As I mentioned in last week's update, my latest (and second-to-last) science purchase was the top-end rover wheels. I've not been all that impressed with the concept of rovers in KSP. I've played with them, sure. I even did something semi-ridiculous with them back in January. But I eventually reluctantly concluded that "there isn't much there there." There aren't enough biomes on distant locations to make rovers worthwhile. On the places where there are enough biomes like the Mun and Minmus, the distances between the biomes is too long to make rovers practical.
Driving rovers is also very quirky: a rover with multiple axles tends to want to flip or roll over. This happens due to the rear drive wheels tending to push the forward drive wheels into the air rather than into the surface. This problem is exacerbated by low gravity. Turning is also an issue for the same reason: there isn't enough mass pressing down on a rover's contact patches at moderate speed in low gravity to ensure a safe turn.
Still, a few things conspired together to encourage me to take one more swing at a mobile vehicle.
- Action groups which I learned from working with space planes could be used to address the wheel balance problems.
- A heavy lifter could put even a particularly heavy wheeled vehicle on the Mun without too much difficulty.
- The experience I've picked up landing oddly-sized and shaped vehicles could be turned toward a horizontal lander.
- I confirmed the landing wheels of such a vehicle could be repaired on site if needed.
- I know for a fact that I could perform a precision landing within a few hundred meters of a set target, having done that before.
- And finally, a science lab on the Mun could be used as the basis for a permanent base.
What I ended up with was a goofy little train-like vehicle. My plan was to put the thing into orbit and land it conventionally like my very first tall skinny Mun probe... except this time I'd count on the thing tipping over in the direction of its highest mass, the wheels. I was pretty sure that I could deliberately jinx the landing a little bit to encourage the vehicle to fall over in this direction. Just in case this didn't work, I also equipped the thing with a pair of the smallest solid rocket boosters deliberately aimed in such a way as to push the vehicle onto its "side"... onto the wheels.
The "base" itself was the game's Mobile Science Lab with a Cupola on one side and a docking port, large size probe core, and large size battery on the other. Across the top, two of the largest solar arrays and a communications array, plus all of the science instruments. The landing stage would be a small fuel tank, a Poodle engine, and six landing legs at the end of a docking port facing the opposite direction. I loaded the vehicles with my three stupidest kerbals and off it went. Once the thing was down, I'd cut the landing stage loose, repair the wheels, and there I'd be on the Mun with a mobile science lab rover hybrid.
And amazingly, the thing worked on the first go, landing within a kilometer of my eyeballed target point! I broke four of the six wheels tipping it over but the pilot hopped out with a hammer and a screwdriver and soon all four were fixed. I didn't even need to use my two little SRBs. The hardest part was not to damage the solar arrays while climbing back aboard. The discarded landing stage even made for a fun photo opportunity.
Once I was down and the science mods had sampled my Midlands landing point as well as the nearby Northwest Crater, I turned my vehicle northwest heading toward the Northern Basin. The plan was to sample a Midlands Crater on the way. And off in the distance I spotted something that didn't quite fit with the rest of the terrain (it's in the middle right side of the horizon)...
I'd read here and there about easter eggs on the Mun but this was the first one I'd seen. I headed off in that direction which gave me the opportunity to try out action groups again. This time I set one action group to disable to rear drive wheels. This was intended for flat terrain and climbing hills; without the rear driving wheels engaged, the vehicle wouldn't tend to throw its front tires in the air. For going downhill, I had a second action group to do the opposite: shutting down the forward drive wheels would prevent them from causing the vehicle to face-plant when braking. I also set up a third action group to disable steering of all but the front wheels. At speeds greater than 8m/s, steering with all six wheels threatened a flip-over. With one set of turning wheels instead, turning at higher speeds became safer.
Once these groups were working, I had no problem with the 23km drive to the feature that I'd spotted, which turned out to be an arch rock formation. I guess there are people that like to fly through it. ;-) I planted a flag and noted its location for future reference...
From there, it was about a 5km drive to a Midlands Crater and another 15 or so into the Northern Basin. Not too bad, but still not an experience I'm in a hurry to repeat. Unlike Ben Affleck's ride in Armageddon, mine didn't come equipped with rocket boosters. Every gully and crater was an obstacle that had to be driven around and though my mobile lab negotiated 30 degree slopes with ease, anything greater was a serious danger to the crew.
Once in the basin, I parked the vehicle. The rear docking port, by the way, was just for fun. Over the weekend, I used the same design to land a "Hitchhiker" on the same design chassis with more solar arrays and a couple of off-axis docking ports. I eventually got the two modules docked together, though I had to slam them together a couple of times to get the ports to connect... ;-)
EDIT (18/Mar/2014): For those interested, here's the final version of the Munbase. I doubt very much I'll dock anything to those off-axis ports, but they're there.
The resulting science allowed me to purchase the very last item in the tech tree that I hadn't picked up yet, Nuclear Propulsion.
I'm still gonna do a Jool mission, but this futzing about with easier objectives is sometimes fun, too...