Ion Engines for a Rover?

[Guest Aaack]

So Yesterday I've learned that if you leave a light rover parked in a slope it will move regardless it's breaks.

I needed to move another rover from a lander to a base on the mun, a 6 km ride. The first time I reached the base I saw how the rover collided against a fuel tank, made half base explode, killed two kerbals and littered a ton of pieces all around.

The second time and who knows why the rover just "jumped" alone almost escaping the mun to smash on the other side of the moon making a huge crater.

Ooook, time to change the rover.

So! I was thinking in another thread where several clever guys added rockets pushing down the rover to add more grip while riding it at high speeds.

What do you think guys? an ion engine or two can help holding it to the ground too?

[HoY]

Ion engines won't do a spectacular job at it honestly. They will help but their thrust is so low you may as well just add a little more weight instead. On The Mun anyhow.

On a little piece of sand like Bop this idea works much better as long as you have the power to run them. Solar panels are half as efficient out there, and twice as effective on a moon like Ike.

[Umlüx]

i don't think the thrust would be enough. plus you would need an insane amount of generators. you need about 30e/s for two ion engines and one generator only gives you 45/min.

i would try this approach with some RCS thrusters. but then you need some means to refuel the rover.

[Cheebsta]

Ions are roughly equivalent to a Kerbal blowing air through a straw. I don't think they will be enough either, but that certainly wouldn't stop me from trying it anyways

[Guest Aaack]

I was doing tests, but you both are right, the ions are pretty attachments and little else.

The thing is I didn't want to deal with fuel (not much at least, the xenon eventually will deplete), that being said, the thing looks COOOOOL so far lol

[Tw1]

Perhaps there is something else that is causing the sliding problem. If you use physics warp, things tend to slide whatever you do.

[Guest Aaack]

I never used the physics warp, honestly I don't know why should anyone try to accelerate the physics calculations?

I think that the rover is just too light, i was very conservative on the design of that thing, instead to go way WAY over the top as always, I tried to make something easy to put up there...

Edit: the rover is not the only thing that skids, I left two kerbals out waiting for the third one (those are the ones that were killed inthe explosion), the second time when my haunted rover decided to go into orbit I found my kerbals really far away from where I left them. together in the same position but translated about 50 meters. I guess... it was the skidding, because the rover was really away from the path of them, so I discard being "pushed" away.

Edited July 22, 2013 by Aaack

[Tw1]

I never used the physics warp, honestly I don't know why should anyone try to accelerate the physics calculations?

.

Physics warp accelerates time but lets you keep doing stuff. It's really useful for long drives, flights, burns, or whatever, provided everything is running stably.

What kind of slope are we talking here? Could we get a navball reading?

[Guest Aaack]

What kind of slope are we talking here? Could we get a navball reading?

Sure!

Edit: I didn't know about it, I knew about physics warp but didn't know it was some sort of "multitasking" warp, however i never used it...

[capi3101]

So the idea is to provide downward force, right? To prevent rollovers...

You might try mounting them to the sides. Big question is going to be power; two ion engines are going to require at least 30 RTGs for power. And then you get two kN of downward thrust.

You'd probably have better luck by adding a standard SAS module to the rover, widening the wheelbase, locking the steering on the back wheels and driving around with the docking controls.

It's a neat idea, I'll grant you that. If you try it, lemme know how it turns out.

That is a neat looking rover design, I'll grant you that.

Edited July 22, 2013 by capi3101

[Guest Aaack]

So here's some shots of the rover, it's 80 parts and a mass of 6.23 tons. Ill add some antennae and a couple of extra battery packs before it's done.

It has an ASAS and between the modules and the probe enough gyros to keep them mostly stable in kerbin, so i assume will be even more stable on the Mün.

Also I added landing struts as "parking brake" to prevent accidental slidings.

About the ions, I think ill use them as extra help to prevent tip overs in case of sudden brake.

Parking brake on...

Eye candy solar panels deployed, there's some clipping but ill survive...

Assorted views:

I tried to keep the gravity centre really low, and I think I got it right as I can turn at 22 m/s on kerbin without roll over.

[CodatheSpaceFox]

Well, here's hoping any on mun tests prove some worthy results. One way or another though, you have a good skill in designing unique rovers.

[Guest Aaack]

Thanks man!

I can tell something I just discovered making tests at the launchpad. I thought the solar panels were mostly eye candy but they are incredible efficient, I did two tests with everything on (wheels running while having the landing struts down and the ion engines), to see how fast it depletes the electric energy, it takes about 120 seconds with the ion engines throttled to the max.

But during the day with the solar panels deployed takes about 60 seconds to recharge everything. At night it takes about 3 or 4 minutes to do so using only the 8 thermal generators.

I don't have more space to add more solar panels but it's very interesting how much an "eye candy" can help!

[WhiteWeasel]

Thanks man!

I can tell something I just discovered making tests at the launchpad. I thought the solar panels were mostly eye candy but they are incredible efficient, I did two tests with everything on (wheels running while having the landing struts down and the ion engines), to see how fast it depletes the electric energy, it takes about 120 seconds with the ion engines throttled to the max.

But during the day with the solar panels deployed takes about 60 seconds to recharge everything. At night it takes about 3 or 4 minutes to do so using only the 8 thermal generators.

I don't have more space to add more solar panels but it's very interesting how much an "eye candy" can help!

How are solar panels eye candy? The smallest solar panels provide just as much energy at 1/16th the weight as an RTG. And the very largest solar panel can power a single ion engine at full thrust with ~20% power output (assuming in full sun) to spare.

[capi3101]

Why ASAS as opposed to SAS?

[WhiteWeasel]

Why ASAS as opposed to SAS?

SAS only stops rotation.

[Guest Aaack]

Hey White!

Well I didn't know, I'm still learning, simple as that ^^

These kind of crazy stuff are the things that shows me how things work in KSP!

About the ASAS... I figured out that if I add a SAS on my rover it'll use just the gyros provided in it. ASAS would use all the gyros of the probe and both cockpits. Right?

[Tw1]

Sure!

-snip-

Wow, your stuff should not be slipping on such a low slope.

This would slip a bit, but not much.

Something doesn't seem quite right.

[Guest Aaack]

Yep, it's possessed by the spirit of an angry kerbal. I put two refuel stations on Kerbin's orbit, a massive station over the mun, two rovers, two landers and a base to rescue the very first mission to the mun, a single and poor kerbal stranded there.

... to discover i deleted it in some history's moment without noticing, I believe now his spirit is angry at me for taking so long to replentish his sandwichs stack...

[WhiteWeasel]

Hey White!

Well I didn't know, I'm still learning, simple as that ^^

These kind of crazy stuff are the things that shows me how things work in KSP!

About the ASAS... I figured out that if I add a SAS on my rover it'll use just the gyros provided in it. ASAS would use all the gyros of the probe and both cockpits. Right?

Close enough, SAS just adds torque to stop rotation (movement on the axis controlled by Q &E) when activated. ASAS has no power of it's own but uses other control surfaces such as winglets, RCS, torque from the command pods, etc...

[draeath]

I like your idea of using landing legs as a "parking brake"

When I build a kethane miner I think I'll be borrowing that idea

[Guest Aaack]

Hey Draeath!

Well I never played with the ketane add-on. But check the height on the launchpad, those things are very tall and stress a lot the rover when they're deployed. Granted, on the Mün there'll be lot of less stress due the reduced gravity but I don't know where do you plan to mine so... just test it a lot lol.

Close enough, SAS just adds torque to stop rotation (movement on the axis controlled by Q &E) when activated. ASAS has no power of it's own but uses other control surfaces such as winglets, RCS, torque from the command pods, etc...

White, so in this case having an ASAS operating 3 sets of gyros is more efficient than put a simple SAS to stabilize the rover, is that correct?

[capi3101]

Close enough, SAS just adds torque to stop rotation (movement on the axis controlled by Q &E) when activated. ASAS has no power of it's own but uses other control surfaces such as winglets, RCS, torque from the command pods, etc...

My understanding of the whole ASAS vs SAS function is that ASAS provides no torque of its own, that it's good for controlling heading, whereas SAS provides torque to stop rotation. ASAS has no power to stop rotation on its own. So if the point of adding it is to help prevent rollover, SAS would be the better option; in my experience, pod torque causes rollover, particularly if the rover's being controlled in staging mode instead of docking mode. You'd save a bit of weight too.

[WhiteWeasel]

Also to help you with future power problems, I made this little contraption that shows off all of the power sorces:

Basically it has all of the power generating/related items on it. Has all the battery types on it, but you know what they do.

For the solar panels and RTG:

OX-STAT, The smallest solar panel .75 E/s (Electric charge a second, also assuming full sun) They do not follow the sun, but is more durable and don't get ripped off from drag in return.

An RTG is basically a OX-STAT that works at all times, but is much heavier and therefore less efficient in e per ton. But makes sure your probes don't permanently die from running out of power. So at least one is good. But you don't usually need more. Plus you can get more 'usable' power from batteries than the same weight from RTG's

The next size up is the 1x6 and the 2x3 panels that can be extended and retracted and rotate to face the sun. Both of them produce the same amount of electricity, 2 E/s, and has a counterpart in more protective (in impact/bumping into stuff) white cases that are a bit heavier. Note that 'folding' panels can be ripped apart by atmospheric drag. So retract, don't have them out them when moving in non-vacuum.

The largest is the gigantor solar panel with a whopping 18 e/s. Nuff said.

Also to calculate how much power you need here are the consumption rates of parts assuming full speed/thrust:

Illuminator MKI (round light) .04 e/s

Illuminator MKII (Box light) .02 e/s

Rovemax model 2) .5 e/s

Rovemax model 1) 1 e/e

Rovemax model 3) 2 e/s

TR-2L .70 e/s

Ion engine 14.442 e/s

As you can see you don't need all that much power unless you using ion's or a lot of rover wheels. A good rule for ions is one gigantor per ion on ship. For most rovers an RTG or two and a few batteries should be good. Add in solar panels as needed. Also note that solar panels are half as strong at Jool and Eloo due to being farther away from the sun.

Edited July 22, 2013 by WhiteWeasel

[Guest Aaack]

Wow, very very interesting, thanks for sharing the results of your test!

Im at the landing on the moon process, the thing is so stupidly wobbly (for once i forgot to add struts in my hurry to take it off to the mun) that I'm not sure if I'll be able to land it safely, but... I'll try! After I land I'll test the ion engines as a way to improve the grip of the rover. If it works Ill try to design one with big solar arrays.

+

I didn't know that the RTG were so weak, ( and I never really checked the numbers at the VAB either, you can blame me, I'm a lazy ass).