Momentus’ Vigoride orbital transfer vehicle. Credit: Niall David / Momentus
The first test flight of a commercial orbital transfer vehicle from Momentus is suffering from a problem with its solar panels after launching last month on a SpaceX rocket, and the company said Monday that its confidence in completing the spacecraft’s demonstrations has “substantially declined.”
The Vigoride 3 space tug was one of dozens of small satellites launched on SpaceX’s Transporter 5 rideshare mission May 25. The spacecraft rode a Falcon 9 rocket into a polar orbit from Cape Canaveral, beginning a variety of communications, Earth observation, tech demo, and research missions.
Momentus intended to test the Vigoride spacecraft’s novel water-based propulsion system and deploy nine small customer-owned satellites from the transfer vehicle, but power and communications faults are preventing the mission from completing its objectives, the company said Monday.
“We are continuing efforts to address the anomalies, but our level of confidence that we will be able to deploy additional customer satellites from Vigoride and perform some planned operations of the vehicle on this test and demonstration mission has substantially declined,” Momentus said Monday.
Company officials said after the launch last month that the Vigoride spacecraft encountered “anomalies” in orbit. Momentus revealed details of the problems in a statement Monday.
“Of note, the deployable solar arrays that are produced by a third party and are folded and stowed during launch did not operate as intended once in orbit,” Momentus said. “This resulted in power and communications issues with the vehicle, even though the body mounted solar panels did operate as intended.”
Momentus, based in San Jose, California, did not identify the supplier of the deployable solar panels, but said engineers have identified a possible root cause for the problem with the arrays. The company believes it has also identified the root cause of other anomalies, which were not explained in Monday’s statement.
The Vigoride 3 mission was primarily intended to be a test flight for Momentus’ orbital transfer vehicle, but the spacecraft carried nine small satellites. Eight of the Vigoride passengers are “PocketQubes” measuring about 2 inches (5 centimeters) on a side, and the ninth payload is a slightly larger CubeSat about the size of a loaf of bread.
Two of the nine satellites deployed from the Vigoride transfer vehicle May 28, but Momentus said it has been unable to confirm any additional deployments. Momentus said it is no longer able to maintain two-day communications with the Vigoride spacecraft, which it said is likely due to the “low power situation” on the vehicle caused by the solar array problem.
Momentus said May 27 it was using an unplanned frequency to communicate with the Vigoride space tug. The company said it has received special temporary authority from the Federal Communications Commission to use the frequency.
The Vigoride 3 spacecraft’s water-fueled propulsion system has not been tested yet. Those demonstrations were scheduled after the deployment of the customer satellites.
Artist’s concept of a Vigoride orbital transfer vehicle with solar panels deployed. Credit: Momentus
“During this first launch of the Vigoride vehicle to space, we have learned a great deal and plan to incorporate improvements in other Vigoride vehicles currently being assembled and ground-tested. This was the primary purpose of this initial Vigoride mission,” said John Rood, CEO of Momentus, in a statement. “As we stated prior to the launch, we fully expected to experience challenges during this test and demonstration mission and to learn from them, which is what we are doing.”
Momentus said it plans to launch its next Vigoride orbital transfer vehicle on SpaceX’s next dedicated rideshare mission, Transporter 6, this November. The company said it plans to incorporate improvements to future Vigoride spacecraft based on lessons learned from the Vigoride 3 mission.
“Space is a notoriously unforgiving environment,” Rood said in a statement. “Like other companies that have worked through initial challenges to create successful capabilities, our engineering team at Momentus is focused on learning as much as possible from the remainder of the current Vigoride mission, and utilizing industry best practices to implement corrective actions and lessons-learned for our upcoming missions.”
Momentus’ orbital transfer vehicle is similar in purpose to space tugs developed by other companies, like Spaceflight and D-Orbit, both of which had their CubeSat carriers on SpaceX’s Transporter 5 mission last month.
The space tugs can change their altitude, inclination, or other orbital parameters, delivering small payloads to different locations in space than the drop-off orbit of the main rocket. The transfer vehicles can reposition small satellites into orbits more favorable for their missions.
Some transfer vehicles use conventional propulsion, with thrusters powered by liquid propellants. Others are testing electric thrusters, a lower-thrust but higher-efficiency propulsion option.
Rood said in an interview the launch last month that the water-based propellant used on Vigoride vehicle provides performance in a “sweet spot” between chemical and electric propulsion, with higher efficiency then conventional rocket fuels, and higher thrust than ion engines.
“It’s H20, it’s water as a propellant,” Rood said last month. “The way this works is similar to the microwave you use in your home. We use microwave energy with a magnetron to heat water vapor to a temperature that’s roughly half the temperature of the surface of the sun.
“The real science comes in to control that resulting plasma, making sure it doesn’t just melt through everything inside, including the nozzle,” Rood said. “And then controlling that plasma to expel it through the rocket nozzle to therefore produce thrust.”
The Vigoride 3 orbital transfer vehicle had an empty weight, or dry mass, of about 270 kilograms (about 600 pounds), according to Rood.
“This microwave electrothermal thruster technology has been in development since the 1980s by university researchers, but Momentus is a real pioneer in bringing it to the marketplace and using it in space.”
Momentus demonstrated a scale version of the thruster in 2019, but the propulsion system on the Vigoride transfer vehicle has many advancements over that test unit.
Momentus also booked a port on the Falcon 9 rocket to accommodate customer payloads, which deployed directly from the upper stage in orbit. The company said Monday that all four of the satellites on the other Falcon 9 port successfully separated from the rocket.
Momentus had to wait longer than it hoped to fly the the first Vigoride orbital transfer vehicle. An earlier version of Vigoride was originally slated to launch in early 2021. The U.S. government withheld regulatory licenses for the Vigoride demo mission, citing national security concerns stemming from the company’s original ownership by two Russian citizens.
The hold-up forced the Russian owners to divest their interest in Momentus, which is now a public company. Rood took the helm of Momentus last year, and the company secured U.S. government approval for the Vigoride 3 demo mission.
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