One kilometer long spinning space station producing 1G of artificial gravity deployed from a single Falcon Heavy launch vehicle. Credits: Zachary Manchester, graphic by Tzipora Thompson
This year’s NASA Innovative Advance Concepts (NIAC) award winners presented their ideas in a virtual poster session last week. Zachary Manchester of Carnegie Mellon University and Jeffrey Lipton at the University of Washington have come up with a rotating habitat to produce artificial gravity. But to do this without causing severe disorientation that would result from a short radius habitat, their novel facility is one kilometer long spinning to produce 1G at both ends. Manchester and Lipton’s innovation is a deployment mechanism that leverages advances in “mechanical metamaterials” to reduce mass while increasing expansion ratios such that the structure can be squeezed into a single Falcon Heavy payload envelope but when deployed, expands to 150 times its stored configuration size. The structure can be erected autonomously and without any assembly in space.
The key enabling technologies are a combination of “handed shearing auxetics” (HSA) and branched scissor mechanisms. HSA is described in a 2018 paper in Science by Lipton and other researchers where they “…produce both compliant structures that expand while twisting and deployable structures that can rigidly lock.”
“The station can…be spun at 1-2 RPM to generate 1g artificial gravity at its ends while still maintaining a microgravity environment at its center near the spin axis, providing the crew with the flexibility of living in a 1g environment while performing some work in microgravity.”
Rendering of a toroidal space habitat with 12 centrifuges containing gardening units and four composing modules providing an environmental control life support system for a crew of 6. Credits: Thomas Lagarde / International Astronautical Federation
Fully closed environmental control life support systems for long term human space missions are difficult to achieve. But its possible to get closer using a novel approach proposed by Thomas Lagarde in a paper presented at the 69th International Astronautical Congress in Bremen, Germany which took place in October 2018. Using a combination of rotating greenhouses and worm composting units, the system would significantly reduce resupply while producing air and food with equipment that accelerates plant growth while efficiently recycling waste.
Lagarde starts with the inputs and outputs of a crew of six and determines what the surface area required for greenhouses to produce nutritious crops for sustenance and life support. He assumes that inflatable modules like Bigelow Aerospace’s B330 design could be a starting point for the enclosures and then extends the concept to a torus combining the advantages of a solid shell module with that of an inflatable. The greenhouses utilize a rotating garden concept called an “omega garden unit” (OGU) based on an Omega Garden, Inc’s rotary hydroponics system which maximizes crop yield while minimizing space requirements. Growing plants under these conditions, i.e. with artificial gravity, has been shown to activate plant hormones called auxin, thereby increasing their growth rate. The use of an organic light-emitting diode source at the axis of the centrifuge provides a commercially available solution for optimal light exposure while saving space, energy and generating less heat.
To make significant progress toward closure of the life support system recycling loop, human waste and non-edible plant parts become worm food in composting units. This natural process can be accelerated under the right conditions, achieving exponential growth of the worm population but can be self-regulated as described in detail in the paper.
Lagarde sums up the research by saying: “After studying all the different aspects of plant growth and composting, we can conclude that the combination of a rotating garden and processing of organic products by worms will provide enough food and fresh air for a crew of 6 in a minimal space.”
If humanity is to ever move off Earth, clearly we will need to be able to have children wherever we establish long term settlements. But, as humans have evolved over millions of years in Earth’s gravitational field, normal gestation may not be possible on the Moon or Mars. This is probably the most important physiological question to be answered before outposts are permanently occupied on these worlds. We can shield people from radiation, we can recycle wastes and use ISRU to replenish consumables for life support. But we may find that artificial gravity either in free space rotating habitats or on planetary surface settlements is required for settlers to have healthy children. In fact, when I asked Dr. Shawna Pandya, a physician and expert in space medicine about it on The Space Show, she said “…that is the million dollar question”.
Numerous studies have shown the deleterious effects of long term microgravity on human health. So we know that humans will need some level of gravity for sustainable occupation. But what level is enough to stave off the effects of lower gravity on human health and what about reproduction under these conditions? Plus, there is the problem of how to run ethical clinical studies to answer these questions? The Japan Aerospace Exploration Agency (JAXA) has started research in this area by studying mice under variable gravity conditions aboard their Kibo module on the International Space Station using a Multiple Artificial-gravity Research System (MARS). Results of this first ever long term space based mouse habitation study with artificial gravity were published in a paper called Development of new experimental platform ‘MARS’—Multiple Artificial-gravity Research System—to elucidate the impacts of micro/partial gravity on mice in Nature back in 2017. The authors* of the paper found that significant decreases in bone density and muscle mass of the mice reared under microgravity conditions were evident when compared to a cohort raised under 1G indicating that artificial gravity simulating the surface of the Earth may prevent negative health effects of microgravity in space. The next obvious step was to test the mice in 1/6 G simulating conditions on the Moon. This experiment was ran in 2019 but the results have not yet been published. SSP has reached out to JAXA with an inquiry on when we can expect a report. This post will be amended with an update if and when an answer is received.
Reproduction of mice or other mammals has not been studied in space under variable gravity conditions. The problem screams out for a dedicated space based artificial gravity facility such as the Space Studies Institute’s G-Lab and others (e.g. Joe Carroll’s Partial Gravity Test Facility ). Even if such a laboratory existed, how would ethical clinical studies on higher mammal animal models to simulate human physiology during pregnancy be carried out? Answering this question will come first before the million dollar one.
June 2, 2023 Update: JAXA finally released the results of their 2019 study on mice subjected to 1/6 G partial gravity in a paper in Nature in April. There is good news and not-so-good news. The good news is that 1/6 G partial gravity prevents muscle atrophy in mice. The downside is that this level of artificial gravity cannot prevent changes in muscle fiber (myofiber) and gene modification induced by microgravity. There appears to be a threshold between 1/6G and Earth-normal gravity, yet to be determined, for skeletal muscle adaptation.
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* Authors of Development of new experimental platform ‘MARS’—Multiple Artificial-gravity Research System—to elucidate the impacts of micro/partial gravity on mice: Dai Shiba, Hiroyasu Mizuno, Akane Yumoto, Michihiko Shimomura, Hiroe Kobayashi, Hironobu Morita1, Miki Shimbo, Michito Hamada, Takashi Kudo, Masahiro Shinohara, Hiroshi Asahara, Masaki Shirakawa and Satoru Takahash
Cross sectional diagram of hypergravity vehicle with tilted cabin on track in max G orientation. Credits: Gregory Dorais / American Institute of Aeronautics and Astronautics
Gregory Dorais, a research scientist at NASA Ames Research Center, has combined several existing technologies including centrifuges, tilted trains and roller coasters to devise a novel hypergravity space settlement ground-analog that could be used to study the effects of artificial gravity on humans, animals and plants for extended periods. He introduced the concept in a paper presented at the American Institute of Aeronautics and Astronautics Space 2016 Conference in Long Beach, California. Experimental results using such a facility could inform designs for orbital rotating habitats providing up to 1G of artificial gravity or even surface-based outposts on the Moon, Mars or anywhere. The facility could also study higher levels of gravity (thus the name “hypergravity”) which could be beneficial in mitigating deleterious effects of microgravity on human physiology.
Dorais’ Extended-Stay HyperGravity Facility (ESHGF) would merge technologies of centrifuges and trains, creating a 150 meter circular track with a series of connected tilting cars. The tracks could use tubular rails similar to today’s rollercoasters or eventually use magnetic levitation. An optional transfer vehicle placed on an outer concentric track is proposed where people and cargo can be moved between a depot and the hypergravity vehicles while they are in motion so that a constant velocity can be maintained without disruptive force changes during operations.
ESHGF system depicted in a complete ring configuration (not to scale). Credits: Gregory Dorais / American Institute of Aeronautics and AstronauticsHypergravity vehicle single cabin side and perspective views. Credits: Gregory Dorais / American Institute of Aeronautics and Astronautics
The interior of each car could be customized to meet the needs of its inhabitants, but would likely include all the expected functions of a thriving space colony including living quarters, agricultural facilities, marketplaces, recreational centers and much more.
The system is modular and extendable allowing the facility to start small and then expand into a variety of configurations to investigate multiple gravity level environments as sanctioned by budgets. Dorais says that the facility “… will permit research on the long-term health and behavioral effects of various artificial-gravity levels and rotation rates on humans and other life, among other things, to establish the design requirements for long-term space settlements.”
Artist depiction of an O’Neill cylinder from the novel K3+. Credits: Katie Lane (Full distribution rights reserved by Erasmo Acosta)
Erasmo Acosta thinks we might be headed in the wrong direction, that we may be suffering from planetary chauvinism and the better way may be to colonize space with O’Neill cylinders. He makes his case in a post on the Predict section of Medium. SSP has long been a strong proponent of free space O’Neill-type settlements, the advantages of which are numerous, not the least of which is 1G artificial gravity to prevent detrimental human health issues that may arise for occupants of colonies with lower gravity on the Moon or Mars. Such space settlements would house millions of people in perfect 70 degree controlled weather without the threat of natural disasters.
Jeff Bezos has advocated for this philosophy with the aim of moving heavy industry off world and preserving Earth’s environment for “residential zoning”. Recent developments seem to indicate he may be spending more of his time focusing on the realization of that vision.
Acosta, a retired software engineer, feels so strongly that O’Neill cylinders will be the preferred mode of space settlement he wrote a novel called K3+ which depicts a future in the next century where humans will be living in thousands of O’Neill cylinders in a “post-scarcity” civilization of virtually unlimited resources. Acosta envisions Mercury as a source of raw materials:
“The planet’s proximity to the sun, its low gravity, and metal-rich concentration make it the ideal source of raw materials for constructing thousands of O’Neill cylinders.”
In a previous post on Predict, he explains how to kickstart a program for harnessing space resources to fabricate these colonies.
After many years of construction, multiple rings of rotating habitats would eventually encircle the sun harnessing a vast amount of the energy output of our star approaching the configuration of a Dyson sphere.
Artist depiction of multiple rings of rotating habitats around the sun. Credits: Katie Lane (Full distribution rights reserved by Erasmo Acosta)
Finally, as a tribute to the father of free space colonies and an inspiration for a generation of space settlement advocates, I’d like to close out this post with a link to the just released trailer for the much anticipated documentary: The High Frontier, The Untold Story of Gerard K. O’Neill.
ArmorHab transport habitat configured for artificial gravity. Credits: Dark Sea Industries LLC / University of New Mexico / The Mars Society
The innovative ArmorHab mission architecture was presented at the Mars Society Conference in 2016. This novel approach should be considered as part of a strategy for settlement of the Red Planet. The concept integrates several engineering solutions for habitat design to address radiation protection, life support, and transportation while leveraging in situ resource utilization to enhance crew health, safety and reduce costs.
The basic building block of the architecture is a cylindrical Mylar shell wrapped in superconductive tape providing radiation protection through emulation of a magnetosphere. This structure is encased in a protective aerogel for strength and insulation including layers of water ice to further protect the crew from micrometeorites and algae bioreactors for scrubbing carbon dioxide for life support.
ArmorHab wall structure with superconducting tape for radiation protection and algae bioreactors for life support. Credits: Dark Sea Industries LLC / University of New Mexico / The Mars Society
Leveraging Buzz Aldrin’s Mars Cycler invention, the plan starts by building out infrastructure in cislunar space including automated factories on the Moon, then expanding out to Mars with space stations, cycling habitats and connecting “trucks” to provide transport to and from the surface of each destination.
Illustration of cycler model showing six TransportHabs, three space stations and a Mars Truck. Credits: Dark Sea Industries LLC / University of New Mexico / The Mars Society
a) Artistic rendering of a megasatellite constellation of habitats with inclined mirrors for collection of sunlight – detail of individual habitats shown in b). Credits: Pekka Janhunen
Pekka Janhunen of the Finnish Meteorological Institute, Helsinki, Finland has just posted a paper on the arXiv server describing his concept for a megasatellite space settlement in orbit around Ceres and constructed from materials from this dwarf planet in the asteroid belt. Ceres is chosen because of the availability of nitrogen and water needed for life support. A space elevator is proposed as an efficient means of lifting materials off the surface.
Janhunen works out the physics and mass budgets for a collection of settlements comprising the megasatellite, each providing 1g artificial gravity and a closed-loop life support system. The assemblage is made up of a collection of self contained rotating habitats which are interconnected and could potentially grow to house billions of people with 2000 square meters of living area per person. Each habitat would include soil thick enough to enable biomes with trees and ideal weather.
SSP covered another free space settlement concept by this author last April a bit closer to home at L5 in the Earth-Moon system. Janhunen discussed this duel-dumbbell design on The Space Show in May of last year.
Joe Carroll of Tethers Applications, Inc. delivered a presentation on a proposal for a LEO partial gravity test facility at the StarShip Congress which took place in San Diego September 13 – 15. An interesting fact is that of all the surfaces of bodies in the solar system where humans may want to build settlements, all of them have gravity similar to the Moon and Mars. Thus gravity in the solar system is “quantized” to just these two levels simplifying the testing regime. Determining the prescription needed for human health in partial gravity is a critical path research topic needed for space settlement.
