Saving Richfal - Orbital Rendezvous

[MajorMushroom]

I must be doing this wrong. My current plan is:

- Match Periapses with targets

-Increase Apoapsis until I get a nice encounter 

Now here is what I don't get, I have to options of which way to point. One (usually) drops my speed, but increases the distance between us, while the other does the opposite.

What must I do to get relative speed and distance to 0? I usually either end up flying at similar speed but being about a kilometre away from him. Also how do I actually get Richfal onto my ship? I haven't been close enough to see it yet, but I assumed I just EVAd him onto my ship, but there is no option to switch to his control. Do we dock or what?

 

EDIT: Thank you everyone! Managed to bring back poor Jebediah after his failed mission to the moon! The A-Team is reunited!

Edited September 30, 2017 by MajorMushroom

[vetrox]

When you get close (think less than 40km or so) your navball should switch to "target" if not you can click it until it says "target"

Once set to target, burn retrograde until the relative speed is 0 then point to target (pink circle) burn until speed is around 50m/s. At this point try to get your prograde marker to match the target marker.  At this point i usually switch to"Docking mode" and use my RCS thrusters to get everything right on the navball.

Once you get close, burn retrograde until your relative speed is 0 again then eva him out of the ship and over onto yours

Edited September 29, 2017 by vetrox

[MajorMushroom]

58 minutes ago, vetrox said:

When you get close (think less than 40km or so) your navball should switch to "target" if not you can click it until it says "target"

Once set to target, burn retrograde until the relative speed is 0 then point to target (pink circle) burn until speed is around 50m/s. At this point try to get your prograde marker to match the target marker.  At this point i usually switch to"Docking mode" and use my RCS thrusters to get everything right on the navball.

Once you get close, burn retrograde until your relative speed is 0 again then eva him out of the ship and over onto yours

Only problem is I can never get close enough without increasing my speed too much, and either way I can't get closer than 1km

[Zhetaan]

@MajorMushroom:

You're doing everything correctly so far.  A one-kilometre separation at orbital distances and speeds is very much a bulls-eye.  However, the problem you describe sounds very much as though you are altering your orbital velocity rather than your relative velocity.  @vetrox is correct in that you need to switch to target mode on the navball; do it by clicking on the speed readout until it says 'Target'.  If it says 'Orbital', one click will make it read 'Surface' and the next will make it read 'Target'.  If it goes from 'Surface' back to 'Orbital' then it means you haven't made Richfal your target yet, but since you mention getting good encounters, I assume you have set him as the target--you may want to check to see whether you accidentally dropped target lock, though.

When you get the navball to 'Target' mode, the prograde/retrograde readouts cease to relate to your orbital velocity and begin to describe your velocity relative to the target.  To add on to @vetrox's answer, you usually want to burn retrograde to zero first because this kills your drift velocity relative to the target.  However, once you do, the difference between your orbits will cause that drift to begin to increase immediately, so it is important to act relatively quickly to close distance and re-zero.  Do this by aiming at the target marker () and burning for it:  50 m/s closing velocity is good for a kilometre out, but you will definitely want to slow as you close.  When separation is at one hundred metres, you will be well-served to have it down to 10 m/s or even lower.  Expect drift to have you coming in slightly inaccurately; it cannot be avoided, and it means that when you do get close enough, you need to burn retrograde (), not anti-target ().  Do this until relative velocity is zero and you will have completely matched orbits.

You do need to EVA Richfal to your ship:  use the square bracket keys ([ or ]) to switch to him once you're within range and your ship is relatively motionless.

[dvp]

Did you do the rendezvous and docking tutorials? Running through those a few times made it really easy for me.

Then '[' or ']' to switch to the other ship once you're within... 500m I think, with zero relative velocity, EVA and spacewalk across.

[MajorMushroom]

1 hour ago, Zhetaan said:

@MajorMushroom:

You're doing everything correctly so far.  A one-kilometre separation at orbital distances and speeds is very much a bulls-eye.  However, the problem you describe sounds very much as though you are altering your orbital velocity rather than your relative velocity.  @vetrox is correct in that you need to switch to target mode on the navball; do it by clicking on the speed readout until it says 'Target'.  If it says 'Orbital', one click will make it read 'Surface' and the next will make it read 'Target'.  If it goes from 'Surface' back to 'Orbital' then it means you haven't made Richfal your target yet, but since you mention getting good encounters, I assume you have set him as the target--you may want to check to see whether you accidentally dropped target lock, though.

When you get the navball to 'Target' mode, the prograde/retrograde readouts cease to relate to your orbital velocity and begin to describe your velocity relative to the target.  To add on to @vetrox's answer, you usually want to burn retrograde to zero first because this kills your drift velocity relative to the target.  However, once you do, the difference between your orbits will cause that drift to begin to increase immediately, so it is important to act relatively quickly to close distance and re-zero.  Do this by aiming at the target marker () and burning for it:  50 m/s closing velocity is good for a kilometre out, but you will definitely want to slow as you close.  When separation is at one hundred metres, you will be well-served to have it down to 10 m/s or even lower.  Expect drift to have you coming in slightly inaccurately; it cannot be avoided, and it means that when you do get close enough, you need to burn retrograde (), not anti-target ().  Do this until relative velocity is zero and you will have completely matched orbits.

You do need to EVA Richfal to your ship:  use the square bracket keys ([ or ]) to switch to him once you're within range and your ship is relatively motionless.

That's all well and good, but at what point should I start decreasing my speed? Earlier or later? Also should I plan on matching orbits? I've noticed this gives me more encounters, so I guess it might be easier to set up another one once I miss one.

[Rocket In My Pocket]

Just follow along with this nice illustrated guide; it's how I learned.

http://i.imgur.com/zAxhwQ5.png

[Pand5461]

@MajorMushroom after you're at 1 km separation, you just need to keep relative velocity marker on top of the target marker . As a rule of thumb, speed = (distance to target)/(20 seconds) is a reasonable value. You may zero the relative velocity at a few dozen meters from target, I usually do that at 20-30 m. Exact matching of orbits is not really necessary, in fact, you need a slightly different orbit to complete the rendezvous. So, there's nothing wrong if, say, periapses differ by 100-200 m and a bit shifted relative to each other.

To keep velocity and target marker aligned, you may use RCS. The rule is, J and L keys move velocity marker left and right, respectively, and I and K down and up. H and N accelerate or decelerate the ship in the current facing direction.

[Rocket In My Pocket]

51 minutes ago, MajorMushroom said:

That's all well and good, but at what point should I start decreasing my speed? Earlier or later? 

As late as possible, as close to your target as possible; at the point where your two orbits are the most similar.

Otherwise the difference in your orbits is going to throw everything off.

Another small tip; when burning prograde you "pull" the prograde marker onto the target marker. When burning retrograde; you "push" the retrograde marker onto the target marker. It doesn't matter which way your ships nose is actually pointing, what matters is where it's actually going; the prograde/retrograde markers will tell you that.

Edited September 29, 2017 by Rocket In My Pocket

[Palaceviking]

Stop looking out the window and look at the instruments!!

[Spricigo]

3 hours ago, MajorMushroom said:

That's all well and good, but at what point should I start decreasing my speed? 

As other said as late as possible. Maintain the relative velocity as high as you can to still avoid overshooting.

Also keep in mind velocity is a vector,  so direction matters.  You need to keep your relative velocity pointed towards your target . With the navball in target mode  should coincide with  and  with  .

 

6 hours ago, vetrox said:

Once set to target, burn retrograde until the relative speed is 0

Don't.  The time your relative speed drop to 0 is the time you start to move away from your target. 

Just control you velocity (direction) to keep going closer to your target, but not overshoot it(velocity intensity). 

[bewing]

BTW, a 1km EVA is just about as easy as a 30m EVA. (They are both kinda tricky, so the extra distance doesn't add any significant difficulty.) So if you get to 1km, you are already there -- 2.2km is enough, even. As said above, use [ or ] to switch control. EVA the victim. Let go of the ladder. Turn on your RCS jetpack. Look around until you spot the rescue ship. Set it as your EVA target. And fly towards it.

EVA fuel is free. So it's preferable to fly your kerbals around in EVA than to spend actual fuel doing a careful rendezvous. In fact, once you get good it's best not to even slow down. You just zoom one ship past the other at 50 m/s, and let the Kerbal burn his jetpack like heck to catch up to the rescue ship.

 

[Spricigo]

1 hour ago, bewing said:

EVA fuel is free.

Lets elaborate a bit for the eventual unaware novice.

Each astronaut have 5 units of EVA fuel that provide about 600m/s deltaV. Each time an astronaut exit a closed crew part that fuel is replenished. So is not just free, but also infinite (as long as the astronaut  can reboard a ship to refill it )

[Snark]

9 hours ago, MajorMushroom said:

Now here is what I don't get, I have to options of which way to point. One (usually) drops my speed, but increases the distance between us, while the other does the opposite.

The illustrated guide that @Rocket In My Pocket posted above is a good way to set up an initial rendezvous, i.e. for getting within a kilometer or so.

To actually close the distance, you may find this illustrated docking tutorial that I wrote helpful.  You're not docking, but a lot of the same principle applies here.

9 hours ago, MajorMushroom said:

Also how do I actually get Richfal onto my ship? I haven't been close enough to see it yet, but I assumed I just EVAd him onto my ship, but there is no option to switch to his control. Do we dock or what?

Yep, you just EVA him across.  You won't be able to switch to his ship until you get within 2.3 km of it.  Once you're close enough, just use [ or ] to switch.

There's no docking involved (stranded kerbals are always in a ship consisting of a single command pod and nothing else, so they never have docking ports on them).

[MajorMushroom]

11 hours ago, Rocket In My Pocket said:

Just follow along with this nice illustrated guide; it's how I learned.

http://i.imgur.com/zAxhwQ5.png

This is what I used to get the intercept markers close, and it works well! Thank you!

 

8 hours ago, bewing said:

BTW, a 1km EVA is just about as easy as a 30m EVA. (They are both kinda tricky, so the extra distance doesn't add any significant difficulty.) So if you get to 1km, you are already there -- 2.2km is enough, even. As said above, use [ or ] to switch control. EVA the victim. Let go of the ladder. Turn on your RCS jetpack. Look around until you spot the rescue ship. Set it as your EVA target. And fly towards it.

 

 

Oh excellent, I've already been close enough to switch control I just didn't know how to, will try it out.

 

11 hours ago, Rocket In My Pocket said:

As late as possible, as close to your target as possible; at the point where your two orbits are the most similar.

Otherwise the difference in your orbits is going to throw everything off.

Another small tip; when burning prograde you "pull" the prograde marker onto the target marker. When burning retrograde; you "push" the retrograde marker onto the target marker. It doesn't matter which way your ships nose is actually pointing, what matters is where it's actually going; the prograde/retrograde markers will tell you that.

Ok that makes sense.

One last thing, I should be prioritising speed over distance right? Get speed down to as close to zero as possible and distance less than 1km 

[MajorMushroom]

8 hours ago, Snark said:

The illustrated guide that @Rocket In My Pocket posted above is a good way to set up an initial rendezvous, i.e. for getting within a kilometer or so.

To actually close the distance, you may find this illustrated docking tutorial that I wrote helpful.  You're not docking, but a lot of the same principle applies here.

Yep, you just EVA him across.  You won't be able to switch to his ship until you get within 2.3 km of it.  Once you're close enough, just use [ or ] to switch.

There's no docking involved (stranded kerbals are always in a ship consisting of a single command pod and nothing else, so they never have docking ports on them).

Success! Thank you very much for writing your guide, it helped a lot. 

I don't think anyone's mentioned this, but circularising your orbit so that it matches the target is great, because it helps to focus on dropping your speed without the annoyance of your distance to target being off, because another encounter will happen, and its usually a better one. 

Also the EVA moment is quite tricky, when it's pitch black and you have to navigate with nothing but a green square (note to self: Install more lights - I forgot about the helmet ones) 

 

-Welcome Aboard!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

-Home Sweet home!

[Spricigo]

3 hours ago, MajorMushroom said:

One last thing, I should be prioritising speed over distance right? 

No. You need to consider both at the same time.

Short distance and high velocity = overshoot or crash

Long distance and low velocity = excessive long time. 

 

 

In any case, you did it. Now its iust a matter of practice to get better at it.

[Snark]

2 hours ago, MajorMushroom said:

Success!

Excellent!    Glad to hear it worked out for you.

2 hours ago, MajorMushroom said:

Also the EVA moment is quite tricky, when it's pitch black and you have to navigate with nothing but a green square (note to self: Install more lights - I forgot about the helmet ones)

Yep.  There are various options that can help mitigate that:

• Set a target.  After you go EVA, double-click on your rescue ship to set it as your EVA kerbal's target.  This really helps, because it makes the target ship show up on your navball so you can navigate using that instead of by trying to see the black ship against a black background.
• Zoom out a little and rotate the camera, so that your EVA kerbal and the target ship are silhouetted against the bright "galaxy" part of the skybox.
• Get really close to the target with your rescue ship, like within a couple of dozen meters, before you go EVA.  That way it'll be within range of your helmet lights when you go EVA.
• Turn on your cabin lights to make your ship easier to see.  Always available, even if you forgot to put extra lights on. 
• Just wait.  Darkness only lasts a few minutes, and you're not in a rush, right?  If you've gotten your rescue ship parked at really really close to zero relative velocity, just timewarp forward a few minutes until you're in daylight again.

[Rocket In My Pocket]

5 hours ago, MajorMushroom said:

This is what I used to get the intercept markers close, and it works well! Thank you!

No problem, if it interests you here is the thread it came from which features several alternative methods illustrated the same way. (I usually avoid posting it first so as not to overwhelm someone with choice.)

13 hours ago, bewing said:

In fact, once you get good it's best not to even slow down. You just zoom one ship past the other at 50 m/s, and let the Kerbal burn his jetpack like heck to catch up to the rescue ship.

I'm more than a little embarrassed to admit that before I actually knew how to rendezvous; an extremely haphazard version of this was basically how I rescued all my Kerbals.

I'd just muck with the maneuver node markers blindly (like seriously just pulling handles at random with only the slightest idea of what they did) until I got some kind of intercept, any intercept. Then I'd jump out when the other ship got close and try to chase it down; often failing abysmally due to being way, WAY, above a 50 m/s speed difference.

I still do a much tamer variation of this like you describe when I'm in a hurry. I've come to lovingly know it as "the hot and nasty" due to my past experiences lol.

Edited September 30, 2017 by Rocket In My Pocket

[Snark]

52 minutes ago, Rocket In My Pocket said:

I still do a much tamer variation of this like you describe when I'm in a hurry. I've come to lovingly know it as "the hot and nasty" due to my past experiences lol.

I'll occasionally do it myself, too, in cases where available dV on the rescue ship is very marginal, and I want to exploit the fact that EVA kerbals have stupid-crazy-huge dV available (600 m/s!)  Go zooming past at hundreds of meters per second, and switch to the rescuee who then has plenty of time to catch up.

I don't do it often, 'coz it feels exploity to me.  But it's certainly an available tool in the toolbox.

One time I had a rescue-kerbal-from-surface-of-Mun contract.  Just for fun, I did it this way:  My rescue ship doesn't (and can't) actually land on the Mun.  Instead, put it into a really really low orbit so it goes screaming past at an altitude < 2.3 km, close enough to "unlock" the rescuee.  (It's a brief dip in the orbit, of course, because 2.3 km is dangerously low on the Mun; if you stay there you're going to smack into an inconvenient mountain pretty soon.)  Then, having done that, I used the stranded kerbal's EVA pack to put himself into low Mun orbit from the surface.  Then I could switch back to the rescue ship and match orbits with the now-orbiting EVA kerbal at my leisure.

That was fun. 

[Spricigo]

2 hours ago, Snark said:

3 hours ago, Rocket In My Pocket said:

I still do a much tamer variation of this like you describe when I'm in a hurry. I've come to lovingly know it as "the hot and nasty" due to my past experiences lol.

I'll occasionally do it myself, too, in cases where available dV on the rescue ship is very marginal, and I want to exploit the fact that EVA kerbals have stupid-crazy-huge dV available (600 m/s!)  Go zooming past at hundreds of meters per second, and switch to the rescuee who then has plenty of time to catch up.

everyone has its own reasons. Mine: cutting part of the 'fine tunning' can make the rendezvous a lot quickier.

[MajorMushroom]

On 30/09/2017 at 3:53 PM, Rocket In My Pocket said:

 

I'm more than a little embarrassed to admit that before I actually knew how to rendezvous; an extremely haphazard version of this was basically how I rescued all my Kerbals.

I'd just muck with the maneuver node markers blindly (like seriously just pulling handles at random with only the slightest idea of what they did) until I got some kind of intercept, any intercept. Then I'd jump out when the other ship got close and try to chase it down; often failing abysmally due to being way, WAY, above a 50 m/s speed difference.

I still do a much tamer variation of this like you describe when I'm in a hurry. I've come to lovingly know it as "the hot and nasty" due to my past experiences lol.

I’ll admit I’m still a bit of a blind tugger, with some sort of an attempted strategy standing slightly sheepishly* behind a mess of quicksaves and quickloads. 

Ill work it out some day

*alliteration  

[Rocket In My Pocket]

31 minutes ago, MajorMushroom said:

I’ll admit I’m still a bit of a blind tugger, with some sort of an attempted strategy standing slightly sheepishly* behind a mess of quicksaves and quickloads. 

Ill work it out some day

*alliteration  

Everyone learns differently, but these two mods really helped me wrap my head around the relationship between 4 dimensional space and the markers on the Navball. NavHud especially, for me it just really helped make the concept easy to learn. Give it a try, hopefully you'll have the same "AHA!" moment.  Precise Maneuver Editor just makes the handles you tug on a lot more user friendly, as well as offering some other neat quality of life improvements to the whole maneuver node experience.

 

(Ignore the 1.2 on NavHud, works fine in 1.3, it even works in the 1.3.1 beta with no issues.)

Edited October 5, 2017 by Rocket In My Pocket

[Spricigo]

2 hours ago, Rocket In My Pocket said:

... the relationship between 4 dimensional space and the markers on the Navball.

That description made me smile.  

The "AHA!" moment one realises that is what need to be figured out mark the transition from hard KSP to easy KSP.

 

[Starchaser]

I know this was closed a bit ago for the most part, but I thought I'd throw my tricks in the ring too.

Getting in the right orbital plane is a priority. Within a degree or 2.

Once you get to the orbital situation on the image labelled "top view" before the radial burn in rocket pocket's illustration, I deviate from the rest of the image. At that point, using Kerbal Alarm Clock mod, I open the "add alarm' dialog and select rendezvous. Leave the dialog open, and drag the orbit counts that it looks for encounters out to 20 orbits. The alarm window will give the distance to closest approach it can find. Turn your rocket pograde and nudge the throttle for a second. If that closest approach gets closer, burn slowly and get the closest approach distance as low as you can. If it gets bigger, turn the rocket retrograde and do the same. I can almost always get within 100 m with only an iteration or 2 of  this approach. 

Granted, it might take many orbits to get there, but it minimizes your delta-v costs, and in the long run, once you're used to the different distances of the rescue orbits they tend to give you, your rocket costs. I use a 10k cost rocket with 4150 delta-v for low kerbal orbit rescues, for example. Once you have a close approach lined up, set the alarm and go do other things. Time on orbit is also free. Just be alert on low orbit rescues on any celestial body that your periapsis isn't too low.

Currently I mixed a tourist contract with a rescue in a wide, highly inclined and highly eccentric orbit. By the time I lined up the inclination and got into the same orbital area, I had just under 800 m/s fuel left. It's gonna take 450 to return to kerbin. Using 30 m/s I got a 1.6 km encounter 17 days away. I'm 9 days into that waiting period. I plan to abort the rescue and return the tourist to Kerbin and try again when I get down to 550 m/s fuel. But I should be able to get him with a 1.6 km encounter and 220 m/s of fuel to play with.

 

Update: I just landed that mission successfully, with 199 m/s fuel left.

Edited October 16, 2017 by Starchaser
updated info