Expecting Failure

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.


5 thoughts on “Expecting Failure

  1. Great post. I’m almost thinking about starting a blog to chart my own adventures. I think my biggest achievement so far is orbital rendezvous. I haven’t figured out the manoeuvre markers – I just stick to the compass, and prograde/retrograde burns, to do Hoffman Transfer orbits to get to places. I have figured out how to change the axis of orbits though (with trial and error, and a good deal of “lets try that, and see what happens in the map view”).

  2. To enhance our virtual escapism – we’re planning on linking 3 monitors together (in a crescent line) therefore being able to sit “in” the game instead of in front of it. We use Flight Simulator, the skies and landscapes are stunning. Takes appropriate software to accomplish – results are amazing!

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