Laythe landing tips

[Warzouz]

I'm planning a my first landing on Laythe

My station is at 500km from laythe. My laythe lander is a 16T rocket based SSTO which should be able to do the round trip. 2 basic jet engines and a LV30. I've added some small chutes to help reducing speed (I'll still need a boost to avoir crashing). I've tested it on Kerbin.

As my initial option was to place the station at 70km. But I've decided to set up at 500km. I think I'll use one of my tugs to truck the lander to a lower orbit, then try to land

My question : how do I manage to avoid falling into the water (my SSTO is not a plane) ? Is it better to start at low circular orbit and horizontal aerobrake or should I start on an eliptic orbit and drop form high altitude ?

For now I don't car too much where I land on Kerbin and where I went to Duna, there was no problem either.

Any insight ?

Edited April 3, 2015 by Warzouz

[Starhawk]

You're probably better off starting in a low orbit. If you have less velocity to shed, it should be easier to choose a landing site.

That said, Laythe is tricky because there's so little land.

Mechjeb has a fairly good atmospheric landing prediction tool.

Good luck, and happy landings!

[McPoisoned]

There is a mod that gives you atmospheric Predictions which might help avoiding the water http://forum.kerbalspaceprogram.com/threads/104694-0-90-Trajectories-v1-1-3-(2015-01-25)-atmospheric-predictions

[Deutherius]

I find it hard to predict just how much the atmosphere will alter my trajectory, so I would probably drop straight from the 500 km orbit. It will cost less dV to deorbit and it will be easier to pinpoint a landing location (less atmo to go through), given that you take into account Laythe's rotation. The atmosphere should be thick enough to slow you down, especially with chutes.

I'd also advise you against using the simple jets, as 2 turbojets would easily have enough thrust to take off and would provide superior performance in getting to orbit. But that's a little OT as you are already there

[Xannari Ferrows]

Laythe's atmosphere is slightly thicker than Kerbins', so if parachutes work on Kerbin, than they are the way to go.

That said, even my landers still need a bit of a powered landing, but generally that isn't helpful over water, so...

If you can intersect on an inclined trajectory, I'd say take it. You'll be covering a much larger area, and it'll be easier to find a landing site. The parameters of your orbit change how you'll land on that target drastically. There's no real guideline.

[celem]

When it comes to touching down on land and not water then I usually use Kerbin as a benchmark for Laythe designs. Kerbins atmosphere starts a bit higher, but isnt quite as thick, so overall a craft follows a similar trajectory on both bodies. I tend to deorbit about 100-110 degrees before my desired touchdown, the exact angle depends on the drag of the design and the starting altitude, but practice on Kerbin as mentioned. If you can deorbit and have things parachute onto KSC then you ought to be able to hit a Laythe landmass.

Bombing in from an elliptical orbit makes hitting the spot even simpler, but means more of a suicide burn to kill the velocity you pick up in freefall. Since you have chutes and jet engines for the softland, I wouldnt think the extra dV would be particularly high.

[StrandedonEarth]

Dropping straight down is still tricky because the moon still rotates. Then again, I heard Laythe is tidally locked to Jool, but it would still rotate a little. Watch out for that!

I like the Trajectories mod for landing predictions.

[Warzouz]

I did it with a medium strategy. I was doing some aerobraking, but my 3 orbit drove me in the water during the night... Then I tried after 2 aerobraking a classical retrograde to fall on an island.

Touch down !

I managed to get to 500km orbit and rendez-vous orbit wih the station.

[Warzouz]

By the way, how to splash without destroying the ship ?

[falloutaddict]

By the way, how to splash without destroying the ship ?

Go very slowly, like less the 7m/s slowly. Make sure all your joints are reinforced so they dont rip apart

[Starhawk]

By the way, how to splash without destroying the ship ?

Strangely, you have to hit the liquid more slowly than you would hit solid ground if you want the craft to survive. One of the quirks of the physics engine.

Happy landings!

[EdFred]

The Trajectories mod still doesn't work for me when using FAR. The error on it is still enough to miss the little bit of land on Laythe.

So I dumped FAR and Trajectories.

[RexKramer]

Laythe's atmosphere is slightly thicker than Kerbins', so if parachutes work on Kerbin, than they are the way to go.

Actually, Laythe's atmosphere is thinner than Kerbin's, so parachutes are slightly less effective. However, the surface gravity is also less on Laythe, so if chutes work on Kerbin, they probably will work ok on Laythe also.

Even though your lander is not a plane, your jets may be able to help steer you towards land if your trajectory takes you close to land.

- - - Updated - - -

I generally take SSTOs with wings to Laythe, but here's a strategy which worked before I started doing that:

First, this requires a lander which will float upright in water. You don't need wings, but need to be able to launch vertically from water. You'll need an engineer on board also.

Enter the atmosphere in a way that you think will get you to land on land. I'm not too good at that, and usually end up in the water, but close to land. Usually you can get within a few hundred km at least.

Use parachutes and jet engines if needed to land softly in the water.

Repack your chutes. Make sure you have a way for a kerbal to get back aboard the ship if he falls into the water. Or make sure he doesn't fall off..

Assess which direction the nearest land is. Launch, using your jet engines, and head that way. This time, when you pass over your intended landing zone, you are going slower, and at a lower altitude, much easier to hit your target.

That's worked pretty well for me.

[Warzouz]

OK, thx for the advices. Last week, my first attempt to land on dryland finished in a splash by night (because of a too adventurous third aerobraking), but my ship dislocated. I'll retry at very low speed. But I'm not sure the ship will stay upward.

My 2 chutes are too small to slow the ship correctly (that was expected). but it manages to drop at 25m/s. I've only to fine tune the speed to than 7m/s.

I think that this low speed is because the landing struts have no effects and non suspension. So the impact speed is dealt to each parts. The water should act as a natural suspension.

On Tylo, I hit the ground at 30m/s (no more fuel) with the medium landing trust and it did well (not even bouncing).

[Warzouz]

I succeeded, but the ship tilted into the water. I wasn't able to raise it and it blew when I started the engines.

I use to cut the SAS on landing (to avoid wobbling), maybe I could let it on. I could try to move fuel, but most of my tanks are quite high.

[Mister Dilsby]

I heard Laythe is tidally locked to Jool, but it would still rotate a little. Watch out for that!

Careful now--I believe it does rotate, but its rotation period is the same as its orbital period such that it always points the same face to Jool as it goes.

[Deutherius]

Careful now--I believe it does rotate, but its rotation period is the same as its orbital period such that it always points the same face to Jool as it goes.

Correct - if it didn't rotate, it wouldn't be tidally locked. Laythe's orbit is also perfectly circular, so it wouldn't even "wobble" like e.g. Ike would when viewed from Duna.

I have actually never heard of any celestial body that wouldn't rotate around its own axis, however slowly - is it even possible? I would intuitively think that it is not, due to conservation of momentum acting in the process of formation of said celestial body.

[Warzouz]

What is best way to return from Laythe to Kerbin ? Do I park in a Jool orbit first to wait for the window ? whch orbit ?

I opted for as 85000km orbit aaround Jool (above Tylo, near Bop). I hesitate to go under Laythe Orbit to profit from Oberth effect, but I found silly to use escape velocity burn to go lower as I could go higher.

Have I done correctly ?

[Deutherius]

What is best way to return from Laythe to Kerbin ? Do I park in a Jool orbit first to wait for the window ? whch orbit ?

I opted for as 85000km orbit aaround Jool (above Tylo, near Bop). I hesitate to go under Laythe Orbit to profit from Oberth effect, but I found silly to use escape velocity burn to go lower as I could go higher.

Have I done correctly ?

There is no "best" way to do it. If you have the dV, you can consider the most direct approach to be the best one. If your dV budget is tight, you might want to use Jool's moons to your advantage.

I am by no means an expert on the Joolian system, but I would probably wait in Laythe orbit and try to get a Laythe->Tylo->Kerbin assist, possibly incorporating Vall in the process. You can also get to Pol, wait for the optimal window, lower your jool Pe to just above the atmo (which is not going to cost much) and then just burn at Pe to escape Jool with some nice Oberth effect exploitation. Bonus points for combining both

[Warzouz]

I understand the concept or gravity assist but I don't know how to use it. I clearly saw that passing behing tylo would nealy make me escape from Jool SOI. But as the trajectory stops at Tylo SOI excape, I don't see where I go then.

Even though, this seems to be very tricky to have an encounter with Kerbin, Tylo should be in the correct spot while beeing in the correct spot to escape Laythe WHILE beeing in the correct phase angle. It sound not easy...

[Starhawk]

I understand the concept or gravity assist but I don't know how to use it. I clearly saw that passing behing tylo would nealy make me escape from Jool SOI. But as the trajectory stops at Tylo SOI excape, I don't see where I go then.

Even though, this seems to be very tricky to have an encounter with Kerbin, Tylo should be in the correct spot while beeing in the correct spot to escape Laythe WHILE beeing in the correct phase angle. It sound not easy...

In the settings.cfg file in your KSP install folder, there is a value called CONIC_PATCH_LIMIT. This determines the number of SOI changes through which the trajectory will be drawn. If you increase it beyond the default of three, you can plan maneuvers that involve several SOI changes.

I have successfully used Tylo to save several hundred m/s returning to Kerbin from Laythe. It's definitely tricky, but doable.

Happy landings!

[Deutherius]

I understand the concept or gravity assist but I don't know how to use it. I clearly saw that passing behing tylo would nealy make me escape from Jool SOI. But as the trajectory stops at Tylo SOI excape, I don't see where I go then.

Go to the folder where you have KSP installed. Open the file "settings.cfg" with notepad or something similar. Find the line that says "CONIC_PATCH_LIMIT" and change the value to something higher. This will cause the game to calculate your trajectory through more SOI changes - I use 4 for example, but for chaining gravity assists you will probably need more. Be advised that higher numbers cause the calculations to be more demanding, and the trajectories after about 3 or 4 SOI changes tend to be slightly inaccurate. You will likely have expend some dV to correct for this, but it's usually worth it.

Even though, this seems to be very tricky to have an encounter with Kerbin, Tylo should be in the correct spot while beeing in the correct spot to escape Laythe WHILE beeing in the correct phase angle. It sound not easy...

Yes, timing gravity assists, especially chaining them, is not a trivial matter. That's why I also gave you the option with Pol It can be done, though.

There are plenty tutorials on gravity assist if you're interested, just search

[Warzouz]

Thx I'll do.