Difference between revisions of "Basic maneuvers"

From Kerbal Space Program Wiki
Jump to: navigation, search
(→‎Match Orbital Inclination: more info)
m (→‎Match orbital inclination : important information added)
 
(34 intermediate revisions by 25 users not shown)
Line 1: Line 1:
 +
This is a brief "cheat-sheet" of [[orbit]]al 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 ==
  
−
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 straight up until your speed is about 100 m/s.
 +
# At that point, 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 (lean north or south to enter a [[Orbit#Inclination|polar orbit]]), but going east saves fuel by moving with [[Kerbin]]'s own spin.  As a rule of thumb, the rocket's nose should point at the rim of the circle of the prograde marker on the [[navball]]: {{mark|prog-l}}
 +
# Continue to accelerate until your apoapsis (hit M and mouse over the Ap node) is greater than 70 km (the end of Kerbin's atmosphere) - ideally around 100 km.
 +
# Cut your engines (hit 'x') and wait until you are getting close to the apoapsis point.
 +
# Accelerate prograde until your periapsis (also visible on your map) is also around 100 km.
  
−
== Ascend to Orbit ==
+
You can save fuel by being close to your [[w:Terminal velocity|terminal velocity]] during ascent. Lower velocity wastes [[delta-V]] on gravity, higher is wasted on air resistance. The terminal velocity of your rocket depends on how aerodynamically you build it. A slim design with aerodynamic nose-cones decreases drag and thus increases the maximum speed you can reach without wasting too much thrust on drag.
  
−
# Ascend straight up for at least 10 km. See table below for optimal ascent speed.
+
== Change orbital shape ==
−
# 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.
 
−
# 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.
 
−
# Cut your engines and wait until you are getting close to the apoapsis point.
 
−
# 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:
+
In general, burning prograde will make your orbit "larger" and burning retrograde will make it "smaller".
−
{| class="wikitable"
 
−
|-
 
−
! 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 periapsis. Raise your apoapsis by burning prograde at your periapsis instead.
  
−
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.
  
−
Lower your periapsis by burning retrograde at your apoapsis. Raise your periapsis by burning prograde at your apoapsis.
+
== Match orbital inclination ==
  
−
== 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 "ascending node" and "descending node," where the two orbital planes cross.
  
−
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).  
+
The direction the craft needs to burn depends on which direction the current orbit is off from the target orbital inclination. When hovering over the ascending or descending node markers, it will show the difference in degrees. Both show the same difference, but the descending node show the value as a negative number while the ascending node show the value as a positive one. If the craft is passing through the ascending node, where the angle is positive, it needs to burn antinormal[[File:Anti-normal.svg|24x24px|frameless|default]] (South from an equatorial orbit), while if it's passing through the descending node, and the angle is negative, it should burn normal[[File:Normal.svg|24x24px|frameless|default]] (North 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.
 
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.
Line 53: Line 29:
 
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.
 
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 ==  
+
NOTE : You may need a mix of normal/antinormal + prograde/retrograde to keep the orbit circular.
 +
 
 +
== Docking / rendezvous ==
 +
An orbital rendezvous is one of the most challenging maneuvers, 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.
  
 +
# Go to the [[map view]] and use the maneuver tool.
 +
# 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.
 +
# 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.
 +
# At the point of nearest encounter maneuver to make:
 +
##your orbits as close as possible to each other.
 +
##the next encounter (probably right back here) to within 0.5 km or so.
 +
# On reaching that encounter, burn to match velocity. To do this, go back to the staging or docking screen. Click on the "point of reference" on the [[navball]] until it displays the relative target velocity. Rotate the "Level indicator" [[File:Level indicator.svg|24x24px|frameless|default]] (which indicates the direction your vehicle is pointing) until it is aligned with "Retrograde" marker [[File:Retrograde.svg|24x24px|frameless|default]] and burn until you bring the relative target velocity (displayed at the top of the [[navball]]) close to zero (ideally less than 1–2 m/s). At this point you have brought your vehicle close to the target and almost stationary relative to the target - your orbits and velocities should now be nearly identical, and position separated only by a fraction of a kilometer.
 +
# Now, rotate so that the "Level indicator" is aligned with the "Target Prograde" marker [[File:Target prograde.svg|24x24px|frameless|default]]. This points the nose of your vehicle towards the target. You should keep these markers aligned as you approach the target until you are within a few metres and ready to make the final docking maneuvers. Using the SAS may help with this.
 +
# Activate your RCS system, this gives you the finest control of your approach.
 +
# Press the "H" key to start moving towards the target. You should keep the relative velocity low as you approach (less than 10 m/s when more than 500m away, slower as you approach). You should see the "Prograde" [[File:Prograde.svg|24x24px|frameless|default]] marker line up with the "Target Prograde" marker [[File:Target prograde.svg|24x24px|frameless|default]](check that you navball is still has the "Target" as its "Point of Reference"). Use the lateral thrust keys ("I","J","K" and "L") to adjust the "Prograde" marker as you approach, and keep it lined up with the "Target Prograde" marker.
 +
# As you get closer, use the "N" key to slow your approach. Slow down gradually to ~1 m/s by the time you are within 50 meters or so. Eventually come to a stop (0 m/s relative velocity) close to the target.
 +
# Try not to bump into anything while you are docking. See the [[docking]] article for how to actually connect your vessels.
  
−
# Begin by [[#Match Orbital Inclination|matching your orbital inclination]] as described above.
+
== See also ==
−
# If necessary, [[#Change Orbital Shape| raise your apoapsis]] so your orbits intersect.
+
* [[Tutorial:Basic Docking|Basic Docking]] tutorial
−
# 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.
+
* [[Cheat Sheet]]
−
#* 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.
 
−
# 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:
 
−
## Click on the velocity number of your [[navball]] until it reads "Target"
 
−
## 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
 
−
## 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.
 
−
## 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
 
−
# On your encounter, zero your relative speed one last time by burning towards your target,
 
−
# 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)
 
−
# 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.
+
[[Category:Maneuvers]]

Latest revision as of 22:26, 28 November 2018

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 until your speed is about 100 m/s.
  2. At that point, 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 (lean north or south to enter a polar orbit), but going east saves fuel by moving with Kerbin's own spin. As a rule of thumb, the rocket's nose should point at the rim of the circle of the prograde marker on the navball: Prograde
  3. Continue to accelerate until your apoapsis (hit M and mouse over the Ap node) is greater than 70 km (the end of Kerbin's atmosphere) - ideally around 100 km.
  4. Cut your engines (hit 'x') and wait until you are getting close to the apoapsis point.
  5. Accelerate prograde until your periapsis (also visible on your map) is also around 100 km.

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. The terminal velocity of your rocket depends on how aerodynamically you build it. A slim design with aerodynamic nose-cones decreases drag and thus increases the maximum speed you can reach without wasting too much thrust on drag.

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 periapsis. 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 "ascending node" and "descending node," where the two orbital planes cross.

The direction the craft needs to burn depends on which direction the current orbit is off from the target orbital inclination. When hovering over the ascending or descending node markers, it will show the difference in degrees. Both show the same difference, but the descending node show the value as a negative number while the ascending node show the value as a positive one. If the craft is passing through the ascending node, where the angle is positive, it needs to burn antinormaldefault (South from an equatorial orbit), while if it's passing through the descending node, and the angle is negative, it should burn normaldefault (North 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.

NOTE : You may need a mix of normal/antinormal + prograde/retrograde to keep the orbit circular.

Docking / rendezvous

An orbital rendezvous is one of the most challenging maneuvers, 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 0.5 km or so.
  5. On reaching that encounter, burn to match velocity. To do this, go back to the staging or docking screen. Click on the "point of reference" on the navball until it displays the relative target velocity. Rotate the "Level indicator" default (which indicates the direction your vehicle is pointing) until it is aligned with "Retrograde" marker default and burn until you bring the relative target velocity (displayed at the top of the navball) close to zero (ideally less than 1–2 m/s). At this point you have brought your vehicle close to the target and almost stationary relative to the target - your orbits and velocities should now be nearly identical, and position separated only by a fraction of a kilometer.
  6. Now, rotate so that the "Level indicator" is aligned with the "Target Prograde" marker default. This points the nose of your vehicle towards the target. You should keep these markers aligned as you approach the target until you are within a few metres and ready to make the final docking maneuvers. Using the SAS may help with this.
  7. Activate your RCS system, this gives you the finest control of your approach.
  8. Press the "H" key to start moving towards the target. You should keep the relative velocity low as you approach (less than 10 m/s when more than 500m away, slower as you approach). You should see the "Prograde" default marker line up with the "Target Prograde" marker default(check that you navball is still has the "Target" as its "Point of Reference"). Use the lateral thrust keys ("I","J","K" and "L") to adjust the "Prograde" marker as you approach, and keep it lined up with the "Target Prograde" marker.
  9. As you get closer, use the "N" key to slow your approach. Slow down gradually to ~1 m/s by the time you are within 50 meters or so. Eventually come to a stop (0 m/s relative velocity) close to the target.
  10. Try not to bump into anything while you are docking. See the docking article for how to actually connect your vessels.

See also

Retrieved from "https://wiki.kerbalspaceprogram.com/index.php?title=Basic_maneuvers&oldid=92707"