The CubeSat Propulsion Guide: Choosing the Right Thruster for Your Mission

SteamJet TunaCan water-based CubeSat thruster

The CubeSat propulsion system is a critically important component that determines the satellite’s capabilities in orbit.

Orbital mobility encompasses active collision avoidance maneuvers (CAM), station-keeping, and post-mission disposal (PMD) to comply with international mitigation standards. In fact, a satellite is just a passive object in space without a propulsion system.

The propulsion system allows for expanding the range of satellite applications. As a result, the satellite can change its orbit to perform various tasks. In addition, it can participate in formation flying and extend the mission’s lifespan.

Today, a space mission has to comply with regulatory requirements that are increasingly stricter. Current international standards, the FCC introduced a 5-year deorbit rule and the ESA Zero Debris Charter, require operators to ensure that a satellite is deorbited after the end of its mission. Therefore, without a propulsion system, adhering to the new standards is impossible.

A CubeSat loses most of its useful functions without the propulsion system. And it can’t meet the modern requirements of the space industry.

Key Parameters to Consider When Choosing CubeSat Propulsion

Several critical characteristics directly affect the success of the mission. Thus, they have to be taken into account when selecting a propulsion system.

Thrust Level

Contemporary CubeSat propulsion systems offer a wide thrust range. From micro-newtons for electric thrusters (0.1 – 5 mN) to hundreds of millinewtons for chemical propulsion systems (100 – 1,000 mN). For instance, emergency evasion manoeuvres require high thrust. On the other hand, precise positioning needs low thrust.

Δv (Velocity Change) Budget

Δv (delta-v) is the primary indicator of a satellite’s manoeuvring margin. Engineers calculate it using the Tsiolkovsky rocket equation, which depends on the thruster’s specific impulse and the satellite’s propellant mass fraction.

Response Time

The time from receiving a command to the start of the manoeuvre can range from a few seconds to hours, depending on the type of propulsion.

If an emergency happens, for example, when operators receive a collision warning 12–24 hours in advance, the system must respond rapidly. It takes minutes to activate chemical and water-based systems. Electrical systems require a lengthy warm-up period and respond slowly.

Power Consumption

Different types of thrusters necessitate varying amounts of electrical power. Electric propulsion systems demand tens of watts of continuous power for hours or days. In contrast, chemical and cold-gas systems consume minimal energy, primarily for control electronics and valve actuation. Water electrothermal systems, however, require peak electrical power during operation to vaporize and heat the propellant, though their standby power remains low. 

Size and Mass Limits

CubeSats have standardised dimensions. Therefore, every cubic centimetre counts. In general, there are two ways to house a propulsion system. The first one is to place it inside the satellite and take up valuable payload space. Second is external mounting. It is also necessary to account for the mass of the system itself and the propellant supply. Typically, it ranges from 0.5 to 3 kg for a 6U satellite, which accounts for 5–25% of the total mass.

Safety & Launch Approval

Launch service providers impose strict safety requirements on propulsion systems. Firstly, the certification process for chemical systems is complex and lengthy. This propulsion system uses toxic propellant and high storage pressures (over 100 bar). Gas systems are approved more quickly and easily due to non-toxic propellants but high pressure.Water systems are the fastest to approve as a green satellite propulsion, since the propellant is non-toxic and is contained under lowest pressure.

Cost and Development Timelines

Commercial Off-the-Shelf (COTS) space hardware  is the optimal option for many missions. Its cost is $50,000–$200,000 and can be integrated in a few months.

On the contrary, in-house development is much longer and usually increases the overall price. However, for certain missions, it is justified.

Types of CubeSat Propulsion Systems

Chemical Propulsion

High thrust (100–1,000 mN) and rapid response, which is ideal for urgent manoeuvres. However, they have a few disadvantages. Namely, high toxicity propellants (e.g., hydrazine), complex fluid handling, and rigorous launch range safety certification (e.g., AFSPCMAN 91-710). Overall, this type of propulsion system is good for major orbital changes and emergency collision avoidance manoeuvres.

Cold Gas Propulsion

Cold gas propulsion systems are safe and easy to use. However, their main disadvantage is low efficiency (Isp ~50–70 s) and a requirement for a large fuel tank. As a result, these systems work well for demonstration missions and simple short manoeuvres.

Electric Propulsion (Ion, Hall, FEEP)

This type of thrusters have a high efficiency (Isp 1,500 – 5,000 s). However, its thrust level is low (0.1–5 mN) and energy consumption is high. Moreover, these systems have a slow response; it may take hours or even days to manoeuvre. Electric propulsion is well-suited for long-term missions, orbit maintenance, and slow orbital transfers.

Water Electrothermal Propulsion (SteamJet TunaCan, TunaTank, and Thruster One)

SteamJet thrusters are completely safe because they use water as a propellant at low storage pressure. The TunaCan thruster takes up zero internal volume (0U) because it is mounted outside the satellite. The thrust level is moderate (~20 mN), which provides a balance between speed and efficiency. Our water-based thrusters for small satellites  are perfect for 3U – 16U satellites to facilitate collision avoidance, formation flying, and rapid deorbiting.

Mission Profiles: Which Propulsion System to Choose

Mission Type
Key Requirements
Recommended Propulsion
Collision Avoidance (CAM)
High thrust, fast response
(<1–5 hours)
Chemical, Water-based
Station-Keeping
Moderate Δv, frequent small burns
Electric (Ion), Water-based
Orbit Transfer
High Δv budget
Electric (long burns), Chemical (fast), Water-based (fast, moderate Δv)
Deorbiting
Compliance with deorbiting requirements
Electric (high Δv, slow descent) or Water-based / Chemical (high-thrust rapid clearance)
Formation Flying
Precise, repeatable maneuvers
Water-based , Cold Gas
Technology Demonstration
Low cost, simplicity
Cold Gas, Water-based

Choosing the right propulsion system will determine the success of the entire CubeSat mission. And the system that fits all types of missions simply doesn’t exist.

For example, chemical propulsion systems work well for emergency manoeuvres. Meanwhile, electric propulsion systems are good for long-term missions with limited propellant supplies. Finally, cold gas systems suit simple demonstration projects.

Water-based electrothermal propulsion systems, such as SteamJet (TunaCan, TunaTank, and Thruster One), offer an optimal balance for modern compact satellites. They combine safety, fast response, sufficient thrust, and a compact design that doesn’t take up internal space – a critical factor for small 3U–16U satellites.

About SteamJet Space Systems

SteamJet Space Systems is a leading UK-based provider of high-performance satellite propulsion solutions. We specialise in water-based propulsion solutions designed specifically for CubeSats and Small Satellites (SmallSats), prioritising operational safety and rapid launch integration. 

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:

SteamJet TunaCan Thruster: A compact, high-efficiency solution for 1U-3U CubeSats.

SteamJet TunaTank Thruster: A safe, high-performance electrothermal propulsion system.

SteamJet 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.

Orbital Mobility for Nanosatellite Constellations: Propulsive Response Times in Active Collision Avoidance

Water propulsion system enabling orbital mobility for small satellites

Low Earth Orbit (LEO) is no longer an empty space.  Orbital Mobility has become a critical capability for satellite constellations operating in an increasingly crowded environment. The number of satellites and space debris has grown exponentially. Therefore, for satellite constellations, the ability to quickly change course and avoid potentially dangerous close encounters is becoming increasingly important. It is especially important for nanosatellites. Hence, the decision to manoeuvre often has to be made almost immediately. Because there is usually not enough time available between the warning and a potential collision.

A 6U CubeSat typically weighs around 12 kg. Avoiding a dangerous close approach depends on orbital calculations and on how quickly it can execute a manoeuvre command, which directly defines its orbital mobility capabilities. Slow reaction or low thrust leaves almost no time. Thus, when selecting a propulsion system, it is important to consider its practical effectiveness:

  • startup speed
  • thrust reserve
  • safety
  • compliance with mission requirements

For this reason, water-propulsion systems are particularly appealing. They provide small satellites and CubeSats with manoeuvrability without unnecessary risks or complications regarding launch clearance. Further, we examine the key characteristics of a water-propulsion system and show why it could be a practical solution for orbital mobility.

Space Sustainability Standards, CAM Distance and Orbital Mobility Timeline

Satellite operators activate pre-established safety protocols when the risk of a dangerous close encounter in LEO exceeds the acceptable threshold Pc > 10-4. They assess the situation according to strict criteria:

  • Miss Distance: to avoid collision, the operator has to determine in advance how close the two objects will pass each other. Also, whether the satellite will have time to change its trajectory. At the Time of Closest Approach (TCA), the safety radius between the centres of mass of the two encountering objects must be at least 1–2 km.
  • Trajectory Displacement: the satellite doesn’t need to change the orbit; the small manoeuvre is usually enough. Operators must alter the satellite’s path by 200 to 500 meters relative to its original trajectory.
  • The Planning Window: these situations shouldn’t be resolved at the last moment. The first warnings of a possible collision usually appear a few days in advance. Approximately 3 to 7 days before TCA. Operators make the final decision on the manoeuvre closer to the event, 24–36 hours in advance. The thruster itself is usually activated 12–24 hours before a dangerous close approach, so that the satellite has time to gradually move to a safe distance.

Propulsion Comparison: Finding the Best Thruster for Orbital Mobility in Small Satellites

For a 12 kg 6U CubeSat, the time it takes for the thrust to provide the nominal velocity change for a quick evasion manoeuvre (Delta V = 0.2 m/s) depends on the type of propulsion system used. The effectiveness of each propulsion technology directly impacts orbital mobility and the ability of a spacecraft to perform timely collision avoidance maneuvers.

Propulsion Performance Overview

1. Chemical thrusters deliver the highest thrust level (~1000 mN). This thrust level enables an extremely fast response — a Δv of 0.2 m/s is achieved in just ~2.4 seconds. These systems are highly responsive in emergency windows. They are capable of reacting up to 1–2 hours before TCA. However, the trade-off is complex integration: the propellants are hazardous and highly volatile, which complicates their use in a 6U satellite.

2. Cold gas systems offer low thrust (~10–50 mN). They require 48 seconds to 4 minutes to reach a Δv of 0.2 m/s. These thrusters remain robust in emergency scenarios, responding up to 3–4 hours before TCA. Safety is their main advantage. However, they are highly inefficient and consume a large amount of internal payload volume. It is a significant drawback for compact CubeSats.

3. The SteamJet TunaCan produces ~20 mN of thrust. Our thruster delivers a Δv of 0.2 m/s in ~2 minutes. It is dependable in emergency windows, responding up to 4–5 hours before TCA. Its standout benefit is the 0U design footprint. Zero internal volume impact makes it ideal for space-constrained missions.

4. Electric propulsion (FEEP/Ion) provides the lowest thrust (~0.4–1.2 mN). This kind of thruster needs 33 minutes to 1.6 hours to reach a Δv of 0.2 m/s. As a result, FEEP/Ion systems are ineffective for late-notice or urgent threats. On top of that, it imposes a high electrical power drain, forcing slow, multi-day tracking rather than rapid maneuvers.

Chemical thrusters respond quickly to imminent collision threats. Whereas electric engines (FEEP/Ion) are too slow for emergency maneuvers. The SteamJet TunaCan system offers the best balance of safety, response speed, and internal space efficiency. And it does not take up any usable space on the satellite.

Emergency vs. Nominal Manoeuvres: The Reality of Orbital Risks

There are two categories of risk collision based on the analysis of manoeuvres in low Earth orbit. These scenarios demonstrate why orbital mobility is becoming an essential requirement for modern satellite operations.

1. Nominal/Planned Manoeuvres, 95%–97% of cases
In most of the cases, the operator receives a warning in advance. Therefore, the satellite has enough time to avoid collision. Under these conditions, high-thrust systems and water-based electrothermal thrusters produce nearly identical practical results.

2. Emergency Manoeuvres, ~3%–5% of cases
Situations like this happen when there is almost no time left to react. Several reasons may lead to these situations. For example, radar blind spots, solar activity spikes expanding the upper atmosphere, or sudden data revisions in Conjunction Data Messages (CDMs) less than 24 hours before TCA.

The TunaTank Advantage: Next-Generation Water Propulsion Technology

Although electric propulsion (FEEP) has a high specific impulse, its thrust is in the micro-newton range. Hence, it is not well-suited for rapid manoeuvres. The corrections have to be planned days in advance. On top of that, the system consumes valuable power from the onboard batteries in the process. Conversely, chemical thrusters present additional challenges. Primarily in terms of safety during storage, launch, and operation.

The TunaTank Thruster is our new water-based propulsion system. We developed it based on our experience with the TunaCan Thruster. The system supports small satellites and gives them more capabilities without unnecessary risks. In fact, TunaTank offers a perfect balance between effectiveness and safety.

  • Clean Propulsion Technology: runs on water, a non-toxic, “green” propellant stored at low pressure.
  • Space Qualified Reliability: designed according to  ESA ECSS and NASA GSFC standards.
  • Flight-Proven 3D Printing: custom printed manifolds allow the system to be adapted to the layout of a specific CubeSat.
  • Uncompromised Volume: The external scalable architecture preserves the satellite’s internal volume for the payload.

About SteamJet Space Systems

SteamJet Space Systems is a leading UK-based provider of high-performance satellite propulsion solutions. We specialise in water-based propulsion solutions designed specifically for CubeSats and Small Satellites (SmallSats), prioritising operational safety and rapid launch integration. 

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:

SteamJet TunaCan Thruster: A compact, high-efficiency solution for 1U-3U CubeSats.

SteamJet TunaTank Thruster: A safe, high-performance electrothermal propulsion system.

SteamJet 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.