What do you think about my unkerballed Mun landing

[Pawelk198604]

Sorry for no voice it's some wrong with shadowplay :-(

I wanted to make sample return, but i have to little delta-v to make it

Fortunately i equipped the probe with antenna, for such eventuality

[GehringGame]

Oh man, it was teetering on the edge of tipping for a second there! Nicely done. Up next, a manned land and return!

[Guest]

FYI: You don't need a fairing for a payload that streamlined. If you put a few fins at the bottom of your central stage, you probably won't need all those ASAS modules either. You can use the weight you save to bring more fuel to the Mun, and bringing more fuel to the Mun will allow you to fly a return mission.

Good luck, and good video!

[Pawelk198604]

FYI: You don't need a fairing for a payload that streamlined. If you put a few fins at the bottom of your central stage, you probably won't need all those ASAS modules either. You can use the weight you save to bring more fuel to the Mun, and bringing more fuel to the Mun will allow you to fly a return mission.

Good luck, and good video!

Thanks, my previous attempt ware epic failure so i don't uploaded it to YouTube ;-)

I think it was because i tried to make apoapsis at 2000 km than try to circularize orbit and make periapsis at 20 or 40 km and try to land. Now i tried to gradually lower orbit first 2000 by 1000, than 600 by 300, than 300 by 100, and finally 40 by 40.

I thin i saved loot of fuel.

[Cairol]

Better outfit your lander with RCS. It really helps to get a smooth landing on low gravity bodies.

You had too much horizontal velocity on your first touch down. With RCS you could compensate without having to turn your rocket for each little correction.

Also: Try to build landers with less height to avoid tipping over when landing. And make them wider at the base instead.

It will be much more forgiving with a wide landing profile when landing with horizontal speed > 0.

[Pawelk198604]

Better outfit your lander with RCS. It really helps to get a smooth landing on low gravity bodies.

You had too much horizontal velocity on your first touch down. With RCS you could compensate without having to turn your rocket for each little correction.

Also: Try to build landers with less height to avoid tipping over when landing. And make them wider at the base instead.

It will be much more forgiving with a wide landing profile when landing with horizontal speed > 0.

Thanks for feedback next time i plan to make Simple lander with rcs without materiał bay only service bay with some equipment just to score sample return mission

[Sharpy]

Wait, how do you plan to pick up samples without a Kerbal?

Notes:

- that kind of staging isn't very efficient. The weight of extra engines (that are inactive) costs more during launch than you get back in reduced weight by not accelerating empty fuel tanks later on. If you replaced the middle engine (the one activated at 5:40) with a fuel tank of the same weight, you'd come out with more dV in the end. Dump empty tanks (attached radially) or radially attached engines with spent fuel tanks (asparagus staging). Keep in-line separation only when the weight of the stages differs a lot, or changes the character drastically (atmospheric engine vs low-thrust high-ISp vacuum).

- Late execution of maneuvers

- you put a lot of effort into circularizing your orbit, an effort that goes out the window the moment you burn for the Mun. Wasted effort, wasted dV. Calculating the encounter from any sloppy orbit is somewhat harder but costs only effort, not fuel.

- Poor encounter - a very distant one. By making the encounter periapsis much lower you save a lot of dV on orbital insertion thanks to Oberth effect, spending only marginally more in Kerbin orbit. That descent to low Munar orbit through so many maneuver nodes was sad - either launch into a very low periapsis, or correct your trajectory 1/3 the way away from Kerbin to Mun to make the fly-by very low - as low as 10km is good! Then just burn at the periapsis to (*roughly*) circularize. I estimate you'd use half the fuel you used for maneuvers of descent. (Remember: the Oberth effect works when you're moving fast. You're moving fast at periapsis of a very elongated orbit, or at a very near flyby, so make that periapsis low when all it costs is moving your node half a degree left or right or speedin up or down by 5m/s. By gradually decreasing the radius of a circular orbit all you did was wasting fuel, painstakingly avoiding the goods of Oberth effect.

- A lander this tall will be prone to tip over. Since you did use a fairing, you could have built your lander with two tanks with engines on the sides of the materials bay. (also remember, you can attach parts radially to a stack decoupler - in this case, two fuel tanks attached to the decoupler which would free the landing payload.) Wide, squat, legs wide apart (you can even tilt them so that they extend wider giving less clearance below!)

- You didn't lose horizontal speed during the landing. (a pretty foolproof method is to burn *retrograde*). You barely saved your craft when it hit at a sideways speed too high.

- You didn't brake with the engine after you rolled over and it pointed directly into retrograde direction.

- Nevertheless, with so little fuel, return is impossible, so there's no point landing upright. As long as you didn't lose any science equipment or the antenna, you can perform all your needed science while lying on the side.

- You have KER installed, but you don't use it. Things like horizontal speed or suicide burn time, they make the landing much easier.

Edited July 3, 2015 by Sharpy

[Pawelk198604]

Wait, how do you plan to pick up samples without a Kerbal?

Notes:

- that kind of staging isn't very efficient. The weight of extra engines (that are inactive) costs more during launch than you get back in reduced weight by not accelerating empty fuel tanks later on. If you replaced the middle engine (the one activated at 5:40) with a fuel tank of the same weight, you'd come out with more dV in the end. Dump empty tanks (attached radially) or radially attached engines with spent fuel tanks (asparagus staging). Keep in-line separation only when the weight of the stages differs a lot, or changes the character drastically (atmospheric engine vs low-thrust high-ISp vacuum).

- Late execution of maneuvers

- you put a lot of effort into circularizing your orbit, an effort that goes out the window the moment you burn for the Mun. Wasted effort, wasted dV. Calculating the encounter from any sloppy orbit is somewhat harder but costs only effort, not fuel.

- Poor encounter - a very distant one. By making the encounter periapsis much lower you save a lot of dV on orbital insertion thanks to Oberth effect, spending only marginally more in Kerbin orbit. That descent to low Munar orbit through so many maneuver nodes was sad - either launch into a very low periapsis, or correct your trajectory 1/3 the way away from Kerbin to Mun to make the fly-by very low - as low as 10km is good! Then just burn at the periapsis to (*roughly*) circularize. I estimate you'd use half the fuel you used for maneuvers of descent. (Remember: the Oberth effect works when you're moving fast. You're moving fast at periapsis of a very elongated orbit, or at a very near flyby, so make that periapsis low when all it costs is moving your node half a degree left or right or speedin up or down by 5m/s. By gradually decreasing the radius of a circular orbit all you did was wasting fuel, painstakingly avoiding the goods of Oberth effect.

- A lander this tall will be prone to tip over. Since you did use a fairing, you could have built your lander with two tanks with engines on the sides of the materials bay. (also remember, you can attach parts radially to a stack decoupler - in this case, two fuel tanks attached to the decoupler which would free the landing payload.) Wide, squat, legs wide apart (you can even tilt them so that they extend wider giving less clearance below!)

- You didn't lose horizontal speed during the landing. (a pretty foolproof method is to burn *retrograde*). You barely saved your craft when it hit at a sideways speed too high.

- You didn't brake with the engine after you rolled over and it pointed directly into retrograde direction.

- Nevertheless, with so little fuel, return is impossible, so there's no point landing upright. As long as you didn't lose any science equipment or the antenna, you can perform all your needed science while lying on the side.

- You have KER installed, but you don't use it. Things like horizontal speed or suicide burn time, they make the landing much easier.

Thanks, i tried but failed :-(