4.4 Inertial Navigation System
215
would resist errors due to sideway acceleration of the ship or aircraft carrying it. It is
a well-known Schuler tuning, a design principle for the INS considering the curvature of the Earth. The Schuler tuning completely solves the problem of tracking the
local vertical line with the established artificial vertical line on the movable object,
laying a foundation for the practical application of the INS.
In 1942, an elementary inertial navigation device was equipped on the V-2 missile
developed by W. von Braun in Germany. As a result, the heading and attitude angles
of the missile were provided by the gyroscope, and the initial velocity of the missile
into trajectory was provided by the gyro-integral accelerometer installed along the
longitudinal axis, so as to guide and control the missile for flight. Although the
guidance accuracy of the inertial navigation device was very low, it had created a
precedent for the application of the INS. With the improvement of gyro stability and
accuracy, inertial technology was gradually applied to the navigation for aircraft and
submarine. In 1949, FEBE (named after the Roman Sun god Phoebus), an inertial
device with a single degree-of-freedom liquid floating gyroscope, was used for the
navigation of the strategic bomber B-29, with a stellar and magnetic coordinate as
reference. The FEBE had created a record of 10-h autonomous flight test, which
showed the inertial navigation was then feasible over moderate distance without
stellar tracking. In 1950, the complete inertial auto-navigator XN-1 was developed by
the electromechanical department of North American Aircraft inc. (established as the
Autonetics Division in 1955), and its auto-navigational capability was demonstrated
in a flight of a C-47 aircraft. Meanwhile, the inertial navigation device N-6 was
developed by improving the XN-1, and successfully applied to the navigation of
marine ships. In 1958, the U.S. Navy’s nuclear submarine Nautilus was equipped
with the N-6A inertial navigation system and the MK-19 north-seeking compass,
starting from Pearl Harbor near Honolulu of Hawaii, crossing the Arctic icecap and
finally arriving at Portland Harbor of Oregon. The entire voyage spent 21 days, and
as the Nautilus surfaced near Portland Harbor, its position error was determined to be
only 20 nautical miles. It fully demonstrates the INS advantages like the autonomy,
concealment and completion, with the unique military application value.
In the 1960s, the technology of liquid floating gyroscope had been improved
while the studies on flexible gyroscopes and dynamically tuned gyroscopes had
risen. The dynamically tuned gyroscope had the advantages of simple structure, easy
manufacture and low cost, with the drift error of 0.01 degrees per hour, and was
widely used in the SINS. The inertial navigation system LTN-72 with the dynamically tuned gyroscopes was developed by Litton Industries, Inc. and had widely been
used in the civil aircraft at that time. In the 1970s, Honeywell International Inc. and
Rockwell Automation Inc. began to develop the electrically suspended gyroscopes
with the drift error of less than 0.0001 degrees per hour. The electrically suspended
gyroscopes were mainly used for the high-precision reference of strategic weapon
throwing platform. Two sets of inertial navigation devices MK-27 with the electrically
suspended gyroscopes, developed by the Rockwell, were equipped on the Ohio-class
strategic nuclear submarine of the U.S. Navy. Afterward, the laser and fiber optic
gyroscopes have developed gradually, whose stability and reliability are far better
than the mechanical rotor gyroscopes, with the average failure time of 90,000 h. The
215
would resist errors due to sideway acceleration of the ship or aircraft carrying it. It is
a well-known Schuler tuning, a design principle for the INS considering the curvature of the Earth. The Schuler tuning completely solves the problem of tracking the
local vertical line with the established artificial vertical line on the movable object,
laying a foundation for the practical application of the INS.
In 1942, an elementary inertial navigation device was equipped on the V-2 missile
developed by W. von Braun in Germany. As a result, the heading and attitude angles
of the missile were provided by the gyroscope, and the initial velocity of the missile
into trajectory was provided by the gyro-integral accelerometer installed along the
longitudinal axis, so as to guide and control the missile for flight. Although the
guidance accuracy of the inertial navigation device was very low, it had created a
precedent for the application of the INS. With the improvement of gyro stability and
accuracy, inertial technology was gradually applied to the navigation for aircraft and
submarine. In 1949, FEBE (named after the Roman Sun god Phoebus), an inertial
device with a single degree-of-freedom liquid floating gyroscope, was used for the
navigation of the strategic bomber B-29, with a stellar and magnetic coordinate as
reference. The FEBE had created a record of 10-h autonomous flight test, which
showed the inertial navigation was then feasible over moderate distance without
stellar tracking. In 1950, the complete inertial auto-navigator XN-1 was developed by
the electromechanical department of North American Aircraft inc. (established as the
Autonetics Division in 1955), and its auto-navigational capability was demonstrated
in a flight of a C-47 aircraft. Meanwhile, the inertial navigation device N-6 was
developed by improving the XN-1, and successfully applied to the navigation of
marine ships. In 1958, the U.S. Navy’s nuclear submarine Nautilus was equipped
with the N-6A inertial navigation system and the MK-19 north-seeking compass,
starting from Pearl Harbor near Honolulu of Hawaii, crossing the Arctic icecap and
finally arriving at Portland Harbor of Oregon. The entire voyage spent 21 days, and
as the Nautilus surfaced near Portland Harbor, its position error was determined to be
only 20 nautical miles. It fully demonstrates the INS advantages like the autonomy,
concealment and completion, with the unique military application value.
In the 1960s, the technology of liquid floating gyroscope had been improved
while the studies on flexible gyroscopes and dynamically tuned gyroscopes had
risen. The dynamically tuned gyroscope had the advantages of simple structure, easy
manufacture and low cost, with the drift error of 0.01 degrees per hour, and was
widely used in the SINS. The inertial navigation system LTN-72 with the dynamically tuned gyroscopes was developed by Litton Industries, Inc. and had widely been
used in the civil aircraft at that time. In the 1970s, Honeywell International Inc. and
Rockwell Automation Inc. began to develop the electrically suspended gyroscopes
with the drift error of less than 0.0001 degrees per hour. The electrically suspended
gyroscopes were mainly used for the high-precision reference of strategic weapon
throwing platform. Two sets of inertial navigation devices MK-27 with the electrically
suspended gyroscopes, developed by the Rockwell, were equipped on the Ohio-class
strategic nuclear submarine of the U.S. Navy. Afterward, the laser and fiber optic
gyroscopes have developed gradually, whose stability and reliability are far better
than the mechanical rotor gyroscopes, with the average failure time of 90,000 h. The