As satellites grow smaller, faster to deploy, and increasingly autonomous, their propulsion systems must be equally agile and ready for action the moment they leave the ground. Whether enabling a longer lifespan, orbital adjustments, space tugs, or deorbit maneuvers, fuel is the lifeblood of satellite mobility. And fueling a spacecraft is one of the most critical and hazardous phases of pre-launch operations.
At Impulso, we support satellite missions end-to-end, including the delicate and highly specialized task of fueling. Here is what goes into it, and why our facility and team are perfectly positioned to manage it safely.
The Basics of Satellite Refueling
Satellite fueling is typically one of the final steps before a spacecraft is integrated with its launch vehicle. During this phase, propellants and pressurant gases are loaded into the satellite’s propulsion system, which will support in-orbit maneuverability throughout its mission.
A Standard Refueling Sequence Includes:
- Preparation & Safety Setup
The fueling operation begins in a controlled area monitored from a control room, using protective suits (SCAPE) if handling toxic gases, and specialized ground support equipment (GSE).
- Purge and Leak Checks
Inert gases like helium (He) and nitrogen (N₂) are used to purge the satellite’s fuel lines and propulsion system, removing contaminants and verifying system integrity.
- Fuel Loading
The propellant gas that will serve as fuel is now loaded into the satellite. An example would be propene (C₃H₆), a hydrocarbon gas used as a clean and efficient fuel, which our facility has loaded into satellites multiple times.
- Oxidizer Loading
The next step is loading the oxidizer. Liquid oxygen, Nitrous oxide, and hydrogen peroxide are some of the gases used for this purpose. During the entire process, they are pressurized and thermally stable, requiring rigorous safety handling due to their ability to decompose explosively at elevated temperatures.
- Pressurization & Final Checks
After propellants are loaded, pressurization and a series of final checks are performed. For larger satellites, particularly those destined for GEO, helium is used to pressurize the propulsion system. This crucial step ensures the propellants will flow correctly during thruster firings.
For small satellites, including CubeSats and nanosatellites, the approach to pressurization can vary significantly due to their stringent mass, volume, and power limitations, as well as the safety regulations regarding pressure vessels.
- Cold Gas Propulsion: Many smallsats utilize cold gas propulsion systems. In these cases, the propellant is stored at a relatively high pressure in a tank. The “pressurization” in this context refers to the initial filling of this tank to its operating pressure. As propellant is expelled, the pressure naturally decreases, and the system relies on this stored pressure for thrust. Therefore, active pressurization with a separate gas like helium is usually not required after fueling.
- Green Propellants & Other Chemical Systems: For smallsats employing more advanced chemical propulsion, such as “green” propellants or some monopropellants, these might be stored as liquefied gases under their vapor pressure. In these systems, heaters might be used to maintain a desired system pressure, especially for propellants that might otherwise have very low vapor pressure. While external pressurization might be used during ground operations for loading, continuous helium pressurization in orbit is less common compared to larger GEO satellites.
- Electric Propulsion: Many smallsats are now equipped with electric propulsion systems, which use propellants like xenon. While xenon is stored under pressure, the thrust relies on the electrical acceleration of ions, not a direct expulsion from gas pressure. So, the “pressurization” aspect is more about maintaining the storage conditions of the propellant, rather than actively pushing it through a combustion chamber.
Following these various pressurization strategies, a comprehensive set of final leak checks is conducted. The process concludes with safety lockouts, securing all valves and interfaces to prevent any accidental activation or tampering. These rigorous steps are essential to guarantee the satellite’s operational reliability and safety, regardless of the size or propulsion type.
Understanding the Hazards
The seemingly simple task of loading gas into a tank is, in aerospace, anything but. The substances involved are flammable, reactive, or both, and the systems operate under extremely high pressure (both figuratively and quite literally).
Potential hazards include:
- Fire and Explosion
- Propene (C₃H₆) is highly flammable and forms explosive mixtures with air.
- Nitrous oxide (N₂O), while non-flammable itself, is a powerful oxidizer. Under the right conditions, especially heat or contamination, it can decompose violently.
- High-Pressure Systems
All fueling operations are performed under high pressure. A leak, rupture, or valve failure can result in mechanical injury or the sudden release of hazardous gas.
- Asphyxiation Risk
Helium and nitrogen are inert but displace oxygen. In confined spaces, even small leaks can create a silent but lethal atmosphere without proper monitoring.
- Electrostatic Discharge
The flow of gases can build a static charge. Without proper grounding and bonding, this charge could spark ignition in the presence of flammable vapor.
How Impulso Ensures Safety at Every Step
At Impulso, our satellite fueling operations are carried out in a purpose-built facility designed specifically for safety, reliability, and mission success.
Expert-Led Operations
Our operations team includes specialists with years of experience of working in fueling protocols for various propellant combinations. Every campaign is overseen by our experienced personnel, who have worked across a range of satellite platforms.
Environmental Controls
All fueling is done under strict environmental parameters. Oxygen monitors, gas detectors, and controlled temperatures and airflow are standard operating procedures.
Compatibility with Emerging Propulsion Technologies
As propulsion evolves beyond traditional toxic propellants, our facility supports green propellants such as nitrous oxide/propylene blends, enabling efficient and lower-impact launches without compromising performance.
Fueling Tomorrow’s Missions
Satellite fueling may be just one step in a long chain of mission readiness tasks, but it is one that demands precision, discipline, and the highest regard for safety. At Impulso, we are proud to support missions of all scales with the infrastructure and expertise to make fueling safe, efficient, and mission-ready.
