Phase Four, a spacecraft propulsion startup, has been awarded an Air Force deal to test an alternate propellant for its thrusters. The United States Air Force‘s AFWERX program awarded Phase Four a Phase 2 Small Business Innovation Research (SBIR) grant worth $750,000 on April 8 to evaluate using iodine as a propellant in the firm’s Maxwell electric thrusters. The grant would be used to develop a prototype of the thruster.
In an interview, Beau Jarvis, CEO of Phase Four, stated that iodine has a host of benefits over traditional propellants such as xenon and krypton. Iodine does not need high-pressure storage, saving weight and complexity, making it ideal for tiny satellites of limited mass and volume.
Given the smaller scale as well as complexity of thruster mechanism, as well as the reduced cost of iodine relative to xenon, that Phase Four has been utilizing with its Maxwell thruster, it may also be even less expensive. “The fluid side of the unit is mixed up with just over 50% of the bill: the holding tank, the high-pressure pumps, and the cost of xenon,” he added.
Iodine may be processed more densely and fuelled early in the launch loading flow due to the absence of high-pressure vessels. Because of the improved mass, spacecraft may hold more power, allowing them to do more maneuvers in orbit and saving propellants for end-of-life disposal maneuvers. “More effective smallsat propulsion solutions such as the radiofrequency iodine thruster would allow new missions in the remote sensing, space monitoring, and communications, among several other areas,” stated Umair Siddiqui, Phase Four’s chief technology officer.
Iodine, on the other hand, has a reputation for corroding thruster elements. “Iodine has a bad reputation for corroding cathodes. Iodine may be temporarily used in a legacy electric propulsion device, but it drastically reduces the lifespan because it corrodes the cathode, making it uncommercially viable,” Jarvis added. That is not a problem for Maxwell, which accelerates the propellant and generates thrust using radiofrequency technologies rather than cathodes. Under the Phase 2 SBIR award, Phase Four would show that in lab trials, and Jarvis stated the company aims to receive a bigger Phase 3 award to develop a flight-qualified variant of the iodine Maxwell thruster.
The first of Phase Four’s xenon Maxwell thrusters was launched on two satellites as a component of the SpaceX Transporter-1 rideshare project in January. Jarvis said the consumer for such thrusters would stay anonymous for the time being but that thrusters were doing admirably. “All of the evidence that our customer has provided with us from thruster firings in space matches what we saw in the lab during training and flight qualification,” he stated. Two more Maxwell thrusters have been built into satellites for deployment in May or June, bringing the total number of Maxwell thrusters deployed this year to ten. “Right now, we’re ramping up our manufacturing capability,” he stated, adding that he plans to hire a few more people.