Browse Topic: Gravity
NASA's 4th New Frontiers Mission is the Titan Dragonfly relocatable lander. This coaxial quadrotor vehicle will be launched on a rocket to Titan in 2028. Following a gravity assisted Earth flyby and an approximate 6-year transit, Dragonfly will enter the Titan atmosphere around 2034 with the goal of exploring Titan's pre-biotic chemistry and habitability. The multirotor design for this unique application has continually evolved since 2016 with constraints such as Titan's cryogenic atmosphere at 95 Kelvin (-288 F), gravity 14% that of Earth's, atmospheric density 440% of standard sea-level air, and the inability to test the entire system together under all these conditions until the first flight on Titan. This paper focuses on rotor design aspects of the Dragonfly lander and introduces a novel framework for multirotor design optimization considering multiple flight conditions. The methodology leverages machine learning methods and is demonstrated in the context of Dragonfly. A new OVERFLOW Machine Learning Airfoil Performance (PALMO) database is first presented. PALMO is then wrapped inside a Bayesian optimization framework and applied to a 4-rotor system (one side of the Dragonfly lander). Training data is generated on each iteration of the optimization using the CAMRAD-II comprehensive analysis software to evaluate successive rotor designs in multiple relevant flight conditions. An optimal design for the 4-rotor system was found with approximately 900 rotor designs analyzed in CAMRAD-II, which required 9 million queries of the PALMO surrogate models. This demonstration case evaluated 10,000,000 potential candidate rotor designs in 5.5 hours on 114 CPU cores using uniform inflow, and in 27.8 hours using the prescribed wake model. This work thus enables mid-fidelity rotor design optimization without requiring access to high-performance computing.
Dragonfly is an X-8 octocopter designed to explore Saturn's moon Titan, and is currently under development for launch in 2026. Titan is a uniquely favorable body for atmospheric flight, in that it has a low gravity (1/7 Earth's) and a dense atmosphere (4x Earth's) which reduce the energetic requirements for heavier-than-air flight. Dragonfly will make multiple (autonomous) flights over several years with ranges of the order of 10km to explore different sites on Titan. The key features of the Titan environment are reviewed. These include the characteristics of the landing site terrain, resembling dune fields in terrestrial deserts. Winds are generally very low, ∼ 1m/s. Stronger winds, and methane rainfall, can occur in rare rainstorms, but these are not expected at the latitude and season of Dragonfly's arrival. Brownout and triboelectric charging due to surface dust lofted by rotor downwash is possible, and these hazards and their mitigations are discussed.
Abstract Transient numerical simulations are conducted over a NACA 0012 airfoil with triangular protrusions at a Reynolds number (Re) of 100000 using the γ-Reθ transition Shear Stress Transport (SST) turbulence model. Protrusions of heights 0.5%c, 1%c, and 2%c are placed at one of the three locations, viz, the leading edge (LE), 5%c on the suction surface, and 5%c on the pressure surface, while the angle of attack (AOA) is varied between 0° and 20°. Results obtained from the time-averaged solution of the unsteady Navier-Stokes equation indicate that the smaller protrusion placed at 5%c on the suction surface improves the post-stall lift coefficient by up to 59%, without altering the pre-stall characteristics. The improvement in time-averaged lift coefficients comes with enhanced flow unsteadiness due to vigorous vortex shedding. For a given protrusion height, the vortex shedding frequency decreases as the AOA is increased, while the amplitude of fluctuations in lift coefficient increases as the protrusion height is increased or as the AOA is increased. Nevertheless, mitigation of static stall phenomena is observed for most configurations investigated, and this finding can be beneficial for the design of Unmanned Aerial Vehicles (UAVs) and Micro Aerial Vehicles (MAVs). The enhancement in the vortex shedding frequencies due to triangular protrusion can be utilized for Vortex-Induced Vibrations (VIVs)-based energy generators.
Large amounts of existing space debris pose a threat to satellites, space vehicles, and astronauts aboard those vehicles. However, cleaning up the debris is problematic. For example, suction cups don't work in a vacuum, and traditional sticky substances like tape are largely useless because the chemicals they rely on can't withstand extreme temperature swings.
Preliminary data was recently provided for a reaction sphere prototype on NASA’s zero-gravity parabolic flight vehicle. Gyroscope telemetry indicates that reaction spheres were successfully commanded at 10- to 20-ms pulses during a handful of parabolas in each flight. This is the first publicly disclosed validation of a freely rotating reaction sphere in a standalone compact package. At dimensions of
NASA has long recognized the difficulty in providing emergency medical care to astronauts in space. Many aspects of space travel make medical care inherently difficult, and sufficient storage space for medical equipment severely limits the ability to carry a full complement of diagnostic and therapeutic equipment onboard. The Microgravity Compatible Medical Suction Device (MCMSD) enables aspiration and containment of bodily fluids and vomitus, while preventing the transmission of infectious agents.
In order to detect and quantify bone-specific alkaline phosphatase (BAP) in a human biological sample, a binding agent (molecule) that specifically recognizes BAP in a sample is typically required. This binding agent can then be used in numerous assays/instruments to enable the detection and quantification of BAP.
A stay on the International Space Station is no vacation. During a visit to the orbiting National Laboratory, astronauts divide their time among a variety of tasks. For one, they look after a multitude of space-based science experiments. For another, they clean and check the station’s equipment—inside and out. They also spend a significant amount of time doing something you might not expect: exercising.
Objects that orbit the Earth, such as the International Space Station (ISS), provide a unique environment called zero-g, or more correctly, microgravity. All objects in orbit are pulled by Earth’s gravity, but they achieve the lack of gravity when they move at just the right speed (in the case of the ISS, around 17,500 miles per hour) so that the curve of their fall matches the curve of the Earth. The result is a perpetual freefall, creating weightlessness.
Future manned spacecraft and lunar or Mars outposts will need a condensing heat exchanger (CHX) to control humidity in the cabin atmosphere. Condensing surfaces must be hydrophilic to control condensate flow and ensure efficient operation in zero gravity, and biocidal to prevent growth of microbes and formation of biofilms on condensing surfaces. Coatings must be extremely stable, adhere to the condensing surface, and maintain hydro philic and biocidal properties for many years.
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