Evaluation of the Thorax of Manduca Sexta for Flapping-Wing Micro Air Vehicle Applications

The tobacco hornworm hawkmoth (Manduca sexta) provides an excellent model from which to garner knowledge pertaining to the development of a Flapping Wing Micro Air Vehicle (FWMAV). Insect-sized FWMAVs will be used by the future warfighter for reconnaissance, nuclear/chemical/biological hazard sensing, and targeting. One of the major challenges facing FWMAV developers is the energetically demanding nature of low Reynolds flapping flight. Investigating the Manduca sexta thorax/wing flapping mechanism as a mechanical system will provide insight into its inherent efficiency. This thesis examined the energetics of the thorax under static loading and dynamic loading using an innovative load-application technique. It was discovered that the thorax resists compression by a spring constant k=0.62 N/mm under the action of the dorsoventral flight muscles (DVMs). Constant stiffness measurement (CSM) nanoindentation of a major component of the thoracic exoskeleton, the tergum, revealed an elastic modulus of 5 GPa. This value is a benchmark for engineers seeking energy-storing materials for a FWMAV fuselage. Finally, a truly groundbreaking device was developed and used to directly measure the power requirement of the DVMs at Manduca sexta\u27s natural flapping frequency (25 Hz). This effort yielded a mechanical power output of 72-143 W*kg-1 for the DVMs. The feasibility of the author\u27s approach was confirmed by the agreement of this conclusion with published results. The power output requirement confirms the need for lightweight and energy-dense power sources for the fruition of fully-capable FWMAVs

Methods Used to Evaluate the Hawkmoth (Manduca Sexta) as a Flapping-Wing Micro Air Vehicle

Examining a biological flapping-flight mechanism as a mechanical system provides valuable insight related to the development and construction of Flapping-Wing Micro Air Vehicles (FWMAVs). Insects provide excellent candidates for this reverse-engineering, and one species in particular, the hawkmoth Manduca sexta, stands out as an exceptional model. Engineers with FWMAV aspirations can benefit greatly from knowledge of M.sexta\u27s advanced yet deceptively simple flight mechanism. Avenues for investigating this mechanism include finite element modeling, nanoindentation for material properties, and mechanical power output calculations or measurement. This paper presents these concepts and reviews existing literature to provide a platform for ongoing FWMAV research and design

Exploratory Structural Investigation of a Hawkmoth-Inspired MAV’s Thorax

Manduca Sexta present excellent flight performances which make this insect an ideal candidate for bio-inspired engineered micro air vehicles. The actual insect presents an energetically very efficient thorax-wing flight system which needs to be fully understood for an effective design of artificial flying machines. This work discusses a preliminary finite element model which simulates the thorax-wing system and the muscles involved in the flapping motion. Both upstroke and downstroke conditions are statically analyzed with the application of load sets that simulate the contractions of the dorso-ventral and dorso-longitudinal muscles (indirect flight). Comparison with commercial software and experimental results is also presented and discussed

Trait Rumination Predicts Elevated Evening Cortisol in Sexual and Gender Minority Young Adults

Stress may contribute to illness through the impaired recovery or sustained activity of stress-responsive biological systems. Rumination, or mental rehearsal of past stressors, may alter the body’s stress-responsive systems by amplifying and prolonging exposure to physiological mediators, such as cortisol. The primary aim of the current investigation was to test the extent to which the tendency to ruminate on stress predicts diminished diurnal cortisol recovery (i.e., elevated evening cortisol) in a sample of sexual and gender minority young adults. Participants included 58 lesbian, gay, bisexual, and transgender young adults (Mage = 25.0, SD = 4.1) who completed an initial online survey that assessed trait rumination and current depressed mood. Participants completed daily evening questionnaires and provided salivary cortisol samples at wake, 45 min post-wake, 12 h post-wake, and at bedtime over seven consecutive days. Trait rumination predicted significantly higher cortisol concentrations at bedtime, but was unrelated to other cortisol indices (e.g., morning cortisol, diurnal slope, total output). The association with trait rumination was not accounted for by daily negative affect, and was largely independent of depressed mood. These results have implications for identifying and treating those who may be at risk for impaired diurnal cortisol recovery and associated negative health outcomes