Gastrocnemius medialis contractile behavior during running differs between simulated Lunar and Martian gravities

The international partnership of space agencies has agreed to proceed forward to the Moon sustainably. Activities on the Lunar surface (0.16 g) will allow crewmembers to advance the exploration skills needed when expanding human presence to Mars (0.38 g). Whilst data from actual hypogravity activities are limited to the Apollo missions, simulation studies have indicated that ground reaction forces, mechanical work, muscle activation, and joint angles decrease with declining gravity level. However, these alterations in locomotion biomechanics do not necessarily scale to the gravity level, the reduction in gastrocnemius medialis activation even appears to level off around 0.2 g, while muscle activation pattern remains similar. Thus, it is difficult to predict whether gastrocnemius medialis contractile behavior during running on Moon will basically be the same as on Mars. Therefore, this study investigated lower limb joint kinematics and gastrocnemius medialis behavior during running at 1 g, simulated Martian gravity, and simulated Lunar gravity on the vertical treadmill facility. The results indicate that hypogravity-induced alterations in joint kinematics and contractile behavior still persist between simulated running on the Moon and Mars. This contrasts with the concept of a ceiling effect and should be carefully considered when evaluating exercise prescriptions and the transferability of locomotion practiced in Lunar gravity to Martian gravity.

Properties of the lunar gravity assisted transfers from LEO to the retrograde-GEO

The retrograde geostationary earth orbit (retro-GEO) is an Earth’s orbit. It has almost the same orbital altitude with that of a GEO, but an inclination of 180°. A retro-GEO monitor-satellite gives the GEO-assets vicinity space-debris warnings per 12 h. For various reasons, the westward launch direction is not compatible or economical. Thereby the transfer from a low earth orbit (LEO) to the retro-GEO via once lunar swing-by is a priority. The monitor-satellite departures from LEO and inserts into the retro-GEO both using only one tangential maneuver, in this paper, its transfer’s property is investigated. The existence of this transfer is verified firstly in the planar circular restricted three-body problem (CR3BP) model based on the Poincaré-section methodology. Then, the two-impulse values and the perilune altitudes are computed with different transfer durations in the planar CR3BP. Their dispersions are compared with different Sun azimuths in the planar bi-circular restricted four-body problem (BR4BP) model. Besides, the transfer’s inclination changeable capacity via lunar swing-by and the Sun-perturbed inclination changeable capacity are investigated. The results show that the two-impulse fuel-optimal transfer has the duration of 1.76 TU (i.e., 7.65 days) with the minimum values of 4.251 km s−1 in planar CR3BP, this value has a range of 4.249–4.252 km s−1 due to different Sun azimuths in planar BR4BP. Its perilune altitude changes from 552.6 to 621.9 km. In the spatial CR3BP, if the transfer duration is more than or equal to 4.00 TU (i.e., 17.59 days), the lunar gravity assisted transfer could insert the retro-GEO with any inclination. In the spatial BR4BP, the Sun’s perturbation does not affect this conclusion in most cases.

Geostationary Orbit Transfer with Lunar Gravity Assist from Non-equatorial Launch Site

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.

Lunar surface soft-landing analysis of a novel six-legged mobile lander with repetitive landing capacity

The autonomous robots consisting of an immovable lander and a rover are widely deployed to explore extraterrestrial planets. Two main drawbacks limit the development of this cooperative work mode: (1) it cannot perform soft-landing missions repeatedly on the planet, owing to the damage of buffer structure during soft-landing. (2) the rover’s detection area is restricted to the vicinity of the immovable lander. To overcome these problems, we have designed an innovative six-legged mobile lander with repetitive landing capacity, called “HexaMRL”, which integrates the functions of a lander and a rover including folding, deploying, repetitive landing, and walking. This novel robot’s legs adopted hybrid mechanism with active and passive compliance. Therefore, it remains to be a great challenge to analyze the robot soft-landing capacity which is determined by the parameters such as spring stiffness coefficient, damper damping coefficient, and initial tiptoe position. In order to solve the problem, the dynamic modeling and assessment criteria were established. The soft-landing process was analyzed through three numerical simulations using three sets of representative parameters based on dynamic model and the set of best effective parameters was chosen to apply in soft-landing experiment on a 5-DOF lunar gravity testing platform (5-DOF LGTP). The experiments were further verified that the selected parameters met the requirement of soft landing on the lunar surface. The HexaMRL provides novel insight for the next generation equipment for lunar exploration, which may be an efficient solution to the extraterrestrial planet exploration.

Additive Manufacturing Under Lunar Gravity and Microgravity

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.

Cardiopulmonary Resuscitation in Hypogravity Simulation

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.