Best way to orbit a thing

[Fireheart318]

This tutorial will show you the best way to get into orbit around a celestial body - planet, moon, star, whatever. This tutorial assumes you've already got an encounter set up. The law of physics you'll be exploiting here is called the Oberth Effect and it's EXTREMELY efficient!

Step 1: Burn retrograde at periapsis until you're in orbit. STOP AS SOON AS THIS HAPPENS!!!

Step 2: Now's the time to make any inclination changes - you probably want an orbit along the equator - an equatorial orbit. Make a maneuver node at the equator and adjust accordingly. This is really only useful for a few bodies - Moho, Gilly, Minmus, Dres, and Bob. I'm probably forgetting one.

Step 3: Burn retrograde at apoapsis until your periapsis reaches the desired altitude.

Step 4: Burn retrograde at periapsis until your apoapsis reaches the desired altitude.

 

That's pretty much all I've got to say so Fireheart318 out!

[Pecan]

Are you aware there is a tutorials sub-forum?

[Windspren]

I'm pretty sure you burn prograde in all of those maneuvers, and I don't see anything different with your methods and everyone else's

 

Edited May 7, 2016 by Laythe Dweller

[SchweinAero]

6 minutes ago, Laythe Dweller said:

I'm pretty sure you burn prograde in all of those maneuvers, and I don't see anything different with your methods and everyone else's

Isn't this how to capture from a hyperbolic trajectory? But yes, there aren't really all that many choices.

[LameLefty]

Bless his heart, every newbie thinks they're a genius when they figure this stuff out.  

But yeah, this is better posted in the Tutorials forum, and better still as an answer of sorts (*) to someone's specific question how to achieve orbit once you enter an SOI on a hyperbolic trajectory.

 

(*) I say "of sorts" because it could really use more detail and some screenshots of the Map screen to help people understand what he's trying to describe.

[problemecium]

You can also save up to a few hundred m/s of delta-V by setting your desired periapsis during the transfer maneuver. By using the Oberth effect from the origin body, and sensitive dependence on initial conditions, you can easily adjust the eventual periapsis and inclination and then only have to make a single insertion burn during the flyby.

[GoSlash27]

If you really need to make an inclination change, you should do it at apoapsis, not periapsis. Inclination changes are cheaper at low speed.

Ideally, you would not need to do this, since you were careful to intercept in the desired plane in the first place...

Best,
-Slashy

 

[Draco T stand-up guy]

1 hour ago, GoSlash27 said:

If you really need to make an inclination change, you should do it at apoapsis, not periapsis.

To change inclination the best place is either of the Ascending or Descending nodes.

1 hour ago, GoSlash27 said:

Ideally, you would not need to do this, since you were careful to intercept in the desired plane in the first place...

Don't know about you but I find it impossible to do the really minor adjustments to a node at Kerbin to be sure of the intercept angle at Mun. Bodies further away get more difficult. This is why I use MehJeb but I do wish it would plan orbits for bodies that can be orbited rather than intercepts.

[GoSlash27]

5 minutes ago, Draco T stand-up guy said:

To change inclination the best place is either of the Ascending or Descending nodes.

This is true if you are trying to match an argument of right ascension. If you just want (say) a generic polar orbit, then you do the correction at the apoapsis of a barely- closed orbit where velocity is minimal. If you have to match a specific orbit, then it is indeed the ascending or descending node, whichever is closest to apoapsis.

9 minutes ago, Draco T stand-up guy said:

Don't know about you but I find it impossible to do the really minor adjustments to a node at Kerbin to be sure of the intercept angle at Mun. Bodies further away get more difficult.

Actually, I don't bother setting those up at the escape burn (although some do). I do it at the midcourse correction. It's much easier to set up there and it's cheap.

Best,
-Slashy

[Fireheart318]

On 5/7/2016 at 0:32 PM, Pecan said:

Are you aware there is a tutorials sub-forum?

Nope! I'l move it when I'm not in a class. Or at least try to

[JoeNapalm]

 

 

Step 5: Revert to VAB

Step 6: Add solar panels

Step 7: Add more boosters

Step 8: ADD MORE BOOSTERS!!

 

 

-Jn-

 

[A35K]

I always change my inclination while still at Kerbin if possible, or somewhere in Solar orbit when crossing the AN or DN for that planet. Much less dV! I once spent almost an hour to set up my Eeloo encounter to arrive with a perfect trajectory (while my ship was still at Kerbin). Turns out maneuver nodes are really touchy at these distances...

[suicidejunkie]

I would say that step 2 should be best done during the midcourse correction, and then refined closer to when you enter the SoI.  The further away you are the cheaper it will be.  You may even need to thrust limit your RCS to 5% for precision.

 

If you've waited until you're already inside the SoI, then an inclination change is going to cost you dearly.

In most cases I expect it will be worth doing your capture burn on the equator slightly ahead or behind the PE, since that means your new AN/DN will be at the new AP, and be as cheap as possible while not losing much of the Oberth.

[Tourist]

Hmmm, "Best way to orbit a thing", I was always told the best way was to go around it really fast.... but not too fast or you'll orbit another thing.

[Vanamonde]

If you already know what the OP is sharing, that's swell. Now skip to the next thread without mocking his/her kindly attempt to share game knowledge. 

[Warzouz]

On 7/5/2016 at 4:39 PM, Fireheart318 said:

This tutorial will show you the best way to get into orbit around a celestial body - planet, moon, star, whatever. This tutorial assumes you've already got an encounter set up. The law of physics you'll be exploiting here is called the Oberth Effect and it's EXTREMELY efficient!

Step 1: Burn retrograde at periapsis until you're in orbit. STOP AS SOON AS THIS HAPPENS!!!

Step 2: Now's the time to make any inclination changes - you probably want an orbit along the equator - an equatorial orbit. Make a maneuver node at the equator and adjust accordingly. This is really only useful for a few bodies - Moho, Gilly, Minmus, Dres, and Bob. I'm probably forgetting one.

Step 3: Burn retrograde at apoapsis until your periapsis reaches the desired altitude.

Step 4: Burn retrograde at periapsis until your apoapsis reaches the desired altitude.

 

That's pretty much all I've got to say so Fireheart318 out!

I would suggest to tweak your periaps FIRST by burning radial IN when you enter SOI. It's usually very cheap and will save you one manoeuvre later.

As for the inclination change you should say that there is two locations to do it and you must select the one farther from the body you orbit.

If you want to match a satellite orbit of do a rendezvous, you should prepare to optimize your inclination change burn. This is usually very costly.

• Adjust your PE so you match your target orbit (except if the target PE is in high orbit, then you should favor the obert effect)
• Set a node around PE and go to an elliptic orbit BUT try to push the ascending or descending node far from the body. For that, you may want to burn before or after PE. This is less efficient, but if your AN/DN are near the body, you'll loose MUCH more when you'll have to do the inclination change.
• Line up AN/DN with target. If indicators don't show, line the map view so both orbits become lines. The point they intersect is AN of DN. Put a node there and check it's the farther away.
• When you burn is done, you only have to match orbit or do the rendez-vous.

 

[NikkyD]

You do know that Oberth cannot be exploited as it is merely an observational (mathematical) phenomenon ?!

[Warzouz]

25 minutes ago, NikkyD said:

You do know that Oberth cannot be exploited as it is merely an observational (mathematical) phenomenon ?!

Well, that's semantic.

Imagine you want to arrive at Duna and want an orbit around 1000km.

• Option 1 : Set your PE at 1000km and retro burn until you AP is around 1000km too
• Option 2 : Set your PE at 60km and retro burn until your AP is 1000km then at AP burn prograde until your circularize at 1000km.

Options 2 is less expensive in dV due to Oberth effect. We could say we "exploit" the Oberth effect.

[FlyingPete]

16 hours ago, Tourist said:

Hmmm, "Best way to orbit a thing", I was always told the best way was to go around it really fast.... but not too fast or you'll orbit another thing.

And if you go fast enough, eventually you'll be far enough out that you won't orbit anything. Or you'll end up in the stomach of a Space Kraken Thing.