ISS at assembly complete (Credit: NASA).

The propulsion system onboard the International Space Station (ISS) is vital to the safe operation of the spacecraft. Its primary purpose is to raise the ISS orbit to counteract drag and to control the orientation of the spacecraft. NASA Glenn Research Center’s Constellation Systems Project Office plays an important role in ISS propulsion by investigating safety issues related to the system and supporting international propulsion system developments.

ISS node, FGB, and Service Module (Credit: NASA).

The ISS propulsion system is located in several components including the Russian Functional Cargo Block (FGB) and the Russian Service Module. Due to orbital drag, the ISS loses altitude. Russian Progress vehicles periodically dock with the ISS to deliver propellant and move the ISS to a higher orbit or maneuver to avoid hitting orbital debris. Each component contains high pressure tanks of propellant used to power the thrusters and engines.

ISS Functional Cargo Block (Credit: NASA).

Two new uncrewed spacecraft are in development that will resupply the ISS. The European Automated Transfer Vehicle (ATV) will dock with the Service Module. This element will deliver supplies and propellant to the Service Module and reboost the ISS, providing more delivered consumables than the current Progress vehicle.

The Japanese H-II Transfer Vehicle (HTV) will deliver supplies to the U.S. segment and the Japanese Experiment Module. The HTV is not fired while attached to the ISS, but its system must satisfy requirements for safe approach and berthing.

ISS Progress and Service Module (Credit: NASA).

As these new supply vehicles are developed overseas, Glenn is working closely with Johnson Space Center and their International Partners to design test programs for the vehicles to address safety issues and ensure that the new hardware is fully compatible with the ISS. Glenn is also addressing operational issues and monitoring the activity of the Russian ISS hardware.

Transitioning to space exploration initiatives, Glenn has been chosen to lead the development of the Service Module for the Orion crew exploration vehicle. Glenn's work on ISS and previous experience with launch vehicle and satellite programs positions the center to provide key support to Orion for future exploration missions.