Rovers on other planets/moons

[Wolfie2474]

So i have been thinking about sending a rover to duna but what is the ideal design? should i use a skycrane or should i land it entirely by parachutes? Also should i use Solar panels or RTGs                                                     

Edited November 27, 2018 by Wolfie2474

[Mike Mars]

Solar panels still work on Duna.

Check out Wild Blue Industries mod for some cool rovers with built in rooftop solar panels.

I prefer skycranes because they provide better control for a precise landing.

Have fun and let us know about your future adventures.

MM

Edited November 28, 2018 by Mike Mars
spelling, duh!

[Pecan]

Solar panels definitely but as to the rest - what's the rover for?
If large & crewed then just design and build it like a normal lander except that you use wheels instead of legs.  Although parachutes work on Duna the atmosphere is so thin that whether they save more mass than they add is questionable.  I'd recommend first designing your lander/rover without them.
At the other extreme if you just want a small, drone rover then a parachute should be sufficient and your design should focus on making it as light as possible.

Either way, note that rovering around planets gets old really fast.  A lander/rover that can do several 'hops' and refuel in orbit is far more versatile and less boring.

[Guest]

Unlike Mars, Duna is quite easy to land on. Last time I dropped rovers there, I used parachutes. They were pretty light and had ruggedised wheels; I tested on Kerbin that they'd happily deal with a 25 m/s landing. I got it well below that with parachutes. 

For Tylo I clipped an Oscar with an Ant at each end of the rover, with decouplers ejecting the engines after landing. If your rover is bigger and you don't have enough parachutes, you can use that technique for the final braking -- you'll only need, like, 10 m/s or so. 

Skycranes also work, as do VTOL cargo planes and a lot of other things. Use your imagination and do whatever feels cool.

I also agree with @Pecan about rovering getting old fast. I used the rovers to scout for a base site and they did work well with that -- I dropped them in a promising ore-rich, low-lying area and then drove around a bit to find a suitably flat spot, but traversing any amount of distance quickly becomes a PITA. It can be fun the first time you land on a new body though -- I really enjoyed my drive from the highlands to the sea the first time I dropped a rover on Eve for example. Collected five biomes over less than 25 km!

[magnemoe]

8 hours ago, Pecan said:

Solar panels definitely but as to the rest - what's the rover for?
If large & crewed then just design and build it like a normal lander except that you use wheels instead of legs.  Although parachutes work on Duna the atmosphere is so thin that whether they save more mass than they add is questionable.  I'd recommend first designing your lander/rover without them.
At the other extreme if you just want a small, drone rover then a parachute should be sufficient and your design should focus on making it as light as possible.

Either way, note that rovering around planets gets old really fast.  A lander/rover that can do several 'hops' and refuel in orbit is far more versatile and less boring.

its two rovers in this image.

The small utilty rover and the huge base who cast shadow on it. 

Three more rovers.

The lander on just below the closed heatshield, and the base below it and an utility rover on side of the lower part of the base. 
Wheels here is simply as its hard to do precise landings on Duna so you have to drive say an kilometer to refuel. 

Has 3 classes of rovers, 1) large stuff with wheels so it can be positioned. 2) utility rovers mostly used to transport stuff for KAS assembly like extra drills and spare parts. 
3) fast rovers, this is the classical rovers either doing science or just for fun 
4) low tire mun lander with wheels, this is to be able to sample multiple biomes, it was more practical back then you had an area on Mun with 8 something biomes within 10 km. 

the small utility rover on the Duna lander is mounted on the side of base, release with decopler. 
For replacing the one on Minmus who clipped into terrain I used an skykrane as in an decopler on top of the probe core, 4 short 1.25 meters tanks, two in an stack and two radial with the small yellow radial engines, this took me all the way to minmus and landing there I gave trust until just about taking off and decouple so the skycrane skyrocketed. 

Edited November 28, 2018 by magnemoe

[Cavscout74]

For Duna, I typically use skycranes with assistance from a chute or two for rovers large enough to carry crew.  Mini rovers can usually get by with just chutes.  My primary use is scouting an ideal base landing location.  I also prefer to land my crew ships a little ways (500-1000m) away from the base for safety, so having a crew rover and fuel tanker rover is almost a requirement.  Like others have said, they get old fast for actual exploration.  One way around that is the Bon Voyage mod that drives them in the background while you do other stuff.

A Feline Utility Rover landing on Duna - the chute keeps the descent rate under 50 m/s, then the skycrane only has to provide a short landing burn.

[Cataclism]

By the way, if your intentions are for Duna only, at least for now, the reentry heat won´t be a problem (different from Mars). It will be gentle in Laythe, as well.
But, if you happen to grow an idea of reentering Kerbin or other atmospheric planes (planet pack MODs), the heat will take its told.

I´ve been beaten up by it in several The World Beyond planets, and most of the times the rover has to remain like a (chinese) farmer´s head until low atmosphere: all covered from the heat.

(the flames/fire effects have been disabled due to performance reasons)

Edited November 30, 2018 by Cataclism

[Fearless Son]

I have landed rovers on Duna a few times.  I find that parachutes are helpful, but the atmosphere is so thin that they rapidly hit diminishing returns, it takes more mass to do an unpowered landing with parachutes than it does to add a small rocket engine or two.  Primarily I will use a couple of drogue chutes to help slow the rate of descent and leverage the lander's orientation so that the landing engines can be smaller and require less fuel to slow it to a safe landing speed.

As for the landing, I haven't really had much luck with sky crane style deployment.  Basically anything where the wheels of the rover have to take the impact of landing is something I try to avoid, since wheels can be broken by pressure or impact and a drone rover won't have a qualified engineer nearby to fix them.  So often I will have a rover that is smaller than the landing struts on the lander itself, then detaches from the bottom once the landing struts take the impact of landing (I like to stuff a bunch of communication network equipment on the lander and use that as a "ground relay" for the rover.)

For the majority of my Duna rover missions, I actually try to make a rover small enough to fit inside a 2.5m service bay, and build the lander around that.  I can avoid landing struts that way while still keeping the rover safe.  Once it touches down, the bay opens, the rover detaches, and then rolls out onto the Dunian soil under it's own power.

Oh, and just a general note on powering rovers: while RTGs are ideal, they are expensive so you might not want them in a one-way craft, and they only get unlocked near the end of the tech tree so they might not be an option in earlier career and science mode.  That leaves you with solar panels as your power plants for rovers.  One school of thought is to put a bunch of fixed panels across the top.  It charges slow, but continuously.  The other school of thought is to have a deployable solar panel that charges more quickly, but only as long as the panel is deployed.  You want to avoid deploying a panel while the rover is in motion because they are delicate as heck, but even if you choose to go that way I recommend adding at least a tiny fixed solar panel so you can be sure the rover will always have some power left to it.  Otherwise you may end up going back to mission control, then transferring back to control of the rover months or years later to find it was out of power and without power can't process your signal to let it deploy it's solar panels.

[Wolfie2474]

Thanks for the tips guys!

[magnemoe]

On 11/30/2018 at 8:28 PM, Fearless Son said:

I have landed rovers on Duna a few times.  I find that parachutes are helpful, but the atmosphere is so thin that they rapidly hit diminishing returns, it takes more mass to do an unpowered landing with parachutes than it does to add a small rocket engine or two.  Primarily I will use a couple of drogue chutes to help slow the rate of descent and leverage the lander's orientation so that the landing engines can be smaller and require less fuel to slow it to a safe landing speed.

As for the landing, I haven't really had much luck with sky crane style deployment.  Basically anything where the wheels of the rover have to take the impact of landing is something I try to avoid, since wheels can be broken by pressure or impact and a drone rover won't have a qualified engineer nearby to fix them.  So often I will have a rover that is smaller than the landing struts on the lander itself, then detaches from the bottom once the landing struts take the impact of landing (I like to stuff a bunch of communication network equipment on the lander and use that as a "ground relay" for the rover.)

For the majority of my Duna rover missions, I actually try to make a rover small enough to fit inside a 2.5m service bay, and build the lander around that.  I can avoid landing struts that way while still keeping the rover safe.  Once it touches down, the bay opens, the rover detaches, and then rolls out onto the Dunian soil under it's own power.

Oh, and just a general note on powering rovers: while RTGs are ideal, they are expensive so you might not want them in a one-way craft, and they only get unlocked near the end of the tech tree so they might not be an option in earlier career and science mode.  That leaves you with solar panels as your power plants for rovers.  One school of thought is to put a bunch of fixed panels across the top.  It charges slow, but continuously.  The other school of thought is to have a deployable solar panel that charges more quickly, but only as long as the panel is deployed.  You want to avoid deploying a panel while the rover is in motion because they are delicate as heck, but even if you choose to go that way I recommend adding at least a tiny fixed solar panel so you can be sure the rover will always have some power left to it.  Otherwise you may end up going back to mission control, then transferring back to control of the rover months or years later to find it was out of power and without power can't process your signal to let it deploy it's solar panels.

I use fixed unless I plan to do science with it as they don't break easy
If using solar panels you might want a panel on the bottom of the rover Have lost some underway to Mun and Minmus as the bottom of the rover faces the sun. 

Simple skycrane, simply add trust so rover almost take off and stage to remove it

[Wolfie2474]

So now i'm planning to send a rover to the mun...
should i try to make it fit into a cargo bay/service bay?

[Fearless Son]

4 hours ago, Wolfie2474 said:

So now i'm planning to send a rover to the mun...
should i try to make it fit into a cargo bay/service bay?

Putting a rover in a bay is less important when doing a Munar landing since the Mun is completely without atmosphere, unlike Duna.  You don't have to worry about overheating some components due to atmospheric burn, nor about how it will affect drag since you won't have any air to drag against.

However, landing on an airless body presents some other challenges.  Since you can't use chutes, you are entirely dependent on your engines to slow to a safe landing speed.  You will need to plan your delta-v requirements appropriately.  While there are plenty of alternative designs, the most common design for a rover-lander is a sky crane style approach where the rover sits on the bottom of the lander.  An engine on the bottom of the rover itself is probably not a good idea, so you are probably going to have to mount two or more engines radially positioned to expel their propellant past the rover's body.  If the rover is short, you might as well add some landing struts to the side of those radial engines.  Think of the lander as being like a spider with a rover that clings to it's bottom, then drops off and rolls past it's legs once it touches down.  

Remember that the Munar gravity is low.  This has some effects on rover design.  You can drop the rover off the lander without fear of damaging it, but remember to kill the throttle as soon as you touch down, because you are likely to bounce on landing and you need to cancel as much outward force as possible.  The rovers themselves have a habit of flipping over during tight turns or when breaking too fast going down slopes, or having insufficient traction to go up slopes.  This has everything to do with not having enough down force on the wheels for them to grip as tightly as they need to.  Sometimes it can benefit rovers to give them a small downward force by, say, some down thrusting monoprop nozzles, used sparingly when you need a little extra control.  Likewise, good use of SAS can keep the rover level.  Every probe core will include some reaction wheels, plus any you add yourself.  Before launch, set the probe core and reaction wheels to "SAS Only" mode, which will keep you from flipping the rover end-over-end by accident, but will help the onboard core keep the rover level.  Remember to briefly turn the SAS off when on a new slope to level the probe's wheels with the slope, then turn it back on before trying to change direction.  This should keep the worst of the flipping under control.

Have fun!  Landing and exploring with a rover can be an enjoyable and educational experience. 

[Wolfie2474]

11 hours ago, Fearless Son said:

Putting a rover in a bay is less important when doing a Munar landing since the Mun is completely without atmosphere, unlike Duna.  You don't have to worry about overheating some components due to atmospheric burn, nor about how it will affect drag since you won't have any air to drag against.

However, landing on an airless body presents some other challenges.  Since you can't use chutes, you are entirely dependent on your engines to slow to a safe landing speed.  You will need to plan your delta-v requirements appropriately.  While there are plenty of alternative designs, the most common design for a rover-lander is a sky crane style approach where the rover sits on the bottom of the lander.  An engine on the bottom of the rover itself is probably not a good idea, so you are probably going to have to mount two or more engines radially positioned to expel their propellant past the rover's body.  If the rover is short, you might as well add some landing struts to the side of those radial engines.  Think of the lander as being like a spider with a rover that clings to it's bottom, then drops off and rolls past it's legs once it touches down.  

Remember that the Munar gravity is low.  This has some effects on rover design.  You can drop the rover off the lander without fear of damaging it, but remember to kill the throttle as soon as you touch down, because you are likely to bounce on landing and you need to cancel as much outward force as possible.  The rovers themselves have a habit of flipping over during tight turns or when breaking too fast going down slopes, or having insufficient traction to go up slopes.  This has everything to do with not having enough down force on the wheels for them to grip as tightly as they need to.  Sometimes it can benefit rovers to give them a small downward force by, say, some down thrusting monoprop nozzles, used sparingly when you need a little extra control.  Likewise, good use of SAS can keep the rover level.  Every probe core will include some reaction wheels, plus any you add yourself.  Before launch, set the probe core and reaction wheels to "SAS Only" mode, which will keep you from flipping the rover end-over-end by accident, but will help the onboard core keep the rover level.  Remember to briefly turn the SAS off when on a new slope to level the probe's wheels with the slope, then turn it back on before trying to change direction.  This should keep the worst of the flipping under control.

Have fun!  Landing and exploring with a rover can be an enjoyable and educational experience. 

Ok thanks for the help! i'll try it out today

[Fearless Son]

On 12/11/2018 at 3:39 AM, Wolfie2474 said:

Ok thanks for the help! i'll try it out today

One more thing: it's easy enough to get up to a full speed driving across the surface of the Mun if you have enough flat open space to build up a straight-line acceleration, but it requires almost as much space to slow down again.  The aforementioned low gravity means that the friction on the tires is pretty weak, so it will roll for a good long while without adding more power to the drive, and also means that the wheels will slip and slide over the surface even as you hold down the breaks.  Imagine you are driving in icy conditions and you will have a good analogy for how it feels.  If you go too fast, you may find yourself launching into wide jumps off the crests of hills that wouldn't pose a problem in stronger gravity, or unable to slow down fast enough to make a tight turn to avoid a collision without flipping end over end.  Make sure your rear tires are set to use maximum breaking force and try to avoid the temptation to accelerate to top speed if you want your rover to last without smashing itself apart because it lost control.

[Wolfie2474]

15 hours ago, Fearless Son said:

One more thing: it's easy enough to get up to a full speed driving across the surface of the Mun if you have enough flat open space to build up a straight-line acceleration, but it requires almost as much space to slow down again.  The aforementioned low gravity means that the friction on the tires is pretty weak, so it will roll for a good long while without adding more power to the drive, and also means that the wheels will slip and slide over the surface even as you hold down the breaks.  Imagine you are driving in icy conditions and you will have a good analogy for how it feels.  If you go too fast, you may find yourself launching into wide jumps off the crests of hills that wouldn't pose a problem in stronger gravity, or unable to slow down fast enough to make a tight turn to avoid a collision without flipping end over end.  Make sure your rear tires are set to use maximum breaking force and try to avoid the temptation to accelerate to top speed if you want your rover to last without smashing itself apart because it lost control.

ok
i made a small rover using 4 of the wheels that looks like the sojourney wheels and a rovemate probe core
if i fit it into a cargo bay should i put the cargo bay the lowest in the vehicle? or should i try to make a ramp for it? or i just don't need to worry about it because of the low gravity

[Fearless Son]

5 hours ago, Wolfie2474 said:

ok
i made a small rover using 4 of the wheels that looks like the sojourney wheels and a rovemate probe core
if i fit it into a cargo bay should i put the cargo bay the lowest in the vehicle? or should i try to make a ramp for it? or i just don't need to worry about it because of the low gravity

So long as it doesn't get the chance to accelerate more than a few meters per second on it's way to the ground, it should be fine.  You can generally just drop it from a lander.

The biggest worry is if the rover gets stuck on some piece of lander geometry when it detaches.  Like if it fell out of a vertically oriented cargo bay and flipped over, or something like that.  If it can get wheels down on the Munar regolith, you are good to roam.

[Wolfie2474]

After very careful (and not so careful) planning i finnaly designed a crewed rover i named it "Armstrong Rover" in honor to the first man that stepped on the moon
https://imgur.com/YdZMh2n

I couldn't fit a skycrane so i just added some 4 twitch engines