I am curious about how much potential would a hybrid (electric & chemical) micropropulsion system have for CubeSats.

The chosen propellant is water due to its non toxic nature, cheap cost and high Delta-V. Besides, it can be disassociated, by applying external electrical power, into hydrogen and oxygen. These two would react in a combustion chamber (chemical propulsion).

Nanosatellites such as CubeSats impose strict requirements in terms of mass, volume, and power. These are the restrictions I am thinking to impose on the micropropulsion system ONLY: 0.7 Kg as the maximum total wet mass of the system, a 1U size for the micropropulsion system (100 mm X 100 mm X 100 mm) and 7 W as maximum power required to make the system work.

The CubeSat performance requirements set by ESA are as follows

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Now the question is what electric and chemical propulsion systems shall we choose to be combined. I propose

  1. Micro-resistojet (Electric propulsion). It vaporizes liquid water to a high temperature vapor for expulsion via a conventionally shaped nozzle, and has a wide potential for in-orbit maneuvers of nano-satellites. The general structure of the thruster is based on a modular design with three main parts: inlet section, heating chamber and nozzle. Biggest advantage: high Isp. Biggest drawback: low thrust.

enter image description here

  1. Bipropellant system (Chemical Propulsion). Combustion of an oxidizer (oxygen) and a fuel (hydrogen) are utilized to create a high-temperature, high-pressure gaseous mixture that can be expanded using a converging–diverging nozzle to create a high velocity exhaust stream. Bipropellant systems feature the highest performance for chemical systems per stored propellant, but require generally complex propellant managements system with multiple active components. Biggest advantage: higher thrust and performance among all chemical propulsion systems. Biggest disadvantage: complexity.

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Do you think it is feasible to combine those propulsion systems within CubeSat constrains?

Thank you in advance! ;)

  • $\begingroup$ About chemical propulsion cubesats with water electrolisys - yes, they are in development: nasa.gov/feature/ames/ptd-1 $\endgroup$
    – Heopps
    Sep 30, 2022 at 11:52
  • $\begingroup$ About thermal propulsion by electroheating - I see some problem here. It will be rather ineffective propulsion method, with very low delta V (velocity change) per propellant spent. Even nuclear thermal propulsion rocket is (theoretically) effective only when it uses pure hydrogen as propellant, not water - and with heating to much higher temperatures compared to electroheaters. I'm interested, what a cubesat with two different propulsion systems can do, but can't with single electrolisys-based system? $\endgroup$
    – Heopps
    Sep 30, 2022 at 13:00
  • $\begingroup$ The max requirement for thrust is one millinewton. That really minimizes the thrust advantage of the biprop system. $\endgroup$
    – Erin Anne
    Sep 30, 2022 at 20:32
  • $\begingroup$ or wait wait wait. you're asking if a resistojet and biprop rocket can be combined? I don't understand how you're proposing to do that in the first place. You want to resistively heat the combustion byproducts from a biprop rocket? $\endgroup$
    – Erin Anne
    Sep 30, 2022 at 20:36


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