Difference between revisions of "Basic maneuvers"

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(→‎Match Orbital Inclination: more info)
(→‎Docking / Rendezvous: fixed the instructions)
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== Docking / Rendezvous ==  
 
== Docking / Rendezvous ==  
  
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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.
  
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# Begin by [[#Match Orbital Inclination|matching your orbital inclination]] as described above.  
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# Go to the [[map view]] and use the maneuver tool.
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# If necessary, [[#Change Orbital Shape| raise your apoapsis]] so your orbits intersect.
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# Begin by [[#Match Orbital Inclination|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. This matches orbital angle.
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# 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.
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# Bring one point on your orbit (ideally an [[Terminology#Orbital_Terms|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. This matches orbital radius.
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#* 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.
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# At the point of nearest encounter maneuver to make:
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#* 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.
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##your orbits as close as possible to each other.
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# 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:
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##the next encounter to within 0.5km or so.
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## Click on the velocity number of your [[navball]] until it reads "Target"
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# 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.
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## 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
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# 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.
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## 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.
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# 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.
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## 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
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# Slow down gradually to ~1m/s by the time you are within 50 meters or so.
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# On your encounter, zero your relative speed one last time by burning towards your target,  
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# Try not to bump into anything while you are docking. See the [[docking]] article for how to actually connect your vessels.
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# 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)
 
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# Slow down to 0 relative velocity and try not to bump into anything once you are close enough to your target.
 
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See the [[docking]] article for how to actually connect your vessels.
 

Revision as of 17:26, 17 April 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:

Altitude (m) Aprox. Terminal Velocity (m/s)
500 105
1,000 110
2,000 120
3,000 130
5,000 160
8,000 215
10,000 260 (remember to start your gravity turn!)
13,000 350
15,000 425
16,000 470
32,000 2250

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 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.

  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. This matches orbital angle.
  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. This matches orbital radius.
  4. At the point of nearest encounter maneuver to make:
    1. your orbits as close as possible to each other.
    2. the next encounter 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.
  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.
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