In recent times, many presentations on CubeSat propulsion have promised us a “green future”. At conferences, in white papers, and in promotional materials people talk about safe propellants, a sustainable space industry, and a new era of small satellites. However, when analysing the actual choice of CubeSat mission operators the picture is different. The market continues to choose between hydrazine, cold gas, and electric propulsion. On top of that, the main metrics continue to be specific impulse and flight heritage. “Green propulsion” stays on the slides, while decisions are made according to the familiar rules.
The main issue is that the industry talks about safe propellants on paper, but not in real-life business terms. A mission manager selecting a propulsion system faces various challenges. Namely, delays due to the coordination of hazmat procedures, refusals from rideshare providers, and ITAR restrictions when working with international partners. These costs determine whether a mission will launch on schedule or be delayed.
“Safe” isn’t just a fancy label. It means the absence of operational and regulatory risks all the way from the lab to orbit. And water-based propulsion is the only thruster that remains safe from ground operations to the final deorbiting manoeuvre.
What Does "Green" Actually Mean for CubeSat Propulsion
The term “green propulsion” emerged as a response to a real problem, the toxicity of hydrazine and everything associated with it. The idea was to find a propellant that is easier and safer to work with. But over the past ten years, marketing has overtaken engineering. Today, the word “green” is slapped on almost anything that isn’t hydrazine. Thus, the word has effectively lost its meaning.
The root issue is that the space industry defines “green” as a chemical property rather than an operational and financial reality.
A Mission Manager selecting a propulsion system isn’t just buying performance specs—they are managing launch delays, hazardous material (Hazmat) procedures, rideshare dispenser restrictions, and ITAR/export compliance. True safety isn’t a buzzword; it is the absolute elimination of regulatory, launch, and integration risks from the lab bench to orbital de-orbiting. Water-based electrothermal propulsion is one of the few architectures that delivers on all six operational fronts.
The "Greenwashing" Problem in Space Propulsion
The concept of “green propulsion” arose to solve a critical operational bottleneck: the extreme toxicity, complex handling, and expensive SCAPE (Self-Contained Atmospheric Protective Ensemble) suit requirements of hydrazine.
Over the past decade, however, marketing has overtaken systems engineering. Today, the label “green” is applied to almost any non-hydrazine system:
Energetic Monopropellant Blends
(e.g., ADN/HAN-based): Marketed as “less toxic,” yet still requiring high decomposition temperatures, energetic materials handling, elevated material compatibility testing, and complex thermal pre-heating.
Electric Propulsion (EP)
Non-toxic in storage, but introduces high power conditioning unit (PCU) overhead, complex EMC/EMI testing, high peak power draws, and extended low-thrust burn durations that complicate mission timelines.
Inert Cold Gas
Safe, but severely limited by low specific impulse (Isp) and heavy high-pressure storage tanks that introduce pressure vessel safety reviews (e.g., Range Safety pressure limits).
For a Systems Engineer, a “green” label on a spec sheet guarantees nothing about launch integration complexity. Mission success depends on launch provider sign-offs, range safety approval, integration time, and regulatory clearance.
What Actually Delays the CubeSat Mission
When selecting a CubeSat propulsion system, the discussion most often boils down to two parameters: specific impulse and unit cost. In practice, however, delays and budget overruns arise from entirely different sources. Namely, coordination efforts, ground operations, restrictions imposed by the launch provider, and regulatory procedures. These costs rarely appear in comparison tables, but they are precisely what determine the actual timeline and cost of a mission.
Hazmat approvals and ground operations
Handling toxic propellant requires specially equipped facilities, trained personnel, and specific transportation protocols. Fueling at the launch site requires a separate approval process. All of this takes weeks and costs tens of thousands of dollars, expenses that are not included in the engine’s specifications.
Rideshare rejections and placement restrictions
Launch providers are taking an increasingly strict stance on hazardous propellants. A satellite may be denied a preferred launch, placed into a less favourable orbit, or required to be isolated from neighbouring payloads. For CubeSats, this results in a direct mission delay.
Export Control & ITAR Bottlenecks
Thrusters bound by strict export controls limit international supply chains, restrict overseas testing, and introduce multi-month licensing delays for global constellation operators.
Thermal & Structural Qualification Overhead
Toxic or energetic systems demand extensive material compatibility testing and complex thermal management systems, lengthening the qualification loop.
It is precisely these costs that determine the true value of a propulsion system. From this standpoint, hydrazine, “green monopropellants,” and some cold-gas solutions have the same disadvantage of extra costs.
What “Safe” Actually Means for CubeSat Propulsion
In the industry, the word “safe” usually comes down to chemistry. Whether a propellant is toxic or not, or whether it’s explosive or not. This is important, but it’s just the tip of the iceberg. Chemical safety is a necessary condition, but it alone isn’t enough to ensure that a mission stays on schedule and within budget without any surprises.
When breaking down the concept of “safe” into actual processes that a mission manager deals with, a very different picture emerges. For a CubeSat propulsion system to be truly safe, it must meet six operational requirements:
- Safe to handle — requires no additional training for personnel, no special facilities, and no separate transportation protocols.
- Safe to integrate — compatible with standard satellite materials and standard assembly procedures, with no exceptions or additional testing required.
- Safe to launch — poses no issues for adjacent payloads and is accepted by launch providers without restrictions on rideshare placement.
- Safe to license — not subject to ITAR or other export restrictions, which is critical for international teams.
- Safe to schedule — does not entail lengthy regulatory reviews and does not delay the mission schedule by quarters.
- Safe to operate — requires no special precautions in orbit and poses no risks to other spacecraft.
It is within this framework that safety ceases to be a chemical characteristic and becomes an operational and financial metric. It directly affects the schedule, the budget, and the likelihood that the mission will take place as planned at all.
A water-based CubeSat propulsion system is one of those rare cases where all six levels of safety can be addressed simultaneously.
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.