Overview Of Rotor Hover Performance Capabilities At Low Reynolds Number For Mars Exploration

Abstract

The Evolutionary aLgorithm for Iterative Studies of Aeromechanics (ELISA) software was developed in support of the Rotorcraft Optimization for the Advancement of Mars eXploration (ROAMX) project. ELISA was developed to enable aerodynamic rotor hover optimization for low Reynolds number flows in the Mars atmosphere. ELISA comprises two modules. The first module is dedicated to airfoil optimization and allows for the creation of multi-objective Pareto-optimal (PO) airfoil sets with the airfoil performance evaluation performed using the CFD code OVERFLOW. The second module is dedicated to rotor hover performance optimization and generates multi-objective PO rotor sets with the rotor performance evaluation performed using the comprehensive analysis code CAMRAD II. This paper presents recent updates to the ELISA optimization toolset. The airfoil module now includes variation in section Reynolds number, alongside simultaneous maximization of section lift and minimization of section drag. Consequently, the rotor optimization module can query PO airfoil sets (as a function of section lift, drag, and Reynolds number) and generate PO C81 airfoil decks tailored to specific Reynolds numbers; this eliminates the need for adequate initial chord guesses and allows for arbitrary rotor solidities to be studied. Furthermore, the rotor optimization procedure has been extended to incorporate a third dimension, alongside maximization of blade loading and minimization of rotor power. This enables optimization across a relevant density range on Mars, resulting in the lowest power rotor hover geometry (for each attainable blade loading and each density). The goal of this work is to present the relevance of recent updates to the ELISA optimization toolset, by demonstrating full rotor hover optimization using unconventional airfoils across a practical Mars density range, and by presenting various optimum solutions involving variable number of blades along with unconstrained solidity in the Mars atmosphere.