Ramjet ammo

A ramjet, sometimes known as a stovepipe jet requires virtually no moving parts. Indeed, if it uses solid fuel, the heat of the air flowing into it ablates the fuel, and no moving parts are necessary. The main problem with ramjets is getting them up to the speed where they function.

In theory, it might be possible to minaturize such a ramjet down to the size of a M-60 grenade, shotgun shell, or perhaps even a .45 round. In practive military artillery would likely be the first weaponry it would work with.

Such a small engine could then be fired out of the gun to get up the initial speed needed for the ramjet to begin operation. To avoid jamming the exhausts, a sabot would likely be needed, and this might function as a parachute later on to pull an ignition on the engines. The ramjet would then greatly increase the velocity of the projectile. If the outlets were slightly canted, this might also continue to impart spin on the projectile, which may provide gyroscopic stability during flight.

Such projectiles could be fired from existing weapons, and might increase range, velocity, or both.

I forsee applications in a number of fields: Signal flares are an obvious choice, as individual rounds are already expensive, accuracy and secrecy is of little importance, but distance is considered highly desirable.

More exacting design standards could allow these weapons to be useful in armor piercing rounds, and in larger ammunition, they might be capable of penetrating tanks with an explosive round, thus replacing heavy and expensive bazookas with somewhat smaller and cheaper guns that could be easily used for at least a few other applications as well.

CWIS weapons systems, currently used to defend ships against missiles might also benefit greatly from longer range bullets, although I am not sure whether the reduction in weight of the ammo would be worth the range increase. Usually when the aim is to defend against missiles, cost is not much of an issue.

Lastly, if they could be produced cheaply enough, these might make for far more deadly antipersonnel weapons. The jet ports would heat the projectile, and hollow it out, making deformation and fragmentation of the projectile upon impact more likely. Since the jet ports would provide stability in flight, but clog upon impact this feature would also tend to favor causing the projectile to tumble around once inside the body. Elite forces might find this to be quite useful on high-risk missions.

Ramjet ammo would likely be quite expensive, and therefore of limited usefulness in many fields. However, unlike gyrojet ammunition, these could be used in existing guns, making their adoption or rejection much cheaper on any group who should choose to experiment with them.