News Article

Phase Four's spacecraft engine first to demo AFRL's game-changing 'green' fuel
Date: Nov 04, 2022
Author: Theresa Hitchens
Source: ( click here to go to the source)

Featured firm in this article: Phase Four Inc of Hawthorne, CA

Former NASA administrator Jim Bridenstine told Breaking Defense that Phase Four has the potential to "disrupt the in-space propulsion market," and its technology "is important for the country."

WASHINGTON -- In a first, California startup Phase Four has successfully demonstrated that its novel spacecraft engine can run on a new "green" fuel created by Air Force Research Laboratory, company officials told Breaking Defense.

"This is a project that we've been working on with the Space Force for the past several months to validate that our thruster can take this green chemical propellant, create a plasma with it, and then we demonstrated operation at a variety of power levels and flow rates," Beau Jarvis, Phase Four CEO, explained in an interview on Monday.

Following the successful ground test, Phase Four is now working on optimizing its thruster parameters to best utilize AFRL's Advanced Spacecraft Energetic Non-Toxic (ASENT) propellant with an eye to a later on-orbit test.

Phase Four was one of three contractors to win a Small Business Innovation Research (SBIR) contract from AFRL's SpaceWERX at last year's Space Pitch Day.

It also has another SBIR from AFRL for investigating the use of iodine fuel with its radio frequency thruster, he said, as well as contracts with the Defense Advanced Research Projects Agency and commercial companies, like Capella Space, which is building large constellations in low Earth orbit.

The company's novel thruster design uses RF rather than a cathode to spark the fuel and create plasma that provides thrust, Jarvis explained. This allows it to run on ASENT -- developed by the lab as a non-toxic alternative to traditional hydrazine.

"Radio frequency electric propulsion that is fuel agnostic: xenon, krypton, iodine, hydrazine, ASENT, water, etc," he explained. Noting that Phase Four is already experimenting with the use of iodine, he added that iodine costs $150 per kilogram, compared with xenon at $30,000 per kilogram.

Unlike cathodes that can corrode when exposed to certain fuels, he said, Phase Four's RF thruster doesn't actual come in contact with the propellant at all.

"We actually embed an RF element inside the thruster. So we actually don't have anything that physically touches the propellant, which allows us to be propellant agnostic," Jarvis said. The RF mechanism in the engine he added, works in a similar manner to that used in a charging mat for a cell phone.

But more importantly, company officials said, Phase Four's technology is enabling the development of what are called multimode thrusters -- which in essence combine a chemical thruster with an electric thruster using the same fuel source.

Electric spacecraft propulsion systems are more fuel efficient. In engineering jargon they have a high specific impulse (Isp) but cannot generate enough thrust to allow a satellite to rapidly maneuver. Thus, they are usually used by satellite operators for the small orbital shifts required for day-to-day station keeping.

By contrast, on-board chemical thrusters, which rely on stored propellants, can provide a lot of thrust. The downside is they get pretty low gas mileage, and their tanks add a lot of mass/volume. (More mass equals more cost to launch.)

"From my perspective, the goal is to have a single propulsion system that can do both high thrust and high ISP," said former NASA head Jim Bridenstine, who is on Phase Four's board.

In fact, he told Breaking Defense, Phase Four is the only startup whose board he has joined, not only because of its potential to "disrupt the in-space propulsion market" but also because its technology "is important for the country."

Bridenstine said the combo of capabilities is a game-changer. "This is how it relates to the Department of Defense: We hear from the Space Force a lot [the need for] the ability to 'maneuver without regret'," he added.

"So, you need the high Delta-v in order to maneuver quickly -- in order to get out of the way of a threatened anti-satellite missile, maybe orbital anti-satellite capability, or maybe it's just debris, but you got to be able to move quickly, which means you need high thrust or high Delta-v," Bridenstine explained. "On the other hand, you also have to be able to operate normally, and for that you need high Isp, you need a very efficient rest capability that can last for long, long periods of time."

Further, he noted that typical thruster fuels like xenon and krypton are largely produced in Russia and China. And using water for fuel -- water that could be harvested from asteroids -- could enable cheaper space operations in cislunar space around the Moon, and farther out into the Solar System.

Jarvis said the company already has six of its smallest RF engines in what it calls its Maxwell series, operating on orbit for commercial customers -- running on traditional fuel -- and will have six more flying in the first quarter of next year.

"The current engine that we have operating in space is our first product, called Maxwell Block 1. It's about a toaster-size, turnkey system. So, it's basically a plug-and-play system that you put into a small spacecraft," he said.

"This year, we've just started delivering our second product, a product called Maxwell Block 2. It's a little bit larger because it's a more capable system," he added, explaining that Block 2 also sports a "flexible architecture" that allows spacecraft operators to decide how to configure the propulsion unit to fit their satellite.

Finally, Jarvis said, Phase Four is working on a future model that can provide much more power, "because that's where we see a lot of the both commercial market as well as the DoD market going with some of the new Space Force architecture" -- which puts a premium on resiliency, including both larger constellations and maneuverability even for some of its larger satellites.