Kerbal Space Program: To the Mun and Back

Docked in Munar orbit

It’s not that there’s not a lot to do in Kerbal Space Program; it’s that it takes so long to do.

Just like real space flight.

I’ve been doing work on my heavy lifter, the Munar Exploder. My goal here is to get into Kerbin orbit with a full stage of fuel left. I was hoping to ease the need for fuel by skipping the Kerbin orbit and just burning straight for Mun, but the necessary burn took too long and pushed me past the apoapsis, sending me on an inescapable trip back to the ground, strapped to a hundred ton bomb.

I couldn’t even MAKE orbit with the engines I had on my third stage, so those needed upgrading, and of course stronger engines need more fuel, which means more weight, which means more engines…

Anyway, work on the M.E. continues. Since this version of the Exploder carries a Munar lander, for one test I sent it off to Mun. I used all the lander fuel getting to a Mun transfer orbit; I had to let Mun capture the capsule, then use RCS thrusters to enter orbit.

While I was there, I figured it would be fun to dock with the orbiter I’d sent there a few days ago. I’d practiced meeting another spacecraft in orbit on the “Marooned” mission, but this was different: I was going to try a dock, so it wasn’t going to be enough to just get really close. I was going to have to get everything lined up exactly.

Docked first try. After about an hour and a half of orbit matching and slow, slow positioning.

Once the craft were mated, I took the orbits down to 10,000 meters for some surface skimming fun, then used the remaining fuel in the orbiter to escape Mun orbit, used RCS from there to return to Kerbal, though it took a few orbits to do so.


Both craft splashed down safely within meters of each other.

If this reminds you of the Apollo spacecraft, well, there’s a reason. I’ve been working from the Wikipedia page of the Apollo and the Saturn V heavy lifter, trying to figure out how to get these things working in game. The Saturn V was a huge rocket; KSP does not seem to be able to construct rockets that powerful. Even that giant rocket took three stages to get to Earth orbit.

Planetary exploration still seems out of reach. I’ve not even managed to deliver a fueled-up lander to Mun, yet.

Kerbal Space Program: Marooned


There’s this movie that used to come on TV occasionally when I was a kid called “Marooned” — stars Richard Crenna, Gene Hackman and other famous people. Three Apollo astronauts are trapped in orbit with air running out. A desperate rescue mission on a military rocket that is in no way ready for launch is proposed. It’s a really great movie.

I didn’t set out to remake this movie in Kerbal Space Program….

After upgrading to the full version of Kerbal Space Program, I was testing different rocket designs to try and make orbit gracefully. There’s a lot of new kinds of rockets, so I was trying to get stuff that looked like the space shuttle launches going (way too unstable for KSP) or just stacking stuff as high as I could get to see if that helped (unstable and heavy). SOMEHOW I managed to get my guys into orbit. With no fuel left for a return. And without RCS thrusters to help de-orbit — I didn’t know how to use those, then.

So this is important. Always have RCS thrusters and RCS fuel available on your last stage.

In KSP, you can leave your current flight and go back to the Kerbal Space Center and do more research or flying, what have you. This lets you leave satellites or space stations in orbit so you can return to them later, or do other things while planetary missions are in progress. I did this, leaving my Kerbals in orbit. My new mission — this being a sandbox game, at the moment you make your own missions, and this was mine — rescue those Kerbals.

I needed a new rocket, but first I needed to learn how to meet another object in orbit. I watched this video by Scott Manley maybe three times to understand everything he was doing. It is NOT as easy as he makes it seem. But his techniques DO WORK.

Also, how does he get away with such a simple looking rocket? That’s not what mine is like.

Interceptor v1.5

Here’s mine, version 1.5 of a series that went from 1.0 to 1.8. But this was the best. Command pod is an airplane type, because in “Marooned”, they are met in space by an experimental space plane. Wings because they look cool. Below that is the passenger module, big enough for four Kerbals. This module includes radial parachutes and RCS thrusters. Connecting the two are a ASAS, an anti-spin ring, and RCS propellant.

Below that is the second stage orbital maneuvering section, with a tank of fuel and a “poodle” engine.

Below that is the main stage with a heavy lifter engine and two layers of solid rocket boosters to help this thing get through the thick part of the atmosphere. This rocket gets right to orbit with about half a tank of fuel left in the orbital stage — enough to get to Mun, or to do a fair number of orbit changes.

So this was last Sunday.

Even with the tips in the video, I could not get anywhere near the marooned Kerbals. It was very frustrating. I’d spend hours working on new rockets. Once I came within 2km of the lost spacecraft, but I just couldn’t match orbits

If you’ve followed along on Google+, you’ve seen these postcards before. I needed to make something out of each night’s adventures.

Anyway, last night I figured out Hohmann transfer orbits (for which there is support in game) and was able to quickly switch to higher and lower orbits to catch up to and meet the other craft. Then came the agonizingly slow matching of orbits when the ships were about 20km apart. One of my docking tests of the previous night went well until the two ships crashed. There may have been an explosion in space. Thankfully, no Kerbals died, and I was testing docking in a ballistic trajectory and not in orbit so everything was always going to come back to Kerbin.

It would have been a tragic irony if the rescue attempt ended in a fiery collision. So I wasn’t going to let that happen.

Having finally learned what all the markings on the nav ball meant, I was able to align my direction of travel with my target, and use the vertical and horizontal abilities of the RCS thrusters to line everything up perfectly. You can’t chase the other ship. Have to kill relative velocity, then use left/right and up/down thrusters for positioning.

Finally the spacecraft was in sight, and then there we were. I used “[]” to switch to the other ship and evaced a Kerbal. He let go of the hatch ladder and just floated senseless in space. Another quick look at the keyboard reference — ah, have to turn on his jetpack with “R”.

With that, he was able to bump into the passenger module hatch, grab on and board. I repeated this twice more for the other Kerbals and used the last of my liquid fuel for a quick retroburn.

I wanted to come down at the Kerbal Space Center, and after jettisoning my orbital stage, was using RCS thrusters to pick my landing spot. When it looked like I’d miss the KSC and land in the water, I panicked and made sure I’d hit land on the previous continent, because I wanted a screen shot of all the Kerbals alive, and on the land.

I was ready to give up and rescue these guys later, but I couldn’t stop thinking about them up in orbit, confident they weren’t forgotten. It took me three real life nights, and 26 game days, to rescue them.

But I’m happy.

Next mission: build a plane to go get them and bring them back to the Kerbal Space Center.

Kerbal Space Program: Lost in Space

Moon shot

It’s a tense day for the Kerbal Space Program. Three intrepid explorers have been strapped into the Super Booster 3, charitably described in the Kerb press as a “flying bomb”.

In actuality, there’s an excellent chance it will explode right on the launch pad, like the regular kind of bomb.

That’s all in the past, though. The mess has been cleared away. Again. The space program has nearly run out of Kerbonauts, though — these are the last three. It is more important than ever, that they not die.

Right away, anyway.

Second stage!

Launch went surprisingly well. Eight solid rocket boosters paired with four mighty liquid fuel engines pushed the bomb spacecraft off the pad and into the clear skies. Twenty five seconds later, the SRBs dropped away while the liquid fuel engines continued. Above the atmosphere, the liquid fuel engines gasped the last of their fuel and were dropped.

Approaching Mun

The last stage took over. Previous models of the spacecraft had this last stage boosting from the start along with all the other engines, but this one saves the last engine for breaking out of orbit and landing on the moon.

You don’t just _fly_ places in Kerbal Space Program. You adjust the orbit so that it intersects the orbit of your destination at the same tangent. You don’t land on Kerbin. You choose a ground-intersecting orbit.

I fired the rockets and used the (M)ap display to help select an orbit that would intersect Mun at about the right altitude to grab the spacecraft and give me a base to circularize the orbit and make a controlled descent onto the moon.

Goodnight, Moon

Unfortunately, the space craft was moving too fast to be captured. Instead of going into orbit around Mun, the moon’s gravity swung the craft into orbit around the sun.

Kepler’s Dilemma

It’s been a very long time since we learned about Kepler’s Laws in high school, but I do remember that inner orbits are faster than outer orbits. This also means that if I can make the orbits match up, then at that particular point, if the tangents at that point are the same, the spacecraft and Kerbin will be moving at the _same orbital velocity_ — and the Kerbals will be saved.

The Kerbonauts have been sitting in their craft for game-years right now, waiting for the one moment when their planet and the spacecraft’s orbits are close enough to use the last of the spacecraft’s fuel to slow sufficiently to be recaptured by Kerbin and come to a final, safe landing.

It’s a game, and the aliens are cute, and if you buy the full version of the game (I am playing the free demo), you’ll have many opportunities to build more capable ships and explore more places and have a little more in-game help with the orbital mechanics.

This game works with the real physics. It IS rocket science. But it’s FUN rocket science! Plus, you get to fly spacecraft that you design, and how much fun is that?