How to hit a strange orbit effeciently

[trinimac]

I received a contract to put a satellite into a specific orbit but I have no clue where on the nav ball to point the rocket during launch to get there efficiently. would love some help on how to get to this orbit (and other strange orbits) from launch efficiently.

[Anquietas314]

Without knowing which direction that orbit is in, I would have to guess you should either tilt over at 10km towards ~315-325 on the navball, or towards 135-145. It's hard to tell from the angle the screenshot was taken at though. You want to wait til KSC (i.e. you) is just slightly to the west of where the orbit passes over the equator before launching. That should put you into an orbit that's not terribly far away from the right inclination.

[Captain Sierra]

Okay, I will recommend that you wait until KSC is under that orbit. Then you need to launch into that inclination. That will save you dV from making an inclination change. You may need to do some radial/antiradial and normal/antinormal burns to get it on target. There's no real 'best' way to get into that.

[trinimac]

Alrighty thanks for the tips guys. It says its a 63 degree orbit. how do i tell i'm launching at the right angle? is it the numbers under the nav ball?

[Anquietas314]

Alrighty thanks for the tips guys. It says its a 63 degree orbit. how do i tell i'm launching at the right angle? is it the numbers under the nav ball?

The numbers around the horizon on the navball are bearings. 0 = north, 180 = south, etc.

[LethalDose]

Like Capt. Sierra said you want to launch straight into that orbit off the pad. It will save you hundreds of dV. A step by step I would offer would be:

1. Launch directly into the inclination off the pad with a low PE
   
2. Circularize
   
3. Boost your AP to meet the target orbit's PE
   
4. At your new AP, boost until your orbit has a it's PE at your current location, and continue to thrust until your AP is at it's target.
   

This isn't the most efficient method to get the orbit (it would be more efficient to boost the full AP in one go), but it's is pretty easy to set up.

[LethalDose]

The numbers around the horizon on the navball are bearings. 0 = north, 180 = south, etc.

Actually, this will screw you up. It's a 63 degree inclination from the equator! If the inclination is 63 degrees in a NE direction, you need to burn at 90 (ecliptic) - 63 (target inclination) = 27 degrees heading.

[Anquietas314]

Actually, this will screw you up. It's a 63 degree inclination from the equator! If the inclination is 63 degrees in a NE direction, you need to burn at 90 (ecliptic) - 63 (target inclination) = 27 degrees heading.

I was aware of that. If you read my first post in this thread, I suggested leaning towards (approximately) 315 or 135 depending on the direction of the orbit based on the screenshot. Oddly a 63 degree inclination doesn't fit that orbit o.O (look at the ascending/descending nodes.)

[purpletarget]

Time the launch for when KSC is just about to pass under the orbit, as was already mentioned.

Then it's a matter of doing your gravity turn on the inclination heading...so if you want an inclination of 63 degrees, then you want to goto a heading that is around 63 degrees away from East for a prograde or West for a retrograde orbit. (I'm not sure how the contracts are measuring the inclination, and the picture doesn't really indicate direction, and the An/Dn don't make sense to me for a 63 prograde...)

however, ...there's also the rotation of Kerbin...so you'll probably want to steer westward about 3 degrees or so from whichever you pick.

(So, 63 prograde inclination, and launching notherly, you'll want East (090) minus 63 (notherly) for heading of 027, and then westerly another 3 for 024)

If you time it right, you should be within a degree or two from full alignment once you hit orbital velocity at LEO.

You can pretty much align yourself from a circular parking orbit (anything lower than the Pe of your final orbit), and then push out the Pe/Ap into the target shape once you're done.

[Chewy]

I would have taken a slightly different strategy than most here, but I'm interested in what everyone thinks:

1. Launch on a trajectory that crosses the target orbit at its PE, but is rotated maybe 10 degrees relative to kerbin's axis. So I would wait for KSC to be 10 degrees past the orbit before launching and then shoot for a heading around 73 degrees from east (say to the northeast for the sake of my example). I would tweak the trajectory in map view during the launch so that my AN would line up with the target PE and circularize.

2. At the point where I cross the target orbit (AN), I would burn prograde until my orbit crosses the target orbit near its AP.

3. Now I should have an orbit that has its AN close to the target PE, and its DN near the target AP, but with an inclination difference of 10 degrees or so. At DN, my speed is very low, probably under 50 m/s or less, so I can make the 10 degree inclination change for very little DV.

4. Make a couple final tweaks radially and pro/retro to match the orbit more closely and voila!

This would only make sense only for highly eccentric or high altitude orbits. Point is that a 1 degree inclination change in a circular LKO takes more fuel than a 10 degree inclination change at the AP of a highly eccentric orbit, but it's easier to match the AN to the target PE with a slight inclination difference at launch.

Any thoughts?

[Wanderfound]

Also keep in mind that the tiny weight of a minimal satellite makes ÃŽâ€V very cheap. A lightweight sat can reach escape velocity from LKO off just a single FL-R10 monoprop tank.

[Janos1986]

With my current technology and RemoteTech installed I can't reach those orbits either.

If I get into a fuel-efficient suborbital path my apoapsis ends up beyond the line of sight of ksc breaking connection, if manage to keep it high above the ksc I then lack deltaV to do anything except circularize at 100 kilometers.

I don't have patched conics so using the probe flight computer is impossible since I lack manever nodes to program.

All my parts are too heavy and I still have the 30 part limit.

I'm stuck with kerbin surveys until I unlock conics. Bummer.

Edited December 22, 2014 by Janos1986

[Aedile]

Launch at appropriate time. Then go north or south as required. Once the inclination is close enough, turn to match exactly your prograde (orbital) vector.

If you are using remote tech, and this is your first sat contract, this could be pretty difficult. On the bright side the tundra and "kolnya" will give you a pretty nice coverage afterwards.

[Red Iron Crown]

Like Capt. Sierra said you want to launch straight into that orbit off the pad. It will save you hundreds of dV. A step by step I would offer would be:

1. Launch directly into the inclination off the pad with a low PE
   
2. Circularize
   
3. Boost your AP to meet the target orbit's PE
   
4. At your new AP, boost until your orbit has a it's PE at your current location, and continue to thrust until your AP is at it's target.
   

This isn't the most efficient method to get the orbit (it would be more efficient to boost the full AP in one go), but it's is pretty easy to set up.

It is slightly more efficient to raise Ap to the desired Ap as step 3 and raise Pe to desired Pe from there as step 4, but that's a nitpick. It's step 1 where the big savings are.

[Anquietas314]

Chewy: That's not a bad way to do it - it does at least make getting the inclination part right during launch a non-issue - but it can be done more efficiently