Phase Four to Launch Monopropellant Multi-Mode Propulsion System

Phase Four has announced today the upcoming commercialization of its monopropellant multi-mode propulsion system. The new technology utilizes the Maxwell Block III, integrating monopropellant chemical propellants such as ASCENT and hydrazine with electric propulsion capabilities. The company plans to accept orders for these systems in the first half of next year.

Monopropellant multi-mode propulsion represents an advancement for satellite technology, offering a combination of the high thrust associated with chemical propulsion and the efficiency of electric propulsion. Traditionally, satellite propulsion systems require separate propellants for different modes, but Phase Four’s unique approach allows a single propellant to power both. This is made possible by the company’s proprietary radiofrequency (RF) thruster, which is capable of integrating chemical propellants into the electric propulsion system.

Ground demonstrations set for 2025

Phase Four will be supplying the electric propulsion component for ground demonstrations of both ASCENT- and hydrazine-based systems, with trials scheduled for completion by the end of the first quarter of 2025. These efforts are part of a partnership that includes the Department of Defense and private sector collaborators. The goal of these demonstrations is to validate the system’s capabilities and demonstrate its potential benefits for dynamic space operations.

ASCENT, a non-toxic propellant developed by the Air Force Research Laboratory (AFRL), is noted for its performance characteristics similar to hydrazine but without the stringent safety and handling requirements that hydrazine demands.

On the other hand, hydrazine is currently the most widely used propellant in commercial satellite operations. Integrating both of these propellants into a multi-mode propulsion system could significantly enhance the versatility of satellite missions, particularly in terms of maneuverability and endurance.

Benefits for satellite operators

The monopropellant nature of Phase Four’s Maxwell Block III offers substantial advantages for satellite operators. By relying solely on the chemical propellant, the system eliminates the need for auxiliary propellant tanks, such as those used for xenon or krypton in other multi-mode systems.

This design choice simplifies the propulsion system, making it lighter, smaller, and more cost-effective. It also reduces the logistical complexities associated with traditional electric propulsion systems, where supply chains for xenon and krypton pose ongoing economic and security challenges.

Umair Siddiqui, Phase Four’s President and CTO, highlighted the significance of this innovation: “We’ve been refining the state-of-the-art electrodeless RF thruster for nearly a decade. The absence of a hollow cathode allows our thruster to handle propellants like hydrazine and ASCENT more effectively than traditional electric propulsion systems.”

“We are excited to demonstrate this capability through direct integration with live propellants, in collaboration with the Department of Defense and leading chemical thruster suppliers,” he added.

Strategic development for national security missions

Phase Four continued investment in multi-mode propulsion capabilities, has a specific focus on meeting national security mission requirements, anticipated later this decade.

The company is testing a follow-on electric string thruster designed for multi-mode operations, which has already shown promising improvements in both thrust and specific impulse. The use of a single chemical propellant for both propulsion modes also simplifies on-orbit refueling, an important feature for extended mission lifespans.

“A true monopropellant multi-mode propulsion is a game-changer for space operations, and Phase Four is excited to bring this product to market,” said Steve Kiser, CEO of Phase Four. “By enabling a propulsion system to quickly and easily toggle between chemical and electric propulsion performance, Phase Four is bringing dynamic space operations (DSO) capabilities to both commercial and government programs now.”

Implications for the space industry

The introduction of a monopropellant multi-mode system marks a sharp separation from traditional satellite propulsion methods. As the satellite industry continues to evolve with an increasing number of small satellite constellations, the demand for more versatile and efficient propulsion systems grows.

Phase Four’s new offering could provide a viable solution to some of the challenges associated with traditional electric propulsion systems, such as the dependency on rare propellants like xenon and krypton, or Argon, like SpaceX’s Starlink constellation.

Furthermore, the ability to integrate ASCENT into multi-mode systems offers an attractive alternative for commercial and government operators looking for a safer, less regulated propellant. Given ASCENT’s non-toxic nature and similar performance to hydrazine, it could play a key role in future satellite designs that prioritize safety and sustainability without sacrificing performance.

The company aims to establish itself as a major player in the propulsion market.