“Kerbal Space Program”, a recently released computer game, is something in a league of its own. It puts you in the shoes of an engineer designing and constructing rockets, satellites, rovers, landers, capsules, space stations, and an array of other vehicles and crafts for the imaginary “Kerbal space program”. It also allows you to serve as the pilot of these crafts, letting you travel and explore the deeply detailed and complex “Kerbal” solar system. What makes this game so fantastic is the level of complexity, and also the simplicity, involved in it. The physics of space, and all of the complex gravitational maneuvers required to land a probe on another planet from ours, are fully simulated and represented. Yet you don’t need to be an astrophysicist to play this game to its fullest (though it wouldn’t hurt to be one, either!). There are many shortcuts and assistants which the game provides to allow someone without even the slightest grasp of astrophysics and rocketry procedures (myself included) to quickly jump into the game, build some rockets, slap on some probes, and begin exploring the universe.
I’ve been playing this game a lot recently, and it continues to blow me away. I want to share my experience in this game, and allow others to see the incredible things it allows you to do, by detailing a mission from start to finish. I’ll begin by building my rocket, guide you through the entire rocket building process, take you along on my journey to my destination, demonstrate the complexities of space travel and how the game represents them and aids you along, and we’ll finally end our journey together when my probe completes its mission. Let’s begin!
Welcome to the rocket assembly plant. This is where all the action before the mission takes place. It’s here where you pick and choose parts to build your rocket, your probe, your space station, whatever you want. For our mission, I want to land a probe on the moon. The ‘Curiosity’ rover’s landing on Mars this summer has given me some inspiration, and I want to replicate that amazing accomplishment in this game of mine. While some people playing this game actually have designed and flown rovers and probes which function and look like Curiosity, the complexity of that rover is a bit too much for me at the current moment. We’re going to have to settle for something a little more simple.
(Click on images for full size)
How about this? I’ve put together a nice little landing probe. Attached are some solar panels, to provide it with a source of energy for when its deep in its journey and when it lands on the moon, some instruments and scientific gizmos to conduct research and take measurements, some light fixtures to illuminate our landing zone, some landing legs to provide us with a stable landing platform, and finally a nice little rocket and some fuel tanks to slow us on our final descent.
This lander will do a great job landing on the moon (I hope), but it won’t be able to get us there. For that we need to start attaching some rockets. I’m going to add to this probe a decoupler, which when activated will detach the probe from the parts below it, and then add a fuel tank and a rocket engine. Also included in the parts I’m throwing on the rocket are some RCS thrusters, which will allow me to make minute adjustments to my craft’s facing and direction while in space, and a SAS piece, which should provide my rocket with some stability while lifting off and prevent gyrations and other aerodynamic ‘wobbles’ which could ruin my liftoff. This stage should hopefully be powerful enough to transfer me from an orbit around our home planet into an orbit around the moon.This stage still isn’t enough to get us off the ground and into space. For that we’re going to need to pull out the big rockets. I’m attaching a major fuel tank to our smaller stage and the largest engine available to that fuel tank. I’m then attaching two other tanks and engines alongside the side of this fuel tank to provide us with even more thrust and fuel for liftoff. These extra tanks are attached with a decoupler, which will detach them from my rocket when they run out of fuel. To get an idea of what this will do, think about the Space Shuttle and its rocket boosters and how they detach after burning out. Something like that should happen for these fuel tanks. For good measure I’m also going to throw on some canards, which should hopefully provide us with some aerodynamic stability and lift while we’re on our way up into space. I reinforce all of the rocket with some metal rods, which should keep our rocket together in one piece, and we’re ready to go!
This is where it all happens. We’re sitting on the launch pad, waiting to lift off. On the left side of the screen is the information about my stages. Each of the separate stages are shown in a separate box, and each require separate activation to turn on. So, for example, I have to activate my two side engines first, followed by my central engine, and then, once they’re done burning, I need to activate the decouplers. The staging system in this game is really quite simple but allows for complex rocket functionality (as we’ll find out soon enough). The bottom of the screen shows my navigation ball; this provides me with all the navigation information I need to take my rocket and navigate it anywhere in the solar system. It’s quite intimidating at first, but once you get used to it it’s very straight-forward and incredibly useful. Finally, at the top of the screen is my altimeter, a gauge representing my vertical lift (which is useful in telling me if I’m going against the pull of gravity or being drug down) and a scale which shows how much atmosphere I’m still in (atmosphere slows a rocket considerably, so its useful to know when you’re still in or out of it).
A few seconds later I activate my main, center rocket. By now we’re steadily gaining speed and lifting into the air. My engines are beginning to overheat, but that’s alright; so long as they aren’t pushed to the max, they won’t suffer any damage or lessened performance. I try to keep my rocket pointed straight up by following the alignment of my navigation ball.
Once we’ve hit a considerable altitude (for this rocket, about 30,000 meters), I begin to roll my rocket towards the east by navigating down the navigation ball towards the 90 degree marker. By doing this, I’ll be setting up an orbit which follows the rotation of the planet. This allows me to gain some extra momentum when trying to transfer to the moon. It’s complicated astrophysics stuff, but even a beginner like me, with enough experience, can pick up on some of these rocketry tricks. turn the engines off. My engines are almost out of fuel, so I turn them off. We’re still gaining altitude, as we’re coasting towards the highest point of our orbit, the apoapsis. It is at the apoapsis where I will throttle my engines back up and try to circularize my orbit; the apoapsis is the point where the least energy and fuel is expended in return for the greatest adjustment to my orbit. Welcome to the map screen. Once you’re off the ground, this is where you spend much of your time. The line in blue is my current path; you can see that it will crash back into the ocean. I need to circularize my orbit, and by doing so actually create an orbit around the planet, by thrusting at my apoapsis. In order to do this, I create a maneuver at the apoapsis. The new orbit produced by this maneuver comes up in orange around my planet, and next to my navigation ball I’m given information about how far away I am from my maneuver point, where I will need to point my rocket during my maneuver, and how long I’ll need to burn my engines in order to accomplish my new orbit. It’s very intuitive, and even though I’m simply making a circular orbit right now using this process, I’m using the same tool which I would use to plan interplanetary transfers, land on other planets, and other very complex things.
After coasting for about a minute (which is how long it takes for my rocket to reach apoapsis), I align myself along the guideline presented to me on my navigation ball and begin to burn my engine for 20 seconds, the amount of time I’m told I need to burn in order to accomplish my new orbit. As I burn, the yellow bar next to my navigation ball begins to decline; this bar tells me how much more thrust I need to expend to achieve my new orbit.
Halfway through my burn, my two side engines run out of fuel. I detach them from my rocket, leaving me with just my center engine. The discarded engine and fuel tanks will fall back to our planet, where they will be collected by the Kerbal Space Agency for reuse. To compensate for the decreased thrust I’m now putting out, I’m told I need to burn for a little bit longer.
A little bit longer into my burn, and my main engine runs out of fuel. I was hoping to be able to use it during my entire circularization burn, but I have enough fuel left in my upper stage to complete the burn. I detach the main fuel tank, which falls back to our planet, and continue my burn. Because my upper stage puts out much less thrust than the engines on the earlier stage, I need to burn for much longer.
I do this by setting up another maneuver on my orbit (I told you this tool was incredibly handy!) This new maneuver will require me to burn my engines for 20 seconds once I’ve gone slightly passed my current orbit’s apoapsis. By doing this, as the new orange orbit line demonstrates, I’ll be in a path which will intersect the gravity of the moon. Once I’m in the moon’s gravity well, I’ll plan another maneuver to circularize my orbit around the moon and then bring my lander down to its surface.
As I maneuver my rocket into the position I need to be once I begin my burn by using my RCS thrusters, I also deploy my solar panels. This game simulates the electrical components of my spacecraft with much detail, meaning that I need to be sure my spacecraft gets energy or else it will power off in mid-flight and be unusable (which has happened to me before, and is quite annoying).
A dozen or so minutes go by, and we approach the point where we need to conduct our next burn. I retract the solar panels, because I don’t want them to get damaged during my burn, and because they’ve provided my batteries with enough energy stores to last us for a while. I’ll reactivate them once we’re on our way to the moon. The burn lasts 20 some seconds, and once it is complete we are on a trajectory which will bring us to the moon!
This game is also quite beautiful, and presents many opportunities for some fantastic photographs. Here our lander is on route to the moon, which stands small in the distance but is getting ever closer.
Three days go past as we’re in transit to the moon until we hit the moon’s gravity well. On the map, my current trajectory shows that I’ll smash head first into the moon! I’ve come in too directly, and the gravity of the moon will pull me straight into it. I thus create a maneuver which will bring me into an elliptical orbit around the moon before that happens; I should have enough fuel to be able to complete this burn and still bring us down for a nice landing.
I complete my burn, which takes only a few seconds, and am placed into an orbit around the moon which won’t result in my smashing straight into it. Meanwhile, I create a second maneuver which will bring me down onto the planet in the point of my choice; in this case, I want to land somewhere where my probe will be able to send messages to the home planet, and thus will be in sight of it. Of note is that my current orbit brings me as close as 5,000 meters to the moon at its periapsis, its lowest point. I’ll be hardly skimming its surface! This will allow me to take some fantastic pictures of the moon’s surface as I fly near; the scientists back home will be very pleased.Passing over the moon at our orbit’s lowest point as our planet slips underneath the horizon.
As I approach the point where I need to conduct my burn to get into a landing trajectory, I prepare my lander for landing. I extend the landing legs and retract my solar panels; they’ll be extended again once I land. I also extend my communications relays to send back information about my current journey to mission control. We’re now in landing mode. No longer can I rely upon the game providing me tools to calculate my orbital adjustments. I must do this all on my own. In order to slow my descent, I begin to burn along a guideline provided to me on my navigation ball which tells me where I must burn to decrease my orbit. I make sure that I burn enough to slow myself but not too much so that I quickly run out of fuel. This continues for at least a good minute. Coming down onto the surface is a slow and difficult task which requires careful maneuvering. One slip up, or if I run out of fuel too high, and my lander will become an experiment in impacting the moon’s surface at high speeds. At about 4,000 meters above the moon’s surface, the second stage of my spacecraft runs out of fuel. I detach it from my craft and it drops quickly to the surface of the moon; iIt has served me well. I was expecting it to run out of fuel as I slowed my descent, because one way or another I needed to detach it from my lander before the actual touchdown occurred. I now activate the rocket on my lander; it will do the rest of the work from here. The lander doesn’t have much fuel or much thrust, but in the vacuum of space the little thrust it does provide will be more than capable of doing the job. I slowly bring down my lander to the moon’s surface.
It requires careful maneuvering and a number of adjustments to the direction I’m pointed and the amount of thrust I’m producing, but after 2 minutes or so of landing, I touch down gently on the moon’s surface.