TNT EQUIVALENT

(Redirected from Megaton)
'TNT equivalent' is a method of quantifying the energy released in explosions. The 'tonne of TNT' is used as a unit of energy, approximately equivalent to the energy released in the detonation of this amount of TNT.
The kiloton and megaton of TNT have traditionally been used to rate the energy output, and hence destructive power, of nuclear weapons (see nuclear weapon yield). This unit is written into various nuclear weapon control treaties, and gives a sense of destructiveness as compared with ordinary explosives, like TNT. More recently, it has been used to describe the energy released in other highly destructive events, such as asteroid impacts.

Contents

Value

Examples

See also

References

Value

A gram of TNT releases 980–1100 calories upon explosion. To define the 'tonne of TNT', this was arbitrarily standardized to 1000 thermochemical calories = 1 gram TNT = 4184 J (exactly).^[1]
This definition is a conventional one. Explosives energy is normally calculated using the thermodynamic work energy of detonation, which for TNT has been accurately measured at 1120 cal/g from large numbers of air blast experiments and theoretically calculated to be 1160 cal/g.^[2]
The measured pure heat output of a gram of TNT is only 651 thermochemical calories ≈ 2724 J,^[3] but this is not the important value for explosive blast effects calculations.

Grams TNT	Symbol	Tons TNT	Symbol	Energy
gram of TNT	g	microton of TNT	μT	4.184 J
kilogram of TNT	kg	milliton of TNT	mT	4.184 J
megagram of TNT	Mg	ton of TNT	t	4.184 J
gigagram of TNT	Gg	kiloton of TNT	kt	4.184 J
teragram of TNT	Tg	megaton of TNT	Mt	4.184 J
petagram of TNT	Pg	gigaton of TNT	Gt	4.184 J

Examples

The atomic bomb dropped on Hiroshima on August 6, 1945 exploded with an energy of about 15 kilotons of TNT (~6.3 joules). The nuclear weapons currently in the arsenal of the United States range in yield from .3 kt to 1.2 Mt TNT equivalent. During the Cold War, the United States developed hydrogen bombs with a maximum theoretical yield of 25 Mt; the Soviet Union developed a prototype weapon, nick-named the Tsar Bomba, which was tested at 50 Mt, but had a maximum theoretical yield of 100 Mt.^[4] The actual destruction of such weapons can vary greatly depending on conditions, such as the altitude at which they are detonated, the nature of the target they are detonated against, and the physical features of the landscape where they are detonated.
On a much grander scale, supernova explosions give off about 10⁴⁴ Joules of energy, which is about ten octillion (10²⁸) megatons of TNT.
By E=mc², when 1 kilogram of antimatter annihilates with 1 kilogram of matter the reaction produces 1.8 J, which is equal to 42.96 Mt.In antiproton annihilation, about 50% of this energy is carried off by effectively invisible neutrinos (see S.K. Borowski, Comparison of Fusion/Antiproton Propulsion systems); in contrast, almost 100% of
electron-positron annihilation events emit their energy entirely as
gamma rays.

See also

★ Ton

★ Tonne

References

1. NIST Guide for the Use of the International System of Units (SI): Appendix B8 - Factors for Units Listed Alphabetically
2. Cooper, Paul. ''Explosives Engineering'', New York: Wiley-VCH, 1996, pp 406.
3. "Physics for Future Presidents, a textbook", 2001-2002, Richard A. Muller, Chapter 1. Energy, Power, and Explosions
4. See Currently deployed US nuclear weapon yields, Complete List of All U.S. Nuclear Weapons, Tsar Bomba, all from Carey Sublette's Nuclear Weapon Archive.


★ Guide for the Use of the International System of Units (SI)

★ Nuclear Weapons FAQ Part 1.3

★ Rhodes, Richard. ''The Making of the Atomic Bomb'', New York: Simon and Schuster, 1986.