Kerbal Space Program
Kerbal Space Program is a space flight simulation video game developed and published by Squad for Microsoft Windows, macOS, Linux, PlayStation 4, and Xbox One. In the game, players direct a nascent space program, staffed and crewed by green humanoid aliens known as "Kerbals". The game features a realistic orbital physics engine, allowing for various real-life orbital maneuvers such as Hohmann transfer orbits and bi-elliptic transfer orbits.
The first public version was released digitally on Squad's Kerbal Space Program storefront on 24 June 2011, and joined Steam's early access program on 20 March 2013. The game was released out of beta on 27 April 2015. Kerbal Space Program has support for user-created mods that add new features, and popular ones, such as those for resource mining and context-based missions, have received support and inclusion in the game by Squad. People and agencies in the space industry have taken an interest in the game, including NASA and the European Space Agency.
In May 2017, Squad announced that the game was purchased by video game company Take-Two Interactive, who will help support Squad in keeping the console versions up-to-date alongside the personal computer versions. An Enhanced Edition was released on the Xbox One and PlayStation 4 in January 2018 by Private Division, a publishing subsidiary of Take-Two Interactive. Two expansions for the game have been released as downloadable content: Making History in March 2018 and Breaking Ground in May 2019. A sequel, Kerbal Space Program 2, has been announced for a 2021 release.
Gameplay
The player administers a space program operated by Kerbals, a species of small green humanoids, who have constructed a fully furnished and functional spaceport called the Kerbal Space Center on their home planet, Kerbin. Despite being shown as cartoonish beings sometimes lacking common sense, Kerbals have shown themselves capable of constructing complex spacecraft parts and performing experiments to realize their scientific goals.Players can create rockets, aircraft, spaceplanes, rovers, and other craft from a provided set of components. Once built, the craft can be launched by players from the KSC launch pad or runway, or other launch pads and runways around Kerbin, in an attempt to complete player-set or game-directed missions while avoiding partial or catastrophic failure. Players control their spacecraft in three dimensions with little assistance other than a stability system called "SAS" to keep their rocket oriented. Provided it maintains sufficient thrust and fuel, a spacecraft can enter orbit or even travel to other celestial bodies. To visualize vehicle trajectory, the player must switch into map mode; this displays the orbit or trajectory of the player vehicle, as well as the position and trajectory of other spacecraft and planetary bodies. These planets and other vehicles can be targeted to view information needed for rendezvous and docking, such as ascending and descending nodes, target direction, and relative velocity to the target. While in map mode, players can also access maneuver nodes to plan out trajectory changes in advance, which helps in accurately planning burns to other planets or celestial bodies.
Missions involve goals such as reaching a certain altitude, escaping the atmosphere, reaching a stable orbit, landing on a certain planetary body, capturing asteroids, and creating space stations and surface bases. Players may also set challenges for each other on the game's forums, such as visiting all five moons of Jool, or use mods to test each other's spacecraft in air combat tournaments.
Players can control in-game astronauts, known as Kerbals, who can perform extravehicular activities. While on EVA, Kerbals may use their EVA suit propellant system to maneuver in space and around craft and space stations, similar to the use of NASA's Manned Maneuvering Unit. Actions that can be performed while on EVA include repairing landing legs, wheels, and deploying or repacking parachutes. Kerbals can also collect material from science experiments, allowing them to store data inside the ship's capsule. During an EVA on any solid planet or moon, a Kerbal can place a flag or take a surface sample.
Historical spacecraft can be recreated and their accomplishments mimicked, such as the Apollo program, the Mars Science Laboratory rover, or the International Space Station. Players may install mods which implement destinations, weapons, additional rocket parts, and goals, such as attempting challenges in a real-scale solar system. Mods can also add informational displays showing craft and orbital statistics such as delta-v and orbital inclination, while a few can near-fully automate flight. Some mods have been added into the game, due to popularity. For example, resource mining, in order to obtain Ore for refining into resources such as fuel, has been implemented from a popular mod.
As of version 1.9.1, the major celestial bodies in the game in order of their proximity to the parent star, the Sun, are Moho, Eve, Kerbin, Duna, Dres, Jool, and Eeloo. Community modifications are able to expand this planetary system to include analogs of the missing outer planets, as well as fictional bodies and faraway exoplanet systems. Moons in the system include the captured asteroid around Eve, Gilly; the two moons of Kerbin, Mun and Minmus; The singular moon of Duna, Ike; the technically unlimited "moons" of Dres, being asteroids which randomly spawn in, called the Drestroid Belt by fans; and the five moons of Jool. The innermost is an ocean moon dotted with sandy islands, Laythe, the only moon to have an atmosphere and only other body in the solar system to have liquid water besides Kerbin; Vall, an ice moon; Tylo, a moon the size of Kerbin; Bop, another captured asteroid; and Pol, the outermost moon of Jool. Eeloo has no natural satellites.
Game modes
The player starts a new game by choosing one of three game modes: sandbox, science, and career mode. In sandbox mode, players may attempt to construct a suitable vehicle for any desired project without penalties for failure and entirely user-assigned missions. Many players have constructed unrealistic spacecraft in this mode, such as impractically large, complicated, or expensive rockets. This mode is also frequently used to create replicas of real-life aircraft, rockets, trains, boats, cars, and other types of vehicles.In science mode, the initial selection of parts is limited. More complex parts can be unlocked in the Research and Development building by advancing "science" with various experiments on Kerbin and elsewhere throughout the solar system. This mode was designed to ease new players into the game and prevent them from getting overwhelmed.
Career mode extends science mode by adding funds, reputation, and contracts. To build and launch new rockets, the players must complete contracts, earning funds to pay for the necessary parts. Reputation affects how many contracts are given to the player; less reputation leads to fewer, lower-quality contracts. Declining a contract will reduce the likelihood that a contract of the same type will appear later. Simultaneously, players must upgrade buildings in the space center to unlock new features such as improved tracking, higher spacecraft mass limit, larger part count limit, and increased available contracts.
Currencies
There are three currencies in Kerbal Space Program: Science, Credits or Funds, and Reputation. Although credits are the in-game analogs of money, Science and Reputation are referred to as currency as well. In Sandbox mode, no currencies are available, as there is no need for them. In Science mode, only science is available. All three currencies are available in Career mode.Science is gained by performing experiments or crew reports. The experiments can only be turned into Science through either transmissions via antennae or recovery of a craft on Kerbin. Recovery of an experiment is worth more science than transmitting it. Each time an experiment is turned into science, it is worth less science the next time it is recovered, until it is worth no Science at all.
Funds, or credits, can be obtained in two ways: One; completing contracts by various agencies, and Two; by exploring new celestial bodies. The Kerbin World Record-Keeping Society does have contracts; however, the rewards for exploring celestial bodies are not contracts. Contracts are accepted through the Mission Control building in KSC, and are completed during flight.
Reputation is gained through successful missions, and lost through failed ones. It is essentially how safe Kerbals believe it is to fly on spacecraft. Generally, the better the space program's reputation, the better are the contracts received.
Physics
While the game is not a perfect simulation of reality, it has been praised for its accurate orbital mechanics; all objects in the game except the celestial bodies are simulated using Newtonian dynamics. For instance, rocket thrust is applied to a vehicle's frame based on the placement of force-generating elements, and joints between parts have limited strength, allowing vehicles to be torn apart by excessive or misdirected forces.The game simulates trajectories and orbits using patched conic approximation instead of a full n-body simulation; thus, it does not support Lagrange points, perturbations, Lissajous orbits, halo orbits or tidal forces. According to the developers, implementing full n-body physics would require the entire physics engine to be rewritten.
The in-game astronauts, Kerbals, are physically simulated. Hitting an object with their feet will cause them to tumble.
Some celestial bodies have atmospheres of varying heights and densities, affecting the impact of drag on wings and parachutes. The simulations are accurate enough that real-world techniques such as aerobraking are viable methods of navigating the solar system. Aerobraking, however, has become a much more difficult method of velocity reduction since the full 1.0 release due to improved aerodynamics and optional heating during atmospheric entry. In-game atmospheres thin out into space but have finite heights, unlike real atmospheres.
Kerbal Space Program alters the scale of its solar system for gameplay purposes. For example, Kerbin has a radius of only, approximately that of Earth's. To compensate for the gravitational consequences of this size difference, Kerbin's density is over 10 times that of Earth's. The planets themselves are also significantly closer together than the planets in the real-life solar system. However, some mods port the real-world solar system into the game with accurate scaling, environments, and additional parts to make up for the extra power requirements.
Expansions
There are two downloadable content expansions: Making History and Breaking Ground.;Making History
The Making History, released March 2018, adds additional elements to the game, some of which are historic parts from the Apollo program. These include a lunar lander, basic rocket parts of the Saturn V and more. A level editor allows the players to create their own scenarios. New launch sites, including an island, are added.
;Breaking Ground
Breaking Ground, released May 2019, adds robotic parts, which can be used to build helicopters, propeller airplanes, and robots. The parts include pistons, hinges and rotors. New suits were added as well. A major addition are surface features and science. The player can find certain rocks on surfaces of planets and analyse them using robotic arms. Science experiments such as active seismometers and weather stations can be deployed by the Kerbals and can be used to gather extra science points in science and career mode.
Development
Pre-development
Director Felipe Falanghe was hired by Squad in April 2010. At the time, the company did not develop software. According to Falanghe, the name "Kerbal" came from the names he gave small tin figurines he installed in modified fireworks as a teenager. In October 2010, development on Kerbal Space Program was authorized by co-founder Adrian Goya but deferred until Falanghe had completed his projects. Kerbal Space Program was first compiled on 17 January 2011. The game's first public release, version 0.7.3, was on 24 June 2011. The game entered beta on 14 December 2014, with version 0.90, and was released out of beta on 27 April 2015.Alpha
Version 0.7.3 was the first public release of Kerbal Space Program, and was released on 24 June 2011. It was downloaded over 5,000 times. Compared to future versions of this game, 0.7.3 was quite rudimentary. There was no stability assist mode, Kerbin did not rotate and the Sun was simply a directional light source. There were no fuel flow mechanics, no control surfaces, and no other celestial bodies. Later versions added additional planets and moons, as well as the ability to load and save collections of parts, known as "subassemblies". Tutorials were also added at this stage.Version 0.24, titled First Contract and released on 17 July 2014, added the contracts and reputation system to the game's career mode; however, players were still able to play career mode without these features in the new science mode. Contracts reward the player with currency and reputation. Funds can be used to purchase rocket parts, and reputation results in better and more lucrative contracts.
The final alpha release, 0.25, included a new economic system, and a major rework of aircraft components.
Beta
Version 0.90, nicknamed Beta Than Ever, was released on 15 December 2014. This was the only beta update for Kerbal Space Program. Featuring extensively rewritten code for the editor, it introduced the ability to sort parts by several characteristics and to assign parts to custom categories. Players could now offset parts, including into space. Career mode featured building upgrades; only the creation of small rockets with low mass and a part count is initially supported, but the player can upgrade each of the facilities to increase size limitations or unlock other capabilities.Release
Version 1.0 was the first full release of Kerbal Space Program. It was nicknamed We Have Liftoff! and released on 27 April 2015. Version 1.0 completely overhauled the flight and drag model for a more realistic simulation, now ignoring drag on rocket parts which were occluded from the air flow. It also allowed for body lift, so that parts that were not specifically designed as wings could still generate lift. 1.0 added shock heating and heat shields, making atmospheric entry much more dangerous, as well as air brakes and procedurally generated fairings. All parts received internal modeling. Resource mining was added to refine into fuel or monopropellant. 1.0 also brought several improvements to Kerbals, who could now have various specializations. For example, "Engineer" Kerbals can repair wheels and landing legs. Female Kerbals were also added to the game. Version 1.1, nicknamed Turbo Charged, was released on 19 April 2016, almost one year after the last major update. The game engine was upgraded from Unity 4 to Unity 5, resulting in a massive increase in performance, as well as a stable 64-bit client, removing memory constraints caused by too many mods being installed. Much of the game was rewritten to accomplish this.Squad released Version 1.2, nicknamed Loud And Clear, to upgrade the game from Unity 5 to 5.4 and introduce performance and minor gameplay improvements. The patch entered experimental testing on 6 September 2016 and was officially released on 11 October 2016. Its main new features include communication satellites, relay systems, and KerbNet. Several updates have been released since.
Other updates, Take-Two Interactive ownership
On 27 January 2014, it was revealed that Squad was working on an education-themed version of the game entitled KerbalEdu in collaboration with TeacherGaming LLC, creators of . It has since been released and includes 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.Squad has also made an Asteroid Mission Pack, with full support from NASA. Released on 1 April 2014, it is based on the real-life initiative to send humans out to study asteroids.
The majority of the game's music was provided by royalty-free composer Kevin MacLeod, with the rest of the soundtrack having been written by Squad's in-house composer Victor Machado. The game's main theme was composed by lead designer Felipe Falanghe and arranged by Machado.
On 5 June 2015, it was announced that Kerbal Space Program was being ported to the PlayStation 4 by Flying Tiger Entertainment. In August 2015, it was announced that Xbox One and Wii U ports were also in development by Flying Tiger Entertainment.
The game has since been released on the PlayStation 4 and Xbox One, but Squad has been quiet regarding the announced Wii U port. In January 2017, one of Squad's developers had finally broke the silence on the official forums, and admitted that despite initial enthusiasm to release the game on the Wii U, they claimed that various "external factors" has forced them to reevaluate supporting the console. They added that additional details will be announced at a later date.
On 17 March 2017, Squad announced a full expansion for the game; called Making History, it would be paid and contain new features. These new features included Mission Builder, which would allow players to create and edit their missions that players could complete by launching and operating various rockets and ships in the game, and History Pack, which would provide designed missions simulating important historical space endeavors that have been completed in real life. Squad announced on 7 February 2018 that the expansion would be released on 13 March 2018. The expansion contains many parts inspired by those used in various rockets such as the Soyuz spacecraft and the Saturn V.
Squad announced in May 2017 that Kerbal Space Program has been acquired by publisher Take-Two Interactive; this acquisition does not affect Squad's development or plans for the game and early backers will still get free DLC, and with Take-Two's help as a publisher, better support Kerbal Space Program on consoles to keep those versions to-date alongside the personal computer ones. Kerbal Space Program will be one of the first titles published under Take-Two Interactives's 2017-launched Private Division, a publishing label aimed to support mid-sized development studios.
In late May 2019, Squad released the Breaking Ground expansion, which includes servos, pistons, redesigned space suits, and experiments which can be deployed to earn science over time.
Reception
The public alpha and beta releases were well-received. Many publications have spoken positively of the game, praising its replay value and creative aspects, including Kotaku, Rock, Paper, Shotgun, IGN, GameSpy, Eurogamer, Polygon, and Destructoid.In May 2015, PC Gamer awarded Kerbal Space Program 1.0 a score of 96 out of 100, their highest review score of 2015. They praised the "perfect blend of science and slapstick", as well as the sense of accomplishment felt upon reaching other planets and completing goals. IGN has praised Kerbal Space Program ability to create fun out of failure, saying that "By the time I finally built a rocket that achieved successful orbit, I had failed so many times that in almost any other game I would have given up completely."
In their review, Edge thought that "The magic of Kerbal Space Program is not just that it manages to be both a game and a simulation, a high-level educational tool and something that is fun to simply sit and tinker with. It's that, in combination, these qualities allow for a connection with real history and real human achievement... Its ultimate promise to the player is not that you'll crack a puzzle that has been set by a designer, but that you'll crack a puzzle set by reality."
Commercial
In the hours after its Steam early access release on 20 March 2013, Kerbal Space Program was one of the platform's top 5 best-selling games, as well as the best seller on Steam for Linux.Squad has released physical merchandise such as clothing and plush toys. In March 2015, Squad and 3D printing service Eucl3D announced a partnership that would allow players to order 3D printed models of their craft.