Struts vs Wheels for landing vs girders

[tranenturm]

I'm looking to do a mid-career science lab to the mun and wanted it mobile. I was looking at landing gear and saw their m/s values. Then I looked at wheels and they were measured in vastly different units.

How do I compare impact tolerance of wheels and struts.

I also noticed the girders had VERY high impact resistance, anyone use those for landings?

Edited May 15, 2015 by tranenturm

[Geschosskopf]

I-beams and girders make good landing gear but have their drawbacks:

1. (new to 1.x) DRAAAAAGGGGG. You can't retract them, so they'll be sticking out during launch and fairings wide enough to cover the whole assembly make the launcher fly very poorly.

2. (from before) No traction. If you land on even a moderate slope, your lander will slowly slide down the hill. And as it does so, 1 or more girders will get a good grip momentarily as the rest of the lander keeps moving, so the leg will bend. Then either the girder will lose its grip and the lander will jerk forward, or the girder will break off and the lander will fall over.

But seriously, Mun has low enough gravity than the normal lander legs will work most of the time.

[n0xiety]

There are parts that has like 60m/s crash tolerance but that doesn't mean rest of your craft has the same values. Even if those girders don't explode the rest of the craft might just get separated and explode. Besides landing struts give you stability when you land on a slope.

[Jaeleth]

In short: do what you would do in the real world and it'll be the most sensible. Landing gear is perfectly fine for... Landing. Specially the most sturdy model, which I would recommend for a larger vehicle, like that mobile lab. You should never approach ground at a speed that would damage the landing gear, it's unrealistic, i always make my touch down at speed below 3 m/s, unless something gone terribly wrong, like running out of fuel a few meters above ground, as it happened to me once, on the Mun.

add a few roboust wheels that will make contact with the ground when you raise the landing gear and you've got yourself a very workable rover/lander

[tranenturm]

I found the m/s values for the rover wheels, which is what I was confused about (it also has impact values). I'll be attaching the rovemax M1 wheels to the sci lab (with cupola as command module for effect). The M1 wheels are listed at 50 m/s which is far more than I need. I wanted to land the rocket on its side and just wanted to be sure the rover wheels could handle it.

I do my best to land in a realistic manner, but as a novice I like to over engineer my rockets to account for my lack of pilot skills.

Thanks all!

[xtoro]

Go big or go home! Don't be afraid of large wheels or large payloads or fairings.

Here's my mining rover getting ready for launch:

This is what's inside the fairing:

Got to orbit no problems. Drag isn't a huge problem, just keep the speed down for the first 10k ascent and slowly speed up after that. My rover is based on the MK3 parts and holds over 5k LF and O2. It's now landed on Minmus and drilling for ore. The large wheels are great, they never break and can take a hard landing.

XT

[Jaeleth]

I found the m/s values for the rover wheels, which is what I was confused about (it also has impact values). I'll be attaching the rovemax M1 wheels to the sci lab (with cupola as command module for effect). The M1 wheels are listed at 50 m/s which is far more than I need. I wanted to land the rocket on its side and just wanted to be sure the rover wheels could handle it.

I do my best to land in a realistic manner, but as a novice I like to over engineer my rockets to account for my lack of pilot skills.

Thanks all!

That's a good principle. Not for the beginner only, but for all kerbonauts. Backups, always carry backups. Specially in long duration missions. More than once I saved my missions, Apollo 13 style, using gear that I carried in a different way it was planned to be used, but because I always put that "little extra" beyond what was considered "mission essential".