Questions about Elliptical Orbits & Launching Satellites

[Turk_WLF]

I know that people have asked this before but I need some clarification on the finer points of launching multiple payloads from a single launch vehicle.

The Example Mission: Launching 4 satellites in a Geostationary Orbit

 

1. Should I circularize my initial orbit at 80 km & then readjust the Apogee 2868 km on my second pass of Perigee, if so how do I know if I have the spacing correctly for equal deployment?

    

2. Once I’m approach the deployment point of the satellites, how I when to switch from the launch vehicle to the satellite.

    

3. Another question I have is, how much delta-vee does each satellite to circularize & will I need any more fuel once the satellite is in its correct orbit & location?

    

Thanks,

[Zhetaan]

1.  The trick to getting the spacing correct is resonance.  If you want to start at 80 km, go ahead, but it's not going to help you space the satellites correctly.  There are a few ways to do it; with four satellites, the various ways distil to two general methods:

• First, you can set an orbit with apoapsis at the stationary orbit, but when you're there, adjust the periapsis so your orbital period is one quarter (quarter because you have four sats) the orbital period.  A stationary orbit is six hours, so one quarter amounts to an orbital period of 1.5 hours.  This may not be possible on Kerbin:  the periapsis for this orbit may be in the atmosphere or under the surface--you can tell that I don't use this one much.
• Second, you can go to the stationary orbit and instead opt for an orbital period that is either three quarters or five quarters.  This orbit is much more like your final orbit, so it takes less fuel to circularise everything, and more importantly, it is far less likely to graze the atmosphere or otherwise run into issues.

2.  I'm not certain I understand the query here.  If it's a single-launch, multiple-payload mission, I prefer to decouple via right-click on the decoupler or separator rather than bother with complicated staging.  Make certain that any antennae you need are deployed so you don't lose control of anything.  To switch from one craft to the next, press the square bracket ([ or ]).  If you're putting engines on the satellite and want to use it to circularise, then make certain you decouple before you reach the manoeuvre node.  If you're using a transfer stage to do the orbital placement, then make certain your separators have their decoupling force tweaked to zero.

3.  Geostationary delta-vee is theoretically 4,515 m/s.  From an 80 km orbit, it is theoretically 1,115 m/s.  This is from the delta-v map on the wiki.  If you're launching one lifter to orbit and then using the sats to circularise, then each sat needs at least 1,115 m/s.  Some amount of fuel on the sats is usually a good idea, if only for the fact that you probably won't get the placement exactly perfect and will need to adjust the satellites to compensate for orbital drift in ten years or so.