Most fuel efficient way to get into a 120km circular Orbit?

[gta-man]

Hello! I just want to know this because i really dont know how to do a good circular orbit

[BlackBicycle]

1. Use MechJeb (accent autopilot for now) so that you only have to set the parameters, not to steer. Once you watched it do a run or two, you will know how it works. I recommend only leaving autothrottle on, the 'autostage' is redundant here, and the 'autowarp to apoapsis' will only skew your perception of what\'s happening. It\'s training, remember. To use it, install a mechjeb mod and add a mechjeb module from the 'command and control' (second) tab somewhere on the ship.

2. Head east (set heading 90deg/inclination zero deg (I prefer to set heading, but they are interchangeable), adds the 200 m/s Kerbin surface rotation speed for your craft.

3. If the craft has serious drag (deduced by looking at accent autopilot>stats in mechjeb), adjust the path (in the same autopulot>edit path) to pierce most of the atmosphere vertically before starting the roll. In my experience, with sleek rockets, i start a turn as low as 5km, and with really draggy ones at 15-20 km. Fuel works out well enough.

Soft landings to ya : )

[Cykyrios]

You can use MechJeb to get there automatically, and then analyze how it gets your rocket in orbit.

But the basics are:

- Climb vertically until 10-12km

- Begin gravity turn (slowly) and try to get a pitch of 0° before 60km (the atmosphere is so thin at this altitude, that it isn\'t worth pitching up anymore, plus you still have vertical velocity from launch)

- Burn heading East (for a 0° inclination) until your Apoapsis reaches 120 km, then let your rocket get there

- Start burning shortly before reaching Ap to get your Pe to the same altitude

E: Ninja\'d

[Knyght]

This is very rocket dependent. If your rocket is huge and Kerbaly then you probably won\'t be able to tilt with any stability until 20 or even 30K. Not sure exactly when the best case for efficiency tilt would start, I usually go for 20K, but I\'m no master of fuel economy.

[BlackBicycle]

If your rocket is huge and Kerbaly then you probably won\'t be able to tilt with any stability until 20 or even 30K

Wrong. Add more control surfaces.

[Knyght]

Pfft, that\'s cheating.

[BlackBicycle]

Excuse me? We are talking the range of 5-40 km here.

[gta-man]

1. Use MechJeb

2. Head east

3. If the craft has serious drag

Soft landings to ya : )

I dont want to use MechJeb, but thanks for the East tip!

You can use MechJeb to get there automatically, and then analyze how it gets your rocket in orbit.

But the basics are:

- Climb vertically until 10-12km

- Begin gravity turn (slowly) and try to get a pitch of 0° before 60km (the atmosphere is so thin at this altitude, that it isn\'t worth pitching up anymore, plus you still have vertical velocity from launch)

- Burn heading East (for a 0° inclination) until your Apoapsis reaches 120 km, then let your rocket get there

- Start burning shortly before reaching Ap to get your Pe to the same altitude

Tried that, didnt go well , i wasnt able to get Pe to the same altitude as Ap, infact my ship started to lose altitude really fast and got caught by the atmosphere.

This is very rocket dependent. If your rocket is huge and Kerbaly then you probably won\'t be able to tilt with any stability until 20 or even 30K. Not sure exactly when the best case for efficiency tilt would start, I usually go for 20K, but I\'m no master of fuel economy.

My ships are really small (i dont like to leave derbis) , For this orbit i will be using this ship:

[Knyght]

While you might think that that is really small (and compared to most rockets I see, it is) but if you\'really goinf fuel efficient, you can get into orbit and back with 3 or 4 tanks total.

That said, getting into a good orbit is mostly a factor of practice. Keep at it and see what works for you. Watch videos if that sort of thing helps you. If your orbit isn\'t circular, try this:

When your apo gets to the point you want it or a little over (125K or so maybe) cut off the engines, coast to apo and burn again. By the time you cut off your engines your orbit line on the map should look somewhat reasonable, ie. somewhat wide. If it\'s quite tall, you need to tilt more or earlier. I\'m not sure on the efficiency of this, but it\'s probably better than getting your orbit all screwed up. Your rocket has plenty fuel, I wouldn\'t worry too much about efficiency anyway if all you want to do with it is get into orbit.

[BlackBicycle]

If you don\'t want to use MechJeb, your choice. However, I\'d like to reiterate a point ion my post, that states: watch MechJeb do it a couple of times, then you can do it manually.

Or is it not me who is confused, but yourself? Did you already figure out your way of conquering space? There is a number, you know. Build a monster that can do anything. Build a medium which can do most of the stuff. Build a sufficient design, precisely tuned to the payloads you have in mind AND one that doesn\'t leave burned-out stages in low orbit? Which ones appeals more to you? Just go ahead.

[Cykyrios]

Tried that, didnt go well , i wasnt able to get Pe to the same altitude as Ap, infact my ship started to lose altitude really fast and got caught by the atmosphere.

If you want, you can post your .craft file, and I will make a short vid taking this rocket to orbit, so you can get the feeling when and how you can do each step.

[PakledHostage]

Hello! I just want to know this because i really dont know how to do a good circular orbit

Check out the Optimal Ascent Profile for this spacecraft challenge. That rocket can easily get you into a 75 km circular orbit. From there, it only takes about 70-80 m/s Delta-V to get up into a 120 km circular orbit. The guys on the challenge\'s leaderboard are reaching the 75 km circular orbit with about 400 m/s Delta-V to spare. Plenty for your purposes.

And while the pitchover altitude and angle will probably vary from rocket design to rocket design (the jury\'s still out on this point), the optimal pitchover altitude for the rocket in the challenge seems to be somewhere between 7500 m and 10000 m. There\'s a good video that was put together by jqhullekes that shows the challenge rocket reaching orbit with near record remaining fuel levels.

[gta-man]

Check out the Optimal Ascent Profile for this spacecraft challenge. That rocket can easily get you into a 75 km circular orbit. From there, it only takes about 70-80 m/s Delta-V to get up into a 120 km circular orbit. The guys on the challenge\'s leaderboard are reaching the 75 km circular orbit with about 400 m/s Delta-V to spare. Plenty for your purposes.

And while the pitchover altitude and angle will probably vary from rocket design to rocket design (the jury\'s still out on this point), the optimal pitchover altitude for the rocket in the challenge seems to be somewhere between 7500 m and 10000 m. There\'s a good video that was put together by jqhullekes that shows the challenge rocket reaching orbit with near record remaining fuel levels.

That is JUST what i wanted to see, this clears so much confusion, thanks!

If you want, you can post your .craft file, and I will make a short vid taking this rocket to orbit, so you can get the feeling when and how you can do each step.

Sorry Cykyrios , after seeing the video PakledHostage posted a link to, i see that you were right, i just got confused and did the Ap burn all in one shot, not in short bursts.

While you might think that that is really small (and compared to most rockets I see, it is) but if you\'really goinf fuel efficient, you can get into orbit and back with 3 or 4 tanks total.

That said, getting into a good orbit is mostly a factor of practice. Keep at it and see what works for you. Watch videos if that sort of thing helps you. If your orbit isn\'t circular, try this:

When your apo gets to the point you want it or a little over (125K or so maybe) cut off the engines, coast to apo and burn again. By the time you cut off your engines your orbit line on the map should look somewhat reasonable, ie. somewhat wide. If it\'s quite tall, you need to tilt more or earlier. I\'m not sure on the efficiency of this, but it\'s probably better than getting your orbit all screwed up. Your rocket has plenty fuel, I wouldn\'t worry too much about efficiency anyway if all you want to do with it is get into orbit.

Its kinda large because i want to do rendezvous with it (im new to rendezvous)

Thanks for the tips!

[hunter558]

Get up to 40k turn to 45 degrees, burn to 70k turn to 90 degrees, burn to 120k assuming you get orbit. Then go to the apoapsis and burn prograde to increase the periapsis until they begin to switch, just before they switch you should have a relatively circular orbit although it probably wont be exactly at 120k.