Critical to the flight of any vehicle through interstellar space are the concepts of guidance and navigation. These involve the ability to control spacecraft motions, to determine the locations of specific points in three and four dimensions, and to allow the spacecraft to follow safe paths between those points.
The theater of operation for the USS Odyssey takes it through both known and unknown regions of the Milky Way galaxy. While the problems of interstellar navigation have
been well-defined for over a hundred years, navigating about this celestial whirlpool, especially at warp velocities, still requires the precise orchestration of computers, sensors, active high-energy deflecting devices, and crew decision-making abilities.
The whole of the galactic environment must be taken into account in any discussion of guidance and navigation. The Milky Way galaxy, with its populations of stars, gas and dust concentrations, and numerous other exotic (and energetic) phenomena, encompasses a vast amount of low-density space through which Federation vessels travel. The continuing mission segments of the USS Odyssey will take it to various objects within this space, made possible by the onboard navigation systems.
The attitude and translational control of the USS Odyssey relative to the surrounding space involves numerous systems. As the starship maneuvers within the volume of the galaxy, the main computers attempt to calculate the location of the spacecraft to a precision of 10 kilometers at sublight, and 100 kilometers during warp flight. The subject of velocity is important in these discussions, as different sensing and computation methods are employed for each flight regime.
During extremely slow in-system maneuvering at sublight velocity, the main computers, coupled with the reaction control thrusters, are capable of resolving spacecraft motions to 0.05 seconds of arc in axial rotation, and 0.5 meters of single impulse translation. During terminal docking maneuvers, accuracies of up to 2.75 cm can be maintained. Changes in spacecraft direction of flight, relative to its own center of mass, is measured in bearings, as shown in the diagramme above. Internal sensing devices such as accelerometers, optical gyros, and velocity vector processors, are grouped within the inertial baseline input system, or IBIS. The IBIS is in realtime contact with the structural integrity field and inertial damping systems, which provide compensating factors to adjust apparent internal sensor values, allowing them to be compared with externally derived readings. The IBIS also provides a continuous feedback loop used by the reaction control system to verify propulsion inputs.
The Navgator's responsibilities are three-fold.
- First: To calculate and update the ship's present position with regards to velocity and maneuvers.
- Second: To locate the coordinates of the Captain's designated destination, using the ship's Navigational Computer. Third: To calculate the best course from the origin coordinates to the destination coordinates, allowing for intervening Neutral Zones and catalogued hazards to navigation. The final course, a nearly-straight line (spline) which curves to avoid hazards, is then transferred into the Console's Course Preset Panel.
The Helmsman's responsibilities are four-fold.
First: To execute any courses stored in the Course Preset Memory Bank - as ordered by the Captain and at the velocity designated by the Captain.
Second: To monitor the ship's progress along its course, alerting the Captain to any uncharted objects or hazards, and to override the existing course as directed so as to either avoid said hazard or stop for investigation.
Third: To manuœvre the vessel on manual control for such purposes as evasive maneuvers. intercept courses, and orbital insertions.
Fourth: To act as the auxiliary Weapon's Officer wherever the Bridge Tactical Console is unmanned using the Helm Console Fire-Control Panel.
As shown in the preceding diagram, any maneuver can be described as a series of rotations along the X, Y, or Z Axis - alone or in combination. Such rotations are divided into three categories: Roll (rotation along the X Axis), Pitch (rotation along the Y Axis), Yaw (rotation along the Z Axis). As well, each category can be in either of two directions.
The position of objects outside of a vessel (planets, stars, other vessels) are described by means of relative bearings The bearings are so-called because they are relative to a line forward of the vessel's bow. A set of bearings is of two parts. The first bearing is along a great-circle running clockwise from 000 degrees (dead ahead) along the equatorial plane through 180 degrees (dead astern) to 359 degrees (just one degree short of dead ahead again). Thus the first bearing circles the vessel "horizontally", and is also known as the azimuth. The second bearing curves up to +90 degrees (zenith), or down to -90 degrees (nadir) from the azimuth, and is also known as the elevation or depression angle.
When recorded or stated, a relative bearing is listed thus: Bearing, Azimuth Angle, Mark, Elevation/Depression Angle. Therefore the illustration above would be described: Bearing 356.8 Mark 17. A relative coordinate is stated: Relative Bearing, Range. An example would be: Bearing 356.8 Mark 17, Range 2.9 parsecs.
There are three types of planetary orbits used primarily by Starfleet vessels. Each has its own particular function and type Number for ease of Command. The examples below include Type, Description, Function, and a diagram showing the orbital path relative to the planet and its rotation (dynamics). It is an axiom that no planet is a perfect sphere - each has its own imperfections in terms of shape (mountain ranges, ocean bed trenches) and density concentrations (mascons). Such imperfections cause distortions in the theoretically smooth and symmetrical gravity well surrounding a planet. For this reason, vessels in orbit must apply occasional maneuvering thrust to adjust anomalies in their orbital path - especially in close orbits, where orbital decay is never far off.
- Type 1: (Standard Orbit) With the planet rotating below, the vessel travels in a low orbital path which overtakes the rotation by a factor of five or more. Thus the vessel traverses the entire equatorial belt, useful for scanning for civilizations, and allowing for frequent communication and transport with widely scattered Landing Parties at intervals.
- Type 2: (Geosynchronous Orbit) Orbiting in synch with the planet's rate of rotation, the vessel remains poised over one planetary coordinate near the equator. Essential for moni-toring a critical on-planet activity, remaining in constant contact with a Landing Party, or staying on alert in case of an immediate transport requirement.
- Type 3: (Polar Orbit) Utilized for cartographic survey, or search-and-rescue scanning modes. Maintaining a close orbital path at right-angles to the planet's rotation, the vessel will eventually have traveled directly over every section of the planet, as the planet continues to rotate beneath it.
Various phenomena existing In space pose serious dangers to spacecraft navigation. Some of these objects/ conditions are natural, others are artificial. All are included on standard military and civilian starcharts. These hazards can be identified by their coding, which consists of two parts: a letter designating the type of hazard, and a number denoting the danger-level the particular hazard was assigned by the discovering vessel and the Federation Bureau of Navigation (1 denoting low danger and 10 high). Thus a coding of I-4 describes a moderate Ion Storm.
Since man first began voyaging in wooden boats upon the seas of Terra, he has navigated by the stars. As his oceangoing vessels grew more sophisticated, so also did his navigational aids (inertial guidance, satellite reference). but always as a final check he used the "fixed" stars. As man moved into space the stars regained their primary importance. Whether for orbital, interplanetary, or even slower-than-light interstellar travel, the stars served as readily visible points of reference. By this time "epoch" - the proper motion of stars - had been discovered, but when compared with the speeds of the vessels, epoch vectors (measured in km/sec) were of little consequence.
However, in the early twenty-first century this changed, as Warp Drive was invented. Suddenly the distant stars were not so distant, and their apparent motions ever-more-so difficult to calculate as vessels out-raced the photons themselves. Also, identifying individual stars (other than those within a few parsecs) while traveling at Warp speeds turned out to be extremely difficult. Worse yet, a vessel travelling ten or twenty parsecs could re-enter normal space to find that all but the brightest stellar benchmarks (Antares, Rigel) were now indistinguishable from the surrounding background. A need had arisen for a new type navigational reference point—one easily located at long interstellar distances.
The solution was pulsars. These phenomena were first detected by radio astronomers in the early atomic era (Terra 1970's CE). Each was shown to be a distant, swiftly rotating on star, whose fierce magnetic field collimated its intense electromagnetic emissions into two beams - so that emissions were only detectable on a plane perpendicular to the pulsar's axis of rotation. Extremely accurate regarding "pulse-rate" (consistent to within .000014 % per year), it was decided by the United Earth Space Probe Agency - forerunner of Starfleet - to utilize pulsars as beacons.
