How to test landers

[martincmartin]

I'm about to make my first lander to land on the Mun.  Yay!  To test different designs, do I really need to launch each one from Kerbin and transfer to the Mun?  That's a lot of time before I get to the actual landing part.

[LordKael]

Well, you have a couple of options:

First: You can launch multiple landers at the same time, if you have the tech/skill to. That could potentially cut your launch count in half or even thirds.

Second: You can install a mod called "Hyperedit" which allows you to enter values for orbital conditions, and teleport your landers from the launch pad to Munar Orbit.

Third: You can use the tools in the VAB or SPH to show you the CoM and CoT. Look at these forums, and you can see the ideal placement for CoT vs. CoM. Essentially, what you're going for is a lander with 3-6 contact points spread relatively wide apart. From the contact point (landing gear, structural elements, or engines) to the CoM should probably less than a 45degree angle from the ground. 

 

In all honesty, Munar and Minmus landings are not terribly hard, and Minmus landings are extremely slow and require very little dV/fuel, so it might behove you to head there before tackling the Mun.

 

Best of luck, and if you want to post screenshots of your designs in this thread, I'd be happy to offer advice!

[Finox]

You could try practicing landings and take offs on Kerbin before you head out, actually its a pretty good idea just so you know how your lander will handle.   When I was getting ready for my first mission I also did some tests like seeing how long I could burn the lander engine at full throttle and determining how maneuverable my lander was.   Good luck with your mission!

[JacobT11]

For checking out maneuverability and burn times, I'll often do a full scale test on Kerbin. It's nowhere near accurate to the gravity or lack of atmosphere, but it definitely helps determine major issues with the craft before launching it. 

[Choctofliatrio2.0]

Screenshots could help us determine the best designs, and from there it's just trial and error

[Benoit Hage]

The only trick you may encounter is landing in a steep slope on the Mün. On Minmus, aim for one of the Flats, they are hard to miss.

If you have enough Thrust to Weight Ratio, (very little is needed on both satellite), try to design a lander that is more wide than tall. It will help a lot in case of that steep slope.

Beside, that... there is not much else to think about. Batteries in case you land on the dark side, some light and especially, a ladder! ( yes yes, don't laugh, it will happen to you one day )

Also, test on the launchpad to check if you Kerbals can use that ladder, sometimes the ladder is too short and can't get back inside their ship, or an engine gets in the way while descending.

Edited January 30, 2016 by Benoit Hage
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[Xavven]

25 minutes ago, Finox said:

You could try practicing landings and take offs on Kerbin before you head out, actually its a pretty good idea just so you know how your lander will handle.   When I was getting ready for my first mission I also did some tests like seeing how long I could burn the lander engine at full throttle and determining how maneuverable my lander was.   Good luck with your mission!

I second that! I like to test by initiating a hover on the launchpad, flying gently over to the flagpole, and making a smooth landing. Since Kerbin's gravity is higher, I usually switch out my LV-909's with LV-T45s just for the test, and make sure everything from attitude control to ladders and lights are working properly. Then I switch my LV-909s back in and head to the Mun!

Also, hovering in Kerbin's gravity takes a lot more skill than in Mun or Minmus gravity. If you can master your flight skills near the launch pad, Mun will be a piece of cake when you get there!

[Raptor9]

Piggy-backing on what @Finox said, you could do the Apollo 9 thing and launch to low Kerbin orbit and do some more tests there.  Look at your vacuum burn times, staging/action groups set correctly, etc.  And it will also let you practice rendezvous maneuvers if you plan on doing a Lunar Orbit Rendezvous method (Apollo command module waiting in Moon orbit).  Even though Apollo 9 launched on a full-up Saturn V, you don't necessarily have to do that in KSP for some Kerbin orbit tests.  You could easily launch your test lander on a much smaller rocket.

6 minutes ago, Xavven said:

I second that! I like to test by initiating a hover on the launchpad, flying gently over to the flagpole, and making a smooth landing. Since Kerbin's gravity is higher, I usually switch out my LV-909's with LV-T45s just for the test, and make sure everything from attitude control to ladders and lights are working properly. Then I switch my LV-909s back in and head to the Mun!

Also, hovering in Kerbin's gravity takes a lot more skill than in Mun or Minmus gravity. If you can master your flight skills near the launch pad, Mun will be a piece of cake when you get there!

This!

Edited January 30, 2016 by Raptor9

[Fearless Son]

I would like to add a little advice on top of what has already been said.  

If your lander does not have its axis of thrust parallel to the airless surface you are landing on, you are likely going to encounter some difficulty.  An unstable design might flip over, and even a stable design might "pirouette" on a landing leg a bit if it lands on it funky.  At the same time, the craft needs to have its lateral velocity close to nothing for many of the same reasons: lateral movement can cause it to flip on touchdown, and given how low gravity those bodies are, that can be easier to do than on Kerbin.  

Hence, I would advise you to have a bit of a reaction-control system on the lander.  Not a lot, just enough.  Thrusting the engine parallel to the surface is important to arrest lateral velocity, but it forces you to change the entire craft's orientation, which means you cannot see exactly where your prograde marker ends up on the navball until you rotate back again.  This will get you close, but not perfectly, into a direct descent.  The problem is that as you get closer to the surface, your need to keep the direction of thrust downward grows more urgent, which means correcting your descent direction by rotating the craft gets risky.  This is where the RCS comes in.  While falling downward with the craft pointed perpendicular to the surface, you can use the RCS translation controls to fine-tune your prograde vector until it is lined up with the axis of the craft.  

This in turn will allow you a much safer, less stressful landing (just so long as you avoid steep crater and canyon slopes.)

[katateochi]

51 minutes ago, Finox said:

You could try practicing landings and take offs on Kerbin before you head out, actually its a pretty good idea just so you know how your lander will handle.   When I was getting ready for my first mission I also did some tests like seeing how long I could burn the lander engine at full throttle and determining how maneuverable my lander was.   Good luck with your mission!

which isn't so different to how NASA do some tests; - https://www.youtube.com/watch?v=LM1wjs5nWXQ 
(somewhere I've got an accompanying video of my dog being really concerned by the sounds that Morpheus lander makes shorly after crash!)

 

[Perry Apsis]

I consider Hyperedit essential. NASA has physics simulations for developing ships, why shouldn't I? I'm building a lander for Laythe right now, and I'm teleporting it to orbit or even to the surface for testing. Of course, I revert to the VAB after each test. Once it's working, I'll do a real one.

[Hysterrics]

As previously suggested, HyperEdit will work to figure out how well your lander will work.

Me? I go all out Kerbal. I just build it and fly* it.

 

*Doesn't always fly

 

[Mikki]

@martincmartin

i use to test landers and vehicle drops in the western desert, since i refuse to play with hyperedit:

[Mighty1]

i use Kerbal construction time mod. it has a feature that, before you build your ship you can simulate it providing you already visited the desired SOI. In other words you can simulate on the mun, duna etc only if one of your craft visited the Soi of it.

[RizzoTheRat]

Re. Comments on ladders,  I never bother with them for Mun and Minimus, the suit thrusters are powerful enough for a kerbanaut to fly up to the hatch 

[bewing]

I switch to sandbox mode. I need to know if my booster stages are going to be sufficient to get me to LKO. I want to know where my apoapsis is going to end up after my launch. Any special tasks to do during launch. I need to know how much fuel the top stage is going to have once it's in orbit.  I need to know how much fuel it's going to take to get to an encounter (and how long the burn will last), how much to close the orbit, how much to descend to a low circular orbit. How much will it take to burn to 0 orbital velocity. How much to get any landers to the ground -- all with safety margins. All these things can only be found (approximately) by experiment.

So I design the top stage, guess at the boosters. Launch it. Do a quicksave just before I start burning liquid fuel to close my LKO. If it gets to orbit properly, I get as many numbers as I can, do another quicksave, try a transfer orbital burn. Then I go back to the quicksave, turn on the infinite fuel, and do it again. Then I have fuel remaining to do all the testing at the destination, and get those numbers. I also get to see if I forgot anything on any of the ships. Retro thrusters, solar panels, see if the ladders work, or if I can fly around on my RCS jetpacks.

Then take the ship's .craft file and move it back to my career mode game, and use it.

 

 

[maceemiller]

6 hours ago, Benoit Hage said:

 

Beside, that... there is not much else to think about. Batteries in case you land on the dark side, some light and especially, a ladder! ( yes yes, don't laugh, it will happen to you one day )

Also, test on the launchpad to check if you Kerbals can use that ladder, sometimes the ladder is too short and can't get back inside their ship, or an engine gets in the way while descending.

Never a truer word spoken! Done it countless times. As for testing the ladders its essential. Theres nothing more frustrating than not being able to re board your craft.

[federicoaa]

Follow this instructions once in munar orbit

1. Save game
2. Attempt landing
3. If ship exploded, reload and repeat 2.
4. Profit

 

Now seriously, landers are not really that complex, you just need TWR higher than 1 (in the body you attempt to land) and for that you can use MJ or KER, then you need enough dV to go back to orbit (unless you want to strand your kerbals)

Try minmus first it's easier because of lower gravity.

[Perry Apsis]

On 1/30/2016 at 8:16 PM, Benoit Hage said:

Also, test on the launchpad to check if you Kerbals can use that ladder, sometimes the ladder is too short and can't get back inside their ship, or an engine gets in the way while descending.

And leave a little extra on the ladder. I had a case recently where it worked fine on the launchpad, but I landed on a slope, and it was just a *little* too high for my Kerbal to reach. And I've also had cases where I plumb forgot the ladder, and where the ladder was just plain too short.

[moogoob]

I use sandbox mode and SOMETIMES (if I'm in a hurry or testing for interplanetary landings) hyperedit, unless I'm just recreating a design I know will work cause I've built dozens in its basic style.

[magnemoe]

On 30.1.2016 at 1:50 AM, Finox said:

You could try practicing landings and take offs on Kerbin before you head out, actually its a pretty good idea just so you know how your lander will handle.   When I was getting ready for my first mission I also did some tests like seeing how long I could burn the lander engine at full throttle and determining how maneuverable my lander was.   Good luck with your mission!

This, and yes it will require increasing twr, using extra radial engines works well for this, you are interested in how it handles during landing not deorbit. 

Anyway, Mun is close, I often use Mun as an testing area for landers going to other planets. More fun if you can return to LKO and dock lander with mothership for the trip. 
Works well if you can refuel on Mun. For rovers this is especially interesting, test one is around on spaceport, test 2 is on Mun. 

[nobodyhasthis2]

On 1/30/2016 at 0:14 AM, martincmartin said:

I'm about to make my first lander to land on the Mun.  Yay!  To test different designs, do I really need to launch each one from Kerbin and transfer to the Mun?  That's a lot of time before I get to the actual landing part.

The contract progression in Stock is not very good. What should be guided to do is complete power landings on kerbin first. 

On 1/30/2016 at 1:19 AM, Xavven said:

I second that! I like to test by initiating a hover on the launchpad, flying gently over to the flagpole, and making a smooth landing. Since Kerbin's gravity is higher, I usually switch out my LV-909's with LV-T45s just for the test, and make sure everything from attitude control to ladders and lights are working properly. Then I switch my LV-909s back in and head to the Mun!

Also, hovering in Kerbin's gravity takes a lot more skill than in Mun or Minmus gravity. If you can master your flight skills near the launch pad, Mun will be a piece of cake when you get there!

 Which is a Kerbal version of how NASA planned it out for Apollo. This plan included the most hated aircraft ever for a short time to get the hover training done. Everything was simulated to the limits right here.  

Edited January 31, 2016 by nobodyhasthis2

[MatttheCzar]

A note: The test lander NASA built used two rocket engines, each half the strength of the LM engine, and a jet engine to simulate both the lander and lunar gravity.

[Warzouz]

I remembered testing my Laythe lander on... Kerbin back in beta 0.9. As for Tylo (SSTO low TWR) lander, I didn't tested it. but I brought a secondary (staged high TWR) lander which I was sure I would land on Tylo.

In 1.0.x, I use Hyperedit on a sandbox save to put lander is low orbit, then land. I used a lot in1.0.4 to design my Eve lander. I successfully did it after 25 tests...

But in most cases, as I always use the same lander which is quite a simple design, I'm used to it and feel no need to test it.

 

[Warzouz]

On 30/1/2016 at 2:16 AM, Benoit Hage said:

Also, test on the launchpad to check if you Kerbals can use that ladder, sometimes the ladder is too short and can't get back inside their ship, or an engine gets in the way while descending.

That's a VERY good advice. We rarely forget to place ladders, but we can misplace them so you can fail to reach the pod. Always test the lander only on the pad. Get out and get in.