30 November 2013
Kerbal Space Program is a game that simulates spaceflight. The game has no goal, no score, no time limits. You are in charge of a space program with infinite resources, unlimited astronauts, and no safety regulations. Your only adversaries are the laws of physics.
This walkthough demonstrates a moon landing. The rocket I designed has six stages, with propellant cross-pumping between the central cores, and drop tanks on the upper stage.
The rocket burns most of its fuel just to reach low Earth orbit. All that makes it to orbit is the fully fueled lunar lander, and one empty core stage. To reach the moon, we need that core stage fully fueled.
The next step is to launch a second rocket with the goal of refueling the first.
Rendezvous and docking is time consuming as one attempts to match the two crafts' orbits and phases.
Finally one can use RCS thrusters to fine-tune the approach and perform a hard dock.
One of the beautiful details in the game is that as propellant is pumped from the refueling rocket to the lander's core, the combined ship slowly translates to preserve its centre of mass.
With the lander fully loaded, the pilot of the refueling rocket performs a deorbit burn and lands in his one-man capsule.
Meanwhile, the lander performs a burn to enter a Hohmann transfer orbit.
After coasting up towards the Moon, a retro burn is needed to be captured into lunar orbit.
Descent is nerve-wracking. The terrain is covered in craters with steep inclines. I've crash-landed here more times than I'd care to admit.
Touchdown! The astronaut can descend the ladder, plant a flag, and collect a soil sample.
Just a few kilometers away from the landing is the wreckage of a previous landing attempt. The astronaut survived and has been camping out. Fortunately life support is free in this game.
A short walk across the surface (augmented by jet pack) brought the survivors of two separate crashes to the lander.
With all three astronauts together, they took off and headed back home.
The remaining fuel was used to propulsively make the reentry a bit gentler. I'm not sure that this is a great idea in the real world, but it seems to work in Kerbal.
And finally three good chutes, for a gentle touchdown as the capsule meets its shadow.
This gives a flavour of the game. Other potential goals are construction of space stations, missions to other planets, rovers, bases, space planes, satellites, and scientific research. There is also the problem of debris, as each mission adds to the clutter in orbit (here is one way to remove debris). And finally, the game is developer friendly with an active mod community.
I highly recommend Kerbal Space Program for both fun and education.