Kerbal Space Program is a game about a green humanoid species known as the Kerbals, as they start a space program. Superficially similar to Orbiter, the difference between the two has been likened to the difference between making to-scale miniatures for architectural design and playing with LEGO bricks with rocket fuel in them, which you then hurl with glee at your sister.In its current state (version 0.24) the game offers three game modes to suit your style of play. The first is little more than a sandbox. You're set loose upon a space center complete with a vehicle assembly building and a launch pad, a bin full of rocket parts, ground personnel composed entirely of yes-men who build and wheel onto the launch pad anything you design no matter how crazy it is, and some astronauts to crew your creations. The second version is Science, in which you have to conduct experiments in order to unlock various piece parts, as you start off with just the very basics. The third mode is full blown Career mode, and you have to juggle a budget, job offers, your Kerbalnauts and conduct Science similar to the Science mode (which used to be the old Career mode, prior to 0.24). Essentially, you have to manage the entire Space Program. The number of parts has risen dramatically in recent releases, and the community is already cranking out fanmade addons at an impressive pace on top of that.Its official website and download location is here, and a trailer for the game can be found here. Starting with 0.19, it's also available on Steam.
Aerith and Bob: Somewhat odd example - all the Kerbonauts have names that sound fairly Middle American, but anyone who is not an orange suit has a name randomly generated from a list of prefixes and suffixes. So alongside Jeb, Bill, and Bob may sit Melzer, Bardrin, or Billy-Bobfred.
Although there are some characters who are named after historic space personages ("Buzz", for instance) or famous Kerbal Space Program Let's Players.
After Action Report: Many players like to share accounts of their most recent or most memorable accomplishments. The Mission Reports section of the official forums is set up explicitly for this. People also like to assemble collections of screenshots into captioned Imgur albums and share them as brief Machinomics.
Alien Sea: Eve, whose oceans are purple and at least partly made out of rocket fuel.note According to tentative development plans, when resource extraction was going to be implemented, players would have been able to gather propellium from Eve's oceans in addition to water. Announcements made at KerbalKon 2013, however, indicate that plans for harvesting and refining resources on other planets have been temporarily shelved at the very least.
Alien Sky: Eve again, with a thick, heavy purple sky. Laythe also counts; from some angles it looks a lot like you could be on Kerbin until you turn around and see a massive gas giant hanging in the sky about where the sun ought to be.
Alleged Car: Rovers are a bit... unstable at the moment, sometimes shaking themselves apart or exploding with little reason. Of course, when rockets are rarely of much higher quality...
Artistic License - Physics: The game is generally pretty good about using real physics, but that makes the few places where it goes off of it stick out more. Mainly, this is due to engine limitations,note (specifically the Unity3D engine which means some things are inaccessible to even the programmers) some of which the developers hope to improve in future updates. One common example is the way the game models air resistance, which is vastly simplified from a realistic model.note (in current Kerbal physics, everything adds drag in direct proportion to its mass, regardless of shape, which means that some structural surfaces which would normally be added to substantially reduce drag at a small increase in mass actually increase drag)
Artistic License - Nuclear Physics: The LV-N Atomic Rocket Engine, a nuclear fission engine with poor thrust but extremely high efficiency in a vacuum, runs off of the same liquid fuel / oxidizer mix as any other liquid fuel engine. This is acknowledged in a comment in the item's config file, saying that it would be too much trouble to make two separate kinds of fuel sources just to support this one engine at the present time, and the engine was given low thrust for gameplay reasons so as to stop it from being the best engine for every situation.
Actually, that's a real type of rocket design, called a "hybrid nuclear chemical rocket".
Which raises the question of why the nuclear engine doesn't have it's own unique fuel, when the ion engine does (it runs off Xenon gas and lots of electricity).
Art-Style Dissonance: Don't let the cartoonish proportions of the kerbonauts or their rockets fool you; the game is deceptively difficult if you don't already know a little bit about how actual rocketry works.
Ascended Meme: The new loading screen roll references a few that are popular on the forums, such as "Adding K to Every Word."
Asteroid Thicket: Averted. While there are asteroids added in the aptly-titled Asteroid Redirect Mission update, they are few and far between, and players have to go out of their way to detect them in the first place, let alone rendezvous with one, conduct experiments, and even change its course.
Awesome, but Impractical: There's nothing preventing you from making a rocket far larger than one you really need to complete the mission.
The ion engine. The most fuel efficient engine in the game by far, but it's expensive, uses a lot of electricity, and has a very low thrust output (despite still being several times more powerful than real-life ion engines, especially due to a recent update that upped the thrust level appreciably). As a result, the burn time needed to get anywhere interesting can take hours, and you can only accelerate time up to 4x when engines are on.
Badass: Jebediah Kerman, along with many other randomly generated Kerbals if they have a hidden "BadS" trait set to true. They always smile no matter what's happening and even if something explodes, they get worried for a few seconds before resuming their smiling. If he looks freaked out, you have done something horribly wrong.
Base on Wheels: At its most basic level, you could just slap some large rover wheels onto a Hitchhiker Storage Container and call that a base. Anything more elaborate depends on your imagination and engineering and piloting skills.
Beautiful Void: Only one planet in the whole system has (debatably) intelligent life although there is evidence for it on others, and even that planet is mostly empty aside from your Space Center and a few other locations of note (as of 0.24). Some particularly enterprising modders are working to make the place feel more lived-in, literally.
The Big Board: Both the Tracking Station and the in-flight map view allow you to see statistics on the various bodies in the Kerbol system and monitor the progress of your active flights.
Bilingual Bonus: The Kerbal language is Spanish, played backwards and sped up.
Camera Perspective Switch: If your rocket has a manned cockpit, you can switch to an Intra Vehicular Activity camera and experience the ride from the inside.
Captain Crash: Building your own vehicles is one thing, landing them is another. Mun Landings, for instance, often end in the vehicle tipping over and falling to pieces, leaving the Kerbonauts stranded until help arrives (or backup help when the help befalls the same fate).
Chest of Medals: A series of service ribbons with a host of devices are available for use in signature lines on the KSP forums, indicating what planets you've been to and what you've done there. There is even a mod that tracks the careers of your Kerbals in-game, updating their ribbon and medal counts based off of where they've gone and any activities they have performed.
Colony Drop: The introduction of the Asteroid Redirect Mission allows the player to attach ships to asteroids and redirect them to impact other celestial bodies. There is no particular reason to smash an asteroid at high velocity into a planet though, except as a Self-Imposed Challenge. However, managing to safely land an asteroid on another celestial surface can give another opportunity for additional scientific data.
Construction Is Awesome: The game's primary appeal is that it lets you design, build, and fly your own spacecraft, space stations, and surface bases, including the possibility of assembling them part by part in orbit or on another planet's surface. See also Design It Yourself Equipment.
Context-Sensitive Button : Docking Mode allows you to use the normal rotation keys for RCS translation maneuvers, although it isn't strictly necessary as you can also translate from the main keyboard configuration using different keys. You can also define custom action groups when designing a vehicle, so that you can, for instance, press one key to extend all of your solar panels at once instead of having to do it one-by-one.
Convection Schmonvection: Averted while in the atmosphere. "Clustered" engines can overheat more quickly in thicker atmosphere due to better convection, while in a vacuum they run "cooler" due to most of the heat being thrust away from the craft with no air to transfer it back.
Conveniently Close Planet: Averted, even taking into account the Space Compression. Even getting to the Mun is a challenge for the newest of new players, and traveling to other planets requires quite a bit of planning and forethought — even more so if you plan on going home.
Critical Existence Failure: Your Flight Log may tell you that parts take damage from engine exhaust, but this damage seems to have no effect on their performance at all until they're destroyed outright.
Death Is a Slap on the Wrist: Selectively averted with the 0.21 update, which allows you to enable permanent deaths for your pilots. You have to hire all of your astronauts, and when they're dead, they're gone for good. Previous versions of the game did play the trope straight, however, and you still can if you leave the option disabled (which is the default).
Design It Yourself Equipment: The full game comes with a small selection of prebuilt designs, but if you want to do anything really impressive, you'll have to design and build your own rockets, probes, satellites, etc.
The Dev Team Thinks of Everything: It's supposedly impossible to land on the gas giant, Jool, but they do have responses to performing science experiments on the "surface" such as the EVA report.
The LV-N Atomic Rocket Engine is the largest and heaviest engine in its size category, has trouble with decouplers, and has one of the poorest thrust-to-weight ratios in the game. Its thrust is so poor that it is almost useless on any ascent stage, limiting it to final stages only, which because of the aforementioned weight and decoupling issues, takes a lot more effort to get into orbit than lighter engines - and good luck landing back on solid ground when the engines are twice as tall as any landing gear. However, if you can get them up there, they are the single most fuel-efficient reaction mass burning enginesnote (See Artistic License - Nuclear Physics earlier on this page for why this is an Acceptable Break from Reality) in the game. They are one of the most popular options for interplanetary vessels for this reason.
The First Contract (0.24) update makes this apply to reusable spaceplane designs. Their controls are difficult to master, but the relative cheapness of fuel compared to parts and the fact that they can be piloted back to and recovered at the Space Center for a complete refund on their parts value makes them highly cost-effective for transporting crew, experiments, and small probes into orbit.
Certain advanced maneuvers such as gravity assist or aerobraking can save a lot of fuel when done properly.
Diminishing Returns for Balance: The amount of scientific benefit you get from performing the same experiment multiple times in the same environment slowly decreases until you end up getting nothing out of it at all. This is supposed to encourage players to send craft to many different environments, both around Kerbin and elsewhere in the system. Recent updates have made this effect even more pronounced.
Disaster Dominoes: Any accident that doesn't involve your rocket crashing into the ground wholesale usually involves these, and even that is often only the last domino in a chain of design and piloting mistakes.
Drives Like Crazy: Several of the multi-ton cargo and utility vehicles in the Spaceplane Hangar are apparently driven by speed-obsessed maniacs, including at least one who loves to drift in circles around much larger vehicles and another who nearly causes a three-car pileup by trying to thread between two moving vehicles.
Earn Your Fun: Figuring out how to build a rocket that will actually achieve orbit, let alone go places, can be a challenge for new players. But this is a game that rewards persistence and a willingness to endure failure, and gives experienced players a universe of possibilities.
Easily Detachable Robot Parts: With clever use of docking ports and probe cores, you can create completely autonomous spacecraft from modular components that can operate independently of the main craft as well.
Easy Logistics: Individual craft have limited fuel and electricity, but (discounting monetary costs) that fuel is effectively in infinite supply for your space program as a whole.
Easter Egg: "Anomalies" scattered across the surface of Kerbin, Mun, and other bodies.
Edutainment Game: While the original game is not primarily designed as one, its creators support its use in the classroom as a teaching tool and have been working on a special edition called KerbalEdu specifically meant for classroom use. At least one teacher has incorporated it into his classes.
Ejection Seat: It's possible to create a (very clumsy) ejection seat for rovers with the use of miniature SRBs and a decoupler. With the NASA update, a real-life equivalent from the Apollo program is available for regular cockpits - the Escape Tower, a vectored SRB mounted on the top of the cockpit, which can be activated (in unison with a decoupler) in an emergency to lift the entire cockpit to safety.
Emergent Gameplay: Quite a few people find ways to have fun with the game without launching rockets into space at all, or by finding unusual uses for game parts. Geofley'sCove, a fully aquatic base on Laythe, is one of the less outlandish examples.
Another excellent example is The Wrong Brothers, in which a player goes through career mode using only the spaceplane hangar and runway, and never launches a single conventional rocket.
Enormous Engine: The obvious result of sticking 2-meter diameter engines on 1-meter diameter fuselages or fuel tanks. More particularly, this is true of any launch vehicle, which is simply an enormous engine to get your (relatively) tiny spacecraft or probe up into orbit. Said launch vehicle tends to discard pieces after they are spent on the way up, gradually shrinking the size of the "engine" until only smaller ones remain.
An Entrepreneur Is You: The 0.24 update introduces an economy system to Career Mode to provide funding and contracts for your space program.
Epic Fail: Half the fun of the game is watching your carefully crafted creations explode, go way off-course, or slam into Kerbin at hundreds of miles per hour.
Explosive Overclocking: Cramming too many engines too close to one another and firing them all at full throttle is guaranteed to make them overheat rapidly. Let them get too hot, and all those engines will explode spectacularly.
Explosion Propulsion: While this is arguably true of any liquid or solid fuel rocket (no Orion Drives in the unmodded game, yet) some players find creative uses for rocket exhaust:
One common design Fan Nicknamed the "Mass Relay" is created by attaching two powerful rockets facing opposite each other designed to go to full throttle immediately as a pair. Each rocket cancels the trust of the other, but any object placed in front of one of the nozzles will be launched away at high speed. This is often used as a feature of space stations to move small masses without needing to have their own propulsion.
Fearless Fool: A common fan interpretation of Jebediah Kerman's personality. The description of him on his Steam trading card supports this.
"Fearless? Brainless? Who can tell?"
Fictional Counterpart: Weird names and minor tweaks aside, KSP's set of planets is essentially the same as ours. Kerbin is the third planet from its star, followed by a small red planet, then a small rocky object (the counterpart to Ceres), then a huge gas planet with lots of moons, and so on. Saturn, Uranus, and Neptune equivalents are missing, but may be added in future updates.
Flanderization: According to the development staff, the attitude implied by, among other things, the use of the word "kerbal" as a synonym for "ridiculous and impractical" is a result of the fandom taking one aspect of the Kerbals' approach to rocket science and blowing it totally out of proportion. To quote this development blog post:
Bac9: Overall, I'm convinced the obsession with disasters and perception of Kerbals as worthless engineers only caring about explosions is destructive for the game. KSP deserves much more than being a glorified disaster simulator where rockets falling apart and crews being killed is the prime entertainment and the only expected result.
For Science!: Literally in career mode, where doing experiments, sending reports, and collecting samples in various environments both terrestrial and extra-terrestrial accumulate science points used to unlock the Tech Tree. Generally, the further out from Kerbin you go and/or more inaccessible the location (Eve, for instance), the higher the multiplier for doing science becomes, thus "For Science!" is a wholly rational justification for conducting missions.
Frictionless Reentry: Mostly averted. Friction does slow down things traveling through atmosphere, but it doesn't cause the other part about friction that real astronauts fear - heat - although its complete aversion is a planned feature. Reentry flames were implemented in 0.19, but as of 0.24 actual heating of the spacecraft is not included unless you install the Deadly Reentry mod. Naturally, installing such a mod immediately spikes the difficulty quite a bit...
Fun Size: Kerbal proportions are quite odd compared to those of humans. For one, their heads are ludicrously oversized.
A sandcastle on the Mun can sometimes be seen in the background.
The service trucks added in 0.21 to the VAB and SPH drive around, but you will occasionally see the trucks drifting.
Game-Breaking Bug: If you attach your engines directly to the large orange fuel tank, it has a nasty habit of causing said engines to overheat much faster than normal. Fortunately this can be fixed by adding a smaller fuel tank to the bottom and taping it up with struts, or by using two normal fuel tanks that are half the size together.
Trying to make a new jetpack design with the new external seats? Bye-bye, Kerbin!
When RCS thrusters were first added, they were programmed to have more thrust when they were closer to the ship's center of mass. Since there wasn't any cap on this, having an RCS thruster dead on the center of mass would give it infinite thrust, crashing the game.
Gameplay Automation: The "MechJeb" user-made addon adds an autopilot feature to the game. Since each autopilot program is a separate "module" (with one for docking, one for ascent, one for rendezvous, etc), it's the player's decision how much they want to automate their flight.
Guide Dang It: One of the game's few flaws is that (as of yet) there is little in-game documentation of how most things work. You'll have to learn either by a lot of trial and error, by reading up on and applying actual rocket science, or by watching tutorial videos on YouTube.
The Hard Hat: Kerbonaut helmets are apparently hard enough to survive impacts that would otherwise kill the wearer.
Hitbox Dissonance: In older versions of the game, a few of the buildings at the Kerbal Space Center had some wonky collision meshes, such as the SPH being about 10 meters taller than it actually appeared to be.
House Rules: Prior to implementation of a proper campaign mode, some users had created and shared their own systems for handling funds and tracking pilot stats as a Self-Imposed Challenge.
In-Universe Game Clock: "Internal Game Clock" variety. Time normally passes in real time and is recorded in Earth minutes, hours, days, and years (with, since 0.23.5, an option to switch to Kerbin days and years, where each day is 6 hours and each year is 426 days). Thankfully, as some missions could take a very, very long time in real-time, there are options for time acceleration. Each planet and moon has its own day-night cycle determined by its motion within the solar system, which is important when planning landings or using solar-powered probes.
Jet Pack: Every Kerbonaut has an EVA pack to prevent him from floating away from his vessel. It only works as a traditional jet pack on low gravity bodies, though on the smallest objects, it is possible to achieve orbit. it has 20x the fuel of a real life jetpack.
Lens Flare: You can see the effect whenever your camera is pointed towards the sun.
Loads and Loads of Loading: This will definitely happen if you have a low end computer, or if you have a 3,000-part ship being put on the pad.
Made of Explodium: Rockets have a habit of blowing up on occasion, usually during stack separation or when insecurely radial-mounted pieces "wobble". Justified by most of a rocket's volume being fuel containers which in turn hold most of the rocket's mass... mass that is itself a two-part combustive compound designed to explode preferably slowly and in a controlled manner. Pretty much Every Rocket Is A Pinto.
Every single part, regardless of function, will explode when it hits the ground with enough force.
Made of Iron: In contrast to the Made of Explodium rocket parts, Kerbonauts are incredibly durable. Besides never running out or air or needing food or water on multi-year space journeys, they can somehow survive crashing into the ground at up to 45 m/s (about 100 MPH) completely unharmed. Your ship's landing gear will snap off and/or explode at one-third that speed.
It's been speculated that it's in fact their helmets that are Made of Iron. Landing a Kerbal on their legs will generally kill them instantly, but if you flip them over and land them on their helmets, it's possible to survive.
The Many Deaths of You: Blowing up in liftoff, drifting into the void of space to starve or freeze to death, spinning madly on the launch pad, hurling yourself into the sun - there's no end to the creative ways these guys can perish.
Mohs Scale of Science Fiction Hardness: 5.5. While the game uses realistic Earth technology and Newtonian physics, it is also meant to be accessible to the average joe and used as a teaching tool, which softens it up a bit. Think of it as being able to fly really cool model rockets that can land on other planets.
Nerves of Steel: Jebediah Kerman almost never loses his cool. If you can get him to crack, the odds are good that your spacecraft is already doomed.
Nintendo Hard: While the newer navigation tools have made travel outside of Kerbin orbit much easier the game is still harsh and unforgiving.
While building finely balanced, efficient rockets and sending them to other worlds may not be particularly easy, this pales in comparison to trying to build a Single Stage to Orbit (SSTO) space plane and docking with your orbiting space station. Seriously, try it!
No Antagonist: The only obstacles to your progress are your own design or piloting mistakes. That and the harshness of space.
No OSHA Compliance: Parachutes, landing gear, or anything to insure the survival of your Kerbals are entirely optional. It is even possible to make rockets that face down.
No Plot? No Problem!: There's no real story or backstory to the game aside from player fanon. There's just you, your space program, a ton of rocket parts, a solar system filled with planets and moons, and an endless supply of eager would-be rocket jockeys.
Bill & Bob Kerman always look worried whenever the spacecraft is doing anything other than holding still. All characters do this if something explodes. If Jebediah ever stops grinning... see above.
With the addition of other Kerbonauts, it has been revealed that each one has a personality based on certain modifiers, which in turn determines how brave or cowardly each one is. One of these modifiers is if the Kerbal is trained as a pilot or not (either yes or no). If he is a pilot, he will be mostly happy. If not, he will scream his pants off.
Bob will always look terrified. He'll only calm down if the craft is confirmably drifting back to the surface slowly via parachute or has come to a complete, safe stop.
Outside Ride: Kerbonauts can ride on the outside of rockets by holding onto ladders, but they don't have especially strong grip (so be careful if you try it yourself and never try it when the craft is accelerating). Version .20 added seats; see Rocket Ride.
Quicksand Box: The game can be unforgiving sometimes, but fortunately there are a wealth of videos and forum threads out there to help, and there's plenty of fun in trying to figure out what gets out of atmo without ripping itself apart.
Reality Ensues: You may spend hours recreating a ship from your favorite sci-fi story only to find that it flies like a brick in the air or spins uselessly in zero-g... or tears itself apart while trying to fly.
Also, sure you can build a nice Global Airship to visit all the cool easter egg landmarks around Kerbin. You also have to take the time to sit around and fly it yourself, plus land it without crashing.
There is a steep valley on the Mun that was added in one of the patches. Naturally when this was discovered, the first thing the fanbase did was fly there to recreate the Death Star run. This turned out to be much less exciting with real world physics (and without enemy gunfire, as well). All you need to do is create a low enough orbit to pass through the canyon, cut engines, and gently thrust away from the walls.
Refining Resources: One planned future feature is the ability to harvest raw materials on other planets and refine them into useful things such as rocket fuel. Until then, there are mods that simulate this on a basic level, such as the Kethane mod.
Rocket Ride: 0.20 introduced official support for seats, mainly intended for rovers. Of course, sticking one to the side of a large rocket and launching it into the stratosphere was one of the first things a lot of users did.
Sci-Fi Writers Have No Sense of Scale: The developers avert this but the use of this trope in media has caused some confusion among players less familiar with actual astronomical scales. Even among those familiar with space flight don't always remember exactly how big space really is. For instance, some have suggested ignoring time acceleration (ie being able to increase the speed of the game) and instead allow the program to run essentially in the background to allow for realistic flight during extended missions. Even acknowledging that a single mission would very well be months long, they don't seem to realize that most of that time would be spent doing... nothing.
The distances are less than they would actually be, but that's due to the Space Compression. The scales for Kerbin/Mun/sun are roughly the same as for Earth/Moon/Sun accounting for it.
Self-Imposed Challenge: Making ridiculous rockets, making manned ballistic missiles, making space shuttle equivalents, spacecraft that look like specific patterns, achieving orbit, reaching relativistic speeds, getting a huge and completely pointless concrete cube into orbit, landing on the moons of Kerbin, landing on other planets, landing on the sun, flying to the North Pole, flying to the other Space Center, etc.
The "Advanced Grabbing Unit" is otherwise known as The Klaw.
If opening up a materials bay doors for science over Jool, the science report will tell the story of the computer saying "I'm sorry, I can't let you do that" and then hurriedly complying when you head to the fusebox.
Simple Yet Awesome: Encouraged by the Career mode introduced in the 0.24 "First Contract" update. Each rocket part now costs funds, of which the space program only has so much at any one time, making simple rockets with inexpensive and easily recovered and refurbished parts necessary for accomplishing elaborate objectives, where an unrestricted mode might favor flashier and less humble designs.
Simulation Game: It's not on the same realism level as Orbiter, but it's realistic enough to be a great way to learn basic orbital mechanics.
Single-Biome Planet: Kerbin up to version 0.17 is mostly grassland, with the exception of the poles, which are icy. 0.18 and above have rivers and deserts. Most of the other, lifeless bodies in the system are like this as well (with the possible exception of Duna and Laythe, which have ice caps), but since real-world planets without actual ecosystems also tend to lack easily discernible biomes, it's Truth in Television.
Starting with 0.22, different regions of Kerbin, the Mūn, and Minmus are now assigned to different "biomes", which will give different research data when experiments are performed within them. However, the Mün and Minmus biomes are closer to geographical areas (e.g., "Lowlands", "Midlands", and Highlands") than to the different ecological and climatic regions to which the term usually refers. But then, neither of those planets has any atmosphere or biosphere, so the term "biome" is a misnomer in their context. Similarly, Eve and Laythe have separate 'surface' and 'water' biomes in which to do science.
Removed as of 0.16, but hopefully we'll see a return.
Soft Water: Averted. A hard splashdown can outright destroy a spacecraft and its unlucky passengers.
In fact, splashdowns are often actually more dangerous than landings on solid ground, since when a spacecraft hits the water, it doesn't slow down very quickly. Consequently, all or most parts on it must pass a check to see whether or not their actual splashdown velocity exceeds their rated maximum impact velocity. If it does, they're destroyed. Often, this leads to oceans swallowing up entire spaceships, leaving only a few high-impact-tolerance girders or decouplers bobbing in the water. By contrast, when a spaceship impacts land, the first parts that hit the ground absorb some of the impact velocity and it decelerates much more quickly, giving parts (and crew) far away from the point of impact a chance of survival.
Space Compression: To cut down orbit times and prevent the game from becoming astronomically boring, Kerbin is a mere 1200km in diameter. Jool, the gas giant, is roughly the size of Earth. The orbits of planets and moons are similarly scaled down.
Not counting certain glitches or the Space Kraken, of course...
Space Friction: Averted; spacecraft obey Newtonian physics and will slow down only under power or when passing through an atmosphere. Objects that achieve escape velocity from the star will fly away into the infinite void.
Space Is Noisy: Even in the depths of space, you can still hear rockets and explosions.
Partially justified in that most of those explosions happen either in-atmosphere or when you're still attached to the thing blowing up/making noise, giving the sound a medium on which to propagate to your ears.
Stuff Blowing Up: If any part of a spacecraft hits the ground (or another part) too fast, it makes a nice explosion. The interesting thing is that fuel tanks full of rocket fuel make the same explosion than, say, parachutes or scientific equipment. These explosions seem not to harm other parts though.
Struts For Everything: For the moment, the best solution to any problem involving the rocket coming apart is simply "Add more struts." This may change when the atmospheric drag model is overhauled in future versions.
Subsystem Damage: Each individual rocket part has its own parameters, including heat and impact tolerances. With a little luck, you can even save your crews from crashes that will destroy the rest of the vehicle.
Suspend Save: While your game autosaves periodically to prevent blatant Save Scumming (not that it really needs to at this stage), there's also a single-use quicksave feature that allows you to save at various points during a mission so that you don't have to launch an entirely new rocket if your current one suddenly becomes a million-dollar lawn dart.
The scientific thermometer is totally not a store-bought model, and admitting that it is voids its warranty.
Taken to extremes with the Not-Rockomax Mini Node, which is so obviously not a miniaturized version of an already-existing part that the (in-universe) manufacturers helpfully point out the complete lack of a resemblance in the name.
Tech Tree: A feature of the game added in the .22 update. Kerbonauts and probes can now gather science in flight in Career mode, which you can use to research technology to gather more parts.
More particularly, any aircraft on Eve actually flies more easily than it does on Kerbin thanks to Eve's atmosphere being five times thicker, which makes even improbable designs workable. Especially since any such craft cannot functionally use jet engines due to the atmosphere lacking oxygen with which to power their internal combustion, and it must use other methods of thrust.
Tidally Locked Planet: Mun is tidally locked to Kerbin, Duna and Ike are mutually tidally locked, and Laythe, Vall, Tylo, Bop, and Pol are tidally locked to Jool.
Tim Taylor Technology: Fan lore is that almost any problem you have with a rocket can be solved with "MOAR BOOSTERS!!"
Too Dumb to Live: The numerous shorts Squad has made to advertise the game are filled with this behavior. The worst offender? One kerbonaut finds that a wrench he needs has somehow gotten into his helmet. So, he decides to take his helmet off to get it. While standing on the Mun. Which has no air. And another kerbal reacts to seeing the ownerless helmet rolling around by grabbing at his own helmet as if it might spontaneously come off.
Truth in Television: Sure NASA and the other space programs have brilliant engineers and scientists to build their spacecrafts, but sometimes things go a little Kerbal anyway. The tragedies are, of course, tragic, but those aside, here are a few more lighthearted examples:
This note◊ painted on the Shuttle Carrier Aircraft.
The Soviet N1 rocket with 30 engines on the first stage is quite Kerbal◊.
When training for the Moon landing, Neil Armstrong bailed out of the "Flying Bedstead" aircraft after losing control of it. His fellow astronauts were amazed at how unfazed he was by the incident.
Those who find rendezvous and docking to be difficult and counterintuitive may take comfort in the fact that early astronauts in the real world got off to a rocky start with it themselves. Gemini 4 was America's first attempt at having two different craft rendezvous in space. Unfortunately, neither the astronauts nor the ground crew fully understood the orbital mechanics involved, and so as they tried to thrust towards the target from a higher orbit, they ended up actually speeding away from it, which is completely backwards from how things are on the Earth's surface but makes perfect sense once you realize that they were thrusting into a lower orbit by firing against their own orbital velocity, which would make them orbit faster in the long run.
The game's fandom (at least on the official forums) rejoiced on at least two occasions due to mentions from people who work in space science. The first was when Neil deGrasse Tyson tweeted that he thought the game looked fun and would probably spend "far too much time" playing it if there was a Mac version. (This resulted in the until-then low-priority OSX port becoming the absolute #1 priority for the devteam!)
The second was, if anything, an even bigger reaction when, in response to a question on their blog, NASA's Curiosity Mars rover team stated that there were a number of people on the team who liked to play KSP during their free time. The unpaid endorsement by a group of REAL rocket scientists (or close enough to it for all practical purposes) set off tears of joy from the user base.
Former Astronaut Ed Lu played the game with Scott Manley, Ed's first flight crashed in less than 30 seconds, the second got into space, but not into orbit.
Unexpectedly Realistic Gameplay: See also the entry for Art Style Dissonance. While it's fairly easy to build and launch a simple rocket, actually getting that rocket into orbit or to places other than Kerbin is fairly difficult if you're more used to less realistic space simulators.
Videogame Caring Potential: Some players equip their crew capsules with not only parachutes but various other elaborate safety and/or abort systems, rescue all stranded Kerbals, and try to land returning ships as close to the Kerbal Space Center as possible...
Video Game Cruelty Punishment: ... and then in career mode as of 0.24, losing Kerbals will reduce your reputation, lowering the quality of the contracts that are offered to you because losing crew makes you look incompetent to investors.
Violation of Common Sense: The best way to land a falling Kerbal? On their head. Their helmets can survive practically anything!
With this in mind, you can usually save a Kerbonaut from a doomed aircraft by simply having him step out the hatch while low enough to the ground.
Weaponized Exhaust: An (often) unintentional example of using this on yourself if you are not careful with spaceship construction. All engines have heat tolerances which, when exceeded, will damage the engine. Too many engines too close together can overheat each other at full thrust, and other parts of the spacecraft too near the exhaust might be damaged as well.
Also, if anything comes loose near a working engine, even a Kerbal, it will be launched off into the horizon at unsurvivable speeds, so standing near engines in general is not a good idea.
Laythe also has liquid water and surface temperatures that would let humans -and presumably kerbals- walk around near the equator with nothing but a warm coat, despite being much too far from the sun for this to be possible without some other mechanism. However, the developers have cunningly placed it in a Laplace orbital resonance with 2 other Joolian moons. The heating is supposed to come from the tidal interaction between these objects, in the same way that Io is kept hot enough to have volcanoes in our own solar system
Wide Open Sandbox: In Sandbox mode, money has no importance and there are no goals. 0.22 has added a rudimentary campaign with a limited selection of starting parts and the option to unlock more by researching your way up a Tech Tree, while 0.24 has continued to flesh out the campaign with funding and reputation systems to place additional limits on your space program. Even then there's no storyline as such, and you're free to do whatever you want within the limits of your available parts.
Yes-Man: Played with. No KSC worker bats an eye at the exploding machines of death you bring on to the launchpad, with the exception of some scientists, who will frequently stop and look at your rockets in horror before walking away in the VAB. Regardless of how sound or unsound the design in question is.
You ALL Look Familiar: All Kerbonauts have the exact same face and haircut, as well as the last name of "Kerman." Whether they're all clones, a family of Inexplicably Identical Individuals, or just members of a very homogenous species is a matter of some fan speculation. They aren't all perfectly identical, though, as they have individualized personalities determined by different levels of Bravery and Stupidity, as well as a hidden Pilot Training (or "BadS") flag.