Lunar Gravity Research Articles

Combined effects of heavy ion exposure and simulated Lunar gravity on skeletal muscle

BackgroundThe limitations to prolonged spaceflight include unloading-induced atrophy of the musculoskeletal system which may be enhanced by exposure to the space radiation environment. Previous results have concluded that partial gravity, comparable to the Lunar surface, may have detrimental effects on skeletal muscle. However, little is known if these outcomes are exacerbated by exposure to low-dose rate, high-energy radiation common to the space environment. Therefore, the present study sought to determine the impact of highly charge, high-energy (HZE) radiation on skeletal muscle when combined with partial weightbearing to simulate Lunar gravity. We hypothesized that partial unloading would compromise skeletal muscle and these effects would be exacerbated by radiation exposure. MethodsFor month old female BALB/cByJ mice were -assigned to one of 2 groups; either full weight bearing (Cage Controls, CC) or partial weight bearing equal to 1/6th bodyweight (G/6). Both groups were then divided to receive either a single whole body absorbed dose of 0.5 Gy of 300 MeV 28Si ions (RAD) or a sham treatment (SHAM). Radiation exposure experiments were performed at the NASA Space Radiation Laboratory (NSRL) located at Brookhaven National Laboratory on Day 0, followed by 21 d of CC or G/6 loading. Muscles of the hind limb were used to measure protein synthesis and other histological measures. ResultsTwenty-one days of Lunar gravity (G/6) resulted in lower soleus, plantaris, and gastrocnemius muscle mass. Radiation exposure did not further impact muscle mass. 28Si exposure in normal ambulatory animals (RAD+CC) did not impact gastrocnemius muscle mass when compared to SHAM+CC (p>0.05), but did affect the soleus, where mass was higher following radiation compared to SHAM (p<0.05). Mixed gastrocnemius muscle protein synthesis was lower in both unloading groups. Fiber type composition transitioned towards a faster isoform with partial unloading and was not further impacted by radiation. The combined effects of partial loading and radiation partially mitigated fiber cross-sectional area when compared to partial loading alone. Radiation and G/6 reduced the total number of myonuclei per fiber while leading to elevated BrdU content of skeletal muscle. Similarly, unloading and radiation resulted in higher collagen content of muscle when compared to controls, but the effects of combined exposure were not additive. ConclusionsThe results of this study confirm that partial weightbearing causes muscle atrophy, in part due to reductions of muscle protein synthesis in the soleus and gastrocnemius as well as reduced peripheral nuclei per fiber. Additionally, we present novel data illustrating 28Si exposure reduced nuclei in muscle fibers despite higher satellite cell fusion, but did not exacerbate muscle atrophy, CSA changes, or collagen content. In conclusion, both partial loading and HZE radiation can negatively impact muscle morphology.

Impact of reduced weight on motor and cognitive function in astronaut analogs: A simulated lunar gravity workload study

The purpose of this study was to investigate changes in gait patterns, motor dexterity, cognition, neuromuscular performance, neural activation of the prefrontal cortex, and perception of effort and exertion during a 60-min walking trial at a reduced body weight using a positive pressure treadmill (PPT). Eleven screened astronaut analog participants performed 60-min PPT sessions at either 100% (PPT100) or 20% body weight (PPT20) which were separated into six 10-min segments. During each segment, a 1-min gait analysis, Pegboard Task, Assembly Task, and Memory Recall Task were performed. Step frequency, rating of perceived physical and cognitive exertion, electromyographic amplitude and frequency from the vastus lateralis, metabolic markers, and functional near-infrared spectroscopy (fNIRS) of the prefrontal cortex were obtained for all segments during each condition. The primary findings of the study indicated that PPT20 was able to induce differences in step frequency relative to PPT100 and that PPT100 resulted in greater metabolic expenditures and electromyographic amplitude compared to PPT20. The PPT20, however, exhibited increased fNIRS prefrontal cortex activity during the Assembly Task and Memory Recall compared to the PPT100. In addition, the PPT20 resulted in an increase in Memory Recall errors compared to PPT100. In conclusion, the findings of the present study indicated that altered gait patterns associated with reduced weight does not impact basic motor dexterity tasks, such as gait and Pegboard Tasks, but does increase the difficulty of Assembly Tasks and Memory Recall in astronaut analogs. Thus, novel gait patterns can impact the cognitive loads that astronaut analogs can perform. Special considerations should be given to the impact that gravity-induced changes in gait patterns have on motor and cognitive tasks in future planetary exploration missions.

An approach to simulating Lunar crewed vehicle motions on Earth using a scaled prototype with active compensation

A Lunar crewed vehicle (LCV) is an indispensable detection tool that can not only transport astronauts a long distance from the Lunar module but also ensure their safety when moving around the Lunar surface. Accurate ground simulation of LCVs on Earth is crucial for vehicle testing and astronaut training prior to launch deployment. This study proposes a novel methodology to simulate the dynamic behavior of an LCV on the Lunar surface, that combines dimensional analysis with vehicle active suspension compensation to simulate an LCV experiment without an external compensator. Using dimensional analysis, vehicle parameters can be scaled based on ground experiment requirements and astronaut sensory consistency constraints. A scaled vehicle compensation model was developed that considers variation in the gravity field, and active suspensions were regulated to compensate for gravitational effects using an optimal force distribution strategy. Finally, dynamic simulations were conducted to verify the proposed method, and the results revealed that the prototype vehicle under Earth gravity could effectively approximate the same body dynamic response of a crewed Lunar rover in the Lunar gravity environment.

Basic study for lunar regolith powder bed fusion in high gravity

In-situ resource utilization has become a significant issue in recent space projects. For example, various studies have focused on lunar manufacturing using regoliths available on the moon's surface. Although regolith manufacturing will be conducted under lunar gravity, most studies have not considered the adverse effects of low gravity on additive manufacturing processes. This study evaluates the gravitational effect on lunar regolith powder bed fusion (PBF) by applying centrifugal acceleration to the PBF process. The experimental results show that gravitational acceleration influences the density, hardness, and transparency of the fabricated regolith blocks.

Size and density of lunar core estimated using simulated annealing algorithm

This study focuses on the size of composition of lunar core. In this study, we consider the lunar mean density and mean moment of inertia factor in our inversion. We use the degree-2 coefficients of lunar gravity field model GL990D and the lunar physical liberation parameters to compute mean moment of inertia factor, which is treated as an observed value. We also compute the observed value of the mean density according to the total mass of the Moon. Based on the interior structure with various layers, we deduce the modeled expressions for the lunar mean density and mean moment of inertia factor. Summing the squares of the difference between the observed value and modeled value as an inversion criterion, we estimate the multi-parameters based on the simulated annealing algorithm. By considering the lunar interior structure with three layers, the estimated size of the lunar core is around 470 km, and the density of the core is close to 5486 kg·m&lt;sup&gt;–3&lt;/sup&gt;. The computed size and density of the lunar core are close to other reported values, thereby validating our algorithm. We then consider the scenarios that the lunar core differentiates between a solid inner core and a liquid outer core. The good-inversed outer core is close to 385 km, while the inner core approaches to 350 km. By using the good-inversed sizes as fixed parameters, it is found that the inner core reaches 7879 kg⋅m&lt;sup&gt;–&lt;/sup&gt;³, quite denser than the outer core, which is estimated at 4618 kg⋅m&lt;sup&gt;–&lt;/sup&gt;³. Our result indicates that the outer core is composed of ferrous sulfide (FeS), while the inner core is comprised of ferrous or ferro-nickel, formed 3.56 billion years ago when the lunar core dynamo ended.

ОЦЕНКА ФУНКЦИОНАЛЬНЫХ ВОЗМОЖНОСТЕЙ ЭКИПАЖА ПРИ ВЫПОЛНЕНИИ ВНЕКОРАБЕЛЬНОЙ ДЕЯТЕЛЬНОСТИ ПОСЛЕ ДЛИТЕЛЬНОЙ ИЗОЛЯЦИИ В НАЗЕМНОЙ МОДЕЛИ КОСМИЧЕСКОЙ СТАНЦИИ

During interplanetary expeditions, the crew must adapt not only to gravity transitions but also to long-term stay in a limited space of a space station. In such conditions, it develops a significant decrease in motor activity and the formation of a special stereotype of movements in these conditions. Within further planning of ground-based and real interplanetary missions, it is appropriate to assess the impact of these factors on the crew's functional condition, including when modeling lunar gravity using suspension and virtual reality (VR) technologies. The purpose was to determine the functional capabilities of 5 members of the international crew of the 240-day SIRIUS-21 isolation experiment when performing an extravehicular activity (EVA) after 4 and 6 months of isolation in the hermetic facility. During EVA, the crew performed basic motor tasks using VR on an uneven surface: positional tests, voluntary and tandem walking, walking when avoiding and stepping over obstacles, and verticalization from lying and standing on one knee positions. In addition, the EVA scenario included the tasks of controlling the rover while the hands unloading, as well as moving on a sliding surface in a VR environment when the body lunar vertical unloading. In this study, we presented results of qualitative and quantitative analysis of video recording data and qualitative analysis of the electromyographic activity of the muscles of the lower extremities. The results indicate a sufficient level of functional performance of SIRIUS-21 crew members – all the EVA tasks were completed by the crew in full, while no cases of significant loss of balance and signs of pronounced locomotor and vestibular disorders were registered. At the same time, this paper highlights some features of the crew's EVA performance – the effects of sensorimotor training on some tasks with repeated EVA experience, the most common errors, and difficulties in performing the tasks of the EVA scenario.

The effect of three body positions on colour preference: An exploration of microgravity and lunar gravity simulations

Understanding the colour preference in microgravity environments will enable better design of future spacecraft and extra-terrestrial environments. In this study, a space station's crew cabin was simulated and evaluated in 33 different colours by 55 participants using a standard body position change methodology in controlled conditions. Three body positions were tested, and included normal sitting position (SP), to reflect terrestrial conditions; −15° head-down (HD) bed rest, to simulate a microgravity state; and 9.6° head-up tilt (HU) bed rest, to simulate a lunar gravity state. VR devices were worn by participants to ensure an immersive environment in which to evaluate the different coloured environments across the three different body positions. The results show that in all colour environments, there was no significant difference in the colour preference between SP and HU, but there was a significant change in the colour preference in HD compared to SP and HU. In the three positions, the participants appeared to prefer lighter colours rather than darker ones, warmer colours in ST and HU, and cool colours in HD. In this short-term simulation study, no evidence of gender differences in colour preference by body position was found, but in each body position, men and women had different preference levels for basic hue and chroma brightness.

Gravity Field of Ganymede After the Juno Extended Mission

AbstractThe Juno Extended Mission presented the first opportunity to acquire gravity measurements of Ganymede since the end of the Galileo mission. These new Juno data offered the chance to carry out a joint analysis with the Galileo data set, improving our knowledge of Ganymede's gravity field and shedding new light upon its interior structure. Through reconstruction of Juno's and Galileo's orbit during the Ganymede flybys, the gravity field of the moon was estimated. The results indicate that Ganymede's degree‐2 field is compatible with a body in hydrostatic equilibrium within 1−𝜎 and hint at regional gravity anomalies with amplitudes exceeding those inferred by Cassini for Titan. Our explicit treatment of non‐hydrostatic effects leads to wider confidence intervals for the derived moment of inertia with respect previous analyses. The higher central value of the derived moment of inertia indicates a lesser degree of Ganymede's differentiation.

Landing control method of a lightweight four-legged landing and walking robot

The prober with an immovable lander and a movable rover is commonly used to explore the Moon’s surface. The rover can complete the detection on relatively flat terrain of the lunar surface well, but its detection efficiency on deep craters and mountains is relatively low due to the difficulties of reaching such places. A lightweight four-legged landing and walking robot called “FLLWR” is designed in this study. It can take off and land repeatedly between any two sites wherever on deep craters, mountains or other challenging landforms that are difficult to reach by direct ground movement. The robot integrates the functions of a lander and a rover, including folding, deploying, repetitive landing, and walking. A landing control method via compliance control is proposed to solve the critical problem of impact energy dissipation to realize buffer landing. Repetitive landing experiments on a five-degree-of-freedom lunar gravity testing platform are performed. Under the landing conditions with a vertical velocity of 2.1 m/s and a loading weight of 140 kg, the torque safety margin is 10.3% and 16.7%, and the height safety margin is 36.4% and 50.1% for the cases with or without an additional horizontal disturbance velocity of 0.4 m/s, respectively. The study provides a novel insight into the next-generation lunar exploration equipment.

Augmented Reality Based on Apollo Lunar Imagery: Searching for Stars and Adding Virtual Objects

Abstract Based on photogrammetric models of the first three Apollo landing sites, we have created a method to project virtual objects onto photos taken on the lunar surface. We have applied this method to search for stars in high-resolution scans of Apollo lunar photos and to restore views of the starry sky in some iconic images. Our method can be used to incorporate computer-generated 3D graphics, such as constellation boundaries, and coordinate and contour lines, into lunar images. This research has several applications, including the visualization of digital terrain models, the creation of a virtual planetarium based on lunar photos, and demonstration of object motion in lunar gravity for educational purposes.

Estimating optimum launch velocity of electrostatically detached dust particles over sunlit locations on Moon

ABSTRACT Microscopic fluctuations over sunlit locations on Moon due to dominant photoelectric charging might induce a sufficient fluctuating electric field that can electrostatically detach the overlying charged dust by overcoming surface adhesion and lunar gravity. A formulation based on the dynamical evolution of the statistical variables, viz., the mean charge and the variance, at microscopic scale is established to calculate the local charge and electric field fluctuations and illustrate this effect. The formulation has been coupled with the charged particle dynamics to derive the optimum launch velocity of the dust particles near the surface just after detachment. Fowler's treatment of the photoemission, dominant Extreme Ultraviolet Lyman α radiation of the solar spectrum and subsequent collection of the emitted photoelectrons, measured particle size distribution of the regolith sample, and typical solar wind plasma have been consistently accounted for illustrating the concept. Our analysis suggests that the intense fluctuations in the electric field locally detach the submicron-charged particles with a launch velocity of a few ms−1–for instance, the charge fluctuations might induce ∼ 10 Mv m−1 field that can launch 100 nm particles with a speed of ∼5 m s−1.

Fitting a triaxial ellipsoid to a set of quasi-selenoidal points

Abstract The aim of this work is the determination of the parameters of the triaxial ellipsoid of the Moon, as derived from a quasi-selenoid model. After a detailed description of various quasi-selenoid models of the lunar gravity field, which were proposed in the last twenty years, we prepare suitable data sets of three-dimensional Cartesian coordinates. The mathematical model adopted is the general (polynomial) equation of an ellipsoid functionally related to the nine unknowns: the coordinates of the ellipsoid center, the three rotation angles and the three ellipsoid semiaxes. Furthermore, we adopt mathematical models for one special and two degenerate cases of the triaxial ellipsoid. We implement the least-squares method of indirect observations and we derive results for eighteen data sets of quasi-selenoidal points. From the results, we report the values of the semiaxes of the triaxial ellipsoid of fitting with three unknowns, for the model GL0660B, to be 1,738,256.3 ± 0.2 m, 1,738,023.1 ± 0.2 m and 1,737,603.2 ± 0.2 m, while the other unknowns remain insignificant. This triaxial ellipsoid leads to the improvement in the RMS value of the height anomaly at about 12 per cent in comparison to the oblate spheroid.

Short-term virtual reality simulation of the effects of space station colour and microgravity and lunar gravity on cognitive task performance and emotion

This study implemented a short-term virtual reality examination of the impacts of environmental colour and posture changes (to simulate microgravity and lunar gravity) on cognitive task performance and emotions. In a standard posture change laboratory study, sixty participants performed a simple cognitive task battery (finding A's test and number comparison test) and an emotional state questionnaire within nine different colour scenes while using three postures (normal sitting (SP), −12° head-down bed (HD) and 9.6° head-up tilt bed (HU)). The results showed that in all colour scenes, the HD posture significantly reduced the participants' task performance and level of positive emotions. There was also some variability in task performance and emotional reaction by scene colour. Overall, the study adds to our understanding of how environmental and postural factors impact on cognition and emotion.

Ejecta Pattern of Oblique Impacts on the Moon From Numerical Simulations

AbstractThe commonly adopted ejecta deposit models always assume vertical impacts for simplification. However, most impacts on planetary surfaces are oblique, which produce significantly different ejecta patterns from vertical impacts. Although the asymmetric ejecta patterns from oblique impacts have been studied in laboratory experiments, they cannot be directly applied to large craters on the planetary scale. Here, we use the three‐dimensional shock physics code iSALE‐3D to systematically simulate impact excavation processes under Moon's gravity with varied impact angles (10°–90° with respect to the horizontal), impactor diameters (1–120 km), and impact velocities (10–20 km/s), which produce craters or basins ranging from ∼5 to ∼1,000 km. For each model, we record ejecta launch velocities and angles and calculate their integrated patterns after ballistic sedimentation. Our model results show that as the impact angle departs from the vertical, launch velocities of the uprange ejecta decrease, forming a V‐shaped zone devoid of ejecta. For even lower impact angles, the downrange ejecta thickness significantly decreases due to reduced launch angles and smaller deposit distances, forming a butterfly pattern with most ejecta concentrating in crossrange. In addition, our model results indicate that large impactors tend to produce more asymmetric ejecta patterns and the ejecta patterns are insensitive to typical impact velocities on the Moon. Our modeling results provide a semi‐quantitative relation between the ejecta pattern and impact parameters for oblique impacts on the Moon, which can be used to constrain the possible impact parameters for lunar crater or basins according to the observed ejecta pattern.

Autonomous navigation for lunar final approach based on gravity gradient measurements

Lunar final approach navigation is critical for pin-point lunar landing in future missions. This study investigates the use of lunar gravity gradient measurements for autonomous navigation of a lunar probe during the final approach phase. As the spacecraft approaches the Moon, the strength of gravity gradient signals improves. A spaceborne gravity gradiometer can precisely measure local gravity gradients, and the latest lunar gravity model GL1500E is used to provide reference values. The employed truncation degree and order of the gravity model are increased stepwise considering the decreasing altitude of the spacecraft in order to reach a compromise between computational costs and model accuracy. An iterative Kalman filter is developed for coupled orbit and attitude estimation using gravity gradient measurements and attitude quaternions obtained from star sensors. A simulated spacecraft with a gradiometer noise level of 0.01 E is considered. Simulation results show that the spacecraft’s position converges rapidly and achieves an accuracy of less than 100 m at the last epoch.

Lunar Electromagnetic Mass Accelerator (LEMMA): An Initial Concept Assessment

National Aeronautics and Space Administration (NASA) plans to return to the Moon in 2025–2028 under the Artemis program, followed by establishment of a permanent lunar base by 2028–2032. This will be followed by future manned missions to Mars and exploration of the solar system. To support those objectives, the Gateway space station will be placed in a Near-Rectilinear Halo Orbit (NRHO) orbiting between the L2 Lagrange libration point beyond the Moon and the lunar south pole. The Gateway will be the intermediate supply station for future missions. Because of low lunar gravity, it should be much less expensive to supply lunar-derived water, fuel, and materials from the Moon to the Gateway than from the Earth. The lunar escape velocity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 2400$ </tex-math></inline-formula> m/s) is within the range achieved by the recent U.S. Navy railgun program. An initial evaluation of a lunar-based electromagnetic launcher (EML) railgun capable of delivering lunar-derived liquid hydrogen or lunar ice to the Gateway for fuel for a nuclear-reactor-powered Mars mission is provided here.

A review of different mascon approaches for regional gravity field modelling since 1968

Abstract. The geodetic and geophysical literature shows an abundance of mascon approaches for modelling the gravity field of the Moon or Earth on global or regional scales. This article illustrates the differences and similarities between the methods, which are labelled as mascon approaches by their authors. Point mass mascons and planar disc mascons were developed for modelling the lunar gravity field from Doppler tracking data. These early models had to consider restrictions in observation geometry, computational resources or geographical pre-knowledge, which influenced the implementation. Mascon approaches were later adapted and applied for the analysis of GRACE observations of the Earth's gravity field, with the most recent methods based on the simple layer potential. Differences among the methods relate to the geometry of the mascon patches and to the implementation of the gradient and potential for field analysis and synthesis. Most mascon approaches provide a direct link between observation and mascon parameters – usually the surface density or the mass of an element – while some methods serve as a post-processing tool of spherical harmonic solutions. This article provides a historical overview of the different mascon approaches and sketches their properties from a theoretical perspective.

Strategies to Develop Resilience: Lessons from a Civil Rights Activist, a Scientist, and an Astronaut.

Strategies to Develop Resilience: Lessons from a Civil Rights Activist, a Scientist, and an Astronaut.

Simulated Micro-, Lunar, and Martian Gravities on Earth-Effects on Escherichia coli Growth, Phenotype, and Sensitivity to Antibiotics.

Bacterial behavior has been studied under microgravity conditions, but very little is known about it under lunar and Martian gravitational regimes. An Earth-based approach was designed and implemented using inclined clinostats and an in-house-developed code to determine the optimal clinorotation angular speed for bacterial liquid cultures of 5 RPM. With this setup, growth dynamics, phenotypic changes, and sensitivity to antibiotics (minimum inhibitory concentration (MIC) of two different classes of antibiotics) for three Escherichia coli strains (including uropathogenic) were examined under simulated micro-, lunar, and Martian gravities. The results included increased growth under simulated micro- and lunar gravities for some strains, and higher concentrations of antibiotics needed under simulated lunar gravity with respect to simulated micro- and Martian gravities. Clinostat-produced results can be considered suggestive but not determinative of what might be expected in altered gravity, as there is still a need to systematically verify these simulation devices’ ability to accurately replicate phenomena observed in space. Nevertheless, this approach serves as a baseline to start interrogating key cellular and molecular aspects relevant to microbial processes on the lunar and Martian surfaces.

The Contribution of Small Impact Craters to Lunar Polar Wander

Changes in mass distribution affect the gravitational figure and reorient a planetary body’s surface with respect to its rotational axis. The mass anomalies in the present-day lunar gravity field can reveal how the figure and pole position have evolved over the Moon’s history. By examining sequentially each individual crater and basin, working backward in time order through the catalog of nearly 5200 craters and basins between 1200 and 20 km in diameter, we investigate their contribution to the lunar gravitational figure and reconstruct the evolution of the pole position by extracting their gravitational signatures from the present-day Moon. We find that craters and basins in this diameter range, which excludes South Pole–Aitken, have contributed to nearly 25% of the present-day power from the Moon’s degree-2 gravitational figure and resulted in a total displacement of the Moon’s pole by ∼10° along the Earth–Moon tidal axis over the past ∼4.25 billion years. This also implies that the geographical location of the Moon’s rotational pole has not moved since ∼3.8 Ga by more than ∼2° in latitude owing to impacts, and this has implications for the long-term stability of volatiles in the polar regions.