Type: Versatile SSTO vehicle.
Original manufacturer: Multiple.
Current pattern status: Public domain.
Propulsion: Wide variety of chemical rocket drives or auxiliary non-rocket engines.
Armament: None by default, may carry a wide variety of weapons.
FTL capable: no.
Length: 50 meters.
Payload: 100 to 250 tons, depending on propulsion/refueling options.
Crew: Up to 6.
Passengers: Variable depending on configuration.
Also known as the OSO, the One-Ship Wonder.

The Open Source Orbiter is a great example of what the open-source economy of the space age can produce when given a very adaptable platform, lots of time and a plethora of problems to solve.

The OSO was born in the late years of the interplanetary age and first appeared as a concept, a speculative blueprint posted by an anonymous user on a communal forum. This blueprint drew inspiration from late industrial age vessels as well as modern orbiters to create something that, albeit not technically new, had not really been attempted before: an SSTO vehicle for the masses. The Public Orbiter, as it was known at the time, had nothing of a cutting edge marvel. It was a clever amalgamation of well-developed technologies that aimed at creating a rugged, robust, cheap and adaptable vehicle that wouldn't try to suit the need of a specific commune but could potentially be adapted for any mission in planetary orbit. The idea was received with interest by the aerospace community, then gained its focused attention when various community-fueled improvements turned it into what was to become the Open Source Orbiter.

At its core, the OSO is a VTOL single-stage-to-orbit vessel. What sets it apart from other similar designs and has ensured its longevity is the fact that every single one of its components has been selected and engineered to ensure the lowest possible cost. The OSO can use almost any type of propellant and fuel thanks to the use of universal tanks, its heat tiles are fast to replace and repair, its spare parts are ridiculously easy to source and its cargo bay can carry almost anything, with a clever system of joints and standardized containers allowing for on-the-fly module swapping. Granted, the OSO isn't as powerful as modern orbiters, nor is it as durable as dedicated deep-space vessels, and it certainly lacks the power to make it a true interplanetary freighter, but it's cheap. It's not just cheap in a monetary sense, it's also politically and socially cheap. Given that its blueprint is in the public domain, building the OSO or one of its numerous variants comes at no influence cost, even for a very small, isolated commune. 

Speaking of variants, there is one for about every single case use one can think of. This is emphatically not a metaphor. Drone OSO used as a detachable fuel tank/cargo container? Of course. OSO updated with a nuclear thermal engine for an interplanetary trip? Just give me some radiators and we're good to go. Hastily weaponized OSO used as a "Karman skimmer" vehicle? Illegal, but very much doable. Exploration OSO with reinforced landing gear? Come on. FTL-capable OSO? With a computing station and a fission stage, I will bring that thing to Tau Ceti and back. Two-staged OSO for take-off under high gravity conditions? Hot staging is my passion. Of course, it is also very common to find OSO hulls being used as waystation parts, given the durability of the vessel.

A recent study estimated that as many as 65% of all non-FTL vessels in human space were Open Source Orbiters or derivatives thereof.

Illustration: SpaceX Creative Commons.