Home' Asia Pacific Defence Reporter : APDR May 2015 Contents SEA 1000
countermeasures? What is the aircraft within effective
kill range of the submarine? What are the escape
options post weapon launch (noting the missile will
likely leave a booster trail that leads back to the
submarine’s exact firing position). And many more ...
Noting the greater variety and definitiveness of
sensor information at periscope depth (PD), and the
inherent lack of quality data when deep (except in
the situation where the helicopter is in the dip), the
preferred firing depth will be PD.
The target will almost always be line of sight.
A fire control solution will need to be generated.
This has to be established using normal techniques,
cognisant of the need to avoid mast exposure. With
respect to a quality solution, an aircraft altering course
on a regular basis could prove problematic.
As to the required accuracy of the solution, this will
be dependent on the missile attributes and the tactical
scenario. All of the sub-surface to air solutions being
proposed (and described below) have an infrared
seeker for use in guidance; pulse-Doppler radar
variants may have difficult with a (stationary) helicopter
in the dip. These infrared seeker heads typically have
a 5 to 10 degree field of view, but with the IR sensor
mounted on a gimbal that allows the missile to sweep
across an arc in front of the weapon. This capability will
allow a weapon to succeed with rough targeting data
only, although a close aircraft contact with high bearing
or elevation rates may, in the end, prove problematic.
A helicopter in the dip will prove less challenging; a
“sitting duck” in many respects.
The missile/s will be fired at the target/s and the
submarine may remain at PD to assess the missile
success, ready to fire second shots immediately as
required. The potential danger in this approach for the
submarine can be offset by 1) firing the weapon such
that the aircraft is un-alerted for as long as possible (an
aircraft moving away will often also provide the missile
seeker head with the best IR picture to work with) or
2) the aircraft pilot and TACCO being totally distracted
from ASW by ‘threat-to-life’. If the weapon has feedback
telemetry to the submarine combat system this may
enable the submarine to leave PD earlier.
In the event of a miss, standard aircraft evasion
techniques will have to be adopted. If the aircraft has
managed to manoeuvre close to “on top” a special
fire-mode for the missile will likely be required; one that
lets the missile carry out its boost phase of flight, then
heads away from the launch position and finally alters
back to the launch point. The distance it travels away
from the launch point will be governed by the field of
view of the IR sensor. A weapon detonating on top of
the submarine's position is unlikely to cause damage.
The submariner would expect that the missile
employed for submarine anti-aircraft use would have
a relatively good probability-of-hit and subsequent kill.
MISSILE LAUNCHER REQUIREMENTS
Before looking at each of the missiles, it is worth
discussing the options; mast, vertical launch and tube
One option being adopted by the French company
DCNS is to use a hoist-able mast configured to carry
three missiles. When the target solution has been
generated the mast is raised and trained at the target.
Firing a second missile is achieved by training the
launcher at the next target (or leaving it trained on the
first target if that is what is required). This option allows
a small arsenal of anti-aircraft weapons to be carried
without disturbing the main torpedo compartment
weapon load. However, it negates the ability for the
weapon to be fired when deep.
The other method is to launch the missile from a
vertical launch tube, similar to the Tomahawk missile
arrangement on US submarines. This is the option
being pursued for the US Navy. A vertical launcher
takes up dedicated space (as opposed to tube space
that can be configured to take a number of different
types of weapons, depending on the intended mission)
but allows the missile to be fired at short notice whilst
deep. One consideration in this selection for the US
Navy is likely to be the limited number of tubes that are
found on both LA and Virginia class submarines; those
four tubes are likely to be loaded with other weapons
types in ‘hot’ situations.
The final option, being pursued by both DCNS and
TKMS is to launch the missiles from the tube. The
exact approach used by these two companies in very
US MISSILE OPTIONS:
The AIM-9X being developed by NAVSEA/Raytheon
is based on the well-proven Sidewinder missile.
Information on the submarine variant is scant.
The missile is launched in encapsulated form, similar
to the approach used for the Tomahawk missile. It will
almost certainly be launched fire-and-forget with the
weapon relying on its own seeker. It will have a speed
of Mach 2.7 and a range of circa 35 km.
The status of development of this weapon is
unknown. In 2006 Raytheon announced that it had
successfully launched an AIM-9X from a stationary
vertical platform in a test of its potential launch from
a submarine. “The firing demonstrated the potential
for underwater vertical launch from a capsule and
the missile's ability to quickly reach stable flight when
starting from a stationary platform”. The press release
suggested this weapon was not just to be a defensive
weapon but one that would allow a submarine “to
strike targets with surprise from shallower coastal
FRENCH MISSILE OPTIONS:
A3SM MISTRAL 2
The MISTRAL A3SM (Arme Anti-Aérienne pour Sous
Marins ... literally Anti-Air Weapon for Submarines)
variant is being developed from the proven surface ship
MISTRAL 2 missile.
This weapon will be launched from the hoist-able mast
described earlier. The missiles cannot be reloaded at
sea. A new canister of three weapons can be replaced
when the vessel returns alongside, with the empty
canister being returned to the missile manufacturer’s
(MBDA) local support facility for reloading.
An MH-60R Sea Hawk from the Raptors of Helicopter Maritime Strike Squadron (HSM) 71 assigned to the aircraft carrier
USS John C. Stennis (CVN 74) tests a dipping sonar. Credit: U.S. Navy photo by Mass Communication Specialist 2nd Class
14 Asia Pacific Defence Reporter MAY 2015
23/04/2015 2:07 pm
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