Last week we re-released out Saronic Technologies profile ahead of the announcement the company is raising up to $1.5B in their Series D

This week, X-Bow Systems and SRMs. The activity of the weekend underscored just how central SRMs remain to U.S. missile employment.

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X-Bow Systems (pronounced "crossbow") is applying additive manufacturing, artificial intelligence, and digital engineering to the production of energetics and Solid Rocket Motors (SRM). From the Patriot PAC-3 to the AIM-120 AMRAAM and the LGM-30G Minuteman III, SRMs underpin the majority of U.S. missile capability across tactical, operational, and strategic domains.

Founded in 2016 in Albuquerque, New Mexico, X-Bow emerged from the recognition that U.S. energetics production had stagnated relative to operational demand.  CEO Jason Hundley brought military and Northrop Grumman experience while CTO Max Vozoff came from NASA JPL and SpaceX’s Dragon program. 

X-Bow initially pursued small launch services before pivoting toward a more foundational role: becoming a core supplier of solid rocket motors across the defense ecosystem.

In 2022, the company delivered its Rocket Factory in a Box (RFIB) to Air Force Research Laboratory at Edwards AFB and conducted the first launch of its Bolt rocket at White Sands Missile Range.

By 2024, X-Bow disclosed propulsion development efforts with the U.S. Navy for Mk 72 boosters and Mk 104 dual-thrust motors used in the Standard Missile program. Preliminary Design Review was completed in January 2026.

Meanwhile, the company installed its patented Additive Manufacturing of Solid Propellant (AMSP) production system at its Luling, Texas campus and has begun initial operational testing.

Traditional solid rocket motor production uses a "cast and pour" approach: propellant ingredients are mixed in large batches and poured into a motor case around a removable mandrel that defines the grain geometry.

X-Bow's approach extrudes propellant slurry through a print head, building the grain geometry layer by layer. The process can achieve complex 3D shapes that control the propellant's burn surface area. 

The July 2024 acquisition of Spencer Composites vertically integrated composite motor case production.  By bringing the production of high-strength composite motor cases in-house, the company eliminated a major source of external supply chain delay.

This is Part I of a two-part series on solid rocket motors (SRMs). This week is a primer on how they’re built and why geometry matters. If propulsion physics isn’t your thing, there are plenty of SRM burn videos here, here or here.

Part II next week moves upstream: suppliers, numbers, and chokepoints.

A Solid Rocket Motor is essentially a chemical energy storage device. It converts stored propellant into thrust through controlled combustion inside a sealed pressure vessel.

Every motor has four core elements:

Historically, casings were steel or titanium. Today, filament-wound composites like carbon fiber or Kevlar/epoxy dominate because structural weight = range. Every pound removed from casing mass becomes payload, maneuver energy, or additional kilometers downrange.

The insulation sacrifices itself during burn, charring and carrying heat away from the structure. In case-bonded motors, the propellant is cast directly against this insulation, eliminating voids and maximizing volumetric efficiency

The nozzle is, well, a nozzle. Throat diameter, expansion ratio, and material selection determine how effectively chamber pressure becomes velocity. A well-optimized nozzle doesn’t just “vent gas.” It actually translates stored impulse into reach.

But the heart of the motor is the grain geometry.

Unlike liquid engines, SRMs cannot be throttled. The thrust curve is programmed at manufacture. A star grain, finocyl grain, or other complex internal geometry determines how burning surface area evolves and therefore how thrust evolves over time.

Which Brings Us Back to X-Bow

Additive or digitally controlled grain manufacturing can potentially provide custom thrust profiling without redesigning the entire missile, faster design iteration cycles, reductions in cost per motor, and modular performance upgrades

This is beginning to matter in a very concrete way.

The U.S. air-to-air benchmark remains the AIM-120 AMRAAM, with extended-range capability emerging in systems like the AIM-174B.

China fields long-range systems such as the PL-15 and PL-17. Public reporting consistently frames these as outranging all current U.S. platforms by a not insubstantial margin.²

If incremental propulsion improvements can be introduced without wholesale missile redesign and full recertification cascades, performance gaps can potentially narrow faster than traditional acquisition cycles allow and at reduced cost of full scale missile redesign.

If X-Bow proves reliable, repeatable, and safe propellant production at scale, it becomes an enabling node in U.S. munitions replenishment and hypersonic supply chain resilience.

Its expansion across propulsion adjacencies (Standard Missile boosters (Mk 72 / Mk 104), large-diameter motors, GMLRS prototypes, igniters) is not diversification for its own sake but a  strategy to build steady production volume and utilization density across programs.

X-Bow's ability to translate development milestones into accepted production hardware will determine whether additive manufacturing becomes a genuine transformation of the energetics industrial base or a prototyping capability that supplements how America makes the propellants that drive its missiles.