Marsbees - Power Efficient Bioinspired Mars Explorers
Marsbees are dynamically scaled bioinspired Martian robotic flight vehicles. Marsbees are power efficient explorers with flexible flapping wings, which benefit from the dynamically scaled up animal flight mechanisms. Migrating flying animals showcase astonishing long-range flights, disproportionate to their sizes (Monarch butterflies: 4000 km; wandering albatross: 120000 km). While the aerodynamic mechanism behind these long-range flights is currently unknown, recent studies have shown that the use of lightweight flexible wings leads to energy efficient flapping wing motions.
The mission of the Marsbee is to employ a Marsbee multi-agent system to construct a 3D topographic map by integrating depth measurements captured by Marsbees to improve the effectiveness of Mars rovers. These flying scouts would provide a “third-dimension” to the rover capabilities. In other scenarios, each part of the swarm of Marsbees could carry pressure and temperature sensors for atmospheric sampling, or small spectral analyzers for identification of mineral outcroppings. In each scenario, the rover acts as a recharging and deployment/return station and data and communication hub.
Marsbees can fly in the Martian atmosphere using bioinspired flight mechanisms that insects and birds use.
Human exploration of Mars is one of the major objectives of NASA and commercial entities such as SpaceX and Boeing. The identified innovations unique to the bioinspired flapping Marsbee provide viable multi-mode flying mobility for Martian atmospheric and terrain exploration. A swarm of Marsbees provides an enhanced reconfigurable Mars exploration system that is resilient to individual component failures. These Marsbees can carry sensors and wireless communication devices in combination with a Mars rover and helicopters. These enhanced sensing and information gathering abilities can contribute to the following NASA Mars mission objectives: i) “Determine the habitability of an environment”, ii) “Obtain surface weather measurements to validate global atmospheric models”, and iii) “Prepare for human exploration on Mars”. Various commercial entities, e.g. SpaceX and Boeing, are investing in technologies to transport humans to Mars.
Background - Mars exploration
The red planet Mars has inspired us for centuries. The similarity and proximity to the Earth pose scientific questions that can lead to valuable understanding and discoveries about the Earth and the solar system in general. Since the Mars 1M No.1 mission in 1960, numerous successful and unsuccessful Mars missions involving orbiters, landers, and rovers have provided us critical information about Mars. The overarching goal is the human exploration of Mars.
One of the main challenges in Mars exploration is flying near the surface of Mars. Although the gravitational acceleration on Mars is 38% of Earth’s 9.8 m/s2, the Martian atmospheric density is only 1.3% of the air density on Earth. As aerodynamic forces are proportional to the ambient fluid density, it is difficult to generate sufficient lift to offset the vehicle.
One solution is flying at a higher speed with larger wings. For example, the Mars helicopter Ingenuity has demonstrated a successful take-off in April of 2021 by rotating its rotors at the top speed of 2,700 rotations per minute, which is more than five times of the typical rotational speed for helicopters on Earth. However, this method on Mars requires substantially more power than on Earth, leading to a short flight time of 3 min and a range of 300 m. NASA remains very interested in aerial exploration as evidenced by its Rotorcraft Optimization for the Advancement of Mars eXploration (ROAMX) program to further refine the rotorcraft technology to increase payload capacity, speed, and range.
Prior and current Mars flight vehicle concepts
Several intriguing aerial vehicle concepts have been proposed to overcome the challenges associated with flying on Mars. Liu et al. (Liu et al. 2013) provide a comprehensive review of these proposed designs. The Aerial Regional-scale Environmental Surveyor (ARES) was a rocket-powered, robotic airplane platform to aid the NASA Mars Exploration Program (Braun et al. 2006). The prototype was designed to fly at Martian altitudes between 1 and 2 km. However, the ARES could not land on Mars’ surface, and the concept was abandoned in favor of an orbiting surveyor. To explicitly tackle the issue of the low-density atmosphere, freely falling concepts and Mars balloons have also been proposed (Liu et al. 2013). Additionally, NASA’s Jet Propulsion Laboratory has considered a Mars Helicopter (Balaram et al. 2018b; Grip et al. 2018; Liu et al. 2013).
Bioinspired Mars flight vehicle concept
The proposed Marsbee project focuses on an alternative, bioinspired solution of flapping flights, which is particularly energy-efficient in low-density atmosphere. Migrating flying animals showcase astonishing long-range flights, disproportionate to their sizes. For example, Monarch butterflies (wingspan: 10 cm) fly 4000 km from North American to central Mexico, which has been reported to fly through thin air as high as 11,000 feet (Drake et al. 1988). The wandering albatross (wingspan: 3.1 m) can circumnavigate Antarctica 2-3 times, covering 120000 km (Weimerskirch et al., 2015). While the aerodynamic mechanism behind these long-range flights is currently unknown, recent studies have shown that the use of lightweight flexible wings leads to energy efficient flapping wing motions (Shyy et al. 2013). Also, the compliant nature of the flexible wings is surmised to aid soaring and gliding in the unsteady atmosphere.
To illustrate the power saving concept for flexible wings, we conducted a numerical parametric study (Pohly et al, 2021). For a rigid wing structure, the predicted flight time is 16 min with commercially available battery technology (Panasonic battery NCR18650B with a specific energy of 243Wh/kg). For a bioinspired flexible wing design with both the flapping and pitching inertial powers reduced, the Marsbee flight time substantially increases in the Martian environment.
Marsbees are able to save power by passively deforming and rotating the wings, resulting in a long flight time. The near surface Mars flight capabilities provide more detailed information (on the order of mm/pixel) on the localized surroundings of the rover including “over the hill” awareness. These altitude-advantaged capabilities improve the rover’s efficiency and effectiveness, increasing exploration autonomy while decreasing risk to the rover, thereby increasing the overall scientific return.
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