There is growing demand for in-space propulsion systems that enable small satellites to achieve attitude and orbit control, orbital transfers, and end-of-life deorbiting.
This is particularly important for the slew of LEO and MEO constellations currently being developed, as constellation control will be an important factor in the success of these ventures.
Over the past decade, there has been an explosion of activity in the smallsat propulsion world, driven by technology breakthroughs, industry commercialization, and private investment.
In this article, we provide a gentle primer to the topic of selecting a thruster for a smallsat mission, and give an overview of some of the propulsion products making waves within the global marketplace for space.
Do you know of any smallsat thrusters that we’ve missed? Please drop us a note at [email protected] or on Twitter. Alternatively, if you’d like to list your products and services on satsearch, get started here.
Selecting the most appropriate thruster product for a CubeSat can be a tricky challenge.
Rapid growth of the NewSpace sector has led to greater use of modular components, like thrusters. Picking the right thruster is imperative towards ensuring success of your CubeSat mission.
In this article, we look at some of the factors that should be taken into account to make this decision. We also provide an overview of a number of propulsion products on the market, listed on the satsearch platform to help you select the best option.
Your CubeSat thruster requirements
We recommend a simple 4-step approach for a preliminary selection of a thruster for a CubeSat, as explained below:
- Specify your exact mission parameters
- Record all known design specifications of the CubeSat
- Consider the range of technology that will be used in the system
- Take into account the key performance criteria
Your mission parameters
The first step is to fully understand the full set of mission parameters, including both the critical applications and desirable, but not necessarily essential, objectives.
Knowing exactly what functions your thruster will need to perform, and on what schedule and duration, will make selecting a model easier.
Also consider the launch stresses, testing processes and regulatory compliance that the CubeSat will need to go through, in order to make it into orbit, as well as any obsolescence procedures once the mission is complete.
Your CubeSat’s physical specifications
Next, keep to hand all currently known design information about the CubeSat unit.
This can include the volume, weight, primary structural material and more basic things such as the location, storage and transport arrangements of the major components.
You will need to make sure that the thruster you choose will be suitable for these parameters.
Your full range of tech
Once you are clear on exactly what tasks the thruster will need to perform and the design characteristics of the CubeSat, the next consideration is the technology that will sit alongside the thruster to make sure everything is compatible (and fits in the unit in the first place!)
You may not yet know the full range of accompanying tech (and you might need to first choose the thruster in order to make decisions on other components), but make sure you have access to the technical specifications of all the other sub-systems and structural components that are most likely to be used per the current plans.
Key performance criteria
Now you’re armed with the knowledge of what the thruster needs to do, work alongside and fit within, you can make an informed decision from the available products, based on your required performance characteristics.
Some of the potential key specifications and performance criteria to evaluate are:
- Size and weight - Will it fit? Is it too heavy? The physical volume (usually expressed in CubeSat units / U) and on-Earth weight determine what other components can be used in the unit and impact transport and launch costs.
- Specific impulse - What specific impulse values are required for your CubeSat and intended applications?
- Electric or chemical - This is a big debate and beyond this article to go into in detail. Both classes of propulsion technologies can perform very well for CubeSats and should be evaluated for any potential system.
- Flight heritage - Is this thruster fully tested in space? You need to know that the system will survive the launch and operate as expected in microgravity, so it is important to look at the product’s history.
- Operating power - What power supply can your CubeSat use to operate the thruster? What input will work best with other systems and maintain safety and efficiency?
- Thruster delta-V capability - What changes in velocity does the thruster need to produce in order to carry out the maneuvers required in the mission?
- Integration requirements - Do you require a simple plug-and-play system? Or do your CubeSat’s needs and mission parameters dictate a more customizable solution?
These provide a snippet of the technical details that are necessary to evaluate as part of your selection process. In addition, there are the typical criteria for any major purchase such as; cost, delivery time, supplier reputation and location, contract details and maintenance conditions to take into account.
Finally, it’s important to know that selection of a thruster for your CubeSat is an iteratively process, as is the case for virtually every other component of your overall system.
CubeSat thrusters on the market
Below we have listed several CubeSat thruster products that are currently available.
Please note that this list will be updated when new products are added to the global marketplace for space - so please check back for more.
The PM200 brings high thrust propulsion capability to 3-12U CubeSats. Low system complexity and zero propellant toxicity allow for simple and robust operations, both on the ground and when in orbit. The medium tank pressure and high storage density of liquid propellants enable high safety factor tanks to be used with little mass penalty. The standard 1U configuration of the PM200 propulsion module can deliver in excess of 230 m/s of velocity increment to a 3U CubeSat of 4 kg at a nominal thrust level of 0.5 N. The system can be seamlessly integrated with the iADCS400 to provide a fully integrated GNC and ADCS solution. In addition, the PM200 offers active thrust vector control to minimize disturbance torque on the satellite platform.
Based on helicon technology, the REGULUS system is a magnetically-enhanced RF plasma thruster designed for small platforms; characterized by low power and budget constraints. Due to its simplified architecture the thruster allows for cost reduction, making it a valuable solution for small platforms down to multi U. The system is throttleable and is easily scalable to match with the customer needs, while being composed only of a discharge chamber, an antenna and a magnetic field generator. It does not use electrodes, does not require neutralizers and grids, thus allowing cost reductions and long lifetimes. A proprietary (patented) helicon technology has been developed specifically for micro and nano-satellites.
Morpheus’ FEEP technology has been specially developed for miniaturized applications using the low-melting metallic gallium propellant, as well as a chip-based neutralizer with the corresponding supply and control electronics. All of the system’s components are optimized to deliver the best propulsion performance for the least amount of space, mass and necessary electrical power, which are the most valuable commodities on board a nanosatellite. Due to the system’s plug-and-play nature the integration into a satellite platform is easy and highly customizable in order to fulfil the propulsion requirements of almost all low Earth orbit missions. The modular thruster system can be purchased as a single system, the nanoFEEP, or several units may be combined for more complex requirements in the multiFEEP.
NanoAvionics offers a high-performance and environmentally-friendly propulsion system for small satellites that is compatible with CubeSats. The system has the potential to unlock relaunch savings for satellite operators by an estimated 80%.
The propulsion system is modular in design and can be scaled by adjusting the volume of the tank to accommodate different propellant quantity needs. The system uses “green” ADN-based monopropellant which has a 6% higher specific impulse and 24% higher energy density compared to hydrazine-employed systems, enabling significant levels of thrust in a relatively small storage volume.
The TILE 500 and TILE 5000 by Accion Systems
Accion’s TILE products require no gas-phase ionization, which means the ionization chamber is orders of magnitude smaller compared to plasma-based electric propulsion systems. As an example, a XIPS-25 gridded ion thruster requires an ionization chamber roughly 250 mm deep whereas an Accion TILE system only requires a depth of 2 mm and enables much more compact and volume-efficient configurations.
TILE systems are optimized for a high thrust-to-power ratio as there is no on-orbit ionization and no external cathodes, propellant heaters or other components that draw additional power from the spacecraft. The passive nature of the ionic liquid propellant removes the need for bulky, heavy valves and propellant feed systems, which also means that TILE has simpler safety requirements, reducing costs over the program lifecycle. Removing the need for these additional components also means that the TILE design is optimized for high thrust-to-power.
Edit: 31 July 2019 - please note that this listing has been updated to more accurately reflect Accion Systems’ current in-space propulsion products.
One of the highest thrust electric propulsion systems on the market – able to dramatically reduce the time needed to carry out propulsion while maintaining a high total impulse density to minimize the impact on your system. The ExoMG® is a Hall Effect Thruster (HET) - an ion thruster in which electrons emitted by a cathode are trapped in a magnetic field and used to ionize a propellant. Due to unique innovations of the plasma chamber, the cathode and the fluidics system Exotrail has been able to reduce the size of this technology to fit small satellites.
The NPT30 is a standalone electric propulsion system for small satellites that can deliver high ∆V. ThrustMe challenged the fundamentals of electric propulsion and miniaturized the system by innovating in how propellant is stored, handled and accelerated. Combining ion thruster technologies with techniques derived from the semiconductor industry enabled high-performance miniaturization. The NPT30 is at TRL6. No performance degradation has been observed after hundreds of hours of operations and hundreds of ON/OFF cycles.
With a controllable specific impulse of up to 5,000 seconds, the IFM Nano Thruster features an efficient ionization process that allows ionization up to 60% of the evaporated Indium atoms. The system offers a higher specific impulse than most other ion propulsion systems currently on the market. The thrust can be dynamically controlled through the electrode voltages, providing excellent controllability over the full thrust range and giving a low thrust noise. The system also features two cold-redundant electron sources acting as neutralizers. More than 100 emitters have been tested and an ongoing lifetime test has demonstrated more than 18,000 hours of firing without degradation of the emitter performance.
Flight heritage: 25 IFM Nano thrusters have been used in space to date with many more already delivered and waiting for next launch.
Edit: 2 August 2019 - please note that at the request of Enpulsion the image of the IFM Nano Thruster was updated to a more recent and representative version.
Comet CubeSat and Microsatellite Water Thruster by Bradford Space is a simple, launch-safe, and cost-effective electrothermal propulsion system that uses water as a propellant. Comet thrusters are the ideal balance of cost and performance, occupying a place in the market between low-cost, low-performance cold gas and resistojets, and high-cost, high-performance monopropellant and electric systems. The Comet design is scalable from CubeSats to small microsatellites, with a highly-flexible interface suitable for a wide range of spacecraft sizes. Comet thrusters are inert, launch-safe, and also safe for deployment from the International Space Station.
Edit: 4 August 2019 - please note that at the request of Bradford Space this product listing was updated to the latest details on the Comet system.
ExoTerra Resource’s Halo is a miniaturized centerline-cathode Hall-effect thruster that uses magnetic fields to focus and accelerate a plasma to generate thrust. The Halo system operates on a flexible range of inert gases and storable propellants without combustion. The current version of Halo has demonstrated operation between 75 and 400 W with thrust ranging from 4 to 34 mN and Isp from 700 s to 1500 s. Designed for CubeSats, Halo fits within a 7.5 cm diameter by 4 cm long volume (excluding mission unique gas fittings), and weighs just 0.6kg.
Tethers Unlimited offer the HYDROS™ high-performance propulsion for small satellites. The thrusters use a hybrid electrical/chemical scheme to provide small spacecraft with both high thrust (≥ 1.5 N) and high Isp (≥ 310 s) propulsion. HYDROS propulsion systems enable secondary payloads to perform missions requiring orbit agility and large ∆Vs while launching with the ultimate ‘green’ propellant, water.
Bellatrix Aerospace has developed and patented Microwave Electro-thermal Thrusters (MET), an advanced type of electric propulsion for satellites. This is an efficient electric propulsion system and has a unique distinction of being able to efficiently work on several propellants such as Argon, Xenon, Nitrogen, Ammonia and Water Vapour. MET is an electrode-less (zero erosion), vortex-stabilized thruster where microwaves are used to heat the propellant and produce a high temperature exhaust for in-space propulsion.
Maxwell is a turn-key electric propulsion solution for next generation small satellites. It includes propellant (and control system) and a proprietary RF thruster. Maxwell is a 300-500 W class engine providing propulsion for small satellites (20-500kg) that was designed, built, tested in under 8 weeks. It provides a thrust output of 6-10 mN and has a specific impulse of 7,000-14,000 Ns.
Edit: 11 July 2019 - please note that previously in this section the CubeSat propulsion product called Rider, manufactured by Phase Four, was listed. This listing has been removed, as Rider has been obsoleted and replaced by Phase Four’s Maxwell thruster.
The Orbital Thruster is a miniaturised resistojet propulsion module that uses water-based propellant. The OT module is designed to be plug-and-play ready, as only power and connectivity wiring are required from the satellite. Although featuring a much reduced volume the OT is still estimated to provide enough propellant for 100 firings in the the nano-size variant making the product highly suitable for propulsion experiments and orbital adjustments prolonging satellite’s lifespan.
The B125 SmallSat Bipropellant Thruster and DFAST CubeSat Warn Gas Thruster by Benchmark Space Systems
Benchmark Space Systems manufactures scalable thrusters with additively manufactured core components that can be easily configured for individual spacecraft to large constellations. The products use gaseous propellant and are available in two core models:
The B125 SmallSat Bipropellant Thruster delivers a non-toxic (‘green’), high thrust propulsion system for small satellites. The proprietary, on-demand pressurisation technology and use of non-toxic propellants are designed to ease the launch manifest and expand the operator’s capabilities. In addition, Benchmark Space’s patent pending micromixing technique eliminates the need for catalyst beds, which are a high cost, long-lead, and high-power consumption component used in other systems in the class.
The DFAST CubeSat Warn Gas Thruster product line was developed to provide reliable, high-precision positioning and control capabilities with high levels of safety and affordability.
Currently in development. SteamJet’s TunaCan propulsion system is designed to provide safe, compact and affordable water-based propulsion for smallsats and CubeSats. The product is being developed along with tungsten carbide manufacturing firm Total Carbide and a prototype of the system will be tested in space-simulated conditions in March 2020, with a patent also due to be filed.
Edit: 27 January 2020 - the TunaCan propulsion system by SteamJet Space in-development product listing was added.
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