3 ms·
Aren't lower orbits faster? So wouldn't dragon be moving too slowly to maintain it's orbit, not too fast?
by mmaunder 14y ago
Aren't lower orbits faster? So wouldn't dragon be moving too slowly to maintain it's orbit, not too fast?
- pasbesoin 14y agoThink of energy. The higher orbit has higher energy with respect to the earth -- gravitational, and by virtue of comparing stable orbits, also kinetic. Dragon will "catch up" with the space station by converting some additional chemical energy (propellant) into kinetic energy, moving into and matching the station's orbit (and gaining the additional gravitational potential). (Or, given the small adjustment needed, perhaps mechanical energy, depending upon how the positional thrusters work -- compressed gas?) Ugh, my physics classes are a long time away. Hope that's worded halfway comprehensibly.
- dexen 14y agoLower orbits have higher anglular velocity -- and it is angular velocity that dictates which craft gets ahead on orbit, because we're comparing angular position, not linear one. For example, geostationary orbit (~36'000km radius) has period of 24h -- i.e., takes whole 24hours to cover all 360 degrees of rotation, having angular speed of 15deg/h, while Hubble's Space Telescope orbit (~560km radius) has period of 96minutes -- i.e., takes just over 1.5h to cover 360 degrees; with angular speed of 240deg/h. Sure GEO has higher linear velocity and associated kinetic energy, but that's irrelevant. I guess the Dragon was positioned under the Station so it gains the angular position slowly over time in a natural way.
- pasbesoin 14y agoThanks. I felt I was missing something. I should have waited for the coffee to kick in. I'll leave my comment as a warning to what age does to a person. ;-)