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At least 973 records · Page 54

NASA's Space Launch System: A New Capability for Science and Exploration

The National Aeronautics and Space Administration's (NASA's) Marshall Space Flight Center (MSFC) is directing efforts to build the Space Launch System (SLS), a heavy-lift rocket that will launch the Orion Multi-Purpose Crew Vehicle (MPCV) and other high-priority payloads into deep space. Its evolvable architecture will allow NASA to begin with human missions beyond the Moon and then go on to transport astronauts or robots to distant places such as asteroids and Mars. Developed with the goals of safety, affordability, and sustainability in mind, SLS will start with 10 percent more thrust than the Saturn V rocket that launched astronauts to the Moon 40 years ago. From there it will evolve into the most powerful launch vehicle ever flown, via an upgrade approach that will provide building blocks for future space exploration. This paper will explain how NASA will execute this development within flat budgetary guidelines by using existing engines assets and heritage technology, from the initial 70 metric ton (t) lift capability through a block upgrade approach to an evolved 130-t capability, and will detail the progress that has already been made toward a first launch in 2017. This paper will also explore the requirements needed for human missions to deep-space destinations and for game-changing robotic science missions, and the capability of SLS to meet those requirements and enable those missions, along with the evolution strategy that will increase that capability. The International Space Exploration Coordination Group, representing 12 of the world's space agencies, has worked together to create the Global Exploration Roadmap, which outlines paths towards a human landing on Mars, beginning with capability-demonstrating missions to the Moon or an asteroid. The Roadmap and corresponding NASA research outline the requirements for reference missions for all three destinations. The SLS will offer a robust way to transport international crews and the air, water, food, and equipment they would need for extended trips to asteroids, the Moon, and Mars. SLS also offers substantial capability to support robotic science missions, offering benefits such as improved mass margins and radiation mitigation, and reduced mission durations. The SLS rocket, using significantly higher characteristic energy (C3), can more quickly and effectively take the mission directly to its destination, reducing trip time and cost. As this paper will explain, the SLS is making measurable progress toward becoming a global infrastructure asset for robotic and human scouts of all nations by providing the robust space launch capability to deliver sustainable solutions for advanced exploration.

Crumbly, Christopher M.↗

Recent advancements in the genetic engineering of microalgae

The development of more sustainable food, feed, and bio-products is critical to mitigating the environmental stresses facing our world today. Algae, which includes seaweeds, eukaryotic microalgae, and cyanobacteria, are a promising platform to achieving this, as they have low energy and space requirements, are safe for human and animal consumption, and can be manipulated to produce a diversity of valuable bioproducts. This review focuses on microalgae, both eukaryotic and cyanobacteria. In the past, addressing the major challenges of bringing microalgal production systems to an economically viable scale only had a relatively small genetic toolset to work with, in comparison to other microbial systems such as bacteria and yeast. Expanding the molecular tools available for genetic engineering of microalgae will lead to higher product yields, and accelerate the development of new microalgal bioproducts for commercial applications, thereby supporting the shift towards more environmentally friendly products. In this review, we highlight significant advances from recent years on the design of microalgal expression vectors, discovery of genetic regulatory elements (promoters and transcription factors), optimization of transformation methods, and development of new strain improvement techniques, all aimed at advancing microalgae to become a more efficient biomanufacturing platform. We then discuss how these tools have been applied to improving recombinant protein production, and to enhance metabolic pathway engineering.

09 BIOMASS FUELS↗

The Physical/Chemical Closed-Loop Life Support Research Project

The various elements of the Physical/Chemical Closed-Loop Life Support Research Project (P/C CLLS) are described including both those currently funded and those planned for implementation at ARC and other participating NASA field centers. The plan addresses the entire range of regenerative life support for Space Exploration Initiative mission needs, and focuses initially on achieving technology readiness for the Initial Lunar Outpost by 1995-97. Project elements include water reclamation, air revitalization, solid waste management, thermal and systems control, and systems integration. Current analysis estimates that each occupant of a space habitat will require a total of 32 kg/day of supplies to live and operate comfortably, while an ideal P/C CLLS system capable of 100 percent reclamation of air and water, but excluding recycling of solid wastes or foods, will reduce this requirement to 3.4 kg/day.

Bilardo, Vincent J., Jr.↗

Performance of the Research Animal Holding Facility (RAHF) and General Purpose Work Station (GPWS) and other hardware in the microgravity environment

This paper discusses the performance of the Research Animal Holding Facility (RAHF) and General Purpose Work Station (GPWS) plus other associated hardware during the recent flight of Spacelab Life Sciences 1 (SLS-1). The RAHF was developed to provide proper housing (food, water, temperature control, lighting and waste management) for up to 24 rodents during flights on the Spacelab. The GPWS was designed to contain particulates and toxic chemicals generated during plant and animal handling and dissection/fixation activities during space flights. A history of the hardware development involves as well as the redesign activities prior to the actual flight are discussed.

Hogan, Robert P.↗

Dual Use of Packaging on the Moon: Logistics-2-Living

This paper describes a modular packaging system for logistics that can be reconfigured into internal outfitting for a lunar outpost, including desks, chairs, partitions, cabinets, and radiation shielding. Logistics include clothes, equipment, food, and other consumables needed to sustain the crew for the duration of the mission. A significant mass penalty is required for the packaging and handling of logistics for re-supply of short to long-term space missions that must be brought out of the gravity well on a launch vehicle. Once the supplies have been exhausted, the packaging material is typically of no further use and is discarded. If a scheme can be developed that reuses the logistics packaging, the mass penalty can be reduced. In this research, a modular packaging system has been devised as a kit-of-parts that can be used for both handling logistics supplies, and then reconfigured into desks, chairs, partitions, cabinets, and radiation shielding. The system is derived from a standard International Space Station (ISS)-type Cargo Transfer Bag (CTB), using soft, unfoldable box-like containers with stiff metal inserts. The empty hydrogen-impregnated CTBs can be used as-is for cabinets, opened up for use as partitions, or draped over the habitat as layers of radiation shielding. Stiff metal inserts can be reconfigured into desks and other useful outfitting.

recycle and reuse↗

VEG-04 PICK-AND-EAT CROP PRODUCTION AND HUMAN RESEARCH ON THE INTERNATIONAL SPACE STATION

Growing fresh, nutritious, palatable produce for crew consumption during spaceflight may provide health-promoting, bioavailable nutrients and enhance the astronaut dietary experience as we move toward longer-duration missions. Tending plants may also serve as a countermeasure for crew psychological stresses associated with spaceflight. However, requirements to support consistent growth of a variety of nutritious crops under spaceflight environmental conditions remain unclear. This study explores the potential to grow crops for consumption on the International Space Station (ISS) using the Veggie vegetable-production system. VEG-04A and B were two flight tests conducted in 2019 with the leafy green crop Mizuna mustard. Mizuna was grown in two Veggie chambers simultaneously, with the chambers set to different red-to-blue light formulations; one Veggie was programmed as “red-rich” and the second as “blue-rich.” Light quality is known to impact plant growth, nutrition, microbiology, and organoleptic characteristics on Earth, and the Veggie flight tests examined how these impacts might differ in microgravity. VEG-04A was a 35-day growth test with a single harvest. VEG-04B, a 58-day test with harvests at four, six, and eight weeks from the same plants, assessed sustained productivity. Challenges with the watering program occurred early during VEG-04A, and several plants failed to survive in both the flight and ground control operations. Thus, prior to VEG-04B, an extra test was conducted to tailor water timing and volumes. This test allowed a fine tuning of methods for VEG-04B, and generally plant survival was better in that experiment. At each harvest, the astronauts froze half of the edible plant tissue to return to Earth and weighed the remaining half using the ISS Mass Measurement Device (MMD). Weighed samples were then cleaned with produce-sanitizing wipes, and consenting crew members participated in organoleptic evaluation of the fresh produce. Organoleptic evaluations were conducted on the Mizuna crops grown in both light treatments, and data from these tests are compared to ground data collected at JSC. The remaining sanitized produce was available for crew consumption as desired. Frozen flight samples were returned for microbial and chemical analyses to assess food safety and nutritional quality. Microbial assessments included culturing and identifying aerobic bacteria, yeasts, and molds, and screening for specific human pathogens. Chemical nutrient analyses included assessing elements, antioxidants, and phenolics in plant tissues. Crew members involved in plant operations completed behavioral health surveys pre-flight, in-flight associated with plant growth and harvest activities, and post-flight. Surveys captured the amount of time spent on different plant-related operations, enjoyment of the different activities, engagement with Veggie, experience interacting with Veggie, and sensory stimulation associated with growing plants in Veggie. Within each study, plant growth did not differ across light treatment or location (flight versus ground). In general, more biomass was produced in most treatments during the longer study, but growth of this crop declined over time with the repeated harvests. On average, bacterial and fungal counts were significantly lower on ground control samples than flight samples, and microbial counts increased with repeated harvests. Light treatment did not influence any elements in tissues tested; however, the growth duration did impact levels of several elements. Organoleptic scores were generally higher in flight, and ground tasters considered samples more bitter. Amount of interaction and responses to Veggie varied widely by individual. Enjoyable tasks had higher impact than non-enjoyable tasks and interacting with Veggie was generally viewed as positive. These tests on ISS are helping to mitigate the risk of an inadequate food supply for long-duration missions by adding fresh vegetables and key nutrients to the crew diet, and indicating which plant care activities are providing behavioral health benefits for the crew. This research was co-funded by the Human Research Program and Space Biology (MTL#1075) in the ILSRA 2015 NRA call. Videos due Jan. 25th.

Veggie↗

Nutrition and renal stone disease in space

There is a growing body of evidence from the National Aeronautics and Space Administration and the Russian space program showing that humans exposed to the microgravity environment of space have a greater risk for developing renal stones. Increased bone resorption and the attendant hypercalciuria and hyperphosphaturia contribute significantly to raising the urinary state of saturation with respect to the calcium salts, namely calcium oxalate and calcium phosphate. In addition, other environmental and dietary factors may adversely affect urine composition and increase stone formation risk during space flight. For example, reductions in urinary volume, pH, and citrate contribute to raising stone formation risk. In addition to raising the risk for calcium stone formation, this metabolic profile is conducive to the formation of uric acid stones. Although observations to date have suggested that there may actually be a reduced food intake during the early phase of flight, crew members on longer-duration flights may increase food intake and be at increased risk for stone formation. Taken together, these findings support the use of nutritional recommendations for crew members that would serve to reduce the stone-forming propensity of the urinary environment. Pharmacologic intervention should be directed at raising urinary volumes, diminishing bone losses, and preventing reductions in urinary pH and citrate. Success in reducing the risk for stone formation in astronauts would also be of potential major benefit to the estimated 20 million Americans with nephrolithiasis.

Review↗

Controlled environment agriculture: An opportunity to strengthen interagency research collaboration in the US government

Challenges facing food production and agricultural systems are increasingly interconnected with economic, security, health, and equity issues, among others. Threats such as extreme weather, economic volatility, and shrinking water resources and arable land, influence our ability to maintain a safe and resilient food supply. One promising solution to these threats is controlled environment agriculture (CEA). In many cases, CEA can drastically reduce the amount of water and land used in crop production while increasing productivity. Operations may be established in nearly any environment and harvests can take place year-round, supporting food system resiliency and sustainability. CEA sits at the nexus of a number of disciplines and industries, making it well suited for transdisciplinary and multi-institutional research coordination. Herein, authors from multiple US government agencies present CEA as a case study in improving cross-agency research collaboration. The federal government houses a range of scientific expertise and research capabilities, positioning scientists to lead national and global efforts in transdisciplinary, interagency approaches to complex challenges. Navigating cross-agency collaboration can be a challenge, especially coordinating across different scientific disciplines, geographic locations, and funding mechanisms. To enhance multiagency efforts, collaborators could prioritize (i) organizing personnel and resources, (ii) enhancing existing multiagency collaborations, and (iii) focusing on further opportunities for coordination. Adopting these approaches could enable federal researchers to reinforce and advance academic and industry efforts to address current CEA challenges while solidifying the United States as a leader in this arena.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

NASA Plans for In Situ Resource Utilization (ISRU) Development, Demonstration, and Implementation

The United States (US) National Aeronautics and Space Administration’s (NASA) Artemis Moon to Mars program has four major goals: (1) Returning Americans to the Moon: 1st Woman & 1st Person of Color, (2) Learning to live and work on the Moon, (3) Translating lessons learned so that the United States has capabilities and operational experience for a mission to Mars, and (4) Inspires the next generation of explorers, researchers, scientists, and engineers worldwide. Overarching all of this, the NASA Artemis program also continues to follow Space Policy Directive One (SPD-1) which directs the US to lead an innovative and sustainable exploration program with commercial and international partners. A major objective to achieve the Artemis program goals and SPD-1 is to understand and characterize the resources that exist at these destinations, and to learn how to utilize these resources for sustained human exploration and the commercialization of space. This ability, commonly known as In Situ Resource Utilization (ISRU), involves any hardware or operation that harnesses and utilizes local resources to create products and services for robotic and human explo-ration. The NASA ISRU program is focused on the production of mission consumables and com-modities to enable sustained human exploration, such as rocket propellants, life support consuma-bles, fuel cell reactants, feedstock for manufacturing and construction, and nutrients for food and plant growth. In particular, propellants make up a significant fraction of the mass launched from Earth, are critical to mission success, and can reduce the cost for reusable transportation. Important for enabling long term surface stays, greater independence from Earth, and growing lunar infra-structure are the abilities to perform construction and manufacturing from in situ-derived metals and materials to create and expand on the infrastructure and reduce the logistical resupply needed for sustained surface and space operations. To achieve these ISRU capabilities, NASA, in partner-ship with industry, academia, and international partners has initiated a multi-faceted program which involves (i) Determining Customer Needs (Type and Quantity of Commodities), (ii) supporting ground Development of Hardware and Systems until Ready for Lunar Flight, (iii) utilize Commer-cial Lunar Payload Services (CLPS) flights to fly resource assessment missions with the Science Mission Directorate (SMD), and public-private partnership (PPP) ISRU demonstrations of critical technologies and processes, and (iv) performing commercial-led end-to-end ‘Pilot’ Plant production of commodities and demonstration of usage at a scale and duration that minimizes or eliminates risk for full implementation of ISRU-derived commodities in mission critical applications. This paper will discuss the technologies, mission studies, and accomplishments achieved to date for the ISRU multi-faceted program, and plans for continued ground development and flight missions to reduce the risk of full ISRU implementation.

In situ resource utilization↗

Musing over Microbes in Microgravity: Microbial Physiology Flight Experiment

New York City, the most populated city in the United States, is home to over 8 million humans. This means over 26,000 people per square mile! Imagine, though, what the view would be if you peeked into the world of microscopic organisms. Scientists estimate that a gram of soil may contain up to 1 billion of these microbes, which is as much as the entire human population of China! Scientists also know that the world of microbes is incredibly diverse-possibly 10,000 different species in one gram of soil - more than all the different types of mammals in the world. Microbes fill every niche in the world - from 20 miles below the Earth's surface to 20 miles above, and at temperatures from less than -20 C to hotter than water's boiling point. These organisms are ubiquitous because they can adapt quickly to changing environments, an effective strategy for survival. Although we may not realize it, microbes impact every aspect of our lives. Bacteria and fungi help us break down the food in our bodies, and they help clean the air and water around us. They can also cause the dark, filmy buildup on the shower curtain as well as, more seriously, illness and disease. Since humans and microbes share space on Earth, we can benefit tremendously from a better understanding of the workings and physiology of the microbes. This insight can help prevent any harmful effects on humans, on Earth and in space, as well as reap the benefits they provide. Space flight is a unique environment to study how microbes adapt to changing environmental conditions. To advance ground-based research in the field of microbiology, this STS-107 experiment will investigate how microgravity affects bacteria and fungi. Of particular interest are the growth rates and how they respond to certain antimicrobial substances that will be tested; the same tests will be conducted on Earth at the same times. Comparing the results obtained in flight to those on Earth, we will be able to examine how microgravity induces physiological changes in the microbes.

Schweickart, Randolph↗

Nutrition Requirements, Standards, and Operating Bands for Exploration Missions

The challenge was brought forward in early 2005 to define the nutritional requirements for Exploration missions, and to define the relevant standards and associated operating bands related to nutrition. This document is the result of this charge. An extensive review of existing knowledge was conducted with participation of intramural and extramural experts, and the findings are summarized herein. In short, the approach taken was to define the nutrient intake requirements, that is, the amount of each nutrient expected to be available in the food system. The standards are defined as markers of nutritional status, with optimal (green), sub-optimal (yellow), and critical (red) levels for each. For many of the nutrient requirements, it is not known if they are altered during space flight. Furthermore, in many cases the intake of a nutrient may act as a countermeasure to one or more negative effects of space flight, but these potential countermeasures, too, are not well defined. Thus, we have also documented herein the areas where further research is required. Accordingly, while this document is intended as a comprehensive summary of our knowledge to date, it is expected that this is the first edition of these requirements and standards. As we learn more about space-flight nutrition, and as relationships between disease and nutrients are further defined in Earth-based populations, this document, and the approach to nutrition in the space rogram, will need to be updated accordingly.

Neubek, Deborah J.↗

N 2 Onet: a global collaborative network facilitating advances in measurement, modeling, and mitigation of agricultural soil nitrous oxide emissions

Nitrogen (N) fertilizer supports global food production, but its use and overuse drive emissions of nitrous oxide (N 2 O), a potent and long-lived greenhouse gas. Understanding the drivers of N 2 O fluxes remains elusive, making it difficult to predict emissions in time and space and to develop and evaluate ways to lower emissions through management. Major scientific uncertainties underlying the understanding of the drivers of N 2 O fluxes identified in a workshop of N 2 O emissions experts include poor process-based understanding of controls on soil N 2 O emissions in the field; insufficient data to reduce uncertainty in N 2 O budgets from the field to regional scales, including N 2 O emission measurements and importantly, field-scale N balances; and high uncertainty in model predictions of soil N 2 O emissions across environmental and management conditions. To reduce these uncertainties, we present the concept of N 2 Onet, a global collaborative initiative to accelerate advances in N 2 O measurement, analyses, and mitigation. N 2 Onet will serve as an observational network of supersites with multi-scale measurements; a database hub for N 2 O flux and ancillary data; and a catalyst for community building, information sharing, and training. By coalescing and coordinating the global community of researchers, N 2 Onet will provide a roadmap for reducing N 2 O emissions from agriculture worldwide.

54 ENVIRONMENTAL SCIENCES↗

Effects of Increased CO2 Level on the Well-Being, Growth and Renal Function of Rats

On the Space Shuttle the mean CO2 levels have been 0.3% which is ten times normal air, while there have been extended periods with mean levels of 0.7% and peak concentrations of 2%. On the Space Station the projected mean concentration of CO2 is 0.7% and not to exceed 1.0%. To ensure that high level of CO2 does not compromise the integrity of the science on the Space Station, the effects of chronic exposure to high levels of CO2 were investigated. Following 7 days of cage adaptation animals exposed to 2% CO2 for 30 days were compared to control (ambient air) animals and the effects on the well-being, growth and renal function analyzed. Ten male rats per group were placed in individual metabolic cages which allowed monitoring of daily food and water consumption, as well as feces and urine to be collected. Cages were placed in a plexiglass chamber with internal environment controlled by a computer in conjunction with gas sensors. The elevated CO2 was held constant at 2.0 +/- 0.03% and the O2 at 20.9 +/- 0.15%. Body weight and food and water intake were measured daily for the first ten days of exposure and then every three to four days for the remaining three weeks. Urine was measured for pH, CO2 (as an indicator for bicarbonate) and ammonia (as an indicator for ammonium). During 2% CO2 exposure, animal growth, weight, food and water consumption were within normal ranges suggesting that their well-being was not affected. Urine pH decreased from 7.12 to 6.77 over the first 6 days of exposure and increased the following 24 days returning to pre-exposure levels. Urine NH4+ increased 68% the first 6 days then dropped to and remained at 29% higher than pre-exposure level. Urine bicarbonate concentration did not change the first 6 days, but significantly increased by day 30. These results of chronic exposure to 2% C02 are consistent with renal compensation for respiratory acidosis which may impact science conducted on the Space Shuttle or the Space Station if CO2 levels reach 2%.

Lang, C.↗

Biomass production and nitrogen dynamics in an integrated aquaculture/agriculture system

A combined aquaculture/agriculture system that brings together the three major components of a Controlled Ecological Life Support System (CELSS) - biomass production, biomass processing, and waste recycling - was developed to evaluate ecological processes and hardware requirements necessary to assess the feasibility of and define design criteria for integration into the Kennedy Space Center (KSC) Breadboard Project. The system consists of a 1 square meter plant growth area, a 500 liter fish culture tank, and computerized monitoring and control hardware. Nutrients in the hydrophonic solution were derived from fish metabolites and fish food leachate. In five months of continuous operation, 27.0 kg of lettuce tops, 39.9 kg of roots and biofilm, and 6.6 kg of fish (wet weights) were produced with 12.7 kg of fish food input. Based on dry weights, a biomass conversion index of 0.52 was achieved. A nitrogen budget was derived to determine partitioning of nitrogen within various compartments of the system. Accumulating nitrogen in the hypoponic solution indicated a need to enlarge the plant growth area, potentially increasing the biomass production and improving the biomass conversion index.

Owens, L. P.↗

Life Sciences and Space Research 25 (3): Natural and Artifical Ecosystems; Meeting F4 of the COSPAR Plenary Meeting, 29th, Washington, DC, Aug. 28-Sep. 5, 1992

Bioregenerative life support systems will be an essential part of long duration manned space flight. Studies have been made of various components of these closed ecological systems. these studies have included those spaceborne experiments on Spacelab and Mir, as well as ground-based simulations. The effects of reduced gravity include alterations in food crop and other plant growth and vigor. Systems have also been designed and tested to provide a balanced regenerative system that recycles airborne and other wastes while providing nutrients and other input for future cycles. Hydroponic cultivation must include control of pathogens. All closed systems require sensing and automatic control.

Macelroy, R. D.↗

Integration of Biological, Physical/Chemical and Energy Efficient Systems in the CELSS Antarctic Analog: Performance of Prototype Systems and Issues for Life Support

The Controlled Ecological Life Support System (CELSS) Antarctic Analog Project (CAAP) is a joint endeavor between the National Science Foundation, Office of Polar Programs (NSF-OPP), and the National Aeronautics and Space Administration (NASA). The fundamental objective is to develop, deploy, and operate a testbed of advanced life support technologies at the Amundsen-Scott South Pole Station that enable the objectives of both the NSF and NASA. The functions of food production, water purification, and waste treatment, recycle, and reduction provided by CAAP will improve the quality of life for the South Pole inhabitants, reduce logistics dependence, enhance safety, and minimize environmental impacts associated with human presence on the polar plateau. Because of the analogous technical, scientific, and mission features with Planetary missions, such as a mission to Mars, CAAP provides NASA with a method for validating technologies and overall approaches to supporting humans. Prototype systems for waste treatment, water recycle, resource recovery and crop production are being evaluated in a testbed at Ames Research Center. The combined performance of these biological and physical/chemical systems as an integrated function in support of the human habitat will be discussed. Overall system performance will be emphasized. The effectiveness and efficiency of component technologies will be discussed in the context of energy and mass flow within the system and contribution to achieving a mass and energy conservative system. Critical to the discussion are interfaces with habitat functions outside of the closed-loop life support: the ability of the system to satisfy the life support requirements of the habitat and the ability to define input requirements. The significance of analog functions in relation to future Mars habitats will be discussed.

Bubenheim, David L.↗

Bacteria Provide Cleanup of Oil Spills, Wastewater

Through Small Business Innovation Research (SBIR) contracts with Marshall Space Flight Center, Micro-Bac International Inc., of Round Rock, Texas, developed a phototrophic cell for water purification in space. Inside the cell: millions of photosynthetic bacteria. Micro-Bac proceeded to commercialize the bacterial formulation it developed for the SBIR project. The formulation is now used for the remediation of wastewater systems and waste from livestock farms and food manufacturers. Strains of the SBIR-derived bacteria also feature in microbial solutions that treat environmentally damaging oil spills, such as that resulting from the catastrophic 2010 Deepwater Horizon oil rig explosion in the Gulf of Mexico.

Source record↗

Fibroblast Growth Factor-23 in Bed Rest and Spaceflight

Many nutritional factors influence bone, from the basics of calcium and vitamin D, to factors which influence bone through acid/base balance, including protein, sodium, and more. Fibroblast growth factor 23 (FGF23) is a recently identified factor, secreted from osteocytes, which is involved in classic (albeit complex) feedback loops controlling phosphorus homeostasis through both vitamin D and parathyroid hormone (PTH) (1, 2). As osteocytes are gravity sensing cells, it is important to determine if there are changes in FGF23 during spaceflight. In extreme cases, such as chronic kidney disease, FGF23 levels are highly elevated. FGF23 imbalances, secondary to dietary influences, may contribute to skeletal demineralization and kidney stone risk during spaceflight. Presented with an imbalanced dietary phosphorus to calcium ratio, increased secretion of FGF23 will inhibit renal phosphorus reabsorption, resulting in increased excretion and reduced circulating phosphorus. Increased intake and excretion of phosphorus is associated with increased kidney stone risk in both the terrestrial and microgravity environments. Highly processed foods and carbonated beverages are associated with higher phosphorus content. Ideally, the dietary calcium to phosphorus ratio should be at minimum 1:1. Nutritional requirements for spaceflight suggest that this ratio not be less than 0.67 (3), while the International Space Station (ISS) menu provides 1020 mg Ca and 1856 mg P, for a ratio of 0.55 (3). Subjects in NASA's bed rest studies, by design, have consumed intake ratios much closer to 1.0 (4). FGF23 also has an inhibitory influence on PTH secretion and 1(alpha)-hydroxylase, both of which are required for activating vitamin D with the conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D. Decreased 1,25-dihydroxyvitamin D will result in decreased intestinal phosphorus absorption, and increased urinary phosphorus excretion (via decreased renal reabsorption). Should a decrease in 1,25- dihydroxyvitamin D be necessary to reduce intestinal phosphorus absorption, calcium absorption will also proportionally be reduced, potentially leading to skeletal demineralization. Demineralization of bone can increase kidney stone risk, a medical issue that could prove detrimental to mission success. Given the interrelationships described above, we sought to determine circulating FGF23 concentrations in spaceflight and ground analog studies to better understand the potential effects of dietary phosphorus on bone and calcium metabolism. We analyzed serum from ISS astronauts participating in studies of bone biochemistry, including the Nutrition SMO and Pro K experiments, and we also evaluated FGF23 during extended-duration bed rest. Serum intact FGF23 levels were determined using an ELISA kit from Kainos laboratories in Japan. While initial evaluation of the data showed no changes over time during flight or bed rest, evaluation continues of FGF23 data in light of dietary factors, PTH, vitamin D status, and other biochemical and endocrine factors.

Bokhari, R.↗