Trans-Lunar: Kerbal Space Program

Cuter than the real thing.
Watching the final shuttle launch last week had me thinking about how I would have to look for a game about managing a space program, so that I could post relevantly here on RPS. I never got around to looking for one, but it turned up in my inbox from a dozen sources anyway. The game is called Kerbal Space Program and it’s about building rockets (in a Spore-like rocket-building editor) and trying to get aliens called “Kerbals” into space. The game comes with a full SDK and even though it’s only been out for a few weeks, people are already modding in new bits and pieces to play with. Right now the game features a host of rocket-building systems, along with a 600km planet to try and get into orbit from. Try being the significant part of that sentence: because failure is part of the fun. Long term, the team are planning moon landings, bases on other worlds, and a detailed astronaut recruitment and training management subgame. It’s certainly promising stuff.

You can download it, and also watch amusing illustrative videos below.


  1. kutkh says:

    Man, I love these historical sims.

  2. Peter Radiator Full Pig says:

    Excellent looking stuff. Cant believe it was never done before, seens like such an obvous idea. The sort you wish you had come up with yourself.

    • Moni says:

      Yeah, it’s not like it’s rocket science.

      (Isn’t rocket science actually just trigonometry, therefore, super easy?)

    • CMaster says:

      A lot of it is just simple F=ma stuff. Although if you actually want to work out accelerations of the rocket as fuel decreases, or the path it will take then you need to use some calculus.

    • Harlander says:

      It’s the rocket engineering that’s the hard bit

  3. Inigo says:

    Having watched the videos, I can only say JESUS CHRIST MY FUCKING EARS

  4. xfxian says:

    It’s really nice for this early development stage. I’m really looking forward for new releases.

    In the meantime, near-perfect physics without the building part: link to

  5. ArcaneSaint says:

    So, does this mean that we’ll soon see pictures of genital-shaped Space Shuttles all over the internet?

    • Felixader says:

      What do you jmean soon?

      Isn’t the form of a rocket already kinda phallic?

  6. Srekel says:

    Oh, reminds me of Bridge Builder/Pontifex but with rockets :)

  7. MuscleHorse says:

    Initially misread that as Kersal building project.

    link to

    Don’t think they’d get very far.

  8. groovychainsaw says:

    Anyone else remember Buzz Aldrin’s race into Space? still my favourite space race game, and one I play from time to time. It was very hard, mind (turns out the space race is difficult to win at!). There’s a couple of freeware remakes around somewhere….

    On topic, this looks pretty good fun too!

  9. Jams O'Donnell says:

    People were chatting about this in the RPS Steam chat yesterday, and it was sounding awfully fun. I love the faces of your astronauts after you launch the rocket.

  10. Moni says:

    Just having a quick play around with it, it’s really good, it’s solidly made, funny, and the tutorial isn’t completely useless.
    The only problem is, there doesn’t seem to be a frame rate limit, so my GPU goes into jet engine mode.

    edit: Some screenshots of my first launch:

    link to – sitting on the launch pad.
    link to – igniting the rockets.

  11. Eraysor says:

    I am loving this game already. After half an hour of work I had made it into space. My maximum height is 175km so far.

    • Moni says:

      I’m really struggling, I can’t get the damn thing to fly straight.

    • Bilbo says:

      My main problem early on was flying by the screen and not the instruments. If you fly by the instruments instead, it makes keeping level a bit more logical

    • CMaster says:

      SAS is very helpful too.

  12. ShineDog says:

    I love that Jeb is cool as shit in most situations. If Jeb looks worried, you know you’ve really screwed up.

  13. neolith says:

    Ooooh, a rocket surgery sim – can’t wait to get home and give it a try! :)

  14. talon03 says:

    Thanks to you, RPS, I have accidentally signed off two hours of my life. EXTREMELY fun little sim. Can’t wat to see the improvements in the future, as there seems to be a lot of features waiting to be added.

  15. Rii says:

    Love the concept, and it looks great so far. I look forward to checking it out once it’s had a few more months in the shop.

  16. Bilbo says:

    Fallen in love with this. How do give all my money?
    Max altitude so far: 183785, in the Odysseus II. Breaking free of the planet’s gravity for the first time was an awesome feeling. Getting my Kerbals back alive was the icing on the cake.

    *Edit* Just broke 300k. I’m addicted to a demo! Topped out at 310k and started falling. Seems re-entry isn’t a massive problem at this stage in development :)

    *Edit* Just broke 1000k. World looks very small from up here. Might work on having a third-stage craft that can actually steer and stuff, rather than just a rocket

    • skinlo says:

      :o Mines likes 12000. How do you keep it stable?

    • Bilbo says:

      Keep your ship designs symmetrical, hold F the entire time, and make careful adjustments with your steering

    • ShineDog says:

      No need to hold F the entire time, just hit T to toggle the stabiliser.

    • Bilbo says:

      That’s dead handy, thanks

    • Snidesworth says:

      link to
      link to
      Have I won yet?

      Thanks for that tip about T, by the way. I’ve been holding F like a moron for the past 10 minutes.

    • Bilbo says:

      Yeah, that’s pretty fast. I think my current craft is probably going to top out at about 1500. What sort of thing are you using? I’ve found a stack of fuel tanks with an engine at the bottom, with a ring of solid fuel boosters close to the nose cone as a first-stage to be the most stable.

      *edit* Got to 1500, still going at about 600m/s. Getting boring, to be honest. Will try and work on orbiting the planet safely next, I think – had about enough of this going up high really fast and then falling down stuff

      *edit* They started falling again at about 1800. Somewhat relieved – the thought of my plucky crew being lost in space was putting a downer on my afternoon

    • Crimsoneer says:

      3700K away, 4000 m/s, and decelerating very, very slowly!
      link to

      Built with an entirely terrible ship which had a bunch of boosters to get me off the launchpad, followed by 3 or so 4 fuelcontainer rockets.

    • PFlute says:

      I…I don’t think the game likes my pyramid-of-boosters very much.
      link to

    • randomnine says:

      Orbiting is not difficult but it does require some care – and a final stage with a liquid fuel booster, if you want a circular orbit. Here’s my rocket’s final stage passing over its launch pad in a stable 150km orbit.

      Near Earth, a 150km orbit would be stupid – atmospheric drag would claw down anything that close. But this isn’t Earth.

      Here is some FACT SCIENCE derived from a few stable orbits:

      – The Kerbal planet has a radius of around 590km, so is roughly 1/11th as wide as Earth

      – It has a mass of about 5.2*10^22kg, so around 1/114th Earth’s mass

      Because it’s so much smaller, reaching space is much easier! Escape velocity from Earth’s surface is 11.2km/s – on the Kerbal planet, it’s 3.4km/s. Escape velocity from an altitude of 100km is 3.2km/s. If you’re going faster than this when you hit this altitude, you will never come back down.

      If you want to get into orbit, you can derive the correct orbital velocities given the numbers above… but here are a few (approximate) orbit velocities:

      at 100km: 2246m/s
      at 200km: 2100m/s
      at 2000km: 1161m/s
      at 20000km: 412m/s
      at 385000km (equal to Moon orbit): 95m/s

      Process for orbital insertion:

      1. Launch straight up. You need to escape atmospheric drag as quickly as possible.
      2. Once you reach at least 40km or so altitude, accelerate horizontally to around 2500m/s for a low orbit or around 3000m/s for an extremely high one.
      3. Climb slowly to required orbital altitude. Once there, thrust downwards until altitude stabilises.
      4. Watch altitude. If you are accelerating downwards, accelerate forwards a few m/s and then restabilise altitude. If you are accelerating upwards, accelerate backwards a few m/s and then restabilise altitude. Repeat until altitude is stable.
      5. If you wish to deorbit for landing, accelerate backwards, not downwards. Accelerating downwards will speed you up and slingshot you into a higher, more elliptical orbit.

    • Persona Jet Rev says:

      Thanks for the explanation, randomnine.

      I achieved my 1500km height yesterday, but that was pretty boring. With more than enough fuel left when hitting the 300km, I should be able to reach escape velocity.

  17. CMaster says:

    Made 500k just now. They’re on the way back down as we speak. Attempt to curve the trajectory near the end in an attempt to reach orbit, too little too late though I think, looks pretty ballistic. Really unfinished at the moment though, and the post-flight summaries often seem to talk nonsense.(Last one had “stage 0 separation confirmed” at about a minute in, even though it didn’t happen until T+6 or so).

  18. Howling Techie says:

    just like to point out that version 0.8.1 will have a symmetry feature, a sound normaliser, reduced structure wobble as well as more:

    He is also planning to improve the staging feature, a redone terrain engine, enchanced UI, timeskip, automated control and loads more.

    • Harlander says:


    • LionsPhil says:

      Symmetry mode is going to be a killer; right now trying to make something that doesn’t shake itself apart due to tiny misalignments is a pain.
      Also, see the uploader comments: “fuel can now flow through Strut parts”, and someone has argued for a Shuttle-style ability for jettisonable fuel tanks without losing the engine too.

    • Persona Jet Rev says:

      0.8.1 (and 0.8.2 for some bugfixes) is out. It includes modules insertion and symmetry, and should feature sound normalization.

  19. LionsPhil says:

    It simulates terminal velocity, and only in atmosphere!
    After every physics engine being set in a vaccum, I am most pleased. Atmospheric braking does worry the little pilots, though. :D

  20. Muzman says:

    This is just a plot by Epic to keep John Carmack distracted from designing game engines isn’t it.

  21. Redcoat-Mic says:

    What on Earth is the screenshot button?

    • dsi1 says:

      F1, or you can run it through Steam and use your Steam Screenshot button.

  22. mr_notorious says:

    Haha, this game is awesome.

  23. BoZo says:

    Aw crap, I seem to have gotten them stuck in an elliptic orbit…
    How do I get them home!? :(

    link to