What photon torpedoes SHOULD have been...
Posted: 2006-12-21 12:56am
In two threads on the Pure Star Trek and Star Trek v. Star Wars boards, the nature of photon torpedoes has cropped up in discussion. We know, of course, that the photon torpedo is essentially a missile with a matter/antimatter warhead. So named because, in the 60s, it was thought that the product of a M/AM blast would be pure gamma ray photons. That's not quite the case, of course, but the colliqualism persists not only for photorps but the more exotic forms of nuclear photonic rocket designs which are based on matter/antimatter anihilation as the propulsion source.
The friendly folks at Atomic Rocket have demonstrated why you'd never get 100% yield from an M/AM intermix in a warhead design. Lots of people go with the STNG/STDS9 tech manual assumption (though not supported in any actual episode) that a photorp warhead would produce the equivalent blast of a 64 MT nuclear warhead, a bit more than the yield measured for Tsar Bomba, the largest test detonation in history. According to the Atomic Rocket folks, if you could fuse one gram of matter and one gram of antimatter under conditions of 100% efficiency, you'd ideally get an energy yield equivalent to a 43 KT atomic bomb. Not bad if you can make it work.
Unfortunately, various factors ensure that you'd be lucky to get about 70% of that at most, which would still give you a respectable 30KT blast. The more pessimistic estimates downgrade the figure to a mere tenth of that yield for a 3KT blast, roughly the equivalent of a World War II blockbuster bomb. You're still getting much more bang for the buck, since you're using only a tiny fraction of the explosive material you'd need for a blockbuster bomb or a standard atomic bomb.
The problem of course is that you have to keep that 1kg of antimatter safely bottled up longterm until you're ready to fire your torpedo. Which leads to problems of its own. With a starship's full-load arsenal, you're talking about keeping 250kg of antimatter stored up outside the ship's standard fuel bunkers for a long period of time. Of course, it's been suggested that the antimatter is drained from the ship's own reserves and loaded into the warheads prior to combat. Which means a complex piping system to feed the antimatter into the warheads —which can break down or suffer battle damage, which neutralises the rest of your photorp arsenal. Which in a battle situation would be bad.
However, suppose for a moment that, instead of using the antimatter as reactant for the warhead it was instead used for propulsion and your torpedo, instead of an active weapon system, is actually nothing more than a 100kg trashcan-sized slug with a small-scale M/AM photonic rocket at the one end? The torpedo would be ejected out of a starship's tube, after which the engine would fire up, accelerating the 100kg mass very rapidly (say, a one second burst) to a velocity of 3000 km/sec. In this conception the torpedo is nothing more than a hypervelocity kinetic-kill missile.
A 100kg object impacting a solid target (or presumably a deflector shield) at 3000 km/sec would produce a force equivalent to a 107kt nuclear blast, which is about equivalent to the W-76 warhead carried by a Trident II SLBM. The antimatter to fuel the missiles could be contained in the rocket's own storage bottle, which would be plugged into the ship's general power grid for maintenance until it's time to load the tubes for the first salvo. A short-life battery would maintain the containment for only a matter of a minute or two, but you want that anyway when the torpedo is clear of the ship.
A fuel load of 400-600 micrograms of M/AM would be sufficient for this type of torpedo, constituting a far more logical usage for antimatter than in a warhead. Of course, this would mean the writers could never realistically use the photon torpedo as a mine or a "space depth charge". Instead, they could have shown a starship carrying a rather large arsenal (apart from its phasers) with the equivalent destructive power of about twenty present-day Trident SSBNs by employing a fairly basic brute-force principle instead of technobabble.
The friendly folks at Atomic Rocket have demonstrated why you'd never get 100% yield from an M/AM intermix in a warhead design. Lots of people go with the STNG/STDS9 tech manual assumption (though not supported in any actual episode) that a photorp warhead would produce the equivalent blast of a 64 MT nuclear warhead, a bit more than the yield measured for Tsar Bomba, the largest test detonation in history. According to the Atomic Rocket folks, if you could fuse one gram of matter and one gram of antimatter under conditions of 100% efficiency, you'd ideally get an energy yield equivalent to a 43 KT atomic bomb. Not bad if you can make it work.
Unfortunately, various factors ensure that you'd be lucky to get about 70% of that at most, which would still give you a respectable 30KT blast. The more pessimistic estimates downgrade the figure to a mere tenth of that yield for a 3KT blast, roughly the equivalent of a World War II blockbuster bomb. You're still getting much more bang for the buck, since you're using only a tiny fraction of the explosive material you'd need for a blockbuster bomb or a standard atomic bomb.
The problem of course is that you have to keep that 1kg of antimatter safely bottled up longterm until you're ready to fire your torpedo. Which leads to problems of its own. With a starship's full-load arsenal, you're talking about keeping 250kg of antimatter stored up outside the ship's standard fuel bunkers for a long period of time. Of course, it's been suggested that the antimatter is drained from the ship's own reserves and loaded into the warheads prior to combat. Which means a complex piping system to feed the antimatter into the warheads —which can break down or suffer battle damage, which neutralises the rest of your photorp arsenal. Which in a battle situation would be bad.
However, suppose for a moment that, instead of using the antimatter as reactant for the warhead it was instead used for propulsion and your torpedo, instead of an active weapon system, is actually nothing more than a 100kg trashcan-sized slug with a small-scale M/AM photonic rocket at the one end? The torpedo would be ejected out of a starship's tube, after which the engine would fire up, accelerating the 100kg mass very rapidly (say, a one second burst) to a velocity of 3000 km/sec. In this conception the torpedo is nothing more than a hypervelocity kinetic-kill missile.
A 100kg object impacting a solid target (or presumably a deflector shield) at 3000 km/sec would produce a force equivalent to a 107kt nuclear blast, which is about equivalent to the W-76 warhead carried by a Trident II SLBM. The antimatter to fuel the missiles could be contained in the rocket's own storage bottle, which would be plugged into the ship's general power grid for maintenance until it's time to load the tubes for the first salvo. A short-life battery would maintain the containment for only a matter of a minute or two, but you want that anyway when the torpedo is clear of the ship.
A fuel load of 400-600 micrograms of M/AM would be sufficient for this type of torpedo, constituting a far more logical usage for antimatter than in a warhead. Of course, this would mean the writers could never realistically use the photon torpedo as a mine or a "space depth charge". Instead, they could have shown a starship carrying a rather large arsenal (apart from its phasers) with the equivalent destructive power of about twenty present-day Trident SSBNs by employing a fairly basic brute-force principle instead of technobabble.
