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Weightlessness

Weightlessness, also known as microgravity, is the condition in which objects and people experience an apparent absence of weight due to continuous free fall, where gravitational forces are effectively canceled by orbital motion or equivalent acceleration, resulting in a sensation of floating despite the presence of gravity.^[1]^[2] This state occurs when an object, such as a spacecraft in low Earth orbit, falls toward Earth at the same rate as its surroundings, typically at speeds around 17,500 miles per hour (28,000 kilometers per hour), creating a balanced trajectory where no net force from gravity is felt relative to the environment.^[2] Although an object's mass remains unchanged, its apparent weight registers as zero on a scale, distinguishing weightlessness from true zero gravity, as Earth's gravitational pull is still, for example, about 90% as strong at typical low Earth orbit altitudes of 200–250 miles (320–400 kilometers).^[2]^[1] In space environments like the International Space Station, weightlessness enables unique scientific research by allowing phenomena such as fluid behavior, combustion, and material formation to be observed without the interference of Earth's full gravitational field.^[2] Physiologically, prolonged exposure leads to effects including muscle atrophy, bone density loss at rates up to 1% per month, and cardiovascular changes, necessitating countermeasures like exercise to mitigate deconditioning in astronauts.^[3] On Earth, brief periods of weightlessness can be simulated through parabolic aircraft flights, drop towers, or roller coasters, providing valuable testing grounds for space-related studies.^[1]

Definition and Fundamental Physics

Newtonian Perspective

In Newtonian mechanics, weight is defined as the normal force exerted by a surface on an object in contact with it, which counteracts the gravitational force to prevent free fall.^[4] This normal force is what we perceive as the sensation of weight in everyday situations, such as standing on the ground where the surface pushes upward with a force equal to mg, with m being the object's mass and g the local gravitational acceleration (approximately 9.8 m/s² on Earth's surface).^[5] Weightlessness arises when an object experiences no net contact forces, such as the normal force, and is solely under the influence of gravity, resulting in uniform acceleration at g. In this state of free fall, the object follows a parabolic trajectory dictated by gravity alone, with no additional forces altering its motion relative to the gravitational field.^[6] The apparent weight can be expressed by the equation W = mg - ma, where a is the acceleration of the reference frame containing the object; during free fall, a = g, yielding W = 0.^[7] This condition occurs not only in vertical drops but also in scenarios where the acceleration matches gravity's pull, leading to a lack of perceived weight. Isaac Newton's law of universal gravitation, formulated in 1687, provides the foundational framework for understanding weightlessness by describing gravity as a force proportional to the product of masses and inversely proportional to the square of the distance between them: F = G \frac{m_1 m_2}{r^2}, where G is the gravitational constant.^[8] This law elucidates orbital motion as a form of perpetual free fall, where satellites or planets continuously "fall" toward the central body but maintain a stable orbit due to their tangential velocity balancing the gravitational acceleration.^[9] Newton's insights, building on earlier work by Galileo on falling bodies, established that all objects accelerate uniformly under gravity regardless of mass, enabling the conceptual link between simple free fall and complex orbital paths.^[10] It is important to distinguish weightlessness from zero gravity: gravity is never truly absent in these scenarios, as the gravitational force persists, but its effects on perceived weight are nullified by the matching acceleration of the free-falling frame.^[11] In Newtonian terms, this equivalence highlights that weightlessness is a consequence of inertial motion under gravity, not the elimination of the gravitational field itself.^[9]

Equivalence Principle and Free Fall

The equivalence principle, formulated by Albert Einstein, posits that the inertial mass and gravitational mass of any object are identical, ensuring that all bodies accelerate identically under gravity regardless of their composition or mass.^[12] This equivalence implies that, in a local region, the physical effects of a uniform gravitational field are indistinguishable from those experienced in an accelerated reference frame, such as a rocket accelerating upward at the same rate as the gravitational acceleration.^[13] Consequently, weightlessness arises in free fall because the only force acting is gravity, which imparts the same acceleration to all objects, eliminating apparent weight as measured by contact forces like normal force.^[14] Free fall represents a trajectory where gravitational attraction is the sole influence, resulting in weightlessness for all objects within the falling frame, independent of their mass or density.^[15] In this state, observers and objects inside a freely falling enclosure, such as an elevator, perceive no gravitational effects, as their acceleration matches that of the enclosure itself. Einstein illustrated this through a thought experiment: an observer in a sealed elevator cannot distinguish whether they are in deep space far from any gravitational sources or in free fall within a gravitational field, as both scenarios yield identical local physics with no detectable weight.^[16] This indistinguishability holds because the principle equates the experience of gravity with uniform acceleration, rendering weightlessness a direct consequence of such equivalence. The equivalence principle forms the foundational insight for Einstein's general theory of relativity, which reinterprets gravity not as a force but as the curvature of spacetime induced by mass and energy.^[17] In this framework, weightlessness in free fall corresponds to motion along geodesics in curved spacetime, where the absence of tidal forces—differences in gravitational pull across an extended object—mimics a zero-gravity environment. Mathematically, within a sufficiently small region, the gravitational field can be approximated as uniform, allowing the acceleration of free fall to precisely replicate the conditions of an inertial frame devoid of gravity, thus upholding the principle's predictions.^[18]

Simulation Methods

Parabolic Aircraft Flights

Parabolic aircraft flights simulate weightlessness by flying a modified airplane in a series of parabolic arcs, creating brief periods of microgravity through controlled free fall. The aircraft typically climbs at a steep angle of approximately 45 degrees for about 20 seconds, subjecting passengers to around 1.8 g of acceleration, before reducing engine thrust and pushing over the top of the parabola at an altitude of roughly 8 kilometers. This initiates a free-fall trajectory lasting 20 to 25 seconds, during which the interior experiences near-weightlessness as the plane and its contents fall together under gravity alone, followed by a 20-second pull-out phase returning to 1 g.^[19]^[20] The historical development of these flights traces back to NASA's KC-135 program in the 1960s, when the modified military tanker, nicknamed the "Vomit Comet," began conducting parabolic maneuvers over the Gulf of Mexico to train astronauts and test equipment for the Apollo missions. The KC-135 followed a standardized flight profile involving 30 to 40 parabolas per sortie, with each arc featuring a pull-up to 1.8 g, a zero-g phase of about 25 seconds, and a pull-out to 1.8 g, allowing repeated exposure to varying g-forces for physiological and engineering studies. This program continued until 2004, when the aging KC-135 was retired due to maintenance costs and airframe fatigue.^[21]^[22]^[19] NASA transitioned to the C-9B Skytrain II in 2005, which operated similar profiles but with enhanced instrumentation for reduced-gravity research until its retirement in 2014, after which NASA contracted commercial providers for parabolic services, including ongoing campaigns as of 2025.^[19] The European Space Agency (ESA) advanced its own program with the introduction of the Airbus A310 Zero-G in 2015, operated by Novespace from Bordeaux-Mérignac Airport in France, marking a shift to a more modern, fuel-efficient platform for microgravity campaigns. As of 2025, the A310 remains active, supporting ESA's research with flights executing 31 parabolas per mission, each providing 20 seconds of weightlessness amid 1.8 g transitions.^[23]^[24] Commercially, the Zero-G Corporation offered public parabolic flights from 2004 until August 2025 using a modified Boeing 727 aircraft, known as G-Force One, enabling civilians, researchers, and trainees to experience weightlessness without government affiliation. These flights accommodated up to 35 passengers, who received pre-flight briefings, flight suits, and anti-nausea aids like Dramamine, while adhering to strict FAA Part 121 safety standards equivalent to commercial airlines, including redundant systems and medical oversight for a spotless safety record over more than 900 missions. Passengers reported sensations of floating, somersaulting, and brief disorientation during the parabolas, with post-flight celebrations featuring photos and memorabilia to commemorate the experience. Operations were paused in August 2025 due to certification issues, with resumption unclear as of November 2025.^[25]^[26] Each parabolic flight typically delivers 20 to 30 seconds of high-quality microgravity per arc, enabling up to 30 to 40 parabolas over a 60- to 90-minute mission, though durations can vary slightly by aircraft and atmospheric conditions. For instance, the Zero-G Boeing 727 achieved about 30 seconds per parabola across 15 arcs, totaling around 7.5 minutes of cumulative weightlessness, while the ESA A310 targets 20 seconds of zero g within its 31 parabolas. However, the quality of microgravity is not perfect, as atmospheric turbulence, wind gusts, or pilot corrections can introduce residual accelerations up to 0.05 g, potentially disrupting sensitive experiments and reducing the effective free-fall purity compared to orbital conditions.^[19]^[20]^[25]^[27]

Drop Towers and Ground Facilities

Drop towers simulate weightlessness by releasing experimental capsules from significant heights within evacuated shafts, allowing them to undergo free fall with minimal air resistance and achieving microgravity levels as low as 10^{-6} g.^[28]^[29] This principle leverages the equivalence of gravitational acceleration and inertial motion in a vacuum, providing short periods of pure weightlessness for scientific investigations.^[30] Prominent facilities include NASA's Zero Gravity Research Facility at the Glenn Research Center, operational since 1966, which offers 5.18 seconds of microgravity in a 510-foot (155 m) underground vacuum chamber.^[31] The ZARM Drop Tower at the University of Bremen in Germany, established in 1990, provides up to 9.3 seconds of microgravity through catapult-assisted drops from a 146-meter tower, following an initial standard drop duration of 4.74 seconds.^[32]^[33] Japan's Japan Microgravity Center (JAMIC) drop tower, with a 710-meter depth, delivered up to 10 seconds of microgravity for materials and combustion research until its closure in 2003.^[34] These systems employ drop capsules, typically up to 1 meter in diameter, that house experiments and are released into the vacuum shaft; upon reaching the bottom, deceleration occurs via energy-absorbing materials such as polystyrene granules or foam, limiting impact forces to around 30 g to protect payloads.^[35]^[36] Drop towers are advantageous for their cost-effectiveness in testing non-biological samples, high repeatability with multiple runs per day, and recent enhancements like catapult mechanisms that extend microgravity durations beyond traditional free falls.^[37] However, their primary limitations include very brief microgravity periods ranging from 2 to 10 seconds, which restrict complex dynamic studies, and the inability to accommodate human subjects due to safety constraints.^[37]^[38]

Orbital and Suborbital Spaceflight

In orbital mechanics, weightlessness is achieved during circular orbits when the centripetal acceleration required for the spacecraft's curved path exactly balances the gravitational acceleration toward Earth's center, resulting in a state of continuous free fall. This balance is described by the equation \frac{[G](/page/G)M}{r^2} = \frac{[v](/page/Velocity)^2}{r}, where G is the gravitational constant, M is Earth's mass, r is the orbital radius, and v is the orbital velocity.^[39]^[40] Suborbital spaceflights provide brief periods of weightlessness through ballistic trajectories that arc above the Kármán line at approximately 100 km altitude before falling back to Earth. Blue Origin's New Shepard rocket, operational since its first crewed flight in 2021, delivers about three minutes of high-quality microgravity during its 11-minute total journey.^[41] Similarly, Virgin Galactic's SpaceShipTwo, with spaceflights beginning in 2018 and commercial operations from 2021, offers four to five minutes of weightlessness per flight, peaking near 100 km.^[42]^[43] In contrast, orbital spaceflight sustains weightlessness for extended durations by maintaining a stable orbit around Earth. The International Space Station (ISS), operational since 1998, provides microgravity environments lasting six months or more per expedition, with residual accelerations typically below $10^{-6} g during quiescent periods, enabling long-term scientific research.^[44]^[45] Historical milestones include Yuri Gagarin's pioneering one-orbit flight on Vostok 1 in 1961, marking the first human experience of orbital weightlessness for 108 minutes.^[44] Emerging private initiatives, such as Axiom Space's planned station module launching to dock with the ISS in 2027, aim to extend commercial orbital access beyond the ISS's retirement.^[46] Suborbital flights primarily support short-duration tourism and targeted research experiments, limited by their parabolic paths, while orbital platforms like the ISS facilitate in-depth studies requiring prolonged microgravity exposure.^[47]^[48]

Laboratory-Based Techniques

Neutral buoyancy techniques simulate weightlessness by submerging objects or astronauts in water tanks, where the buoyant force counters gravitational pull to create an apparent zero-gravity environment. This method relies on Archimedes' principle, adjusting the density of submerged items through weights or foam to achieve neutral buoyancy, allowing free movement as in microgravity. Developed for astronaut training, it provides a controlled, Earth-based analog for extravehicular activities (EVAs).^[49] NASA's Neutral Buoyancy Laboratory (NBL), located at the Johnson Space Center in Houston, exemplifies this approach with its massive indoor pool measuring 202 feet long, 102 feet wide, and 40 feet deep, holding 6.2 million gallons of chlorinated water maintained at 84–86°F. Established in 1997 as part of the Sonny Carter Training Facility, the NBL evolved from earlier facilities: neutral buoyancy training began in 1966 for Gemini missions using external pools, followed by NASA's Water Immersion Facility in 1967—a 25-foot diameter, 16-foot deep tank—and the Weightless Environment Training Facility in 1980. Today, the NBL supports EVA training for International Space Station assembly and future exploration missions by deploying full-scale mockups of spacecraft and habitats underwater.^[50]^[49] Rotational devices, such as clinostats and Random Positioning Machines (RPMs), offer another laboratory method to mimic weightlessness by continuously reorienting samples relative to the gravity vector, effectively averaging its direction over time to simulate microgravity. Clinostats, first introduced in 1879 by Julius von Sachs for plant studies, rotate samples around a single axis to counteract gravitropism. Since the 1980s, RPMs—developed in the Netherlands by Dutch Space—have advanced this concept with two independently motorized frames for three-dimensional rotation, randomizing orientation at speeds exceeding biological response times (e.g., 60 degrees per second) while minimizing centrifugal forces. These devices are particularly suited for biological research, enabling long-duration experiments on cell cultures without the intermittency of free-fall methods.^[51]^[52] Two-dimensional (2D) clinostats, which rotate flat or layered samples around one horizontal axis, simulate microgravity by averaging the 1g gravity vector for thin specimens like cell monolayers, reducing directional cues and promoting isotropic growth. In contrast, 3D RPMs extend this to complex, volumetric organisms or tissues by rotating around two axes, providing a more uniform averaging of gravity and minimizing artifacts from single-axis motion. The 3D approach is preferred for three-dimensional models, such as organoids or small animals, as it better approximates the random orientation in true microgravity.^[51] These techniques find primary applications in pre-flight astronaut training at facilities like the NBL, where simulations prepare crews for spacewalk procedures, and in biological experiments using RPMs to study cellular responses, such as gene expression and tissue development under simulated weightlessness. For instance, RPMs facilitate 3D cell culturing to investigate microgravity's effects on mammalian cells, serving as ground-based analogs for spaceflight hardware validation. However, limitations persist: neutral buoyancy introduces residual drag from water viscosity and potential Coriolis forces during motion, while clinostats and RPMs generate shear stresses and incomplete gravity cancellation, leading to discrepancies in biological outcomes compared to actual orbital microgravity.^[49]^[51]^[37] Recent advances in the 2020s integrate rotational simulators with centrifugation for partial gravity studies. The European Space Agency's (ESA) Large Diameter Centrifuge (LDC) at ESTEC, with its 8-meter arms generating 1–20g hypergravity, combines with RPMs to explore fractional g environments (e.g., lunar or Martian levels) by modulating rotation speeds. In 2024, ESA's Academy Experiments Programme utilized the LDC and RPM for projects like Team SelenarFungi's two-week study on lettuce cultivation with mycorrhizal fungi in regolith simulants, assessing plant growth under altered gravity to inform future space agriculture.^[53]^[54]^[55]

Human Physiological Impacts

Acute Effects

Upon entry into weightlessness, astronauts commonly experience space motion sickness (SMS), a condition affecting approximately 70% of individuals during the first 1-3 days of spaceflight.^[56] Symptoms include nausea, vomiting, headache, pallor, cold sweating, and malaise, primarily resulting from sensory conflict between the vestibular, visual, and proprioceptive systems in the absence of gravity.^[57] This conflict arises as the brain receives mismatched signals, leading to disorientation and gastrointestinal distress.^[58] Incidence is higher among women, potentially due to greater susceptibility to motion sickness in general.^[59] A prominent acute response is the headward fluid shift, where blood and other bodily fluids redistribute toward the upper body within hours of microgravity exposure.^[60] This cephalad movement, driven by the loss of hydrostatic pressure gradients, causes facial puffiness (edema), nasal congestion, and a noticeable reduction in leg volume, often described as "puffy face and chicken legs."^[61] The shift contributes to headaches and can exacerbate symptoms of SMS.^[62] Vestibular disturbances further compound initial adaptation, as the otolith organs in the inner ear, which detect linear acceleration including gravity, no longer register a consistent gravitational vector.^[63] This leads to spatial disorientation and illusions, such as perceived tilting or inversion, impairing balance and coordination during the early phase of flight.^[64] These effects typically peak shortly after launch and subside as the nervous system adapts over days. Early manifestations of spaceflight-associated neuro-ocular syndrome (SANS) also emerge acutely, linked to elevated intracranial pressure from the fluid shifts.^[65] Signs include globe flattening of the eye, detectable via imaging, which can alter visual acuity and contribute to hyperopic shifts.^[66] To mitigate SMS, pre-flight administration of scopolamine, an anticholinergic agent, is often employed to reduce nausea and vomiting severity.^[67]

Chronic Effects

Prolonged exposure to weightlessness induces profound adaptations in the human musculoskeletal system, primarily through the elimination of mechanical loading that normally stimulates bone and muscle maintenance. Bone mineral density decreases at a rate of 1-2% per month in weight-bearing regions, with trabecular bone—such as in the vertebrae and pelvis—being most vulnerable due to heightened resorption and reduced formation driven by absent gravitational forces.^[68]^[69]^[70] Skeletal muscle experiences rapid atrophy, with losses reaching up to 20% in antigravity muscles like those in the legs and back within the first two weeks, exacerbated by diminished neural activation and protein synthesis in microgravity.^[71] The cardiovascular system undergoes deconditioning from sustained weightlessness, beginning with a 10-15% reduction in plasma volume during the initial weeks as fluids shift cephalad, leading to decreased overall blood volume and cardiac output adaptation.^[72] This contributes to orthostatic intolerance upon re-entry to gravity, where astronauts struggle to maintain arterial pressure in upright postures, often requiring supportive measures for mobility.^[73] Over longer durations, the heart muscle remodels with atrophy and reduced mass, reflecting the lower workload in microgravity and potential vascular stiffness changes.^[74] Immunological function is compromised in chronic weightlessness, with T-cell proliferation and activation suppressed, impairing adaptive immunity and cytokine production.^[75] Latent viruses, including Epstein-Barr and varicella-zoster, frequently reactivate due to this dysregulation and stress hormones, elevating the risk of opportunistic infections during and after missions.^[76] Visual impairments arise from spaceflight-associated neuro-ocular syndrome (SANS), affecting 20-30% of long-duration astronauts and characterized by optic disc edema from intracranial pressure alterations and fluid shifts.^[77] Studies from Mir missions in the 1990s and ongoing International Space Station research document significant bone loss in the lumbar spine after six months, underscoring the cumulative impact on skeletal integrity.

Countermeasures and Adaptations

Astronauts aboard the International Space Station (ISS) follow rigorous exercise regimens as a primary countermeasure against the musculoskeletal deconditioning induced by weightlessness. The Advanced Resistive Exercise Device (ARED), installed in 2008, utilizes a piston and flywheel system to simulate gravitational loading through up to 30 different resistance exercises, mimicking weightlifting to target muscle and bone preservation.^[78]^[79] These protocols typically require approximately 2.5 hours of daily exercise, combining 60 minutes of resistance training six days per week with 30 minutes of aerobic activity four to seven days per week, using devices like ARED alongside treadmills and cycle ergometers.^[80]^[81] Pharmacological interventions complement exercise to address specific physiological challenges in weightlessness. Bisphosphonates, such as alendronate, have been tested since the early 2000s in clinical trials to mitigate bone loss by suppressing osteoclast activity and reducing resorption rates during spaceflight.^[82]^[83] For instance, the Bisphosphonate Flight Experiment on the ISS demonstrated that alendronate, when combined with resistive exercise, enhanced bone mass preservation compared to exercise alone by further inhibiting bone breakdown.^[84] Additionally, anti-nausea medications like promethazine (administered intramuscularly at 25-50 mg) and scopolamine (0.4 mg orally) are used to counteract space motion sickness, which affects up to 70% of crew members shortly after launch.^[58]^[59] Nutritional strategies play a crucial role in supporting bone health amid demineralization risks. High-calcium diets, providing 1,000-1,200 mg daily, paired with vitamin D supplementation of 800 IU per day, help maintain calcium balance and prevent elevations in serum calcium levels during missions, as evidenced by studies on ISS crews.^[85]^[86] These interventions counteract the reduced vitamin D synthesis from limited ultraviolet exposure in space, ensuring adequate absorption for skeletal integrity.^[87]^[88] Emerging technologies offer promising avenues for more comprehensive mitigation. Lower body negative pressure (LBNP) devices simulate gravitational fluid shifts by applying negative pressure to the lower extremities, thereby countering cephalad fluid redistribution and generating ground-reaction forces to support cardiovascular and musculoskeletal health.^[89]^[90] Artificial gravity via centrifugation, proposed for future deep-space missions like those to Mars, involves rotating habitats to produce centripetal acceleration equivalent to partial Earth gravity, potentially integrating with exercise to prevent deconditioning more effectively than current methods.^[91]^[92] The effectiveness of these countermeasures varies, with exercise protocols significantly attenuating muscle atrophy—reducing losses by up to 50% in key muscle groups compared to early missions without such regimens—though full recovery of bone density often requires several months to years post-flight.^[93]^[78]^[94] In the Artemis program, 2025 updates from ongoing standard measures investigations, including Artemis II preparations, emphasize integrated exercise and pharmacological approaches to inform countermeasures for lunar and Mars missions, with ultrasound and biomarker data highlighting persistent needs for optimization against prolonged weightlessness.^[95]^[96]

Biological Effects on Non-Humans

Cellular and Molecular Responses

In non-human organisms, exposure to weightlessness induces significant alterations in gene expression, particularly the upregulation of stress-related genes. Studies conducted using Biological Research in Canisters (BRIC) experiments on the International Space Station (ISS) have demonstrated that microgravity triggers changes in genes associated with hypoxia, heat shock responses, and cell wall remodeling in plant seedlings, such as Arabidopsis thaliana.^[97] In microbial systems, similar BRIC investigations reveal upregulation of stress genes involved in cytoskeleton remodeling, enabling adaptation to the absence of gravitational cues and preventing structural collapse in bacteria and yeast.^[98] These transcriptional shifts highlight microgravity's role as a potent environmental stressor, promoting survival mechanisms at the molecular level.^[99] At the cellular signaling level, weightlessness disrupts mechanotransduction pathways, which rely on gravitational forces to transmit mechanical signals into biochemical responses. In bacteria like Deinococcus radiodurans, simulated microgravity alters the abundance of signal transducer proteins, leading to impaired stress sensing and modified metabolic pathways.^[100] Yeast cells, such as Saccharomyces cerevisiae, exhibit similar disruptions under low-shear modeled microgravity, with changes in genomic expression affecting mechanosensitive pathways that regulate cell wall integrity and protein synthesis.^[101] These alterations result in reduced protein synthesis efficiency and altered cellular morphology, as mechanotransduction fails to integrate gravitational input for proper cytoskeletal organization.^[102] Weightlessness also compromises DNA repair mechanisms, increasing mutation rates in microbial populations. NASA studies from the 2000s on Escherichia coli cultures exposed to spaceflight conditions showed elevated mutagenesis compared to ground controls, attributed to hindered DNA repair pathways under microgravity.^[103] More recent simulated microgravity experiments confirm that prolonged exposure leads to the accumulation of unique mutations in E. coli, particularly under nutrient-limited conditions, enhancing adaptive evolution but risking genomic instability.^[104] Microgravity exacerbates oxidative stress by elevating levels of reactive oxygen species (ROS) in cells, as the lack of gravitational orientation disrupts normal antioxidant signaling. In non-human cell models, including plant and microbial systems, simulated and real microgravity conditions increase ROS production, leading to mitochondrial dysfunction and lipid peroxidation without the regulatory cues provided by Earth's gravity.^[105] This oxidative imbalance activates compensatory pathways but can overwhelm cellular defenses, contributing to broader molecular damage.^[106] In model organisms, weightlessness induces shifts in apoptosis regulation at the cellular level. In Caenorhabditis elegans, spaceflight and simulated microgravity alter apoptotic miRNA and mRNA expression profiles, promoting excessive programmed cell death in response to environmental stressors like altered gravity.^[107] Similarly, fruit fly (Drosophila melanogaster) cells exposed to microgravity show dysregulated apoptosis during development, with gene expression changes linked to enhanced cell death in neural and muscular tissues.^[108] Recent 2025 studies on rodent myogenic cells under combined simulated microgravity and radiation further indicate telomere lengthening, potentially via activation of alternative lengthening pathways, which may influence cellular senescence and longevity mechanisms.^[109]

Organismal and Ecosystem Studies

Studies of plant growth in microgravity have revealed significant alterations in developmental patterns, particularly in model organisms like Arabidopsis thaliana. Experiments conducted during NASA's Advanced Plant Experiments (APEX) missions on the International Space Station (ISS) since the 2010s demonstrate enhanced root elongation and accelerated cell proliferation in Arabidopsis seedlings under microgravity conditions, contrasting with the reduced gravitropic responses that typically orient roots downward on Earth.^[110] These changes arise from disrupted gravity-sensing mechanisms, leading to disoriented root skewing and altered cell wall composition, which could inform strategies for cultivating crops in space habitats.^[111] Such findings highlight the potential for microgravity to accelerate certain growth phases, though they pose challenges for stable space farming systems reliant on reliable plant orientation and nutrient uptake.^[112] Animal responses to weightlessness often manifest as behavioral and physiological disorientation, as observed in aquatic vertebrates. In Japanese Aerospace Exploration Agency (JAXA) investigations using medaka fish (Oryzias latipes) aboard the ISS via the Aquatic Habitat facility, microgravity induced looping swim patterns and impaired schooling behavior, attributed to fluid shifts and vestibular disturbances that mimic dizziness in higher organisms.^[113] Similarly, frog embryo development, exemplified by Xenopus laevis in NASA spaceflight experiments, exhibits anomalies such as extra cell layers during the blastula stage and delayed gastrulation, though many embryos develop into outwardly normal tadpoles capable of regulating some gravitational cues.^[114] These disruptions underscore how microgravity interferes with gravity-dependent orientation during early ontogeny, potentially affecting locomotion and habitat adaptation in space.^[115] Insect colonies and microbial communities display disorganized structures and heightened pathogenicity in weightless environments. Ant colonies of Tetramorium caespitum, tested on the ISS in 2014, showed altered collective search patterns and reduced surface adhesion, leading to frequent detachment and inefficient foraging despite maintained teamwork, indicating partial disorganization of social hierarchies.^[116] Concurrently, microbial ecosystems like Salmonella enterica serovar Typhimurium form denser biofilms and exhibit increased virulence in microgravity, as evidenced by NASA's OS-526 experiment, where spaceflight cultures displayed upregulated adhesion genes and enhanced lethality in mouse models compared to ground controls.^[117] These shifts suggest that weightlessness promotes biofilm stability at the expense of balanced community dynamics, raising concerns for contamination control in enclosed space habitats.^[118] Multi-generational studies on mammals demonstrate successful reproduction under prolonged microgravity exposure. On the ISS in the 2020s, mouse reproduction experiments showed viable initial embryo development from space-exposed sperm, with F1 and F2 offspring of space-flown females exhibiting health issues including metabolic and behavioral deficits.^[119]^[120]^[121] As of 2025, experiments have successfully produced healthy offspring from mouse stem cells exposed to six months of ISS conditions, indicating resilience in reproductive cells to space environments.^[122] These effects, linked to disrupted endocrine signaling and germline instability, indicate cumulative impacts on reproductive success over multiple cycles.^[120]^[121] Simulations of ecosystems in closed-loop bioreactors further illustrate imbalances induced by microgravity. The Closed Equilibrated Biological Aquatic System (CEBAS) on STS-90 demonstrated a stable closed aquatic ecosystem in microgravity, with effective nutrient cycling but challenges in gas management leading to differences in oxygen distribution and system dynamics compared to 1g controls.^[123]^[124] In broader bioregenerative life support systems (BLSS), microbial and plant interactions in space analogs reveal non-optimal nutrient fluxes, where upstream processes cause dynamic imbalances in crop cultivation, emphasizing the need for gravity-mimicking countermeasures to sustain closed ecosystems.^[125]

Applications and Research Outcomes

Materials Science Advancements

Weightlessness provides a unique environment for materials science by eliminating buoyancy-driven convection and sedimentation, allowing for more controlled growth and processing of materials that are distorted by gravity on Earth. This absence of gravitational effects enables the production of higher-quality crystals and alloys with fewer defects, uniform compositions, and enhanced properties, which have applications in electronics, optics, and manufacturing.^[126] In crystal growth, microgravity facilitates the formation of defect-free protein crystals by minimizing convective flows that disrupt nucleation and growth on Earth. NASA's Protein Crystal Growth (PCG) experiments, conducted on Space Shuttle missions such as STS-37, demonstrated this advantage, producing crystals up to 10 times larger than ground controls through techniques like vapor diffusion and batch methods. These larger, more ordered crystals improved X-ray diffraction resolution, aiding structural biology research.^[127] Similarly, inorganic crystals benefit, as the lack of sedimentation allows for slower, more uniform incorporation of atoms into the lattice.^[126] For semiconductors and alloys, the Bridgman technique in microgravity yields highly uniform crystals by suppressing melt convection, resulting in consistent dopant distribution and reduced inclusions. Experiments on gallium arsenide (GaAs) crystals, including those supported by the European Space Agency (ESA) in the 2000s, produced materials with superior structural quality and fewer defects compared to Earth-grown counterparts. These improvements enhance electrical resistivity and performance in optic applications, such as lasers and detectors. A meta-analysis of over 160 microgravity experiments confirms that 83% showed greater compositional uniformity in semiconductors like GaAs.^[128]^[129] Combustion studies in weightlessness reveal behaviors unattainable on Earth, such as perfectly spherical flames around fuel droplets due to the absence of buoyancy-induced flow. The Flame Extinguishment Experiment (FLEX) on the International Space Station (ISS) in the 2010s investigated droplet combustion with fuels like heptane and methanol, observing reduced soot production in certain conditions—methanol flames produced minimal soot, appearing as dim blue spheres. These findings inform models for cleaner fuel combustion on Earth, enabling designs with lower emissions and improved efficiency for engines and industrial processes.^[130]^[131] Commercial outcomes from these advancements include in-orbit manufacturing technologies, exemplified by Made In Space (now part of Redwire), which deployed the first 3D printer to the ISS in 2014. This system successfully produced functional parts like tools from plastic filaments, demonstrating that microgravity does not hinder additive manufacturing and can even enhance material properties such as tensile strength. The global in-space manufacturing market, encompassing space-derived materials, reached USD 6.3 billion in 2025, driven by applications in optics, alloys, and beyond. In mid-2025, Varda Space Industries returned the first space-manufactured pharmaceutical crystals to Earth, advancing in-orbit drug production capabilities.^[132]^[133]^[134] Despite these advances, challenges persist in scaling production due to high launch costs, historically around $20,000 per kilogram, which limit the volume of raw materials sent to orbit and make large-scale manufacturing economically unfeasible. Even with recent reductions to about $2,700 per kilogram via reusable launchers, the expense continues to constrain experimentation and commercialization to small batches.^[135]

Biomedical and Pharmaceutical Research

Microgravity environments, such as those on the International Space Station (ISS), have enabled significant advances in drug crystallization by producing higher-quality protein crystals that are larger, more ordered, and uniform compared to those grown on Earth. This is particularly beneficial for pharmaceutical applications, including the development of treatments for diseases like cancer. In the 2010s, Merck conducted trials on the ISS to grow crystals of pembrolizumab (Keytruda), resulting in improved structural resolution that aids in designing more effective formulations with enhanced stability and injectability for cancer therapies.^[136] These efforts build on earlier shuttle missions but were scaled up via ISS access, demonstrating microgravity's role in overcoming terrestrial limitations like sedimentation that disrupt crystal formation. Insulin crystals have also been grown in microgravity, showing potential for improved diabetes treatments through better-ordered structures.^[137] In tissue engineering, microgravity facilitates the growth of scaffold-free 3D organoids that more accurately replicate human tissue architecture, providing novel models for studying diseases like cancer metastasis. For instance, in the 2020s, researchers from Encapsulate Bio launched colorectal cancer patient-derived organoids to the ISS aboard SpaceX CRS-30 in 2024, where microgravity promoted self-assembly into tumor-like clusters without gravitational distortion. These organoids exhibited distinct cell migration patterns indicative of early metastatic behavior, such as altered responses in APC-mutated cells, offering insights into invasion mechanisms not observable in ground-based 2D or scaffolded models.^[138] Ongoing trials planned for 2025 aim to expand this to multi-site studies, potentially accelerating personalized therapies by testing drug efficacy in these realistic microgravity-grown structures.^[138] Rodent studies in microgravity have proven invaluable for modeling human osteoporosis, as the rapid bone loss observed mirrors postmenopausal or spaceflight-induced demineralization, allowing efficient testing of therapeutic interventions. In experiments using mouse-derived primary osteoblasts exposed to simulated microgravity via rotary cell culture systems, treatment with parathyroid hormone-related protein (PTHrP 1-36) analogs reversed microgravity-induced cell death and restored anabolic signaling pathways, as evidenced by microarray analysis of gene expression changes.^[139] These findings, from NASA's OSD-107 study released in 2016 but informing ongoing ISS rodent missions, highlight PTH analogs' potential to counteract bone resorption by modulating osteoblast viability and mineralization, providing a translational model for Earth-based osteoporosis therapies.^[139] Microgravity research has also enhanced vaccine production by promoting more uniform antigen structures, which can improve immunogenicity and manufacturing consistency. In the 2000s, NASA-initiated studies, beginning around 1998 with bacterial vaccines like Salmonella, explored antigen growth in microgravity to reduce aggregation and achieve better particle uniformity in cell cultures.^[140] This approach, later validated in ISS experiments like Sanofi Pasteur's 2020 influenza virus cultivation in MDCK cells, demonstrated higher yields of consistent antigens, potentially leading to more effective seasonal flu vaccines with reduced variability in immune response.^[141] NASA's ongoing ISS research has tested CRISPR-Cas9 in microgravity, with 2021 demonstrations (Genes in Space-5) confirming efficient genome editing in yeast cells to study DNA repair mechanisms under space radiation conditions. Collaborations with pharmaceutical companies, such as Merck's continued ISS protein studies, underscore industry investment in space-based biomedical tools to fast-track therapies for degenerative diseases.^[142]^[136]

References

[1]
What Is Microgravity? (Grades 5-8) - NASA
Feb 15, 2012 · Microgravity is the condition in which people or objects appear to be weightless. The effects of microgravity can be seen when astronauts and objects float in ...Missing: physics | Show results with:physics
[2]
What is Microgravity? - NASA
Feb 13, 2009 · Objects in a state of free fall or orbit are said to be weightless. The object's mass is the same, but it would register “0” on a scale. Weight ...Missing: physics | Show results with:physics
[3]
[PDF] Chapter 1 THE GRAVITY OF THE SITUATION
proven prior to undertaking such challenging missions. 1. Weightlessness is the experience (by people and objects) during freefall, of having zero-g force (0 ...
[4]
On Defining Weight and Weightlessness | The Physics Teacher
Sep 1, 2024 · The weight of an object arises when a nongravitational force prevents the free fall of that object through the universal gravitational field.
[5]
Weightlessness* – Body Physics: Motion to Metabolism
However, your weight is certainly not zero because weight is just another name for the force of gravity, which is definitely acting on you while you free fall.
[6]
Newton's First Law Applied to a Falling Object
Since there is no initial air resistance, the object begins to free fall and accelerate. But as the object velocity increases, it encounters air resistance, or ...<|control11|><|separator|>
[7]
[PDF] Physics 101: Lecture 05 - Free Fall and Apparent Weight
Free Fall. ○ Only force acting on object is GRAVITY. →Newton's 2nd Law F. Net. , y. = ma y. →Force is Weight = mg (near surface of earth). » F. Net, y. = ma y.
[8]
6.5 Newton's Universal Law of Gravitation - College Physics 2e
Jul 13, 2022 · Newton's universal law of gravitation and his laws of motion answered very old questions about nature and gave tremendous support to the notion ...Missing: perpetual | Show results with:perpetual
[9]
Weightlessness in Orbit - The Physics Classroom
These sensations are common to any situation in which you are momentarily (or perpetually) in a state of free fall. ... Newton's second law of motion to solve the ...
[10]
6.4: Orbital Motion - Physics LibreTexts
Sep 4, 2024 · As we just learned, objects in orbit are in free fall; they have nothing exerting a normal force against them and thus no weight. Tap to ...
[11]
Weight, apparent weight, and weightlessness (video) - Khan Academy
Oct 6, 2025 · A system appears weightless when there are no forces exerted on the system, or when the force of gravity is the only force exerted on the system. Created by ...<|control11|><|separator|>
[12]
Equivalence Principle | The Eöt-Wash Group
The simplest way to state the equivalence principle is this: inertial mass and gravitational mass are the same thing. Then, gravitational force is ...
[13]
4. Gravitation - Lecture Notes on General Relativity - S. Carroll
... Equivalence Principle, or WEP. The WEP states that the "inertial mass" and "gravitational mass" of any object are equal. To see what this means, think about ...
[14]
13.7 Einstein's Theory of Gravity – University Physics Volume 1
In Einstein's general theory, there is no difference between free fall and being weightless. This is called the principle of equivalence. The equally ...
[15]
[PDF] General Relativity (1916) Equivalence Principle Acceleration ...
It's surprising because equivalence principle then states that gravity can be canceled, or mimicked, by acceleration. – Case 1: Free-fall (gravity canceled). – ...
[16]
Remarks on General Relativity - Galileo
This is called the Equivalence Principle. The acceleration could also be used to cancel an existing gravitational field—for example, inside a freely falling ...
[17]
[PDF] Lecture 10: General Relativity I
Sep 25, 2018 · principle – when gravity is present, the inertial frames of Special Relativity should be identified with free-falling frames of reference. ✦ ...
[18]
Tides and Gravity | Physics Van | Illinois
Mar 26, 2015 · That absence of effects from uniform gravitational fields is called the Equivalence Principle, and forms the basis of General Relativity.
[19]
Parabolic Flight - NASA
Purpose: Parabolic flight research allows scientists to conduct Earth-based studies that could lead to enhanced astronaut safety and performance.
[20]
ESA - Airbus A310 Zero-G - European Space Agency
The Airbus A310 Zero-G aircraft generally executes 31 parabolic manoeuvres during flight. From a steady horizontal flight, the aircraft gradually pulls up and ...
[21]
[PDF] Thank You for Flying the Vomit Comet
The "Vomit Comet" (C9) is NASA's aircraft that creates microgravity using parabolic maneuvers over the Gulf of Mexico.Missing: mechanism history
[22]
[PDF] 19660026484.pdf - NASA Technical Reports Server (NTRS)
profile for the KC-135, described elsewhere in detail (l), consisted essentially of a ballistic traiectwy with a weightless period of about twenty-five to ...Missing: history | Show results with:history<|separator|>
[23]
Airbus A310 Zero-G (Experimental Microgravity Flights for Research)
May 7, 2015 · The Airbus A310 “ZERO-G” aircraft generally executes a series of 31 parabolic maneuvers during flight. From a steady horizontal flight, the ...
[24]
A sensational Zero-G campaign for teams CAVE 0g and MVIPER
Sep 30, 2025 · ... ESA parabolic flight campaign in September 2025. Flying aboard Novespace's Airbus A310 from Bordeaux-Mérignac Airport, the teams tested ...
[25]
Take Your First Step Into Space & Be Part Of The Zero-G ...
Yes, zero gravity flights are perfectly safe. Not only are we held to the exact same Part 121 safety standards as passenger airlines like Delta, Southwest, and ...Public Flights · Private Flights · Research Flights · Corporate Flights
[26]
Zero Gravity Corporation Wins NASA Contract to Provide ...
Jan 2, 2008 · ZERO-G operates under the highest safety standards as set by the FAA (Part-121) with its partner Amerijet International of Ft. Lauderdale ...
[27]
[PDF] Use of aircraft for zero-gravity environment
Unstable air masses can degrade the trajectory quality because of the inability of the pilot to react to wind gusts and local perturbations. Because the ...
[28]
Microgravity and drop towers - European Space Agency
Drop towers offer the best microgravity levels - as low as 10 -6 g - and are the most flexible and adaptable platforms for many scientific experiments.Missing: simulation principle
[29]
Microgravity Level Measurement of the Beijing Drop Tower Using a ...
Aug 17, 2016 · Drop tower is the most common ground-based facility to provide microgravity environment and widely used in many science experiments.
[30]
How (and why) do NASA researchers simulate microgravity on Earth?
Feb 12, 2024 · These ground-based Towers support the dropping of experiments with low drag from air, due to creating a vacuum in the tower before the drop and ...
[31]
Reduced Gravity Drop Towers and Test Rigs - NASA
The Zero Gravity Research Facility is the largest microgravity research drop tower in the world and one of 2 drop towers located at the NASA Glenn Research ...Missing: details | Show results with:details
[32]
Labs and Test Facilities - ZARM - Universität Bremen
The main facility of ZARM is the Bremen Drop Tower, a worlwide unique research laboratory for short-term experiments under microgravity conditions. For more ...
[33]
ESA - The ZARM drop tower in Bremen - European Space Agency
In the drop mode the capsule is released from a height of 120 m giving 4.74 s of microgravity experiment time. The capsule experiences a deceleration of up to ...
[34]
Ignition and combustion of metal fuels under microgravity
JAMIC drop tower of the Microgravity Center [23] in Japan has a total depth of 490 m, providing a microgravity environment of up to 10 s with a precision of 10− ...
[35]
[PDF] Bremen Drop Tower - Payload User's Guide - ZARM
Apr 22, 2025 · After capsule deceleration, all experiment data are stored on board or downloaded for. Bremen Drop Tower - Payload User's Guide - Version 1.6.
[36]
Controlled partial gravity platform for milligravity in drop tower ...
Apr 25, 2025 · The partial gravity environment is created by a two stage approach: First, we place the experiment in the microgravity of a free-falling drop ...Missing: principle | Show results with:principle
[37]
Advantages and Limitations of Current Microgravity Platforms ... - MDPI
Drop tower platforms have many advantages. They are medium-cost and have relatively easy-to-handle safety requirements. Multiple experiments can be performed ...
[38]
(PDF) Advantages and Limitations of Current Microgravity Platforms ...
Oct 15, 2025 · such forces. Drop tower platforms have many advantages. They are medium-cost and have. relatively easy-to-handle safety requirements ...
[39]
Chapter 3: Gravity & Mechanics - NASA Science
Jan 16, 2025 · To move in a curved path, a planet must have an acceleration toward the center of the circle. This is called centripetal acceleration.Missing: equation | Show results with:equation
[40]
[PDF] On-Orbit Satellite Servicing Study - Project Report - NASA
centripetal acceleration balances the gravitational acceleration between the primaries, thus causing the primaries to remain stationary in the rotating ...
[41]
First Commercial Payloads Onboard New Shepard | Blue Origin
Dec 21, 2017 · During this flight, our customers get approximately three minutes in a high-quality microgravity environment, at an apogee around 100 kilometers ...
[42]
How Virgin Galactic's SpaceShipTwo Passenger Space Plane ...
Jul 6, 2021 · Passengers experience five minutes of weightlessness. SpaceShipTwo's rudders are configured in "feathered" mode for re-entry into the ...
[43]
Virgin Galactic flight to the edge of space: your questions answered
Jul 11, 2021 · The trip will last in total about two and a half hours. However, Branson and his team will only be weightless in space for four to five minutes ...
[44]
April 1961 - First Human Entered Space - NASA
Nov 3, 2023 · Yuri Gagarin from the Soviet Union was the first human in space. His vehicle, Vostok 1 circled Earth at a speed of 27,400 kilometers per hour ...
[45]
[PDF] International Space Station Increment–6/8 Microgravity Environment ...
The residual acceleration environment of an orbiting spacecraft in a low earth orbit is a complex phenomenon[1]. Many factors, such as experiment operation ...
[46]
Axiom Space Raises $350M at Series-C Close with $2.2B+ in ...
Aug 21, 2023 · Axiom Station's first module is under construction and is scheduled to launch to the ISS by 2026. Additional modules will follow to build out ...
[47]
New Shepard | Blue Origin
During the 11-minute journey, astronauts soar past the Kármán line (100 km/62 miles), the internationally recognized boundary of space, experiencing several ...Fly to Space · Reserve a Seat · Payloads
[48]
[PDF] NP-2015-11-040-JSC-Acceleration Environment-ISS-mini-book ...
Denser portions give rise to more drag and thus higher acceleration levels. ... The microgravity acceleration environment of the ISS is quite dynamic. The ...
[49]
Neutral Buoyancy Facilities for Spacewalk Training - NASA
Oct 6, 2021 · In 1966, NASA began to use neutral buoyancy as a higher-fidelity tool for spacewalk training, a method astronauts still rely on today.
[50]
Neutral Buoyancy Laboratory - NASA
The NBL is a large indoor pool used for mission planning, astronaut training, and manipulating buoyancy to simulate gravity. It has a volume of 6.2 million ...
[51]
Simulated Microgravity: Critical Review on the Use of Random ...
Short-term effects of microgravity (on the order of seconds) can be studied on research platforms such as drop towers or airplanes that fly in parabolic ...
[52]
Some history and use of the random positioning machine, RPM, in ...
In this essay I want to go into the use of instruments in gravity related research with emphases on the Random Positioning Machine, RPM.
[53]
ESA - Large Diameter Centrifuge - European Space Agency
A Large Diameter Centrifuge (LDC) has been developed by ESA that can cater to experiments requiring hypergravity conditions ranging from 1 to 20 g.
[54]
Seven new teams selected for the ESA Academy Experiments ...
Mar 5, 2024 · ... Large Diameter Centrifuge and Random Positioning Machines (RPM) at ESA ESTEC in The Netherlands. They plan to cultivate lettuce with ...
[55]
Pharmacological and non-pharmacological countermeasures to ...
Jun 15, 2023 · Space Motion Sickness (SMS) is a syndrome that affects around 70% of astronauts and includes symptoms of nausea, dizziness, fatigue, ...
[56]
Space motion sickness: incidence, etiology, and countermeasures
Oct 30, 2006 · Space motion sickness symptoms are similar to those in other forms of motion sickness; they include: pallor, increased body warmth, cold ...
[57]
OS-746 - NASA OSDR
Space motion sickness is characterized by symptoms of spatial disorientation, nausea, and vomiting. It affects approximately 70% of the crew during space ...
[58]
Pharmacological and non-pharmacological countermeasures to ...
Jun 16, 2023 · Studies have found that, age negatively correlates with motion sickness susceptibility, and females have a higher susceptibility to motion ...
[59]
Microgravity-Induced Fluid Shift and Ophthalmic Changes - PMC
Perhaps the most obvious and profound physiological response and adaptation to the microgravity environment is the redistribution of fluid and tissues of the ...
[60]
Mechanism of Headward Fluid Shift During Exposure To Microgravity
Jan 1, 1994 · Symptoms of this fluid shift include facial edema, nasal congestion, and headache. Normally on Earth, the human body is exposed to hydrostatic ( ...Missing: redistribution | Show results with:redistribution
[61]
Spaceflight-Associated Brain White Matter Microstructural Changes ...
Jan 23, 2019 · Conclusions and Relevance Free water redistribution with spaceflight likely reflects headward fluid shifts occurring in microgravity as well ...
[62]
Challenges to the Vestibular System in Space - PubMed Central - NIH
Nov 3, 2021 · Space-based experiments have shown that altered gravity causes structural and functional changes at multiple stages of vestibular processing.Missing: disturbances | Show results with:disturbances
[63]
Neuro-Vestibular Examination During and Following Spaceflight ...
Adaptation to microgravity during spaceflight causes neurological disturbances that are either directly or indirectly mediated by the vestibular system. These ...
[64]
Space flight-associated neuro-ocular syndrome (SANS) - PMC - NIH
Six astronauts had post-mission OCT and orbital/cranial MRI, and four astronauts had lumbar punctures (LP). Optic disc edema was noted in five, globe flattening ...
[65]
https://pmc.ncbi.nlm.nih.gov/articles/PMC6043524/
[66]
Impact of Gender on Pharmocokinetics of Intranasal Scopolamine
Sep 22, 2013 · Clearance of the parent compound was significantly faster and the volume of distribution was significantly higher in males than in females, As a ...Missing: incidence women
[67]
Counteracting Bone and Muscle Loss in Microgravity - NASA
Dec 1, 2023 · For every month in space, astronauts' weight-bearing bones become roughly 1% less dense if they don't take precautions to counter this loss.
[68]
Perspective on the Impact of Weightlessness on Calcium and Bone ...
It is now recognized that an unloading of the skeleton, either due to strict bed rest or in zero gravity, leads on average to a 1%–2% reduction in bone mineral ...
[69]
The effects of microgravity on bone structure and function - Nature
Apr 5, 2022 · This review introduces a plethora of on-ground research that elucidate the intricate process of bone loss, utilising technology that simulates microgravity.
[70]
The Effects of Spaceflight Microgravity on the Musculoskeletal ...
Prolonged microgravity exposure decreases bone density and muscle volume, and changes muscle fiber properties, affecting the musculoskeletal system.
[71]
Long-term spaceflight and the cardiovascular system
On Earth, orthostatic intolerance has many causes, including decreases in stroke volume, plasma volume and constriction of restriction vessels.6 Orthostatic ...
[72]
Impact of Prolonged Spaceflight on Orthostatic Tolerance During ...
Jul 19, 2019 · This study demonstrated for the first time that prolonged spaceflight did not cause orthostatic hypotension or intolerance during routine postflight activities.
[73]
Cardiovascular disease in space: A systematic review - ScienceDirect
Microgravity causes cardiac atrophy and orthostatic intolerance while space radiation may potentially accelerate atherosclerosis.
[74]
Effects of simulated space conditions on CD4+ T cells - Frontiers
Studies have found that a lack of gravitational force in space can lead to immunosuppression, characterized by a reduction in T cell activation and ...Missing: reactivation | Show results with:reactivation
[75]
Challenges for the human immune system after leaving Earth - Nature
Nov 18, 2024 · A growing body of evidence points towards immunological changes in astronauts, including heightened pro-inflammatory responses, reactivation of latent viruses, ...
[76]
Spaceflight associated neuro-ocular syndrome (SANS) and ... - Nature
Feb 7, 2020 · The optic disc edema seen both in terrestrial models of increased ICP and in SANS demonstrates a pattern of nerve fiber layer thickening ...
[77]
Bone mineral and lean tissue loss after long duration space flight
Eighteen crew members received a lumbar spine and hip DEXA scan (Hologic 1000W) before and after flight; 17 crew members received an additional whole body scan.Missing: studies | Show results with:studies
[78]
Astronaut Exercise - NASA
May 20, 2024 · Installed in 2008, ARED uses a piston and flywheel system to provide loading that essentially mimics weightlifting in weightlessness. A current ...
[79]
[PDF] Mechanism Development, Testing, and Lessons Learned for the ...
ARED is a multi-format resistive exercise machine specifically designed for a zero-gravity environment. Capable of 30 different exercises, ARED will be used ...Missing: regimen weightlessness countermeasures
[80]
[PDF] Strength and Conditioning for Astronauts Professor Paul Comfort, Ph ...
These recommendations include 60 minutes of resistance exercises ~6 days per week and 30 minutes of aerobic exercise 4-7 days per week (this is discussed in ...Missing: regimen | Show results with:regimen
[81]
[PDF] NASA-STD-3001 Technical Brief Exercise Overview OCHMO-TB-031
Oct 2, 2023 · Evaluation of the effects of ISS exercise countermeasures on multisystem function using latest exercise (T2,. ARED, CEVIS) devices and exercise ...Missing: regimen | Show results with:regimen
[82]
Bisphosphonates as a supplement to exercise to protect bone ...
Conclusions: The combination of exercise plus an antiresoptive drug may be useful for protecting bone health during long-duration spaceflight. Publication types.
[83]
Bisphosphonate ISS Flight Experiment
Jan 1, 2014 · We tested whether an antiresorptive drug in combination with in-flight exercise would ameliorate bone loss and hypercalcuria during longduration ...
[84]
Resistive exercise in astronauts on prolonged spaceflights provides ...
We conclude that a bisphosphonate, when combined with resistive exercise, enhances the preservation of bone mass because of the added suppression of bone ...
[85]
Interventions to prevent bone loss in astronauts during space flight
High calcium intake and vitamin D supplementation during space flight does not affect bone metabolism, but prevents an elevation of serum calcium level ...
[86]
Space Flight Calcium: Implications for Astronaut Health, Spacecraft ...
Dec 18, 2012 · Recent studies have documented that supplementation with 800 IU vitamin D/day will maintain vitamin D stores in astronauts on 6-month space ...
[87]
[PDF] Calcium and Bone Metabolism During Spaceflight
The absence of ultraviolet light and decreased dietary intake of vitamin D during spaceflight diminish vitamin D pools in the body. This was observed during the ...
[88]
Physiological Alterations in Relation to Space Flight: The Role of ...
Nov 19, 2022 · Astronauts require an adequate oral intake of vitamin D and Ca2+ during spaceflights, and the amount necessary to minimize a negative balance is ...
[89]
The Mobile Lower Body Negative Pressure Gravity Suit for Long ...
Aug 5, 2020 · LBNP counteracts head-ward fluid shifts and generates ground-reaction forces (GRFs). GRFs are beneficial for maintaining bones and muscles by ...
[90]
Review article Lower body negative pressure as a research tool and ...
LBNP may prove to be a countermeasure for the multifaceted physiological changes endured by astronauts during spaceflight related to cephalad fluid shift.
[91]
A spacecraft-compatible combined artificial gravity and exercise ...
Artificial Gravity (AG) produced by centrifugation may provide an efficient countermeasure against spaceflight physiological deconditioning. The acceleration ...
[92]
[PDF] Study of artificial gravity systems for long duration space missions
It was first proposed in 2011 for long duration space missions such as trips to the Moon or Mars. The spacecraft has a modular design for a crew of 6 astronauts ...
[93]
Effects of exercise countermeasures on multisystem function in long ...
Feb 3, 2023 · Exercise training is a key countermeasure used to offset spaceflight-induced multisystem deconditioning. Here, we evaluated the effects of ...
[94]
Incomplete recovery of bone strength and trabecular ... - Nature
Jun 30, 2022 · Bone resorption was suppressed and bone loss reduced in astronauts prescribed a bisphosphonate (alendronate) compared with astronauts not on a ...<|separator|>
[95]
Artemis II Standard Measures - NASA
Sep 11, 2025 · Scientists who tap this dataset will gain insight into how isolation, confinement, weightlessness, and other space hazards affect human health ...
[96]
[PDF] Astronaut physiological deconditioning and exercise prescription ...
The ISS is equipped with hardware systems designed and engineered to support astronaut exercise countermeasures in microgravity. Over the years, this hardware ...Missing: regimen | Show results with:regimen
[97]
Comparative transcriptomics indicate changes in cell wall ...
KEY RESULTS. In our BRIC-16 experiments, we noted expression changes in genes involved in hypoxia and heat shock responses, DNA repair, and cell wall structure ...
[98]
Stress, and pathogen response gene expression in modeled ...
These proteins are induced when a cell responds to stressors such as heat, cold and oxygen deprivation. Microgravity is another stressor that may regulate HSPs.Missing: cytoskeleton remodeling microbes BRIC
[99]
Current Knowledge about the Impact of Microgravity on Gene ...
Flies reared on the ISS showed smaller and weaker hearts, reduced sarcomeric and ECM gene expression, upregulated expression of proteasome subunit genes, and ...
[100]
Molecular response of Deinococcus radiodurans to simulated ... - NIH
Our results emphasize the importance of certain signal transducer proteins, which showed higher abundances in cells grown under reduced gravity. These proteins ...<|separator|>
[101]
Yeast genomic expression patterns in response to low-shear ...
We have previously demonstrated that low-shear modeled microgravity (LSMMG) causes significant phenotypic changes of a select group of Saccharomyces cerevisiae ...Missing: mechanotransduction | Show results with:mechanotransduction
[102]
Mechanotransduction as an Adaptation to Gravity - PubMed Central
Yeast cells must maintain cell wall integrity when exposed to changes in the extracellular environment such as osmotic stress and oxidative stress (40).
[103]
Spaceflight and modeled microgravity effects on microbial growth ...
Microgravity induces enhanced virulence of both enteropathogenic E .coli and salmonellae. In a separate global approach, two-dimensional gel electrophoresis ...
[104]
OSD-728 - NASA OSDR
Jun 9, 2025 · Longer term SµG culture under glucose-limited conditions led to the accumulation of unique mutations when compared to control cultures, ...
[105]
Space-driven ROS in cells: a hidden danger to astronaut health and ...
Aug 4, 2025 · Space conditions like cosmic radiation and microgravity increase ROS production, causing oxidative stress (Fig. 2). Fig. 2: Reactive Oxygen ...
[106]
Oxidative Stress on the Ground and in the Microgravity Environment
Feb 18, 2025 · In this review, we discuss the mechanisms of OS, the physiological effects on different systems caused by OS in microgravity environment, and potential ...
[107]
Changes in apoptotic microRNA and mRNA expression profiling in ...
Aug 17, 2015 · Radiation and microgravity exposure have been proven to induce abnormal apoptosis in microRNA (miRNA) and mRNA expression, but whether space ...
[108]
Influence of Microgravity on Apoptosis in Cells, Tissues, and Other ...
The study revealed that a short-term mission in space resulted in significant impact in both organs: Altered expression of genes related to T cells (e.g., Il10, ...Missing: flies 2020-2025
[109]
Transcriptomics analysis reveals potential mechanisms underlying ...
Jan 20, 2025 · The dysregulated genes and pathways were mostly involved in energy and oxygen metabolism, immune responses, cell adhesion/migration and cell ...
[110]
APEX-03-1 Advanced Plant Experiments-03-1 Payload - NASA
The first, APEX-03-1, will study microgravity's impact on root development and cell walls of plant seedlings. For this experiment, Arabidopsis thaliana ...
[111]
Microgravity enhances the phenotype of Arabidopsis zigzag-1 and ...
Sep 6, 2022 · Our results indicate that microgravity enhances the zig-1 phenotype by reducing hypocotyl growth and vacuole fusion in some cells.
[112]
Advanced Plant Experiment-07 (APEX-07) - NASA Science
Jun 3, 2021 · APEX-07) examines how changes in gravity and other environmental factors associated with spaceflight affect plants at the level of gene expression.
[113]
Fish Are Having a Real Hard Time in Space - VICE
Jan 15, 2017 · “Under microgravity, there are several changes in the animal body, such as fluid shift, increase in blood pressure, and dizziness,” Akira Kudo, ...
[114]
[PDF] Amphibian development in the virtual absence of gravity
Recent space- flight experiments have successfully fertilized eggs of Xenopus laevis and reared the embryos to the gastrula stage. The morphology of the ...
[115]
Frog Egg Growth - [ Record Viewer ] NLSP
The objective of this experiment was to determine the effects of subgravity on development in a gravity-oriented biological system, by determining the effect of ...
[116]
Collective search by ants in microgravity - Frontiers
An experiment on the International Space Station in January 2014 examined how ants (Tetramorium caespitum) perform collective search in microgravity.Missing: disorganization | Show results with:disorganization
[117]
OS-526 - NASA OSDR
Data showed that Salmonella typhimurium grown in rich LB media in spaceflight displayed increased virulence, biofilm-like formation, and global alterations ...
[118]
Spaceflight and simulated microgravity conditions increase ... - Nature
Feb 4, 2020 · It has been shown that after spaceflight, there are global changes in expression of genes that may potentially be related to virulence and that ...
[119]
Research brief: Astronaut mice reproduce successfully
Jan 28, 2020 · The embryos fathered by mice housed in microgravity and artificial gravity showed developmental patterns comparable to those seen in ground ...
[120]
Microgravity impairs endocrine signaling and reproductive health of ...
May 12, 2025 · In this review, the focus is on how weightlessness disrupts ovarian function and endocrine signaling by affecting the hypothalamic-pituitary-gonadal axis.
[121]
(PDF) Impact of Female Space Travel on Progeny Health
Jun 15, 2025 · This study analyzes behavioral, metabolic, and functional outcomes in F1 and F2 offspring of female mice following a 42-day spaceflight on the ...
[122]
[PDF] STS 107 | NASA
(Biotube-MFA); Closed Equilibrated Biological Aquatic System (CEBAS); Commercial ITA ... This experiment will examine the effect of microgravity on a closed ...<|control11|><|separator|>
[123]
Plant and microbial science and technology as cornerstones to ...
Aug 24, 2023 · Upstream microbial processes in the closed loop of BLSS will likely result in dynamic and non-optimal crop cultivation conditions (nutrient ...Mimicking Nature: Towards An... · The Higher Plant Compartment · Microbe CompartmentMissing: imbalance | Show results with:imbalance<|separator|>
[124]
Microgravity protein crystallization - Nature
Sep 3, 2015 · The experiments, in sum, provided persuasive evidence that growth in microgravity could produce protein crystals of larger size, better ...
[125]
[PDF] N93-22648 ..
... largest volume PCF (500 ml) from STS-37, the space crystals were 10 times bigger than controls while for the smallest volume (50 ml) they were 2 times bigger.Missing: PCG | Show results with:PCG
[126]
A meta-analysis of semiconductor materials fabricated in microgravity
Semiconductor crystals grown in microgravity show improved properties visually, grow larger, display structural improvements, have a more uniform composition ...
[127]
[PDF] Microgravity: - A Tool for Industrial Research
This brochure introduces selected examples of research where microgravity as a tool is relevant for application-oriented and industrial research.
[128]
None
### Summary of ISS FLEX Experiment (Combustion Studies in Microgravity)
[129]
Studying flames in microgravity is helping make combustion on ...
Sep 13, 2019 · This experiment's results could enable the design of flames that are more sooty or soot-free, depending on the need of ...
[130]
3D Printing: Saving Weight and Space at Launch - NASA
Mar 21, 2025 · 3D printing in Zero-G sent the first 3D printer, developed by NASA's Marshall Space Flight Center and Redwire (formerly Made in Space), to the space station in ...
[131]
In Space Manufacturing Market | Global Market Analysis Report - 2035
Sep 19, 2025 · In Space Manufacturing Market was worth USD 6.3 billion in 2025, and is predicted to grow to USD 39.2 billion by 2035, with a CAGR of 20.0%.Missing: derived | Show results with:derived
[132]
[PDF] The Impact of Lower Launch Cost on Space Life Support
Dec 9, 2015 · Space launch costs were very high for decades, typically about $20,000/kg, and it was understood that this high launch cost made it necessary ...
[133]
Drug Development in Microgravity: The Next Frontier in ...
May 27, 2025 · Companies like Merck and Bristol Myers Squibb have used the ISS to advance protein studies, including early work on insulin. Merck, for ...
[134]
Crystallizing Proteins in Space Helping to Identify Potential ... - NASA
Jul 23, 2022 · During the Space Shuttle and Mir programs, researchers discovered that they could produce higher quality protein crystals in microgravity than ...
[135]
Biotech Startup Uses Space to Treat Cancer - ISS National Lab
Jul 23, 2025 · Each chip hosts a biopsy sample—often from solid tumors like colorectal or pancreatic cancer—and grows it into several tiny, biologically ...
[136]
OSD-107 - NASA OSDR
Sep 4, 2024 · Our results confirm PTHrP efficacy as an anabolic agent to prevent microgravity-induced cell death in TOs. Total RNA samples extracted from ...Missing: analogs | Show results with:analogs
[137]
NASA vaccine research in microgravity - Space Center Houston
Mar 22, 2021 · Thanks to NASA, vaccine development is being streamlined as a result of studies being conducted in microgravity onboard the International Space Station (ISS).Missing: antigen 2000s
[138]
SpaceX CRS-21 Mission Overview - ISS National Lab
Nov 17, 2020 · In this project, Sanofi Pasteur seeks to grow MDCK (Madin-Darby Canine Kidney) cell cultures infected with the influenza virus in microgravity ...Missing: flu | Show results with:flu
[139]
CRISPR gene-editing tested in space for first time in DNA damage ...
Jul 2, 2021 · Thanks to low gravity and high radiation, astronauts can experience loss of muscle mass, and increased risks of diabetes, cardiovascular disease ...