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what is the point of rovers on moons/planet with low gravity?

lammatt

By lammatt
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Brotoro

Brotoro

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There have been times I've needed to move six kernels from my Minmus base to their Kerbin-return ships parked 2.3 km away (for reasons of lag prevention). I was glad to have a rover I could pile them all on and drive them over in one go rather than have to do the rocket-pack thing over and over and over and over and over again.

Plus, I recently tested out a rover for Bop, and it was loads of fun flying that thing over huge distances when it went over bumps.

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lammatt

lammatt

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There have been times I've needed to move six kernels from my Minmus base to their Kerbin-return ships parked 2.3 km away (for reasons of lag prevention). I was glad to have a rover I could pile them all on and drive them over in one go rather than have to do the rocket-pack thing over and over and over and over and over again.

Plus, I recently tested out a rover for Bop, and it was loads of fun flying that thing over huge distances when it went over bumps.

2.3km is an odd spot...

you should either set them >2.5km apart to let the physics sim unload, or park them a lot closer

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FlamedSteak

FlamedSteak

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I find rovers pretty boring most of the time, they're slow, prone to flipping and I always end up stranding someone by seeing how high I can launch it off the top of a hill.

With the Kethane and KAS mods, it makes more sense to deliver short hop landers (with probe cores and seats) to the surface.

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katateochi

katateochi

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I like rovers on low grav places, just simply for the fun of diving them and attempting silly stunts that no self respecting astronaut would ever do. My goal for rovers (aside from base assembly ones) is to see how fast they can go and still be "safe".

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lammatt

lammatt

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I like rovers on low grav places, just simply for the fun of diving them and attempting silly stunts that no self respecting astronaut would ever do. My goal for rovers (aside from base assembly ones) is to see how fast they can go and still be "safe".

well....

but...

here in my pic, my rover doesnt even pick speed up...

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katateochi

katateochi

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well....

but...

here in my pic, my rover doesnt even pick speed up...

On my fast rovers, (fast being limited to 60m/s cos of the wheel breaking limit) the key was in RCS usage. Not for forward propulsion (although I do use that too) but for stability, traction and braking.

My fast rovers have RCS ports facing straight up which act to push the rover into the ground, helps keep the wheels in contact and when going over small bumps helps you not loose control (sometimes). I drive in docking mode, not just for the torque factor, but because of how it changes the RCS directions to complement driving, I just have to tap RCS on and off to get a quick burst to push the rover down.

I have RCS ports facing forward to help slow the rover down which really helps improve the survival rate of the poor occupant. I also usually equip them with a reaction wheel if they don't have a pod which helps reducing tipping (but u must drive in docking mode) or if you do start to tip you can correct it.

This is one of my fav rovers that I made a while back, It was designed for Mun, but it works well on Minmus too.

RJgAFBJm.jpgKXR1tn9m.jpg

It has two RCS ports facing up, one facing forward and two facing back. The back facing ones help with initial acceleration and then the wheels maintain the speed. This one is pretty safe at speeds of around 55m/s, it would go faster but the wheel bursting limits prevent that. It's low and fairly wide so it doesn't tip too badly anyway, but it also has a small reaction wheel (from KSPX) to further help with that.

(it also folds up, which has no relevance to this topic, but hey, it folds. - http://imgur.com/a/V2xXc)

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lammatt

lammatt

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On my fast rovers, (fast being limited to 60m/s cos of the wheel breaking limit) the key was in RCS usage. Not for forward propulsion (although I do use that too) but for stability, traction and braking.

My fast rovers have RCS ports facing straight up which act to push the rover into the ground, helps keep the wheels in contact and when going over small bumps helps you not loose control (sometimes). I drive in docking mode, not just for the torque factor, but because of how it changes the RCS directions to complement driving, I just have to tap RCS on and off to get a quick burst to push the rover down.

I have RCS ports facing forward to help slow the rover down which really helps improve the survival rate of the poor occupant. I also usually equip them with a reaction wheel if they don't have a pod which helps reducing tipping (but u must drive in docking mode) or if you do start to tip you can correct it.

This is one of my fav rovers that I made a while back, It was designed for Mun, but it works well on Minmus too.

http://i.imgur.com/RJgAFBJm.jpghttp://i.imgur.com/KXR1tn9m.jpg

It has two RCS ports facing up, one facing forward and two facing back. The back facing ones help with initial acceleration and then the wheels maintain the speed. This one is pretty safe at speeds of around 55m/s, it would go faster but the wheel bursting limits prevent that. It's low and fairly wide so it doesn't tip too badly anyway, but it also has a small reaction wheel (from KSPX) to further help with that.

(it also folds up, which has no relevance to this topic, but hey, it folds. - http://imgur.com/a/V2xXc)

that's exactly why i am disappointed

you need RCS to push the car down before you get any meaningful traction for the wheels to work is just lame...

the kerbal engineers should have just used rubbers that have insane friction coefficent on the rover wheels to begin with.

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katateochi

katateochi

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that's exactly why i am disappointed

you need RCS to push the car down before you get any meaningful traction for the wheels to work is just lame...

the kerbal engineers should have just used rubbers that have insane friction coefficent on the rover wheels to begin with.

That's much like a sports car that needs a spoiler to help push it down to improve traction. In rl the moon rovers moved so slowly (about 3ms) which feels almost stationary in KSP. I'm sure you can get 3ms out of your rover, any faster and you're racing so you need a 'spoiler'! ;)

I think that if they increased the friction the next thing would be everyone complaining that cornering at any speed sends them tumbling over. Before the stock wheels came out, one of my fast rovers used a couple of the bobcat rover probe bases, to make it safe I actually had to modify the friction to be less so it could skid a little when cornering fast and not just tip over. when I turned the friction up much more than default the darn thing would just back-flip straight away. I think they've got a pretty good balance now.

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lammatt

lammatt

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That's much like a sports car that needs a spoiler to help push it down to improve traction. In rl the moon rovers moved so slowly (about 3ms) which feels almost stationary in KSP. I'm sure you can get 3ms out of your rover, any faster and you're racing so you need a 'spoiler'! ;)

I think that if they increased the friction the next thing would be everyone complaining that cornering at any speed sends them tumbling over. Before the stock wheels came out, one of my fast rovers used a couple of the bobcat rover probe bases, to make it safe I actually had to modify the friction to be less so it could skid a little when cornering fast and not just tip over. when I turned the friction up much more than default the darn thing would just back-flip straight away. I think they've got a pretty good balance now.

nah, i can barely get to 0.5m/s....

can as well walk. or jet pack.

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sharpspoonful

sharpspoonful

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nah, i can barely get to 0.5m/s....

can as well walk. or jet pack.

Then you are either not engineering it correctly, or not having the patience to drive a rover across the Minmus ice fields. Even with the low gravity and traction, I can still get them to slowly maneuver safely at 10 m/s (that's 36 mph), it just takes longer is all.

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Spatzimaus

Spatzimaus

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All of my rovers have vertical lift capability, even if it's only rarely used after the initial landing. For instance, here's an older version of my smallest manned rover, which uses the VTOL rockets from the B9 mod:

RM5aK3F.png

That picture is of it leaving Kerbin orbit under its own power, but I usually use a carrier module to get the rovers to the various moons instead. It's designed for Mun, so those rockets are only used when I need to move it to another part of the planet entirely, or I'm confronted with something like a crater edge that's too steep to easily drive over.

On a lower-gravity moon like Minmus or Pol, those rockets serve a different purpose; if I leave the surface because I went too fast over a ridgeline or something, they allow me to control my descent with only a minimal cost in fuel. The thing is, this rover is also a mobile Kethane refinery, so when it's fully loaded it's actually a bit over 30 tons. That mass gives it pretty good traction, even on Minmus, even if the extra mass does make it a bit top-heavy when trying to make sharp turns.

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Kasuha

Kasuha

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Then you are either not engineering it correctly, or not having the patience to drive a rover across the Minmus ice fields. Even with the low gravity and traction, I can still get them to slowly maneuver safely at 10 m/s (that's 36 mph), it just takes longer is all.

There are areas of "bad terrain" on many bodies including Minmus. Rovers have very hard time accelerating on such surface or they get phantom acceleration in unexpected directions such as uphill. It's one of known bugs in the game. This terrain usually has another property - you shine a light on it and you don't see any change on the surface.

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spectrhz

spectrhz

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I took a rover to pol recently, I knew it wouldn't work well,it was originally part of my eve mothership/surface outpost. Since I had the delta-v and had never been to pol I decided to take the whole massive lag machine there. Worth it.

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sharpspoonful

sharpspoonful

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There are areas of "bad terrain" on many bodies including Minmus. Rovers have very hard time accelerating on such surface or they get phantom acceleration in unexpected directions such as uphill. It's one of known bugs in the game. This terrain usually has another property - you shine a light on it and you don't see any change on the surface.

Oh, I understand that, but his complaint about rovers doesn't seem to be about the bugs in the game, but the physics and overall speed of the rovers.

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Kasuha

Kasuha

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Oh, I understand that, but his complaint about rovers doesn't seem to be about the bugs in the game, but the physics and overall speed of the rovers.

His complaint seems to be that he's barely able to make 0.5 m/s. I don't see any further details but assuming it is related to certain position of his rover, it matches my experience with "bad terrain" pretty well.

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el_coyoto

el_coyoto

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Soo... Has anyone tried that trick from Armaggeddon, where they hard RCS on top of the rovers, pushing them down to improve traction?

Yeah, I know that movie was 99,9% bull****, but that one might actually work...

I think people regularly use this trick in KSP, so it should work. I've seen RCS and ion engines (more fuel efficient) used for this, never tested it myself.

Just make sure the thrust goes through your center of mass... :D

To counteract the traction problem on low grav worlds, I usually build big and heavy and hope for the best. I also like giving my rovers (small or big) the ability to land and fly around on their own.

It's been a while since I haven't "roved", but here a two examples of what I mean :

Not sure about the "0.5 m/s top speed" problem described by lammatt in the opening post though...

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