dv for Tylo and Laythe lander.

[Kasuha]

Still, "a few units of fuel", while technically more efficient, doesn't seem like a significant difference given the huge amount you need at Tylo anyway.

Once again, the difference is in how easy is to execute it. The small difference only exists if you manage to perform perfect suicide burn. If you don't end right above the surface, you're going to spend not a few units but a whole lot of extra fuel to brake the fall.

Designing Tylo landers is sort of a hobby of mine. I keep making new ones, HyperEditing them out there, and seeing how they work. With each new design, the testing process is to start from an orbit just above the mountains and see what happens. If it goes splat, I raise the orbit a bit and try again, repeat, until I can get it down safely. I have yet to succeed in landing from any starting altitude less than 175km and 200km seems to be the "sweet spot" for most designs.

My first Tylo landing ever started on 50 km orbit and it was a lander with <1 initial TWR (not my design, OP was curious if it is possible to land and return on Tylo with it). For my own missions I used 65 km orbit because it allows higher time warp and is still reasonably low.

However, this has always been from a circular orbit. I've never considered starting from the Pe of an eccentric orbit but now that I am, it seems to me this would require very careful planning to get any benefit. The greater your eccentricity, the faster you're going at Pe compared to a circular orbit at that altitude, so the more horizontal speed you have to kill off and the more fuel that requires.

I start from circular orbit too, lowering periapsis to ~10 km is the initial landing maneuver. Taking Tylo diameter into account I think orbit with Ap=65 km and Pe=10 km can't be considered any significantly eccentric.

Yes, your horizontal speed at Pe is higher than at Ap, but the difference is smaller than the velocity you gain by freefall from 65 to 10 km. Thus it also takes less fuel to kill.

I used this landing method just today to do a pinpoint landing on Tylo's South pole (landed 350 m from it). This method is not very good for pinpoint landings so it took a few tries. I can give you the quicksaves I used for it if you're interested to check where I was at which point and eventually try it out yourself.

Is the argument about suicide burn you had with Kosmo-not documented in posts here somewhere? I would like to have a look at it if possible.

Yes, it is in this thread. I admit my defeat in this post.

I am a believer since then

Edited November 29, 2013 by Kasuha

[Nao]

Yes, it is in this thread. I admit my defeat in this post.

I am a believer since then

Ohhh i remember that thread, I was searching for it the other day, I'll bookmark it now. Thanks!

I don't really find this more efficient. It costs about 3100m/s to land on Tylo no matter how you slice it. The lower you are, the more horizontal speed you have to kill off. The higher you are, the more you fight gravity all the way down. But it ends up more or less a wash in practice. I find it easier to land at or near a specific spot starting higher, but you've got a long time to worry about whether you're keeping your vertical speed under control. Starting low with an upwards vertical velocity takes away some of the anxiety about vertical speed but I find I have little if any control over where exactly I land.

Hmm i took a copy of OP's craft for the spin earlier, and from 8km orbit it took only 2450m/s dV to land on Tylo (almost made ascent with rest of fuel). And landing on exact spot from low orbit isn't that hard if you have more than 1.5 TWR and do some math beforehad. Even as simple as starting the burn Xseconds before reaching target where X = orbitalspeed/inital acceleration/2 have got me landed ~1km from target spot (center of 8km dia. crater) using only 50m/s dV more (2450). And i didn't landed on tylo since 0.18patch i think.

edit: yay 404th post

Edited November 30, 2013 by Nao

[SSSPutnik]

Oh, so my craft wouldn't make it? Even if I landed at 6km height?

(And return to orbit of course).

[Kasuha]

Since I already spent time preparing them, here are my quicksaves if anyone wants to try.

The lander's task was also to dump some empty fuel tanks on the ground, these can be staged as soon as you enter suborbital trajectory. The descent part has three stages - dump the "cargo", dump supplementary fuel tank, and dump braking engines. You shouldn't spend much fuel after dumping these as what remains is primarily intended for ascent.

The lander has its issues, I had to retract landing legs and decouple first ascent stage to be able to get my Kerbals out of the pod (and then back in). It still made it safely back to orbit with one pair of tanks full and one half full.

There are five quicksaves in the zip:

1 - on initial orbit before periapsis reduction

2 - right before periapsis, ready for braking phase

3 - braking phase initiated, "cargo" decoupled to crash into terrain

4 - end of braking phase

5 - landed

To try them, start a new sandbox game, unzip the file into that directory, copy/rename individual files to quicksave.sfs and quickload.

The lander (without the "cargo") has initial TWR just above 1 on Kerbin. The design is "guesstimated" as I don't use mods so it is probably not as efficient as it could be.

Edited November 30, 2013 by Kasuha

[Nao]

Oh, so my craft wouldn't make it? Even if I landed at 6km height?

(And return to orbit of course).

You are short ~150m/s dV from near perfect landing on and ascent from Tylo's highest mountain (11km)

But seriously take a lander with at least 6000-7000 m/s dV and consider staging some of the parts (empty fuel tanks, lander legs, parachutes etc.).

[SSSPutnik]

Can't stage.. I need to land on all moons.

However, I can carry two landers. Possible I can use staging for Tylo and Laythe, the other moons, I can land on more easily minus the stages.

I designed a new lander, testing it now, no staging with 5896 deltaV. TWR 0.92

However it uses KW rocketry mod engines and tanks.

Another revision: 6106 dV and TWR: 0.83

Craft file.

https://moc-per.micromine.com/owncloud/public.php?service=files&t=232e8ffe3b1b4d2209171db98bd9a22c

Screenshot.

https://moc-per.micromine.com/owncloud/public.php?service=files&t=93b38b2c80bf3bd698b6a24cf8c059fd

Edited November 30, 2013 by SSSPutnik

[Kasuha]

Laythe can be done without staging, I used the following design for it:

It's good enough for any Jool moon except Tylo. However that was in 0.21, now I would recommend to put the landing gear a bit lower (slant girders a bit) to prevent scratching the bottom docking port off the lander.

[Xzabath]

If you take a kethane pack you can cut your dV in half for tylo I think it was about 3k needed, refuel on surface and head up. (if you mod)

[Nao]

Can't stage.. I need to land on all moons.

However, I can carry two landers. Possible I can use staging for Tylo and Laythe, the other moons, I can land on more easily minus the stages.

As Tylo takes the biggest amount of dV to land, you can actually place it last in order of your Jool exploration and stage the rocket there.

There is also another idea: design a smaller lander with 3000-4000m/s dV and just attach "booster stage" with docking ports when landing at Tylo. Doing it this way you could further reduce the basic lander dV and place parachutes on the booster stages for Laythe landing (without staging them there), this could potentially save you a lot of fuel on hauling the extra weight around the smaller moons.