Rescue Mission

[Starchaser]

Alright. Several more contracts down, and I decided that poor Helmut Kerbin had waited long enough.

Unfortunately, ole Helmut is orbiting without much maneuver room. After several burns to attempt to bring him to my rescue craft, I had to save and go to work. I came back home, and when I re-loaded the game went into the tracking building and noticed that Rescue 1 was listed as a sub orbital craft. I looked at my peri and it was 42km, and 20 min away. I burned to raise my peri to 74km, but it was a horrible position to make a recovery back to orbit. I still have plenty of delta-v. However, I had neglected to put a pv cell on my craft. I have a battery, and after several orbits I'm only down to 136/150 electrical charge, but I want to make the recovery quickly. I've tried making a small prograde node and looked ahead 3-4 orbits to find a place to make it, and can't find a spot where we approach again.

What would be my best course of action now?

Edited March 27, 2015 by Starchaser

[WanderingKid]

I can't personally see where your ship is in that image. It's going to depend a lot on where you are relative to the Kerbal when you cross orbits.

First I'd push my Periapsis up near his orbit. Then I'd wait until I was nearing it and determine if I was 'ahead' or 'behind' him. If I'm orbiting in front of him I'd keep the other side of my orbit above him, otherwise if you're behind you need to bring it below him so you go faster. A lot depends on your relative position in orbit.

[Deutherius]

One trick to preserve your electric charge is to right click the battery and disable resource drain -> that little green triangle on the right. The battery will stop giving out electric charge unless you reenable the resource drain again, essentially giving your rescue craft infinite amount of time to plan the randezvous and rescue.

As to the randezvous itself, I can't seem to figure out where your rescue ship is. I might be blind, but I just can't see it.

[Claw]

Yeah, I kind of agree. If your AP is above his orbit, but your PE is below his orbit, it's quite possible that it would take a very, very long time for the two to meet up again.

What I would recommend is that you raise your PE to at least Helmut's orbit, and likely above it. Often, I find it's easiest (not always most economical) for the rescue craft to have a circular orbit above or below the target. That way you can place a maneuver node that lowers the PE to match the target's orbit. Then increment the maneuver node an orbit at a time (by collapsing the maneuver node, and clicking the little icons at the lower left/right). Eventually the rendezvous flags will get close. Then you can grab the maneuver node and slide it back and forth till the flags line up.

Sometimes in the process of sliding the flags, the maneuver node will not maintain it's orbit increment. In that case, timewarp forward a few orbits till you catch up to your maneuver node. Just make sure you don't warp past the next rendezvous window. (Paying attention to "ahead" or "behind" as WanderingKid said.)

About your electrical charge...If you only have a manned pod (not a probe core) then your craft will only consume electricity when you are turning the ship. If you need to turn, you can save electricity by turning off SAS. Add a bit of yaw/pitch/roll to start the turn, then let the craft rotate on it's own till you get to the desired orientation. Toggle SAS back on and it will come to a stop. In this way, you can really limit the amount of electricity used per maneuver. If you have a probe core installed, then the craft is going to slowly drain regardless, and you'll have to speed up the rescue.

Good luck...

Cheers,

~Claw

[Starchaser]

I had turned off ships on the display, to hide clutter from my 2 orbiting stations. I didn't realize it would hide my active ship as well. In the orbital pic above, it's between 1 and 2 o'clock. I had closed the game to prevent time passing. If you need a more precise location I will fire the game up again and take another screenie

- - - Updated - - -

Ok, I went back and circularized my orbit. Seems like I wound up with the worst possible outcome.

on the bright side, the burn recharged my batteries. I'm at 153/155 again. Time to see how many orbits it might take for the rendezvous.

- - - Updated - - -

I found a rendezvous. 2 and a half hours until the burn. Closest approach I can get is 1.0 km.

[Claw]

That's not too bad, considering the ships look to be about 50% of an orbit apart.

If you get impatient, you can always make your rescue craft's orbit more elliptical (but keep the AP/PE both above or below the target's orbit). It's just easier to explain via text on a forum board to try from a circular orbit. It's easier to make adjustments to the location of the maneuver node, but can take a little longer to get a rendezvous. Elliptical orbits are a bit more tricky with the maneuver node, because the amount of dV needed to initiate the rendezvous will also be dependent on where you start it.

In any case, it sounds like you are well on your way.

Cheers,

~Claw

[Starchaser]

I've made a number of passes at him. The closest I can get is 500m, and he darts away. The lowest relative velocity I get is 28.2 m/s. I saved it at 3.2 clicks apart. Time to go watch the rendezvous video again.

[Claw]

Ahh, once you are getting close to him, take a look at your NavBall. The velocity will switch from "Orbit" to "Target". You will also see a couple pink markers on the NavBall itself. What you'll need to do is burn retrograde to slow yourself down as you approach.

What is happening is that your rescue craft is now in an elliptical orbit, while the target is in a circular orbit. So right where they meet, you basically need to match your rescue vehicle's orbit with the target (turn it from elliptical to circular). If/when you watch a video, keep an eye on the NavBall symbols while the person executes the final burn.

Also, in anticipation of your next problem, once you get your rescue ship close... Use the ] or [ key to switch control from your rescue ship to the kerbal. Then you can press "R" to activate the kerbal's jet pack and fly over to the rescue ship to climb on board (hopefully you left some room for him...)

Cheers,

~Claw

Here, I found a picture that might help. Unfortunately, the pink retro-target marker is not visible. It's the pink one that looks like a Y. In this picture, the retro-target marker is under the far right white arrow.

Edited March 26, 2015 by Claw

[Landge]

If your 3 km apart can't you set your rescue as target and zero out your relative velocity by firing retrograde to your target? Once you are near matching speeds switch to Helmut and jetpack to the ship.

Rats ninja'd

[Starchaser]

Thanks. I knew about the brackets. I had already watched 5th horseman's rendezvous and docking vids, before I launched, but, it's hard to retain everything before doing it once for yourself.

I did leave room. That would be a kicker wouldn't it? Spend 2 days getting in position to make the rescue and then not have room for him in the craft. Also, thanks to a mishap trying to get a surface sample from the grasslands, on a command module with a small tank still attached, and not being able to get back into the command module...I included a big ladder on the module too.

Too bad it's 11....time to go to bed. Maybe I can rescue Helmut in the morning.

- - - Updated - - -

If your 3 km apart can't you set your rescue as target and zero out your relative velocity by firing retrograde to your target? Once you are near matching speeds switch to Helmut and jetpack to the ship.

Rats ninja'd

I was waiting too long to begin trying to match velocities, nearest I can tell.

[monophonic]

I've made a number of passes at him. The closest I can get is 500m, and he darts away. The lowest relative velocity I get is 28.2 m/s. I saved it at 3.2 clicks apart. Time to go watch the rendezvous video again.

I have made successful rescues with such numbers. Those kerbal RCS packs have some wicked TWR. I had to be quick to get the rescuee headed closer to the ship though. After I am below ~15m/s relative velocity and closer than say 1.5km it is usually smooth sailing. The trick is to not approach too fast or you will overshoot.

[michaelhester07]

If you have enough funds... i'd scrap the current rescue ship and launch an improved one.

- Put a few OX-STATs on it.

As for the intercept I have a few tips.

1. Wait for the target (your rescuee) to be near the India shaped continent to the west of the space center before you launch.

2. Circularize your orbit above his orbit before the intercept unless he passes you during the launch. If he passed you during the launch circularize below his orbit.

3. If he gets within 20km of you during launch switch to "target" mode on the navball and burn on the retrograde marker.

If 3 didn't happen do a normal intercept after 2. There are intercept tutorials out there.

4. When you intercept a rescuee he somehow got stranded with full EVA fuel. Switch to him and hit the R key to active the EVA jetpack so you can get him on the rescue ship.

[Starchaser]

If you have enough funds... i'd scrap the current rescue ship and launch an improved one.

- Put a few OX-STATs on it.

.

Funds aren't a problem for me at the moment. I've been doing contracts with an eye to getting my last upgrade on the science building..(and have ~1500 sci banked for when I do) but I have a quicksave of me and the lil floating guy when we are 3.5 km apart.

- - - Updated - - -

I have made successful rescues with such numbers. Those kerbal RCS packs have some wicked TWR. I had to be quick to get the rescuee headed closer to the ship though. After I am below ~15m/s relative velocity and closer than say 1.5km it is usually smooth sailing. The trick is to not approach too fast or you will overshoot.

I figured out, upon watching the rendezvous tutorial again, that I was thrusting the wrong way, so even though I was closing the distance, I was increasing our relative velocity. Hopefully I can play tonight, and do it right.

[Claw]

To me, it doesn't really sound like you need to restart the mission. Sounds like you're just working your way through learning the rendezvous process. You'll get it, I have no doubt.

Cheers,

~Claw

[Landge]

My rule of thumb when closing the distance to a target is keeping my speed proportional to the distance remaining. You will have better control to prevent overshooting your target. All depends on how much time it takes your engine to slow you down. Quite similar to docking or landing on a airless moon.

1st number is Distance to Target. 2nd number is Speed to Target

100 to 50 km ~ 1000 to 500 m/s

50 to 10 km ~ 500 to 100 m/s

10 to 5 km ~ 100 to 50 m/s

5 to 2 km ~ 50 to 20 m/s

From here on in use RCS if you have it.

2 to 1 km ~ 20 to 10 m/s

100 m to 10 ~ 10 to 5 m/s

10 m or less ~ 5 to 1 m/s

Edited March 27, 2015 by Landge

[Starchaser]

I got him...

I did wind up reloading a save from before I launched. I kept running out of power. I guess I need more practice in turning without SAS. So I reloaded the pre-launch quicksave, and slapped some solar arrays on my command module. Without having to worry about power, I got him with only 1 flub on approach. Although I never did manage to match velocity...closest I got was 0.4 m/s....and that was my flub, I misjudged the angle to apply thrust, and had to line it up again. Our relative speed when I picked him up was 1.7, but he was also only 18 meters away, so I swapped to him and jetted for the ladder.

[Claw]

0.4 m/s is plenty slow. For rescues, getting within a couple m/s is plenty close enough.

In either case, congrats!

-Claw

[bakanando]

Getting below 1m/s around 100m from target is a very nice approach indeed. That is not a flub, it's an achievement.

You will always need to modify your relative speed for docking/pointing to an precise part of a vessel. Next time, try using RCS when you are close enough so you move directly towards your target at speeds below 5m/s.

It looks like you already control the methods for rendez-vous and docking. Congrats

[Harry Rhodan]

Although I never did manage to match velocity...closest I got was 0.4 m/s....and that was my flub, I misjudged the angle to apply thrust, and had to line it up again. Our relative speed when I picked him up was 1.7,

Always remember that you can switch to precise mode with capslock if you're having trouble correctly aligning your retrograde marker to the target marker. And you can tweak down the thrust of your engine if you find yourself constantly overshooting the 0m/s.

[Mapoko]

If your 3 km apart can't you set your rescue as target and zero out your relative velocity by firing retrograde to your target? Once you are near matching speeds switch to Helmut and jetpack to the ship.

Rats ninja'd

I have question. I went to save my first kerbal awhile ago, but I never managed to switch to it. "You can not control objects you do not own" error message. Then I did it with the Klaw, but will be nice to know what I did wrong, so I could not just EVA to the ship. I was just 10m away with the first non-klaw ship, but I had to launch new one.

[AlexinTokyo]

@Mapoko - you need to use the 'switch vessel' keys ('[' and ']' by default on a standard US keyboard) to switch to the Kerbal in need of rescue.

[Harry Rhodan]

I have question. I went to save my first kerbal awhile ago, but I never managed to switch to it. "You can not control objects you do not own" error message. Then I did it with the Klaw, but will be nice to know what I did wrong, so I could not just EVA to the ship. I was just 10m away with the first non-klaw ship, but I had to launch new one.

You have to use the [ and ] keys to switch.

[Mapoko]

@Alexin & Harry thank you very much !

[Landge]

@Starchaser: Congrats on your 1st rescue!

@Mapoko: You also have to be within physics range, 2.3 km or less, for the [ and ] bracket keys to work.