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Cruise Missile
This section provides a brief, unclassified discussion of cruise missiles. It contains a summary of the principal attributes; provides a history; describes the technologies and characteristics of cruise missiles; gives brief descriptions of the cruise missiles that have been developed over the years; discusses the possible future of cruise missiles; and concludes with potential improvements.
Summary of Cruise Missile Attributes
• Pilotless, air-breathing (sometimes rocket powered), continuously powered, usually relatively low flying, guided using aerodynamic lift and control throughout flight.
Some cruise missiles (e.g., Tactical Tomahawk) have two way data links for missilestatus and retargeting.
• Payload is integrated as part of the airframe, with missile assumed destroyed at the end of the mission.
• Ranges can extend thousands of miles, with accuracies of tens of feet.
• Can be launched from land, sea surface and sub surface, and air.
• Payloads of conventional and nuclear warheads, other specialized cruise missile payloads considered, at least conceptually, include ISR systems/sensors and niche weapons concepts (non-kinetic weapons
, penetrators for HDBT, etc.).
• Speeds can be sub- or supersonic. Typical flight times range from tens of minutes to several hours.
History
Cruise missiles were first conceptualized in about 1891 by Sir Hiram Maxim, the inventor of the modern machine gun and a dabbler in flying machines. The first example of a cruise missile was the Kettering Bug, commonly known as an aerial torpedo. It was an unmanned biplane that flew in a straight line for a set period of time, detached its wings and struck the ground with the fuselage and warhead. Developed during World War I, it integrated aircraft guidance technologies developed by Elmer and Lawrence Sperry for a U.S. Army project led by Charles F. Kettering. The first flights occurred in the fall of 1918, but it was never used in war as WWI came to an end that November.
Between World War I and World War II both the British and Americans continued aerial torpedo development. The first launch of a cruise missile (called Larynx) from a destroyer at sea occurred in the 1920s. Prototype aircraft with names such as Hoop-la (British), various versions of Mistel (German), and TDR-1 (American) appeared during WWII with varying results. These all appeared similar to manned airplanes of the day.
The first cruise missile used in war was the German V-1 flying bomb. The V-1 was used in raids against England beginning in June 1944. . It had the appearance of a modern day cruise missile with a bomb-like fuselage and short wings and fins. It was small and cheap and was made and used in very large numbers with effect. Powered by a pulse jet engine and guided by an inertial guidance system, it flew at high speed and low altitude, and had a range of about 250, and later 400, kilometers (140 and 225 nm) with a warhead
of 800 kilograms (1760 pounds). Initially launched using a steam catapult from ground ramps, V-1s initially had metal wings (later changed to wood) with no control surfaces; instead employing tail fins and a rudder for control. Gyroscopes kept it stable, a magnetic compass controlled direction, and a barometric altimeter
controlled altitude. Powered after launch by a distinctive sounding pulse-jet engine, V-1’s used either a timing or a distance-estimating system to lock the control surfaces and pop out spoilers, which would put the missile into a steep dive. The V-1 used an electric fuse, but had mechanical and time-delay fuses for backup. By today’s standards, it was not accurate (it is believed half the V-1s fell roughly within four miles of the aim point), but it was accurate enough to spread terror in the city of London and the English countryside. The V-1 could be fitted with a nerve gas warhead, but this variant was never used. Other payloads did see some use: including 23 one-kilogram incendiary bomblets and a cardboard tube with propaganda leaflets.
Toward the end of the war, some V-1s were launched from specially modified Heinkel He-111 bombers. At least 30,000 were built during the World War II.
Cruise Missile Technologies
The V-1 story provides a quick introduction to the technologies that make cruise missiles work.
As the state of the art in these technologies evolved, the types used in cruise missiles changed.
Key technologies that form the basic components of cruise missiles are described in more detail
as follows:
• Propulsion and fuel (for both launch and flight): Most cruise missiles use a booster (usually a solid fuel rocket) for launch and a jet engine for sustained flight. The fuels used vary from one missile type to another.
• Aerodynamics (bodies, wings, and control surfaces): Nearly all cruise missiles use shapes and surfaces to maintain and control flight, as in manned aircraft.
• Guidance and Navigation: Today, most cruise missiles use some kind of INS, composed of gyros and accelerometers. Many modern cruise missiles employ an additional external data input to provide in-flight position updates to the INS to refine the navigator, thus significantly increasing the overall accuracy. Such data sources include updates from map or scene matching algorithms; in addition, nearly all modern cruise missiles use GPS for this purpose. Another external data source for navigation updates that is common to modern cruise missiles are altimeters (barometric, radar, and combined).
• Communications: As will be discussed later, several of today’s cruise missiles use in-flight communications. Some allow the missile to report its status and many allow controllers to change some aspect of the mission being flown (including designating a new target).
• Sensors: Some cruise missiles carry sensors, primarily radars and cameras. These
are used for navigation purposes or as ISR sensors.
• Payloads (kinetic and non-kinetic) and fuses: Most cruise missiles carry explosive warheads (conventional and nuclear), unitary bombs or smaller bomblets. Non-kinetic warhead concepts also exist, including biological and chemical constructs. The fuse activates the warhead, and fuse types include contact fuses (sometimes with fixed or selectable time delays), timing fuses, altimeter fuses, and distance measuring
fuses (as in the V-1).
Cruise Missile Characteristics
The primary characteristics of cruise missiles are provided below:
• Unmanned
• Speed and range: Although a few cruise missiles travel at more than the speed of sound, most are subsonic, usually high subsonic. Maximum ranges vary from a few 10s of miles to more than 1000 miles.
• Time of flight: Speed and range obviously combine to yield a time of flight to the target, which together with times for other links in the kill chain (ISR and C2 times) produces a total reaction time — the time it takes to search for, decide to strike, and hit a target. Most cruise missile flight times range from tens of minutes up to several hours (again dependent on speed and range to target).
• Flight Profile (altitude, maneuverability, etc.): Cruise missiles essentially are confined to altitudes of less than about 30,000 feet (although there are a few modern variants that can fly much higher during some portions of the flight profile). Many cruise missiles fly very close to the surface of the earth to avoid
detection and try to “hug” the terrain.
• Part of a cruise missile flight profile can include a loiter interval; this can be used to reduce the response time by reducing the time of flight for an emergent or time sensitive target or to redirect the missile with updated target information. The message to transition from a loitering posture to striking the target (or to a new target) can come via communications from an external “controller” or from an organic sensor on the missile.
• Accuracy: Many cruise missiles are coordinate-seeking weapons, i.e., they guide to the geographic coordinates (latitude, longitude, and altitude, usually in GPS coordinates) provided to them. There are cruise missiles with organic seekers/sensors of some type for improved targeting. Some cruise missiles can also be provided real-time direction from a human (man-in-the-loop,or MITL) for designated targets.
In general, accuracy has two contributing factors: target location error (TLE – not knowing exactly where the target is) and circular error probable (CEP – not being able to navigate and guide to the aimpoint, exactly
where the target is believed to be). CEP has two components: Navigation, which is how well the missile knows where it really is (depends on the type and quality of the navigation system), and guidance, that is, how well the missile can guide to where it wants to be (depends on the maneuverability and controllability of the missile). Accuracy errors are associated with all three spatial dimensions. For coordinate-seeking cruise missiles, GPS alone can produce accuracies with miss distances of several 10s of
feet. Other update techniques can achieve improved accuracies, especially approaches that combine INS with external sources such as GPS.
• Launch platforms: Cruise missiles can be launched from ships, submarines, aircraft, and land sites. Special launchers are often needed, although some submarines use normal torpedo tubes and some aircraft can use existing pylons. A system is required on the launch platform or near the launch point to transport, store, power up, and initialize the missile prior to launch.
• Sensors: Cruise missiles often have sensors associated with their navigation systems, including the TERCOM radars, DSMAC cameras, or other position update sensors.Tactical Tomahawk also uses the DSMAC camera to record battle damage indication images of previous strikes at preplanned locations as the missile flies over. Other sensors can include devices intended to detect, identify, locate, and sometimes home on the missile’s target.
• Reliability: This is a measure of the probability that the cruise missile will successfully achieve the desired effect. Typically reliability is the cumulative probability of successful initialization, launch, flight, control, and warhead detonation. Reliability (and accuracy) are often used in determining numbers of missiles required to achieve an overall desired effect on a given target.
Cruise Missiles – Past, Present, and Future
The following is a brief discussion of cruise missile evolution after WWII. Immediately after the war, and even during the last stages of the war, the U.S. Air Force, the U.S. Navy and the Soviet military built their own cruise missiles based on the V-1, and the U.S. Army tried its own “flyingwing” design. Most launches were from the ground, but air-launched, surface ship-launched and even submarine-launched cruise missiles were explored by the services.
Cruise Missiles from the 50s and 60s
From the late 1940s through the end of the 1960s, many efforts were made to develop guided missiles in general, and guided cruise missiles in particular. While these efforts made progress in understanding the key technical issues and maturing the required technologies, they did not succeed in producing a practical cruise missile. Most of these missile concepts were supersonic with ranges of up to several thousand miles (that consequently resulted in very large missile sizes and weights). Many of these early Cold War cruise missile concepts had significant challenges in flight control, guidance and navigation, and overall reliability. Early missiles and programs included the USAF’s Matador, Mace, Snark, Hound Dog, Crossbow, Navaho, Buck Duck, Bull Goose, and Quail; and the USN’s Regulus series, Rigel, and Triton.
Modern Cruise Missiles (from the 70s to the present)
By the late 1960s, the various key technologies required by cruise missiles had matured enough such that operationally useful cruise missiles became practical and affordable. These technologies included developments in improved accuracy of gyros and accelerometers and smaller, more powerful computers. With these advances, developments began in earnest of cruise missiles that became operational, and several remain in service today, as described as provided below.
• Harpoon (AGM/RGM/UGM-84A) – USN/USAF. Air-, ship-, and sub-launched anti-ship cruise missile. It originally used a heading reference system and a radar seeker to find and guide to the target. Operational range was initially about 60 nm. Harpoon operational deployments started in 1977 and continue to this day.
• Tomahawk (RGM/UGM 109A/B/C/D/E) Sea-Launched Cruise Missile (SLCM) – US and UK navies. The A variant had a nuclear warhead for striking very distant land targets, and the B variant was an anti-ship missile (similar to Harpoon) with an operational range of about 250 nm. Neither are operational today. The C and E
variants have large unitary warheads and the D variant has small bomblets that can be distributed over one or more areas. The E is called Tactical Tomahawk, which is less expensive and has, among other things, two-way communications, including redirection of the missile after launch. The C and E variants have ranges of about 900nm. The Tomahawk series started in the early 1980s and continues to evolve today.
• ALCM (AGM-86A/B/C/D) Air-Launched Cruise Missile – USAF. The A and B variants had nuclear warheads, and the C and D are conventional (called CALCMs). The C has a unitary blast fragmentation warhead, and D has a penetrator warhead.The ranges are about 750 miles. Initially operated in the early 1980s, it remains
operational today.
• ACM (AGM-129A/B) Advanced Cruise Missile – USAF. These air-launched cruise missiles have nuclear warheads, have longer range capability (1865 mi) than the ALCM and CALCM missiles, and use stealth technology.
• SLAM – ER (AGM-84K) Standoff Land Attack Missile-Expanded Response – This missile is an evolution of Harpoon (AGM-84A) and SLAM (AGM-84E). The SLAM– ER is air-launched with GPS-aided inertial navigation, has an imaging infrared seeker and fire-and-forget or MITL (with two-way AWW-13 communications pod) for target selectivity and moving target capability.
• TSSAM (AGM-137) Tri-Service Standoff Attack Missile – USAF/USN. Air-launched cruise missile with conventional warhead and 600nm range. Cancelled in EMD phase and essentially replaced by the JASSM program.
• JASSM (AGM-158), Joint Air to Surface Standoff Missile – USAF/USN. Air-launched, 250 nm nominal
range, GPS-aided navigation and an imaging infrared seeker in terminal phase, an automatic target correlator, and a penetrating warhead. The JASSM has a one-way bomb impact assessment transmission viacommunications link.
Before and during these same years, other countries began to develop cruise missiles, many of which saw use in conflict and remain operational today. As would be expected, the Russians have developed a variety of cruise missiles. The sinking of the Israeli destroyer Eilat in 1967 by a Soviet-built Styx anti-ship cruise missile is often credited with renewing the USN’s interest in cruise missiles. While there are many examples
of foreign cruise missiles, most are relatively short range. France has developed a family of cruise missiles known by various names depending on their specific attributes (including the country that deploys it) such as APACHE, Scalp, and Storm Shadow. These French missiles are air-launched, land attack, standoff (i.e.,
relatively short range) weapons, with GPS-INS navigation and terrain following capability.
Sweden and Germany have together developed a land attack missile called Taurus, with terrain-matching navigation, an imaging IR seeker and a range of nearly 300 nm. Israel developed Delilah, again with GPS-INS, a datalink, a seeker, and a loiter capability with a nominal range of 150 nm.
Planned Cruise Missiles in Near Term
There is a continued desire to improve capabilities of cruise missiles by making them faster, better (range, accuracy, etc), cheaper, smaller, and easier to operate. Cruise missiles planned (that is in the program of record or being considered) for the near future include:
• Future Tactical Tomahawk – USN. Includes improvements in C2 and interoperability, more robust datalink, a multiple effects warhead, PTAN for GPS-independent navigation updates, ASUW, and mobile target capabilities. New launch platforms: include SSGN and DDG 1000. Possible Block V upgrade with high speed
capabilities are also under consideration.
• JASSM-ER – USAF. Range of 500 nm with new engine, two-way datalink including capability for target update in flight. Includes planning for an anti-ship capability (2011 for JASSM-ER and 2012 for JASSM).
• JASSM–XR – USAF. Extra Extended Range version being considered with range up to1000 nm. Launch platform would include bombers and heavy strike aircraft.
• Affordable Weapon – USN. As the name implies, a less expensive (<$30K) capable “cruise-like” missile. Missile concept is rocket launched from a shipping container and powered in flight by a small turbojet engine with in-flight retargeting using a two way data-link. This missile would have a loitering capability and a payload of up to 200 pounds with a maximum range of up to about 800 nm.
• RATTLRS, Revolutionary Approach to Time Critical Long Range Strike – USN, USAF, NASA. This is a technology demonstration that is part of the National Aerospace Initiative and sponsored in part by Office of Naval Research (ONR). This concept has a turbine engine that operates at Mach 3.0 for about 5 minutes. It could be air-launched, as well as ship- and sub-launched.
• LOCAAS, Low Cost Autonomous Attack System – AFRL. This is a miniature airvehicle with a laser radar seeker, smart targeting algorithms, and a multi-purpose warhead. Intended to be employed against
moving/relocatable targets and capable of multi-missile swarming tactics.
• SMACM, Surveilling Miniature Attack Cruise Missile – USAF. A proposal based on LOCAAS and Joint Common Missile technologies to be built from affordable, off-the-shelf components. Essential concept is a loitering, stand-off weapon that searches for targets with its on-board sensors.
During the past decade, there has been an increased emphasis on concept development, experimentation, and demonstrations aimed toward building a practical supersonic or hypersonic capability for aircraft and cruise missiles. Some relevant high-speed demonstration programs are described as follows:
• Fasthawk, Low Cost Missile System (LCMS) Advanced Rapid Response Missile Demonstrator (ARRMD) – ONR. This Advanced Technology Demonstration (ATD) was conducted in 1997 and 1998. Missile characteristics included a bending body, a rocket booster with ramjet engine that would have a 700 nm range and speeds of up to Mach 4.0. While LCMS terminated in 1998, this effort evolved into what became the
HyFly concept.
• HyFly – DARPA/ONR. This is a hypersonic flight demonstration program using a dual combustion ramjet propulsion concept. Additional attributes of HyFly include high-temperature materials and hypersonic guidance and control. Concept variants would include surface ship, submarine, and air-launched missiles with ranges of about 600 nm, at speeds up to and greater than Mach 6.0.
• HyTech (Hypersonic Technology) – AFRL. This is a scramjet research and test
program that is examining speeds of Mach 4.5 to Mach 6.5.
•JSSCM, Joint Supersonic Cruise Missile– DTRA/OSD/OPNAV. Came out of an April 2002 solicitation for a supersonic cruise missile ACTD that had a range of 400 nm and would operate at Mach 3.5 to Mach 4.5 with a CEP of 3 m.
• FALCON, Hypersonic Force Application and Launch from CONUS –DARPA/USAF. A reusable hypersonic
cruise vehicle that can carry several munitions, including cruise missiles and bombs.
• X-43A (Hyper-X) – NASA. A cruise missile size, unmanned, air-breathing, hypersonic flight research aircraft, with speeds of Mach 7 to Mach10. This aircraft reached sustained speeds of Mach 6.8 in March 2004 and Mach 9.6 in November 2004 at an altitude of near 100,000 feet.
• X-51 (Waverider) – AFRL. An air-launched hypersonic cruise missile for the B-52. Concept has launching aircraft at 35,000 ft. The missile’s solid rocket booster accelerates to Mach 4.5, then scramjet to Mach 6 to Mach 7+. Tests are planned for 2007 – 2008 timeframe.
Discussion of Potential Cruise Missiles Capability Improvements
The following is a discussion of possible improvements that could be made to cruise missile
characteristics.
Response Time
–Response time can be reduced by moving the effective launch point closer to the target, e.g., launching from a manned (or perhaps unmanned) aircraft, using a loiter area from which to depart on cue, or using on-board ISR sensors to find and locate the target. However, moving closer to the target raises concerns of launch platform endurance, vulnerability and survivability.
Increasing speed of the cruise missile is another candidate area to reduce response time. It is difficult as of today to predict when and if a realistic super- or hypersonic capability for a U.S. cruise missile will be realized. It is often noted that other countries have developed supersonic cruise missiles, but these foreign weapons are mostly anti-ship missiles that are shorter range than what typically is expected for U.S. land attack cruise missiles. For example, a joint venture between India and Russia produced the BrahMos anti-
ship cruise missile with a range of 290 km (160 nm) and a speed of Mach 2.5+. This cruise missile became operational in 2006, and is believed to also have some land-attack capability.
The technological challenges of practical, long-range, land-attack cruise missiles in this speed regime go beyond propulsion area, which has understandably been the focus of high speed weapon experiments, demonstrations, and flight tests. Additional technical challenges for these high speed weapon concepts include thermal protection of the missile and payload, and communication techniques to allow the missile to receive in-flight navigation or targeting updates.
Terminal Guidance
– Improvements in terminal guidance could include several areas: better capabilities to guide to the assigned aimpoint; on-board sensors to autonomously detect, identify, locate, and track the target; or increased flexibility for operators to designate the target and guide the missile to it.
Flexible Target Set Capability
– Today, different payloads are required to effectively strike different targets. For example, much work is
being done on a warhead that is effective against hard and deeply buried targets. An ideal capability might allow changing the effective payload configuration (and attack profile, if appropriate) just before launch or perhaps even during flight that is customized for the target.
Range
– Currently, several long range cruise missiles can reach out to or beyond 1000 nm.
Trade-offs of payload size and desired response times can be conducted to consider longer range
“global strike” capable cruise missiles in the several thousand mile range.
Size
– A smaller cruise missile could have advantages of more flexibility for the launch platforms (e.g., smaller UAVs) and stealth. The trade-off of a smaller cruise missile is potential reduced capability, specifically a shorter range and smaller payload.
Cruise Missile
This section provides a brief, unclassified discussion of cruise missiles. It contains a summary of the principal attributes; provides a history; describes the technologies and characteristics of cruise missiles; gives brief descriptions of the cruise missiles that have been developed over the years; discusses the possible future of cruise missiles; and concludes with potential improvements.
Summary of Cruise Missile Attributes
• Pilotless, air-breathing (sometimes rocket powered), continuously powered, usually relatively low flying, guided using aerodynamic lift and control throughout flight.
Some cruise missiles (e.g., Tactical Tomahawk) have two way data links for missilestatus and retargeting.
• Payload is integrated as part of the airframe, with missile assumed destroyed at the end of the mission.
• Ranges can extend thousands of miles, with accuracies of tens of feet.
• Can be launched from land, sea surface and sub surface, and air.
• Payloads of conventional and nuclear warheads, other specialized cruise missile payloads considered, at least conceptually, include ISR systems/sensors and niche weapons concepts (non-kinetic weapons
, penetrators for HDBT, etc.).
• Speeds can be sub- or supersonic. Typical flight times range from tens of minutes to several hours.
History
Cruise missiles were first conceptualized in about 1891 by Sir Hiram Maxim, the inventor of the modern machine gun and a dabbler in flying machines. The first example of a cruise missile was the Kettering Bug, commonly known as an aerial torpedo. It was an unmanned biplane that flew in a straight line for a set period of time, detached its wings and struck the ground with the fuselage and warhead. Developed during World War I, it integrated aircraft guidance technologies developed by Elmer and Lawrence Sperry for a U.S. Army project led by Charles F. Kettering. The first flights occurred in the fall of 1918, but it was never used in war as WWI came to an end that November.
Between World War I and World War II both the British and Americans continued aerial torpedo development. The first launch of a cruise missile (called Larynx) from a destroyer at sea occurred in the 1920s. Prototype aircraft with names such as Hoop-la (British), various versions of Mistel (German), and TDR-1 (American) appeared during WWII with varying results. These all appeared similar to manned airplanes of the day.
The first cruise missile used in war was the German V-1 flying bomb. The V-1 was used in raids against England beginning in June 1944. . It had the appearance of a modern day cruise missile with a bomb-like fuselage and short wings and fins. It was small and cheap and was made and used in very large numbers with effect. Powered by a pulse jet engine and guided by an inertial guidance system, it flew at high speed and low altitude, and had a range of about 250, and later 400, kilometers (140 and 225 nm) with a warhead
of 800 kilograms (1760 pounds). Initially launched using a steam catapult from ground ramps, V-1s initially had metal wings (later changed to wood) with no control surfaces; instead employing tail fins and a rudder for control. Gyroscopes kept it stable, a magnetic compass controlled direction, and a barometric altimeter
controlled altitude. Powered after launch by a distinctive sounding pulse-jet engine, V-1’s used either a timing or a distance-estimating system to lock the control surfaces and pop out spoilers, which would put the missile into a steep dive. The V-1 used an electric fuse, but had mechanical and time-delay fuses for backup. By today’s standards, it was not accurate (it is believed half the V-1s fell roughly within four miles of the aim point), but it was accurate enough to spread terror in the city of London and the English countryside. The V-1 could be fitted with a nerve gas warhead, but this variant was never used. Other payloads did see some use: including 23 one-kilogram incendiary bomblets and a cardboard tube with propaganda leaflets.
Toward the end of the war, some V-1s were launched from specially modified Heinkel He-111 bombers. At least 30,000 were built during the World War II.
Cruise Missile Technologies
The V-1 story provides a quick introduction to the technologies that make cruise missiles work.
As the state of the art in these technologies evolved, the types used in cruise missiles changed.
Key technologies that form the basic components of cruise missiles are described in more detail
as follows:
• Propulsion and fuel (for both launch and flight): Most cruise missiles use a booster (usually a solid fuel rocket) for launch and a jet engine for sustained flight. The fuels used vary from one missile type to another.
• Aerodynamics (bodies, wings, and control surfaces): Nearly all cruise missiles use shapes and surfaces to maintain and control flight, as in manned aircraft.
• Guidance and Navigation: Today, most cruise missiles use some kind of INS, composed of gyros and accelerometers. Many modern cruise missiles employ an additional external data input to provide in-flight position updates to the INS to refine the navigator, thus significantly increasing the overall accuracy. Such data sources include updates from map or scene matching algorithms; in addition, nearly all modern cruise missiles use GPS for this purpose. Another external data source for navigation updates that is common to modern cruise missiles are altimeters (barometric, radar, and combined).
• Communications: As will be discussed later, several of today’s cruise missiles use in-flight communications. Some allow the missile to report its status and many allow controllers to change some aspect of the mission being flown (including designating a new target).
• Sensors: Some cruise missiles carry sensors, primarily radars and cameras. These
are used for navigation purposes or as ISR sensors.
• Payloads (kinetic and non-kinetic) and fuses: Most cruise missiles carry explosive warheads (conventional and nuclear), unitary bombs or smaller bomblets. Non-kinetic warhead concepts also exist, including biological and chemical constructs. The fuse activates the warhead, and fuse types include contact fuses (sometimes with fixed or selectable time delays), timing fuses, altimeter fuses, and distance measuring
fuses (as in the V-1).
Cruise Missile Characteristics
The primary characteristics of cruise missiles are provided below:
• Unmanned
• Speed and range: Although a few cruise missiles travel at more than the speed of sound, most are subsonic, usually high subsonic. Maximum ranges vary from a few 10s of miles to more than 1000 miles.
• Time of flight: Speed and range obviously combine to yield a time of flight to the target, which together with times for other links in the kill chain (ISR and C2 times) produces a total reaction time — the time it takes to search for, decide to strike, and hit a target. Most cruise missile flight times range from tens of minutes up to several hours (again dependent on speed and range to target).
• Flight Profile (altitude, maneuverability, etc.): Cruise missiles essentially are confined to altitudes of less than about 30,000 feet (although there are a few modern variants that can fly much higher during some portions of the flight profile). Many cruise missiles fly very close to the surface of the earth to avoid
detection and try to “hug” the terrain.
• Part of a cruise missile flight profile can include a loiter interval; this can be used to reduce the response time by reducing the time of flight for an emergent or time sensitive target or to redirect the missile with updated target information. The message to transition from a loitering posture to striking the target (or to a new target) can come via communications from an external “controller” or from an organic sensor on the missile.
• Accuracy: Many cruise missiles are coordinate-seeking weapons, i.e., they guide to the geographic coordinates (latitude, longitude, and altitude, usually in GPS coordinates) provided to them. There are cruise missiles with organic seekers/sensors of some type for improved targeting. Some cruise missiles can also be provided real-time direction from a human (man-in-the-loop,or MITL) for designated targets.
In general, accuracy has two contributing factors: target location error (TLE – not knowing exactly where the target is) and circular error probable (CEP – not being able to navigate and guide to the aimpoint, exactly
where the target is believed to be). CEP has two components: Navigation, which is how well the missile knows where it really is (depends on the type and quality of the navigation system), and guidance, that is, how well the missile can guide to where it wants to be (depends on the maneuverability and controllability of the missile). Accuracy errors are associated with all three spatial dimensions. For coordinate-seeking cruise missiles, GPS alone can produce accuracies with miss distances of several 10s of
feet. Other update techniques can achieve improved accuracies, especially approaches that combine INS with external sources such as GPS.
• Launch platforms: Cruise missiles can be launched from ships, submarines, aircraft, and land sites. Special launchers are often needed, although some submarines use normal torpedo tubes and some aircraft can use existing pylons. A system is required on the launch platform or near the launch point to transport, store, power up, and initialize the missile prior to launch.
• Sensors: Cruise missiles often have sensors associated with their navigation systems, including the TERCOM radars, DSMAC cameras, or other position update sensors.Tactical Tomahawk also uses the DSMAC camera to record battle damage indication images of previous strikes at preplanned locations as the missile flies over. Other sensors can include devices intended to detect, identify, locate, and sometimes home on the missile’s target.
• Reliability: This is a measure of the probability that the cruise missile will successfully achieve the desired effect. Typically reliability is the cumulative probability of successful initialization, launch, flight, control, and warhead detonation. Reliability (and accuracy) are often used in determining numbers of missiles required to achieve an overall desired effect on a given target.
Cruise Missiles – Past, Present, and Future
The following is a brief discussion of cruise missile evolution after WWII. Immediately after the war, and even during the last stages of the war, the U.S. Air Force, the U.S. Navy and the Soviet military built their own cruise missiles based on the V-1, and the U.S. Army tried its own “flyingwing” design. Most launches were from the ground, but air-launched, surface ship-launched and even submarine-launched cruise missiles were explored by the services.
Cruise Missiles from the 50s and 60s
From the late 1940s through the end of the 1960s, many efforts were made to develop guided missiles in general, and guided cruise missiles in particular. While these efforts made progress in understanding the key technical issues and maturing the required technologies, they did not succeed in producing a practical cruise missile. Most of these missile concepts were supersonic with ranges of up to several thousand miles (that consequently resulted in very large missile sizes and weights). Many of these early Cold War cruise missile concepts had significant challenges in flight control, guidance and navigation, and overall reliability. Early missiles and programs included the USAF’s Matador, Mace, Snark, Hound Dog, Crossbow, Navaho, Buck Duck, Bull Goose, and Quail; and the USN’s Regulus series, Rigel, and Triton.
Modern Cruise Missiles (from the 70s to the present)
By the late 1960s, the various key technologies required by cruise missiles had matured enough such that operationally useful cruise missiles became practical and affordable. These technologies included developments in improved accuracy of gyros and accelerometers and smaller, more powerful computers. With these advances, developments began in earnest of cruise missiles that became operational, and several remain in service today, as described as provided below.
• Harpoon (AGM/RGM/UGM-84A) – USN/USAF. Air-, ship-, and sub-launched anti-ship cruise missile. It originally used a heading reference system and a radar seeker to find and guide to the target. Operational range was initially about 60 nm. Harpoon operational deployments started in 1977 and continue to this day.
• Tomahawk (RGM/UGM 109A/B/C/D/E) Sea-Launched Cruise Missile (SLCM) – US and UK navies. The A variant had a nuclear warhead for striking very distant land targets, and the B variant was an anti-ship missile (similar to Harpoon) with an operational range of about 250 nm. Neither are operational today. The C and E
variants have large unitary warheads and the D variant has small bomblets that can be distributed over one or more areas. The E is called Tactical Tomahawk, which is less expensive and has, among other things, two-way communications, including redirection of the missile after launch. The C and E variants have ranges of about 900nm. The Tomahawk series started in the early 1980s and continues to evolve today.
• ALCM (AGM-86A/B/C/D) Air-Launched Cruise Missile – USAF. The A and B variants had nuclear warheads, and the C and D are conventional (called CALCMs). The C has a unitary blast fragmentation warhead, and D has a penetrator warhead.The ranges are about 750 miles. Initially operated in the early 1980s, it remains
operational today.
• ACM (AGM-129A/B) Advanced Cruise Missile – USAF. These air-launched cruise missiles have nuclear warheads, have longer range capability (1865 mi) than the ALCM and CALCM missiles, and use stealth technology.
• SLAM – ER (AGM-84K) Standoff Land Attack Missile-Expanded Response – This missile is an evolution of Harpoon (AGM-84A) and SLAM (AGM-84E). The SLAM– ER is air-launched with GPS-aided inertial navigation, has an imaging infrared seeker and fire-and-forget or MITL (with two-way AWW-13 communications pod) for target selectivity and moving target capability.
• TSSAM (AGM-137) Tri-Service Standoff Attack Missile – USAF/USN. Air-launched cruise missile with conventional warhead and 600nm range. Cancelled in EMD phase and essentially replaced by the JASSM program.
• JASSM (AGM-158), Joint Air to Surface Standoff Missile – USAF/USN. Air-launched, 250 nm nominal
range, GPS-aided navigation and an imaging infrared seeker in terminal phase, an automatic target correlator, and a penetrating warhead. The JASSM has a one-way bomb impact assessment transmission viacommunications link.
Before and during these same years, other countries began to develop cruise missiles, many of which saw use in conflict and remain operational today. As would be expected, the Russians have developed a variety of cruise missiles. The sinking of the Israeli destroyer Eilat in 1967 by a Soviet-built Styx anti-ship cruise missile is often credited with renewing the USN’s interest in cruise missiles. While there are many examples
of foreign cruise missiles, most are relatively short range. France has developed a family of cruise missiles known by various names depending on their specific attributes (including the country that deploys it) such as APACHE, Scalp, and Storm Shadow. These French missiles are air-launched, land attack, standoff (i.e.,
relatively short range) weapons, with GPS-INS navigation and terrain following capability.
Sweden and Germany have together developed a land attack missile called Taurus, with terrain-matching navigation, an imaging IR seeker and a range of nearly 300 nm. Israel developed Delilah, again with GPS-INS, a datalink, a seeker, and a loiter capability with a nominal range of 150 nm.
Planned Cruise Missiles in Near Term
There is a continued desire to improve capabilities of cruise missiles by making them faster, better (range, accuracy, etc), cheaper, smaller, and easier to operate. Cruise missiles planned (that is in the program of record or being considered) for the near future include:
• Future Tactical Tomahawk – USN. Includes improvements in C2 and interoperability, more robust datalink, a multiple effects warhead, PTAN for GPS-independent navigation updates, ASUW, and mobile target capabilities. New launch platforms: include SSGN and DDG 1000. Possible Block V upgrade with high speed
capabilities are also under consideration.
• JASSM-ER – USAF. Range of 500 nm with new engine, two-way datalink including capability for target update in flight. Includes planning for an anti-ship capability (2011 for JASSM-ER and 2012 for JASSM).
• JASSM–XR – USAF. Extra Extended Range version being considered with range up to1000 nm. Launch platform would include bombers and heavy strike aircraft.
• Affordable Weapon – USN. As the name implies, a less expensive (<$30K) capable “cruise-like” missile. Missile concept is rocket launched from a shipping container and powered in flight by a small turbojet engine with in-flight retargeting using a two way data-link. This missile would have a loitering capability and a payload of up to 200 pounds with a maximum range of up to about 800 nm.
• RATTLRS, Revolutionary Approach to Time Critical Long Range Strike – USN, USAF, NASA. This is a technology demonstration that is part of the National Aerospace Initiative and sponsored in part by Office of Naval Research (ONR). This concept has a turbine engine that operates at Mach 3.0 for about 5 minutes. It could be air-launched, as well as ship- and sub-launched.
• LOCAAS, Low Cost Autonomous Attack System – AFRL. This is a miniature airvehicle with a laser radar seeker, smart targeting algorithms, and a multi-purpose warhead. Intended to be employed against
moving/relocatable targets and capable of multi-missile swarming tactics.
• SMACM, Surveilling Miniature Attack Cruise Missile – USAF. A proposal based on LOCAAS and Joint Common Missile technologies to be built from affordable, off-the-shelf components. Essential concept is a loitering, stand-off weapon that searches for targets with its on-board sensors.
During the past decade, there has been an increased emphasis on concept development, experimentation, and demonstrations aimed toward building a practical supersonic or hypersonic capability for aircraft and cruise missiles. Some relevant high-speed demonstration programs are described as follows:
• Fasthawk, Low Cost Missile System (LCMS) Advanced Rapid Response Missile Demonstrator (ARRMD) – ONR. This Advanced Technology Demonstration (ATD) was conducted in 1997 and 1998. Missile characteristics included a bending body, a rocket booster with ramjet engine that would have a 700 nm range and speeds of up to Mach 4.0. While LCMS terminated in 1998, this effort evolved into what became the
HyFly concept.
• HyFly – DARPA/ONR. This is a hypersonic flight demonstration program using a dual combustion ramjet propulsion concept. Additional attributes of HyFly include high-temperature materials and hypersonic guidance and control. Concept variants would include surface ship, submarine, and air-launched missiles with ranges of about 600 nm, at speeds up to and greater than Mach 6.0.
• HyTech (Hypersonic Technology) – AFRL. This is a scramjet research and test
program that is examining speeds of Mach 4.5 to Mach 6.5.
•JSSCM, Joint Supersonic Cruise Missile– DTRA/OSD/OPNAV. Came out of an April 2002 solicitation for a supersonic cruise missile ACTD that had a range of 400 nm and would operate at Mach 3.5 to Mach 4.5 with a CEP of 3 m.
• FALCON, Hypersonic Force Application and Launch from CONUS –DARPA/USAF. A reusable hypersonic
cruise vehicle that can carry several munitions, including cruise missiles and bombs.
• X-43A (Hyper-X) – NASA. A cruise missile size, unmanned, air-breathing, hypersonic flight research aircraft, with speeds of Mach 7 to Mach10. This aircraft reached sustained speeds of Mach 6.8 in March 2004 and Mach 9.6 in November 2004 at an altitude of near 100,000 feet.
• X-51 (Waverider) – AFRL. An air-launched hypersonic cruise missile for the B-52. Concept has launching aircraft at 35,000 ft. The missile’s solid rocket booster accelerates to Mach 4.5, then scramjet to Mach 6 to Mach 7+. Tests are planned for 2007 – 2008 timeframe.
Discussion of Potential Cruise Missiles Capability Improvements
The following is a discussion of possible improvements that could be made to cruise missile
characteristics.
Response Time
–Response time can be reduced by moving the effective launch point closer to the target, e.g., launching from a manned (or perhaps unmanned) aircraft, using a loiter area from which to depart on cue, or using on-board ISR sensors to find and locate the target. However, moving closer to the target raises concerns of launch platform endurance, vulnerability and survivability.
Increasing speed of the cruise missile is another candidate area to reduce response time. It is difficult as of today to predict when and if a realistic super- or hypersonic capability for a U.S. cruise missile will be realized. It is often noted that other countries have developed supersonic cruise missiles, but these foreign weapons are mostly anti-ship missiles that are shorter range than what typically is expected for U.S. land attack cruise missiles. For example, a joint venture between India and Russia produced the BrahMos anti-
ship cruise missile with a range of 290 km (160 nm) and a speed of Mach 2.5+. This cruise missile became operational in 2006, and is believed to also have some land-attack capability.
The technological challenges of practical, long-range, land-attack cruise missiles in this speed regime go beyond propulsion area, which has understandably been the focus of high speed weapon experiments, demonstrations, and flight tests. Additional technical challenges for these high speed weapon concepts include thermal protection of the missile and payload, and communication techniques to allow the missile to receive in-flight navigation or targeting updates.
Terminal Guidance
– Improvements in terminal guidance could include several areas: better capabilities to guide to the assigned aimpoint; on-board sensors to autonomously detect, identify, locate, and track the target; or increased flexibility for operators to designate the target and guide the missile to it.
Flexible Target Set Capability
– Today, different payloads are required to effectively strike different targets. For example, much work is
being done on a warhead that is effective against hard and deeply buried targets. An ideal capability might allow changing the effective payload configuration (and attack profile, if appropriate) just before launch or perhaps even during flight that is customized for the target.
Range
– Currently, several long range cruise missiles can reach out to or beyond 1000 nm.
Trade-offs of payload size and desired response times can be conducted to consider longer range
“global strike” capable cruise missiles in the several thousand mile range.
Size
– A smaller cruise missile could have advantages of more flexibility for the launch platforms (e.g., smaller UAVs) and stealth. The trade-off of a smaller cruise missile is potential reduced capability, specifically a shorter range and smaller payload.
