Explosive harpoon
The explosive harpoon is a type of harpoon which uses an explosive discharge to assist in whaling. In Norway, Japan, and Iceland, penta-erythritol tetra-nitrate is used in harpoon grenades. These are steel canisters that thread onto the tip of a reusable harpoon and explode by means of a hook and trigger line when they have penetrated approximately half a meter into the whale. Shrapnel and hooks that are attached to the harpoon cable are lodged into the whale's body, inhibiting the whale's ability to escape. A cable then reels the whale in as it draw its last breath. Norway uses more advanced and more expensive grenades.  They claim that 80% of whales are killed instantly. Iceland uses the Norwegian grenades, which can kill even large fin whales instantaneously 84% of the time.  In Japan, the use of harpoons has been shown to yield a poor rate of instantaneous fatalities.

Historic versions

Albert Moore's explosive harpoon 
Among many patents for explosive harpoons is Albert Moore's patented hand-dart explosive harpoon. It was invented on March 16, 1844 (U.S. Patent No. 3,490). This was the first handheld explosive harpoon ever invented. No other equipment was required, and a small boat equipped with these harpoons could take down a whale or other similar marine creatures.

Charles Burt’s explosive harpoon 
Patented on May 6, 1851, by Charles Burt of Belfast, Maine (U.S Patent No. 8,073), this was the second harpoon of its kind. The explosive was used as a propellant for the harpoon to enter the whale with great velocity.

Controversy

Possible use as a weapon 
An alternative version of the explosive harpoon, known as the power spear, was only designed for the purpose of spearing. That claim could lead to multiple interpretations of its true purpose. If it was only needed for fishing, then it could have been called a variant of the harpoon. However, because the official description in the patent was vague, its use is left up to interpretation.

Whale endangerment 
Whaling itself endangers multiple species of whales. Nearly all of the countries involved in whaling make use of explosive harpoons. The targeting of female Minke whales has caused marine conservation organizations to take a stand against the practice of whaling in general which, in turn, has helped bring a slow cease to the use of explosive harpoons. The excessive hunting of whales has been heavily assisted by the very fast-paced evolution of harpoons. The dramatic increase in reliability and effectiveness of harpoons has caused whaling to be a highly profitable source for trade.

Technologies

Evolution 
The major evolution of explosive harpoons has supported the evolution of hand thrown harpoons which are propelled by a gun or a ballistic type system. The biggest goal behind this improvement was to ensure there was more piercing capabilities to better deliver the harpoons. Harpoon guns were better optimized to ensure accurate deliverance of the harpoons themselves.

Mounted 
Term for broad range of explosive harpoons, though this variant is bigger and more powerful than a hand thrown explosive harpoon this specific variant is known to be mounted to vessels as well. The point of this explosive harpoon type is to launch the harpoon accurately and powerfully. A stationary variant in which the means of propelling the explosive harpoon is spring based. Explosive discharges were avoided due to the fact that the harpoon itself is volatile and delicate. At the time, using explosive discharges would cause much more damage than anything else.

Hand thrown 
The first iteration of explosive harpoon was designed as an improvement of the basic harpoon. Being that the explosive harpoon is the improvement on traditional harpoon, it stands to reason that it would be used as the original harpoon was intended though delivering better results.

Gunpowder explosives seemed to remain constant but the functionality of explosive seemed to change. The explosion itself for a long time was the main tool for the death of the whale. In later times the explosion can be used in tandem with barbs or other impaling devices that can deliver fatal blows to the whale.

Many different types of explosives and propellant were tried. Initially, black powder grenades were used in the tips of harpoons. They had numerous problems; if the powder were to get wet, it had the potential to misfire, the powder was very sensitive and had a tendency to combust prematurely, and the sulfur used in the powder could taint the taste of the whale’s meat.

Switched from gunpowder to explosive charges, most models involved uses of gunpowder and ways to optimize use of gunpowder.

Use 
The explosive harpoon was only documented for the use of whaling. Though that was the documented purpose, though due to Oliver Allen’s improvement of the harpoon gun it can be perceived that the harpoon gun could have other means of use besides whaling.

In 1986, the International Whaling Commission issued a global moratorium against commercial whaling. This had a positive effect on the worldwide whale population. However in certain countries like Canada, Japan, Norway, Indonesia and Iceland whaling is still continues on a limited scale, as this is considered an integral part of their cultures. The explosive harpoon is being replaced by rifles in most modern whaling in these countries.