ACER (aka 'Boom Bullets')

Personal weapons system that operates by firing small nuclear explosive shells

Image from Steve Bowers
ACER bullets being tested in the Lost Valley, Atlantis. Warning! 'Boom bullets' are not suitable for close combat


The term ACER was originally an acronym for Anti-Matter Catalyzed Explosive Round. Although criticized by purists because the antimatter was not a true catalyst (it was consumed during the reaction), the name stuck. The original acronym became a different sort of misnomer as the antimatter was replaced by a truly catalytic monopole arc, but by that time the terminology had become entrenched and the ACER name remains with us today.

Basic Design

ACER warheads, also known as "Boom Bullets" or "Boomers" are a family of often small caliber explosive warheads using microfission or microfission/fusion to produce a detonation far in excess of what could be delivered using conventional high explosives or overloaded carbon-based energy storage cells. Early designs used on the order of a nanogram of antimatter (equivalent to 2e5J, or 50 grams of TNT) to initiate fission. More modern ACERs use a high voltage monopole arc discharge as the "spark" to start the nuclear reaction. Upon launch, the warhead is armed, and upon reaching its target the boomer detonates. The fission blast may be enhanced by a fusion third stage. The end result is an x-ray hot fireball that emits a scorching flash of heat, an explosive blast wave, and a pulse of neutron radiation. A typical 1.85 cm diameter (12 gauge) warhead can vaporize a human and level a residential house, while simultaneously emitting enough neutrons to sterilize most cells and nanobots within tens of meters, and even sterilize radiation hardened cells and nanosystems within a few meters.

Although even a single boom bullet detonation can produce significant prompt radiation, they are typically engineered to minimize residual radioactivity. Radioactive contamination cannot be eliminated, but it requires repeated firings of modern boomers to pose a significant radiological hazard even in the absence of medical care.

Monopole catalyzed boom bullets contain both magtrons and anti-magtrons to generate the magnetic potential to drive the arc. After detonation, many of these annihilate each other, but a significant quantity of residual monopoles remain in the debris. Since static monopoles are passively safe as long as the matter they contact has not been completely ionized, this monopole contamination is not considered a hazard.

Delivery Systems

The most basic delivery system for an ACER round is a dumb-fire projectile. This design is launched by a coil gun, electrothermal gun, chemical propellant gun, or other variety of slugthrower. The warhead is usually primed by the shock of firing, and detonates by the shock of impact. While lacking any target seeking abilities, they can be quite accurate when fired from a rifled barrel by a trained user. In many cases, the high rate of fire can compensate for the lack of guidance.

More advanced ACER warheads are mounted in seeker rounds, that can lock onto a target before launch and guide themselves to fly directly into their victim. A typical seeker boom bullet contains an electrothermal arc-rocket powered by a disintegrating superconducting quench-solenoid for secondary propulsion after launch, and guided by airfoils or vectored thrust. Some seekers are given a relatively soft launch, and boosted to speeds of 2 km/s by the rocket. Others gain most of their initial speed from the gun they are fired from, and use a rocket or aerodynamic control surfaces only for course corrections.

Boomers can also be employed in semi-autonomous or autonomous suicide drones, such as synsects. This divorces the warhead from the launch platform, and while it adds versatility, drone boomers are typically much lower velocity and therefore easier to defend against than higher velocity bullets. Hybrid drone/seeker boomers use a synsect to autonomosly detect a target, then launch the boom bullet at high velocities with its arcjet rocket.

Notable Calibers

0.6 cm - This is the smallest practical caliber of boom bullet yet manufactured. It is too small for fusion boosting, nearly all of its explosive power comes from the conversion initiated fission. While fairly popular, guidance and maneuvering capabilities of seeker rounds are limited. A 0.6 cm boomer can dismember a neb into a splatter or sizzling gore, but has limited effect against rad hardened swarmtech or utility fog.

1.85 cm - The "12 gauge" caliber boom bullet is a popular warhead for the versatile and popular 12 gauge shotgun. A direct hit by a boomer of this size is guaranteed to completely destroy any target the size of a baseline human, although the collateral damage is likely to be extensive. The 12 gauge is a smooth-bore design that cannot withstand large chamber pressures. Consequently, dumb-fire boom bullets have a relatively low velocity (on the order of 0.4 km/s)that makes them somewhat vulnerable to point defense beams.

2.5 cm - Autocannon of 2.5 cm bore size are common light anti-armor weapons. When firing boomer rounds, they can smash even heavy mechanized armor and rapidly chew through fortifications. Anti-armor boom bullets typically use a directed blast to funnel much of their energy into a narrow forward cone. When detonating in contact with an armored surface, the resulting pressure in the hypersonic plasma jet is sufficient to overcome the material strength of even the strongest armor to a depth of at least half a meter.

4 cm - The first ACER warhead produced was for a 40 mm man-portable grenade launcher. These primitive boomers had a yield comparable to modern 12 gauge ACERs, lacked guidance, and were either dumb-fire or assisted by an unguided chemfuel solid rocket. While the antimatter containment was relatively secure, it was impossible to completely failsafe, and if damaged the antimatter could annihilate - although this would not detonate the fission fuel of a warhead that had not been armed. The caliber has remained in continuous use, and has improved to a powerful anti-armor warhead for the versatile 4 cm launch guns.

Launch guns are low pressure smoothbores with an even slower muzzle velocity than shotguns, making un-boosted 4 cm rounds easy targets for point defense.


First introduced in the late 22nd century CE but conceived well before, the Anti-matter Catalyzed Explosive Round was initially developed as a result of several advances, including the application of room temperature superconductors to particle accelerator design, the availability of cheap and abundant fusion and solar power, and the construction of the first dedicated antimatter production facilities in high orbit. These early facilities still lacked the capacity to economically produce quantities of amat sufficient for practical interplanetary travel and would not be able to compete with the much simpler technology of anti-matter mining of planetary magnetospheres for decades to come. However, the sudden increase in the availability of anti-matter led to a number of technological advances, particularly among governments and megacorporations that were willing and able to pay the premium prices.

ACER technology was invented at the Livermore facility in the then young nation of California in 2182 CE. Cutting-edge technology was a big part of Californian history and culture, and the Parliament in Sacramento was convinced that technological dominance was a matter of both national pride and security. The anti-matter containment technology developed at Livermore was revolutionary for its time, although limited to tiny quantities of amat before becoming unstable (it has been suggested that the macroscopic containment techniques developed by ASEABB in the early 2200s may have been based on the Livermore technology, but surviving records are unclear on this point). This was more than sufficient for Californian purposes however, and the first ACER round was demonstrated to the Californian National Guard Command on July 17, 2185 at 2:14 in the afternoon Pacific Standard Time. It has been said that the term "boom bullet" was coined and in general usage less than 12 hours later.

Californian dominance of boom bullet technology would serve the nation-state in good stead for several more decades, but by the early 23rd century CE, competition from other Terran nations, the rising power of the various orbital states, and the growth of their space based solar energy and amat production facilities ended first California's and then any Terran power's ability to effectively compete in the arena of anti-matter based weapons or power systems. The invention of the anti-matter flechette in 2275 CE was initially promoted by many (particularly the inventors) as a replacement for boom bullet technology, but in fact amat flechettes were never able to match the versatility and popularity of boom bullets, particularly in the arenas of surface and in-atmosphere combat.

Boom Bullets in the Modern Age

Although a vast number of weapons have been invented since the ancient days when the boom bullet was first conceived, it remains a common and popular component of military inventories across the Civilized Galaxy and beyond. Past eras have seen occasional attempts to heavily regulate or even ban the technology, but the ease of monopole production and the simplicity of the weapons design have made enforcement all but impossible without transapient intervention or assistance.

Barring the widespread application of such measures, the boom bullet seems destined to remain a part of civilized combat for a long time to come.

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Development Notes
Text by Luke Campbell, Mike Miller, and Todd Drashner
Initially published on 28 April 2010.