Modular Propulsion: Optimizing CubeSat Volume Efficiency with Custom Tanks

CubeSat propulsion system with custom titanium propellant tank by SteamJet

Engineers often consider thrust, specific impulse, system mass, and total impulse when selecting a propulsion system for CubeSat. NASA’s Small Spacecraft Technology State of the Art report demonstrates that these are the key factors for small spacecraft propulsion systems. However, small satellites have another limitation that, in most cases, becomes the major one. Namely, the internal volume.

In simple terms, volume efficiency refers to how effectively the system utilizes the available space inside the satellite. If more propellant can be stored within the same CubeSat dimensions, the spacecraft gains additional maneuvering capability without increasing its external size.

As a result, this directly affects mission capability. If other parameters are unchanged, a larger usable propellant mass can increase the available ΔV margin. As a result, the satellite can support additional orbit adjustments, unscheduled maneuvers, extended mission duration, or end-of-life deorbit.

Therefore, engineers should evaluate not only the thruster parameters, but also how efficiently the propulsion system uses the satellite’s internal volume. A well-integrated fuel tank can enhance a mission’s capabilities even without modifying the engine itself.

Why Cold Gas Systems Limit CubeSat Volume Efficiency

In cold gas propulsion systems, the propellant remains in a pressurised gaseous state. The tank becomes a high-pressure container, rendering its geometric profile critical for uniform stress distribution and structural integrity under high pressure. Simple shapes, such as spheres or cylinders, are usually the most efficient for this type of tank. They distribute internal pressure better and help reduce structural risks.

However, for a CubeSat, it presents a design challenge. The interior of a satellite is typically rectangular and tightly packed with other systems, so a spherical tank does not fit well in such a space. There are empty spaces left around the tank that are impossible to use for payload, electronics, and additional propellant storage. Thus, even if a cold gas propulsion system fits well in terms of the thrust and the mass, its tank may be using the internal volume inefficiently.

Unpressurized Propellant Gives More Freedom in Tank Design

In SteamJet thrusters, the propellant is not stored under high pressure. Hence, engineers can design the tank in a wider range of shapes than in cold gas propulsion systems. This removes one of the main geometric constraints. A tank does not have to be spherical or cylindrical.

Instead, our engineers adapt tanks to the available space inside a CubeSat or Small Satellite. If there is an irregularly shaped space inside the unit, it is no longer a “dead space” but an additional propellant storage capacity.

Titanium Additive Manufacturing Enables Complex Tank Geometry

We use titanium direct metal laser sintering (DMLS) to manufacture tanks. It allows the production of tanks with complex shapes that are difficult or impossible to manufacture using traditional methods. Instead of adapting the satellite’s internal layout to fit a standard tank, the tank can be designed to fit a specific available space inside the satellite.

This is especially important for CubeSats and Small Satellites, where every centimeter counts. After electronics, payload, and other systems have been installed, the tank can be 3D-printed to match the space as precisely as possible. As a result, the satellite may carry more propellant without increasing its size.

Patented Tank Architecture Supports Сonformal Propellant Tanks for Small Satellites

Our patented tank design enables the engine to operate with tanks of various shapes, not just standard ones. This is important because the capability to 3D-print the tank doesn’t solve the issue. The thruster has to receive a steady supply of propellant and function properly with this configuration. The tank that may be adapted to the internal volume of the CubeSat or Small Satellite gives engineers greater flexibility when integrating the propulsion system.

More Usable Propellant Volume Without Increasing CubeSat Size

The custom tank’s main advantage is its capability to increase the volume of propellant without increasing the size of the CubeSat. It can replicate the available geometry inside the satellite. As a result, the custom tank converts more of the internal space into usable propellant capacity rather than remaining as “dead volume”.

For the mission, it means:

  • greater flexibility for orbit adjustments;
  • longer operational lifespan;
  • additional margin for unforeseen maneuvers;
  • the ability to perform deorbit at the end of the mission.

The deorbiting process is no longer optional. At the moment, it is a prerequisite. The FCC introduced a 5-year deorbit rule for LEO satellites, while ESA promotes sustainable mission design through its ESA Zero Debris Charter.

About SteamJet Space Systems

SteamJet Space Systems is a leading UK-based provider of high-performance satellite propulsion solutions. We specialise in green water propulsion for CubeSats  and Small Satellites (SmallSats), with a strong focus on 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.

Protecting Optical Payloads: The Clean Benefits of Water-Based Satellite Propulsion

Water-based satellite propulsion system supporting payload protection for sensitive optical instruments

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:

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.

Stationkeeping for 5G/6G Satellites: Precision in High-Frequency Orbits

Water-based satellite propulsion system for performing stationkeeping manoeuvres for a 5G communication satellite constellation

5G satellite networks and future 6G services grow rapidly, which leads to higher demand for the accuracy of satellites in orbit. Even minor deviations may alter the communication quality; thus stationkeeping, maintaining the satellite in the correct position, is an important task. To perform precise and effective stationkeeping, satellites need propulsion systems capable of regularly maintaining their orbits.

What Is Stationkeeping in Satellite Operations?

Stationkeeping is the process of keeping a satellite at a specific point in its orbit by performing small corrective manoeuvres. Unlike initial orbital insertion or daily attitude control (orientation), stationkeeping specifically focuses on maintaining the satellite’s geographic and spatial position over time. . It is necessary for a stable signal, reliable communication, and preventing interference between satellites. On top of that, stationkeeping helps to comply with orbital requirements, coordinate satellite constellations, and prolong the service life of the satellite. In order to do this, the satellites regularly perform different types of corrections: for latitude, longitude, and orbital altitude.

Why 5G/6G Satellites Demand Higher Orbital Precision

Modern satellite networks for 5G and future 6G services are not similar to traditional telecommunication networks. Big GEO-satellites are used to provide communications. Today, there is a greater dependence on large constellations of satellites in LEO and MEO orbits. As a result, the orbit becomes more congested, and satellite manoeuvres become more complicated.

High-frequency communication bands, such as Ka-band, V-band, and the future 6G band, require precise satellite position. These systems utilise high-frequency bands with highly directional, narrow communication beams, making them exceptionally sensitive to pointing and positioning deviations. Furthermore, modern satellites have to regularly perform orbital corrections, coordinate satellite constellations, avoid collisions, and compensate for the effects of atmospheric drag in low Earth orbit.

The Propulsion Challenge Behind Continuous Stationkeeping

Continuous stationkeeping requires a propulsion system, and for each orbital correction, some amount of propellant is used. At the same time, the precision of the manoeuvres depends directly on how precisely the thruster can control thrust.

Traditional propulsion systems are often difficult to operate. They use toxic propellant, necessitate an expensive integration process, and take up a lot of space, which is particularly critical for small satellites. In addition, such systems provide a limited number of manoeuvres.

Thus, new age satellite constellations need efficient systems with lower thrust that work well for frequent small corrections to ensure stable performance over a long period of time. They also have to be easy to scale for large satellite constellations.

Stationkeeping Economics in Large Satellite Constellations

When the satellite deviates from its orbit, it inevitably affects the coverage quality, increases collision risk, and reduces connection stability. Large satellite constellations face significant operational challenges in the case of even a small deviation.

The propulsion system allows for effective propellant usage and extends satellite service life. It reduces the need for recurrent equipment replacement, simplifies the management of large satellite fleets, and lowers the overall operating costs of the entire constellation.

Stationkeeping and Space Sustainability

Precise stationkeeping helps to prevent risks in the orbit because satellites avoid collisions and operate safely in constellations. This is particularly important given the growing number of satellites and the increasing congestion in orbit.

In addition to its role during the mission, the propulsion system is also important at the end of the satellite’s service life. It supports the controlled deorbit and compliance with space debris requirements. For future telecommunications networks, sustainability and zero-debris strategies are becoming increasingly important, and efficient propulsion systems play a key role in this regard.

Water-Based Electrothermal Propulsion For Future Telecom Constellations

This type of propulsion system is one of the most efficient solutions for future telecom satellite constellations. It allows for precise orbit correction with low complexity and safe operation. Water-based propulsion systems fit perfectly for frequent manoeuvres, and they reduce mission costs. On top of that, they support a more sustainable approach to the operation of large satellite constellations.

Comparison: Traditional Satellite Propulsion vs. Water-Based Systems

Propulsion Type
Propellant Hazard
System Pressure
Multi-Manoeuvre Capability
Constellation Scalability
Hydrazine (Monopropellant)
High (Toxic/Carcinogenic)
High
High
Low (Expensive integration)
Cold Gas
Low (Inert)
Extremely High
Moderate
Moderate (Heavy tanks)
Water Electrothermal (SteamJet)
None (Green/Safe)
Low (Stored as liquid)
High (Precise impulses)
High (Plug-and-play)

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.