Landing on Tylo

[Warzouz]

Yep, I'm retrying from 30000, and aim for the highlands (I already visited the lowlands with my staged lander). further more, I miss 600m/s of dv tor each orbit...

Do you think I should go for 20000 or even 15000 ?

- - - Updated - - -

Ok starting at 30000, I kill my horizontal velocity keeping th vertical at -100m/s. At 200m/s horizontal, I switch to prograde. At 4000, swith to MJ autolanding. Did well, with 690m/s more fuel in tank. I landed using 3100m/s.

I landed in midlands at 1800m.

I tried keeping my vertical velocity around 170m/s, but I crashed. It was too fast, I couldn't kill my horizontal speed fast enough. -100 seems to be nice.

[Deutherius]

Ok starting at 30000, I kill my horizontal velocity keeping th vertical at -100m/s. At 200m/s horizontal, I switch to prograde. At 4000, swith to MJ autolanding. Did well, with 690m/s more fuel in tank. I landed using 3100m/s.

Landing on Tylo from 30 km orbit with 3100 m/s? I'd call that a success. Congratulations!

Do you think I should go for 20000 or even 15000 ?

I have no idea about your TWR values, so I don't know for sure - it sounds like you could squeeze more from your lander, though. I would even consider starting from 10k, lowering periapsis to be just over the land (landing at the equator, you are unlikely to be encountering land at altitudes >6600 m, most likely at the ~4 km region), and waiting for Pe to start the burn (when your vertical velocity is close to zero - and keep it that way, more or less) - as I said, the lower you end up after killing horizontal, the more dV you will save from gravity losses. Cutting it this close is risky, though, and will most likely kill you at least a few times Try to land for the higher ground (1800 m is really a bit low), if you can, for additional dV savings! And most of all, good luck

Edited April 10, 2015 by Deutherius

[Warzouz]

Take off successful. Final words

SSTO lander is a 14T fully loaded (7T dry) TWR is 1 (full) to 2.15 (empty) with 6050m/s dv. I started at 30000m. Used 3100m/s to land at 1800m. I used 2800m/s dv to return to orbit with only 150m/s of fuel left... Hopefully, the tug will do the rendez-vous.

BTW Mechjeb failed to ascend to orbit several times... I had to do it manually. I used MJ only for the final suicide burn on landing, under 4000m. Activating landing guidance higher WILL result in "divergent litho-bracking". Horizontal speed has to be handled under 200m/s before returning to retrograde.

I'm quite happy with this flight. I had a 5800m/s design before. Hopefully I optimized it to 6050 (mainly removing double science equipment). I still managed to do all the science on surface.

Time to return to the space station. Still one landing on Laythe, the back home with nearly 250 experiments on jool system !

[impyre]

Someone beat me to it. TWR *MUST* be greater than 1 ASL to even think about landing... otherwise you're fighting a losing battle with gravity (not a fight you want to lose) regardless of piloting. On a side note, if for whatever reason you find yourself in a similar situation again, you can always burn off some fuel to raise TWR (assuming you have fuel to spare).

Edited April 10, 2015 by impyre

[Warzouz]

Well, the vertical thrust must be greater than 1, but you can kill lateral with less than 1. As you burn fuel, the TWR rises and you'll be able to fight vertical velocity with a TWR higher than 1. The higher the TWR is the easier it is.

The parameters of the landing profile are

- Starting altitude (lower is better because you'll have less gravity to fight, but you have less margin to stop lateral speed)

- Starting TWR (lower means lateral velocity will take longer to kill)

- controlled vertical speed (I used -100m/s. If the TWR is lower, it should be smaller).

- dV of course : If you have a low TWR, you'll burn much more than with a higher TWR.

In theory, you could land and take off with 4500m/s dv, but that's with infinite TWR. With my starting TWR=1 , and 1.6 on ground, ending at 2.15, I burnt 5900m/s of dV. 31% loss because of that low TWR.

And finally, with low TWR, autopilots do a poor job it seems.

[Jouni]

Just don't take the wrong lesson from how bad the LV-N is under high gravity. The LV-N is the best lander engine to use for very low gravity bodies, and there's a number of those in KSP. Obviously, the TWR of the LV-N is much higher on low gravity bodies, so that's why it works well there. But it's HORRIBLE on Tylo.

If you want to build a reusable Tylo lander, nothing beats the LV-N. The payload fraction will be higher than with any other engine type, and you can also improve the efficiency by using the same engines for interplanetary transfers. Flying a low-TWR lander will be difficult, but that's an issue with player skills, not with the engine itself.

[Warzouz]

I'm not sure you can land any low TWR on Tylo. There is probably a lower limit. You must be able to control you vertical velocity as you horizontal speed is reducing. That require more and more TWR.

My 6000m/s DV SSTO for Tylo was meant to be reusable (thus I landed it only once, I was quite fed up with Joolian system.)

[seyss]

Just landed on Tylo! Used the very same rocket to get me from Kerbin to a low-orbit on Tylo, but with a new lander (LV-N, Rockomax X200-8, Mk1, and a little science rover topping it all), good for a 8m43s burn.. thanks everyone.

edit: pic

Edited April 17, 2015 by seyss

[Warzouz]

Well done !

[Mister Dilsby]

After a bunch of tries i finally managed a decent landing/ascent in one stage using the Constant Altitude method. I don't have a picture of the ship, but it's easy to describe: Mk1 lander can, Rocko-32 18 ton fuel tank, a little RCS and a medium gyro, 3x LV-N, and a few I-beams between the engines to allow the landing legs to mount low enough. Total dV is over 7000, TMR a bit less than 0.9 fully fueled.

Descent profile:

1. Begin 20km orbit
   
2. Burn retro to 2000m/s orbital velocity
   
3. Fall to ~12km
   
4. Begin firing engines to reduce vertical speed
   
5. Vertical velocity ~0 at 5km
   
6. Continue burning at 30 to 60 degree angle to horizon, keeping vertical velocity near zero while reducing horizontal
   
7. With horizontal velocity ~200-400 m/s and not seeing large mountains in the way, allow ship to begin falling
   
8. Continue reducing horizontal velocity while allowing vertical velocity of up to 50 m/s
   
9. At <1000m from ground, kill horizontal velocity and finish descent
   

Got to ground this way using about 2600m/s dV, no trouble ascending. I did have to practice the landing method several times though, it was a new skill for me.

[Warzouz]

Your lander seems heavier than mine. (14T fully loaded). Is it as SSTO or a staged lander ? Did you have a mothership or tug at 20km ?

[Warzouz]

BTW, this is my staged lander for Tylo

And my SSTO