A good rover for Minmus?

[MrPopcup]

The tittle says it, I'm trying to make a rover that doesn't bounce off on minmus, I always make rovers that are pretty good on Moons and atmospheric bodies, but it doesn't work on minmus ( also Pol,Bop and gilly ) cause of the low gravity, so if anyone can help me? I tried making the center of mass close to the ground but that doesn't help!

Edited August 7, 2013 by MrPopcup

[Lindy]

Along with a low CoG have you tried wide and slow? How about a tracked vehicle? I don't have a link handy, but there is a tracks mod around, and they do work well in low gravity.

[capi3101]

Had one that I drove on Minmus last night for fourteen kilometers without a hitch...of course, this is the same design that utterly failed to flip over on Kerbin even when turning at 23 m/s. I'll say that having SAS on and using the docking controls (as opposed to the staging controls) makes driving a rover a heck of a lot easier, as does low and wide. Try using a Reaction Wheel instead of a Rovemate for the chassis, and use modular girders to form the remainder of the wheelbase...on my rover, I've got the front wheels extended further forward with XL girders, with four wheels in the back; the two outboard wheels are on girders jutting from the side and the inboard wheels are center; they're there for additional power (and to help offset the weight imbalance a bit - my skycrane for the thing includes a counterbalance). Basically, it's what they called "cab forward" design in the early '90s - and it's remarkably stable; don't even have to lock steering on the back set of wheels.

Somebody will tell you "re-map your translational controls to the keypad" sooner rather than later...

Need to get some pics of my rover up. I thought I had some, but apparently that's not the case.

[MilanFIN]

I've added some beams to avoid mine from flipping. Only tested on mun, but with slower tyres it might work in other moons as well.

[lammatt]

bounce?

it's probably your landing speed is too fast...try a touch down with less than 1m/s and you'll be fine

--

but if the problem is flipping or rolling over...that's another story

since Minmus has low gravity; a slightest moment can make the rover flip

to battle this you either lower the center of mass as low as you can and your wheel span as wide as you can

if this still does work very well

use a stronger torque reaction wheel and drive with SAS on.

the reaction wheel will be probably enough to exert a torque to balance the flip/roll

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but in extreme case... if the rover still flips/rolls

add RCS thrusters and use the translational thrust to counter teh roll/flip.

[MilanFIN]

I've got one on mun, but adding smaller tyres might work on other moons as well. The beams are bloking it from falling over.

[MrPopcup]

@ Lindy-

No, I didn't try it wide and slow, but I will right now! thanks for advice!

@ Capi3101

thats a great rover! I didn't put ASAS module on it because I heard it will screw up the turning around, but I'll use your advice, and I'll reply if it worked with pictures

@ lammatt

I play ksp since 0.17 , I have no problem with landing speed or anything, I can even achieve a VERY soft landing ( 0.5m/s ~ 3/ms ) usually I land at this speed, again I have no problem with this, and I've deployed MANY rovers, it's just gravity.

but yeah, problem is that when I speed up say ( 7m/s ) and do a SLIGHT turn the rover with flip to it's other side, I have a low center of mass but i'll make mine wider and lower to the ground with ASAS,

Can anyone provide some pictures with some rover that has a really low center of mass?

note**: I play a vanilla KSP and I don't want anymods. just stock parts!

[lammatt]

see...

when you turn your car

it's as if it's travelling a section of a circular motion

and i.e. there must be a centripetal force on the car in order for the turn to even exist

however... this same external force is what makes the car topples...

we have that centripetal force (which is the friction acting on the wheel by the ground) also giving rise to a moment about the contact point of the wheel.

and because the only counter moment is the one exerted by gravity at the center of mass

since minmus has low gravity the moment is low and because moment is the dot product of the force and distance

you either make the distance large or the angle small or both.

that's why you shoould make the wheel span large or the center of gravity low.

---

generally...

people here suggest the CoM-wheel angle lies anything less than 45deg is fine

but it always doesnt hurt if you can get it even lower.

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further...

you want to afford a small centripetal force

i.e. either a small v or a large r or both (F=mv^2 /r)

so... slower speed and shallower turn helps too...

---

you know... driving on minmus isnt the easiest thing...

the low gravity and uneven terrain arent your friend.

Edited August 7, 2013 by lammatt

[Geschosskopf]

On Minmus, as an alternative to a wheeled rover, you can just tape some lawn chairs to a small RCS fuel tank. Then just blip along following the terrain without worrying about bouncing on bumps . Just be very gentle on the controls and sure to put a parachute on such a thing because you can accidentally reach Minmus escape velocity if get going too fast, in which case you'll probably have to re-enter back at Kerbin .

[MrPopcup]

True, but now i'm back with a surprise!

Yep, you guessed it, I made a rover that reaches a top speed of - 23.1 m/s! incredible! It also jumps from the surface but lands quite nice! with no bouncing or rolling off, tipping over, in-fact, I made a hard touchdown, my skycrane was out of fuel ( when I realized my nuclear engine was sucking from it's fuel after I decoupled ) and it touched down @ 3.6m/s but I drove 14.1 Km! omg amazing!

this is where I landed:

High Speed!:

Bonus Picture:

Has anyone noticed the new textures? look, it seems like it got a brown/grayish colour.

[capi3101]

Nice looking rover you've got there. One quicky suggestion for the future...I'd highly recommend encasing the critical hardware - probe core, batts, RTGs - between structural panels or girders (or at least sandwiching them). Why? Those parts have an impact tolerance of 80 m/s, far faster than you could drive. If despite all your precautions the rover flips at high speed, a simple structural panel will make the difference between having the annoyance of figuring out how to upright it again (easily doable on a low-gee world like Minmus) and having the frustration of yet another pile of debris generated...

Eight RTGs is a bit much for the hardware you've got, but to each his own, right?

I might suggest the addition of a roll cage for the seats, but as I have no idea how to build an effective cage out of stock parts my own self, I won't actually suggest it.

[MrPopcup]

I got your idea, I once made a medium sized manned rover using what you said, but here I found it useless as I THOUGH that the wheels won't make that ' fast ' contact with ground on minmus, which is true, you can see the wheels spinning and spinning but a little speed is coming out, this doesn't happen on mun/kerbin, I tested this rove and it goes until 35m/s ( so far ) but yeah, great idea of protection the critical hardware.

thanks guys, everyone gave me an idea and I'm happy now ;D!

[dharak1]

I have a set of rovers that comes in on a craft it contains 6 modules that can dock any way around. It has two "engines" and four "trailers" The engines have 180 liters of fuel and two orange radial engines facing up that give it downforce for traction at two notches on the throttle it can get to around 25m/s then shut off the thrusters and the low friction lets it glide forever.

[capi3101]

I realized today that I've never put up any pics of my Hellhound 7 rover anywhere...here are a few. On Minmus, no less.

Last one's my favorite...Kerbol-set, with Mun, Kerbin and Kerbol all in the shot (though you have to squint to see Mun).

[Bacterius]

Another option is to use downwards RCS (shift, I believe, or ctrl) to pin your rover to the ground and prevent it flinging itself into orbit. A good design is far superior, of course, but it can help in a pinch.

[Mtshaw113]

What are the parts in betweeen the front 2 axels(?)

[capi3101]

Responded to your PM. Admins are probably going to lock down this thread for gross necromancy...

Those are structural panels held on by strut connectors. There's also a pair of RTGs there; the Hound is RTG powered. IIRC I put that panel out in front specifically to protect those forward RTGs, which would otherwise be outside of that protective "sandwich" for critical parts. The prototype was slightly underpowered, hence their addition. Might've also done that to help better protect the headlight.

[Skorpychan]

TBH, I just stick with suborbital hops rather than rovering around on Minimus. The low gravity means even Jeb's jetpack is good for that.