Difference between revisions of "Basic maneuvers"

Revision as of 01:02, 24 April 2013

This is a brief "cheat-sheet" of orbital maneuvers, 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 than 80 km (the end of Kerbin's atmosphere) - idealy around 100km.
4. Cut your engines (hit 'x') 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

In general, burning prograde will make your orbit "larger" and burning retrograde will make it "smaller".

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 the two orbital planes cross. 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 icons. Matching orbital inclination is a crucial first step in a rendezvous or docking procedure.

Docking / Rendezvous

An orbital rendezvous is one of the most challenging manuvers, requiring a perfect match in orbit and position. Follow the steps below to get it right on your first try and feel like a space wizard. These steps also work for getting into orbit around planets and moons.

1. Go to the map view and use the maneuver tool.
2. Begin by matching your orbital inclination as described above. During the procedure below occasionally check to ensure that the inclination is exactly zeroed and make correction burns as necessary.
3. Bring one point on your orbit (ideally an apsis) tangent to the target orbit. You will see an orange/purple pair of arrows. Each colored arrow corresponds to the relative position of you and your target. The orange is the nearest encounter, and the purple is the next encounter after that.
4. At the point of nearest encounter maneuver to make:
   1. your orbits as close as possible to each other.
   2. the next encounter (probably right back here) to within 0.5km or so.
5. On reaching that encounter, burn to match velocity. Your orbits and velocities should now be nearly identical, and position separated only by a fraction of a kilometer.
6. Go back to the staging or docking screen. Click on the "point of reference" on the Navball until it displays the relative target velocity This number should be low at this point, within 10m/s.
7. Now slowly "drive" towards your target by aligning the "orbit prograde" and "target prograde" icons on your Navball. Do not exceed ~10m/s. You will probably want to just use RCS thrusters at this point. (If you forgot to put RCS on your rocket... good luck!)
8. Slow down gradually to ~1m/s by the time you are within 50 meters or so.
9. Try not to bump into anything while you are docking. See the docking article for how to actually connect your vessels.