Difference between revisions of "Tutorial: Advanced Orbiting"

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= Advanced Orbiting Maneuvers =
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== Hohmann transfer ==
This article will cover some more advanced orbiting maneuvers.  The '''bi-elliptical transfer orbit''' can be more efficient (but slower) than the Hohmann transfer orbit in some cases. The other maneuvers will allow you to intercept other orbiting bodies, such as satellites or space stations.
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{{See also||{{Wikipedia|Hohmann transfer orbit}}}}
 +
The '''Hohmann transfer''' is the most frequently used method of changing orbital altitudes while keeping the same [[Orbit#Inclination|inclination]]. The ending orbit may be around the same celestial body as it began or for traveling to another body, such as between [[Kerbin]] and the [[Mun]].  
  
== Bi-Elliptical Transfer Orbits ==
+
It involves first entering an [[Orbit#Eccentricity|eccentric]] orbit, then circularizing once reaching the desired orbital altitude. Thus, there are two burns to be made, ideally using engines with high thrust-to-weight ratios; low TtW can require up to 40% greater Δv from having to start earlier at less efficient points than [[apoapsis]] or [[periapsis]] are for changing orbits.
 +
 
 +
To transfer from a lower orbit to higher:
 +
# Burn prograde at periapsis until the apoapsis reaches the desired altitude.
 +
# Upon reaching the raised apoapsis, burn prograde until periapsis rises to the desired altitude.
 +
 
 +
To transfer from higher to lower:
 +
# Burn retrograde at apoapsis until the periapsis reaches the desired altitude.
 +
# Upon reaching the lowered periapsis, burn retrograde until apoapsis falls to the desired altitude.
 +
 
 +
=== Aldrin Cyclers ===
 +
Hohmann Transfers let you move between orbits or bodies with the intention of changing to a new orbit at the far end. Without taking special care a Hohmann Transfer between two bodies does not form a repeating loop. IE. it is not a fully cyclic orbit. An Aldrin Cycler is an extension on Hohmann that creates a cyclic orbit between two bodies. See [[Tutorial: Earth-Moon Aldrin Cycler]].
 +
 
 +
== Bi-elliptical transfer ==
 +
{{See also||{{Wikipedia|Bi-elliptic transfer}}}}
 +
The '''bi-elliptic transfer''' can be more efficient (but slower) than the Hohmann transfer orbit in some cases (when going from a very tight orbit to a very large one: the ratio must be higher than ~12:1). This is because burns are more efficient at higher speeds, due to the Oberth effect (initial burn raises speed to increase efficiency, this is why the maneuver requires such a large change in orbits to be efficient).
 +
* Start by burning prograde (most efficiently at periapsis) until orbit becomes highly elliptical with the apoapsis higher than starting and desired orbits.
 +
* At apoapsis, burn prograde until the periapsis reaches the altitude of your desired orbit.
 +
* Upon reaching periapsis, burn retrograde until your orbit is circularized.
 +
 
 +
Opposite burns at these same points will lower your orbit. This can be used to enable [[aerobraking]] to lower your orbit height.
 +
 
 +
Check out TomPN's [https://ideone.com/EZ8UHX calculator] for when to use a Hohmann transfer or bi-elliptical transfer.
 +
 
 +
== Orbital plane alignment ==
 +
An important part of intercepting another orbiting body is to align your orbital plane with the target's orbital plane.
 +
 
 +
Start by select the destination body as a target. This will show several new points on your orbit, in particular ascending node (AN) and descending node (DN). These are the points where your orbit crosses the plane of the other body's orbit. ("Ascending" is from the point of view of a prograde (eastward) orbit. If you're orbiting retrograde, your orbital plane "descends" below the other one at the "ascending" node.)
 +
 
 +
Set up a maneuver node at the next one of these nodes. The maneuver you want is pure normal, in the opposite direction from the type of node it is. For the descending node, burn normal ("up", a pink triangle with a dot in the centre); for the ascending node, burn antinormal ("down", an upside-down pink triangle with radial lines and a dot in the centre). See [[Maneuver node]] to see what these symbols look like.
 +
 
 +
General tips:
 +
 
 +
* Don't attempt to match planes anywhere other than an ascending or descending node. It won't work and you'll waste fuel trying.
 +
* It is easier to match orbital planes if your orbit is roughly the same shape (especially regarding eccentricity) as the target, mostly because you can line up the orbits in the map view much more easily.
 +
* Changing inclination is most efficient when you're moving slowly, i.e. high in the orbit. If you're aiming for a polar orbit, arrange that while you're still far away from the body rather than doing it after you've arrived. If you need precision afterwards, start with a high altitude parking orbit.
 +
* If you're merely changing orbits, for example to fulfill a "put a satellite in a particular orbit" contract, try to combine the two maneuvers by making the transfer from an ascending or descending node and adding a normal component to the burn.  Matching planes this way is highly efficient.
 +
* On the other hand, if you need to rendezvous with a body, it's often necessary to make the plane change as a mid-course correction.
 +
 
 +
== Orbit synchronization ==
 
In progress.
 
In progress.
  
== Orbital Plane Alignment ==
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=== Bi-Elliptic Synchronization ===
The first step in intercepting another orbiting body is to align your orbital plane with the target's orbital plane.
 
  
In progress.
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#  Achieve a stable [[orbit]] around the same [[celestial body]] as the target.  If you don't know how there are [[tutorials]].
 +
#  At periapsis  adjust apoapsis so that it is equal to the target orbits apoapsis.
 +
#  At apoapsis circularize the orbit.
 +
#  At the highest Ascending or Descending node, match the orbital plane of the target orbit.
 +
#  At the point where the current orbit intersects the apoapsis of the target orbit, adjust the periapsis to match the target orbits periapsis.
 +
 
 +
If you additionally need to adjust the mean anomaly (crafts position within the orbit), delay the final periapsis adjustment and read the [[tutorials]].
 +
 
 +
=== The Exley maneuver ===
 +
{{outdated}}
 +
(As of {{version|0.17.1}})
 +
[[File:Orbit Synchronization how to.png|thumb|150px|A demonstration using a target planet with an orbit outside your starting planet's orbit.]]
 +
 
 +
Named by its author, wiki user [[User:Sir_Exley|Sir Exley]], it is an approach to getting an encounter with a target planet without having a precise launch window planned by entering an eccentric orbit whose apoapsis meets the orbital path of your target and a periapsis whose altitude has a lower altitude around the sun that the target.
 +
 
 +
In order to easily meet with a target planet's sphere of influence, you will need to perform a few burns while at either the periapsis or apoapsis of your transfer orbit.
 +
 
 +
==== Planets outside your original orbit ====
 +
If you are meeting with a planet whose orbit is outside of your starting orbit, create a transfer orbit such that your apoapsis is as close as possible to your target planet's orbit.
 +
 
 +
Next, make a few orbits until the target planet is slightly in front of you when you reach your apoapsis. Begin a prograde burn until you see your orbit cross the target planet's near your apoapsis for a fraction of a second. If you overshoot, simply turn around and burn retrograde until the cross orbit is visible again. If your transfer orbit exceeds the planet's orbit, then you have gone too far, and have either missed the cross orbit, or do not have an apoapsis close enough to the target orbit to be affected by the planet's sphere of influence.
 +
 
 +
==== Planets inside your original orbit ====
 +
If you are meeting with a planet whose orbit is inside of your starting orbit, create a transfer orbit such that your periapsis is as close as possible to your target planet's orbit.
 +
 
 +
Next, make a few orbits until the target planet is slightly behind you when you reach your periapsis. Begin a retrograde burn until you see your orbit cross the target planet's near your periapsis for a fraction of a second. If you overshoot, simply turn around and burn prograde until the cross orbit is visible again. If your transfer orbit goes within the planet's orbit, then you have gone too far, and have either missed the cross orbit, or do not have a periapsis close enough to the target orbit to be affected by the planet's sphere of influence.
 +
 
 +
==== Finally ====
 +
Once you are in the cross orbit, burn retrograde until the orbit goes around your target planet.
  
== Orbit Synchronization ==
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Good luck!
In progress.
 
  
== Orbit Computing ==
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[[Category:Tutorials|Advanced Orbiting]]
Infomation obtained from: github:gist link:  [ https://gist.github.com/1075144 ]  
 
<br>(Note: roughly at 34700m to 34400m a non-powered craft will start to skim the atmosphere and slow down thus losing its orbit and begin reentry.) 
 
  0 km, Vcirc = 2425.56 m/s, Tcirc =  25.90 min, Vesc = 3430.27 m/s
 
  5 km, Vcirc = 2415.52 m/s, Tcirc =  26.23 min, Vesc = 3416.06 m/s
 
  10 km, Vcirc = 2405.60 m/s, Tcirc =  26.55 min, Vesc = 3402.03 m/s
 
  15 km, Vcirc = 2395.80 m/s, Tcirc =  26.88 min, Vesc = 3388.18 m/s
 
  20 km, Vcirc = 2386.12 m/s, Tcirc =  27.21 min, Vesc = 3374.49 m/s
 
  25 km, Vcirc = 2376.56 m/s, Tcirc =  27.54 min, Vesc = 3360.96 m/s
 
  30 km, Vcirc = 2367.11 m/s, Tcirc =  27.87 min, Vesc = 3347.60 m/s
 
  35 km, Vcirc = 2357.77 m/s, Tcirc =  28.20 min, Vesc = 3334.39 m/s
 
  40 km, Vcirc = 2348.54 m/s, Tcirc =  28.54 min, Vesc = 3321.34 m/s
 
  45 km, Vcirc = 2339.42 m/s, Tcirc =  28.87 min, Vesc = 3308.44 m/s
 
  50 km, Vcirc = 2330.41 m/s, Tcirc =  29.21 min, Vesc = 3295.69 m/s
 
  55 km, Vcirc = 2321.49 m/s, Tcirc =  29.55 min, Vesc = 3283.09 m/s
 
  60 km, Vcirc = 2312.68 m/s, Tcirc =  29.89 min, Vesc = 3270.63 m/s
 
  65 km, Vcirc = 2303.97 m/s, Tcirc =  30.23 min, Vesc = 3258.31 m/s
 
  70 km, Vcirc = 2295.36 m/s, Tcirc =  30.57 min, Vesc = 3246.13 m/s
 
  75 km, Vcirc = 2286.84 m/s, Tcirc =  30.91 min, Vesc = 3234.09 m/s
 
  80 km, Vcirc = 2278.42 m/s, Tcirc =  31.25 min, Vesc = 3222.17 m/s
 
  85 km, Vcirc = 2270.09 m/s, Tcirc =  31.60 min, Vesc = 3210.39 m/s
 
  90 km, Vcirc = 2261.85 m/s, Tcirc =  31.95 min, Vesc = 3198.74 m/s
 
  95 km, Vcirc = 2253.70 m/s, Tcirc =  32.29 min, Vesc = 3187.21 m/s
 
100 km, Vcirc = 2245.64 m/s, Tcirc =  32.64 min, Vesc = 3175.81 m/s
 
105 km, Vcirc = 2237.66 m/s, Tcirc =  32.99 min, Vesc = 3164.53 m/s
 
110 km, Vcirc = 2229.77 m/s, Tcirc =  33.34 min, Vesc = 3153.36 m/s
 
115 km, Vcirc = 2221.96 m/s, Tcirc =  33.70 min, Vesc = 3142.32 m/s
 
120 km, Vcirc = 2214.23 m/s, Tcirc =  34.05 min, Vesc = 3131.39 m/s
 
125 km, Vcirc = 2206.58 m/s, Tcirc =  34.41 min, Vesc = 3120.57 m/s
 
130 km, Vcirc = 2199.01 m/s, Tcirc =  34.76 min, Vesc = 3109.87 m/s
 
135 km, Vcirc = 2191.52 m/s, Tcirc =  35.12 min, Vesc = 3099.27 m/s
 
140 km, Vcirc = 2184.10 m/s, Tcirc =  35.48 min, Vesc = 3088.78 m/s
 
145 km, Vcirc = 2176.76 m/s, Tcirc =  35.84 min, Vesc = 3078.40 m/s
 
150 km, Vcirc = 2169.49 m/s, Tcirc =  36.20 min, Vesc = 3068.12 m/s
 
155 km, Vcirc = 2162.29 m/s, Tcirc =  36.56 min, Vesc = 3057.95 m/s
 
160 km, Vcirc = 2155.17 m/s, Tcirc =  36.93 min, Vesc = 3047.87 m/s
 
165 km, Vcirc = 2148.12 m/s, Tcirc =  37.29 min, Vesc = 3037.89 m/s
 
170 km, Vcirc = 2141.13 m/s, Tcirc =  37.66 min, Vesc = 3028.02 m/s
 
175 km, Vcirc = 2134.21 m/s, Tcirc =  38.03 min, Vesc = 3018.23 m/s
 
180 km, Vcirc = 2127.36 m/s, Tcirc =  38.40 min, Vesc = 3008.54 m/s
 
185 km, Vcirc = 2120.57 m/s, Tcirc =  38.77 min, Vesc = 2998.95 m/s
 
190 km, Vcirc = 2113.85 m/s, Tcirc =  39.14 min, Vesc = 2989.44 m/s
 
195 km, Vcirc = 2107.20 m/s, Tcirc =  39.51 min, Vesc = 2980.02 m/s
 
200 km, Vcirc = 2100.60 m/s, Tcirc =  39.88 min, Vesc = 2970.70 m/s
 
205 km, Vcirc = 2094.07 m/s, Tcirc =  40.26 min, Vesc = 2961.46 m/s
 
210 km, Vcirc = 2087.59 m/s, Tcirc =  40.63 min, Vesc = 2952.30 m/s
 
215 km, Vcirc = 2081.18 m/s, Tcirc =  41.01 min, Vesc = 2943.23 m/s
 
220 km, Vcirc = 2074.82 m/s, Tcirc =  41.39 min, Vesc = 2934.25 m/s
 
225 km, Vcirc = 2068.53 m/s, Tcirc =  41.77 min, Vesc = 2925.34 m/s
 
230 km, Vcirc = 2062.29 m/s, Tcirc =  42.15 min, Vesc = 2916.52 m/s
 
235 km, Vcirc = 2056.10 m/s, Tcirc =  42.53 min, Vesc = 2907.77 m/s
 
240 km, Vcirc = 2049.98 m/s, Tcirc =  42.91 min, Vesc = 2899.10 m/s
 
245 km, Vcirc = 2043.90 m/s, Tcirc =  43.29 min, Vesc = 2890.51 m/s
 
250 km, Vcirc = 2037.88 m/s, Tcirc =  43.68 min, Vesc = 2882.00 m/s
 
255 km, Vcirc = 2031.91 m/s, Tcirc =  44.06 min, Vesc = 2873.56 m/s
 
260 km, Vcirc = 2026.00 m/s, Tcirc =  44.45 min, Vesc = 2865.19 m/s
 
265 km, Vcirc = 2020.13 m/s, Tcirc =  44.84 min, Vesc = 2856.90 m/s
 
270 km, Vcirc = 2014.32 m/s, Tcirc =  45.23 min, Vesc = 2848.68 m/s
 
275 km, Vcirc = 2008.56 m/s, Tcirc =  45.62 min, Vesc = 2840.53 m/s
 
280 km, Vcirc = 2002.84 m/s, Tcirc =  46.01 min, Vesc = 2832.45 m/s
 
285 km, Vcirc = 1997.18 m/s, Tcirc =  46.40 min, Vesc = 2824.44 m/s
 
290 km, Vcirc = 1991.56 m/s, Tcirc =  46.80 min, Vesc = 2816.49 m/s
 
295 km, Vcirc = 1985.99 m/s, Tcirc =  47.19 min, Vesc = 2808.61 m/s
 
300 km, Vcirc = 1980.46 m/s, Tcirc =  47.59 min, Vesc = 2800.80 m/s
 
305 km, Vcirc = 1974.99 m/s, Tcirc =  47.99 min, Vesc = 2793.05 m/s
 
310 km, Vcirc = 1969.55 m/s, Tcirc =  48.38 min, Vesc = 2785.37 m/s
 
315 km, Vcirc = 1964.16 m/s, Tcirc =  48.78 min, Vesc = 2777.75 m/s
 
320 km, Vcirc = 1958.82 m/s, Tcirc =  49.18 min, Vesc = 2770.19 m/s
 
325 km, Vcirc = 1953.52 m/s, Tcirc =  49.59 min, Vesc = 2762.69 m/s
 
330 km, Vcirc = 1948.26 m/s, Tcirc =  49.99 min, Vesc = 2755.26 m/s
 
335 km, Vcirc = 1943.04 m/s, Tcirc =  50.39 min, Vesc = 2747.88 m/s
 
340 km, Vcirc = 1937.87 m/s, Tcirc =  50.80 min, Vesc = 2740.56 m/s
 
345 km, Vcirc = 1932.74 m/s, Tcirc =  51.20 min, Vesc = 2733.30 m/s
 
350 km, Vcirc = 1927.64 m/s, Tcirc =  51.61 min, Vesc = 2726.10 m/s
 
355 km, Vcirc = 1922.59 m/s, Tcirc =  52.02 min, Vesc = 2718.95 m/s
 
360 km, Vcirc = 1917.58 m/s, Tcirc =  52.43 min, Vesc = 2711.86 m/s
 
365 km, Vcirc = 1912.60 m/s, Tcirc =  52.84 min, Vesc = 2704.83 m/s
 
370 km, Vcirc = 1907.67 m/s, Tcirc =  53.25 min, Vesc = 2697.85 m/s
 
375 km, Vcirc = 1902.77 m/s, Tcirc =  53.66 min, Vesc = 2690.92 m/s
 
380 km, Vcirc = 1897.91 m/s, Tcirc =  54.07 min, Vesc = 2684.05 m/s
 
385 km, Vcirc = 1893.09 m/s, Tcirc =  54.49 min, Vesc = 2677.23 m/s
 
390 km, Vcirc = 1888.30 m/s, Tcirc =  54.90 min, Vesc = 2670.46 m/s
 
395 km, Vcirc = 1883.55 m/s, Tcirc =  55.32 min, Vesc = 2663.74 m/s
 
400 km, Vcirc = 1878.83 m/s, Tcirc =  55.74 min, Vesc = 2657.07 m/s
 
405 km, Vcirc = 1874.15 m/s, Tcirc =  56.16 min, Vesc = 2650.45 m/s
 
410 km, Vcirc = 1869.51 m/s, Tcirc =  56.57 min, Vesc = 2643.89 m/s
 
415 km, Vcirc = 1864.90 m/s, Tcirc =  57.00 min, Vesc = 2637.37 m/s
 
420 km, Vcirc = 1860.32 m/s, Tcirc =  57.42 min, Vesc = 2630.89 m/s
 
425 km, Vcirc = 1855.78 m/s, Tcirc =  57.84 min, Vesc = 2624.47 m/s
 
430 km, Vcirc = 1851.27 m/s, Tcirc =  58.26 min, Vesc = 2618.09 m/s
 
435 km, Vcirc = 1846.79 m/s, Tcirc =  58.69 min, Vesc = 2611.76 m/s
 
440 km, Vcirc = 1842.35 m/s, Tcirc =  59.11 min, Vesc = 2605.47 m/s
 
445 km, Vcirc = 1837.94 m/s, Tcirc =  59.54 min, Vesc = 2599.23 m/s
 
450 km, Vcirc = 1833.55 m/s, Tcirc =  59.97 min, Vesc = 2593.04 m/s
 
455 km, Vcirc = 1829.20 m/s, Tcirc =  60.40 min, Vesc = 2586.89 m/s
 
460 km, Vcirc = 1824.88 m/s, Tcirc =  60.83 min, Vesc = 2580.78 m/s
 
465 km, Vcirc = 1820.60 m/s, Tcirc =  61.26 min, Vesc = 2574.71 m/s
 
470 km, Vcirc = 1816.34 m/s, Tcirc =  61.69 min, Vesc = 2568.69 m/s
 
475 km, Vcirc = 1812.11 m/s, Tcirc =  62.12 min, Vesc = 2562.71 m/s
 
480 km, Vcirc = 1807.91 m/s, Tcirc =  62.56 min, Vesc = 2556.77 m/s
 
485 km, Vcirc = 1803.74 m/s, Tcirc =  62.99 min, Vesc = 2550.87 m/s
 
490 km, Vcirc = 1799.60 m/s, Tcirc =  63.43 min, Vesc = 2545.01 m/s
 
495 km, Vcirc = 1795.48 m/s, Tcirc =  63.86 min, Vesc = 2539.20 m/s
 
500 km, Vcirc = 1791.40 m/s, Tcirc =  64.30 min, Vesc = 2533.42 m/s
 
505 km, Vcirc = 1787.34 m/s, Tcirc =  64.74 min, Vesc = 2527.68 m/s
 
510 km, Vcirc = 1783.31 m/s, Tcirc =  65.18 min, Vesc = 2521.98 m/s
 
515 km, Vcirc = 1779.31 m/s, Tcirc =  65.62 min, Vesc = 2516.32 m/s
 
520 km, Vcirc = 1775.33 m/s, Tcirc =  66.06 min, Vesc = 2510.70 m/s
 
525 km, Vcirc = 1771.38 m/s, Tcirc =  66.51 min, Vesc = 2505.11 m/s
 
530 km, Vcirc = 1767.46 m/s, Tcirc =  66.95 min, Vesc = 2499.56 m/s
 
535 km, Vcirc = 1763.56 m/s, Tcirc =  67.40 min, Vesc = 2494.05 m/s
 
540 km, Vcirc = 1759.69 m/s, Tcirc =  67.84 min, Vesc = 2488.58 m/s
 
545 km, Vcirc = 1755.84 m/s, Tcirc =  68.29 min, Vesc = 2483.14 m/s
 
550 km, Vcirc = 1752.02 m/s, Tcirc =  68.74 min, Vesc = 2477.73 m/s
 
555 km, Vcirc = 1748.23 m/s, Tcirc =  69.19 min, Vesc = 2472.36 m/s
 
560 km, Vcirc = 1744.45 m/s, Tcirc =  69.63 min, Vesc = 2467.03 m/s
 
565 km, Vcirc = 1740.71 m/s, Tcirc =  70.09 min, Vesc = 2461.73 m/s
 
570 km, Vcirc = 1736.98 m/s, Tcirc =  70.54 min, Vesc = 2456.46 m/s
 
575 km, Vcirc = 1733.28 m/s, Tcirc =  70.99 min, Vesc = 2451.23 m/s
 
580 km, Vcirc = 1729.61 m/s, Tcirc =  71.44 min, Vesc = 2446.03 m/s
 
585 km, Vcirc = 1725.95 m/s, Tcirc =  71.90 min, Vesc = 2440.87 m/s
 
590 km, Vcirc = 1722.32 m/s, Tcirc =  72.35 min, Vesc = 2435.73 m/s
 
595 km, Vcirc = 1718.72 m/s, Tcirc =  72.81 min, Vesc = 2430.63 m/s
 
600 km, Vcirc = 1715.13 m/s, Tcirc =  73.27 min, Vesc = 2425.56 m/s
 
605 km, Vcirc = 1711.57 m/s, Tcirc =  73.73 min, Vesc = 2420.53 m/s
 
610 km, Vcirc = 1708.03 m/s, Tcirc =  74.19 min, Vesc = 2415.52 m/s
 
615 km, Vcirc = 1704.51 m/s, Tcirc =  74.65 min, Vesc = 2410.55 m/s
 
620 km, Vcirc = 1701.02 m/s, Tcirc =  75.11 min, Vesc = 2405.60 m/s
 
625 km, Vcirc = 1697.54 m/s, Tcirc =  75.57 min, Vesc = 2400.69 m/s
 
630 km, Vcirc = 1694.09 m/s, Tcirc =  76.03 min, Vesc = 2395.80 m/s
 
635 km, Vcirc = 1690.65 m/s, Tcirc =  76.50 min, Vesc = 2390.95 m/s
 
640 km, Vcirc = 1687.24 m/s, Tcirc =  76.96 min, Vesc = 2386.12 m/s
 
645 km, Vcirc = 1683.85 m/s, Tcirc =  77.43 min, Vesc = 2381.33 m/s
 
650 km, Vcirc = 1680.48 m/s, Tcirc =  77.89 min, Vesc = 2376.56 m/s
 
655 km, Vcirc = 1677.13 m/s, Tcirc =  78.36 min, Vesc = 2371.82 m/s
 
660 km, Vcirc = 1673.80 m/s, Tcirc =  78.83 min, Vesc = 2367.11 m/s
 
665 km, Vcirc = 1670.49 m/s, Tcirc =  79.30 min, Vesc = 2362.43 m/s
 
670 km, Vcirc = 1667.20 m/s, Tcirc =  79.77 min, Vesc = 2357.77 m/s
 
675 km, Vcirc = 1663.92 m/s, Tcirc =  80.24 min, Vesc = 2353.14 m/s
 
680 km, Vcirc = 1660.67 m/s, Tcirc =  80.72 min, Vesc = 2348.54 m/s
 
685 km, Vcirc = 1657.44 m/s, Tcirc =  81.19 min, Vesc = 2343.97 m/s
 
690 km, Vcirc = 1654.22 m/s, Tcirc =  81.66 min, Vesc = 2339.42 m/s
 
695 km, Vcirc = 1651.02 m/s, Tcirc =  82.14 min, Vesc = 2334.90 m/s
 
700 km, Vcirc = 1647.85 m/s, Tcirc =  82.61 min, Vesc = 2330.41 m/s
 
705 km, Vcirc = 1644.69 m/s, Tcirc =  83.09 min, Vesc = 2325.94 m/s
 
710 km, Vcirc = 1641.54 m/s, Tcirc =  83.57 min, Vesc = 2321.49 m/s
 
715 km, Vcirc = 1638.42 m/s, Tcirc =  84.05 min, Vesc = 2317.08 m/s
 
720 km, Vcirc = 1635.32 m/s, Tcirc =  84.53 min, Vesc = 2312.68 m/s
 
725 km, Vcirc = 1632.23 m/s, Tcirc =  85.01 min, Vesc = 2308.32 m/s
 
730 km, Vcirc = 1629.16 m/s, Tcirc =  85.49 min, Vesc = 2303.97 m/s
 
735 km, Vcirc = 1626.10 m/s, Tcirc =  85.97 min, Vesc = 2299.66 m/s
 
740 km, Vcirc = 1623.07 m/s, Tcirc =  86.46 min, Vesc = 2295.36 m/s
 
745 km, Vcirc = 1620.05 m/s, Tcirc =  86.94 min, Vesc = 2291.09 m/s
 
750 km, Vcirc = 1617.04 m/s, Tcirc =  87.43 min, Vesc = 2286.84 m/s
 
755 km, Vcirc = 1614.06 m/s, Tcirc =  87.91 min, Vesc = 2282.62 m/s
 
760 km, Vcirc = 1611.09 m/s, Tcirc =  88.40 min, Vesc = 2278.42 m/s
 
765 km, Vcirc = 1608.13 m/s, Tcirc =  88.89 min, Vesc = 2274.24 m/s
 
770 km, Vcirc = 1605.20 m/s, Tcirc =  89.38 min, Vesc = 2270.09 m/s
 
775 km, Vcirc = 1602.27 m/s, Tcirc =  89.87 min, Vesc = 2265.96 m/s
 
780 km, Vcirc = 1599.37 m/s, Tcirc =  90.36 min, Vesc = 2261.85 m/s
 
785 km, Vcirc = 1596.48 m/s, Tcirc =  90.85 min, Vesc = 2257.76 m/s
 
790 km, Vcirc = 1593.61 m/s, Tcirc =  91.34 min, Vesc = 2253.70 m/s
 
795 km, Vcirc = 1590.75 m/s, Tcirc =  91.83 min, Vesc = 2249.66 m/s
 
800 km, Vcirc = 1587.90 m/s, Tcirc =  92.33 min, Vesc = 2245.64 m/s
 
805 km, Vcirc = 1585.08 m/s, Tcirc =  92.82 min, Vesc = 2241.64 m/s
 
810 km, Vcirc = 1582.26 m/s, Tcirc =  93.32 min, Vesc = 2237.66 m/s
 
815 km, Vcirc = 1579.47 m/s, Tcirc =  93.82 min, Vesc = 2233.70 m/s
 
820 km, Vcirc = 1576.68 m/s, Tcirc =  94.31 min, Vesc = 2229.77 m/s
 
825 km, Vcirc = 1573.91 m/s, Tcirc =  94.81 min, Vesc = 2225.85 m/s
 
830 km, Vcirc = 1571.16 m/s, Tcirc =  95.31 min, Vesc = 2221.96 m/s
 
835 km, Vcirc = 1568.42 m/s, Tcirc =  95.81 min, Vesc = 2218.08 m/s
 
840 km, Vcirc = 1565.69 m/s, Tcirc =  96.31 min, Vesc = 2214.23 m/s
 
845 km, Vcirc = 1562.98 m/s, Tcirc =  96.81 min, Vesc = 2210.39 m/s
 
850 km, Vcirc = 1560.29 m/s, Tcirc =  97.32 min, Vesc = 2206.58 m/s
 
855 km, Vcirc = 1557.60 m/s, Tcirc =  97.82 min, Vesc = 2202.78 m/s
 
860 km, Vcirc = 1554.93 m/s, Tcirc =  98.33 min, Vesc = 2199.01 m/s
 
865 km, Vcirc = 1552.28 m/s, Tcirc =  98.83 min, Vesc = 2195.25 m/s
 
870 km, Vcirc = 1549.64 m/s, Tcirc =  99.34 min, Vesc = 2191.52 m/s
 
875 km, Vcirc = 1547.01 m/s, Tcirc =  99.85 min, Vesc = 2187.80 m/s
 
880 km, Vcirc = 1544.39 m/s, Tcirc =  100.35 min, Vesc = 2184.10 m/s
 
885 km, Vcirc = 1541.79 m/s, Tcirc =  100.86 min, Vesc = 2180.42 m/s
 
890 km, Vcirc = 1539.20 m/s, Tcirc =  101.37 min, Vesc = 2176.76 m/s
 
895 km, Vcirc = 1536.62 m/s, Tcirc =  101.88 min, Vesc = 2173.12 m/s
 
900 km, Vcirc = 1534.06 m/s, Tcirc =  102.39 min, Vesc = 2169.49 m/s
 
905 km, Vcirc = 1531.51 m/s, Tcirc =  102.91 min, Vesc = 2165.88 m/s
 
910 km, Vcirc = 1528.97 m/s, Tcirc =  103.42 min, Vesc = 2162.29 m/s
 
915 km, Vcirc = 1526.45 m/s, Tcirc =  103.93 min, Vesc = 2158.72 m/s
 
920 km, Vcirc = 1523.94 m/s, Tcirc =  104.45 min, Vesc = 2155.17 m/s
 
925 km, Vcirc = 1521.44 m/s, Tcirc =  104.97 min, Vesc = 2151.63 m/s
 
930 km, Vcirc = 1518.95 m/s, Tcirc =  105.48 min, Vesc = 2148.12 m/s
 
935 km, Vcirc = 1516.47 m/s, Tcirc =  106.00 min, Vesc = 2144.61 m/s
 
940 km, Vcirc = 1514.01 m/s, Tcirc =  106.52 min, Vesc = 2141.13 m/s
 
945 km, Vcirc = 1511.56 m/s, Tcirc =  107.04 min, Vesc = 2137.66 m/s
 
950 km, Vcirc = 1509.12 m/s, Tcirc =  107.56 min, Vesc = 2134.21 m/s
 
955 km, Vcirc = 1506.69 m/s, Tcirc =  108.08 min, Vesc = 2130.78 m/s
 
960 km, Vcirc = 1504.27 m/s, Tcirc =  108.60 min, Vesc = 2127.36 m/s
 
965 km, Vcirc = 1501.87 m/s, Tcirc =  109.12 min, Vesc = 2123.96 m/s
 
970 km, Vcirc = 1499.47 m/s, Tcirc =  109.65 min, Vesc = 2120.57 m/s
 
975 km, Vcirc = 1497.09 m/s, Tcirc =  110.17 min, Vesc = 2117.21 m/s
 
980 km, Vcirc = 1494.72 m/s, Tcirc =  110.69 min, Vesc = 2113.85 m/s
 
985 km, Vcirc = 1492.36 m/s, Tcirc =  111.22 min, Vesc = 2110.52 m/s
 
990 km, Vcirc = 1490.01 m/s, Tcirc =  111.75 min, Vesc = 2107.20 m/s
 
995 km, Vcirc = 1487.67 m/s, Tcirc =  112.27 min, Vesc = 2103.89 m/s
 

Latest revision as of 02:15, 19 November 2022

Hohmann transfer

→ See also: Hohmann transfer orbit on Wikipedia

The Hohmann transfer is the most frequently used method of changing orbital altitudes while keeping the same inclination. The ending orbit may be around the same celestial body as it began or for traveling to another body, such as between Kerbin and the Mun.

It involves first entering an eccentric orbit, then circularizing once reaching the desired orbital altitude. Thus, there are two burns to be made, ideally using engines with high thrust-to-weight ratios; low TtW can require up to 40% greater Δv from having to start earlier at less efficient points than apoapsis or periapsis are for changing orbits.

To transfer from a lower orbit to higher:

  1. Burn prograde at periapsis until the apoapsis reaches the desired altitude.
  2. Upon reaching the raised apoapsis, burn prograde until periapsis rises to the desired altitude.

To transfer from higher to lower:

  1. Burn retrograde at apoapsis until the periapsis reaches the desired altitude.
  2. Upon reaching the lowered periapsis, burn retrograde until apoapsis falls to the desired altitude.

Aldrin Cyclers

Hohmann Transfers let you move between orbits or bodies with the intention of changing to a new orbit at the far end. Without taking special care a Hohmann Transfer between two bodies does not form a repeating loop. IE. it is not a fully cyclic orbit. An Aldrin Cycler is an extension on Hohmann that creates a cyclic orbit between two bodies. See Tutorial: Earth-Moon Aldrin Cycler.

Bi-elliptical transfer

→ See also: Bi-elliptic transfer on Wikipedia

The bi-elliptic transfer can be more efficient (but slower) than the Hohmann transfer orbit in some cases (when going from a very tight orbit to a very large one: the ratio must be higher than ~12:1). This is because burns are more efficient at higher speeds, due to the Oberth effect (initial burn raises speed to increase efficiency, this is why the maneuver requires such a large change in orbits to be efficient).

  • Start by burning prograde (most efficiently at periapsis) until orbit becomes highly elliptical with the apoapsis higher than starting and desired orbits.
  • At apoapsis, burn prograde until the periapsis reaches the altitude of your desired orbit.
  • Upon reaching periapsis, burn retrograde until your orbit is circularized.

Opposite burns at these same points will lower your orbit. This can be used to enable aerobraking to lower your orbit height.

Check out TomPN's calculator for when to use a Hohmann transfer or bi-elliptical transfer.

Orbital plane alignment

An important part of intercepting another orbiting body is to align your orbital plane with the target's orbital plane.

Start by select the destination body as a target. This will show several new points on your orbit, in particular ascending node (AN) and descending node (DN). These are the points where your orbit crosses the plane of the other body's orbit. ("Ascending" is from the point of view of a prograde (eastward) orbit. If you're orbiting retrograde, your orbital plane "descends" below the other one at the "ascending" node.)

Set up a maneuver node at the next one of these nodes. The maneuver you want is pure normal, in the opposite direction from the type of node it is. For the descending node, burn normal ("up", a pink triangle with a dot in the centre); for the ascending node, burn antinormal ("down", an upside-down pink triangle with radial lines and a dot in the centre). See Maneuver node to see what these symbols look like.

General tips:

  • Don't attempt to match planes anywhere other than an ascending or descending node. It won't work and you'll waste fuel trying.
  • It is easier to match orbital planes if your orbit is roughly the same shape (especially regarding eccentricity) as the target, mostly because you can line up the orbits in the map view much more easily.
  • Changing inclination is most efficient when you're moving slowly, i.e. high in the orbit. If you're aiming for a polar orbit, arrange that while you're still far away from the body rather than doing it after you've arrived. If you need precision afterwards, start with a high altitude parking orbit.
  • If you're merely changing orbits, for example to fulfill a "put a satellite in a particular orbit" contract, try to combine the two maneuvers by making the transfer from an ascending or descending node and adding a normal component to the burn. Matching planes this way is highly efficient.
  • On the other hand, if you need to rendezvous with a body, it's often necessary to make the plane change as a mid-course correction.

Orbit synchronization

In progress.

Bi-Elliptic Synchronization

  1. Achieve a stable orbit around the same celestial body as the target. If you don't know how there are tutorials.
  2. At periapsis adjust apoapsis so that it is equal to the target orbits apoapsis.
  3. At apoapsis circularize the orbit.
  4. At the highest Ascending or Descending node, match the orbital plane of the target orbit.
  5. At the point where the current orbit intersects the apoapsis of the target orbit, adjust the periapsis to match the target orbits periapsis.

If you additionally need to adjust the mean anomaly (crafts position within the orbit), delay the final periapsis adjustment and read the tutorials.

The Exley maneuver

(As of version 0.17.1)

A demonstration using a target planet with an orbit outside your starting planet's orbit.

Named by its author, wiki user Sir Exley, it is an approach to getting an encounter with a target planet without having a precise launch window planned by entering an eccentric orbit whose apoapsis meets the orbital path of your target and a periapsis whose altitude has a lower altitude around the sun that the target.

In order to easily meet with a target planet's sphere of influence, you will need to perform a few burns while at either the periapsis or apoapsis of your transfer orbit.

Planets outside your original orbit

If you are meeting with a planet whose orbit is outside of your starting orbit, create a transfer orbit such that your apoapsis is as close as possible to your target planet's orbit.

Next, make a few orbits until the target planet is slightly in front of you when you reach your apoapsis. Begin a prograde burn until you see your orbit cross the target planet's near your apoapsis for a fraction of a second. If you overshoot, simply turn around and burn retrograde until the cross orbit is visible again. If your transfer orbit exceeds the planet's orbit, then you have gone too far, and have either missed the cross orbit, or do not have an apoapsis close enough to the target orbit to be affected by the planet's sphere of influence.

Planets inside your original orbit

If you are meeting with a planet whose orbit is inside of your starting orbit, create a transfer orbit such that your periapsis is as close as possible to your target planet's orbit.

Next, make a few orbits until the target planet is slightly behind you when you reach your periapsis. Begin a retrograde burn until you see your orbit cross the target planet's near your periapsis for a fraction of a second. If you overshoot, simply turn around and burn prograde until the cross orbit is visible again. If your transfer orbit goes within the planet's orbit, then you have gone too far, and have either missed the cross orbit, or do not have a periapsis close enough to the target orbit to be affected by the planet's sphere of influence.

Finally

Once you are in the cross orbit, burn retrograde until the orbit goes around your target planet.

Good luck!