Need a crash course on rover design

[More Boosters]

Seriously though, can someone link me to a good rover design tutorial if one exists? Alternatively you can simply make a checklist for what a good rover should include.

[mhoram]

You can find a lot of inspiration in this 113 pages Post your Rover MEGATHREAD.

Also a quick search brought up this:

http://forum.kerbalspaceprogram.com/threads/126245-Rover-Suspension-And-Aesthetic-Tutorial

[capi3101]

1) Build it low. Or rather, build it so that the center of gravity is as low to the ground as you can get it. This makes the rover less likely to flip.

2) Build it wide. A vehicle with a wide axle track is less likely to flip.

3) Include SAS. Your options for bonafide SAS (i.e. something that will help the thing hold its orientation) aren't as wide as they used to be; once upon a time there was at least a reaction wheel in every successful rover I built.

4) Encase the critical bits in high-impact resistant parts (girder segments and structural panels). In the event of a flip, this makes those bits less likely to 'splode and kill your rover.

That's as general a set of guidelines as I can give. Other than that, a "good" rover is one that does what you want it to do. There are a few tricks I've learned over the years that I'd be willing to share (such as using ion thrusters to improve the grip of the tires, including an RCS braking system, or the "cheat" of including a Wheesley engine to lower the CoM), but I don't know if they'd suit what you wanted to do or not.

I leave you with this, an oldie (for sure) but a goodie:

[Kurld]

Build it low and wide. Bring plenty of electricity and a way to regenerate it. Plan for the almost certain inevitability that it will roll over on its back and design a way for it to right itself. If you have enough reaction wheel torque you can use that on low-gravity worlds to roll back over.

[Hagen von Tronje]

Capi's tips are good advice.

For low gravity bodies, downforce is a major concern because traction will be very low. You can counter this by either building a very heavy rover, which has some obvious drawbacks, or by mounting downthrusters, which can be low-thrust engines or RCS nozzles pointed UP, to push your rover into the ground and compensate for lack of gravity. This is extra nice when turning or changing gradient since those are the easiest times to flip.

Also don't neglect to tweak your wheels! It's very easy to overlook that you can and should adjust which wheels have steering and motor; a nice setup that feels natural is rear wheel drive/front wheel steering. This also saves on electrical consumption since only wheels with motor on drain batteries.

And for driving, my biggest tip is to watch it going over the tops of hills so you don't go flying, and not get carried away speeding downhill. Just in general, the biggest mistake you can make with rovers is impatience; you can speed up to x2 or x4 on flats and easy terrain with impunity, so take your time when making maneuvers.

[cephalo]

Rather than downward force, I find it easier to manage with forward and backward verner engines on low traction worlds. The issue is whether you can go up hills and then go down hills safely, and fore/back RCS helps a lot with this.

Oh yeah, and the FIRST RULE for rover design is to install the stock bug fix mod! Otherwise you will have no brakes and your rovers will be almost impossible to control. Rover wheels are catastrophically bugged right now.

[juanml82]

Also, the rover controls can be remaped to the numpad, so they don't overlap with the rotation controls. I usually have an action group to disable/enable torque, so the reaction wheels don't overturn the rover while driving and can easily be turned on when the rover flips over.

I find it's also a good idea to have multiple probe cores, one pointing up and another (pair?) pointing to the front. That way, you have the navball with half the ground at the bottom while you're driving while the core pointing up will show you a more intuitive navball when it flips over (or if the rover is also a lander). The MRS mod has some radially mounted probe cores which work great for rovers.

[Hagen von Tronje]

Rather than downward force, I find it easier to manage with forward and backward verner engines on low traction worlds. The issue is whether you can go up hills and then go down hills safely, and fore/back RCS helps a lot with this.

Oh yeah, and the FIRST RULE for rover design is to install the stock bug fix mod! Otherwise you will have no brakes and your rovers will be almost impossible to control. Rover wheels are catastrophically bugged right now.

I keep hearing this but I'm still not clear on it. When I apply brakes on my rovers, they do indeed come to a stop, and do so faster than merely holding reverse, and in a time frame that I consider not completely unreasonable for a rover (though not what you'd expect out of a car). Are they supposed to be better than that or did I win some kind of no-bug lottery or what?

[cephalo]

I keep hearing this but I'm still not clear on it. When I apply brakes on my rovers, they do indeed come to a stop, and do so faster than merely holding reverse, and in a time frame that I consider not completely unreasonable for a rover (though not what you'd expect out of a car). Are they supposed to be better than that or did I win some kind of no-bug lottery or what?

Here's the issue with the wheels, for example I'll discuss just the orange wheels. They come with a default brake force of 300. However, if you right click on the wheel to tweak it, this will be reduced to a max setting of 30. The wheels are fine unless you right click on them at any time, after that they are severely broken. The brakes will slow your momentum still, but not enough to counter a downward slope.

[GarrisonChisholm]

Here's the issue with the wheels, for example I'll discuss just the orange wheels. They come with a default brake force of 300. However, if you right click on the wheel to tweak it, this will be reduced to a max setting of 30. The wheels are fine unless you right click on them at any time, after that they are severely broken. The brakes will slow your momentum still, but not enough to counter a downward slope.

Ah-ha! Thank you, very useful info.

[Hagen von Tronje]

Here's the issue with the wheels, for example I'll discuss just the orange wheels. They come with a default brake force of 300. However, if you right click on the wheel to tweak it, this will be reduced to a max setting of 30. The wheels are fine unless you right click on them at any time, after that they are severely broken. The brakes will slow your momentum still, but not enough to counter a downward slope.

Thanks, that clears things right up. Wow, I kinda like the sound of brakes 10x more effective, but implementing them after just starting an Elcano challenge might be a little cheaty.

[cephalo]

Thanks, that clears things right up. Wow, I kinda like the sound of brakes 10x more effective, but implementing them after just starting an Elcano challenge might be a little cheaty.

Certainly they allow the bug fix mod.

[capi3101]

The problem I always used to have with using the brakes is that they too had a tendency to flip the rover, particularly if you were travelling at speeds much over 20 m/s (45 mph - what happens when you slam on the brakes?). It's another rationale for providing some kind of down-force producing mechanism. Ions and RCS are the two methods I've encountered over the years that folks recommend for that job. Ion thrusters have two advantages: one, an ion-based system can be set to run by opening up the throttle (instead of having to hold down a key to keep the RCS going - I haven't heard of anybody using an O-10 engine for this same purpose but I imagine it would work) and two: longevity - assuming you're deploying the rover on a world without an atmosphere, you get that awesome Isp. RCS's advantages - they come down lower in the tech tree, the parts are less expensive as a rule, and the power requirements are much lower. It's noteworthy that a linear RCS port and an ion-thruster output the same amount of thrust; the RCS port has less mass, another advantage.

[ajburges]

As alluded, unexpected body torque is the biggest threat to rovers.

You can mitigate this with counter torque (RCS or reaction wheels), increasing your moment of inertia (widen the base or increase your mass), or reducing the torque induced (removing drive and lessening breaking force of outer wheels)

Even when you manage torque, it can be annoyingly easy to flip your rover. Have a plan for such an event. You can't count on any command seat Kerbals to help after a flip due to a bug with the seat. Use reaction wheels, thrusters, and/or a hinge (huge landing gear or a bay) to right a rover.

Test rover integrity by trying to wreck it on the launch pad a crawl way. Extreme tests will include full speed frontal crashes into a building.

Edited July 31, 2015 by ajburges

[Geschosskopf]

Some things I find essential (apart from those others have said, such as build it low and wide and use Stock Bug Fix Modules):

Remap the rover controls to some other keys. I use KP8 for forward, KP4 and KP6 for turning, and KP5 for reverse. This greatly helps rover stability because it takes torque out of the process. If you keep using the WASD keys to drive, you're also using torque, which will tend to make your rover roll over or somersault. Also, you can now drive your rover with both hands, one for the rover itself (the numpad) and one for torque (WASD). This enables you to use 1 or the other or both simultaneously depending on the situation. Sometimes, especially in rough terrain on low-gravity worlds, the rover steering won't work because there's not enough traction, but you can pivot with torque. And even on high-gravity worlds, you can greatly reduce your turn radius using both at once. Finally, when you get airborne, you can use WASD to make sure you hit the ground at the correct orientation.

Always have plenty of lights. Not only massive amounts of headlights but also some dimmer lights on all other sides so you can see what you're doing when you need to EVA beside the rover.

If you build the rover in the SPH, be sure to stick a cubic strut on the roof and then set the 0.625m probe core on top of this (rotated to the horizontal plane with the S key). Use the rover's cockpit or inline probe core for driving and flying in space, and the core on the roof for landing.

Keep an eye on your ground clearance. Although you want the rover low and squatty, make sure that no structural part will touch the ground due to suspension flexing or tires going flat. Flat tires usually won't flip you unless they cause some fixed part to hit the ground. And don't make the rover so low and wide that the belly will drag when you go over the crest of a hill or the lumps on the crawler track at KSC. This is especially something to check if your rover's weight is going to change a lot during operation (like it's a fuel truck). Be sure to test ground clearance both full and empty.

Always have a battery and something that will charge it slowly no matter what. That way, you can cripple along in short bursts if your main power plant fails.

If you want to cover ground quickly, use airplane wheels and some form of rocket to get you up to speed. The airplane wheels can take a lot more speed and harder bounces than the rover wheels can. Then, when you need maneuver at low speed, retract the airplane wheels so the rover wheels touch the ground.

A fuel cell is a rover's best friend.

As with driving an 18-wheeler, hills are MUCH more of a problem going down than going up. If you must go down a steep slope, try taking it at an angle, run in reverse, and ride the brake.

[juanml82]

The new, larger, ox-sat panels included in Asteroid Day are also good for rovers (unless you're going beyond Dres)

[xtoro]

To keep my rovers from pulling wheelies or flipping toward when I brake, I always disable the brakes on the front wheels, and disable the motors on the rear wheels so that it's only the front pulling you. Nice and stable when combined with the other tips above.