the momentum change for the astronaut, and the velocity change will be the velocity change for the astronaut times astronaut mass/ISS mass Getting actual numbers to plug in left as an exercise for the reader.

Thrymr 12y ago
That doesn't tell you whether you will start the station oscillating in some mode of vibration. For that you'd need a model of the stiffness and structure of the station.

outworlder 12y ago

I thought wobbly stations were a Kerbal problem.

TeMPOraL 12y ago
Not really. In fact, Kerbals can just bruteforce the problem with boatloads of struts. But then again, we don't get to meet the Space Kraken.

sitharus 12y ago

Vibrations are a constant worry for the ISS. The structure is pretty stiff - each module is connected with a series of bolts (20 I think) and very stiff steel rings. One of the long term fatigue problems they have to worry about is the impact of space ship docking - the existing APAS-95 docking ports require a significant force to initiate mating which causes the whole structure to flex, especially the truss as it's perpendicular to most docking ports. NASA are planning to solve this with the low impact docking system (LIDS), but that's not going to be deployed until the Orion capsule flies, or perhaps the SpaceX crewed Dragon. Day-to-day all the exercise stations are mounted on special vibration reducing mounts, even the treadmill. Back in the Space Shuttle days there would be blackout periods for exercise to reduce the vibrations transmitted through the docking port to the shuttle. Space is a harsh mistress.