Kerbal X

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Kerbal X on the Launch Pad (1.7)

The Kerbal X is a stock rocket available to all players in sandbox mode. It is a reliable, all-around ship capable of reaching orbit fairly easily and thus is a good way for new players who have issues building their own ships to make it into orbit. It has a total mass of 130.94 t and has 74 parts with the launch clamps. It has no RCS capabilities. Between 0.21 and 0.25, it had SAS capability, but 0.90's change to SAS (to make it dependent on pilot skill) means it doesn't have SAS anymore.

Craft Description

The Kerbal X is one of the most successful rockets that can be ordered from a catalog. Despite the original design having been meant for a plastic model, it's proved itself quite dependable as a full-sized craft.
The X is capable of achieving orbit around Kerbin, and even features a very optimistic set of landing legs on its upper stage.



Kerbal X after dropping all boosters and shortly before advancing to stage 2

The first stage is comprised of three Rockomax X200-32 Fuel Tanks and a Rockomax "Mainsail" Liquid Engine. Also, six liquid fuel boosters are staged in an Asparagus design. It has aerodynamic surfaces and a strong structure. The first stage is easily capable of launching the second stage into a suborbital trajectory, with a good horizontal speed at around 90 km, thus making it easy for the second stage to make orbit. However, skilled players may be able to push the second stage of the spacecraft into low orbit without completely expending the first stage. The full stage with all of its boosters has 2700 kN of thrust, for a thrust-to-weight ratio (TWR) of 2.102. The sole Mainsail and relative fuel tank has a TWR of 1.995 (the total mass of the Kerbal X at that time is 76.64 t).

The upper stage is a large diameter Rockomax X200-16 Fuel Tank plus a Rockomax "Poodle" Liquid Engine, and the final re-entry stage consists of only a Mk1-2 Command Pod with a Mk16-XL Parachute. As the upper stage also has landing legs (LT-2 Landing Struts to be specific) and a ladder, and it is hinted by the menu screen where a wreckage similar to the Kerbal X can sometimes be seen, one can deduce that it was intended to land on the Mun. It is capable of doing so, but it barely has enough fuel to get the crew back home.


The Kerbal X in a 150 km orbit around Kerbin

The first stage's central engine and relative fuel tank has 2973 m/s of Δv, not mentioning the radial ring of boosters which has 1063 m/s. This sums up to about 4036 m/s, enough to make orbit (3500 m/s) with some to spare, making the Kerbal X launch vehicle a suitable option for orbiting small-to-medium payloads. The maximum payload to Kerbin low orbit of the unmodified Kerbal X launch vehicle is slightly less than 24 tons.

The second stage has 2392 m/s Δv, and the total Δv is 6428 m/s. This total impulse is sufficient for landing on the Mun with the piloting skill of the average player, but not for returning to Kerbin afterwards. This is probably intentional: the purpose of the Kerbal X is to present a new player with a flyable and somewhat capable rocket design, that nevertheless needs some improvement in order to be fully successful. However, skilled players have demonstrated that the design as-is will conduct a round-trip Mun-landing mission. The Kerbal X is also capable of going into interplanetary orbit, able to land on Eve or Duna (or their moons, in which case landing and returning is also possible with careful planning) or fly by any other body.

As the usage of electric charge increased in version 0.21 because reaction wheels now require it, the second stage is now equipped with two OX-STAT Photovoltaic Panels.

6× Booster Stage 1 Stage 2 Stage 3
Engine LV-T45 Liquid Fuel Engine Rockomax "Mainsail" Liquid Engine Rockomax "Poodle" Liquid Engine none
Diameter Small Large Large Large
Mass (t) 9.05 60.52 11.70 4.42
Burn time (s) 13.7, 29.7 (+16), 49.8 (+16, +19.8) [Note 1][Note 2] 97.3 [Note 2] 109.8 0
Δv (m/s, vac) 1063 2973 2392 0
  1. After dropping one booster pair the next one fed all engines except the previous (dropped) two engines causing a longer burn time.
  2. 2.0 2.1 All engines of the booster and first stage ignite at the same time.


Action Δv (m/s) Feasible
Orbit 3500 Yes
Munar injection and capture 1170 Yes
Mun landing 580 Yes
Mun surface orbit 580 Yes
Mun orbit return 310 Yes
Minmus injection and capture 1090 Yes
Minmus landing 300 Yes
Solar orbit injection 950 Yes
Interplanetary travel 90+ Yes

The ability of the Kerbal X to reach orbit with a relatively small rocket for a medium payload (24 t) is significant in its reliability as bigger rockets tends to be more prone to exploding randomly or being unsuited for space travel. The two-stage to orbit rarely leaves any debris (the Mainsail first stage, if the ascent profile was efficient, may remain in Kerbin orbit), and is quite cost effective in career mode, though a rocket with solid boosters could do the same job at a lower price.

The Kerbal X is also suited to place payloads in a synchronous orbit around Kerbin as it has the required Δv to do so and deorbit thereafter.

With the help of gravitational assists it is possible to reach other planets or moons without changing the configuration.


An interesting use of the Kerbal X, with added RCS and a docking port, is a space station crew transfer vehicle, allowing crew transfers or module delivery and docking as the ship has a good margin of additional weight it can carry to LKO. If placed properly, the RCS thrusters assure an easy docking and the low chance of failure justifies the uses of the Kerbal X as a crew transfer ship. To fully make the X into a crew transfer vehicle, one should remove any lander-related parts, such as the legs and ladders.

For the docking port, one should use radial parachutes to make room for a Clamp-o-Tron docking port (it is not advised to use the Shielded version in order to make room for a Launch Escape System).

Another upgrade is to replace the LV-T45s with LV-T30s because it allows an additional payload of 1.5 tons from the reduced mass of the T30s (0.25t more payload per engine replaced).

Spoiler: Easter egg
In the scenario Station One, there is a spacecraft named Kerbal XX in orbit around Duna. It is similar in design to the Kerbal X but it only has the upper stage and it has a LV-N "Nerv" Atomic Rocket Motor instead of a Rockomax RE-L 10 Poodle Engine. It is completely flyable.