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Momentus Space was founded by space entrepreneur Mikhail Kokorich and his partner Lev Khasis in Santa Clara, California, in 2017. Momentus originated out of discussions with satellite operators seeking more affordable space transportation. Momentus is developing in-space propulsion systems powered by microwave electro-thermal (MET) water plasma engines. Momentus Space is the first in-space transportation services company built around high-performance water plasma rocket propulsion. Momentus’s water plasma propulsions systems use water that is cheap and nontoxic, and the system is considered safe and easy to work with. Water-based propulsion could provide a path to breaking the ties of space industries to the Earth by allowing resupply from asteroids.
Momentus Space is a developer of three critical functions of a potential space economy—space transportation, satellite as a service, and in-orbit servicing for constellations and for other space shuttles.
Momentus Space has engaged in a partnership with SpaceX since 2020. This partnership began in receiving service from SpaceX rideshare flights, in which the Momentus Space Vigoride transportation vehicles would carry payloads upon the SpaceX Falcon 9 launch vehicle. The Vigoride shuttle is then deposited in orbit. These missions were completed in 2020 and 2021, partly to help test and showcase Vigoride's capabilities.
The partnership continued when SpaceX, and Momentus Space signed a launch service agreement in which Momentus Space will fly on three missions with SpaceX in 2024, including the Transporter-10 mission slated for a January 2024 launch, the Transporter-11 mission targeting a June 2024 launch, and the Transporter-12 mission targeting an October 2024 launch. The launch partnership offers Momentus Space a chance for further testing and payload deployment on the Vigoride spacecraft, and further development on the Ardoride spacecraft.
Artist's conception of the Momentus Ardoride Orbital Transfer Vehicle
Momentus Space is based on over thirty years of university research funded by NASA and the US Air Force. Momentus Space also has several new patents pending. Momentus Space microwave electrothermal water propulsion systems use one-third of the propellant as chemical propulsion systems and deliver payloads three times faster than solar electric ion propulsion.
METs are plasma-based electrothermal devices that use joule heating of a partially ionized gas to heat un-ionized propellant which is then ejected through a converging-diverging nozzle to create thrust in the same manner as chemical rockets. The thruster body is a microwave resonant cavity that allows for microwave breakdown of virtually any gas-state propellant. Momentus is developing a MET system that uses water as the propellant in a highly localized region just upstream of the rocket throat. A combination of solar array power and batteries (depending on duty cycle) provides the energy necessary for operation. For their high-power systems, the microwave power to drive the system is generated by magnetrons, which are the highest known efficiency means of producing radiation from electric power and are highly mature in the terrestrial food preparation and materials processing industries.
Previous academic research and Momentus's in-house development efforts have shown that by carefully injecting the propellant gas with vortex inducing swirl, the gas discharge can be confined on centerline, where the microwave intensity is greatest, thereby inducing a strong radial profile in the gas temperature. Electron temperatures on centerline in the discharge can be as high as 15,000 to 20,000 kelvin, allowing heating of the centerline gas to several thousand kelvin while the boundary layer temperature of the gas that is in contact with the thruster throat can be within the long life temperature constrains of refractory metals.
Momentus's analysis and review of extant literature suggests that at achievable temperatures, specific impulses can approach 1,000s due to extremely high survivable bulk gas temperature and thermal dissociation of the water molecules to the atomic state. The following figure shows key design features of a Microwave ElectroThermal thruster showing the TM011 Mode Field Pattern in the resonant cavity. This cavity mode provides power coupling and positions the discharge in an optimal location upstream of the nozzle.
Key design features of a Microwave Electro-Thermal (MET) thruster showing the TM011 Mode Field Pattern in the Resonant Cavity.
The next figure shows how molecular dissociation of water serves to increase specific impulse at a given temperature beyond that which would be expected at 18 gImol for water by reducing the average molecular weight. The figure shows a plot of frozen flow, fractional dissociation, and thermal efficiency versus chamber temperature for an expansion ratio of 100:1 with water propellant as modeled in TDK, a two-dimensional kinetic code maintained by Sierra Engineering for combustion simulation. An 8,000K chamber temperature yields a specific impulse of about 750s.
Specific impulse (frozen flow), fractional disassociation, and chamber enthalpy to jet efficiency versus temperature for water propellant.
S-band MET Thruster in the lab.
The figure on the right shows an image of an S-Band (2.45 GHz) MET operating in the Momentus laboratory using water propellant at a power Level of 3 kW.
Choice of propellant is a primary cost driver, due to chemical properties, handling requirements, storage conditions, and many other factors, including the following:
- Safe and nontoxic to reduce labor facility costs to build, test propulsion systems, and eliminate concern of contamination for rideshare payloads
- Dense, easy to store and handle at standard pressure and temperature—to eliminate the need for high-pressure storage and feed system, which in turn enhances safety, reduces tankage mass, and reduces orbital debris risk in case of operational mishap
- Inexpensive, although at current satellite prices, propellant costs are typically a small fraction of total system cost. As the system cost comes down, more expensive propellants will be a high fraction of total system cost
- High in low atomic mass elements as is needed to serve as effective radiation shielding material to allow for synergy in structure design by using the propellant storage tank as both structure and shielding
- Available on the asteroids and planetary surfaces as a form of future-proofing against eventual in-situ resource utilization technology and as a way to enable resupply in space from locally available resources
Based on these criteria, water is a proposed ideal propellant, which is why Momentus selected to focus on water-based MET as its core technology.
In 2023, the MET was successfully tested, with Momentus Space completing an initial test sequence on-orbit of the MET on the Vigoride Orbital Service Vehicle (OSV). The test confirmed the capability of the MET in multiple test firings to impart the necessary forces to change and adjust the orbital velocity of the spacecraft, including changing parameters such as altitude and inclination. The tests were conducted using water propellant and not a modified version of the MET.
As shown in the following roadmap diagram, with Momentus's first orbital flight demonstration planned to be ready for launch in 2019, Momentus technology roadmap starts with the Zeal™ and Vigor™ technologies that they are adapting for flight. Momentus will be ready to start taking orders for small sat transportation services in Earth orbit for launch in 2020 or later with their Ardoride™ and Vigoride™ SmallSat space tugs. By 2021, Momentus plans to have Fervoride™ ready, which is a high-performance space tug designed to deliver a new generation of GEO sats. Momentus's roadmap includes Valoride™, a large-scale space tug designed to support space manufacturing, asteroid mining, and resupply for space hotels. Valoride™ is Momentus's proposed workhorse transportation service that ferries equipment and supplies throughout cislunar space and between LEO, GEO, and the asteroids.
Current roadmap of Momentus Propulsion System and Orbital Transfer Vehicle (OTV) Development, along with potential applications.
Vigoride OSV vehicle.
Momentus Space's Vigoride is an orbital service vehicle (OSV) designed to support a range of transportation and in-space infrastructure services. The Vigoride uses the MET thruster, with an aim of offering cost-effective, safe, and environmentally friendly propulsion for the demands of in-space transportation and infrastructure services.
The Vigoride was launched in 2022 for test flights aboard a SpaceX Falcon 9 launch vehicle. The inaugural mission of the Vigoride was to test the spacecraft in space, learn from any issues encountered to incorporate those lessons into future vehicles, and take customer payloads into orbit to generate revenue for the journey. The second test flight of the Vigoride sought to demonstrate the OSV capabilities with mission priorities, including the hosting of Caltech's Space-based Solar Power Project payload, deploying Qosmosys' Zeus-1 payload, and testing the Vigoride's performance in space.
The first Vigoride-5 test flight did show some issues. However, these anomalies seemed to be in the communications system of the Vigoride, which, according to Momentus Space, had been tuned incorrectly, and was operating slightly off compared to its FCC-licensed bands. Otherwise, any other anomalies were not commented on, except to say that they would inform the development of the Vigoride-6.
Following the successful tests of the Vigoride-5, Momentus completed work on the successor, Vigoride-6, which was delivered to the Vandenberg Space Force Base for integration on the SpaceX Transporter-7, and with a mission to deploy two cubesats for NASA's low-latitude ionosphere/thermosphere enhancements in density (LLITED) mission, which seeks to study conditions in the upper atmosphere, and other payloads for commercial and academic customers. The launch of the Vigoride-6 is anticipated to inform productivity gains in the production of the Vigoride-7, as the Vigoride-5 informed development of its successor. In July 2023, Momentus Space announced the successful launch of the Vigoride-6 payloads in orbit.
Ardoride space delivery vehicle.
The Ardoride space delivery vehicle is a refuellable vehicle designed to shuttle between different orbits around the Earth and the moon and is capable of lunar operations. The Ardoride is intended to extend the range and capabilities of the Vigoride OSV, with a focus on lunar exploration and operations in geosynchronous orbit. The Ardoride has been contracted by Qosmosys, after the success of the partnership for the Vigoride services, to bring the Qosymosys Zeus-MS multi-mission platform to the lunar surface. Similarly, Momentus Space signed a deal with the Canadensys Aerospace Corporation to launch a payload into low lunar orbit using the Ardoride space delivery spacecraft.
Slide showing planned Fervoride vehicle.
Momentus Space's Fervoride space shuttle is a planned development of the company's MET technology and to build upon the Vigoride and Ardoride space shuttle vehicles. The Fervoride is intended for deployment of large satellites from low-Earth orbit to geosynchronous orbit, potential moon exploration resupply, deep space missions, and deployment of asteroid mining structure. To do this, the Fervoride requires higher payload carrying capabilities with greater power generation and capability of in-space refueling from asteroids and other sites of space-ice.
