IRIS Dena ship sinking: What is the Mark 48 torpedo used by the US Navy to sink the Iranian Navy ship?

The United States on Wednesday released black and white infrared footage showing the final moments of Iran’s IRIS Dena before it sank in the Indian Ocean. The video captures an American submarine launching a Mark-48 heavyweight torpedo that struck and destroyed the modern Iranian Moudge class frigate. The ship was targeted approximately 40 km off the southern coast of Sri Lanka, near Galle.

According to US officials, the strike killed more than 80 sailors and sent the warship to the bottom of the ocean. The incident marks one of the most dramatic naval developments in the widening Middle East crisis, as rockets, missiles and drones continue to fly across Israel, Iran and other parts of the region, raising fears of a broader regional war.

US Defense Secretary Pete Hegseth described the strike as a “quiet death” and said it was the first sinking of an enemy ship by a US torpedo since World War II.

What is the Mark 48 torpedo?

The Mark 48 is a heavyweight, wire-guided torpedo introduced in 1972 and continuously upgraded since then. Modern versions, such as the Mk-48 ADCAP (Advanced Capability), feature improved propulsion, guidance systems, and digital electronics.

It weighs about 3,800 pounds (around 1,700 kilograms) and carries a powerful high-explosive warhead.

How does it operate?

• Guidance system: It uses both active and passive sonar to detect, classify and track underwater targets.
  
  
• Wire-guided control: After launch, submarine operators can guide the torpedo in real time through a wire connection, updating target data and adjusting its course.
  
  
• Autonomous mode: If the guidance wire is cut or lost, the torpedo switches to fully autonomous homing and continues tracking the target independently.
  
  
• Advanced processing: It uses digital signal processing and decision-making algorithms to track targets even in complex underwater environments.
  
  

Why is it lethal?

Unlike weapons that hit a ship directly, the Mark 48 is designed to detonate beneath the vessel. The underwater explosion creates a large gas bubble that expands and collapses, breaking the ship’s keel, the central structural beam, which can cause the vessel to split and sink rapidly.

The torpedo can travel at speeds exceeding 55 knots (over 100 km/h) and strike targets dozens of kilometres away, making it one of the most powerful undersea weapons in modern naval warfare.