Space shuttle flight times

Well, Russia just sent a Soyuz pod to the ISS.

http://news.bbc.co.uk/2/hi/science/nature/7665782.stm

Here's a link to the launch video. Near the end, the commentator says that the link up to the station will occur 'two days from now.'

A subsequent news story says the capsule arrived 'slightly ahead of schedule.'

I doubt the shuttle will be either faster or slower. I think the amount of time is more dependant on the problem of synchrenizing orbits. Some trips may be faster, some slower.

Remember that the shuttle will reach orbit very quickly. A matter of minutes. Then both the shuttle and the space station will be in their own unique orbits- they're both circling the Earth every, what, 90 minutes? The rest of the time till docking would be spent reaching the right altitude and drawing those orbits closer.

What you are talking about is called an "Orbital Rendezvous" maneuver and is pretty complicated. It is usually done through a series of what are called, "Hohmann Transfers," alternately elipticizing and circularizing the orbits. Warning: It is highly non-intuitive.

For instance, if the ISS is ahead of you, you would actually slow down in the direction of your motion to reach it. What this does is lowers the perigee on the other side of the orbit causing you to orbit faster. Then, once you've caught up, you would wait until you are at perigee, then apply a delta-V (change in velocity) in your direction of motion to circularize your orbit. Everything in space is done by calculating the magnitude and direction of your delta-v, then applying it at the right time.

The mission is planned out well in advance and the shuttle would fly an ascent trajectory specifically designed to put it in the right place to rendezvous with the ISS after the maneuvers. It is very important that the shuttle reach orbital insertion within a few kilometers(or less) of where it needs to be. There will never be any guess work since the missions are completely and totally modeled using what are called Six Degree of Freedom Simulations, or 6-DOFs. That's actually what I do for a living.

Knowing where these two objects are is of primary importance. During ascent the position of the shuttle will be maintained by onboard instruments consisting of an inertial measuring unit that sense acceleration and rotation and software that takes these measurements and calculates your position using it's own internal 6-DOF. Once in orbit it will maintain this navigation solution and will also receive updates from ground-based radars. The ISS also has an IMU and radar navigation solutions. Ground based measurements can determine the position of satellites to within a few feet.

The entire process is usually designed to take a day or two and is entirely dependent on the orbital insertion position of the shuttle with respect to the ISS. As they get close they are very careful, with closing velocities between the shuttle and the station on the order of just a few meters per second, coming down to inches per second on final approach. Collisions in space are very, very bad, just ask the Russians.

If you have any more questions feel free to PM me.