Maxwell thrusters
Phase Four's new Maxwell Block 2 electric thruster (left) next to its original Block 1 thruster. Credit: Phase Four

WASHINGTON — Phase Four announced June 16 two new electric propulsion systems that offer performance and other improvements, along with a subscription service that offers those thrusters to customers at a discount.

The company, which raised a $26 million Series B round June 11, said it now offers a Block 2 version of its Maxwell thruster, available for deliveries starting in the first quarter of 2022. A Block 3 version will follow in the second half of 2022.

The Maxwell Block 2 thruster is based on the technology in the original Maxwell thruster, now called Maxwell Block 1, that the company has flown several times. The Block 2 incorporates a new “chassis-style” design intended to make it easier to customize the thruster with different propellant tanks or other changes.

“For the Maxwell Block 1, the optimization was all around volume,” Beau Jarvis, chief executive of Phase Four, said in an interview. “The challenge with Block 1 was, can we fit this into the smallest form factor possible?”

Once customers started using Maxwell, he said, they asked for modifications, such as larger propellant tanks to increase the total impulse. “We needed to develop what we’re calling a chassis that allows us to on-ramp new subsystems, like the thruster or the electronics, without having to rebuild the whole product,” he said.

Another change in the Block 2 design is improved thermal management for the thruster. Jarvis said that enables longer continuous burns of the thruster.

The Block 3 version will feature a new power processing unit, the electronics that controls the thruster, while keeping the same overall form factor. “It basically doubles our specific impulse, twice the fuel efficiency that we have today,” he said. “It also raises the thrust level by 30-40%, so we’ll be able to provide significantly more thrust.”

Along with the new thrusters, Phase Four announced what it called P4 Pass, a subscription program where customers pay a fee to lock in low prices for thrusters and “priority placement” in the customer queue.

“The two things that customers have told us is, one, that the lead times for subsystems vary wildly, especially in electric propulsion, where the lead times are closer to a year or more,” Jarvis said. “The second thing is being able to establish a uniform price.”

Subscribers can lock in a low rate over a period of two to three years without having to pay upfront for a volume discount. “Customers that are in the P4 Pass program know that if they put in an order at the beginning of the quarter, they get their system by the end of the quarter,” he said. “A three- to four-month lead time doesn’t really exist today in the world of electric propulsion.”

Jarvis said the subscription program also benefits his company by helping it better forecast demand. “If we can forecast our supply chain further out, then not only can we secure our supply chain and not have hiccups, but we can also get better pricing for ourselves.”

Phase Four has discussed the subscription program with a few customers and gotten a “very positive” response so far. “The only concern that we’ve heard from customers is having too many people sign up,” he said. “This isn’t something that we can obviously offer to everybody, so it’s going to be first come, first served.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...