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How to rendezvous with other orbiting spacecraft


duckunlimited2
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After many days of researching, brainstorming, testing, and general figuring out of stuff, I have designed a Easy-to-follow step-by-step process that will get any two satellites to meet up in orbit; and don\'t worry, there is very minimal math required as per designed.

There are 2 versions of my process: Low-to-High Transfer and High-to-Low Transfer. Both assume that the satellite you want to meet is in a perfect circular orbit and that the spacecrafts orbit is in the same plane as the satellite.

Low-to-High Transfer

1) Set your spacecraft in a circular orbit that has an orbital radius of 63% compared to the orbital radius of the satellite you want to meet up.

- ex: if the satellite you want to meet has an orbital radius of 12,000,000m, you want your craft to have an orbital radius of 7,560,000m or 63% of the meet-up satellite\'s orbital radius.

2) Wait for the satellite, your craft, and the central orbiting body to position themselves, in that order, in a perfectly straight line.

3) Wait for your spacecraft to complete 1 & 3/4 orbits

4) Burn in the direction of travel to raise your Apoapsis up to the same level of orbit as that of the Meet up satellite

-ex: if the meet up satellite has an orbital radius of 12,000,000m, raise apoapsis to that same No.

- For optimal results, do your burn a little later or after you hit 3/4 of that last orbit in step 3

5) wait again for your spacecraft to reach the other side of its orbit at apoapsis

- From here, your spacecraft should meet up with the satellite

6) Burn in the direction of travel to make a circular orbit that matches with the satellites circular orbit

7) Congratz yourself for a job well done!

High-to-Low transfer

1) Set your spacecraft in a circular orbit that has an orbital radius of 159% compared to the orbital radius of the satellite you want to meet up.

- ex: if the satellite you want to meet has an orbital radius of 7,560,000m, you want your craft to have an orbital radius of 12,000,000m or 159% of the meet-up satellite\'s orbital radius.

2) Wait for your craft, the satellite,and the central orbiting body to position themselves, in that order, in a perfectly straight line.

3) Wait for your spacecraft to complete 3/4 orbits

4) Retrograde to lower your periapsis down to the same level of orbit as that of the Meet up satellite

-ex: if the meet up satellite has an orbital radius of 7,560,000m, lower periapsis to that same No.

- For optimal results, do your burn a little early

5) wait again for your spacecraft to reach the other side of its orbit at periapsis

- From here, your spacecraft should meet up with the satellite

6) retrograde to make a circular orbit that matches with the satellites circular orbit

7) Congratz yourself for a job well done!

Do to the fact that while your doing it, you are approximating, you may find that your rendezvous may not be stellar and may find yourself a little too far ahead or behind for a docking attempt. If you find yourself in this situation, follow these correctional maneuvers:

Correctional Rule of Thumbs

To speed your craft up to meet up with the satellite, Retrograde and lower periapsis just slightly. For every orbital period that passes, you will gain on the satellite. The more you lower periapsis, the more you gain on the satellite per orbital period. Once you have sufficiently caught up, bring periapsis back up to to make a circular orbit again at apoapsis.

To slow your craft down to meet up with the satellite, Prograde and raise apoapsis just slightly. For every orbital period that passes, the satellite will gain on you. The more you raise apoapsis, the more the satellite gains on you per orbital period. Once you have sufficiently caught up, bring apoapsis back down to to make a circular orbit again at periapsis.

Seems illogical, but when you lower/raise an orbit, your velocity doesn\'t change much. What changes significantly is the distance you need to cross to complete an orbit. High orbit = more distance = longer orbital period. Low orbit = less distance = shorter orbital period.

This maneuver is best used when you cannot see the satellite\'s distance indicator in the flight screen. It\'s a good way to get the distance indicator into view

The Skipping Maneuver

This maneuver is best used when you can see the satellite\'s distance indicator.

To slow down yourself in order for the satellite to catch up, retrograde a bit to lower your speed. Watch the satellite\'s distance indicator in order to help control the rate at which the satellite closes. As the satellite gets closer, prograde in increments to gently slow the rate the two crafts closes until their in a reasonable distance away from each other to perform docking maneuvers. Once achieved, you can fix your orbit, or attempt a dock.

Important: After you retrograded, your craft, by laws of physics, will start to lose altitude. In order to keep altitude under control, you want to thrust upwards, away from the celestial body your orbiting (do this by placing your indicator on the north pole of your navball and thrust). This type of burn will raise the front half of your orbit, and lower the back half of your orbit without changing your orbital velocity. Periodically thrust up in order to keep altitude (hence the term 'skip'). I find it best to use the main engine to maintain altitude and RCS thrusters to slow the rate of closure.

In order to speed yourself up to catch up with the satellite, prograde instead and periodically retrograde as you get closer. To keep altitude in check thrust straight down (south pole on navball). I think you get the picture.

Aligning A Tilted Orbit

Right after the pivot point (where your two craft\'s orbits meet), you want to thrust in the direction of the satellite\'s orbit. (on the navball, you should be thrusting in between the yellow markers.

With this guide, you now have the ability to create space stations, meet up with other planets, and other things you could imagine. Enjoy

Notes:

you really want both crafts apoapsis and periapsis to be extremely close to the same spot and extremely close to the same altitude. It makes things alot easier.

HarvestR is planning on implementing a feature in the game to help with rendezvous. Since it will be more precise and be a bit more versatile, it probably would outdo this guide. However, it won\'t be released probably in the next few patches.

Be sure to check out WX_Echo\'s Orbital Mechanic calculator. It\'s quite a good tool to help with orbital matters.

Forgot to mention: Altitude and orbital radius aren\'t the same thing. To find orbital radius, take the altitude and add that with the planets radius. (I made that mistake a few times. I\'m just trying to warn you, lol!)

Edited by duckunlimited2
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Thanks, I\'ll be sure to try this out sometime.

Think you could write a version for performing a rendezvous with an orbiting craft from, say, the surface of the mun (or Kerbin, even)

I don\'t think it\'d be that hard. Launch into an orbit just lower than what you want to rendezvous with, wait until you meet up -- since you\'ll be traveling slightly faster than the target vehicle-- and then perform a low-to-high transfer and viola. Rendezvous from the surface of the Mun.

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I don\'t think it\'d be that hard. Launch into an orbit just lower than what you want to rendezvous with, wait until you meet up -- since you\'ll be traveling slightly faster than the target vehicle-- and then perform a low-to-high transfer and viola. Rendezvous from the surface of the Mun.

That\'s basically what I did. It took a long while, but it works. I did it all with the stock game too, no add-ins.

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