UGM-84L Sub-Harpoon
Boeing Defense · Submarine-Launched Anti-Ship Missile / Anti-Ship Strike from Submarines · USA · Cold War (1970–1991)
The UGM-84 Sub-Harpoon is the American submarine-launched encapsulated version of the Harpoon anti-ship missile — Boeing's principal submarine-launched anti-ship weapon for the US Navy and allied forces across four decades. Boeing derived the UGM-84 from the air-launched AGM-84 Harpoon between 1977 and 1981, with service entry in 1981. Roughly 2,000 UGM-84s have been built across all variants. Operators include US Navy submarines, the Royal Navy, JMSDF, German Navy, Israeli Navy, Italian Navy, Spanish Navy and Greek Navy submarine forces.
Airframe, warhead and guidance are identical to the AGM-84D Harpoon; the UGM-84 differs only by an external buoyant launch capsule and a slightly modified rocket booster. To fire, the encapsulated round is loaded into a 21-inch torpedo tube and ejected like a torpedo. The capsule rises buoyantly to the surface, then a small rocket booster and sustainer kick the Harpoon clear of the water and into level flight. From there the missile flies the standard Harpoon profile: sea-skimming cruise to a radar terminal homing attack. Maximum range is 130 km. The warhead is a 221 kg semi-armour-piercing charge. Because the launch happens from underwater, the firing submarine stays hidden — the surface plume and low missile track are visible briefly, but unlike a surface ship's launch they do not pinpoint the boat.
Combat use has been thin; most submarine fleets have never fired a Sub-Harpoon in anger. The one exception came in 1982, when the Argentine submarine ARA San Luis attempted Sub-Harpoon launches against British surface forces during the Falklands War — every attempt failed due to wiring and fire-control faults. For most of its service life the UGM-84 has been the only Western submarine-launched anti-ship missile. Newer weapons — the Naval Strike Missile and a future submarine-launched LRASM — are gradually replacing it in US Navy service. As of 2026, six allied navies still field the UGM-84 from their submarines.
For Kids — a shorter, friendlier version
The UGM-84 Sub-Harpoon is a missile that launches from a submarine under the sea. It was made by Boeing and entered service in 1981. The American Navy and six other navies around the world use it.
Launching this missile is pretty cool. A submarine fires it from a torpedo tube just like a torpedo. The missile sits inside a special floating capsule. The capsule rises up through the water to the surface.
Once the capsule reaches the surface, a small rocket fires the missile out of the water and into the air. Then the missile flies very low over the ocean toward its target. It uses radar to find and hit enemy ships. Its range is about 130 kilometers — longer than many large cities are wide.
The Sub-Harpoon is almost the same as the regular Harpoon missile. The big difference is the floating capsule that protects it underwater. The capsule lets the submarine stay hidden during the whole launch. About 2,000 of these missiles have been built over the years.
Fun Facts
- The Sub-Harpoon has been used by the American Navy for over 40 years.
- It launches from a torpedo tube, just like a regular torpedo!
- A floating capsule carries the missile safely to the water's surface before it flies.
- The missile flies so low over the ocean that it almost skims the waves.
- Its explosive charge weighs 221 kg — heavier than a large motorcycle.
- Six other navies besides the American Navy use the Sub-Harpoon, including the British and Italian navies.
- About 2,000 Sub-Harpoons have been built across all versions.
- The submarine stays hidden the whole time because the launch happens underwater.
Kids’ Questions
How does the Sub-Harpoon get out of the water?
The missile is sealed inside a special floating capsule. The submarine fires the capsule from a torpedo tube. The capsule floats up to the surface on its own. Then a small rocket pushes the missile up and out of the water into the air.
How far can the Sub-Harpoon fly?
The Sub-Harpoon can fly up to 130 kilometers. That is longer than many large cities are wide. It flies very low over the water the whole way.
Why does the submarine stay hidden when it fires?
The missile launches underwater inside a capsule. The submarine never has to come to the surface. This makes it very hard for an enemy to spot the submarine during a launch.
Variants
- UGM-84A / B / C (1981)
- Original versions, equivalent to AGM-84A/B/C.
- UGM-84L (1990s)
- Block II version with GPS-aided guidance.
Notable Operators
- US Navy submarine force (1981-present)
- Principal operator; carried on Virginia and Los Angeles class submarines.
- 6 allied navies
- Royal Navy, JMSDF, Germany, Israel, Italy, Spain, Greece, Egypt.
Frequently Asked Questions
How does the encapsulated launch work?
The UGM-84 is stored and fired inside a sealed plastic canister sized for a standard 21-inch torpedo tube. Compressed air — the same impulse charge that launches torpedoes — ejects the capsule from the tube, and its positive buoyancy carries it to the surface. At the surface, small explosive bolts blow the nose off the capsule and the missile's solid-fuel rocket booster ignites, kicking the Harpoon upward and clear of the water. The booster burns for about 2 seconds, lifting the missile to roughly 100 m altitude and cruise speed, after which the Williams J402 turbojet takes over for cruise and attack. The full sequence from torpedo-tube fire to level cruise runs about 10-15 seconds. Only the surface plume briefly betrays the firing boat, which is why the Sub-Harpoon remains an attractive standoff anti-ship option for submariners.
Sources
See Also
- AGM-84 Harpoon — Air-launched parent variant