A friend, and more experienced Kerbal Space Program player, says I’ll be landing on Mun (the closer of Kerbin’s moons) in “no time.” I think she may be right.
I’ve decided to make Mun my next goal. I’m going to start with a robotic lander, and not plan for a return to Kerbin. That should make things easier, and no Kerbonauts will be harmed in case things go wrong – and things will go wrong.
I built a basic lander based on some suggestions I found online, and stuck it on top of a simple, short-range rocket. I tried a couple of short flights within Kerbin’s atmosphere. I’d never tried to land a lander with a rocket before. I realized, though, that they weren’t very good tests. The lander’s rocket didn’t have enough trust to land safely on Kerbin, but Mun has less gravity and no atmosphere. So I don’t really know if my lander will work. According to the online suggestions, it should work.
It’s going to be a long process of experimentation, full of failures.
Last night, I decided to launch my lander into Kerbin orbit – just a next step in the process. I ran out of fuel before achieving an orbit, and crashed my lander into the ocean.
One handy feature of the game is that rockets can be saved as a file, so when you crash one, there’s a clone back at the Vehicle Assembly Building ready for the next flight.
I shut the game down last night. But, later, I thought of another design. I started the game again.
I added four more rockets to the first stage, and re-designed the second stage with two nuclear rockets.
(The nuclear rocket is designed for interplanetary travel, according to what I’ve read, but I decided to experiment with it.)
I launched my new design last night. The first stage got my lander to almost 60 kilometers. That’s pretty impressive. Then I achieved an orbit. It was a terribly elliptical orbit, as is typical of my orbits so far. But it was also an inclined orbit – not an equatorial orbit recommended for a Mun launch. That usually doesn’t happen. It should have been a clue, but I didn’t see it yet.
I got to the periapsis and tried to correct my orbit. I still had a lot of fuel in that second stage. I corrected it to the most circular obit I had ever achieved – something like 78 km on one side and 82 km on the other side. But I couldn’t figure out how to change the inclination while keeping that nice circle. That was OK. It was merely the next step in the experimentation. I had achieved an orbit.
I was noticing that my rocket, even with the short second stage, was very difficult to control. I still didn’t see what the problem was.
It was getting close to bedtime. I was ready to shut the game down. Even though I’d been saving the game at critical points, I was going to terminate the ship and start anew on another day. So, I figured I might as well play around a bit – just to see what would happen.
I lined my ship up with Mun and fired the rockets as it appeared over the horizon, just like the tutorials say to do for a Mun launch.
I watched the map as my ship’s orbit reached out past Mun’s orbit. I still had a lot of fuel left. But no encounter with Mun showed up on the map. I didn’t understand it. I’d done what the tutorials told me to do, but the map was telling me I’d miss Mun.
Then I remembered that my orbit was inclined. I tilted the map and saw my ship’s orbit passing far “above” the orbit of Mun.
I played around with a maneuver node until the apoapsis of my ship’s orbit lowered. Suddenly – there was a predicted encounter into an orbit with Mun.
I couldn’t believe it. Even though I’d been expecting to merely send the ship up and end it, I was actually going to get to Mun.
I got close to the point of the course correction, and started to line my ship up. At first, I couldn’t get the ship to turn. Then, I couldn’t get it to stop spinning.
Then I understood the problem – I think. My ship was off-balance. (Even an object without weight has mass, and therefore inertia to overcome.) When I’ve been building ships, I’ve been forgetting to use the “center of mass” tool.
I terminated the ship, shut the game down, and went to bed. I felt very optimistic about how much I’d accomplished last night. All I’d intended to do was achieve an orbit, I was expecting failure, and I almost made it to Mun.
Next, I’m going to investigate that center of mass. If that’s not the problem, or even if it is, there are other things I can try out: RCS thrusters, inline reaction wheels, different engine configurations – maybe replace those nuclear rockets with rockets featuring thrust vectoring.
Kerbal Space Program is one reason I don’t watch television these days.