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The present study investigates capture and escape dynamics associated with a planar, high–energy, retrograde periodic orbit around the Earth for applications to spacecraft trajectories. A lunar gravity assist plays the central role in both capture and escape scenarios. In the capture analysis, the trade–off among time–of–flights, launch energies, and insertion delta–v are revealed. A variety of solutions exists including fast, multi–revolutional, and Sun–perturbed transfers. The escape analysis, on the other hand, focuses on transfers with short time–of–flights. The search finds that a double lunar gravity assist, occurring after a departure delta–v on the periodic orbit, enables efficient escape from the Earth with substantial hyperbolic excess velocities. The overall result leads to a concept “Comet Interception from eArth retrOgrade orbIT viA Lunar gravIty Assist” using the retrograde periodic orbit as a staging post and enabling fast lunar encounters to travel toward the interplanetary region.

We show that it is possible to launch a satellite to Geostationary Equatorial orbit (GEO) from the non-equatorial launch site (Naro Space Center in South Korea) even though that is located in the mid-latitudes of the northern hemisphere. When launched from this site, the equatorial inclination after separation will be 80°. We use a lunar gravity assist (LGA) transfer to avoid the excessive ∆V costs of plane change maneuvers. There are eight possible paths for the LGA; there are four paths consisting of Earth departures and free-return types, and there are two nodes of the Moon’s orbit (ascending and descending). We analyze trajectories over five launch periods for each path using a high-fidelity orbit propagation model. We show that the LGA changes the orbital energy of the “cislunar” free-returns more than for the “circumlunar” free-returns, resulting in less geostationary insertion ∆V for the cislunar free-returns. We also show that the geometrical ∆V variation over the different paths is greater than the seasonal ∆V variation. Our results indicate that an ascending departure and cislunar free-return at the descending node have lower ∆V requirements than the other paths, and lower than described in several previous studies.

BACKGROUND: Limited research exists into extraterrestrial CPR, despite the drive for interplanetary travel. This study investigated whether the terrestrial CPR method can provide quality external chest compressions (ECCs) in line with the 2015 UK resuscitation guidelines during ground-based hypogravity simulation. It also explored whether gender, weight, and fatigue influence CPR quality.METHODS: There were 21 subjects who performed continuous ECCs for 5 min during ground-based hypogravity simulations of Mars (0.38 G) and the Moon (0.16 G), with Earths gravity (1 G) as the control. Subjects were unloaded using a body suspension device (BSD). ECC depth and rate, heart rate (HR), ventilation (VE), oxygen uptake (Vo2), and Borg scores were measured.RESULTS: ECC depth was lower in 0.38 G (42.9 9 mm) and 0.16 G (40.8 9 mm) compared to 1 G and did not meet current resuscitation guidelines. ECC rate was adequate in all gravity conditions. There were no differences in ECC depth and rate when comparing gender or weight. ECC depth trend showed a decrease by min 5 in 0.38 G and by min 2 in 0.16 G. Increases in HR, VE, and Vo2 were observed from CPR min 1 to min 5.DISCUSSION: The terrestrial method of CPR provides a consistent ECC rate but does not provide adequate ECC depths in simulated hypogravities. The results suggest that a mixed-gender space crew of varying bodyweights may not influence ECC quality. Extraterrestrial-specific CPR guidelines are warranted. With a move to increasing ECC rate, permitting lower ECC depths and substituting rescuers after 1 min in lunar gravity and 4 min in Martian gravity is recommended.Sriharan S, Kay G, Lee JCY, Pollock RD, Russomano T. Cardiopulmonary resuscitation in hypogravity simulation. Aerosp Med Hum Perform. 2021; 92(2):106112.

Lunar gravity assist is a means to boost the energy and C3 of an escape trajectory. Trajectories with two lunar gravity assists are considered and analyzed. Two approaches are applied and tested for the design of missions aimed at Near-Earth asteroids. In the first method, indirect optimization of the heliocentric leg is combined to an approximate analytical treatment of the geocentric phase for short escape trajectories. In the second method, the results of pre-computed maps of escape C3 are employed for the design of longer Sun-perturbed escape sequences combined with direct optimization of the heliocentric leg. Features are compared and suggestions about a combined use of the approaches are presented. The techniques are efficiently applied to the design of a mission to a near-Earth asteroid.

Owing to different gravities, the same manned lunar rover shows different acceleration properties on the earth and the moon; therefore, it is of great significance for astronauts to be trained on the earth under the condition of the acceleration properties found on the moon. In this article, a novel acceleration imitation method focused on a single wheel is proposed to obtain equivalent acceleration when using the same acceleration driver input under different gravities, and the acceleration imitation algorithm is derived based on a mechanical model of a special metal wheel with a mesh surface. To reduce the complexity and improve the real-time properties of the algorithm, a fitting function for the imitation torque ratio is proposed to adjust the relationship between the acceleration driver input and the driving torque of the wheel. Finally, experiments were conducted to verify the acceleration imitation algorithm, and the results revealed that the wheel with an imitation torque ratio could effectively approximate on the earth the same acceleration experienced by a single wheel of a manned lunar rover on the moon, given equivalent acceleration driver inputs.

Spectrum-Roentgen-Gamma is an international X-ray astrophysical space observatory, planned to be launched in 2019. The spacecraft will operate in the vicinity of the Lagrangian point L 2 of the Sun-Earth system. The nominal lifetime of the mission is 7 years, and it includes all-sky survey and pointed observations in the 0.1–15 keV band. The paper describes technical constraints of the mission, covering launch scenario, spacecraft structure and ground data relay network, and a design of suitable operational orbits. In addition, opportunities to achieve a suitable operational orbit are discussed, including a scenario with a lunar gravity assist and a transfer with an intermediate orbit.

The gravity assist is a maneuver greatly applied to space missions, with the main goal of giving or removing energy of a spacecraft through a passage near a celestial body. The patched-conics approximation is the first approximation that is usually considered in the mission planning. It gives a good accuracy in the majority of the situations. However, when using the Moon for the close approach, the results have a tendency to diverge from a more complete three body dynamics. This is due to the large mass of the Moon compared to the Earth. In that sense, the goal of the present paper is to study the errors given by the patched-conics approximation in a lunar gravity assist maneuver. To find those errors we compare the results coming from this approximation with the equivalent results obtained from the circular restricted three body problem and the bi-circular restricted four body problem for a same periselenium condition. This comparison is made in the orbital elements before the maneuver and the C 3 of the spacecraft after the maneuver under the three models considered. Different values for the initial conditions of the spacecraft are used to obtain general conclusions about the behavior of the errors involved. We conclude that there is a tendency to a better agreement between the patched-conics and the three body problem for retrograde transfer orbits. We also find that the effects of the Sun in the maneuver needs to be included only in more accurate steps of the mission.

The short- and long-term postural effects on the forced expiratory tracheal noise time were studied in a sample of 12 subjects. In contrast to the spirometric parameters, the tracheal forced expiratory noise time does not respond to a short-term change in the body posture from sitting and standing positions to the lying position, as well as to 14-day-long orthostatic hypokinesia in a lying position with a body angle of +9.6°. However, significant multidirectional individual dynamics of the tracheal forced expiratory noise time was observed in all subjects during long-term orthostatic hypokinesia, whereas the spirometric parameters had a dominant growth response. It is assumed that the estimation of the forced expiratory tracheal noise time during long-term orthostatic hypokinesia in lunar gravity simulation may provide useful data in addition to spirometry when assessing the individual lung function dynamics. The dynamics of acoustic parameters, as well as spirometric parameters, during long-term postural effects can be considered as adaptive changes.

This paper shows the performance of various traction control strategies that aim to minimize slippage and wheel fighting by properly adjusting the velocity of each traction wheel in a planetary rover. These strategies are validated through simulations performed in ANVEL (Quantum Signal LLC) and using two rovers currently employed by NASA. These experiments use similar features to those that a planetary rover would face on the Moon such as terrain geomorphology and lunar gravity. After running those experiments, the following conclusions were drawn: (1) when no traction control is considered, results show the rover gets entrapped or makes a shorter progress than when traction control is applied; (2) the proposed traction controllers demonstrate a proper balance between slip-compensation (lowest mean slip) and reduction of wheel fighting effects (less aggressive control actions); (3) after considering two different planetary rovers, it is observed that the mechanical configuration effects slip reduction. These contributions can also be observed in the accompanying videos.

The twin satellite mission Gravity Recovery and Interior Laboratory (GRAIL) aims to recover the lunar gravity field by means of Ka-band ranging observations. In order to exploit the potential of the inter-satellite range variations, absolute position information of the two probes is required. Hitherto, the Graz lunar gravity field models (GrazLGM) relied on the official science orbit products provided by NASA. In this contribution, we present for the first time a completely independent Graz Lunar Gravity Model based on Primary Mission data. The models are resolved up to spherical harmonic degree and order 420. The orbits of the two probes are determined using variational equations following a batch least squares differential adjustment process implemented in the in-house developed software package ORCA (Orbit Re-Construction Application). These orbits are based on S-band radiometric tracking data collected by the Deep Space Network (DSN) and are used for the independent GRAIL gravity field recovery. To reveal a highly accurate lunar gravity field, an integral equation approach using short orbital arcs is adopted to process the Ka-band data, where no regularization or Kaula constraint is applied. The correlation of gravity with lunar topography as well as the Bouguer spectrum of our solutions is comparable to the models officially released by the GRAIL Science Team.

In the future, when humans build their bases on terrestrial planets and their moons, caves will be the safest place for inhabitation. Large holes, believed to be cave entrances, have been discovered on the Moon, along with small features called “impact melt pits.” In the Gravity Recovery and Interior Laboratory (GRAIL) gravity model, which is expressed in spherical harmonics (SH), it is difficult to express the gravity anomaly created by a small empty space below the surface. Nevertheless, we propose that a cave network, akin to an anthill, exists under the impact melt pits discovered on the Moon. This is because we think it is natural to apply a network created by Earth’s small caves to the Moon. We obtained accurate Bouguer gravity measurements by calculating regional crustal density using localized admittance of the study area and detected weak gravity (mass deficit) information. By increasing the degrees and order of SH at regular intervals, we estimated the change in gravity at a specific position at high degrees and order, thereby extracting shallow depth information. To validate our method, we compared our results with those of existing studies that analyzed the previously known Marius Hills Hole (MHH) area. The analysis of seven regions in our study area revealed a mass deficit in some impact melt pits in four lunar regions (Copernicus, King, Stevinus, and Tycho). We propose that there is a cave network in this region, indicated by the gravitation reduction in the impact melt pits region. Our results can be useful for the selection of landing sites for future in situ explorations of lunar caves.

Mankind is setting to colonize space, for which the manufacturing of habitats, tools, spare parts and other infrastructure is required. Commercial manufacturing processes are already well engineered under standard conditions on Earth, which means under Earth’s gravity and atmosphere. Based on the literature review, additive manufacturing under lunar and other space gravitational conditions have only been researched to a very limited extent. Especially, additive manufacturing offers many advantages, as it can produce complex structures while saving resources. The materials used do not have to be taken along on the mission, they can even be mined and processed on-site. The Einstein-Elevator offers a unique test environment for experiments under different gravitational conditions. Laser experiments on selectively melting regolith simulant are successfully conducted under lunar gravity and microgravity. The created samples are characterized in terms of their geometry, mass and porosity. These experiments are the first additive manufacturing tests under lunar gravity worldwide.

The work is devoted to evaluation of parameters of operator performance (OP) during controlling the lunar rover using the virtual reality (YR) technique “Lunar mission simulator”. Yirtual systems are a safe and controlled area for training and research of traumatic and dangerous situations. Physiological effects of lunar gravity were simulated by orthostatic hypokinesia (OH) with a body angle of+9.6 relative to the horizon. The influence of lunar gravity to certain extent affects cardiovascular and respiratory system that cannot help influencing on the operator’s work, especially during adaptation of a body to new conditions. There was analyzed the data from four healthy subjects who were in orthostatic hypokinesia for two weeks. Data of OP and cardiorespiratory reactions during OP was recorded at the stage before hypokinesia (baseline data) and on 13th day of OH in the study. It was established that the time indicators of OP such as reaction time on emergency situations and expended time of the task in tight time tended to worsening in simulated conditions. The results of the dynamics of cardio-respiratory system parameters reflect multidirectional changes when performing operator work: a decrease in blood pressure and respiratory rate, and an increase in heart rate.

The effects of long-term reduced (lunar) gravity are very much unknown. The Apollo Program represents our only experience with humans in extended lunar gravity. Those exposures were brief, but few if any major medical issues were encountered that cannot be ascribed to issues other than reduced gravity. Animal experiments will be of great value in elucidating partial-g effects, but they have uncertain transfer to human responses; the best of these experiments are being performed now (2021) with rodents on an ISS centrifuge. We might expect that some of the main physiological issues that occur in extended weightlessness (e.g., ISS) will manifest also in extended lunar gravity, but this is far from certain. The reduced but non-zero gravity level on the moon may well be sufficient to halt or dramatically reduce the main aspects of physiological deconditioning seen in weightlessness. Those aspects that are not sufficiently alleviated in this way might benefit from additional exercise and intermittent exposures to higher gravity levels.

Orbit determination of probes visiting Solar System bodies is currently the main source of our knowledge about their internal structure, inferred from the estimate of their gravity field and rotational state. Nongravitational forces acting on the spacecraft need to be accurately included in the dynamical modeling (either explicitly or in the form of empirical parameters) not to degrade the solution and its geophysical interpretation. In this study, we present our recovery of NASA GRAIL orbits and our lunar gravity field solutions up to degree and order 350. We propose a systematic approach to select an optimal parametrization with empirical accelerations and pseudo‐stochastic pulses, by checking their impact against orbit overlaps or, in the case of GRAIL, the very precise inter‐satellite link. We discuss how parametrization choices may differ depending on whether the goal is limited to orbit reconstruction or if it also includes the solution of gravity field coefficients. We validate our setup for planetary geodesy by iterating extended lunar gravity field solutions from pre‐GRAIL gravity fields, and we discuss the impact of empirical parametrization on the interpretation of gravity solutions and of their error bars.

We performed an innovative STEM outreach project. High school students from the Colombian robotics’ designed a prototype of a Lunar Loo named Tech Lunar Toilet (TLT) that was part of the international HeroX-NASA Challenge. These experiences were possible thanks to a wonderful network of collaboration. As a result of this program, the students that participated were able to cultivate their curiosity, strengthen their scientific skills and increase their interest in pursuing careers in STEM fields. Simultaneously, they were able to contrast visual and instrumental data obtained from the robotics and new technologies that can be performed in the microgravity environments for future space explorations. The efficient TLT suction system will guarantee proper operation in both microgravity and lunar gravity. Most of the structure can be built in a 3D printer using PLA as a raw material. This polymer made from renewable resources with mechanical properties comparable to the petroleum-based ones will allow reducing the weight of the structure. We recognized that our project-based education is a powerful engine for development. We share our methodology for the construction of our TLT that can be used in microgravity. We also show the progression and impact of this innovative project of scientific dissemination.

We obtain computational expressions for determining the generalized free fall acceleration at any point on the Earth surface depending on the terrestrial, solar, and lunar gravities, height above sea level, season, and diurnal time. The acceleration components due to the solar gravity and the Earth revolution around the Sun take sign-alternating values in the period of 24 hours. The greatest influence of the Sun on the free fall acceleration is in perihelion with the maximal diurnal amplitude of oscillations up to 55.34mGal, while the influence of the lunar gravity is negligible and takes sign-alternating values (up to 3–4mGal).We determine the maximum and minimum values of the acceleration on the Earth surface (983229.81 and 976073.25mGal) and also note the possibility of influence of accelerations due to centrifugal forces on the human organism.

In this paper, optimal two-impulse Earth-Moon transfers using the lunar gravity assist (LGA) are designed and investigated in the restricted four-body problem (RFBP) with the Sun, the Earth, and the Moon as primaries. Using the double LGA orbit as the initial guess, we propose an optimization method of the Earth-Moon transfer using the LGA in the RFBP. In our design process, the optimization problem in the RFBP is decomposed into several easier optimization subproblems in the easier models to reduce the difficulty of the optimization problem. Then, the optimal LGA transfers are displayed and analyzed. The results indicate that the LGA is an important technique in the Earth-Moon transfer design, which can efficiently save the fuel cost, but the LGA transfer duration must be larger than a period of the Earth-Moon system.

In this paper, transfers from the low Earth orbit (LEO) to libration point orbits using lunar gravity assist (LGA) are proposed and investigated in the Sun-Earth-Moon restricted four-body problem (RFBP). Using the patched LGA orbits as the initial guesses, we present a design method of LGA transfers to libration orbits in the RFBP. The design method is applicable to both prograde and retrograde lunar flyby. Based on the design method, 8 kinds of LGA transfers are obtained. Then, the performances of those LGA transfers, including fuel cost and duration time, are compared and discussed. The analysis results can guide us choose appropriate types of LGA transfers in libration point mission. Finally, LGA transfers are compared with direct transfers based on the Sun-Earth stable manifolds to display the effect of lunar flyby on the transfer.

NASA's GRAIL mission employed twin spacecraft in polar orbits around the Moon to measure the lunar gravity field at unprecedentedly high accuracy and resolution. The low spacecraft altitude in the extended mission enables the detection of small-scale surface or subsurface features. We analyzed these data for evidence of empty lava tubes beneath the lunar maria. We developed two methods, gradiometry and cross-correlation, to isolate the target signal of long, narrow, sinuous mass deficits from a host of other features present in the GRAIL data. Here, we report the discovery of several strong candidates that are either extensions of known lunar rilles, collocated with the recently discovered “skylight” caverns, or underlying otherwise unremarkable surfaces. Owing to the spacecraft polar orbits, our techniques are most sensitive to east-west trending near-surface structures and empty lava tubes with minimum widths of several kilometers, heights of hundreds of meters, and lengths of tens of kilometers.

This paper globally explores two-impulse, low-energy Earth–Moon transfers in the planar bicircular restricted four-body problem with transfer time of up to 200 days. A grid search combined with a direct transcription and multiple shooting technique reveals numerous families of optimal low-energy solutions, including some that have not been reported yet. We investigate characteristics of solutions in terms of parameters in two- and three-body dynamics, and discuss a trade-off between cost and transfer time based on Pareto-optimal solutions, with and without lunar gravity assists. Analysis of orbital characteristics reveals the role of the Sun, the Earth, and the Moon in the transfer dynamics.

The success of previous lunar science missions can be expanded upon by using a constellation of satellites to increase the lunar surface coverage. A constellation could also serve as a communications or GPS network for a lunar human base. Small-sats, deployed from a single mothercraft, are proposed to achieve a lunar constellation. The establishment of a single- and multi-petal constellation is investigated where the mothercraft does the primary deployment maneuvers. The constellation lifetime and closed-loop maintenance are addressed once higher order lunar gravity fields and Earth/solar perturbations are included.

In this paper, the lunar gravity assist (LGA) orbits starting from the Earth are investigated in the Sun–Earth–Moon–spacecraft restricted four-body problem (RFBP). First of all, the sphere of influence of the Earth–Moon system (SOIEM) is derived. Numerical calculation displays that inside the SOIEM, the effect of the Sun on the LGA orbits is quite small, but outside the SOIEM, the Sun perturbation can remarkably influence the trend of the LGA orbit. To analyze the effect of the Sun, the RFBP outside the SOIEM is approximately replaced by a planar circular restricted three-body problem, where, in the latter case, the Sun and the Earth–Moon barycenter act as primaries. The stable manifolds associated with the libration point orbit and their Poincare sections on the SOIEM are applied to investigating the LGA orbit. According to our research, the patched LGA orbits on the Poincare sections can efficiently distinguish the transit LGA orbits from the non-transit LGA orbits under the RFBP. The former orbits can pass through the region around libration point away from the SOIEM, but the latter orbits will bounce back to the SOIEM. Besides, the stable transit probability is defined and analyzed. According to the variant requirement of the space mission, the results obtained can help us select the LGA orbit and the launch window.

A novel method of ground simulation in humans of physiological effects induced by the stay on the surface of celestial bodies with hypogravity was developed and successfully tested. This method is based on the change of gravity force angle, which decreases the gravitational component of the blood hydrostatic pressure characteristic of human vertical posture on the Earth and the load-weight onto the locomotor apparatus to the lower values expected at celestial bodies with hypogravity. The methodological requirements for ground simulation of the physiological effects of lunar gravity on human body are specified and substantiated by theoretical calculations. The experimental study revealed redistribution of liquid media in the human organism, functional changes in the cardiorespiratory system, and a decrease in the load-weight applied to the locomotor apparatus.

In this paper a design method for changing the inclination of an orbital spacecraft from the ascending orbit to the retrograde orbit is presented. Firstly, revealing the mechanism of the lunar gravity assist, and maximum change capability of the spacecraft orbit parameters will be obtained, based on the Lagrangian planetary equation or Hamilton equation; Secondly, studying the flight mechanism to transfer the geocentric orbital spacecraft to the geocentric retrograde orbit; Finally, the orbit technology from the forward GEO orbit to the retrograde GEO orbit is designed, and the technical application method in the actual orbit design project is proposed.

The aviation and space industry is advancing at a fast pace. In light of the launch and reentry accidents that have happened in the past, it is essential to have accurate analysis of the parameters required for error-free launch and placement of the launched body in correct trajectory. In this paper, we discuss various orbital parameters required for placing a satellite, launched from earth, in correct orbit and the designing of its trajectory using patched conic approximation (PCA) method. Also presented are various perturbations factors like lunar gravity and atmospheric drag. The effect of these factors is considered and compared with the ideal cases.

A lunar roving vehicle (LRV) is an important and indispensable detection tool that can not only transport astronauts a long distance from the lunar module but also ensures their safety when moving around the lunar surface. Thus, it is very important to train astronauts to drive the LRV on Earth. However, astronauts will experience different properties and driving sensations for the same vehicle owing to the difference in the gravities of Earth and the Moon. Thus, it is hard to train them on Earth using a normal LRV. Therefore, an approach is used to produce a vehicle that has the same steering properties and driving sensations as the LRV on the lunar surface. This approach involves a control algorithm that is developed in this paper using the H ∞ control theory. The math calculation and visual simulation results show that a four-wheel steering imitating LRV, which uses an imitating control algorithm, with either a higher stiffness torsion bar spring or lower payload than the LRV has a high imitation accuracy for the yaw speed, slip angle, and lateral acceleration at the driver’s position. Finally, a highly accurate approach for imitating the steering of an LRV on the lunar surface has been realized, which lays the foundation for training astronauts to drive an LRV.

A monitoring of the gravity on the surface of the Moon was undertaken by a surveyor. A geodetic concept seems to be helpful at considering the internal structure of the Moon. The author introduces a model of the Moon which is consisted by a core covered by a spherical surface layer. Referring to the NASA data, the author noted about what is introduced the lunar gravity on the Moon surface to see what is suggested by the monitored lunar gravity field centering though the Moon is on the lunar orbital motion.

The European Space Agency has recently announced to progress from low Earth orbit missions on the International Space Station to other mission scenarios such as exploration of the Moon or Mars. Therefore, the Moon is considered to be the next likely target for European human space explorations utilising, the Lunar surface twofold: As an operational test bed for further planetary explorations and to conduct research in a unique setting with 1/6th of Earth’s gravity field. Compared to microgravity (µg), only very little is known about the physiological effects of exposure to partial gravity (µg < partial gravity < 1 g). However, previous research studies and experiences made during the Apollo missions comprise a valuable source of information that should be taken into account when planning human space explorations to reduced gravity environments. This systematic review summarizes the different effects of partial gravity (0.1-0.4 g) on the human musculoskeletal, cardiovascular and respiratory system using data collected during the Apollo missions as well as outcomes from terrestrial models of reduced gravity with either 1 g or microgravity as a control. The evidence-based findings seek to facilitate decision making concerning the best medical and exercise support to maintain astronauts’ health during future missions in partial gravity. The initial search generated 1323 publication hits. Out of these 1323 publications, 43 studies were included into the present analysis and relevant data were extracted. None of the 43 included studies investigated long-term effects. Studies investigating the immediate effects of partial gravity exposure reveal that cardiopulmonary parameters such as heart rate, oxygen consumption, metabolic rate and cost of transport are reduced compared to 1 g. Biomechanical studies reveal that ground reaction forces, mechanical work, stance phase duration, stride frequency, duty factor and preferred walk-to-run transition speed are reduced compared to 1 g. Partial gravity exposure below 0.4 g seems to be insufficient to maintain musculoskeletal and cardiopulmonary properties in the long-term. To compensate for the anticipated lack of mechanical and metabolic stimuli some form of exercise countermeasure appears to be necessary in order to maintain reasonable astronauts’ health, and thus ensure both sufficient work performance and mission

The lunar roving vehicle (LRV) is an important and indispensable detection tool that not only can travel far from the lunar module and transport, but also need ensure the astronauts safety when driving. Thus, the driving training for the astronauts on the earth is of great significance. However, the same vehicle has the different dynamic properties under the different gravities, and it is not able to train them with same vehicle on the earth. Therefore, a method of earth environment to imitate LRV steering on the lunar surface is required. In this study, to find out the relationship of the vehicles under different gravities, a handling dynamic model of the vehicles under different gravities is built, some parameter relation coefficients of vehicles under different gravities are carried out, and all parameters of the imitating vehicle for training and imitating on the earth are solved. Finally, the simulation results in Vortex show that, the imitating vehicle, which is changed parameters from LRV, can imitate a LRV steering under the lunar gravity on the earth.

Introduction Humans will eventually return to the Moon and thus there is a need for a ground-based analogue to enable the study of physiological adaptations to lunar gravity. An important unanswered question is whether or not living on the lunar surface will provide adequate loading of the musculoskeletal system to prevent or attenuate the bone loss that is seen in microgravity. Previous simulations have involved tilting subjects to an approximately 9.5 degrees angle to achieve a lunar gravity component parallel to the long-axis of the body. However, subjects in these earlier simulations were not weight-bearing, and thus these protocols did not provide an analogue for load on the musculoskeletal system. Methods We present a novel analogue which includes the capability to simulate standing and sitting in a lunar loading environment. A bed oriented at a 9.5 degrees angle was mounted on six linear bearings and was free to travel with one degree of freedom along rails. This allowed approximately 1/6 body weight loading of the feet during standing. "Lunar" sitting was also successfully simulated. Results A feasibility study demonstrated that the analogue was tolerated by subjects for 6 d of continuous bed rest and that the reaction forces at the feet during periods of standing were a reasonable simulation of lunar standing. During the 6 d, mean change in the volume of the quadriceps muscles was -1.6% +/- 1.7%. Discussion The proposed analogue would appear to be an acceptable simulation of lunar gravity and deserves further exploration in studies of longer duration.

When calculating the lunar digital elevation model by using LAM data of ChangE-1 lunar orbiter, the radical error of measurement in lunar mass center fixed coordinate is one kind of the key error sources. For LAM, two stages of oscillators, with one from satellite bus system and one from LAM itself, supplied time synchronization, timing and frequency standard of lunar altimetry. The independent unstable oscillations of them created the relevant errors to LAM. We analyzed the time slips and drifts in data time tags, estimated the possible systematic bias of reference frequency of LAM oscillator. Then we calibrated the effects of them on LAM data. The budgets of these three kinds of error sources are 0.7-1.2 m, ~10 m and ~145 m, respectively. Using the calibrated LAM data, a new 360 orders and degrees lunar topography model, CLTM-s03, has been obtained. By combining the new DEM model of the moon with CEGM02 lunar gravity model, a couple of middle scale type II lunar mascon basins, Fitzgerald-Jackson and Amundsen-Ganswindt, have been newly identified.

The moon has longstanding questions such as lunar environments, origin, formation and evolution, magnetization of crustal rocks, internal structure and possible life. The recent lunar missions, e.g., SELenological and ENgineering Explorer “KAGUYA” (SELENE), Chang’E-1, Chandrayaan-1, and Lunar Reconnaissance Orbiter/Lunar CRater Observation and Sensing Satellite (LRO/LCROSS), have provided new opportunities to explore and understand these issues. In this paper, we reviewed and presented the results and findings in the fields of lunar gravity, magnetic field, atmosphere, surface geomorphology and compositional variations, volcano, craters, internal structure, water and life science from new lunar exploration missions. In addition, the new objectives and scientific questions on lunar explorations in near future are presented and discussed.

To this point, we have discussed the current status and future prospects of energy from coal, oil, natural gas, nuclear, wind, solar, and hydro. With the exception of the contribution from nuclear, the ultimate origin of the energy for all of these sources is the sun— energy captured millions of years ago by photosynthesis in the case of the fossil fuels (coal, oil, and natural gas), energy harvested from contemporary inputs in the case of wind and solar. We turn now to a discussion of the potential for generation of electricity from geothermal sources and ocean tides. Decay of radioactive elements in the Earth’s interior provides the dominant source for the former; energy extracted from the gravitational interaction of the Earth and moon is the primary source for the latter. There are two main contributions to the energy reaching the surface from the Earth’s interior. The first involves convection and conduction of heat from the mantle and core. The second reflects the contribution from decay of radioactive elements in the crust, notably uranium, thorium, and potassium. The composite geothermal source, averaged over the Earth, amounts to about 8 × 10– 2 W m– 2, approximately 3,000 times less than the energy absorbed from the sun. As a consequence of the presence of the internal source, temperatures increase at an average rate of about 25°C per kilometer as a function of depth below the Earth’s surface. The rate of increase is greater in regions that are tectonically active, notably in the western United States and in the region surrounding the Pacific Ocean (the so- called Ring of Fire) — less in others. Of particular interest in terms of harvesting the internal energy source to produce electricity are hydrothermal reservoirs, subsurface environments characterized by the presence of significant quantities of high- temperature water formed by exposure to lava or through contact with unusually hot crustal material. The water contained in hydrothermal reservoirs is supplied for the most part by percolation from the surface through overlying porous rock. The conditions required for production of these hydrothermal systems are relatively specialized.

There is no information regarding the effects of simulated microgravity or lunar gravity on reserve possibilities of different inspiratory muscles. As a part of the multi-disciplinary “SELENA-T” Bed Rest Study, we investigated the pattern of inspiratory muscles fatigue in twenty-two healthy male subjects during incremental exercise test to exhaustion before and repeatedly after 21-days of hypokinesia by bed rest. Ten subjects underwent all 21 days of hypokinesia on head-down bed rest (HDBR) at a -6 degrees angle simulating microgravity. Twelve subjects spend the first five days of hypokinesia on HDBR and subsequent sixteen days - in head-up bed rest (HUBR) at a +9.6 degrees angle as a supposed analogue of lunar gravity. Maximal inspiratory pressure (MIP) and EMG-analyses of the diaphragm (D), parasternal (PS), sternocleidomastoid (SCM) and scalene (SC) muscles served as indices of inspiratory muscle function assessment. The before-to-after exercise decreases in MIP and centroid frequency (f c ) of the EMG (D, PS, SCM, and SC) power spectrum (P

INTRODUCTION: Missions of astronauts to Moon and Mars may be planned in the future. From over 40 years of manned spaceflight it is known that the human body experiences cardiovascular and musculoskeletal losses and a decrease in aerobic fitness while exposed to reduced gravity. Because future missions will be much longer than before, further research is needed to improve Earth-based simulations of reduced gravity. Among others, two methods are capable of simulating fractional gravity on Earth: supine Lower Body Negative Pressure (LBNP) and upright Lower Body Positive Pressure (LBPP). Up to now no direct comparison between supine LBNP and upright LBPP has been performed. To prepare future space exploration missions it is, however, important to determine the best method of simulating on Earth cardiovascular and biomechanical conditions for lunar (1/6 G) and Martian (3/8 G) gravities. For this purpose, exercise performed within a lower body negative pressure (LBNP) and a lower body positive pressure (LBPP) chamber was compared in this study. METHODS: Twelve subjects underwent a protocol of resting and walking (0.25 Froude) within supine LBNP and upright LBPP simulation. Each protocol was performed in simulated 1/6 G and 3/8 G. We assessed heart rate (HR), mean arterial blood pressure, oxygen consumption (V̇O2), normalized stride length, normalized vertical peak ground reaction force, duty factor, cadence, perceived exertion (Borg), and comfort of the subject. A mixed linear model was employed to determine effects of the simulation on the respective parameters. Furthermore, parameters were compared with predicted values for lunar and Martian gravities to determine the method that showed the best agreement. RESULTS: During walking, all cardiovascular and biomechanical parameters were unaffected by the simulation used for lunar and Martian gravities. During rest, HR and V̇O2 were lower in supine LBNP compared with upright LBPP. HR, V̇O2, and normalized vertical peak ground reaction force obtained with supine LBNP and upright LBPP during walking showed good agreement with predicted values. DISCUSSION: Since supine LBNP and upright LBPP are lacking significant differences, we conclude that both simulations are suited to simulate the cardiovascular and biomechanical conditions during activity in lunar and Martian gravities. Operational characteristics and the intended application should be considered when choosing either supine LBNP or upright LBPP to simulate partial gravities on Earth., EINFÜHRUNG: Erfahrungen aus 40 Jahren bemannter Raumfahrt zeigen, dass die Exposition des menschlichen Körpers gegenüber reduzierter Schwerkraft erhebliche Veränderungen des Herz-Kreislauf-Systems sowie des Bewegungsapparates bewirkt. Diese Veränderungen bedingen eine Reduktion seiner Leistungsfähigkeit. Es ist davon auszugehen, dass zukünftige Weltraum- Missionen zum Mond oder Mars denkbar länger sein werden als alle bisherigen. Um diese adäquat vorzubereiten, sind zusätzliche Forschungen notwendig, um erdbasierte Simulationen reduzierter Schwerkraft weiter zu verbessern. Derzeit existieren zwei Methoden für die Simulation reduzierter Schwerkraft auf der Erde: Die Applikation von Unterdruck auf den Unterkörper in horizontaler Position (Lower Body Negative Pressure, LBNP) und die Applikation von Überdruck auf den Unterkörper in vertikaler Position (Lower Body Positive Pressure, LBPP). Allerdings ist bisher kein direkter Vergleich zwischen horizontalem LBNP und vertikalem LBPP durchgeführt worden, um die beste Methode zur Simulation der Anpassungen des Herz-Kreislauf-Systems und Bewegungsapparates an Mond- (1/6 G) und Mars-Gravitation (3/8 G) auf der Erde zu bestimmen. Das Ziel der Studie war daher die Simulation dieser Anpassungen mittels beider Methoden (LBNP vs. LBPP) im Ruhen und Gehen jeweils miteinander zu vergleichen. METHODEN: Zwölf Probanden durchliefen ein Protokoll bestehend aus Ruhen und Gehen (0,25 Froude) unter Verwendung von jeweils horizontalem LBNP und vertikalem LBPP. Jedes Protokoll wurde in simulierter Mond- (1/6 G) und Mars-Gravitation (3/8 G) durchgeführt. Folgende Parameter wurden untersucht: Herzfrequenz (HF), mittlerer arterieller Blutdruck, Sauerstoffaufnahme (VO2), normierte Schrittlänge, normierte vertikale Spitzenbodenreaktionskraft, Tastverhältnis (Duty Factor), Schrittfrequenz, subjektive Beurteilung der Anstrengung (Borg) und des Komforts des Probanden. Ein gemischtes lineares Modell wurde verwendet, um Effekte der Simulation auf die jeweiligen Parameter zu bestimmen. Darüber hinaus wurden die erhobenen Parameter mit vorberechneten Werten für Mond- und Mars-Gravitation verglichen, um die Simulations-Methode mit der besten Übereinstimmung zu identifizieren. ERGEBNISSE: Während des Gehens waren alle Herz-Kreislauf- und biomechanischen Parameter unabhängig von der Simulations-Methode für 1/6-G und 3/8-G. Während der Ruhebedingungen hingegen waren HF und VO2 in horizontalem LBNP verglichen mit vertikalem LBPP niedriger. Darüber hinaus zeigten die mittels horizontalem LBNP und vertikalem LBPP simulierten Parameter (HF, VO2 und normierte vertikale Spitzenbodenreaktionskraft) eine gute Übereinstimmung mit den vorberechneten Werten für Mond- und Mars-Gravitation. DISKUSSION: Da zwischen horizontalem LBNP und vertikalem LBPP keine signifikanten Unterschiede aufgezeigt werden konnten, schlussfolgern wir, dass beide Simulations-Methoden geeignet sind, die Anpassungen des Herz-Kreislauf-Systems und Bewegungsapparates an Aktivitäten bei Mond- und Mars-Gravitation zu simulieren. Die vorgesehene Anwendung und deren Spezifika sollten bei der Auswahl der jeweiligen Methodik (horizontaler LBNP oder vertikaler LBPP) zur Simulation von Mond- und Mars-Gravitation auf der Erde Berücksichtigung finden.

We present a high-resolution lunar gravity field model (LGM2011) that provides gravity accelerations, free-air gravity anomalies, selenoid undulations and vertical deflections over the entire Moon’s surface. LGM2011 is based on the Japanese SELENE mission that provides the low- and medium-frequency constituents of the gravity field, down to spatial scales of ~78 km. At spatial scales between ~78 km and ~1.5 km, LGM2011 uses highfrequency topographic information derived from LOLA laser altimetry to approximate the gravity field signatures of many medium- and small-size impact craters for the first time. For the topography-based gravity approximation, we use Newtonian forward-modelling under the key assumptions that the SELENE and LOLA data are consistent, the high-frequency lunar topography is uncompensated and the topographic mass density is constant. The short-scale component of LGM2011 should not be relied upon in geophysical interpretations. LGM2011 can be used as an a priori model for lunar gravity field simulation and inversion studies, evaluation of past and future lunar gravity field missions, improved topographic mapping

著者人数: 12名, Accepted: 2011-11-18, 資料番号: SA1003651000

In this paper novel Earth–Mars transfers are presented. These transfers exploit the natural dynamics of n-body models as well as the high specific impulse typical of low-thrust systems. The Moon-perturbed version of the Sun–Earth problem is introduced to design ballistic escape orbits performing lunar gravity assists. The ballistic capture is designed in the Sun–Mars system where special attainable sets are defined and used to handle the low-thrust control. The complete trajectory is optimized in the full n-body problem which takes into account planets’ orbital inclinations and eccentricities. Accurate, efficient solutions with reasonable flight times are presented and compared with known results.

The SELENE mission, consisting of three separate satellites that use different terrestrial-based tracking systems, presents a unique opportunity to evaluate the contribution of these tracking systems to orbit determination precision. The tracking data consist of four-way Doppler between the main orbiter and one of the two sub-satellites while the former is over the far side, and of same-beam differential VLBI tracking between the two sub-satellites. Laser altimeter data are also used for orbit determination. The contribution to orbit precision of these different data types is investigated through orbit overlap analysis. It is shown that using four-way and VLBI data improves orbit consistency for all satellites involved by reducing peak values in orbit overlap differences that exist when only standard two-way Doppler and range data are used. Including laser altimeter data improves the orbit precision of the SELENE main satellite further, resulting in very smooth total orbit errors at an average level of 18 m. The multi-satellite data have also resulted in improved lunar gravity field models, which are assessed through orbit overlap analysis using Lunar Prospector tracking data. Improvements over a pre-SELENE model are shown to be mostly in the along-track and cross-track directions. Orbit overlap differences are at a level between 13 and 21 m with the SELENE models, depending on whether 1-day data overlaps or 1-day predictions are used.

The interpretation of planetary anomalies in the gravity fields of Mars and the Moon in relationship to their inhomogeneous internal structure is considered. The Martian and lunar gravity field models up to order and degree 20, three-layer (crust, mantle, core) model parameters, and planetary parameters have been used as input data. Models of the three-dimensional density distribution have been constructed for Mars and the Moon. The maps of horizontal density inhomogeneities at depths of 50, 100, and 1700 km for Mars and 60, 100, and 1400 km for the Moon are interpreted.

The hypothesis, proposed by the late Gunter Klein, that the autonomous nyctinastic movements of bean leaves are related to the tidal force exerted by the Moon was tested. Using data collected by Dr Klein, a close correspondence was found between the time at which leaves initiated a sudden downward turning movement and the time at which the tidal force changed from either a minimum (AƒÂ‚A‚‘low tideAƒÂ‚A‚Â’) or a maximum (AƒÂ‚A‚‘high tideAƒÂ‚A‚Â’). In many cases the data sets of leaf movements and the changing tidal force gave evidence of correlative patterns of behaviour. Evidence was also adduced for a minimal 6.2-h interval, or multiples thereof, between successively executed leaf movements. Data from an earlier study by A Kleinhoonte were also examined and have been found to show even closer correspondences than do KleinAƒÂ‚A‚Â’s data between bean leaf-movements and changing tidal forces. Thus, KleinAƒÂ‚A‚Â’s hypothesis of coherence between leaf and Moon is upheld.