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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

enter image description here

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.

enter image description here

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

Thank you in advance! ;)

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  • $\begingroup$ About chemical propulsion cubesats with water electrolisys - yes, they are in development: nasa.gov/feature/ames/ptd-1 $\endgroup$
    – Heopps
    Sep 30 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 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 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 at 20:36

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