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For the species of Kerbin, see Kerbal.
Kerbonaut with helmet removed (promo image)

A kerbonaut is a Kerbal that has been trained as an astronaut. Kerbonauts are capable of operating assorted vehicles, can perform science experiments, and have a limited ability to perform repairs.

The term kerbonaut is a fan-made term that was created by replacing the root astro- or cosmo- from astronaut or cosmonaut with kerbo-, and is not seen in-game; rather, they are referred to as astronauts; however, the Experiment Storage Unit's description uses the term "kerbalnaut", and Harvester used the term kerbonaut in a developer's note.[1] The commonality of its use by fans mirrors the real-world prevalence of nation-specific terms for space travelers.


A kerbonaut on EVA
Bob Kerman on EVA


Kerbonauts can be directly controlled when on EVA, where they wear a spacesuit and can collect EVA reports and surface samples. In versions prior to 1.11, the spacesuit includes an RCS jetpack, which allows tri-axial maneuvering while in space, and flight on planets with low gravity; starting from version 1.11, the jetpack is a separate inventory item equipped on all Kerbonauts by default. Unequipping the jetpack visually removes it from the Kerbonaut's back as well.

Kerbonauts on EVA can be killed by hitting objects or the ground at a high velocity.[2]. Milder impacts and ground contact with a non-negligible horizontal speed cause the Kerbonaut to ragdoll and become uncontrollable; in space, the Kerbonaut quickly regains control after about a second but under gravity, ragdolled Kerbonauts cannot get back up until they come to a complete halt and if they fall over on a slope, they will often continue to helplessly roll downhill until they accelerate to lethal impact speed and die.

Starting from version 1.5, level 1 Kerbonaut (or level 0 pilots) can use a personal parachute]] to land safely by themselves on atmospheric bodies. From version 1.11, the parachute is an inventory item equipped on every Kerbonaut by default.

Starting from version 1.6, Kerbonauts can remove their helmets and neck rings on planets with a breathable atmosphere although by doing so, they become more susceptible to damage from impacts and can die if the external air pressure drops too low from high altitude. In addition, helmetless Kerbonauts on EVA or in an EAS-1 External Command Seat have extremely low heat tolerance to the point where standing in the immediate vicinity of the blast of any engine that produces significant heat (most often rocket engines) or being subjected to high aero forces from flying at supersonic speeds at low altitude will near-instantly kill them.

When inside of a crewable part, [3] kerbonauts can perform crew reports.

Kerbals with and without helmets

Experience and skill

→ Main article: Experience

Kerbonauts each have one of three specializations and can gain experience in them by going on missions. The skills include pilots, who can provide better SAS control, scientists, who can restore experiments and process additional science, and engineers, who can fix or restore certain parts and increase the efficiency of resource harvesters and converters.

Science container

Only scientists are able to operate science parts during an EVA but the data itself can be taken and carried by any Kerbonaut. Each Kerbonaut can only store one copy of the same experiment/biome/situation combination at a time and entering a command pod or other crewed part automatically transfers all stored data to the vessel unless the part in question is already storing a copy, in which case the duplicates must be discarded or stored elsewhere. The Kerbonauts can also collect surface samples (while landed or splashed down) and get an EVA Report by themselves, as well as use the EVA Experiment Kit if they have one in their inventory and their current situation (ie. not flying in atmosphere and not splashed down) permits it.


Starting from version 1.11, all Kerbonauts have 2 inventory slots with a maximum weight capacity of 65 kilograms and maximum volume of 40 liters. By default, every Kerbonaut carries an EVA Jetpack and an EVA Parachute and must unequip either before they can carry anything else. Note that although Kerbonauts can carry ship components like the 2HOT Thermometer, they cannot actually use these items from their inventory and unless the Kerbonaut is an engineer, cannot even drop the item on the ground, only transfer it to a part (or another Kerbonaut) with free inventory space.

Any items inside the Kerbonaut's inventory are added to the Kerbonaut's weight (or if the Kerbonaut is inside a vessel, to the vessel's weight) and are visually displayed on the Kerbonaut's back during EVA, with the jetpack and the parachute being added first (in this order) and any other equipped item displayed on top of those. A Kerbonaut with an empty inventory (no parachute, no jetpack) is able to jump slightly higher - in fact, they will actually jump so high that they can no longer land on their feet under Kerbin's gravity prior to version 1.11.1 and instead hit the ground hard enough to ragdoll.


The Astronaut Complex provides centralized status listing of all hired crew and the hiring of new Kerbonauts. The surname of every Kerbonaut, and of every known Kerbal, is "Kerman". Aside from the orange suits, each Kerbonaut has a random first name. Each Kerbonaut also has randomized personality traits.


Personality traits determine how a Kerbonaut behaves in various flight conditions. Each Kerbonaut has a random value of two personality attributes—Courage and Stupidity—that are displayed in-game. These traits affect the displayed facial expressions and gestures seen in IVA portraits and EVA, and range from delight to fear. These emotions have no effect on flight performance or Science results[outdated], and serve purely as flavor. There is a 10% chance they may also have the hidden "BadS" (an abbreviation of "badass") flag, which imposes total ignorance of both Courage and Stupidity and forces delight in nearly all situations excluding nearby explosions.

A scared Kerbonaut

There is a bug regarding Courage (but not Stupidity) in version 0.23.5, where courage values in the info screen in both the Tracking Station and Orbital Map are inverted from those displayed in the Astronaut Complex.

Experiments in version 0.23 using non-badass Kerbonauts modified to the four possible combinations of extreme Courage and Stupidity ([1, 1], [1, 0], [0, 0], [0, 1]) revealed that Courage does not control fearful behavior. Both of the Stupid Kerbonauts were blissfully ignorant in the face of danger. Meanwhile, the non-Stupid ones both displayed equal fear of accelerating in any rocket built by KSC engineers, and displayed this at exactly the same time despite having opposite levels of Courage from each other. Subsequent tests with 0.75/0.25 combinations showed an uptick in fear in the less Stupid subjects, indicating that the natural outcome of awareness is dread.

However, observing the behavior of tourists (during the crash runs to Mun, for example) have generated the result: At Kerbin (inside atmosphere, around KSC), those with low stupidity tend to show more fear. However, once they reached a certain altitude (or distance to KSP), their mood (behavior) quickly switched to "content", and are all "excited" when in space (including landed on airless bodies like the Mun). However, regardless of that, all Kerbonauts display fear toward explosions, even if it was caused by jettisoned parts. (tested in version 1.10.1)

The badS flag, however, negates all fear regardless of Courage or Stupidity, pushing the Kerbonaut toward a happy state which only the most blatantly impending catastrophe can dim.

"Orange Suited Kerbonauts"

Every new game begins with four Kerbonauts on the roster in the following order; Jebediah Kerman, Bill Kerman, Bob Kerman, and Valentina Kerman. While all other Kerbonauts have randomly generated names and stats, these four remain persistent through all save games. Their presence at the top of the list means that, when available, they have a much greater likelihood of being aboard any given vessel than any other Kerbonaut.

These are the only “veteran” Kerbonauts in Kerbal Space Program, designated by orange IVA suits and icons in crew interfaces; everything else is visually identical to all Kerbonauts. In some of the game's loading screens, three orange suited Kerbonauts (presumably Jeb, Bill, and Bob) have helmets with orange stripes though no such helmet is seen in-game – IVA helmets have grey stripes and EVA have red.

They are, arguably, the "faces" of Kerbal Space Program.


The term kerbonaut is a fan-made term and is not used in-game. The in-game building for hiring crew is named the Astronaut Complex and is presumably the official term, with only one known instance of a developer using Kerbonaut[1], and the Experiment Storage Unit referring to them as Kerbalnauts.

The commonality of the term kerbonaut by fans mirrors the real-world prevalence of nation-specific terms for space travelers. For example, "astronaut" and "cosmonaut" refer principally to American and Russian space travelers, respectively.

  1. 1.0 1.1 March 31st, 2015 Devnotes.
  2. The true crash tolerance remains unknown, as different parts of the spacesuit have different impact velocities; a bug exists where Kerbonauts can survive impossibly large falls by landing on their helmet, while the same fall would kill a Kerbonaut who landed on its feet
  3. Jebediah, Bill, Bob, and Valentina wear a special orange jumpsuit. All other Kerbonauts have white.