Introducing: my favorite game

I’ve played many games in my life but none has been so entertaining and engaging as Kerbal Space Program, not even the Microsoft Flight Simulator! What is Kerbal Space Program (or KSP, in short) about? It is a fairly realistic simulation of, you guessed it, implementing a space program. You put together your own rockets, a bit like lego’s, and then you pilot them to the stars… or not. This fan video gives a pretty good idea what KSP is all about:

Building a rocket, once you’ve figured out how the editor works, is easy. Or I should say, the process of building a rocket is easy. Building one that actually is able to bring a Kerbal to space—and back!—is a different story. Kerbals, by the way, are the little green men that populate the KSP world. Although all rocket parts are modelled to, or inspired by, Earth technology, the whole game takes place in a different “universe” with different characters and planets. The main reason for that is playability; playing the game in a life-sized solar system would simply take too long. On the other hand, transit from Kerbin (the home planet and the equivalent of Earth) and its nearest moon, Mun, takes about three hours. That means that time acceleration is still welcome, but at least it’s not needed to the extend it would be in a “real” solar system.

KSP Size comparison

How realistic is KSP? There are two answers to that. I like playing it, so I tend to go for “fairly realistic” but haters can just as easily say “there’s a good amount of shortcomings.” I think that a good way to describe it is that it is “realistic in character,” which is kinda funny for a game based on little green men in outer space! What I mean by that it follows most of the laws of physics, but that there are some departures from that, for various reasons. The developers do emphasize that gameplay, not realism, is their prime motivator for the decisions they make.

  1. One of the most glaring shortcomings is atmospheric modeling. Aerodynamics are completely absent in the game, and as a crutch air resistance is based on mass, not on shape and size (and placement). The result is that placing a nosecone on a rocket or a booster actually increases resistance instead of reducing it. The reason this hasn’t been fixed yet is because that crutch works pretty well for the few minutes a craft spends in the atmosphere
  2. In line with this is atmospheric re-entry. The re-entry effects look beautiful but are purely for show. Your ship won’t actually heat up, it will not burn up if the wrong side is exposed (in fact there is no “right” side since there are no heat shields), and the plasma heat effects are depending on altitude, not speed.
  3. Movement of ships is decided by predetermined paths called “Keplerian Patched Conics” and assumes a single source of gravity, be it a moon, planet, or sun you’re circling. When you are in the “sphere of influence” of, say, Minmus, one of the moons of Kerbin, it is only Minmus gravity you’re dealing with, not Kerbin or even Kerbol (the sun) gravity. That may seem like a big departure from Newtonian physics (usually referred to as “n-body physics” because it involves any number of planetary bodies (“n”), not just one) but it has a couple of huge advantages for modelling the game, and although historically it predates the way Newton defined the universe that doesn’t mean it’s bad. I recall somebody from NASA saying “we use Keplerian patched conics alls the time where we can get away with it. They are numerically stable and calculate much faster,” so KSP is in good company.

And there’s a whole list of little things around ship construction, life support, etc. But on the whole, KSP does a remarkable job in being reasonably life-like for most of the time, and while some whiners my complain over the lack of lagrange points or decaying orbits, for most players things work out just fine (the fact that your ship doesn’t wander off because the stars literally—well planets, actually—align has more positive than negative aspects).

Jebediah Kerman on Minmus

You do learn quickly a lot of the finer nuances of spaceflight and rocket design. For instance, efficiency is far less a consideration when travelling through the lower layers of the atmosphere, brute power is; the quicker you leave the soup behind you the better. Or that meeting up with another ship is rarely ever “point your ship towards the other and burn,” but is instead about matching orbits which is mostly a waiting game. There’s a reason the game is hugely popular at NASA (especially the Jet Propulsion Laboratory) and that a special educational version is on its way, as many physics teachers have discovered that it’s a great way to let highschoolers discover physics by themselves, as opposed from a book.

Give it a try, the trial version is limited but free, and the full version is not that expensive!

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