Lander help?

[lordmuffin]

I got a basic lander design, but whenever I try to land, the craft either explodes when touching the ground, or tips over then explodes. Any idea why?

[tater]

A picture might help. Have you considered landing at a lower speed?

[Tex]

This.

A picture might help. Have you considered landing at a lower speed?

Also, if your lander is tipping over upon touchdown, that either means A) you have too much sideways velocity when you make contact, the landing gear is being destroyed by too much speed (a good rule of thumb is to land at less than 8-10 m/s at all times), C) your lander is unbalanced and the extra offset weight is pulling the lander over, or D) you are attempting to land on an incline in the terrain.

Again, pictures of the lander would be helpful but all it takes is some practice and experimentation. Don't forget to quicksave!

[Norpo]

A picture might help. Have you considered landing at a lower speed?

This: A good landing speed is generally under 7 m/s. Any higher and regular parts go boom.

If you have landing legs (which I hope you do) then are they deployed? Double click the green gear icon on the altimiter (thing on the top that shows how high up you are), it's on by default, but landing legs are not, so you'll need to click the gear icon twice to activate them.

Also, tipping over and then exploding generally means your center of mass may be too high. Is it a short lander or a tall lander? Try to make landers as short and stocky as possible. Either that, or you're landing on a non-flat area, or you may not have enough control (or WAY too much) with reaction wheels.

(also, some information on where you're landing may help, Kerbin or the Mun/Minmus, or somewhere further out, like Duna or any of the other planets?)

[Razor235]

Yes, screenshots would definitely help. In their absence, I can only give a few general tips.

-Make sure you're landing at a safe speed. I would recommend from 1-10 m/s vertical. It's possible to land at higher speeds, but you risk damage or bouncing and landing in an unfavorable position. Make absolutely sure you cancel your horizontal speed, 1-2 m/s at the most.

-Widen your suspension. If your footprint is thinner than your lander is tall, you will likely tip over. You can easily widen it by mounting your legs on small fuel tanks or the modular girder segments. As a bonus, they act as handy mounts for scientific or other utility equipment.

-KISS. The more complicated or large your lander is, the more likely it is to fail. You can make a Mun lander and return vehicle with just a Mk1 pod, a parachute, an FL-T400 tank, an LV-909, and four landing legs. It would be kind of unstable, but you could mount the legs on struts or something.

[Taki117]

A picture will definitely help, but if you are tipping over I suspect your lander is too tall or you are not completely killing your horizontal velocity at touchdown.

[lordmuffin]

With the mods I have installed, for some reason, I can't load or save anything. So I'll have to rebuild it, then I can give you some pics.

[lordmuffin]

Here are the images of the lander, re-created.

[capi3101]

I can't offer any advice that hasn't already been offered to you, so I won't. Which is not helpful, I know...

If you can't (or don't want to) provide a screenshot, can you at least describe the parts you're using to us? Is it a design like Razor235 described (i.e. a very basic lander design)? If so, try attaching a quad of modular girder segments on the sides of the tank and attaching the legs to those; it'll widen your base and help with stability issues. And watch your piloting.

[Taki117]

Here are the images of the lander, re-created.

Yeah, you have a really tall lander and a really tiny base. What you could do is move those TH4 Canisters down around the base of your lander, this would move the CoM down and widen your base.

[The_Rocketeer]

Yeah, you have a really tall lander and a really tiny base. What you could do is move those TH4 Canisters down around the base of your lander, this would move the CoM down and widen your base.

Agreed. The capital reason for your problem is your lander's CoM is far too high in the structure, so even a little sideways motion or gently sloped surface tips it over. It's like trying to balance a lollipop on the stick.

[MarvinKitFox]

What is wrong here... let me count the ways....

Monopropellant tanks are very bendy, not advised as the primary structure for your lander.. or *anything* really. They are even more squishy than docking ports.

Your radially mounted doohickeys serve a very similar role as the prongs on an oldstyle sea-mine

That roofrack is violating all known freeway loading statutes.

Try something with a center-of-mass that is lower than 2/3 the distance between your landing legs.

Mount the legs on a *rigid* surface, not on jello.

If you *must* put such a load on your roof-rack, at least use some bungee cord (struts) to keep it from slipping off.

[The_Rocketeer]

Monopropellant tanks are very bendy, not advised as the primary structure for your lander.. or *anything* really.

Hmm... not 100% in agreement here. Those tanks + Lander Can with a suitable number of RCS thrusters make nice lightweight lander with a decent amount of dV. Not saying it's the best bit of engineering in the world, but I wouldn't pull this little design down for that.

[Vanamonde]

Stable landers need to be low and wide to avoid tipping.

Bouncing is a matter of speed.

[lordmuffin]

Agreed. The capital reason for your problem is your lander's CoM is far too high in the structure, so even a little sideways motion or gently sloped surface tips it over. It's like trying to balance a lollipop on the stick.

What is wrong here... let me count the ways....

Monopropellant tanks are very bendy, not advised as the primary structure for your lander.. or *anything* really. They are even more squishy than docking ports.

Your radially mounted doohickeys serve a very similar role as the prongs on an oldstyle sea-mine

That roofrack is violating all known freeway loading statutes.

Try something with a center-of-mass that is lower than 2/3 the distance between your landing legs.

Mount the legs on a *rigid* surface, not on jello.

If you *must* put such a load on your roof-rack, at least use some bungee cord (struts) to keep it from slipping off.

Okay, just saying, I just started playing the game, so I have no idea what I am doing.

Second, I have a vague idea what CoM is, so:

Higher CoM = Bad

Middle CoM = Good

[Taki117]

Okay, just saying, I just started playing the game, so I have no idea what I am doing.

Second, I have a vague idea what CoM is, so:

Higher CoM = Bad

Middle CoM = Good

The lower the CoM (Center of Mass) the better with landers, also if you have a wider base you can land on higher slopes and not tip over as easy.

[merendel]

Okay, just saying, I just started playing the game, so I have no idea what I am doing.

Second, I have a vague idea what CoM is, so:

Higher CoM = Bad

Middle CoM = Good

As a pratical example of why you want your COM low compared to your landing base. Your average human has their center of mass somewhere near the lower end of their torso. stand with your feet togeather and have someone give you a push to the left or right and see how easy it is to tip you over. Now repeat that experiment with your feet spread fairly wide. You'll note that the wide leg stance is much more stable. Not only does your COM shift downwards a bit but the ratio between how wide your base vs how high your COM is gets smaller. The same principle applies to landers.

[Kryxal]

It gets worse ... if I'm not mistaken, aren't those ThF4 containers from KSP-I and rather heavy? You could probably make your life a lot easier by dropping those down to radial attachments, 2 deep in 4-way symmetry and use them as attachment points for the legs.

[cantab]

Whoa, yeah, that design is going to be tricky.

Even if I wanted to keep the tall and skinny form factor, I would at least take out that girder adapter, and just stick the long girder atop the lander can.

It looks like you have severely imbalanced RCS. Loads of ports at the bottom but none at the top. That means that when you try and apply lateral thrust, which would otherwise really help you land, you'll also be tilting the craft. And the angled ports won't work great either. I would change to a ring of 4 or 8 ports at the base, and another at the top mounted on a part above the ThF4 containers. If you need more vertical thrust add linear ports on the base, or better use the O-10 engines, variable thrust will help you land.

You could also try more torque, it can help steady the lander on tricky terrain. Maybe stick a large ASAS on the top that can both do that and hold your upper RCS ports.

[Yakky]

Here are the images of the lander, re-created.

http://i.imgur.com/8BUf9QU.jpg

http://i.imgur.com/2FqRB6o.jpg

http://i.imgur.com/5xWKgZ0.jpg

Am I missing something, or do you not have an engine to slow your descent? Not familiar with the mods you're using but the mod parts in your pics don't look too engine-like to me. I'm pretty sure that ring-o-thrusters is not enough to slow you down.

If those upper parts are in fact engines, is it possible their thrust is getting blocked by the lower parts?

BTW one other idea which will help at the margin (not a lot) is to go from 3 legs up to 4 or 6. Gives you a broader base for a little more stability.

[Kerba Fett]

That's a really tall lander. I don't recognize those tanks on the upper half. do you need them for the landing?

I assume you're using monopropellant as your main fuel source. Even so that seems like a lot. Could you get by with only one tank?

I don't see any reaction wheels so I guess you're limited to what torque the pod supplies. Try moving your thrusters to the top of the ship so you're hanging from your center of lift.

You could also mount your landing gear on the large radial decouplers to widen your footprint a bit. They're lighter than girders and you can mount stuff inside them.