The maritime domain is also roamed by
unmanned systems, including unmanned surface vehicles (USVs) and unmanned
underwater vehicles (UUVs). In the civilian sector, unmanned maritime technology
is used for such applications as oceanography, environmental research, search
and rescue, and even archeology. However, the main driving force for unmanned maritime
systems (UMS) are military applications, which include intelligence,
surveillance and reconnaissance (ISR), mine countermeasures (MCM), and
anti-submarine warfare (ASW). While a lot of applications of unmanned maritime
systems are still in their infancy, UMS technology is advancing rapidly and
constantly improving.
The use of the USVs in the ASW
missions can offer many advantages. USVs have the capability to perform these
dangerous missions without putting human lives in danger. USVs can be designed
with greater endurance, allowing them to perform their missions with longer
periods without refueling. The USVs are capable of carrying large payloads and
sensor suites. The design of USV can be stealthier which would allow the vessel
to perform covert operations. USVs can be built for high speed operations
allowing them to track and follow enemy submarines while still being small and
quite making them difficult to detect.
In the article “Ghost
ship: stepping aboard Sea Hunter, the Navy’s unmanned drone ship”, by Rick
Stella, published in April of 2016, the author talks about the new unmanned
surface vehicle (USV) being built by the United States Navy. The Sea Hunter USV
is developed by the Defense
Advanced Research Projects Agency (DARPA) and is
built under the
named Anti-Submarine Warfare (ASW) Continuous Trail Unmanned Vessel (ACTUV).
The
ACTUV program is designed to accomplish several goals:
·
The
first goal is to design a fully autonomous vessel, where aa a human is never
intended to operate aboard at any point of the mission. This kind of autonomy
will reduce life-support requirements and decrease constraints on conventional ship
construction components such as accessibility, layout, crew support arrangements,
and reserve buoyancy.
·
The
second goal is to develop the propulsion system of the vessel, which is able to
exceed the speeds of diesel electric submarines and at the same time be cost
efficient.
·
The
third goal is to design a high endurance vessel, which can operate over
thousands of miles with several month endurance with minimal control
intervention from the human operator. The USV should be able to autonomously
comply with maritime laws and conventions for safe navigation, perform autonomous
system supervision for operational reliability, and perform autonomous
interactions with an enemy (Littlefield, n.d.).
Figure 1. The Sea
Hunter USV. Adapted from “Ghost ship: Stepping aboard Sea Hunter, the Navy’s
unmanned drone ship,” by R. Stella, 2016. Technology
Trends. Copyright by DARPA.
The
Sea Hunter is originally designed to detect and track quiet diesel electric
submarines. However, with its large available payload capacity, the vessel will
be capable of performing a wide variety of missions. Currently, the Sea Hunter
is in its trial stage, and it is truly the vessel of the future.
The USV is quite large,
measuring 132 feet long with 145-ton displacement (Stella, 2016). The ship has a fiberglass composite exterior and a foam
core. It has a narrow body construction and is designed to travel at speeds up
to 27 knots. The pontoons
on both sides of the vessel provide stability. The outriggers attached to the
main vessel are used to absorb stress. The sturdy Sea Hunter is built to
perform its mission through Sea State 7 (wave heights of up to 20 feet). The
vessel is also capable of long endurance operations. It is able to carry up to 40 tons of diesel fuel, which can supply up to three months
of autonomous mission time (Courtland, 2016).
The
Sea Hunter is designed to be fully autonomous. It incorporates the Sparse
Supervisory Control architecture, which does not require a human operator to
interfere, except for emergency situations. From the moment the ship is
launched from the dock, it can autonomously commence its operations, avoiding
obstacles and activating its payloads to accomplish its main goal- ASW mission.
To seamlessly perform its tasks, the ship must comply with the Convention on the International Regulations for
Preventing Collisions at Sea (Stella, 2016). The Sea Hunter uses its onboard radar and an automatic ship
identification system, which
allows it to automatically detect vessels and obstacles, and maneuver to avoid
the collision in all weather conditions, day and night. The ACTUV designers are also testing special camera
sensors to allow visual vessel classification, since collision prevention
maneuvering rules vary with vessel type (Courtland, 2016).
Although the main sensory payload equipment is classified, it
is known, that the Sea Hunter will use a specially designed sonar equipment to
track ultra- silent diesel electric submarines (Littlefield,
n.d.). It has onboard information processing
architecture, which allows the vessel to interpret the collected data without
human help. The USV would track enemy submarine, defeat the efforts of the sub
to “delouse” itself, and periodically report the sub’s position, speed and
course (Savitz et al.,
2013).
It is unclear how the USV would defend itself in case of
possible air strikes, deliberate ramming by another vessel, jamming, electronic
warfare or other attack (Savitz et al., 2013). Mission trials showed that the USV can effectively detect
submarine targets at distances up to two miles. The Sea Hunter prototype is
scheduled to undergo sea trials and experimentations and planned to be deliver
to the Navy by the end of 2018.
The
Sea Hunter is an excellent example of progress in the UMS technology. With
highly expendable payload capabilities, it can offer tremendous benefits for a wide
range of missions and configurations for future unmanned naval vessels, which
go beyond ASW applications.
Figure 2. The Sea Hunter on the ASW mission. Adapted from “Anti-Submarine Warfare (ASW) Continuous Trail Unmanned Vessel (ACTUV),” by S. Littlefield, n.d. Copyright by DARPA.
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