LKO Rescues

[Ineedaweapon]

(Im on xone in case that makes a difference)

 

So I got my first couple of rescue missions and played through the docking tutorial to learn the basics of intercepting, but when I tried to apply this knowledge to my career game it seemed impossible.  The problem is in the tutorial youre going from a low orbit to a higher one with a lot of space in between.  In my game, those in need of rescue are already in a really low orbit (about 84km) but if I put myself in a lower orbit to transfer up, there isnt enough space.  No matter where I move the maneuver node to I simply cant get the intercept things (forget what you call them) to line up.  It doesnt help of course that the nodes are ridiculously fiddly to set up, at least on console.  If I try going from higher to lower orbit then it seems my projected path will lead me down into the atmosphere again.

What I would like to know, is there an easier way of doing this that I havent thought of?  An alternative method altogether?  Also, I havent unlocked docking hatches yet, im assuming ill be able to just eva the kerbals from one craft to the other?

[Geschosskopf]

2 hours ago, Ineedaweapon said:

What I would like to know, is there an easier way of doing this that I havent thought of?  An alternative method altogether?  Also, I havent unlocked docking hatches yet, im assuming ill be able to just eva the kerbals from one craft to the other?

Well, if they're in very low orbits, you have 2 choices:

1.  Launch from the ground directly to intercept as they pass over.  This is a bit tricky but there are a number of videos on the subject if you search YouTube.

2.  Launch to a higher orbit, sync up with the target, and then transfer down to it.  This is much easier.  It works the same as going from a lower to a higher orbit, just in reverse.  You wan to place your intercept node so that you meet the target on the opposite side of Kerbin from where you do the burn.  This prevents you entering the atmosphere.  You want to do the burn when the target some ways behind you but not too far.  For instance, if you're in a 150km orbit and they're in an 84km orbit, do your burn when the target is about "1 hour" behind you.  By that I mean, look down on Kerbin from the north pole.  Pick some direction arbitrarily to be the 12 o'clock position on a clock face.  So if your ship is at "3 o'clock", you want to burn when the target is about at "4 o'clock".  This does NOT mean an actual hour of gametime behind you :).

[MrDave]

Also, if you press the left or right bumper when controlling the cursor, it'll give you fine contol.

[steuben]

#2 is your best option. i've got a disposable station at ~300 km up with a number of rescue pods attached to it. i just blow one off, and drop it down to pick up the fellow, and then drop it down to the ground. 

don't forget you can fine tune your node position by dragging it around as well... at least on the pc version not sure about the console ones.

 

Edited July 24, 2016 by steuben

[Geschosskopf]

3 hours ago, Ineedaweapon said:

(Im on xone in case that makes a difference)

I won't hold that against you .  But yeah, the whole console thing is something I"m going to have to keep in mind now.  I'll have to refrain from giving instructions in terms of keyboard commands and say what the commands actually do.  This will take me some time to get used to as I've been used to an exclusively PC community for the past several years

But anyway, belated WELCOME ABOARD! 

[bewing]

Um, I'm not sure the previous posts quite answered your question -- so let me try it a different way.

When you are orbiting in your rescue vehicle, and you have targeted a victim in their derelict, it is not often possible to get an intercept/rendezvous in just one orbit. So setting a maneuver node usually doesn't work right away.

So what was casually said above about "sync up with" the other craft is the tricky part. The one vastly important thing you need to understand is that low orbits take less time than higher orbits. So if the derelict is below you, then they will be catching up to you from behind a little bit with every orbit. You can enhance this effect by burning prograde and raising your orbit even higher. That will make your orbits take even longer, and the derelict will catch up a bigger angle with each orbit. And then you wait. You can be extreme about this, and raise your orbit really high -- but that will cause you a lot of problems for the final intercept. The time to make your maneuver node is on the orbit when you know that the victim's ship is going to be passing you. So you have to keep track of how fast they are catching up.

[Zophos]

First (because I don't think anyone has answered this part of your question): Yes, you will be able to EVA the stranded Kerbal across to your rescue ship. In fact, you can't generally dock with the stranded parts because they don't come equipped with docking ports.  When you get the grabber, you can grab those parts if you really want to avoid EVA.

As for the rendezvous, there are a few points worth mentioning, some of which have already been addressed:

• If you put yourself in a lower orbit than the target, you will "gain" on it (travel a larger angle in a given time). A higher orbit is the opposite.
• The larger the difference in altitude, the faster your angle will change relative to the target.
• Either way will work; if you are close behind your target and in a higher orbit, it will get farther and farther ahead, until eventually it is coming up behind you. Of course, this may take a few orbits.
• Crossing the target's orbit (altitude) is inefficient, as you will spend part of the orbit gaining and part losing relative to the target. So pick one.
• If the target is in a low orbit, you have much more maneuvering room if you pick a higher orbit and let it gain on you.

With all that in mind, what I usually do is launch to a circular orbit at about the altitude of the target's apoapsis. Then, at that apoapsis (wherever it falls on my orbit), I will burn prograde to raise my apoapsis some way above the target's orbit.  This puts me in an elliptical orbit higher than the target, so my orbit will take longer than the target's (it will gain on me). Moreover, my periapsis is at the same point as the target's apoapsis, and it will stay that way as long as I burn only at my periapsis (raising or lowering my apoapsis). 

My goal at that point is just to make sure I hit periapsis at the same time the target hits apoapsis.  Generally, only a handful of orbits is needed to get one where the target will be relatively close behind me at the meeting point --- specifically, where it would be ahead of me on the next orbit if I don't do anything. At that point, I burn retrograde at periapsis to lower my apoapsis; not all the way to match orbits, but just enough to let the target catch up to an extremely close encounter at the next meeting. Finally, at the encounter, a second retrograde burn matches orbits (lowering my apoapsis to match the target's periapsis).

You can apply the same ideas whether you choose to meet at the apoapsis or periapsis of the target's orbit. But by staying strictly above the target, you will never hit atmosphere as you've described.

There are also more sophisticated techniques in which you enter a circular "phasing orbit" and then do a Hohmann transfer to the target at the right point. They are more efficient in some cases, but they involve more burns and more calculation.  The technique described above can be done entirely on the screen with maneuver nodes and your eyeball.

[Champ]

of course, if you are in career, you must have upgraded the astronaut complex (for EVA) and the tracking station and mission control (for patched conics)

[Ineedaweapon]

Thanks to everyone for all the info, its much appreciated

 

21 hours ago, Geschosskopf said:

I won't hold that against you .  But yeah, the whole console thing is something I"m going to have to keep in mind now.  I'll have to refrain from giving instructions in terms of keyboard commands and say what the commands actually do.  This will take me some time to get used to as I've been used to an exclusively PC community for the past several years

But anyway, belated WELCOME ABOARD! 

 

Perhaps they should make a separate board for consoles, but then we would lose out on all the valuable experience of the seasoned pc players . 

[Geschosskopf]

3 hours ago, Ineedaweapon said:

Perhaps they should make a separate board for consoles, but then we would lose out on all the valuable experience of the seasoned pc players . 

What somebody needs to do is post up a picture of what gamepad button does what (I imagine there are deep menus on some of them) , and have this stickied, so us PC types can reference it when answering questions.

[wumpus]

If you are about to attempt to rescue *plural* kerbals from the Mun, be careful about the directions of the orbits.  Once I decided to pick up two (likely from Minmus) when I discovered they were going opposite ways around Minmus.  Luckily, I [had thought I] vastly overbuilt for that mission and manged to get them both, but reversing orbit is an expensive proposition.

[bewing]

2 hours ago, Geschosskopf said:

What somebody needs to do is post up a picture of what gamepad button does what (I imagine there are deep menus on some of them) , and have this stickied, so us PC types can reference it when answering questions.

PS4: 

Xbone:

-- The problem is that most of them are button combos, and they are all abbreviated.

(The other problem is that the poor suckers are running 1.1.0 (pre-release) -- so you have to remember just how rough things were in the middle of April.)

Edited July 26, 2016 by bewing

[Geschosskopf]

28 minutes ago, bewing said:

PS4: 

Xbone:

-- The problem is that most of them are button combos, and they are all abbreviated.

(The other problem is that the poor suckers are running 1.1.0 (pre-release) -- so you have to remember just how rough things were in the middle of April.)

Egad.  I'd never make sense of that.  And I'm VERY thankful KSP started on the PC and went to consoles instead of the other way around.  I shudder to think what the UI would be like otherwise

And geez, 1.1-pre?  Kraken help them....

[StarStryder]

What I do is launch into the same orbit as the target.  Then put a maneuver node at Pe and add prograde until the intercept marker gives a close pass.  Remember that you need to make sure your relative inclination is low. Burn at An or Dn to adjust it. 

This method will give you an encounter in a single orbit, although it uses more dV than a multi-orbit solution.

[magnemoe]

I always launch to come some kilometers ahead of target, this way I can set up an small burn to raise my Ap so the target catch up with me on the next orbit. 
This can be done as part of the circulation burn if you have some experience, else just do it after circulation, try to get less than 10 km from target but 20 is no issue. 
You don't want to come up behind as you can not lower your orbit much. 

Now its adjustment burns, it can be smart to reduce the trust on your engine for this, eiter set up an node for some ideas of direction or just try to burn in any direction and see if distance increase or goes down, if its increase turn around and burn the other way, now try normal and antinormal, then pro and retrograde again until closest distance is below 2 km.
Increase engine power to max, make sure you are in target view and you want to kill speed relative to target at closest point, do the burn until relative speed is close to zero. 

You can switch to kerbal and have him exit and use his jetpack toward your ship but if you are an new player the ship is easier to control so you might burn towards the target and then brake then closest who should bring you an short distance away. 
Switch to other pod, now target your rescue ship, this makes things much easier, eva kerbal, turn on jetpack and get him to the rescue ship. 
Switch to orbital mode, reduce Pe down to 30 km for landing. 

Its smart to put an extendable ladder on the rescue ship so the kerbal have something except the pod hatch to grab, 

 

[DaMachinator]

15 hours ago, wumpus said:

If you are about to attempt to rescue *plural* kerbals from the Mun, be careful about the directions of the orbits.  Once I decided to pick up two (likely from Minmus) when I discovered they were going opposite ways around Minmus.  Luckily, I [had thought I] vastly overbuilt for that mission and manged to get them both, but reversing orbit is an expensive proposition.

On minmus nothing is expensive. I bet you could EVA the kerbal in the wrong orbit all the way to your ship with just his/her jetpack.

[wumpus]

1 hour ago, DaMachinator said:

On minmus nothing is expensive. I bet you could EVA the kerbal in the wrong orbit all the way to your ship with just his/her jetpack.

It has to be at least 320 m/s delta-v.  And you can't EVA until you are sufficiently "close" (on rescue contracts.  If you stranded your kerbals this isn't a problem), even though the jetpacks probably *have* 320 m/s delta-v (keep at least some in reserve to get in the capsule).  As I mentioned, I could do it.  I wouldn't want to try it around the Mun where it would be at least twice as expensive (according to the subway chart that I taped to my monitor around beta).

[DaMachinator]

It's almost certainly less than that - I've reversed orbits on Minmus before, and I don't remember it being THAT much...

[bewing]

It depends on how high your orbit is. Orbital speed on Minmus can be as low as 8 m/s (at 2Mm altitude). If you want to reverse your orbit, it almost always pays to increase your Ap really high first.