Modern satellites rely on high-precision optical payloads, including Earth observation cameras, space telescopes, and scientific sensors, to capture critical orbital data. As these instruments become more advanced and expensive, payload protection has become a key consideration for mission designers and operators. While laser communication systems are now a core component of advanced small satellite architectures, these sensitive instruments face a critical risk from traditional spacecraft propulsion.
Exhaust plume contamination from chemical or electrothermal thrusters (including condensable outgassing products, hydrocarbon deposits, or backscattered erosion particulates) often stays unnoticed during the design phase, releasing particulates that degrade lenses, mirrors, and sensors. To protect these valuable space assets, mission operators are increasingly turning to water-based satellite propulsion as a clean, non-contaminating alternative.
Why Payload Protection Matters More Than Ever
Satellites carry valuable payloads with equipment that collect data for business, science, and different organizations. These systems include a diverse range of instruments. High-resolution Earth observation cameras and space telescopes form the core of these systems. Then there are infrared sensors, which can detect things that are invisible to conventional optics. And, of course, laser communication terminals.
This equipment performs multiple tasks simultaneously. Namely, tracking climate change, mapping out the surface of the planet, conducting scientific observations, and transmitting data back to Earth.
The success of the entire mission depends on the reliability of the equipment. A single failed sensor and years of preparation could go down the drain. So reliability here isn’t just a technical parameter, but a matter of paramount importance.
Problems that contamination may cause
Optical equipment is sensitive to any kind of contamination. Tiny particles on lenses, mirrors, or protective surfaces can seriously affect the quality of the image. Beyond optical throughput degradation, molecular deposition alters the α/ε ratio of thermal control coatings, inducing critical thermal drift in sensor calibration. Even sub-micron molecular deposition can degrade sensitive optical thin-films.
Contaminants alter the destructive interference properties of Anti-Reflective (AR) coatings – increasing straylight scatter – and distort the phase thickness of bandpass filters, leading to critical spectral transmission shifts and compromised sensor calibration.Sometimes, a speck of dust not visible to the eye is enough to cause the malfunction.
Over time, image quality deteriorates, data becomes distorted, and sensor accuracy declines. The need to calibrate the equipment arises more and more frequently. This process is gradual but inevitable. And the longer a satellite remains in orbit, the more noticeable the effect becomes.
How Traditional Satellite Propulsion Threatens Sensitive Payloads
When selecting the propulsion system, the focus is usually on thrust, efficiency, and fuel consumption. However, many thrusters produce particles and substances that may potentially damage sensitive equipment.
In chemical propulsion systems, the sources of contamination may be fuel combustion products and non-volatile residues (NVR). Sometimes, carbon-containing deposits may accumulate on surfaces.
Electrothermal thrusters can also generate contamination. During operation, certain components gradually wear down, and particles from them are released into the surrounding environment.
How Contamination Reaches Optical Instruments
Due to gas expansion in the continuum-to-rarefied transition regime, a fraction of the exhaust plume expands into the backflow region (>90° off-axis), directly impinging on spacecraft surfaces outside the nominal geometric plume cone.. And along with it, particles scatter and settle on everything they can reach: cameras, sensors, lenses, mirrors, and protective glass.
It might not seem like much. But month after month, year after year, that “little bit” turns into something that can no longer be ignored. For high-precision optical instruments, this is often enough to affect performance.
Real Risks for Mission Operators
Contamination of optical instruments may lead to lower quality of the images and reduced measurement accuracy. For communication systems, this can result in poorer signal quality, and for scientific missions, it can lead to a decrease in the reliability of the data obtained.
On top of that, operators have to take into account additional procedures to check and calibrate the equipment. In the long-term perspective, contamination may shrink the service life of the payload and the general value of the mission.
Water-Based Space Propulsion as a Clean Alternative
Water-based propulsion systems use water as a propellant. It is stored in the tank, then fed into the thruster and heated to a high temperature. This produces steam, which exits through the nozzle and creates thrust. It enables orbital maneuvers, satellite attitude control, and other tasks required during the mission.
The Unique Advantage of Steam Exhaust
One of the main advantages of water-based propulsion is the composition of the exhaust. When the engine is running, it emits mostly water vapor. Unlike traditional propulsion systems, water engines leave behind no hydrocarbon residues or chemical combustion products, which typically settle on the satellite’s surfaces. This means that cameras, sensors, and optical systems get much less contaminated. Cleaner fuel means cleaner equipment.
For missions where data quality is critical, cleaner exhaust can be a key factor in protecting the payload throughout the satellite’s operational life.
Payload Protection Benefits of Water-Based Thrusters
Exhaust fumes from water-based propulsion are cleaner, and there is a lower risk that contamination particles settle on surfaces. It helps to keep the lenses, mirrors, and protective glasses in better condition during the entire mission.
This is particularly important for Earth observation satellites and scientific instruments, as clean optical components help maintain high image and measurement quality for longer.
Improved Long-Term Sensor Performance
Less contamination means less stress on sensitive equipment. Sensors maintain their accuracy longer, and the need for additional calibration arises less frequently.
It might seem like a minor advantage. But in space, where every little detail matters, it makes a significant difference.
This helps reduce equipment degradation and keep consistent data quality even after many years of operation in orbit.
Lower Risk During Frequent Maneuvers
Modern satellites are constantly in motion, constantly making adjustments. Thrusters operate regularly: to maintain a given orbit, to transition to another, and to ensure coordinated operation within constellations. And a separate challenge is avoiding space debris, which is becoming increasingly abundant in orbit.
For non-cryogenic optical payloads operating above the water dew/frost point in vacuum, H2O molecules do not deposit or undergo polymerization, guaranteeing zero NVR accumulation.
Today, payload protection is an important part of the mission’s success. Even minor contaminants generated during engine operation can, over time, affect the performance of cameras, sensors, and other sensitive instruments.
Water-based thrust offers a cleaner alternative to traditional propulsion systems. Water vapor represents a transient gas phase that rapidly desorbs from warm optics once firing ceases, unlike sticky hydrocarbons. Because the exhaust consists mainly of water vapor, the risk of contaminating optical surfaces and degrading equipment performance is reduced.
About SteamJet Space Systems
SteamJet Space Systems is a leading UK-based provider of high-performance satellite propulsion solutions. We specialise in water-based thrusters designed specifically for CubeSats and Small Satellites (SmallSats), with a strong focus on water-based thruster safety.
By pioneering the use of green propellants and intelligent thermal engineering, SteamJet enables complex LEO (Low Earth Orbit) manoeuvres — including orbital maintenance, collision avoidance, and de-orbiting — without the risks associated with toxic hydrazine or high-pressure cold gas systems, advancing green propulsion for space missions.
Steamjet Propulsion Technology
Our modular systems are engineered for seamless integration and maximum safety compliance:
- Steam TunaCan Thruster: A compact, high-efficiency solution for 1U-3U CubeSats.
- Steam TunaTank Thruster: A safe, high-performance electrothermal propulsion system.
- Steam Thruster One: Scalable propulsion for larger SmallSat constellations.
Discover how SteamJet’s sustainable space propulsion innovations are providing the safety and reliability required for the next generation of crewed and robotic missions. Contact our engineering team for technical specifications and ICDs.