Orbiter

Orbiter is a freeware space flight simulator program developed to allow users to operate simulated spacecraft using a detailed and realistic flight model. The developer, Martin Schweiger, felt that space flight simulators at the time were lacking in realistic physics based flight models and decided to write a simulator that made learning physics concepts enjoyable.

The simulator was first released on 27 November 2000 and several new versions have been released, with the most recent version 100830 released for free download on 30 August 2010.

Orbiter has now been used as a teaching aid in classrooms, and a large community of addon developers have created a multitude of addons to allow users to fly assorted real and fictional spacecraft and adding new planets or solar systems.

About the simulator
Orbiter allows users to explore the solar system on a number of spacecraft: both realistic, such as the Space Shuttle Atlantis; and fictional, such as the "Delta-Glider." The developer Martin Schweiger has included fictional spacecraft to allow for easier flights for less experienced users.

The simulator is realistic enough to re-enact historical space flights, however the ability to fly fictional ships allows the player to reach areas of the solar system that cannot be reached by manned spaceflight at the present time. A spacecraft's engines are defined only by the amount of thrust they put out and amount of fuel they use, allowing anything from solar sails to conventional rocket engines to futuristic nuclear fission and fusion drives to be simulated. Orbital, sub-orbital, and interplanetary travel are all supported. Docking and attachment systems allow the user to simulate docking with a space station or other spacecraft and rendezvous with and retrieval of satellite. The user can also attempt to build a space station in orbit.

The solar system presented in Orbiter consists of the sun, the eight planets and their major moons. Dwarf planets, asteroids, and comets are not included in the solar system included with the simulator but exist as add-ons. Although Orbiter contains a database of over 100,000 stars, these are for display purposes only and interstellar travel is currently not possible in the simulator. The simulator also includes a planetarium mode that allows ecliptic and celestial grids to be overlaid onto the star map, along with labels of the constellations and other celestial markers. The planetarium mode can also display labels indicating the location and identity of objects in the solar system, such as planets, moons, or vessels, that appear within a certain proximity based on their type. This mode can also display labels on the celestial bodies in the solar system at certain coordinates on their surface for indicating cities, historical markers, geological formations, and other interesting sites.

Orbiter was developed as a realistic simulator, with accurately modeled Planetary motion, gravitation effects, free space and atmospheric flight. The position of the planets in the solar system is calculated by the VSOP87 solution, the Earth-Moon system is simulated by the ELP2000 model.

The traditional simulated control interface in Orbiter consists of two Multi-function displays and a Head-Up Display. Each features several modes of operation, with all commands given via the keyboard or mouse. The simulator also supports customized control panels and instruments, including 3D virtual cockpits and 2D instrument panels. These allow the player to use the mouse to interact with the panels, and allows more complex systems and instruments that are customized for each ship. The addition of a virtual cockpit also allows the player to freely look around from the perspective of the pilot. From patch 060929 onwards, Orbiter has supported TrackIR, which allows the simulator to track the head-movements of the player and adjust the view accordingly.

The default version of Orbiter has no sound, however a popular add-on called "OrbiterSound" is available. It provides engine noises, ambient sounds in the cabin, radio chatter and other sounds including mp3 playlists. Options enable the user to maintain a realistic silence when the craft is viewed externally during space flight.

Included spacecraft
Orbiter's standard distribution includes real and fictional spacecraft and space stations:

Real vessels

 * Space Shuttle Atlantis: The Orbiter version of a Space Shuttle. It lacks the guidance systems and autopilots of the real Space Shuttle, which makes it one of the hardest spacecrafts to fly in Orbiter But nowadays, on the latest version of Orbiter, it now has a guidance system and a launch autopilot, making the Atlantis not as hard to fly as before. To make it a bit easier, the flight model has more propellant than the real Space Shuttle and its engines are a bit more effective.
 * Space Station Mir: Orbiter's model of the historic Russian space station. Unlike its real counterpart, it was not deorbited and is placed in an orbit which is closer to the ecliptic plane. This was done initially to make Mir a good origin of interplanetary flights in earlier versions of Orbiter, when Orbiter also automatically refueled spacecraft on docking with a space station. Using the scenario editor, it's still possible to refuel in-flight or start the simulation docked and with full tanks.
 * International Space Station: In a similar orbit as the real ISS and in a completed state, it shows modules which are no longer planned to be installed on the real ISS.
 * Hubble Space Telescope: A model of the real HST, it gets used together with Orbiter's Space Shuttle Atlantis.
 * Long Duration Exposure Facility Satellite: Like the Hubble Space Telescope, it's one of the example payloads for Orbiter's Space Shuttle.

Fictional vessels

 * Delta-glider Mk.4: A delta wing spaceplane, which is rather easy to fly and thus good for the first steps into Orbiter. A variant of the Delta-glider Mk.4 is also included, the Delta-glider-S, which trades some of the propellant capacity for a scramjet propulsion system. It's possible to travel from Earth to Mars with the Delta-glider, making it possible to practice interplanetary missions. It is technically a single stage to orbit spaceplane.
 * Shuttle-A: A small space freighter, which can transport six large cargo containers with a total mass of 120 metric tons. It doesn't have an aerodynamic hull so it is at home on the Moon and Mars. Its cargo containers are equipped with automatic parachutes. Using the parachutes, it's possible to simulate a cargo run from a lunar base to Earth and back, dropping the cargo while still in the upper atmosphere. Its high inertia and inferior aerodynamics make it harder to fly than the Delta-glider.
 * Shuttle-PB: A small personal spacecraft, with high agility and a futuristic performance. As its main purpose is to serve as simple SDK example for add-on developers, it lacks many complex details of other included ships in Orbiter like 2D or 3D cockpits or animations.
 * Dragonfly: A complex manned space tug for the construction of space stations. It simulates its various subsystems at a higher complexity than all other standard spacecraft in Orbiter, being a good example of the technical possibilities of Orbiter's SDK. Its flight model is also within the possibilities of current technology, making it a so-called "nearly realistic" spacecraft.
 * Lunar Wheel station: A fictional wheel shaped station in lunar orbit, inspired by Space Station V from the beginning of 2001: A Space Odyssey.. As a rotating space station, it is a challenge to dock with it.
 * Carina: A small fictional science satellite, which is used as payload on Orbiter's Space Shuttle. It is a completely inert payload currently. It is based on a proposed European reentry capsule experiment, to be launched on the Ariane 4, which later resulted in the ARD.

Orbiter add-ons
While the source is not editable, an extensive API enables Orbiter users to contribute by creating add-ons. Many spacecraft are available for download as add-ons, ranging from the Soviet Vostok spacecraft to Project Mercury and the Apollo program. Another popular category of add-ons are modifications of the standard spacecraft of Orbiter, ranging from simple visual changes to complex simulations of the internal subsystems of these fictional crafts. Examples of these more advanced default spacecraft include the DeltaGlider IV and the XR Series of vessels.

Add-ons are also available for new bases, MFD modes, extensions of the simulation menu, space stations, planets, and even other solar systems. Since Orbiter 2006, a scenario editor is included, which can also be extended for supporting the special attributes of add-on vessels.

Manuals and Technical Papers

 * Orbiter: Manual - current manual for Orbiter
 * Orbiter: A Free Spacecraft Simulation Tool (.PDF) (.PPT) - general presentation of Orbiter presented by the author at the 2nd ESA Workshop on Astrodynamics Tools and Techniques at the ESTEC
 * Spacecraft simulation and visualisation with Orbiter 2006 (.PDF) (12 MB PPT) - Presentation of the recent technical developments in Orbiter, held by the author at the 3rd International Workshop on Astrodynamics Tools and Techniques at the ESTEC.
 * Paton, M (2007),, presented at the International Space Development Conference (ISDC) 2007 in Dallas

Reviews

 * Review: Orbiter space flight simulator on The Space Review