Will the Mars Helicopter Induce Local Martian Atmospheric Breakdown?

Abstract

Any rotorcraft on Mars will fly in a low-pressure and dusty environment. It is well known that helicopters on Earth become highly charged due, in part, to triboelectric effects when flying in sandy conditions. We consider the possibility that the Mars Helicopter Scout (MHS), called Ingenuity, flying at Mars as part of the Mars 2020 Perseverance mission, will also become charged due to grain-rotor triboelectric interactions. Given the low Martian atmospheric pressure of ∼5 Torr, the tribocharge on the blade could become intense enough to stimulate gas breakdown near the surface of the rotorcraft. We modeled the grain–blade interaction as a line of current that forms along the blade edge in the region where grain–blade contacts are the greatest. This current then spreads throughout the connected quasi-conductive regions of the rotorcraft. Charge builds up on the craft, and the dissipative pathway to remove charge is back into the atmosphere. We find that for blade tribocharging currents that form in an ambient atmospheric dust load, system current balance and charge dissipation can be accomplished via the nominal atmospheric conductive currents. However, at takeoff and landing, the rotorcraft could be in a rotor-created particulate cloud, leading to local atmospheric electrical breakdown near the rotorcraft. We especially note that the atmospheric currents in the breakdown are not large enough to create any hazard to Ingenuity itself, but Ingenuity operations can be considered a unique experiment that provides a test of the electrical properties of the Martian near-surface atmosphere.

Lifting of Tribocharged Grains by Martian Winds

“…Our experiments may provide a basis to estimate electric charges on Martian sands, e.g., in terrains where electrostatics may be a problem for landers on Mars (Farrell et al 2021). Furthermore, these insights will be useful to improve models of sand transport on the Martian surface and to predict wind conditions necessary for aeolian geomorphodynamics on Mars (Parteli & Herrmann 2007;Pähtz et al 2014;Lämmel et al 2018).…”

A Generalized Townsend's Theory for Paschen Curves in Planar, Cylindrical, and Spherical Geometries in Planetary Atmospheres

“…Recently, Farrell et al. (2021) have suggested that the rotors of the Ingenuity helicopter could cause localized breakdown during takeoff or landing. While Ingenuity does not have the instrumentation to make such measurements electronically, videography in low‐light conditions could reveal such processes.…”

“…We conclude this paper by highlighting several current and upcoming missions that may provide exciting insights into electrical processes on Mars and Titan. Recently, Farrell et al (2021) have suggested that the rotors of the Ingenuity helicopter could cause localized breakdown during takeoff or landing. While Ingenuity does not have the instrumentation to make such measurements electronically, videography in low-light conditions could reveal such processes.…”

Lifting and Transport of Martian Dust by the Ingenuity Helicopter Rotor Downwash as Observed by High‐Speed Imaging From the Perseverance Rover

“…Beyond the importance of dust lifting in general on Mars, the specific problem of dust mobilization by rotor downwash is of interest in aviation—in terrestrial helicopter operations, the effect is termed “brownout” (analogous to “whiteout” in snow). In addition to possible degradation of optical sensor performance, lofted dust might cause triboelectric charging (e.g., Farrel et al., 2021 ; Lorenz, 2020 ). With helicopters now being considered for sample return operations at Mars, and the development of the Dragonfly rotorcraft for Titan underway, the possibility of extraterrestrial brownout means in situ measurements at Mars have considerable value in testing the generality of brownout models (e.g., Rabinovitch et al., 2021 ) under physical conditions quite different from Earth.…”