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RocketBlam

Entering Laythe Retrograde

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So, I found myself FINALLY in Jool orbit with my space plane, and getting ready to enter a Laythe orbit. To my consternation, I found myself orbiting Jool the opposite direction that Laythe was (which I believe is called Retrograde). This makes entering orbit around Laythe difficult, because it's orbital speed is added to yours. I tried a few times but I just couldn't burn enough to circularize the orbit around Laythe, or even come close. So I knew I had to use aerobraking.

After a few trial and error attempts, I set up a periapsis of 18,000 meters above Laythe. This altitude will brake you right into orbit, with an apoapsis of about 600,000 meters. So if you find yourself in that situation, that's the magic number for a retrograde entry into Laythe orbit.

Also, remember to pull in your solar panels. :)

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ugh thats the worst. especially when your mission is to any of the other non atmosphere moons. i can never enter joolian orbit the right way.

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When I did this, I overshot to around 12000m, then quicksaved just outside atmo.

After many hercuean tries, I managed to pull off a complicated chain of micromanagement (including uneven fuel pumping while engines were running) to pull out of a crash, using some of the original kerbin circularization engines that were still attached but unfueled. It is now in Layth orbit waiting for a rescue mission. :P

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To be sure you are going to get into orbit around a planet in the correct direction, use conics mode 0 (zero) instead of the usual conics mode 3. You can edit the conics patch draw mode in the setting.cfg file (that's the hard and inconvenient way), or you can install the Precise Node mod (it lets you change the conics mode on the fly, along with its other uses).

In the image below, I am tweaking that maneuver node that's far off in the background while I'm focused in on the Jool system where conics mode 0 is showing my trajectory as it will be relative to Jool. Come in counterclockwise. Adjust the radial component of your maneuver node to change what side the trajectory comes in on, and adjust the normal component to make sure it is in the equatorial plane.

86pJBhO.jpg

Precise Node also has the oh-so-nice feature that pressing the "o" key will reopen your maneuver node when it annoyingly collapses closed. You can also tweak the burn component values directly instead of pulling on the maneuver node thingies.

I SOOOOO love the Precise Node mod… and I hope Squad implements something like it in the stock game.

Edited by Brotoro

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nIfsCPy.png

Here's the space plane in question. It does a great job flying around Laythe and landing on its tail. Sadly, it just doesn't have the Delta-V to get back into orbit, so I guess Bill Kerman is stuck there for a while. Jebediah is in an orbit around Jool that is perpendicular to all the planets - north-south, that is. Not sure what's going to happen with him.

Edited by RocketBlam

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[snip]

Here's the space plane in question. It does a great job flying around Laythe and landing on its tail. Sadly, it just doesn't have the Delta-V to get back into orbit, so I guess Bill Kerman is stuck there for a while. Jebediah is in an orbit around Jool that is perpendicular to all the planets - north-south, that is. Not sure what's going to happen with him.

May I recommend a probe-controlled VTOL for the rescue? It comes with a re-usable interplanetary frame, and should be quite fun to rescue Bill with :)

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

Here's the space plane in question. It does a great job flying around Laythe and landing on its tail. Sadly, it just doesn't have the Delta-V to get back into orbit, so I guess Bill Kerman is stuck there for a while. Jebediah is in an orbit around Jool that is perpendicular to all the planets - north-south, that is. Not sure what's going to happen with him.

I have 3 kerbals stranded on Laythe for about 8 years now. I'm sending the 6th rescue mission in the next transfer window.

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Come to think of it, how effective your aero braking is will probably depend on how much drag your vehicle has. My space plane probably had fairly little.

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My last Laythe aerobrake required dipping down to 17,600m to get into orbit. Always depends on your approach angle and speed. Took so much trial and error I'm surprised I didn't wear out my f5 and f9 keys.

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It would really be nice if Squad accounted for aerobraking effects in their trajectory predictions. It's one of the things I do use MechJeb for (since the f5/f9 alternative I used previously was just silly).

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Did my first Laythe landing yesterday.

First time I set my aerobrake at 30km... Nope, barely slowed down at all.

Second time around set it at 20km... Nope, my spaceplane decided to rip apart and slam into my interplanetary stage.

Third time the charm, set to 25km and got a nice orbit. (this was all using FAR by the way)

Oh and if you find yourself getting a Jool intercept going retrograde, just do a correction burn as soon as you're in Jool's SOI. I think it only took me 100-150m/s of DeltaV to change from a retro to prograde from the edge of the SOI.

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Try entering laythe's atmosphere retrograde travelling at 100km/s (K-drive test) according to the aerobrake calculator in order to slow down in order to orbit I had to have a negative periapisis, so I turned around and went to dres instead (K-drives are good at <1 day interplanetary travel)

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ugh thats the worst. especially when your mission is to any of the other non atmosphere moons. i can never enter joolian orbit the right way.

Fine tune your approach so that you absolutely *nail* Jool's orbital inclination, and get your periapsis down to zero.

When you enter Jool's SOI, burn at 90º to give you the preferred direction of orbit.

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Try this online calculator.

I've been aerobraking a lot of ships direct at Laythe (some on intercept from Dres instead of Kerbin) and the difference in initial speed at Jool intercept / at Laythe intercept / at Laythe atmosphere intercept can be very high depending on the precise transfer you've used, meaning the aerobraking height can also be very different. There's no single set height to use.

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