New in the NSS Space Settlement Journal is the article Gravitat: Proposal for a Standard Design Vessel for Space Settlement, by Dr. Pietro Calogero.
Abstract
In this paper I propose a “gravitat” as a two-pod vessel rotating around a central truss. I argue that a standard vessel design can serve multiple roles for extended crewed missions: as a vehicle, as an orbiting station, and as a surface base mounted on low-gravity planetary bodies. These roles share substantially overlapping design constraints: low total mass for both delta-V and station-keeping; spin-gravity for crew health and simplification of system design; and a nearly-closed environmental life-support system with significant fault-tolerance. Furthermore, a common design enables the most rapid accumulation of field-test time to identify strengths, weaknesses, and overall risk management of a complex vessel.
The proposed design includes two pods enclosed in three concentric fabric envelopes, tethered to a central truss by cables arranged to minimize oscillation. The pods consist of internal trusses, parallel to the axis of rotation, that support their dwelling decks and multiple garden shelves. The structural design is deliberately simple, to maximize reliability and durability. Complexity emerges in the details of long-term life-support, which requires years of empirical testing and observation to enable actual settlement of space.
Dear Dr. Pietro Calogero;
What are your views / opinions on small radius spin-gravity habitats? Specifically a 4 meter radius habitat spinning at approximately 16 RPM. My opinion is that the inner ear can tolerate spin rates as high as 23 RPM (in space) with little, or no ill effects. Experiments conducted on Earth have 3 forces acting on the Vestibular system. Gravity, Centripetal, and Coriolis. In space only 2 forces act on the Vestibular system. Centripetal, and Coriolis. This difference has caused much confusion in the pursuit of building spin-gravity habitats. SpaceX Starship has a diameter of 9 meters, and could potentially have a spin-gravity habitat of 4 meters radius constructed in it. A small radius spin-habitat would greatly accelerate humans ability to explore the solar system on long duration space flights (years). An ultra light weight experiment using hammocks, swings, or similar constructions would allow fast testing and development of small radius spin-gravity habitats. Also precession is problem with spinning habitats. Two counter-rotating coupled spin-habitat should cancel out the torques that cause precession. i believe the Balancing of passengers movements within the habitats would also need to be compensated for. I have done some simple designs dividing a cylindrical habitat into cabins with the gravity gradients calculated by a program called “SpinCalc”. 8 or 9 cabins seems workable with some cabins allocated for life support. Blunted pie wedges seem to be the logical layout of the cabins. An open central hub would allow access to the rest of the ship which would be in zero-g. The hatch could be located in the ceiling (the blunted point of the pie wedge). If the ceiling is made semi-transparent the lighting in the hub could be used to set circadian rhythms for the crew, and passengers. On a spacecraft like SpaceX Starship, planetary landings would make it necessary to reconfigure the spin-hab cabins. One of the end walls would become the floor as the direction of gravity would change. This would be significant in design considerations, only if the spacecraft is to be used as a base of operations for long periods on planetary surfaces. The problems caused to human health by micro-gravity can be overcome by spin-gravity habitats. I have spent several years meditating on this idea and would greatly enjoy some correspondence on the subject, and possible design solutions.
Sincerely yours,
Geoff S Jones
Bennington VT
Dear Geoff, I am sorry that I was not notified of comments on my paper. I just returned to check it and found your thoughtful comment! Several major unknowns persist with spin-gravity: (1) What is the minimum radius at which trained passengers (not the general public) can adapt without vertigo? (2) What is the minimum effective g-force that people and other elements in the system need in order to stay healthy for extended periods of time? Smaller radii and lower fractions of 1g would make the engineering easier, agreed. If the minimum acceptable radius is within the diameter of a SpaceX vessel or an inflated hab, that would be easiest. From the research I found, that has not yet been demonstrated.
Therefore, the least-mass way of testing out options would be to sling the pods out on cables, and do extended tests first in LEO. Major changes to radius in a two-pod configuration only require additions of lengths of cable. There are so many variables in both humans and semi-closed life-support systems, that I think these can only be tested empirically in the field. Once we have a ‘good enough’ configuration with a lowest feasible mass, we can propel it on an extended voyage, rather than wait for the results of a ten or twenty-year full test. Mainly I think we need to start doing a lot of spin-gravity testing in LEO before we can be confident about what works best.
Other design possibilities:
Dear Doctor Calogero;
Some design ideas I have had are, locating the bearings at the outer rim of a cylinder, or toroid, spin-hab, not the hub, (this is a much more robust way to support the structure while spinning). A pressurized (bearings can’t keep air on one side, and vacuum on the other without leaking) outer hull enclosing two counter rotating spin-habs. (this cancels torques, and should eliminate precession). Electromagnetically spin-up, spin-down the habs. Two counter rotating habs eliminate the need of thrusters, and the finite propellant that they use. A plastic bag surrounding the ship containing liquid water at a thickness of from 1-3 meters, as radiation shielding (this much water is prohibitively heavy, and would be best for stationary spin-habs). Electromagnetic shielding ( https://earthweb.ess.washington.edu/space/propulsion.html ) may be the lowest weight option for traveling spin-habs. Effective electromagnetic radiation shielding may require large amounts of electricity, Aluminum instead of copper as a conductor / inductor?
Some amenities:
A hammock for sleeping, storage of items. Hammocks are very popular on ocean going ships. They stow easily, are ultra light weight, can be fabricated out of many materials, repair easily, can be reconfigured easily to different positions / locations, are auto-leveling to gravity, could possibly be used for sleeping in zero-g. https://en.wikipedia.org/wiki/Hammock Sleep helps cure depression on a long voyage…
The chamber-pot, or loo;
Can easily be made water tight, handy if you “end up” in zero-g (pun intended). A loo is easy to move, fabricate, clean, usable to transport urine, and fecal material (poop) to hydroponics, and chemical factory, for fertilizer, dynamite etc. You would not believe the chemicals that come from poop, and pee. Samples for the ship’s Microbiologist to study the microbial biome. You would not believe the number of microbes that live in your gut, that we can’t live with out, and that they control human health to a great degree. A Loo is absolutely necessary, to cure depression on a long voyage…
Kitchen;
Sink, mini-fridge /freezer, microwave oven, toaster oven, hot plate, tea / coffee pot, bread maker, etc. Cooking is the best way to cure depression on a long voyage…
Small garden;
Hydroponic, salad maker, lettuce, tomato, herbs, bonsai (fruit, and nut trees), medicinal plants, plants for industrial use Bamboo, Hemp. green plants, bright light, maintain circadian rhythms, to help reduce depression on long voyages…
Gymnasium:
Treadmill, bike, rower, stepper, bowflex. Free weights are a bad idea. Ever see what a box of klenex can do to someone’s head in a car crash? An combination Endless pool / Jacuzzi tub (a water treadmill for swimming), to cure depression on long voyages…
Other thoughts:
Testing smaller ultra-lightweight versions of spin-habs will be cheaper, easier to make changes to, and can (potentially) be built completely on earth, eliminating space walks, and their added risk. If small radius spin-habs (4 meters at 16 RPM) are proven to work well; Small radius spin-habs will accelerate the pace of human expansion into the solar system.
Personally I think NASA should start experimenting in LEO with a used SpaceX Dragon 2 capsule, performing rolls at a few RPM, then increase the RPM when proven safe. Or two Dragon 2 capsules tethered nose to nose, and spun. With a winch, as you stated in your paper, you could shorten the radius at will, and increase the spin rate; like a figure skater pulling her arms in during a spin. These tests using Dragon 2, could quickly prove if short radius spin-habs are a workable solution for the future of space development.
Thanks for listening, and helping to cure depression on long voyages… Ha,ha,ha…;-)
Geoff S Jones
Bennington VT
Here is a copy of a letter I Sent to Techshot the makers of the MVP centrifuge now on the ISS. Maybe this will start a conversation or two.
https://techshot.com/aerospace/technology/mvp/
https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1777
https://www.youtube.com/watch?v=2AVvglUaa2g
Dear Mr. Boling,
Do you have a way of measuring the torques the MVP centrifuge produces? Do the Carousels rotate in opposite directions to eliminate torques, and precession? Have you calibrated the carousels in zero-g to see how well the torques, and precession can be eliminated?
It is my understanding that two (balanced, equal mass) counter rotating fly wheels if coupled will cancel each others torques, and eliminate precession. These properties are very valuable in a spin-gravity space habitat. If you can use the centrifuges to push against each other to spin-up, spin-down, and maintain constant rotation speeds, you will not need thrusters to perform these operations. Using electricity (instead of reaction mass) to start, maintain, and stop rotation is a huge advantage during long duration, deep space missions. Zero torques also means that the ship containing “Spin-Habs” can change position just as a ship with now torques acting on it would, like current space craft. A spinning craft could not anchor itself to an asteroid, or comet without risk of damage; a stationary outer hull surrounding a “Spin-Hab” could easily anchor to an asteroid, or comet with little risk of damage
I am interest in designing a Spin-Habitat similar to the Techshot MVP centrifuge. Two 4 meter radius, counter rotating wheels within a pressurized cylindrical outer hull, probably surrounded by 1 meter of water as a radiation shield. as much as 3 meters of water may be necessary to eliminate cosmic radiation ( gamma ray) hazards. Buzz Aldrins “Cycler” ship may work best for this design as it would be extremely massive with all that water. Cyclers only need to be accelerated once at the start of their orbit. After launch of a Cycler the gravity of the earth, and Mars maintain their orbit. Cycler ships don’t go into orbit around each planet. Cyclers orbit the sun, and their orbit crosses the Earth, and Mars orbit near each planet. The Cycler orbit allows “Taxis” from the Earth, Mars, Moon, (asteroids?) to rendezvous with the Cycler ship then passengers, and crew transfer to the Cycler for the journey, The taxi can go along for the ride, and be used to rendezvous with the target destination. This reduces the mass of the transfer craft to a very large degree.
Thanks considering this letter, and any answers you can give.
Links to to other research centers working on Centrifuge generated artificial gravity would be of great help also.
Ad Astra
Sincerely,
Geoff S Jones
Bennington VT