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 impression of a sustainable settlement on the Moon. Credits: ESA – CC BY-SA IGO 3.0
Dylan Taylor of Voyager Space Holdings recently wrote an article in The Space Review on sustainable space manufacturing. He makes a convincing case that long-duration space missions and eventual human expansion throughout the solar system will require radical changes in the way we design, manufacture, repair and maintain space assets to ensure longevity. In addition, the cost of lifting materials out of Earth’s deep gravity well will drive sustainable technologies such as additive manufacturing in space and in situ resource utilization to reduce the mass of materials needed to be launched off our planet to support space infrastructure. In-space recycling and reuse technologies will also be needed along with robotic manufacturing, self-reparability and eventually, self-replicating machines.
But there is more to the philosophy of sustainability and its impact on the future of space activities. According to the Secure World Foundation (SWF), sustainability is essential for “Ensuring that all humanity can continue to use outer space for peaceful purposes and socioeconomic benefit now and in the long term. This will require international cooperation, discussion, and agreements designed to ensure that outer space is safe, secure and peaceful.” Much of the discussion centers around the problem of orbital debris, radio frequency interference, and accidental or irresponsible actions by space actors. SWF is active in facilitating dialog among stakeholders and international cooperation.
The National Science and Technology Council released a report in January called the National Orbital Debris Research and Development Plan. To address the issue, there are several companies about to start operations in LEO to deal with the orbital debris or in-orbit servicing. Japan based Astroscale just launched a demonstration mission of their End-of-Life Services by Astroscale (ELSA) platform to prove the technology of capturing and deorbiting satellites that have reached their end of life or other inert orbital debris.
Image of the Astroscales ELSA-d mission showing the larger servicer spacecraft releasing and preparing to dock with a “client” in a series of technical demonstrations, proving the capability to find and dock with defunct satellites and other debris. Credits Astroscale.
Even financial services and investment houses like Morgan Stanley are pushing for sustainability to reduce the risks to potential benefits emerging from the Newspace economy such as remote sensing to support food security, greenhouse gas monitoring, and renewable energy not to mention internet access for billions of people.
Sustainable operations on the Moon are being studied by several groups as the impact of exploration and development of Earth’s natural satellite is considered. Lunar dust when kicked up by rocket exhaust plumes could create hazards to space actor’s assets as well as Apollo heritage sites. SWF, along with For All Moonkind, the Open Lunar Foundation, the MIT Space Exploration Initiative and Arizona State University have teamed up on a project called the Moon Dialogs to advance interdisciplinary lunar policy directions on the mitigation of the lunar dust problem and to shape governance and coordination mechanisms among stakeholders on the lunar surface. SSP’s take on lunar dust mitigation was covered last July.
These few examples just scratch the surface. NASA, ESA and the UN Office for Outer Space Affairs have initiatives to foster sustainability in space. Humanity will need a collaborative approach where public and private stakeholders work together to ensure that the infrastructure to support near term commercial activities in space and eventual space settlement is both durable and self-sustaining.
The long-term sustainability of space. Credits: ESA / UNOOSA
Artist rendering of a Direct Fusion Drive nuclear rocket. Credits: Princeton Satellite Systems
A small New Jersey company called Princeton Fusion Systems (PFS) is close to developing a nuclear rocket using an innovative reactor that could also have applications that are down to Earth. Called the Princeton Field Reversed Configuration (PFRC) reactor, the system is based on over 15 years of research at the Princeton Plasma Physics Laboratory (PPPL), with funding primarily by the U.S. DOE and NASA. PFS, a subsidiary of Princeton Satellite Systems, could have a space based system by the end of this decade which could significantly reduces trip times to the outer solar system and increase payload capability while ensuring a robust power source at the designation. The second iteration of the research reactor, PFRC-2, is currently undergoing testing at PPPL.
Second generation Princeton Field Reversed Configuration (PFRC-2) undergoing testing at Princeton Plasma Physics Laboratory. Credits: Princeton Plasma Physics Laboratory
The PFRC reactor is simple, small and produces very little radiation through the fusion of deuterium and helium-3. This makes it uniquely suited for space-based applications. The field-reversed configuration is a magnetic-field geometry in which a toroidal electric current is induced in a cylindrical plasma by radio frequency (RF) heating. The plasma is confined in a “magnetic bottle” composed of a linear array of coaxial magnets. The design is compact (about the size of a minivan) as compared to some of the more complex fusion devices currently under development such as the ITER donut shaped tokamak. A Princeton Satellite Systems video explains how the PFRC reactor is used in a DFD for space applications by exhausting fusion byproducts out one end of the device through a rocket nozzle:
In May of 2019, Stephanie Thomas, a VP at Princeton Satellite Systems made a presentation at the Future In-Space Operations working group on the DFD technology. Of particular note was the slide on the product development roadmap on technology readiness for flight hardware. If all goes according to plan, fusion could be achieved in the fourth generation research reactor PFRC-4 within 5 years and a flight ready payload could be launched before this decade is out.
DFD notional roadmap to flight. Credits: Stephanie Thomas, Princeton Satellite Systems
Travel time for a 1-2 MW fusion engine and 10,000 Kg payload would be 1 year to Jupiter, 2 years to Saturn and 5 years to Pluto, a significant reduction over chemical rockets using gravity assists. Many other missions to the outer solar system and beyond have been scoped by Princeton Satellite Systems using this technology. In his thesis for a Master Degree in Aerospace Marco Gajeri used the DFD architecture to design a trajectory for a mission to Titan. This blog covered a trip to Saturn using the DFD back in 2019. An interstellar mission to Alpha Centuari has also been considered.
The PFRC reactor has a multitude of clean energy applications on Earth as well:
Illustration of Ablative Arc Mining Process. Credits: Amelia Greig
A NASA NIAC Phase 1 grant has been awarded to Amelia Greig of the University of Texas, El Paso to study an innovative mining technique called ablative arc mining. The process works by using a pair of electrodes to zap surface regolith with an electrical arc thereby ionizing it into its component constituents. The ablated ions are then sorted and collected by subjecting them to an electromagnetic field which separates the material groups by their respective mass. Such a system, when mounted on a mobile rover, could extract both water and metal ions in the same system.
The goal of the this grant is to identify a feasible ablative arc mining scheme for ISRU on upcoming lunar exploration sorties. The study will define the design of an ablative arc and electromagnetic transport system for extraction and collection of water, silicon, and nickel. The architecture should have an output of 10,000 kg/yr of water for use by lunar outposts or other operations. Finally, a trade study will be performed comparing the efficiency of the proposed concept against other ISRU processes such as microwave or direct solar heating which are designed to only collect a single constituent.
We’ll need ISRU methodologies to enable long-term space settlement on the Moon, Mars, in the Asteroid Belt or to support free space habitats. The ablative arc mining architecture may be an efficient alternative for extraction and collection of multiple volatile constituents in a single system when compared to methods that collect only one material at a time.
Image of Biosphere 2, a research facility to support the development of computer models that simulate the biological, physical and chemical processes to predict ecosystem response to environmental change. Credits: Biosphere 2 / University of Arizona
Once cheap access to space is realized, probably the most important technological challenge for permanent space settlements behind radiation protection and artificial gravity is a robust environmental control and life support system (ECLSS). Such a system needs to be reliably stable over long duration space missions, and eventually will need to demonstrate closure for permanent outposts on the Moon, Mars or in free space. In his thesis for a Master of Science Degree in Space Studies, Curt Holmer defines the stability of the complex web of interactions between biological, physical and chemical processes in an ECLSS and examines the early warning signs of critical transitions between systems so that appropriate mitigations can be taken before catastrophic failure occurs.
Holmer mathematically modeled the stability of an ECLSS as it is linked to the degree of closure and the complexity of the ecosystem and then validated it against actual results as demonstrated by NASA’s Lunar-Mars Life Support Test Project (LMLSTP), the first autonomous ECLSS chamber study designed by NASA to evaluate regenerative life support systems with human crews. The research concluded that current computer simulations are now capable of modeling real world experiments while duplicating actual results, but refinement of the models is key for continuous iteration and innovation of designs of ECLSS toward safe and permanent space habitats.
This research will be critical for establishing space settlements especially with respect to how much consumables are needed as “buffers” in a closed, or semi-closed life support system, when the model’s metrics indicate they are needed to mitigate instabilities. Such instabilities were encountered during the first test runs of Biosphere 2 in the early 1990s.
As SpaceX races to build a colony on Mars, they will need this type of tool to help plan the life support system. Holmer believes that completely closed life support systems for relatively large long term settlements are at least 15 to 20 years away. That means that SpaceX will need to resupply materials and consumables due to losses in their initial outpost who’s life support system in all probability will not be completely closed during the early phases of the project over the next decade. Even SpaceX cannot reduce launch costs low enough to make long term resupply economically viable. They will eventually want to drive toward a fully self sustaining ECLSS. That said, depending on how the company funds its initiatives and sets up it’s supply chains, they may not need a completely closed system for quite some time.
Of course there are sources of many of the consumables on Mars that could support a colony but not all the elements critical for ecosystems, such as nitrogen, are abundant there. There are sources of some consumables outside the Earth’s gravity well which could lower transportation costs and extend the timeline needed for complete closure. SSP covered the SHEPHERD asteroid retrieval concept in which icy planetesimals, some containing nitrogen and other volatiles needed for life support, could be harvested from the asteroid belt and transported to Mars as a supply of consumables for surface operations. TransAstra Corporation is already working on their Asteroid Provided In-situ Supplies family of flight systems that could help build the infrastructure needed for this element of the ecosystem. It may be a race between development of the competing technologies of a self-sustaining ECLSS vs. practical asteroid mining. The bigger question is if humans can thrive long term on the surface of Mars under .38G gravity. In the next century, O’Neill type colonies, perhaps near a rich source of nitrogen such as Ceres, may be the answer to where safe, long term space settlements with robust ECLSS habitats under 1G will be located.
Curt Holmer appeared recently on the The Space Show discussing his research. I called the show and asked if he had used his modeling to analyze the stability of ecosystems sized for an O’Neill-type colony. He said he had only studied habitats up to the size of the International Space Station, but that it was theoretically possible to analyze this larger ecosystem. He said he would like to pursue further studies of this nature in the future.
Artist’s depiction of propulsion concept using Directed Energy. At left, Directed Energy Launch Technology Array (DELTA) beams power to laser powered electrical propulsion (LEP) spacecraft for rapid travel to the outer solar system or for laser sailing to the stars. At right, a sub-module from a close packed array of laser emitters within DELTA. Credits: Todd F. Sheerin / International Astronautical Federation
A concept for fast transit to the outer solar system and beyond has just been published by Todd F. Sheerin et al.* in Acta Astronautica. Since the article is behind a paywall, SSP has obtained permission by one of the coauthors, Professor Philip Lubin at the University of California, Santa Barbara to link to an earlier version of the paper presented at the 70th International Astronautical Congress held in Washington D.C. back in October 2019. Professor Lubin is Director of the Experimental Cosmology Laboratory at UCSB where he oversees research on several interesting directed energy projects.
The concept makes use of an Earth-based Directed Energy Launch Technology Array (DELTA) to beam laser energy to photovoltaic cells on an electric propulsion vehicle for travel within the solar system, or for photon reflection via a laser sail on gram-scale spacecraft accelerated to relativistic speeds for interstellar missions. In the former case, this method leverages existing solar electric propulsion technology which converts optical energy to propulsive jet power like what was used on NASA’s Dawn mission. An existing NASA Innovative Advanced Concepts (NIAC) program at UCSB has demonstrated proof of concept for elements of the array.
The DELTA architecture development can be terraced in progressive stages starting with small one meter arrays building up to large 10 km systems. The concept could support a range of missions, from swarms of gram-scale robots all the way up to human-rated spacecraft greater than 100 tons.
The authors believe this approach “… enables a scalable, cost effective roadmap to rapid solar system transportation for robotic and human missions alike, including robotic and human Mars-in-a-Month missions, with transit times of 30 days, as well as the first robotic relativistic interstellar flight within our lifetime.”
* Authors: Todd F. Sheerin, Elaine Petro, Kelley Winters, Paulo Lozano, Philip Lubin
Illustration of a nuclear thermal rocket in low earth orbit. Credits: NASA
Two U.S. companies are partnering with NASA to develop new fuel sources and reactor designs for future nuclear-fueled crewed space missions. Nuclear thermal and fusion powered rockets could significantly reduce the travel time to the Red Planet, lowering the risk of radiation exposure and the cost of life support consumables.
In an article in IEEE Spectrum, freelance journalist Prachi Patel describes the challenges of designing space nuclear reactors that are safe and lightweight, which will be needed to propel exploratory missions to Mars. These type of space reactors have the added benefit of being able to switch from propulsion to a power source at their destination.
Seattle based Ultra Safe Nuclear Corporation has a reactor design that uses a grade of nuclear fuel enriched to less then 20% uranium classifying it below the limit of highly enriched uranium, thus reducing proliferation risks by nefarious actors. The company coats its microscopic uranium fuel pellets with ceramics in a zirconium carbide matrix. This design approach ensures that the fuel can withstand the extremely high temperatures and volatile conditions inside a nuclear thermal reactor.
BWX Technologies Corporation located in Lynchburg, Virginia has extensive space nuclear reactor experience and has been working under contract to NASA since 2017 to explore designs also using a temperature resistant ceramic composite fuel with low enriched (< 20%) uranium.
Both companies may benefit from the recent Trump Administration Space Policy Directive-6 released December 16 which aims to limit the use of highly enriched uranium in space nuclear reactors unless absolutely necessary. The Memorandum on the National Strategy for Space Nuclear Power and Propulsion specifies that “The use of highly enriched uranium (HEU) in SNPP [space nuclear power and propulsion] systems should be limited to applications for which the mission would not be viable with other nuclear fuels or non‑nuclear power sources.” Although Space Policy Directives can be negated or modified by new administrations this particular directive should have bipartisan appeal.
The article also mentions the Princeton Plasma Physics Laboratory’s Direct Fusion Drive that SSP covered last year. Fusion rockets, although further behind in technology readiness levels, hold promise to outperform fission-based propulsion as fusion reactions release up to four times as much energy.
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Space is Open for Business by Robert Jacobson is a must-read for all potential “astropreneurs” (entrepreneurs involved the NewSpace economy), space advocates, investors or anyone who wants to keep current on space commerce and its impact on the future of humanity. This book is a refreshingly positive view of our future in space, a welcome alternative outlook in stark contrast to many dystopian and negative predictions of where we’re headed in today’s media.
Jacobson covers all aspects of the nascent space economy which has already begun to grow in leaps and bounds, and is headed for explosive growth in the near future. No stone is left unturned by his deep research of all aspects of space commerce, with scores of interviews of executives from both established and small startup space companies.
I especially liked the Sci-Fi and Society chapter in which Jacobson talks about science fiction “illuminating the possibility of the space frontier”. Much of what is now happening in space was predicted in science fiction in the last century. Many CEOs and executives of NewSpace companies were inspired to pursue careers in science or engineering through science fiction books, televisions shows and movies.
Eventually, humanity will evolve to migrate off Earth and establish space settlements throughout the solar system and eventually among the stars. Development of the technologies and commercial activities for space settlement have the potential to create vast wealth, bring billions of people out of poverty and preserve Earth’s natural environment. Jacobson has provided a hopeful glimpse of how the space businesses supporting this effort will manifest this destiny.
ESA astronaut Luca Parmitano loads microbes into the Kubik centrifuge facility on the International Space Station. Credits: ESA
A research team at the University of Edinburgh in the UK has just published an analysis of data from an experiment on the International Space Station that could lead to “biomining” on Mars or an asteroid. Published in Nature Communications on November 10, Cockell, C.S., Santomartino, R., Finster, K. et al.* present experimental results demonstrating microbiological leaching of rare Earth elements from basalt rock, an analogue for much of the regolith material on the Moon and Mars. Called BioRock, the ESA sponsored experiment examined three species of microorganisms under variable gravity conditions in the Kubik centrifuge facility located in Europe’s Columbus module on the ISS.
This technology is a significant breakthrough for in situ resource utilization. By “living off the land” on the Moon, Mars or an asteroid, space settlers could have an available source of valuable materials used in electronic devices and many other high-technology applications. These rare Earth elements and the traditional heavy mining equipment needed to extract them would not have to be launched from Earth, significantly reducing transportation and processing costs. Positive results were found under Earth gravity, Mars gravity and microgravity conditions. The authors conclude that the experiment “…shows the efficacy of microbe–mineral interactions for advancing the establishment of a self-sustaining permanent human presence beyond the Earth and the technical means to do that.”
