Communication with submarines

Last updated

Communication with submarines is a field within military communications that presents technical challenges and requires specialized technology. Because radio waves do not travel well through good electrical conductors like salt water, submerged submarines are cut off from radio communication with their command authorities at ordinary radio frequencies. Submarines can surface and raise an antenna above the sea level, or float a tethered buoy carrying an antenna, then use ordinary radio transmissions; however, this makes them vulnerable to detection by anti-submarine warfare forces.

Contents

Early submarines during World War II mostly travelled on the surface because of their limited underwater speed and endurance, and dived mainly to evade immediate threats or for stealthy approach to their targets. During the Cold War, however, nuclear-powered submarines were developed that could stay submerged for months.

In the event of a nuclear war, submerged ballistic missile submarines have to be ordered quickly to launch their missiles. Transmitting messages to these submarines is an active area of research. Very low frequency (VLF) radio waves can penetrate seawater just over one hundred feet (30 metres), and many navies use powerful shore VLF transmitters for submarine communications. A few nations have built transmitters which use extremely low frequency (ELF) radio waves, which can penetrate seawater to reach submarines at operating depths, but these require huge antennas. Other techniques that have been used include sonar and blue lasers. [1]

Acoustic transmission

Sound travels far in water, and underwater loudspeakers and hydrophones can cover quite a gap. Apparently, both the American (SOSUS) and the Russian navies have placed sonic communication equipment in the seabed of areas frequently travelled by their submarines and connected it by underwater communications cables to their land stations. If a submarine hides near such a device, it can stay in contact with its headquarters. An underwater telephone sometimes called Gertrude is also used to communicate with submersibles.

Very low frequency

VLF radio waves (3–30  kHz) can penetrate seawater to a few tens of metres and a submarine at shallow depth can use them to communicate. A deeper vessel can use a buoy equipped with an antenna on a long cable. The buoy rises to a few metres below the surface, and may be small enough to remain undetected by enemy sonar and radar. However these depth requirements restrict submarines to short reception periods, and antisubmarine warfare technology may be capable of detecting the sub or antenna buoy at these shallow depths.

Natural background noise increases as frequency decreases, so a lot of radiated power is required to overcome it. Worse, small antennas (relative to a wavelength) are inherently inefficient. This implies high transmitter powers and very large antennas covering square kilometres. This precludes submarines from transmitting VLF, but a relatively simple antenna (usually a long trailing wire) will suffice for reception. Hence, VLF is always one-way, from land to boat. If two-way communication is needed, the boat must ascend nearer to the surface and raise an antenna mast to communicate on higher frequencies, usually HF and above.

Because of the narrow bandwidths available, voice transmission is impossible; only slow data is supported. VLF data transmission rates are around 300 bits/sec, so data compression is essential.

Only a few countries operate VLF facilities for communicating with their submarines: Norway, United States, Russia, United Kingdom, Germany, Australia, Pakistan, and India.

Extremely low frequency

1982 aerial view of the US Navy Clam Lake, Wisconsin ELF facility Clam Lake ELF.jpg
1982 aerial view of the US Navy Clam Lake, Wisconsin ELF facility

Electromagnetic waves in the ELF and SLF frequency ranges (3–300  Hz) can penetrate seawater to depths of hundreds of metres, allowing signals to be sent to submarines at their operating depths. Building an ELF transmitter is a formidable challenge, as they have to work at incredibly long wavelengths: The U.S. Navy's Project ELF system, which was a variant of a larger system proposed under codename Project Sanguine, [2] operated at 76  hertz, [3] and the Soviet/Russian system (called ZEVS ) at 82 Hertz. [4] The latter corresponds to a wavelength of 3,656.0 kilometres. That is more than a quarter of the Earth's diameter. Obviously, the usual half-wavelength dipole antenna cannot be feasibly constructed, as that would require a 1,800 km (1,100 mi) long antenna.

Instead, someone who wishes to construct such a facility has to find an area with very low ground conductivity (a requirement opposite to usual radio transmitter sites), bury two huge electrodes in the ground at different sites, and then feed lines to them from a station in the middle, in the form of wires on poles. Although other separations are possible, the distance used by the ZEVS transmitter located near Murmansk is 60 kilometres (37 miles). As the ground conductivity is poor, the current between the electrodes will penetrate deep into the Earth, essentially using a large part of the globe as an antenna. The antenna length in Republic, Michigan, was approximately 52 kilometers (32 mi). The antenna is very inefficient. To drive it, a dedicated power plant seems to be required, although the power emitted as radiation is only a few watts. Its transmission can be received virtually anywhere. A station in Antarctica at 78° S 167° W detected transmission when the Soviet Navy put their ZEVS antenna into operation. [4]

Owing to the technical difficulty of building an ELF transmitter, the U.S., [3] China, [5] Russia, [4] and India [6] [7] are the only nations known to have constructed ELF communication facilities:

ELF transmissions

The coding used for U.S. military ELF transmissions employed a Reed–Solomon error correction code using 64 symbols, each represented by a very long pseudo-random sequence. The entire transmission was then encrypted. The advantages of such a technique are that by correlating multiple transmissions, a message could be completed even with very low signal-to-noise ratios, and because only a very few pseudo-random sequences represented actual message characters, there was a very high probability that if a message was successfully received, it was a valid message (anti-spoofing).

The communication link is one-way. No submarine could have its own ELF transmitter on board, due to the sheer size of such a device. Attempts to design a transmitter which can be immersed in the sea or flown on an aircraft were soon abandoned.

Owing to the limited bandwidth, information can only be transmitted very slowly, on the order of a few characters per minute (see Shannon’s coding theorem). Thus it was only ever used by the US Navy to give instructions to establish another form of communication [9] and it is reasonable to assume[ why? ] that the actual messages were mostly generic instructions or requests to establish a different form of two-way communication with the relevant authority.[ citation needed ]

Standard radio technology

A surfaced submarine, or a submarine floating a tethered antenna buoy on the surface, can use ordinary radio communications. From the surface, submarines may use naval frequencies in the HF, VHF, and UHF bands, and transmit information via both voice and teleprinter modulation techniques. Where available, dedicated military communications satellite systems using line-of-sight frequencies are preferred for long distance communications, as HF are more likely to betray the location of the submarine. The U.S. Navy's system is called Submarine Satellite Information Exchange Sub-System (SSIXS), a component of the Navy Ultra High Frequency Satellite Communications System (UHF SATCOM).

Combining acoustic and radio transmissions

A recent technology developed by a team at MIT combines acoustic signals and radar to enable submerged submarines to communicate with airplanes. [10] An underwater transmitter uses an acoustic speaker pointed upward to the surface. The transmitter sends multichannel sound signals, which travel as pressure waves. When these waves hit the surface, they cause tiny vibrations. Above the water, a radar, in the 300 GHz range, continuously bounces a radio signal off the water surface. When the surface vibrates slightly due to the sound signal, the radar can detect the vibrations, completing the signal's journey from the underwater speaker to an in-air receiver. [11] The technology is called TARF (Translational Acoustic-RF) communication since it uses a translation between acoustic and RF signals. While promising, this technology is still in its infancy and has only been successfully tested in relatively controlled environments with small, up to approximately 200 mm, surface ripples, while larger waves prevented successful data communication.

Underwater modems

In April 2017, NATO's Centre for Maritime Research and Experimentation announced [12] the approval of JANUS, a standardised protocol to transmit digital information underwater using acoustic sound (as modems with acoustic couplers did in order to make use of analogue telephone lines). [13] Documented in STANAG 4748, it uses 900 Hz to 60 kHz frequencies at distances of up to 28 kilometres (17 mi). [14] [15] It is available for use with military and civilian, NATO and non-NATO devices; it was named after the Roman god of gateways, openings, etc.

Blue lasers

In 2009, a US military report stated that "Practical laser-based systems for deep depths were unavailable because lasers operating at the right colour with enough power efficiency to be used in satellites did not exist. DARPA is striving towards a blue laser efficient enough to make submarine laser communications at depth and speed a near-term reality. A recently demonstrated laser will be matched with a special optical filter to form the core of a communications system with a signal-to-noise ratio thousands of times better than other proposed laser systems. If DARPA can demonstrate such a system under realistic conditions, it would dramatically change how submarines can communicate and operate, thereby greatly enhancing mission effectiveness, for example, in anti-submarine warfare." [1]

See also

Related Research Articles

Ground waves are radio waves propagating parallel to and adjacent to the surface of the Earth, following the curvature of the Earth beyond the visible horizon. This radiation is known as Norton surface wave, or more properly Norton ground wave, because ground waves in radio propagation are not confined to the surface.

<span class="mw-page-title-main">Transmission medium</span> Conduit for signal propagation

A transmission medium is a system or substance that can mediate the propagation of signals for the purposes of telecommunication. Signals are typically imposed on a wave of some kind suitable for the chosen medium. For example, data can modulate sound, and a transmission medium for sounds may be air, but solids and liquids may also act as the transmission medium. Vacuum or air constitutes a good transmission medium for electromagnetic waves such as light and radio waves. While a material substance is not required for electromagnetic waves to propagate, such waves are usually affected by the transmission media they pass through, for instance, by absorption or reflection or refraction at the interfaces between media. Technical devices can therefore be employed to transmit or guide waves. Thus, an optical fiber or a copper cable is used as transmission media.

<span class="mw-page-title-main">Radio wave</span> Type of electromagnetic radiation

Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1mm, which is shorter than the diameter of a grain of rice. At 30 Hz the corresponding wavelength is ~10,000 kilometers, which is longer than the radius of the Earth. Wavelength of a radio wave is inversely proportional to its frequency, because its velocity is constant. Like all electromagnetic waves, radio waves in a vacuum travel at the speed of light, and in the Earth's atmosphere at a slightly slower speed. Radio waves are generated by charged particles undergoing acceleration, such as time-varying electric currents. Naturally occurring radio waves are emitted by lightning and astronomical objects, and are part of the blackbody radiation emitted by all warm objects.

<span class="mw-page-title-main">Very low frequency</span> The range 3–30 kHz of the electromagnetic spectrum

Very low frequency or VLF is the ITU designation for radio frequencies (RF) in the range of 3–30 kHz, corresponding to wavelengths from 100 to 10 km, respectively. The band is also known as the myriameter band or myriameter wave as the wavelengths range from one to ten myriameters. Due to its limited bandwidth, audio (voice) transmission is highly impractical in this band, and therefore only low data rate coded signals are used. The VLF band is used for a few radio navigation services, government time radio stations and for secure military communication. Since VLF waves can penetrate at least 40 meters (131 ft) into saltwater, they are used for military communication with submarines.

Low frequency (LF) is the ITU designation for radio frequencies (RF) in the range of 30–300 kHz. Since its wavelengths range from 10–1 km, respectively, it is also known as the kilometre band or kilometre wave.

<span class="mw-page-title-main">Longwave</span> Radio transmission using wavelengths above 1000 m

In radio, longwave, long wave or long-wave, and commonly abbreviated LW, refers to parts of the radio spectrum with wavelengths longer than what was originally called the medium-wave broadcasting band. The term is historic, dating from the early 20th century, when the radio spectrum was considered to consist of longwave (LW), medium-wave (MW), and short-wave (SW) radio bands. Most modern radio systems and devices use wavelengths which would then have been considered 'ultra-short'.

<span class="mw-page-title-main">High frequency</span> The range 3-30 MHz of the electromagnetic spectrum

High frequency (HF) is the ITU designation for the range of radio frequency electromagnetic waves between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters. Frequencies immediately below HF are denoted medium frequency (MF), while the next band of higher frequencies is known as the very high frequency (VHF) band. The HF band is a major part of the shortwave band of frequencies, so communication at these frequencies is often called shortwave radio. Because radio waves in this band can be reflected back to Earth by the ionosphere layer in the atmosphere – a method known as "skip" or "skywave" propagation – these frequencies are suitable for long-distance communication across intercontinental distances and for mountainous terrains which prevent line-of-sight communications. The band is used by international shortwave broadcasting stations (3.95–25.82 MHz), aviation communication, government time stations, weather stations, amateur radio and citizens band services, among other uses.

Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. Understanding the effects of varying conditions on radio propagation has many practical applications, from choosing frequencies for amateur radio communications, international shortwave broadcasters, to designing reliable mobile telephone systems, to radio navigation, to operation of radar systems.

<span class="mw-page-title-main">Extremely low frequency</span> The range 3-30 Hz of the electromagnetic spectrum

Extremely low frequency (ELF) is the ITU designation for electromagnetic radiation with frequencies from 3 to 30 Hz, and corresponding wavelengths of 100,000 to 10,000 kilometers, respectively. In atmospheric science, an alternative definition is usually given, from 3 Hz to 3 kHz. In the related magnetosphere science, the lower-frequency electromagnetic oscillations are considered to lie in the ULF range, which is thus also defined differently from the ITU radio bands.

Super low frequency (SLF) is the ITU designation for electromagnetic waves in the frequency range between 30 hertz and 300 hertz. They have corresponding wavelengths of 10,000 to 1,000 kilometers. This frequency range includes the frequencies of AC power grids. Another conflicting designation which includes this frequency range is Extremely Low Frequency (ELF), which in some contexts refers to all frequencies up to 300 hertz.

<span class="mw-page-title-main">Grimeton Radio Station</span> Historic Swedish wireless telegraphy station

Grimeton Radio Station in southern Sweden, close to Varberg in Halland, is an early longwave transatlantic wireless telegraphy station built in 1922–1924, that has been preserved as a historical site. From the 1920s through the 1940s it was used to transmit telegram traffic by Morse code to North America and other countries, and during World War II was Sweden's only telecommunication link with the rest of the world. It is the only remaining example of an early pre-electronic radio transmitter technology called an Alexanderson alternator. It was added to the UNESCO World Heritage List in 2004, with the statement: "Grimeton Radio Station, Varberg is an outstanding monument representing the process of development of communication technology in the period following the First World War." The radio station is also an anchor site for the European Route of Industrial Heritage. The transmitter is still in operational condition, and each year on a day called Alexanderson Day is started up and transmits brief Morse code test transmissions, which can be received all over Europe.

Goliath transmitter was a very low frequency (VLF) transmitter for communicating with submarines, built by Nazi Germany's Kriegsmarine navy near Kalbe an der Milde in Saxony-Anhalt, Germany, which was in service from 1943 to 1945. It was capable of transmission power of between 100 and 1000 kW and was the most powerful transmitter of its time.

<span class="mw-page-title-main">Umbrella antenna</span>

An umbrella antenna is a capacitively top-loaded wire monopole antenna, consisting in most cases of a mast fed at the ground end, to which a number of radial wires are connected at the top, sloping downwards. One side of the feedline supplying power from the transmitter is connected to the mast, and the other side to a ground (Earthing) system of radial wires buried in the earth under the antenna. They are used as transmitting antennas below 1 MHz, in the MF, LF and particularly the VLF bands, at frequencies sufficiently low that it is impractical or infeasible to build a full size quarter-wave monopole antenna. The outer end of each radial wire, sloping down from the top of the antenna, is connected by an insulator to a supporting rope or cable anchored to the ground; the radial wires can also support the mast as guy wires. The radial wires make the antenna look like the wire frame of a giant umbrella hence the name.

<span class="mw-page-title-main">Ground dipole</span> Radio antenna that radiates extremely low frequency electromagnetic waves

In radio communication, a ground dipole, also referred to as an earth dipole antenna, transmission line antenna, and in technical literature as a horizontal electric dipole (HED), is a huge, specialized type of radio antenna that radiates extremely low frequency (ELF) electromagnetic waves. It is the only type of transmitting antenna that can radiate practical amounts of power in the frequency range of 3 Hz to 3 kHz, commonly called ELF waves. A ground dipole consists of two ground electrodes buried in the earth, separated by tens to hundreds of kilometers, linked by overhead transmission lines to a power plant transmitter located between them. Alternating current electricity flows in a giant loop between the electrodes through the ground, radiating ELF waves, so the ground is part of the antenna. To be most effective, ground dipoles must be located over certain types of underground rock formations. The idea was proposed by U.S. Dept. of Defense physicist Nicholas Christofilos in 1959.

<span class="mw-page-title-main">VLF Transmitter Cutler</span> VLF radio transmitter operated by the US Navy

The VLF Transmitter Cutler is the United States Navy's very low frequency (VLF) shore radio station at Cutler, Maine. The station provides one-way communication to submarines of the Navy's Atlantic Fleet, both on the surface and submerged. It transmits with call sign NAA, at a frequency of 24 kHz and input power of up to 1.8 megawatts, and is one of the most powerful radio transmitters in the world.

<span class="mw-page-title-main">Radio</span> Technology of using radio waves to carry information

Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves. They are received by another antenna connected to a radio receiver. In addition to communication, radio is used for radar, radio navigation, remote control, remote sensing, and other applications.

<span class="mw-page-title-main">Project Sanguine</span> US Navy research on communicating with submarines

Project Sanguine was a US Navy project proposed in 1968 for communication with submerged submarines using extremely low frequency (ELF) radio waves. The initially proposed system, hardened to survive a nuclear attack, would have required a giant antenna covering two-fifths of the state of Wisconsin. The proposed approach was never implemented because of protests and potential environmental impact. A smaller, less hardened system called Project ELF consisting of two linked ELF transmitters located at Clam Lake, Wisconsin 46°05′05.6″N90°55′03.7″W and Republic, Michigan 46°20′10.1″N87°53′04.6″W was built beginning in 1982 and operated from 1989 until 2004. The system transmitted at a frequency of 76 Hz. At ELF frequencies, the bandwidth of the transmission was very small, so the system could only send short-coded text messages at a very low data rate. These signals were used to summon specific vessels to the surface to receive longer operational orders by ordinary radio or satellite communication.

Naval Radio Transmitter Facility Aguada is a tall guyed radio mast erected by the United States Navy. It is used as a facility of the US Navy for ashore and U.S. and NATO ships, planes, and submarines operating at sea in areas of broadcast coverage near Aguada, Puerto Rico at 18°23′55″N67°10′38″W by using radio waves in the very low frequency range.

Through-the-Earth (TTE) signalling is a type of radio signalling used in mines and caves that uses low-frequency waves to penetrate dirt and rock, which are opaque to higher-frequency conventional radio signals.

<span class="mw-page-title-main">Sainte-Assise transmitter</span> Radio transmitter in France

The Sainte-Assise transmitter is a very low frequency (VLF) radio transmitter and military installation located on the grounds of the Château de Sainte-Assise in the communes of Seine-Port, Boissise-la-Bertrand, and Cesson in the Seine-et-Marne department of the Île-de-France region of France. The transmitter's original equipment was inaugurated on 9 January 1921, at the time being the most powerful radio transmitter on Earth. On 26 November 1921 the first French radio program was transmitted from Sainte-Assise. In 1965 the transmitter was used to send VLF signals to FR-1, the first French satellite. Since 1998 the French Navy has used the transmitter to communicate with submerged submarines.

References

  1. 1 2 DARPA Strategic Plan (PDF) (Report). Defense Advanced Research Projects Agency. May 2009. p. 18. Archived (PDF) from the original on 21 January 2022. Retrieved 25 October 2021.
  2. 1 2 Altgeit, Carlos A. (20 October 2005). "The world's largest radio station" (PDF) (Press release). University of Wisconsin . Retrieved 1 September 2013.
  3. 1 2 3 "Extremely Low Frequency Transmitter Site Clam Lake, Wisconsin" (PDF). U.S. Navy. 8 April 2003. Retrieved 5 May 2017.
  4. 1 2 3 4 Jacobsen, Trond. "ZEVS, the Russian 82 Hz ELF transmitter". ALFLAB. Halden, Norway.
  5. 1 2 "China's NYC-sized 'earthquake warning system' array sounds more like a way to talk to submarines". The War Zone. thedrive.com. 31 December 2018.
  6. 1 2 "Navy gets new facility to communicate with nuclear submarines prowling underwater". The Times of India . 31 July 2014.
  7. 1 2 "India makes headway with ELF site construction". Janes.com. Latest defence and security news. Janes Information Services.
  8. ↑ "India to be second country to use ELF facility". The Hindu . 20 May 2017. ISSN   0971-751X . Retrieved 14 December 2019.
  9. ↑ Friedman, Norman (1997). The Naval Institute guide to world naval weapons systems, 1997-1998. New York, NY: Naval Institute Press. pp. 41–42. ISBN   1-55750-268-4 – via Google Books.
  10. ↑ Tonolini, Francesco; Adib, Fadel. "TARF, wireless communication from underwater to the air". TARF (Press release). Massachusetts Institute of Technology.
  11. ↑ Koziol, Michael (24 August 2018). "TARF, MIT researchers develop seamless underwater-to-air communication system". IEEE Spectrum . Institute of Electrical and Electronics Engineers.
  12. ↑ "A new era of digital underwater communications" (Press release). North Atlantic Treaty Organization. 27 April 2017.
  13. ↑ "JANUS Community Wiki".
  14. ↑ Brown, Eric (15 August 2017). "The internet of underwater things: Open source JANUS standard for undersea communications". Linux.com (Press release). The Linux Foundation.
  15. ↑ Nacini, Francesca (4 May 2017). "JANUS creates a new era for digital underwater communications". Robohub.org.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.