-- from Space Systems Directory, 2148

The GILGAMESH class of local space transports were among Burchismo Aerospace's main contributions to the establishment of a vital, robust extraterrestrial infrasture in the decades after the middle of the 21st century. The original three ships -- GILGAMESH, PROMETHEUS and DAEDALUS, were built in the mid-2030s in components at BA's main fabrication facility at Amazonia and lofted with the BSP for final asssembly to the LEO station that eventually became Celestium. Later vessels built on the general GILGAMESH plan were fabricated in whole or part in Earth, Lunar or Martian orbit. By 2075, there were a total of 15 vessels based on the same design in service in cislunar, Martian and various Belt trade routes. The original three remain in service today, having changed ownership and operation many times in their early years and having undergone some modifications along the way.

GENERAL DESIGN & STRUCTRE. The basic design concept behind the GILGAMESH class was the development of minimal structure and systems required to transport a single standard-sized station or logistics module in the cislunar energy regime. The dimensions and "clamshell" opening of the central framework of the vessel were defined by this requirement, and additional spars extend fore and aft from this main structure, around which the vessel's systems are laid out in a mainly radial/axial fashion centered on the z-axis line. A key element of the central framework is its double function: As well as serving as payload acommodation and the primary structural foundation of the ship, it also acts as a thermal radiation system. Coolant is pumped through channels formed into the diamond-phase carbon structure of the main framework spars to radiate heat from the engine reactors and other ship systems to regulate vessel temperature.

MAIN ENGINES. The original three and almost all subsequent GILGAMESH class vessels are powered by four Burchismo Atomics LA 110 LANTR motors or their later derivatives. These Lox-Augmented Nuclear Thermal Rocket engines are "bi-modal" -- operating as standard nuclear-thermal rockets and also, with liquid oxygen injection downstream of the nozzle throat, as H2/LOX combustion engines. The engines, each with its own small nuclear reactor core, mate into a main thrust structure, which also holds the propulsion and electrical generation system's main and cross-feed pumps and associated plumbing.

FUEL/OX TANKS. Two large double-walled liquid hydrogen and two smaller liquid oxygen tanks are situated just forward of the engines and thrust structure, and are integrated with the main frame via structural spars that run along their sides. As originally constructed and operated, GILGAMESH was not equipped with additional thermal covering for these tanks. For clarity, this is the configuration depicted in the general arrangement diagram above. However, it was discovered that the addition of further protection from fuel and oxidizer thermal degradation was desirable and octagonal cross-section covers were added on the next two and all subsequent ships in the class from their original construction. GILGAMESH itself was eventually retro-fitted with the same kind of thermal tank covers in the 2080s as activity in cislunar space began to return to normal.

RCS. Eight Reaction Control System quads are structurally connected to extensions of the main framework and main engine thrust structure, four forward and four aft. Fuel, oxidizer and pumps for the hypergolic RCS system are contained in four tank assemblies that are connected to the RCS quad support structures. Plumbing for RCS primary and cross-feed is incorporated into the main and secondary structural framing elements. The modular RCS quads are situated well off the vessel centerline to increase rotational leverage, minimize RCS thruster impact on other vessel components and to ease servicing.

CMA. The fore and aft sections of the vessel are joined by the Central Mating Assembly (CMA), which consists of extensible, nesting docking tubes that retract fully for loading and unloading payload, extend partially to mate with pressurized payload modules, or extend fully to mate with each other, providing full internal passage from one end of the ship to the other. The forward docking port also retracts in a nested fashion to provide enhanced visibility from the flight deck. This design element was included because the basic structure of the GILGAMESH class is shared with surface lander vehicles in the LSTS family, where downward visibility is a key requirement.

CORE MODULES. The central pressurized section of the ship is separated into two Core Modules, one forward and one aft of the main structural framework. The Core Modules provide structural support for the elements of the CMA and other modules, and also contain ducting carrying wiring and plumbing for ship systems in their walls and on their external surfaces.

MISSION MODULES. Equipment for main ship systems, such as life support, power management, communications and data management, and for specialized applications, are housed in as many as six Mission Modules, which are affixed to the Core Modules. There are connecting points for up to four Class C Mission Modules on the forward Core Module and two Class B Mission Modules on the aft Core Module. This system allows the GILGAMESH ships to be quickly and easily reconfigured for different kinds of service, and speeds normal and unexpected maintenance. Mission Modules are often swapped out during regular port operations, allowing faster turn-around and more economical operation. It also allows vessel operators to optimize their servicing costs, by taking advantage of market competition among specialty service and equipment manufacturers and suppliers who conform to the basic MMA2036xx industry standards.

CREW MODULES. In itheir most common configuration, the GILGAMESH class transports have a crew of two [discussed more fully below]. Each crew member has a personal stateroom module, one port and one starboard on the forward end of the forward Core Module. The Crew Utility Module is situated on the bottom of the forward end of the fore Core Module. The Crew Utility module combines galley and toilet functions (but not usually at the same time). When employed as a passenger transport, passenger accommodations are self-contained within the passenger payload module.

EVA. Extra-Vehicular Activity is an uncommon occurrence in normal operation of the Gilgamesh vessels. When devoted to work that requires regular EV activity, a crew lock mission module is typically fitted to the ship for that purpose. However, extraordinary EVA capabilities are possible and have been carried out by using one of the core modules as an airlock. This is considered off-nominal operation of the vessels, though, because it requires isolating at least part of the pressurized central passageway from other habitable parts of the ship, and is avoided whenever possible.

-- from Solar System Commerce, 2148

The GILGAMESH class transports have been one of the primary utility vehicles in translunar and other local space environments for over 100 years. The simplicity and modularity of their design has led to them being employed in both liner-style regular service and special charter operations.

In the Earth-Moon service in which they were most commonly found in the first period of their operation (and are still very active today), the GILGAMESH ships worked on regular transits between Earth LEO stations and stations in Lunar orbit. Designed to have enough delta-v for a plane change from equatorial orbit and a one-way trip with a safe margin, the GILGAMESH ships were intended from their inception to be refueled at each end of the Earth-moon transit. The energy budget of these ships is split roughly between 50% delta-v for a LEO change to the moon's orbital plane, and the remaining delta-v being split roughly 2/3 for trans-lunar injection, course corrections and lunar orbit insertion burns, and 1/3 for a safety margin.

Although highly automated, the vessels usually operate with a crew compliment of two persons or their equivalents. Operators typically staff this crew requirement with six people, rotating three crews on a regular basis because on-board crew accommodations are relatively small. For instance, TranSpace, operator of the first three vessels in this class in regular cislunar trade since the mid-2060s, usually maintain a total flight crew staff of 18 qualified pilots. These rotate on a 6-week schedule that runs with two weeks of flight duty, two weeks of ground leave and two weeks of orbital support work. Ground leave is taken either Earth-side or on Luna, while orbital support is carried out at TranSpace's equatorial LEO base at Clarke Station. The orbital support crew engages in on-orbit logistical work, including arranging for and supporting the swapping out of Mission Modules, bunkering and chandlering, and generally serves the traditional function of ship's agents and port captain. They also act as back-up flight crew.

Over time, the business of passenger service has tended to become focused on passenger booking and accommodation, so that at this point all passenger service in cislunar space, for instance, is carried out as a specialized business distinct from vessel operations. Passenger modules have come to be owned, maintained and operated by specialized enterprises. Some of these businesses provide passenger service crews with these modules, whose accommodation is housed in the passenger module, while others contract with vessel operators for varying levels of personal passenger service. Thus, depending on the voyage, crew members of the GILGAMESH class ships may find themselves occasionally acting as stewards, cooks, or in other passenger service capacities. Regular travellers between Earth and Luna have come to realize that such work is unpopular with flight crews on these ships and make their travel choices accordingly: Personal service comes at a price, and travellers on a budget have learned to look after themselves on the three to four day trip.

In the economic and social disruptions following the Lunar Jihad of 2073 and the Belt Crash of 2075, a few of the GILGAMESH class ships that had been built in or moved to Mars local space or beyond came into the hands of financially marginal owners and operators. In some cases, the activities of these ships seemed to differ little from the traditional definition of tramps or even, in a few notable instances, piracy. Some of these ships became true "live-aboards" for the people invovled, and the originally relatively spartan accommodations intended for short-haul service were modified in some ingenious ways. This subject is dealt with elsewhere, and deserves closer study than has been devoted to it to date.

This addon is based on Vinka's Spacecraft3.dll, which you must download and install before running any of the included scenarios. The addon utlizes some textures also included in other Burchismo addons, and are safe to overwrite. Scenarios require download of the Space Station Building Blocks 4.1 addon.

Three vessels are included in this addon: GILGAMESH, PROMETHEUS and DAEDALUS. Two versions of the GILGAMESH vessel are included, one with and one without crew figures. These three vessels are listed in the desending order of their mesh size, with the crewed GILGAMESH being the largest mesh, and the DAEDALUS being the smallest mesh.

Being solely an exo-atmospheric vehicle, navigation and control of the GILGAMESH vessels is fairly standard within the Orbiter simulator, so only a key map is provided here for user guidance:

Note that scenarios involving full payload operations begin with the payload module (LTM01) docked to a nearby station node module. Grapple the payload module with the station arm and then, after moving it away from the docking port to which it was attached, switch (F3) to the payload module and undock it (Ctrl-D). This is an important step: If you do not undock the payload module manually, when you release it near the transport vessel's attachment point, it will return to its previous, docked position.

After grappling the payload with the GILGAMESH vessel's single, central attachment point, you may note some misallignment that is "inherited" from whatever orientation the payload module had when it was released by the transferring arm. Saving the scenario and restarting it (always a good idea when successfully completing some segment of complex Orbiter operations, anyway) will cure this problem.

Also note that this addon does not include a target lunar orbit station. This will be implemented in later LSTS 2.0 releases.

The first set of GILGAMESH vessels is part of my continuing effort to go back and retrace the steps in my "future history" series of addons that attempts to set out one pathway through the possible development of space technology, and the society that might travel that path, in the 21st century and beyond. In the process of recreating the original series of addons to more closely match "standard Orbiter scale," I've been able to incorporate the modest improvements in my modeling skills that have come with slowly learning more and more about how to turn my dreams into at least simulated reality, and also to address things about the basic designs in the original series with which I was never really very happy.

I chose to start the recreation of the LSTS vessels with the cislunar transport because that was the element of the original series with which I was least satisfied. In hindsight, I realize that the first design I did for this piece of the system was really an afterthough, after I had lavished attention on the series of landers. So I started with a clean monitor and a standard "Building Blocks" hab module and worked outward from there, just as the systems are desribed in the documentation above. As it turns out, the design work I've done here will provide the modular foundation for much more of the "re-imagineering" of my addons, as I continue to work back to where I was ... and then beyond.

As always, I express my deepest gratitude to Dr. Schweiger for providing us with such a wonderful playground in space, and the many bright and helpful people of the Orbiter community who provide us with tools, help and encouragement along the way. I welcome feedback in the release thread on the Orbiter forum. Happy sailing!

--- Greg Burch

June, 2008