help me improve my rover

[king of nowhere]

I am working on a multipurpose rover, it works magnificently at most of its tasks, yet it has a couple of weaknesses i could not manage to fix; i have to ask for advice

the rover has many functions:

1) fuel transfer between ISRU facilities and landed ships.

2) collects science

3) can land and take off under its own power on all planets without thick atmosphere (up to duna)

4) is fun to drive from a first person perspective (hence the cupola module oriented for better view of the ground)

5) survives capsizing at high speed

6) can operate in a wide range of environments

the rover has around 15 tons of dry weight, with capacity for 32 tons of fuel

https://imgur.com/a/OuInRNY

it does those things quite well, but it has a few weaknesses

a) the rover has a hard time moving uphill. the slope limit depends on gravity and amount of fuel, but it's pretty low. fully loaded, on mun it can't take much more than 10 degrees. even on minmus tiny gravity it can't climb steeper than 30 degrees. this makes it almost useless for moho and duna.

unfortunately, the only ways to fix this that i see would be more wheels and/or bigger wheels. i already put as many wheels as i could fit on that design. as for bigger wheels, I'm already using the TR-2L model. the only model bigger than that is the XL3, but those things are super heavy. even if i swapped out 10 old wheels for 4 new ones, i'd still add 4 tons of weight. way too much. i guess i could use the hinges to angle my rockets backwards. i don't want to have to rely on consumable fuel just to move around a planet, though. and while i don't need it fully loaded, i'd like to be able to move around a planet with enough fuel to take off. which, in duna's case, means between one half and one third of full load.

b) the thrusters don't give uniform push.

this is harder to fix because the center of mass of the vehicle changes with fuel load, as evidenced by the image. however, the asymmetry of the push is small, and i was hoping the SAS system could compensate it. indeed, it can at low thrust. my previous version of this rover was able to achieve orbital manuevering, orbital rendez-vous and docking and a minmus landing, despite being more unbalanced than this one. however, taking off from mun is complex, the rover risk spiraling out of control. i managed after a couple of tries. i could not manage to take off from moho without losing control (i could land just fine from orbit). by the way, that was done at full load, when the center of mass and center of thrust align almost perfectly.

the problem is made worse by the hinges vibrating and further messing thrust direction: the rover is much more stable with the thrusters pointing upwards, but it needs to rotate the hinges downwards to take off (so the hinges are the most unstable right when i need more thrust). I need to explain why i made it like that. Originally, there was only one thruster, and its purpose was to right the rover in case it capsized. only later i realized that since i already has a rocket and a fuel tank, it would be easier and cheaper to strap on some additional engines and make the rover fly than it would be to design a whole cruise module and a landing module and adding them to launch mass. but i still need the rocket to work as anti-capsizing mechanism, so i still need them to be able to point upwards. also, the hinges allow the rockets to be safely retracted to be protected by the landing struts in case of capsizing.

the original plan called for intentionally capsizing the rover in order to take off (i know, it looks silly ). but the rover will just lean on the side, and it's quite hard to take off like that. so, i had to include the possibility to rotate the thrusters.

i could try to control the vibrations and asymmetrical thrust with a big reaction wheel. i could also use the stronger, heavier hinges. but i'm quite reluctant to add even more weight.

the push asymmetry could also be controlled by manually setting a thrust limit for some of the rockets, but it needs to be fine-tuned, and there is no way to do the tuning without firing the rockets and seeing if the push is uniform. if it's not, it's generally too late to fix things. and of course it must be continuously changed to accomodate shifts in the center of mass caused by fuel consumption. so, it's virtually impossible to make it work in practice

c) the rover still breaks for taking a bump at high speed

the safety struts work very well under normal conditions. i run many tests accelerating to 30 m/s (which is basically top speed with those wheels, and anyway it's top speed on most planets because low gravity will make the rover unstable; in fact, on mun it's hard to drive above 20 m/s for long without capsizing), and i never had any damage. directly slamming on the ground is another matter, though. in particular, taking a bump in the ground at high speed can break the front wheels, if the bump was steep enough. i tried putting the front low struts to try avoiding this problem, but turns out they also can't support a direct impact with the terrain at high speed. i may just have to drive more carefully around rough terrain, if there is nothing to be done about it.

 

any suggestion on fixing those issues without creating more problems somewhere else? is my dream of a rover fulfilling the 6 goals even feasible, or do i have to accept mediocrity somewhere?

 

Edited June 22, 2020 by king of nowhere

[AHHans]

Quote

I am speechless!

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Seriously: I don't know what to say!

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Well: Very Kerbal!

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I like it.

3 hours ago, king of nowhere said:

the problem is made worse by the hinges vibrating and further messing thrust direction

Do you lock the hinges when they are extended? And are you using autostruts (to grantparent) on the terriers? The combination of both should make it a lot more stable. (Not stable^(TM), but more stable!)

3 hours ago, king of nowhere said:

in particular, taking a bump in the ground at high speed can break the front wheels

Do the wheels get damaged - i.e. in the way that a sufficiently skilled engineer can repair them -  or do they break off? In the latter case: do you use autostruts on the girders between the tank and the wheels?

P.S. To insert an image into the forums you need to insert the direct link to the image in the "Insert image from URL" window. I.e. an URL that ends on *.jpg or *.png or so. One way to get that URL is to right-click in the browser, select "view image", and the copy&paste the URL from the address bar of the browser.