Modern conventional submarines frequently operate in shallow waters and coastal areas, where they are especially vulnerable to airborne ASW threats. Restricted by this shallow water and narrow areas of operation typical evasion manoeuvres like diving, using differ-ent salt or temperature layers and escaping into deeper water are often not an option. ASW helicopters equipped with dipping sonar and lightweight torpedoes are pose a sub-stantial threat under these circumstances.
The Diehl Defence and thyssenkrupp Marine Systems developing IDAS together, which enables the submerged submarine to actively engage airborne threats without exposing own sensors.
Right after the submarine crew identifies a potential threat condition, IDAS will be ready for operation. Range and bearing are determined/estimated by the submarine's sensor and sensor-data management system. As soon as the commanding officer authorizes, the operator will launch the effector. For the engagement it is not necessary that the subma-rine risks further detection by showing mast mounted optical or ESM sensors or even by surfacing.
Figure 1: IDAS operational concept
During the underwater trajectory, the missile manoeuvres into the direction of the target, thereafter breaks the surface, accelerates to cruising speed and flies towards the ex-pected target area. The operator onboard the submarine maintains control over the mis-sile ("human in the loop"), while the submarine remains hidden. This enables the operator to change the target designation or to abort the mission. In the unlikely event of a loss of the connection (i.e. by rupture of the optical fibre), the missile continues to operate ac-cording to the operational settings, i.e. engaging the last selected or the most probable target, if this is in accordance with the rules of engagement, or mission abort.
In addition, the "human in the loop" enables the system to fulfil secondary roles, i.e. the engagement of surface targets, where a heavy weight torpedo is not appropriate. It also provides the submarine's commander with means for escalation appropriate to the cur-rent operational situation. Further on, the integration of a GPS or other satellite navigation system sensor would include even land targets (e.g. to support SOF operations) into the target.
System description - technical concept
As basis for the industry funded IDP, which started 2012, the IDAS consortium defined a set of requirements.
These were established in cooperation with submariners of the parent German and other navies. Some of the top-level requirements are:
• system range >15 km
• launching depth below periscope depth (comparable to e.g. the Sub-Harpoon missile system)
• minimized restrictions to submarine's manoeuvrability during missile employment
• operator control over the effector during complete employment
• use of existing weapon tubes and weapon loading and storage infrastructure
• minimum integration effort (stand-alone integration)
• full integration with the submarines combat system as growth potential.
The system consists of the following main components, which are described in the follow-ing subchapters.
The IDAS missile
The IDAS missile is a solid fuel rocket propelled autonomous missile equipped with an IIR seeker, which is based on the technology of existing advanced programmes. During its complete mission time it is linked to the submarine's combat system via an optical fibre.
The rocket motor is ignited after the missile has left the weapon tube and reached safety distance to the submarine. The missile turns into target bearing and flies to-wards the surface. Having detected the target by means of the IIR seeker, it homes onto the target and destroys it.
Every IDAS missile is equipped with an optical fibre that is located in a bobbin sys-tem at the missiles aft and connects the effector with the operator. This fibre-optic link allows continuous transmission of images from the missile's IIR seeker to the operator's screen and enables the operator to verify the target selected by the seeker and to command (correct if necessary) the missile right into the chosen hit point.
Wings and fins are folded alongside the missile when stored and are unfolded in safe distance to the submarine after ejection.
The IDAS system uses an ejection container, which stores and ejects them, using a fully integrated separate thrust piston system for every missile, severally out of a torpedo tube.
The ejection container features the main dimensions and weight of a typical heavy weight torpedo. This allows an easy integration for new submarine building projects as well as for refit solutions of existing submarines.
Figure 2: Embarking an IDAS launching container into the HDW 212A submarine U33
Figure 3: Embarking an IDAS ejection container into the Ula-class submarine "Uredd"
Beside the IDAS missiles the ejection container contains ejection control electronics and a missile interface system.
Missile control system - integration aspects
The missile control system is the human machine interface and can either be tightly (full) integrated into the (existing) submarine's weapon control system ("integrated version") or partly (flat) integrated by using a separate Missile System Control Panel and additional interface units.
While the fully integrated version is operationally more comfortable, it has the higher integration efforts and is recommended for new submarine projects or midlife up-grades.
For upgrading submarines, which are already in service or preparing to start with the technology, a flat integration is most likely the better solution, concerning the re-lation of efforts and performance. Anyhow, both configurations benefit of the same core capabilities and features.
An IDAS missile was already launched successfully from a German Navy Class 212A submarine.
Within this (third) firing several important submarine integration aspects were demon-strated. This firing was again closely followed by numerous interested NATO and non-NATO navies.
Ejection tests in May 2015 at the dockyard of thyssenkrupp Marine Systems confirmed the basic design decisions.
After several unwinding tests with the optical fibre bobbin under different operational con-ditions including an ignited rocket motor, further tests with submarines of the Royal Nor-wegian Navy were prepared.
In 2016 loading and unloading tests of the system and later on ejection tests from HNoMS "Uredd" were accomplished successfully. The consortium concluded the IDP with engi-neering development tests in May 2017 in cooperation with the Royal Norwegian Navy.
Figure 11-5: IDAS firing from the HDW Class 212A submarine U33
In 2019 the German procurement agency BAAINBw released a Request for Proposal to the IDAS consortium with respect to the final development and qualification of the IDAS system and its integration into the HDW Class 212A submarines of the German Navy.