Spacecraft propulsion traditionally relies on volatile fuels and separate, bulky systems for different types of maneuvering in space. NASA is working to change that paradigm. Engineers at NASA’s Marshall Space Flight Center in Huntsville, Alabama, recently completed a rigorous series of environmental and physical tests on a new small satellite designed to make spaceflight safer and more efficient.
The ASCENT (Advanced Spacecraft Energetic Non-Toxic) Propulsion Dual Mode mission is a flight demonstration of a spacecraft about the size of a large shoebox. The mission will test a single, integrated propulsion system that uses a common fuel tank to feed two different types of engines.
Typically, spacecraft carry two separate propulsion systems to navigate: a high-thrust chemical system for rapid movements like entering orbit, and a low-thrust electric system for highly efficient, slow maneuvers like maintaining a position. This requires multiple fuel tanks and heavy plumbing, which eats up valuable space and weight.
The spacecraft being developed uses a single non-toxic propellant called ASCENT. By feeding both a high-thrust combustion engine and low-thrust electrospray thrusters from one central tank, the spacecraft saves critical mass and volume. For future missions, this means more room for scientific instruments and the ability to launch on smaller, less expensive rockets.
Bringing this concept to flight requires a nationwide collaborative effort. While NASA Marshall manages the mission, the spacecraft relies on electrospray thrusters developed by the Massachusetts Institute of Technology, a chemical propulsion module built by Plasma Processes, and a spacecraft bus integrated by the Georgia Institute of Technology.
“There are a lot of odds and ends, and a lot of small challenges and some big ones,” said Nehemiah Williams, the demonstration’s project manager at NASA Marshall. “But ensuring the functionality of the propulsion system across all these different teams is what makes the mission successful.”
Before a spacecraft can safely operate in the harsh environment of low Earth orbit, it must pass a battery of tests on the ground. Over the past few months, the engineering team at Marshall has put the flight hardware through its paces inside the center’s Small Spacecraft Servicing and Integration Lab.
To verify the integrity of the unified propulsion system, the team conducted extensive leak testing. Engineers performed a pressurized helium leak test of the spacecraft inside a vacuum chamber to ensure the integrity of the spacecraft’s seals, successfully proving those seals were working as intended. Because the system shares a single tank of ASCENT propellant to feed two different thruster types, ensuring that the fuel lines and valves are perfectly sealed is vital for mission safety and success.
The team also subjected the spacecraft to thermal vacuum testing. Space is an unforgiving environment characterized by a total lack of air and extreme temperature swings. By placing the spacecraft inside a specialized vacuum chamber that mimics these harsh conditions, engineers can ensure that the electronics, thrusters, and mechanical systems will operate normally once in orbit.
Additionally, the spacecraft underwent a spin test. Just like a tire on a car, a spacecraft needs to be perfectly balanced. The spin test measures the spacecraft’s mass properties and center of gravity. This validates the CubeSat’s ability to stably fly and maintain the correct attitude, allowing its antennas to communicate with Earth and its solar panels to accurately catch the Sun’s rays.
With the environmental and physical testing now complete, the mission is entering its final stages of preparation. The team will complete the final system checkouts, integrate the spacecraft’s solar arrays, and ship the hardware to its launch destination.
The ASCENT Propulsion Dual Mode mission is manifested to launch no earlier than October 1 as a payload aboard a SpaceX Falcon 9 rocket from Vandenberg Space Force Base in California.
Once deployed into an orbit about 325 miles above Earth, the spacecraft will begin a nine-month mission. After an initial checkout period, the operations team will execute short chemical and electric maneuvers. If successful, the spacecraft will spend several months performing multiple orbit-raising and lowering maneuvers, alternating between its high-thrust and low-thrust engines to prove the dual-mode concept works in space.
The ASCENT Propulsion Dual Mode mission is managed and funded by NASA’s Small Spacecraft & Distributed Systems (SSDS) within the agency’s Research and Technology Mission Directorate at NASA Headquarters in Washington. SSDS is based at NASA’s Ames Research Center in California’s Silicon Valley.
