I am doing research on propulsion systems and it was suggested that I use an ion propulsion system for a theoretical satellite I am tasked with designing, I need to maintain orbit for three years totaling 720m/s (+ 830m/s to get there) delta v to maintain the orbits, and using a 400kg satellite. One orbit is pretty circular with another being more elliptical, both around 5000km on the semi-major axis. I am trying to figure out how much thrust the propulsion system will need to be able to produce to maintain the orbital patterns I come up with. This is made a bit trickier by the lumpiness of the moon's gravitation field, but I also know very little about guidance and propulsion to come up with any good ideas. I haven't been able to find any lunar orbiting 400kg satellites that use ion propulsion systems, so I can't tell if it is just not feasible given the low thrust of the systems or how to even best approach this.
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1$\begingroup$ "720 total delta v" what units? "ESPA class satellites" What are those? Satellites can stay in lunar orbit for decades if they don't go too low, so without additional details about "the orbital patterns (you) come up with" the answer is certainly "Yes, and in some cases even without it". For example, Chandrayaan-1 was launched in 2008 and last detected in 2016 still in lunar orbit. See also. $\endgroup$– uhohFeb 17, 2022 at 5:15
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1$\begingroup$ Sorry, 720m/s (+ 830m/s to get there) delta v to maintain the orbits, and using a 400kg satellite. It was mentioned by a person I'm working with on this project that one orbit is pretty circular with another being more elliptical, both around 5000km on the semi-major axis $\endgroup$– SamFeb 17, 2022 at 5:29
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$\begingroup$ Okay great, can you go ahead and click "edit" and put that into your question? Thanks! $\endgroup$– uhohFeb 17, 2022 at 5:46
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2$\begingroup$ just for ref (as i think its been edited out), ESPA class of satellites <700kg: csaengineering.com/content/dam/moog/literature/Space_Defense/… $\endgroup$– blobbymcblobbyFeb 17, 2022 at 7:19
1 Answer
Assuming you just need the 720 m/s in electric propulsion for orbital maintenance (830 m/s insertion is done chemically?), I think it's possible.
A first order analysis gives a thrust requirement on the order of milli-Newtons:
$$accel_{avg} = \frac{\Delta V}{T}=\frac{F_T}{m} \to F_T = 400kg \cdot \frac{720 m/s}{3 yr} \to F_T = \sim 3mN$$
NASA's DART, though not a lunar mission, is a similar mass (610 kg) and uses electric propulsion (NEXT-C) so that may be a good starting point for ideas.
The NEXT-C from Aerojet Rocketdyne can amply produce this amount of thrust:
(Source: NEXT-C datasheet)
Even with more realistic duty cycles (10% -> ~30mN, 1% -> ~300mN) it is still possible with NEXT-C, though other options certainly exist.
All of the papers I am seeing on "low thrust orbital maintenance" seem to ignore or leave to the reader dealing with aspherical gravity, but they may be useful regardless:
- Gomes, Vivian & Prado, Antonio & Kuga, Helio. (2009). Orbital maneuvers Using Low Thrust. 12227-10. ResearchGate link
- Vivian M. Gomes, Antonio F. B. A. Prado, "Low-Thrust Out-of-Plane Orbital Station-Keeping Maneuvers for Satellites", Mathematical Problems in Engineering, vol. 2012, Article ID 532708, 14 pages, 2012. https://doi.org/10.1155/2012/532708
- Pollard, J.. (2000). Simplified Analysis of Low-Thrust Orbital Maneuvers. 42. Defense Technical Information Center (DTIC) link
- Aziz, J.D. (2018). Low-Thrust Many-Revolution Trajectory Optimization. PhD dissertation, Abstract link, Warning: Direct Download Link
The last paper is a dissertation so it is quite verbose, though that may be useful for building up an understanding.
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2$\begingroup$ Wow, that is so helpful. Thank you so much for all of that - pretty far in over my head with this class and project so this is huge! $\endgroup$– SamFeb 17, 2022 at 17:22
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1$\begingroup$ @Sam you may also find this interesting: Going from LEO to lunar using only low-thrust ion propulsion - can it be done? $\endgroup$– uhohFeb 17, 2022 at 20:15