Ways to navigate cruise missiles

Taking into account the experience of fighting the introduction of cruise missiles in surrounding six and a half decades, they can be regarded as a mature and well-proven technology. During their existence came a substantial development of technologies used in the development of cruise missiles, clasps glider, engines, air defense and means of overcoming the navigation system.

Thanks to technology creation, airframe missiles were becoming more and more than small-sized. Now they can be placed in the inner compartments and on the exterior of aircraft hangers, ship launchers tube type or submarine torpedo tubes. The engines have changed from conventional pulse jet engines through the turbojet and liquid-fuel rocket engines or ramjet engines (ramjet) to today's composition turbojet engines for subsonic tactical cruise missile turbofan subsonic strategic cruise missiles and ramjet engines or mixed turbojet / rocket configurations for supersonic tactical cruise missiles.

Means to overcome the defense appeared in the 1960s, when the air defense system to hold the outstanding efficiency. These include low altitude with terrain following flight or missiles at maximum low altitude above the sea surface in order to hide from radar and are increasingly shape enhances low profile and radio-absorbing materials designed to reduce the radar signature. Some Russian cruise missiles were also equipped with a defensive purpose jammers designed to thwart interception zenitnoraketnyh complexes.

After all, during this period significantly developed and a variety of system Navigation cruise missiles.

Difficulty navigating cruise missiles
The basic idea of all the cruise missiles would be that a tool can be launched at a target beyond the reach of enemy air defense systems in order not to launch platform response to the attack. This makes it tough prepyadstviya design, the first of which is a cruise missile task force firmly move to a distance of thousands of miles in a particular closeness to the task — and how it will be in the vicinity of a specific target, the warhead to provide clear guidance on target to produce the planned military effect.

First combat cruise missile FZG-76/V-1

The first battle was a German cruise missile FZG-76/V-1, over 8,000 of which were used, while in the main, on targets in England. Judging by modern standards, then its navigation system was quite primitive: the autopilot based on gyro rate stood and anemometer distance to the target. The rocket was exhibited on track before the start and it exhibited the payment distance to the target and as the odometer indicated that rocket is above the target, the autopilot leads her into a steep dive. The missile has an accuracy of about a mile and that was enough for bombing targets large city such as London. The main purpose of the bombing was terrorizing the civilian population and the military forces of Britain distraction from offensive operations and forwarding them to perform air defense missions.

1st South American cruise missile JB-2 is a copy of the German V-1

In particular period after the war, the U.S. and the USSR recreated V-1 and began developing their own programs of their own cruise missiles. The first generation of theater and tactical nuclear weapons has caused the creation of a series of Regulus cruise missile of the U.S. Navy, a series of Mace / Matador U.S. Air Force and the Russian series Comet CS-1 and Comet-20 and future development of navigation technology. All of these missiles are initially use autopilots based on clear gyroscopes, but also the ability of adjusting the line of the rocket on the radio channel so that a nuclear warhead could be delivered as soon as possible precisely. Slip into hundreds of meters can be is enough to reduce the excess pressure produced a nuclear warhead was below the lethal threshold of hardened targets. In the 1950s, came into service the first post-war conventional tactical cruise missiles, initially as anti-ship weapons. While midcourse guidance line of motion lasted based gyroscope, and from time to time and corrected by radio, the pointing accuracy on final line of motion was provided with radar homing short-range actions, semi-active on most of early versions, but soon displaced by active radar . Missiles of this generation usually fly on medium and large heights, swooping in an attack on the target.

Intercontinental cruise missile Northrop SM-62 Snark

The subsequent fundamental step in navigation technology cruise missiles followed by the adoption of weapons of intercontinental land-based cruise missiles Northrop SM-62 Snark, designed for autonomous flight over the polar regions to attack large nuclear warheads to targets terrain Russian Union. Intercontinental distances before the designers presented a new challenge — to make a missile capable of hitting targets at a distance of 10 times more than it was able to make more of early versions of cruise missiles. On the Snark was set corresponding to the inertial navigation system uses a gyro stabilized platform and clear accelerometers to measure the motion of a rocket in space, an analog computer used for the accumulation of measurements and determine the position of the rocket in space. But soon revealed the problem, the drift in the inertial reference system was very large for the operational use of the missiles, and the errors of the inertial positioning system were cumulative — so Makar, the positioning error accumulate with each hour of flight.

The solution to this was prepyadstviya other device designed to perform high-precision measurements of the geographical position of the rocket on the trajectory of its flight and able to fix or "anchor" the errors generated in the inertial system. This is the basic idea and still is central to the design of modern control tools. Thus, the accumulated errors of the inertial system at times reduced to a positional error measurement device.

Martin Matador cruise missile

To solve the puzzles has been used astronavigation system or orientation of the stars, automatic optical device which can measure the angular position of the famous stars and use them to calculate the position of the rocket in space. Astronavigation system have been very clear, and quite expensive to manufacture and difficult to maintain. Also require that the missiles equipped by the system, flying at high altitude in order to avoid the impact of clouds on the line of sight to the stars.

Least it is clear that success astronavigation systems everywhere provided the impetus to the development in the current time of satellite navigation systems such as GPS and GLONASS. Satellite navigation is based on a similar concept of celestial navigation, but instead of stars used satellites in polar orbits, and natural light instead of artificial microwave signals are also used pseudo-range measurements, rather than angular measurements. In the end, this system significantly lowered costs and is allowed to make spotting at all altitudes in all weather criteria. Despite the fact that satellite navigation technology was invented first
the 1960s, they were quickly consumed only in the 1980s.

In the 1960s, there have been significant improvements in the accuracy of inertial systems, such as increased price of the equipment. This eventually led to conflicting requirements for accuracy and cost. As a result there was brand new development in the field of navigation cruise missiles based on the positioning system by comparing missile radar display area with a reference mapping applets. This development came to the United States armed cruise missiles in the 1970s, and Russian missiles in 1980. Development TERCOM (system of digital correlation with the terrain cruise missile guidance unit) was used as the system of celestial navigation, to reset the total inertial system errors.

Cruise missile Comet

Development TERCOM respect of the ordinary on the plan, although complex in detail. Winged rocket without annoying determines the height of terrain under the flight path of its own, using a radar altimeter, and associates the results of these measurements of barometric altimeter readings. The navigation system also stores TERCOM inside digital terrain elevation map, on which she will fly. Then, using a computer-profile programs from areas over which the missile flies compared with a stored digital map of heights in order to find the best of their satisfaction. As a profile consistent with the database, we can very accurately find the position of the missile on a digital map that is used to correct the cumulative errors of the inertial system.

TERCOM had a big advantage over the astronavigation systems: it permitted to produce cruise missiles flying at low altitude as necessary to overcome the enemy's air defense, it was relatively a cheap to produce and very clear (up to 10-ka meters). This is more than enough for the 220 kiloton nuclear warhead and is sufficient for 500 pound conventional warhead used against a huge number of types of goals. Yet TERCOM was not without its shortcomings. The rocket that was unique proparhat over rolling hills, just being compared with the profile of digital elevation maps, had stunning accuracy. But TERCOM proved ineffective over aqua surface of the seasonally variable terrain, such as sand dunes and terrain with varying seasonal radar reflectivity, such as the Siberian tundra and taiga, where snowfall can vary the height of terrain features or hide it. The limited capacity of rockets often made it difficult keeping a sufficient number of map data.

Cruise missile Boeing AGM-86 CALCM

Being sufficient for nuclear warheads filled KR Tomahawk RGM-109A Navy and the AGM-86 ALCM Air Force, TERCOM was apparently not sufficient for the destruction of the ordinary warhead individual buildings or structures. In this regard, the U.S. Navy equipped with Tomahawk cruise missiles TERCOM RGM-109C / D additional system based on the so-called correlation technology display object with its reference digitally. This design was used in the 1980s on ballistic missiles Pershing II, Russian and American KAB-500/1500Kr precision bombs DAMASK / JDAM, also driven by recent Chinese anti-missile systems designed to combat aircraft carriers.

When the correlation display object is used to lock the camera in front of a missile area, and then the information from the camera is compared with a digital image acquired by satellite or aerial reconnaissance and lying in the memory of the rocket. By measuring the angle of rotation and displacement necessary for a clear coincidence of 2-image, the device is able to find a jeweler's precision missiles and position error use to correct its mistakes and TERCOM inertial navigation systems. Block digital correlation cruise missile guidance systems DSMAC used for several blocks KR Tomahawk were indeed accurate, but has side effects similar to the operational TERCOM, which had to be programmed on the flight of a rocket over a recognizable terrain especially in the vicinity of a particular purpose. In 1991, during Operation Desert Storm, it has led to a number of highway interchanges in Baghdad have been applied as such bindings, which in turn allowed the troops to Saddam's air defense anti-aircraft batteries placed there and knock down a few Tomahawks. As well as digital TERCOM block correlation cruise missile guidance system is sensitive to seasonal changes in contrast areas. Tomahawks, kitted DSMAC also carried the flashlight to illuminate the area at night.

In the 1980s, a South American cruise missiles have been integrated into the first receivers of GPS. Development of GPS was presentable as she let a rocket constantly correct its inertial errors regardless of the terrain and the weather criterion, as it acted as a prototype of the water and the ground.

These advantages have been offset by the problem of a weak immunity GPS, because the GPS signal is in its nature very weak, susceptible to the effect of "re-image" (when the GPS signal is reflected from the terrain or buildings) and the change of accuracy regardless of the number of satellites received and the fact they are distributed over the sky. All of the South American cruise missiles today are equipped with GPS receivers and a packet of inertial guidance systems, while in the late 1980s and early 1990s, the technology of mechanical inertial systems have changed over a cheap and more than accurate inertial navigation system on ring laser gyros.

A cruise missile AGM-158 JASSM

Tasks related to the accuracy of the basic GPS uniformly solved by the introduction of wide-range of ways GPS (Wide Area Differential GPS) in which the correction signals are valid for this geographical location are broadcast to the GPS receiver via a radio channel (in the case of U.S. missiles used WAGE-Wide Area GPS Enhancement). The main source of the signals of the system are radio navigation beacons and satellites in geostationary orbit. Clearer technology of its kind developed in the U.S. in the 1990s, are able to correct errors GPS to several inches in 3 dimensions and are pretty accurate to get a rocket into the open hatch armored vehicles.

Difficulties in immunity and "re-image" were more difficult to manage. They have led to the introduction of technology so called "smart" antennas are usually based on the "digital beamforming" in the software. The idea behind the technology of the ordinary, but usually complicated in detail. Ordinary GPS antenna receives signals from all over the upper hemisphere of the rocket, so Makarov, including satellites GPS, as the enemy interference. So called antenna with steerable (Controlled Reception Pattern Antenna, CRPA) using the software synthesizes narrow beams directed to the supposed location of satellite GPS, with the result that the antenna is "blind" in all other directions. More advanced antenna design of this type create a so-called "zero" in the antenna pattern aimed at noise sources for the coming oppression of their impact.

Winged raketaTomagavk

Most of the well-publicized problems first production of cruise missiles AGM-158 JASSM were the result of problems with the software receiver GPS, as a result of which the missile
was losing the GPS satellites and knocking with his own line of motion.

Advanced GPS receivers provide the highest level of accuracy and reliable immunity to placed on the earth's surface interference sources GPS. They are less effective against sophisticated GPS interference sources deployed on satellites, unmanned aerial vehicles, or balloons.

The latest generation of American cruise missile uses GPS-inertial guidance system complements it installed in the nose of the rocket digital thermal imaging camera, the aim is to ensure the ability of such DSMAC motionless against targets with the right software and the possibility of automatic recognition of images and against moving targets, such as anti- missile systems or missile launchers. Stripes data usually come from technology JTIDS/Link-16, being introduced to the ability of retargeting tools in a case where a moving target changed its position in the Time Spent rockets on the march. The introduction of this function priemuschestvenno is dependent on the users who own intelligence and ability to identify such movements end.

Long-term trends in the development of cruise missiles, navigation will lead to their greater intelligence, greater autonomy and a greater abundance in the sensors, excessive reliability and lower prices.

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