Need some help on a rescue mission

[CharlesKerbin]

Hi Team

I need some help. I need to do a rescue mission, but the orbit is inclined (around 11 degrees from equatorial orbit), with apoapsis of ~14,000km and periapsis of ~12,000km. I'm trying the following sequence of events:

1. Launch into a matching include orbit

2. Burn at periapsis to extend apo to ~13,900km

3. Circularize at apo

4. Catch-up to the target in my slightly lower orbit

5. Slight prograde burn to rendezvous

6. Switch to target-mode approach...

I can't seem to get the right orbit inclination at launch, and just not enough fuel to correct the inclination... What would you do? 

[James Kerman]

Welcome to the forum @CharlesKerbin.

I would get into a high orbit first because you will have less velocity (the faster your velocity, the more Dv needed to change inclination), then match orbit at the An or Dn. After that you can set up a high speed rendezvous with an elliptical orbit or burn down to a circular orbit for a gentler RV.

[Aegolius13]

Hi, and welcome aboard!  Sounds like you're doing everything pretty much right.  I wouldn't worry about trying to get the launch angle exact... just take your best shot, and aim to reduce the difference, knowing it can always be fixed later.  

Are you launching right when KSC passes under the target's orbit?  That's the ideal time to launch if you want to match the orbit.*

Do you know about ascending and descending nodes?  They're the places in your orbit where you intersect the target's orbit.  This means they're the ideal place to match angles with a normal/antinormal burn. In fact they're the only places where you can match planes perfectly.

One important property of orbital mechanics is that the slower your speed, the less delta-v it costs to change planes.  This means that if you're going out to a high orbit anyway, you're better off waiting to do the plane change until you get there.**  So I would add between your steps 3 and 4: after reaching the "slightly lower than target" orbit, do a plane change burn at the ascending or descending node.  

As far as running out of fuel - you may just need to make your ship bigger or more efficient.  We'd need to know more to see if that's the case, and what improvements would work best.  Screenshots always help a great deal.

 

*It is, in fact, the ascending or descending node. 

**Caveat: technically you may be able to do the plane change even cheater if you do at least some of it at the same time you raise your apoapsis, but the difference isn't going to be huge so I'd work on the basic approach first.

[Superfluous J]

I agree with everything  @Aegolius13 said.

If you're still having trouble, I suggest you post a pic of your ship in the VAB with Vacuum dV stats expanded, and maybe a pic of map mode, you in space compared to the target. Then we'll see what we can do

Orbital rendezvous is difficult. Don't feel bad. It only becomes easier after you've done it multiple times and it never becomes *easy*.

[Guest]

I’ve recently been experiencing the wonders of high apogee orbital adjustments for deltaV savings and would highly recommend ! Don’t be scared of getting elliptical!

[Snark]

Moving to Gameplay Questions, since this is a question about how to play the game rather than instructions about how to play the game.

[CharlesKerbin]

You chaps are stars. Thank you so much for your help! I really appreciate the guidance. I apologize for being so tardy in getting back to you, but I finally had a 6 hour flight to effect the rendez-vous and thanks to your advice, all is well! Thank you again!