Kerbal Space Program

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Kerbal Space Program (space simulator)
Kerbal Space Program High Res Logo.png
Programmer(s)Marco Salcedo, Jesus Montaño[1]
Platform(s)Windows, Mac OS X, Linux
Release date(s)June 24, 2011 (alpha 0.7.3)[2]

July 25, 2014 (latest, alpha 0.24.2: First Contract)[2]

Genre(s)Space flight simulator
Mode(s)Single-player sandbox, single player science mode single-player career mode
DistributionDigital download
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Kerbal Space Program (space simulator)
Kerbal Space Program High Res Logo.png
Programmer(s)Marco Salcedo, Jesus Montaño[1]
Platform(s)Windows, Mac OS X, Linux
Release date(s)June 24, 2011 (alpha 0.7.3)[2]

July 25, 2014 (latest, alpha 0.24.2: First Contract)[2]

Genre(s)Space flight simulator
Mode(s)Single-player sandbox, single player science mode single-player career mode
DistributionDigital download

Kerbal Space Program (commonly abbreviated to KSP) is a space flight simulator developed by Squad currently in public alpha development for release on Windows, Mac OS X, and Linux. The first public version was released on June 24, 2011,[3] and is currently sold on the online official KSP Store, and since March 20, 2013, through Steam's early access program,[4] where it reached the top 3 best sold games.[5] Updates have been continuously released. KSP has large support for game mods and a large community to create them,[6] which developed shortly after the game's start.[7] Notable members of the space industry have taken an interest in the game.[8][9]


A rocket sitting on the launchpad with the Vehicle Assembly Building and Mün, Kerbin's nearest moon.

The player controls a nascent space program operated by Kerbals, a race of small green humanoids, who have constructed a fully furnished and functional spaceport (known as the Kerbal Space Center, or KSC) on their homeworld Kerbin, similar to Earth.

Kerbals are generally shown as funny cartoon-like little green men, sometimes lacking common sense, resulting in an endless stream of flight volunteers with no care for safety procedures,[10] but they have shown to be able to construct very-well-made spacecraft parts and perform experiments in the lab.

Gameplay consists of constructing rockets and spaceplanes out of a provided set of components and launching them from the in-game space center's launch pad or runway, then going on to complete their desired mission assuming no catastrophic failure.

Because of all the different things a player needs to monitor and the difficulty of grasping orbital mechanics, the game has a steep learning curve.[11]

Missions (although entirely player-set) generally involve, from simplest to most complex, achieving orbit, landing on the Mün/Minmus (both moons of Kerbin), landing on other planets,[12] capturing asteroids and creating space stations and bases.[13]

In the Vehicle Assembly Building and Spaceplane Hangar, many intricate designs can be constructed using the wide selection of engines, fuel tanks, wings, and structural parts,[14] with options for symmetry, viewing the center of mass, lift, and thrust, choosing a crew roster (if manned), and creating shortcuts for keys and buttons in the game's in-flight GUI. Possible designs range from massive multi-stage rockets to aerodynamic SSTO craft. To prevent craft failures, players need to worry about weight, thrust, stability, and structural integrity.[15] Players can also create aircraft and rudimentary boats.

Vehicles can be equipped with solar panels, RCS thrusters, wheels, and other miscellaneous components for the player's needs. Once launched, spacecraft can be navigated to other celestial bodies and landed for surface operations, assuming they have enough Delta-v. Multiple craft can also be docked in orbit to construct space stations and interplanetary tugs without using huge rockets.

Players can manage the spaceport's Kerbal astronaut roster, hired from the Astronaut Complex. They all share the same surname "Kerman." Players can choose personnel to assign to seats. In space or on land, Kerbals can exit the spacecraft safely to perform an extra-vehicular activity (EVA), usually to gain Science or plant a flag.

In the Tracking Station, it is possible to see celestial bodies and craft in-flight when the player is not focusing on the craft. With the Asteroid Redirect Mission, the Tracking Station can track discovered unknown objects (asteroids) and find out their trajectory for a mission to capture asteroids.[16] The longer an asteroid is tracked, the more accurate its trajectory is.[17]

Hired astronauts are ranked (as of version .24) by two factors: courage and stupidity. Kerbals all have randomly generated names with pseudo-randomly generated stats (except for the three starting crew whose names and stats are fixed), with a 10% chance of having the badass ("badS") flag.[18] There are over 11,000 unique Kerbal names that can be generated.[19]

Once a spacecraft is built, it is placed on the launchpad or the runway and is ready for launch. Players control a spacecraft in all three dimensions with little assistance other than a stability system to keep a rocket pointed at a certain direction.[20] If the rocket has enough thrust and delta-v, it is possible to reach orbit. In flight, to visualize the player's trajectory, the player must switch into map mode, which shows the orbit or trajectory of the current craft, and the current position of other spacecraft and planetary bodies.[20]

The game can be played in three different gamemodes that are selected when the player starts a new game: sandbox mode, science mode, and career mode.[21] In sandbox mode, players are free to attempt any mission for which they can construct a suitable vehicle, with no punishments for failure[22] (except the temporary death of Kerbals who died during a mission) and using entirely user-assigned missions.

In Science mode, the initial selection of parts is limited, with the more advanced parts unlocked via "Science,"[21] in the Research and Development building, gained by performing various scientific experiments on Kerbin and throughout the solar system. Science mode was partially designed to ease new players into the game and prevent them getting overwhelmed.[23] Science gained on a mission needs to be received by the space port.[24] This can be done by transmissions via antennas[21] in the game, or recovery by a craft landing back on Kerbin. Career mode is an extension upon science mode, adding funds, reputation, and contracts. In order to build and launch new rockets, the players most complete contracts to earn funds to pay for the new parts. Reputation will affect how many contracts are given to the player in a future update (less reputation leads to fewer contracts).

Historical spacecraft can be recreated and their accomplishments mimicked, such as the Apollo program, the Mars Science Laboratory rover, or the International Space Station.[25] Players may also install mods which can implement destinations, rocket parts, and goals for the game, such as mining for resources or incrementally deploying an interplanetary communication network.

Game development remains ongoing and the studio, Squad, have promised that in the future new features will be added, such as damage due to air compression in reentry, and a system for creating reusable spacecraft.[26]

Celestial bodies[edit]

Kerbal Space Program contains varying celestial bodies to land and perform experiments on.[12] As of version 23.5, the star system contains five major planets, two dwarf planets (as stated by the developers) and nine natural satellites. Because there are no asteroid belts yet, although there are asteroids, according to the IAU's definition of a planet, one of the two dwarf planets in the game are not dwarf planets as they do not have a neighborhood of asteroids in similar orbits.

All the planets and dwarf planets orbit around a yellow star. Because of the game's dwarfed planetary (and solar) size, the Sun in the game is too small to have fusion undergoing in its core assuming real-life astrophysics.[27] Fans of the game often call the star Kerbol, after Kerbals, though no official name has been given.[27]

The planetary bodies are as follows, from the closest to the Sun to the farthest.

Easter Eggs/References[edit]

There are many Easter eggs and references scattered throughout the Kerbol system, the most common of which are black monoliths scattered on the surfaces of many of the celestial bodies.


The game has been praised for its realistic representation of orbital mechanics.[14][28] Every object in the game except the celestial bodies themselves are under the control of a Newtonian dynamics simulation. Rocket thrust and aerodynamic forces are applied accurately to a vehicle's frame based on the positions in which the force-generating elements are mounted. The strength of the joints connecting parts together is finite and vehicles can be torn apart by excessive or inappropriately directed forces.

Some planets have atmospheres of varying heights and densities, affecting the efficiency of wings and parachutes and causing drag during flight. The simulations are accurate enough that real-world techniques such as Hohmann transfers and aerobraking are viable methods of navigating the solar system. Centrifugal force is modeled and players have created torus stations which exhibit measurable artificial gravity and can be traversed by wheeled rovers. The game simulates trajectories and orbits using patched conic approximation instead of a full n-body simulation, and thus does not support Lagrange points and halo orbits. According to the developers, full n-body physics would require the entire physics engine to be rewritten.[29]


Notable inaccuracies include the perfect reliability of equipment (equipment generally only fails with excessive force) and the lack of life-support consumables. Kerbals can survive indefinitely in space either in a capsule or a space suit.[25] This simplifies orbital rendezvous by making it practical to wait multiple orbits until a desirable alignment is reached. Also, Kerbals have extremely capable EVA suits with 600 m/s of Δv. This is 24 times the capability of NASA's manned maneuvering unit, sufficient to reach orbit from (or even land on, return to orbit from, and rendezvous with a spacecraft orbiting around) small moons,[30] and allows EVA transfer between markedly different orbits.

The celestial bodies in the Kerbal solar system are about 1/10 the radius of their real-universe equivalents yet have comparable surface gravity,[6] implying that they have unrealistically high densities. This change to scale makes many tasks considerably easier. For example, a surface to low-Kerbin-orbit launch requires a delta-v of about 4.5 km/s, compared to 9.5 km/s for a low-Earth-orbit launch. In particular, because of the game also having unrealistically efficient and flexible (in terms of speed and altitude) turbojet engines, this means it is much easier to make a single-stage-to-orbit vehicle using jet engines to accelerate a vehicle to orbital speed on only a small fraction of its mass in jet fuel, then give a tiny boost with rockets to reach orbit, whereas in real life, a highly efficient but powerful and lightweight scramjet would be necessary to do the same with several times the amount of fuel.

The game's aerodynamic model applies drag force to parts based on a "drag coefficient" multiplied by the part's mass (remaining mass for fuel tanks) multiplied by the air density at that altitude multiplied by the speed of the part multiplied by a constant. This results in conventionally aerodynamic designs being unaerodynamic, and most designs having unrealistic levels of drag (often by orders of magnitude for large needle-like rockets). This also means that nose cones actually add drag to a vessel. The relatively minor drag on the nose cone is added to the drag of the other parts. This drag also reduces the effects of steep reentry trajectories and high-speed flight by applying drag forces evenly distributed between the mass of the vessel (except for nose cones, which may go flying off of the front of the vessel, and parachutes, which may pull the back of it off). Lift is calculated in a similar manner and so some planes can have unrealistically far forward wings and not become aerodynamically unstable. Also, non-wing parts do not generate lift, meaning, for example, that re-entering space capsules are neutrally stable in all directions and free to rotate, whereas in reality, they are intended to point heat-shield-down. No re-entry shock heating has been implemented yet;[26] although an effect exists to show the flames generated by re-entry, it currently is harmless to the spacecraft itself. Also the re-entry effects like heating up and the decrease of velocity stops on parts that are separated from the main space vehicle during re-entry. This could be for example the service module.


The game is currently in the alpha stage of development and is considered by the developers to only be a small approximation of the final product.[31] New features are added regularly in updates to the game. No schedule or criteria for transition into beta or final release have been announced. KSP is written in C# and uses the Unity engine.

The game's first public release was Alpha 0.7.3 on June 24, 2011. The game has been moddable from the very early versions[2] and has steadily become more robust.[32] Versions 0.13.3 (March 3, 2012) and 0.18.3 (February 12, 2013) are available, in limited form, as demos; they are available at no cost, but have limited content and can not receive updates. The latest version of the game, 0.24, was released on July 18, 2014.[13]


KSP allows support for extensive modding,[33] allowing anything from craft parts to whole autopilot systems and changes to the game's physics to be created. All mods can be hosted on the game's official mod site,, which can be accessed via a link in the main menu.

There are a wide variety of available mods. The most notable ones add autopilot tools,[34] geodetic mapping systems, resource scanning and harvesting, various methods of life support for crew members, data graphing systems, communications network systems, and extensive collections of new parts.[34] (including recreations of real and historic spacecraft, including Apollo, SLS, and the Space Shuttle) Many mods have attempted to cover aspects of the game that have not yet been developed by Squad, (such as adding re-entry heat and implementing accurate drag physics) and some mod-makers have even been hired by Squad to do in-house work due to their mod's comparatively high quality.

On January 27, 2014, it was revealed that Squad is working on an education-themed mod entitled KerbalEdu in collaboration with TeacherGaming LLC (of MinecraftEdu). It will include an improved user interface for easier data gathering and summary, pre-made lessons that focus on certain constructions, options to use the metric system, and a "robust pedagogy" that includes information outside of the game that ties into its content.[35][36]

Squad has also made an Asteroid Mission Pack (update 23.5) with full support from NASA, that was released on April 1, 2014. It is based on a real-life initiative to send humans out to study asteroids.[13][37]



Although the game is still in alpha, KSP is already considered a success, having over 100,000 members registered on their forums with over 5,500 active users.[38] In the hours after its Steam release on March 20, 2013 it reached the top 5 of best sold games,[5] as well as the best seller on Steam for Linux.[39]


The public alpha releases have been well-received so far. Many publications and individual people have referred fondly to Kerbal Space Program and praised the game's replayability and creative aspects, including Kotaku,[40] Rock, Paper, Shotgun,[20][41] IGN,[42] PC Gamer,[43] Gamespy,[44] Eurogamer,[12] Polygon,[28] Destructoid,[45] and The Torch.[46] It has also received a substantial following on Reddit with over 77,000 readers.[47]

Scientific community[edit]

The game has notably crossed over into the scientific community with scientists and members of the space industry having an interest in the game – including NASA[8] and Copenhagen Suborbitals.[9]

See also[edit]


  1. ^ Squad's Meet the Team Page Retrieved April 25th, 2014
  2. ^ a b c "Version history – KSP Wiki". Kerbal Space Program Wiki. December 16, 2013. Retrieved December 16, 2013. 
  3. ^ Kerbal Space Program Official Wiki (v0.7.3) Retrieved 25/04/2014
  4. ^ Villapaz, Luke (April 2, 2014). "'Kerbal Space Program' Launches NASA 'Asteroid Redirect Mission' Update". International Business Times. Retrieved May 1, 2014. 
  5. ^ a b Relaxnews (June 17, 2013). "PC Download Charts". xin.msn. Retrieved July 22, 2014. 
  6. ^ a b Rossignol, Jim (December 18, 2012). "Trajectory: Squad Explain Kerbal Space Program". Rock, Paper, Shotgun. Retrieved May 2, 2014. 
  7. ^ White, Sam (May 22, 2014). "Minecraft in space: why Nasa is embracing Kerbal Space Program". The Guardian. Retrieved May 22, 2014. 
  8. ^ a b c Andrew Groen (June 18, 2013). "NASA’s Jet Propulsion Lab is obsessed with a certain game, and I bet you can guess what it is". The PA Report. Archived from the original on December 27, 2013. Retrieved June 19, 2013. 
  9. ^ a b "Copenhagen Suborbitals joins KSP Forums". KSP Forums. May 1, 2013. Retrieved August 6, 2013. 
  10. ^ Zuev, Artyom (July 31, 2013). "Environment art and modeling in Kerbal Space Program". Gama Sutra. Retrieved May 2, 2014. 
  11. ^ Kalican, Aykurt (May 30, 2013). "A Mission to Mun: Kerbal Space Program". Electric Feast. Retrieved May 4, 2014. 
  12. ^ a b c 31-01-2014 Eurogamer "Kerbal Space Program Early Access Review" Retrieved 25-04-2014.
  13. ^ a b c Fingas, Jon (April 2, 2014). "NASA's game collaboration lets you steer asteroids without leaving home". Engadget. Retrieved April 25, 2014. 
  14. ^ a b Emanuelli, Matteo (August 12, 2013). "Kerbal Space Program, the Spaceflight Simulator That Conquered JPL". Space Safety Magazine. Retrieved May 2, 2013. 
  15. ^ Nicholls, James (March 10, 2013). "Hidden Gems of the Gaming World: – Kerbal Space Program Review". Games-Tec. Retrieved May 2, 2014. 
  16. ^ Gee, Sue (April 13, 2014). "NASA Contributes Mission to Kerbal Space Program". I-Programmer. Retrieved May 1, 2014. 
  17. ^ McKinnon, Mika (April 1, 2014). "Kerbals and Asteroids: What could possibly go wrong?". io9. Retrieved May 2, 2014. 
  18. ^
  19. ^
  20. ^ a b c Craig Pearson (May 24, 2013). "(Not) Rocket Science In Kerbal Space Program". Rock, Paper, Shotgun. Retrieved June 19, 2013. 
  21. ^ a b c Devore, Jordan (October 17, 2013). "Kerbal Space Program Finally Gets Career Mode". Destructoid. Retrieved April 26, 2014. 
  22. ^ a b Gilson, Adam (March 30, 2014). "Kerbal Space Program - Review". Retrieved April 26, 2014. 
  23. ^ Nealie, Cam (February 10, 2014). "Kerbal Space Program review". 3news. Retrieved April 26, 2014. 
  24. ^ Groen, Andrew (October 17, 2013). "Kerbal Space Program is finally an actual game and it’s magnificent". The PA Report. Retrieved May 1, 2014. 
  25. ^ a b Russin, Aaron (May 1, 2013). "Kerbal Space Program raises metaphysical questions of purpose". Spectator Tribune. Retrieved May 2, 2014. 
  26. ^ a b "Planned features - Kerbal Space Program Wiki". Retrieved 2013-11-22. 
  27. ^ a b "Kerbol". Kerbal Space Program Wiki. Retrieved April 25, 2014. 
  28. ^ a b "To the Mun and Back: Kerbal Space Program". Polygon. January 27, 2014. Retrieved April 25, 2014. 
  29. ^ McRed, Targie (February 13, 2013). "Kerbal Space Program: Q&A with the devs". The Mittani. Retrieved May 2, 2014. 
  30. ^ Escaping the Mun Using A Broken Ship & EVA Suit
  31. ^ "About". Kerbal Space Program. Retrieved July 18, 2013. 
  32. ^ "Plugins - Kerbal Space Program Wiki". February 22, 2013. Retrieved August 30, 2013. 
  33. ^ October 9, 2013 - University Press Online "'Kerbal Space Program' is an Out-of-This-World Sandbox" Retrieved April 25, 2014.
  34. ^ a b Savage, Phil (November 23, 2013). "The 17 Best Kerbal Space Program Mods". PC Gamer. Retrieved April 26, 2014. 
  35. ^ Matulef, Jeffrey (27 January 2014). "Kerbal Space Program lands on various schools' curriculum". Eurogamer. Gamer Network. Retrieved 28 January 2014. 
  36. ^ Warr, Philippa (January 24, 2014). "Kerbal Space Program to get children as well as Kerbals into space". Wired. Retrieved April 25, 2014. 
  37. ^ Sarkar, Samit (April 1, 2014). "Kerbal Space Program's Asteroid Redirect Mission now available". Polygon. Retrieved April 25, 2014. 
  38. ^ "Kerbal Space Program Forum". Squad. Retrieved June 20, 2013. 
  39. ^ Silviu Stahie (April 1, 2013). "Kerbal Space Program Is the Best-Selling Game on Steam for Linux". softpedia. Retrieved June 18, 2013. 
  40. ^ Luke Plunkett (July 18, 2011). "Will You Help These Stupid Aliens Into Space?". Retrieved August 18, 2013. 
  41. ^ "Trans-Lunar: Kerbal Space Program". Rock, Paper, Shotgun. July 12, 2011. Retrieved August 18, 2013. 
  42. ^ Anthony Gallegos (April 21, 2012). "Five Ridiculous Upcoming Games". IGN. Retrieved November 12, 2012. 
  43. ^ "Kerbal Space Program". PCGamer. Retrieved June 29, 2013. 
  44. ^ Mike Nelson (March 29, 2012). "Become a Terribly Awesome Rocket Scientist With Kerbal Space Program". GameSpy. Retrieved June 19, 2013. 
  45. ^ Lyons, Sterling (February 5, 2012). "Revisiting the Kerbal Space Program". Destructoid. Retrieved April 26, 2014. 
  46. ^ Atomp (January 31, 2013). "Kerbal Space Program (Beta) , SQUAD (P)review". The Torch. Retrieved June 19, 2013. 
  47. ^ "/r/KerbalSpaceProgram statistics". Retrieved August 12, 2014. 

External links[edit]