SBIR-STTR Award

Ad Astra Rocket Company proposes a novel method of manufacturing a VASIMR® coupler. This method intends to increase the surface area in contact between the actively cooled coupler and the plasma facing GCT resulting in a lower heat flux between the components, lower temperature on the GCT, higher operational temperature margin, and ultimately a higher steady-state operational power limit of 100 kW for the VX-200SS™ prototype. This innovation is anticipated to increase the contact surface area by a factor of 3 and lower the temperature of the full-scale Ion Cyclotron Heating (ICH) GCT by roughly 40%. This manufacturing method will first be applied to a small-scale coupler assembly that will then have its thermal performance experimentally verified and compared to a traditionally-manufactured small-scale coupler assembly. At the completion of the Phase I work, Ad Astra will provide a small-scale prototype demonstrating the viability of the manufacturing method and a report that contains experimental data, simulation results, analysis, predicted thermal performance of the full-scale ICH coupler assembly, and a design/test plan for thruster-level integration and demonstration to be implemented in Phase II. This maturation of the VASIMR® engine will move it closer to commercialization. The VASIMR® engine is a high-power electric propulsion system approaching TRL 5. Past prototypes have exceeded many key performance parameters detailed in the National Academies' "Space Nuclear Propulsion for Human Mars Exploration" 2021 report and are anticipated to exceed them all. The VX-200 VASIMR® prototype operated at 200 kW of electrical power at 72% efficiency and a specific impulse of 4, 900 seconds. VASIMR® engines can use many propellants including argon and krypton. The TC-1Q first flight unit is expected to operate at 150 kW electrical power, readily be clustered to exceed 1 MW, have a specific mass of 4 kg/kWe, and have an operation lifetime of 10 years. Anticipated

Benefits:
Cislunar cargo transfer, space debris removal, Mars mission (cargo, crew), deep space uncrewed missions, asteroid mining/deflection High-maneuverability satellites, in-space manufacturing logistics, lunar settlement cargo delivery, private space station positioning

The proposed work on Phase II involves the design, manufacture, and test of a full-scale embedded RF Coupler for the plasma “heater” stage of the VX-200SS™ VASIMR® rocket core. The RF Coupler is a critical power component of the engine and, specifically, the heater stage RF Coupler delivers the largest fraction of the power to the VASIMR® plasma. In 2021, an earlier innovation to the design of the RF Coupler-GCT assembly, called the “Trapped Coupler,” enabled the VASIMR® VX-200SS™ test article to reach thermal steady-state at a company record of 80 kW. With the “Embedded Coupler” design, the proposed innovation in Phase II of this SBIR, and the knowledge obtained from Phase I, the Ad Astra team looks to increase that power to ?100 kW, an objective relevant to the Phase I Solicitation Subtopic, High-Power Electric Propulsion Thrusters for Mars-Class Missions. In a “Trapped Coupler,” all heat coming from the ceramic must pass through its inner diameter surface. In contrast, the Embedded Coupler uses its walls as two additional surface heat pathways. Theoretical estimates conducted by the Ad Astra team show that the heat transfer area in the embedded design increases by roughly a factor of 3 and results in a lower steady-state temperature for the GCT. To accomplish this, the RF Coupler will be machined-in-place in a high-purity copper vein pattern cast on a ceramic GCT host. The coolant within the coupler flows along two stacked counter-flowing channels, a feature required by the current RF electrical circuit. Other potential designs for this channel structure are possible and being explored outside of this SBIR but, in all cases, the manufacture requires a high-precision welding technique that Ad Astra has developed in-house and successfully demonstrated in the Trapped Coupler configuration. Anticipated

Benefits:
- Lunar resupply missions with high-power solar and nuclear electric propulsion (SEP/NEP) - Fast interplanetary robotic science missions with high-power NEP - Cislunar NASA in-space transportation with high-power SEP/NEP - Planetary defense missions with high-power SEP/NEP - Orbital debris mitigation (could also be non-NASA) - Multi MW-class human fast interplanetary missions with high-power NEP - Lunar resupply missions with high-power SEP/NEP - In-space "mining" missions with high-power SEP/NEP - Cislunar commercial in-space logistics with high-power SEP/NEP - DoD cislunar robotic applications with high-power SEP/NEP - Mission extension, resupply, maintenance and repair vehicles with high-power SEP/NEP - Reboost and orbit maintenance of large space stations in LEO with high-power SEP