Difference between revisions of "Basic maneuvers"

Revision as of 16:19, 12 March 2013

This is a brief "cheat-sheet" of orbital manuvers, low on details, math, background info or video content (these are all better provided by other pages and articles). This is instead meant as a quick reference while in-game.

Ascend to Orbit

1. Ascend straight up for at least 10 km. See table below for optimal ascent speed.
2. After 10km, begin your gravity turn by slowly leaning east (bearing 90 degrees on your navball, usually "right" from the standard launchpad). You can lean other directions as well but going east saves fuel by moving with Kerbin's own spin.
3. Continue to accelerate until your apoapsis (hit M and mouse over the Ap node) is greater then 80 km (the end of Kerbin's atmosphere) - idealy around 100km.
4. Cut your engines and wait until you are getting close to the apoapsis point.
5. Accelerate prograde (i.e. the direction you are going, represented by a green circle on your navball) until your periapsis (also visible on your map) is also around 100km.

You can save fuel by being close to your terminal velocity during ascent. Lower velocity wastes delta-V on gravity, higher is wasted on air resistance:

Change Orbital Shape

Lower your apoapsis by burning retrograde (see navball) at your peripasis. Raise your apoapsis by burning prograde at your periapsis instead.

Lower your periapsis by burning retrograde at your apoapsis. Raise your periapsis by burning prograde at your apoapsis.

Match Orbital Inclination

If you want to orbit on the same plane as another object (planet, ship, etc) - set it as your target in the map view. You will see two green arrows labeled as the "ascending node" or "descending node" where your orbits are closest. At either of those points burn either "normal" or "antinormal" (which simply means "north" or "south" respectively if you are starting from an equatorial orbit).

If you need several burns to get to your desired inclination, remember that if you burn "normal" on one node you need to burn "antinormal" on the other to keep going the same direction.

It might also help to plan your burns using the orbital maneuver planning system in the map view, where normal and antinormal directions are labeled with purple arrows.

Docking / Rendezvous

1. Begin by matching your orbital inclination as described above.
2. If necessary, raise your apoapsis so your orbits intersect.
3. In map view, you will see an orange/purple pair of arrows. Each colored arrow corresponds to a line of the same color. When you get to an arrow, the corresponding line represents the position of your target.
   • If you are ahead of your target, increase your orbit (larger orbits are slower) and let time elapse until your target catches up with you a little.
   • If you are behind your target, make sure you are in a smaller orbit (smaller orbits are faster) and let time elapse until your catch up with your target.
4. Once the encounter is sufficiently close (~200km give or take is close enough for Kerbin's orbit) you need to zero your relative speed to the target:
   1. Click on the velocity number of your navball until it reads "Target"
   2. When you are at your closest encounter (orange or purple arrow on the map), burn retrograde to slow down (or prograde to speed up) so your relative speed decreases
   3. As you do this, your orbit will start to diverg - match orbits by burning directly towards your target (purple dot on your navball to both fix this and get your next encounter to get even closer.
   4. Repeat this process several times (zero your speed, match orbits, zero your speed, match orbits, etc) until you have some very closely matched orbits and an encounter below 0.3km
5. On your encounter, zero your relative speed one last time by burning towards your target,
6. Now slowly move towards your target but keep slow (~3m/s - you may even want to just use RCS thrusters at this point - the H and N keys can translate you forwards/backwards)
7. Slow down to 0 relative velocity and try not to bump into anything once you are close enough to your target.

See the docking article for how to actually connect your vessels.