*n responding to the Dec 26 question about the possibility of satellite collision, it was stated that:
"If two of them collide, they’re both going to be moving at a good clip, so the net impact speed of a glancing blow won’t necessarily be that high. "
So, I take that to mean that they are all traveling in the same direction.
Really? I didn’t know that. Why would that be so? Is this by agreement, or some law of physics? Might some contrarian not decide to send his satellite in the opposite direction? (remember ‘Midnight Express’?) And finally, just for the hell of it; what direction are they travelling?
Someone could send a sat into an opposing orbit, but it would be silly to do so in an orbit that’s already occupied, because you’d be vastly increasing your chances of having your equipment collide with someone elses, and you’d be risking a very sizeable investment.
And IIRC, there’s something inherently less stable about retrograde orbits.
Edit: It occurs to me that at least one country, Israel, does launch orbits into retrograde orbit, because it doesn’t want batched attempts to fall on its neighbors. Ofeq.
This has the added bonus of being even more costly, because you have to fight earths rotation, rather than gaining it.
They tend to be traveling in the same direction because it is easier to take advantage of Earth’s rotation to provide some of the velocity of orbit, rather than to go retrograde and fight that rotation. That would take a lot more energy, thus fuel, thus weight. It’s called a free ride. Well, not free, but greatly discounted.
So if the Earth is rotating from West to East (Sun travels East to West), that is the direction of launch. That’s why rockets from Florida fly out over the Atlantic Ocean. (Rockets are launched from Florida because the ocean is on that side, so no houses/buildings/people for accidents to fall on.)
And they’re launched from the south because, the nearer the equator, the more the boost. (That’s why France, for example, launches from tropical islands.)
Not all space launch rockets are launched from Cape Canaveral AFS. While there is another smaller space launch facility on the East Coast (NASA Wallops Flight Facility) SLVs are also launched from Vandenberg Air Force Base and the Kodiak Launch Complex, and in fact many Titan IV and EELV launches have occurred out of VAFB; the infamous SLC-6 facility is the primary West Coast launch facility for Delta IV. These sites are typically used for polar or retrograde orbit launches; SLVs that are launched in prograde orbits use CCAFS and launch in an easterly direction for the reasons Irishman lists above.
