Quick question about rendezvous.. probably a silly one..

[MoridinUK]

I'm trying to rescue a dear ickle Kerbin. I've got my ship with in 47k of him and now need to 'dock' to get close enough. But my ship has no RCS (other than the reaction wheels in the command modules running low on elecy) Got plenty of Dv left. I have him set as a target but I can't find any vectors on the nav ball for him...

Edited January 5, 2015 by MoridinUK
answered

[Alshain]

47km is too far. You need to use an altered orbit to get within 5km, 10 tops. Make sure you set him as the target from the map screen and when you do you get the pink vector icons. When you get within range through orbiting, you can then make a burn straight toward him by pulling your prograde toward the pink circle marker (or if your going too fast, push your retrograde toward the opposite pink marker)

As you approach the 200meter mark, flip the ship and slow down by burning against the green crosshair, this will eliminate relative velocity to the target. (Make sure the Navball is in "Target" mode). Also be carefull not to burn directly against the kerbal, though they are for the most part fireproof, it will push him into another orbit, or out of orbit.

For more details check out this guide here:

http://forum.kerbalspaceprogram.com/threads/92480-Illustrated-Tutorial-for-Orbital-Rendezvous

Edited January 5, 2015 by Alshain

[radonek]

47km is a long shot, but if you have a lot of fuel it can be done. Click on orbital velocity to get to "Target" mode. Now big violet marker shows vector to poor Ickle and prograde/retrograde markers show relative speed vectors. You point to violet one a give it a kick, see target coming closer. Then aim at retrograde mark and wait as long as distance to target goes down. When it starts going up again, you passed closest approach point - burn retrograde to kill relative velocity. You are stationary somewhat closer then before, but difference in orbit will imediately begin to pull you apart (relative velocity will slowly increase). Rinse, repeat – big violet marker gets you closer, but at speed. Retro burn kills speed. Once you get it into hand, you can combine both into single maneuver. Also, look at some docking tutorial since meeting at almost 50km is pretty bad. With a bit of practice you can get to <500m and avoid catching-up maneuvers entirely. Once you are close enough and have no big relative velocity, its just same as ordinary EVA.

[RW-1]

47km is a long shot, but if you have a lot of fuel it can be done. Click on orbital velocity to get to "Target" mode. Now big violet marker shows vector to poor Ickle and prograde/retrograde markers show relative speed vectors. You point to violet one a give it a kick, see target coming closer. Then aim at retrograde mark and wait as long as distance to target goes down. When it starts going up again, you passed closest approach point - burn retrograde to kill relative velocity. You are stationary somewhat closer then before, but difference in orbit will imediately begin to pull you apart (relative velocity will slowly increase). Rinse, repeat – big violet marker gets you closer, but at speed. Retro burn kills speed. Once you get it into hand, you can combine both into single maneuver. Also, look at some docking tutorial since meeting at almost 50km is pretty bad. With a bit of practice you can get to <500m and avoid catching-up maneuvers entirely. Once you are close enough and have no big relative velocity, its just same as ordinary EVA.

I agree, in early career I've rescued kerbals and had no RCS as well, just make sure you hit RShift to ignite your burns to begin with instead of z, results close by will depress you ....

[WanderingKid]

You CAN use burn towards/kill speed to get near a kerbal in orbit (or anything, really) at that distance, but I don't recommend it. I'd recommend you adjust your orbit to be very close and slightly above/below them in height by about 1k (above if they're behind you in the circle, below if they're in front) and wait. Once the distance starts going up again, then start your rondevous techniques.

Adjust orbit, not direction to target, until you're much closer. It'll save you some sanity.

[EtherDragon]

Think of your rendezvous this way: You need to meet a friend at a particular coffee stand at a particular time, but you each only have 15 minutes to spare before having to move on with your day.

If you arrive at the place more than 15 minutes early, you've got to leave before he gets there, and will not be able to meet.

If you arrive at the place more than 15 minutes late, he has to leave before you get there, and will not be able to meet.

Now, you're in space - and you're still 47km away from where you need to be. Time to reschedule your meeting.

As others posted, you reschedule the meeting by modifying your orbit so that next time you get to this same place, you're both arriving at the same time. The goal should be to get within 2km of them during the encounter - then rendezvous is really easy. 5km is ok, but get's a little hairy.

[MoridinUK]

Ok well, I've burnt a tonne of fuel getting even this close. He is in a very LKO and so I only have 4 arrows of time warp. When I first got into an orbit almost matching his (but a little higher) he was ahead of me and the relative velocity was so low it would take a year or so for him to catch up to me (lower orbits are faster right?) if i'm goign 2190m/s and him 2205 m/s thats 15m/s and with most of an orbit to complete that is a real long time. (I'm not sure what would happen if I bugged out to the tracking station for better time warp, I wasn't sure it would tell me the intercepts. So I did a burn at PE to throw my AE a long way out and so let him catch up sooner.. I was so excited when it seemed I could burn to a 47k intercept.

How do I alter my orbit to reschedule this?

[WanderingKid]

One of the subscribers to my Let's Play recently just asked for a tutorial on this, which I just finished publishing on YouTube.

I'm not sure if this will help you particularly, but here you go:

[MoridinUK]

Well I just let them orbit another once around and our intercept dropped to 3.7km I got it down to a 200m space walk to get the chap in! What a way to pay for a launch pad upgrade!