Landing on the mun.

[Skorpychan]

So, I tried to land a probe on the mun earlier, and it exploded. It was coming in at around 150 m/s, and mostly sideways. The legs snapped off, it rolled, and then it broke apart and blew up.

As I understand it from science, I need to come in vertically, so I can use the engine to slow me down properly. How do I get rid of enough orbital velocity to accomplish that?

Should I not try and land the engine and fuel tank that got me to the mun in the first place, and go for something smaller and lighter?

And how the hell do you get landing legs past a decent-size engine without using girders?

EDIT:

I think I got it now. I exploded again, but that's because I couldn't see the ground.

Is it necessary to get into a proper munar orbit first, before de-orbiting and landing?

Edited July 2, 2013 by Skorpychan

[kenbobo]

Ok. You put the legs right on the bottom of the fuel tank. for the landing legs. And what version?

[Skorpychan]

Current version. I don't know the numbers; it's on steam.

And putting them right on the bottom wouldn't get them past the engine. Should I use the http://wiki.kerbalspaceprogram.com/wiki/LV-909_Liquid_Fuel_Engine instead of the http://wiki.kerbalspaceprogram.com/wiki/LV-T30_Liquid_Fuel_Engine ?

And will the -909 have enough power to drop me into munar orbit in the first place?

[K^2]

On the nav ball, look for the prograde and retrograde markers. Simply point the ship at the retrograde marker and burn. This will slow you down both horizontally and vertically. Bring your speed down to about 5m/s, and you should have no trouble touching down.

Edit: LV-909 is a good engine for Mun landing, yes. If it's not enough thrust to get you to the Mun, add an extra stage with a larger engine.

[nimbim]

You start the burn to deorbit by pointing at the retrograde vector. You will see your retrograde vector moving upwards towards 90°, you keep pointing at the horizon (between the blue and orange part) relative to your retrograde vector, so it keeps moving upwards, you can follow it a bit on its way to keep the direction correct. Once the retrograde vector is somewhere between 80-90° you can start pointing straight up. Click on your velocity indicator to switch from orbital to surface speed. Kill horizontal velocity to get the retrograde indicator as close to 90° as you can, kill vertical velocity as needed. Good Luck

[Skorpychan]

Okay, I'll try that approach. More stages, de-orbit properly instead of just dropping out at an angle.

[dragoncannon]

While it's not the most efficient method, it can somethimes be useful to kill all or almost all of your horizontal velocity during your deorbit burn... then you must only control your vertical velocity... try not to touch down at more than 10 m/s... 5 m/s is better

[Sirrobert]

Use the L909 for in vaccum, way more efficient. Or Atomic motor would be even better, but you can't put that under the lander (to long for the landing legs)

[K^2]

While it's not the most efficient method, it can somethimes be useful to kill all or almost all of your horizontal velocity[...]

That will cost you a LOT of extra Delta-V. But for practicing landings, it might be a good approach.

[Skorpychan]

Use the L909 for in vaccum, way more efficient. Or Atomic motor would be even better, but you can't put that under the lander (to long for the landing legs)

A nuclear engine on the current lifter design has a whackload of fuel left by the time it hits mun orbit. (I sent a couple of test probes into orbit first)

It's a bit overkill, currently.

Maybe for a Minimus or interplanetary booster.

Okay! Landing attempt #2 proved three things:

1. The concept is sound.

2. Landing on the dark side of the mun is not recommended.

3. The altimeter is inaccurate.

I got down to about 60, 70 m/s, and what looked like a good 20k to go. Then I smashed into the ground suddenly, bounced, and exploded. Derp.

Still, the design is sound!

Edited July 1, 2013 by Skorpychan

[Motokid600]

I actually use a skipper engine to kill my horizontal velocity. But I do not follow the retrograde mark as it falls. I keep my ship pointed directly at the horizon until ALL my speed is gone and I'm falling straight down. I then jet that stage and land nice and soft with nukes. That method is amazing for landing within a 100m of a target. I find the nukes don't have enough thrust to kill the speed. It's fine if you have plenty of altitude, but if your under 15km forget it.

[Nasakev]

To condense what everyone in this thread is saying, you have two options. Once you are in a munar orbit:

1. Point retrograde and burn until you have a speed of 5 m/s or less, then maintain speed until landing. This bleeds off speed most efficiently, but is slightly more difficult as retrograde shifts as your velocity changes.

2. Kill your horizontal velocity first, then point straight up and burn to about 5 m/s and maintain speed until landing. This costs a bit more delta-v, but is easier to control as you don't have to worry about horizontal velocity as you descend.

Another thing to remember: the altitude given on the top of the screen is not necessarily exactly how far you are from the ground- it's how far you are from that planet/moon's version of sea level. The actual ground might be much higher than that. Minmus, for example, has areas with surface over 5 km above sea level.

[Mr. Scruffy]

[...]

I got down to about 60, 70 m/s, and what looked like a good 20k to go. Then I smashed into the ground suddenly, bounced, and exploded. Derp.

Still, the design is sound!

Yeah sound like ´boom´ - ;D

[capi3101]

Another thing to remember: the altitude given on the top of the screen is not necessarily exactly how far you are from the ground- it's how far you are from that planet/moon's version of sea level. The actual ground might be much higher than that. Minmus, for example, has areas with surface over 5 km above sea level.

If you've got a manned lander, the best way to iron out any ambiguities in the matter of "how far to the ground" is to go IVA and look for the radar altimeter. It's the gauge that looks like this:

Yours will be in meters, of course. While you're landing, go IVA every now and again and wait for the needle to start moving. When it does, read the guage; you know at that point you're at least that far above the ground and can figure out the ground's elevation (or at least make an educated guess). That'll let you know how much time you've got before you absolutely have to have your speed down below 10 m/s.

[Danger2007]

I've built my excursion vehicle with a single Poodle and the KW Rocketry SB-1 LFT. If the tank is full on decent, and your not tooo thirsty with the engine you should be able to make it back to Kerbin.

[Horn Brain]

Put a light on the side of your vehicle pointing down and turn it on when you're landing. It makes judging the distance to the ground super easy during the last two hundred meters or so. Don't forget to provide power, though.

[Mr. Scruffy]

...which leaves but a few options on the dark side (the real one) of the mün.

[Skorpychan]

Put a light on the side of your vehicle pointing down and turn it on when you're landing. It makes judging the distance to the ground super easy during the last two hundred meters or so. Don't forget to provide power, though.

It had a ring of downward-pointing lights. Falling as I was, with the altimeter showing 25k to the ground, I wasn't looking out for it.

PsshhhhhWHAM

[Horn Brain]

It had a ring of downward-pointing lights. Falling as I was, with the altimeter showing 25k to the ground, I wasn't looking out for it.

PsshhhhhWHAM

If it said 25km to the ground and you hit the ground, you either read the altimeter wrong or you found a bug. It probably said 2.5km to the ground. The Mun's elevation is usually around that high, up to about 4km near the poles.

[Skorpychan]

I found something, that's for sure...

Tried again today. frakked up majorly by not turning the RCS on for the de-orbit burn, and de-orbited straight into the mun. Ran out of fuel on the way down, but saw the ground coming this time for all the good it did.

Within the week, I shall have it.

[Loafcake]

Sorry for being off-topic...but, does anyone know approximately how long it takes the mods to review a post and approve it before it gets posted?

[Depends how tired we are - Moderator Comment]

[Skorpychan]

How long is a piece of string?

Keep posting and contributing, it'll wear off.

[troyn123]

Another tip: When caps-lock is on, the controls are in "fine" mode, and will do smaller inputs. Can make it a lot easier to stay on your retrograde marker once you're close to it.

[Skorpychan]

Does that work with the throttle as well?

[Pugspaceprogram]

Does that work with the throttle as well?

Sadly not, that is for you to figure out yourself.