SEMA —
a submarine on demand.
SEMA is an autonomous, recoverable acoustic training target that puts a credible submarine signature in the water on the navy's own schedule. Easy to launch and recover from a RHIB or a ship, it lets crews train the full detect-classify-track-engage cycle and run torpedo-firing exercises — without taking a real submarine off the line. In service with the French Navy and selected by the Royal Netherlands and Belgian navies.
ASW skill is perishable — and real submarines are scarce.
Detecting and prosecuting a submarine is one of the hardest tasks a navy trains for, and the skill fades fast without repetition. But real submarines are few, costly to run and almost never free to play the target. SEMA breaks that bottleneck: an autonomous target that recreates a realistic submarine acoustic signature and submarine-like kinematics, deployed from the navy's own small craft — so crews can rehearse the full detect-classify-track-engage cycle, and torpedo programmes can fire against a controllable point, as often as the training plan demands.
It behaves like the real thing on sonar
SEMA is built around a genuine submarine signature, not a simple pinger that teaches the wrong habits. An acoustic echo-repeater works across 1–33 kHz with five bands for active sonar, two bands tuned to homing-torpedo seekers, and multi-echo artificial intelligence — so the contact your operators work responds the way a submarine would on their sensors.
Passive, active and combined acoustic modes, six narrowbands (200 Hz–38 kHz) and two broadbands let the same target span everything from quiet-passive search training to active-sonar prosecution and torpedo engagement. An on-board recorder encrypts the run for after-action analysis.
A moving threat that fights back — then comes home
Plan the run as waypoints (latitude, longitude, speed, depth) or configurable segments (heading, speed, depth, timeout). SEMA can be set to perform evasive manoeuvres, presenting a target that does not simply hold a straight line for the prosecuting crew.
It starts automatically at a programmed depth, can be stopped by acoustic command at any time, and surfaces to a defined GPS recovery point with an antenna mast (GPS, X-Band, flash light) for fast pickup. An auto-recovery mode brings the target back even on a system failure — so an expensive asset is not lost during the exercise.
No mine-hunter, no crane, no waiting
At 2.13 m, 150 mm in diameter and 33 kg in air, SEMA is sized for two operators and launches from a RHIB or any boat — and recovers to any boat. The system ships complete with a launching ramp, pike poles and a fully rugged control laptop.
Between runs it is reconfigurable in one hour: swap the rechargeable battery, download the encrypted mission data, reprogram the next run, and relaunch. Buoyancy adapts for sea or fresh water, and encryption & deciphering keys keep the training data secure.
SEMA training target specifications
Manufacturer figures (RTsys SEMA briefsheet). Exact configuration confirmed at quotation against your training objectives. SEMA is subject to export-control restrictions.
- TypeAutonomous, recoverable acoustic target
- TrainsASW aircraft · helicopters · frigates · submarines
- RoleASW · torpedo · operator training
- Length2,130 mm
- Shell diameter150 mm
- Height285 mm
- Weight (in air)33 kg
- Operating depthDown to 300 m
- Speed4 to 15 knots
- Endurance10 h @ 4 kn · 1.5 h @ 15 kn
- NavigationINS · GPS · DVL · pressure sensor
- Mission planningWaypoints or configurable segments
- Acoustic modesPassive · active · combined
- Echo-repeater1–33 kHz · multi-echo AI
- Active sonar bands5 bands
- Torpedo-homing bands2 bands
- Narrowband / broadband6 NB (200 Hz–38 kHz) · 2 BB (450 Hz–8 kHz · 10–23 kHz)
- RecorderOn-board, data encrypted
- RecoveryGPS point · antenna mast · auto-recovery on failure
- ControlRemote (radio / acoustic) · acoustic stop command
- TurnaroundReconfigurable in one hour
- Latest variantSEMA MK-II — compact, latest-gen sonar & homing compatibility
- OriginRTsys — Caudan (Brittany), France
- ExportITAR-free · EU / French export controls apply
SEMA in the water, with real navies
Footage published by RTsys — including the Royal Netherlands Navy operating SEMA and a live RHIB deployment.
Already trusted by NATO navies in your waters
SEMA is in service with allied navies — including two of Denmark's closest North Sea and Baltic partners.
SEMA MK-II in service
RTsys delivered the new-generation SEMA MK-II to the Marine Nationale in 2020. SEMA is in service with the French armed forces and was developed in close cooperation with the French Navy.
4 of 7 targets · 2021
In February 2021 the State of the Netherlands selected RTsys for a seven-target order — four for the Royal Netherlands Navy — to train real-condition submarine localisation and tracking.
3 of 7 targets · 2021
The remaining three targets of that same binational 2021 contract go to Belgium's Naval Component — a shared North Sea ASW training capability with the Netherlands.
Denmark operates in the same North Sea and Baltic ASW environment as the navies above. SepcoTech brings the identical, field-proven SEMA target — and full through-life support — to the Royal Danish Navy as your single point of contact in Denmark.
Train the crew without scheduling a submarine
Because the threat is generated by the target itself, training is no longer hostage to submarine availability. A navy can run the detect-track-engage cycle far more often — building and keeping the perishable skill that ASW depends on — and recover the same target to do it again tomorrow.
Check. Train. Analyze.
Anti-Submarine Warfare
The ASW overview — how SEMA and the SIERA measurement range fit the Check-Train-Analyze doctrine.
See the ASW overview →
Sonar & Signature Measurement
The SIERA range for validating sonar performance and characterising platform acoustic signatures.
Explore measurement →
Mine Counter-Measures
The other RTsys mission — a manned-and-unmanned MCM suite for EOD divers.
See the MCM suite →Part of a bigger mission
SepcoTech scopes and delivers this as one piece of a cross-supplier capability. See the missions it supports:
A safe pair of hands for defence at sea
Authorised Distributor
We represent RTsys directly — specification, supply and through-life support, coordinated from Denmark.
Naval & EOD Focus
A portfolio assembled for navies, coast guards and EOD units — not adapted from civilian kit.
One Point of Contact
Multi-supplier defence systems, integrated and quoted as a single package by one partner.
Backed Through Life
Training, spares and support for the full operational life of the system.
Speak directly with our defence specialist
Every enquiry is handled directly and in confidence — you will normally have a reply within one business day.
For spec sheets, capability documents, pricing or to arrange a briefing or demonstration — on this system or any platform in the SepcoTech defence portfolio — contact me directly:
- Spec sheets & technical datasheets on request
- Briefings & demonstrations for units & agencies
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