Designing a jet powered rover

[creator1629]

hello, i am trying to design a jet powered rover for the purpose of... well... just going fast really and i had some questions regarding how to go about it

1. the actual rover wheels seem to suffer failure after exceeding certain speeds, which of course causes a major crash, is the only way around this, using the landing gear as wheels instead of the actual rover wheels?

2. i want to somehow generate downforce to keep my wheels stuck to the ground much in the same way that race cars do, but the wings in the game only generate upward lift. is there another option, like angling my main jet engine pointing down a few degrees to press the craft to the ground while driving fast. or having secondary auxiliary engines on the rover pointing straight down to generate the downforce?

3. braking at high speeds is a bit slow when using the conventional braking systems. im looking for other options around this, but the only ideas i have come up with are either having a secondary engine facing front which i can trigger with an action group, or using parachutes, but the problem is that they aren't reusable. do you guys have any other ideas?

[Sir Nahme]

chutes are re-usable if you have a kerbal who can eva and repack them

[Vanamonde]

1. Use the old, airplane landing gear wheels. They can go much faster without failing, but will need some strut reinforcement so they don't flex under strain and send the vehicle tumbling. 2. Wing surfaces angled down will apply downforce, not as an air foil, but simply as an inclined plane. 3. Parachutes can be repacked by a Kerbal on EVA, but do use an action group to deploy them, because for some reason resetting the staging doesn't re-trigger the chutes.

[RawChicken]

Pretty much what Vanamonde said.

As for the downwards pull, i dont know which is better, wings or engines. Make a couple designs and post them here!

[HoY]

The chutes won't work to slow you down unless your airborne. They disappear as soon as you touch the ground

There's no reason you can't angle your engine down a little to keep you on the ground, and you can edit the stock wheels .cfg to increase their speed tolerance quite easily. Also, your idea for a second engine to slow you down is probably the best way, but I'd avoid using it unless you need to stop Now, to save fuel. The brakes would slow and stop you faster than a jet engine would spoil up so the retro engine would need to be a rocket. If you want to use mods, I think there's a jet engine or turbofan with fire spitter that lets you instantly reverse its thrust? At least I think that's the pack it came with! Throttle down before you reverse it or it may rip off your craft

[creator1629]

Thanks for the info guys, i had no idea a kerbal could repack parachutes, that is definitely good to know. Unfortunately as HoY said they don't really work if you are on the ground already, i learned that the hard way when i deployed them and they just disappeared. I guess i should just anticipate my goal and start applying the brakes early.

Oh great to know HoY, thanks, i hadn't considered increasing the speed tolerance of the wheels that way. that should let me experiment with several more designs.

the last problem is the downforce, im thinking of making a version for the mun by replacing the jet engine with a rocket engine. and since the mun has much lower gravity, the downforce is even more important. the lack of an atmosphere here will make using wings obsolete though

[HoY]

It will also make the jet engines useless for downforce consider using some ion engines, or ant engines. You won't need much. (For mun that is) you could also use a damned robotic hinge to gymbal your rocket engine to point it slightly up if you need more down force than the little engines are giving. Mun speed rovers like that tend to need to be large to carry lots of fuel, or are small and don't have enough fuel for extended play time. Either way you'll want to use an LVN for the forward and I'd use a single or pair of ions for downforce to have the most efficient drive setup. You know.. Unless you consider solar powered rover wheels more efficient lol

[EndlessWaves]

You can increase both the braking force and the speed at which wheels break by editing the part.cfg file for the rover wheels (it's just a plain text file).

[creator1629]

@EndlessWaves: oh hey thanks, yeah that would be very useful especially if i have to perform an emergency braking maneuver

@HoY: oh hey yeah i had never thought of using a nuclear engine to propel my rover, but its high isp means i can run longer than with other engines. true, solar powered rover wheels are technically more efficient but what im really looking for is speed. you mentioned a pair of ion engines to produce the downforce, but considering the very low gravity of the moon, are 2 ion engines enough to get the grip you need for speed?

[HoY]

It depends on how much speed honestly. If you want to sail across the ground at over 100m/s then yes, for the duration of your 'trip' your rover will be on the ground. Unfortunately the duration will probably only be 30-45 seconds

Down force while on flat ground is one thing. But you hit a bump? A bump at 100+m/s will propel you upwards extremely fast. If I were to do something like this it would have 4 LVN's, one on each corner pointing towards the rear, and all tilted up by about 10 degrees. (I say this without testing but those numbers sound like they would work).

[HoY]

It depends on how much speed honestly. If you want to sail across the ground at over 100m/s then yes, for the duration of your 'trip' your rover will be on the ground. Unfortunately the duration will probably only be 30-45 seconds

Down force while on flat ground is one thing. But you hit a bump? A bump at 100+m/s will propel you upwards extremely fast. If I were to do something like this it would have 4 LVN's, one on each corner pointing towards the rear, and all tilted up by about 10 degrees. (I say this without testing but those numbers sound like they would work).

[creator1629]

yeah maybe cruising at 100 m/s on the mun and have it be stable is asking a bit much. maybe something along the lines of 50-60 m/s would be better. instead of 4 nuclear engines on each corner how about just one in the center angled up 10 degrees with the rover frame built around it? with the newly released rover wheels having 30 m/s top speed, i would only need a little extra throttle to hit the 50-60 mark thus conserving fuel. what do you think?

[Colonel_Panic]

hello, i am trying to design a jet powered rover for the purpose of... well... just going fast really and i had some questions regarding how to go about it

1. the actual rover wheels seem to suffer failure after exceeding certain speeds, which of course causes a major crash, is the only way around this, using the landing gear as wheels instead of the actual rover wheels?

2. i want to somehow generate downforce to keep my wheels stuck to the ground much in the same way that race cars do, but the wings in the game only generate upward lift. is there another option, like angling my main jet engine pointing down a few degrees to press the craft to the ground while driving fast. or having secondary auxiliary engines on the rover pointing straight down to generate the downforce?

3. braking at high speeds is a bit slow when using the conventional braking systems. im looking for other options around this, but the only ideas i have come up with are either having a secondary engine facing front which i can trigger with an action group, or using parachutes, but the problem is that they aren't reusable. do you guys have any other ideas?

I don't think chutes work for land vehicles. I've tried them before to try and stop a plane on the runway, but if your wheels are touching the ground the parachute will automatically cut itself loose immediately. You can combine rover wheels with aircraft wheels so at high speeds you can lower the aircraft wheels to lift the rover wheels off the ground.

beware of your vehicle's propensity to tip over when turning at high speed. You can use outriggers to prevent this.

[creator1629]

oh ok cool. what do you mean by outrigger?

[Flixxbeatz]

hello, i am trying to design a jet powered rover for the purpose of... well... just going fast...

I'm sure you want to do something like this:

Well the major problem you'll face is that the wheels are made to "pop" once you've reached a certain speed, as demonstrated here. You can use the old runway wheels, but you won't be able to maneuver it, let alone accelerate by itself. Or try a runway wheel/rover wheel combination

[42undead2]

There is also TT Omni Wheels. With suspension and steering, and they won't pop, they seem like the would be the best.

[drakesdoom]

I have seen rovers that use ion engines and plane landing gear reach orbital velocity on the minmus flats. On the mun you would have to go twice that speed and there is no where so flat but still keep in mind there is a hard speed limit where you stop driving and start orbiting.

[Flixxbeatz]

I have seen rovers that use ion engines and plane landing gear reach orbital velocity on the minmus flats. On the mun you would have to go twice that speed and there is no where so flat but still keep in mind there is a hard speed limit where you stop driving and start orbiting.

Not to mention the speed where steering will apparently "lock" and you won't be able to turn your rover anymore (or turning may cause it to tumble) - around 20+ m/s on the Mun (0.18.2 tested, ion-powered) and 13+ m/s when using large rover wheels.

Edited May 25, 2013 by Flixxbeatz

[Colonel_Panic]

oh ok cool. what do you mean by outrigger?

like this. http://forum.kerbalspaceprogram.com/showthread.php/31212-Testing-Jeb-s-new-flying-car!?p=384668#post384668

[creator1629]

well what i have done is modify the rover cfg file so that instead of the wheel failing when it hits 60 m/s it only fails at 300 m/s which gives me a nice margin seeing as to how my rover isnt stable on uneven terrain above 150 m/s. another problem is that at high speeds, instead of the wheels failing they just get detached from the girder holding them to the main body, i have somewhat rectified this by adding struts between the wheels and the girder segment, but im still looking for ways to increase the stability further at high speeds