Space exploration will lead to space migration and eventually space exodus.  The lifespan of our planet is limited and dependent on the life of the Sun.  There have been approximate calculations made of for how long would the Sun last before it burns all its hydrogen.  Yet, long before this will happen, the Earth will probably be destroyed by some other natural cataclysm.  As a most positive effect, the freedom of expanding human society into space will allow the earth to recover its natural glory.  Present activities that pose a threat to people and nature, such as hazardous industries, could be moved to earth-orbiting stations and to the moon. A realistic artificial gravity could be created by centripetal forces generated by spinning a space station on a large radius circle.

Architectural Framework for a future International Space Station 2

The development of a space habitat is a long trial process that should include extensive experimentation and testing of the various components.  Following is a proposal for an architectural framework for a pilot space station, with the following objectives:

Creating and Evaluating Artificial Gravity (AG)

Functional Flexibility of components

Expandability

Experimental Manufacturing in space

Economically and technically feasible in the near future

The main objective is to develop the infrastructure in space for evaluating the long-term effects of Artificial Gravity on human health and functioning.  AG could be created through centripetal forces generated by spinning the living quarters on a 50m radius circle.  The revolving velocity will be one of the parameters subject to experimentation.

The ISS2 will be composed of 2 main assemblies.  The Rotating Assembly (RAS) will be revolving around an axle that is the centre of the Stem Modules (SM).   The Static Assembly (SAS) will remain fixed around the same axle and will be connected to the RAS through the Motion Switch Hub (MS).  The MS will have a special core developed to allow communication between the two assemblies without having to stop the RAS.

The RAS will have 3 Space Habitat modules (SH).  They will be kept in a stable equilateral triangle configuration by 3 sets of Spoke Modules (SP), a central Habitat Hub (HH) with Stem Modules (SM) and tension cables (C).  Between each SH and the peripheral SP, there will be a Propulsion for AG module (PA), which will provide the forces for inducing and breaking rotation.  The Radius could be increased by adding SPs to the 3 spokes.

The SAS will be used for Research and Manufacturing in Weightlessness, and will provide the means to achieve the economic viability of ISS2, through joint ventures with the private sector.  The Manufacturing Modules (M) will form hexagonal clusters of 6 units, attached to Manufacturing Hubs (MH) and SMs.  The Static Assembly (SAS) will also incorporate Docking Modules (D), Fuel units (F) and Solar Arrays (S).  The D, F and PD units at the end of SAS can be moved by a Space Tug (ST) to allow the insertion of an HM and M units, for expansion.

The Central Command module (CC) will have its own D, F and Propulsion for Direction (PD), and will be able to move from the top of the RAS to other docking modules.  The PDs will also control the positioning of ISS2.  The SPs and SMs will be cylindrical, with a central circulation tunnel and air locks at both ends.  The spoke and stem modules will have a circular cross section with a core circular tube for circulation.

3STAR, a Pilot Space Habitat 

Several designs for space habitats have been proposed in the last century, such as the Stanford torus (1 mile diameter donut-shaped), the Bernal sphere (16 Km diameter), the O'Neill cylinder (3 Km radius), and combinations of them.  In essence, they all create artificial gravity with centripetal force produced by spinning the entire space station. Unfortunately, they have the disadvantage of being very large and inflexible, in the sense that they could not serve their purpose before being fully completed.  This poses tremendous economic and technological difficulties.

3STAR is a relatively small-scale space prototype that could be technically and economically feasible in the near future.  Any earth-orbiting space habitat could be developed in stages, using the present International Space Station as a platform.  This will make good use of the great achievements of ISS and would ensure continuity in space exploration.

Having the flexibility of conducting multi-disciplinary research is crucial for any such prototype.   3STAR would provide independent modules for facilitating parallel experiments in various scientific fields, permaculture, energy self-sufficiency, simulated gravity, space architecture, low and near-zero gravity manufacturing, etc.  3STAR provides this opportunity thanks to its configuration that not only allows development in stages, but also invites expansion.

In the near future, 3STAR could provide a platform for travel to Mars and other planets and for establishing a lunar base, avoiding Earth’s gravity.  Its telescope could observe the universe better than anything that could ever be built on Earth.  Furthermore, a next generation 3STAR could become self-sufficient in time, able to break away from its earthly cradle and could begin the human space odyssey.

There is also tremendous potential for incorporating commercial components, which would attract private investment and make the entire endeavor economically viable.  Tourism, lunar mining, production of rare metals and new compounds, low-gravity manufacturing, are examples of activities that would attract private enterprise.

3STAR, as the name implies, resembles a three-pointed star forming an equilateral triangle.  This type of triangle is a “ground state” geometry providing optimal stability and equilibrium.  When completed, 3STAR would have three geodesic spheres, one at each point, revolving in perfect balance in a circular trajectory around the central hub, interconnected with cylindrical stems and stabilized by an array of cables.

The author has named the geodesic sphere BUCKYGLOBE, in memory of Richard Buckminster Fuller, one of the greatest geniuses that ever lived.  Due to the large radius required, the stems (including spokes) will have intermediate nodes and tension cables.  As a result, the entire complex will resemble a giant spider net.

The illustrations indicate a circular trajectory with a diameter of 1000m, yet the required minimum radius and velocity that the spheres will have to spin in order to simulate a gravity sufficiently close to 1g (9.81 meters per second per second) will have to be calculated based on mathematical formulas for centripetal force and acceleration, derived from Newton’s laws.

As the mass of the components located near the centre of the complex, mainly the Hub, will gradually increase with the addition of various building materials, equipment, furnishing, etc., the rotation velocity can decrease, requiring less energy.

If an object is traveling in a circle with a varying speed, its acceleration can be divided into two components, a radial acceleration (the centripetal acceleration that changes the direction of the velocity) and a tangential acceleration that changes the magnitude of the velocity.

Other products of artificial gravity that affect human comfort also need to be addressed; such are centripetal acceleration, head-to-foot gravity gradient, angular velocity (max. 6 rotations per minute, but max. 2 for optimal comfort), tangential velocity (minimum 6m, but ideally 10m per second), cross-coupled head rotations and the Coriolis effects.

By Newton's second law of motion, a physical force F_c must be applied to a mass to produce this acceleration. The direction of the force is inwards, towards the center of the circle and opposite to the direction of the radius vector. If the applied force is less or more than F_c, the object will "slip outwards" or "slip inwards", moving on a larger or smaller circle, respectively.

Following are quotations from "Artificial Gravity and the Architecture of Orbital Habitats" by Theodore Hall, Proceedings of 1st International Symposium on Space Tourism, Daimler-Chrysler Aerospace GmbH., 20 March 1997:

“…comfort in artificial gravity depends as well on other aspects of environmental design, beyond the basic rotational parameters…“Only the global centripetal acceleration represents "design gravity". The other components are gravitational distortions that arise from motion within the environment. They affect the magnitude and direction of the total acceleration, causing changes in the apparent weight of objects and the apparent slope of surfaces. Taking Earth as the norm, one's experience of gravity should be independent of one's motion. Hence, the goal is to design the environment such that the global centripetal acceleration yields some preferred level of artificial gravity while the other components. The equations suggest that the angular velocity should be kept low and that the radius should be large.”

ECOSYSTEM

The goal is to create an ecosystem that will gradually become self-reliant and independent.   The supply of all essentials, namely air, water, food and energy, would gradually shift from being imported from Earth, to being produced in the space habitat and reproduced in closed natural cycles.

At the beginning, an artificial atmosphere will have to be created with Oxygen brought from Earth.  When the Moon will become a source of raw materials, Oxygen can be extracted from lunar ice and other minerals, together with many other elements used in manufacturing.

In time, plant life shall generate most of the Oxygen required for maintaining a high air quality.  The amount of CO2, essential for plant growth, will have to be monitored to maintain a healthy balance of gases in the air.

Water can be a by-product of power cells that produce energy from burning Hydrogen and will also be part of an artificially created natural cycle.  Rain can be produced from the condensation of water vapor in contact with the outer cold surface of the Buckyglobe.  For growing food, permaculture principles will be applied.

Permaculture is both a philosophy or lifestyle ethic as well as a design system that utilizes a systems thinking approach to create sustainable human habitats by analyzing and duplicating nature's patterns (ecology).

3STAR will incorporate a vast energy system, collecting solar energy and converting it back and forth between chemical, kinetic and electromagnetic forms, with Hydrogen as the main storage agent.  As a result, the energy system will have a symbiotic relationship with the air, the water and food production.

3STAR has five main functional elements:  the BUCKYGLOBE, the HUB, the STEM, the ROBCON and the WEB.

BUCKYGLOBE

Each Buckyglobe will enclose an independent ecosystem.   The three-dimensional space structure, made of tubular elements, will support a double layer (or skin) to protect the micro-atmosphere created inside.  The main function of the outer layer will be to provide a radiation shield with retractable insulated panels, which will regulate the sunlight penetrating through the transparent panels.  Some of the geodesic segments could have solar panels inserted; others incorporate adjustable shutters for regulating and screening the entire spectrum of solar radiation.

The inner layer will provide an air & vapor barrier.  Depending on the locations facing the various interior components, some portions will be transparent to provide sunlight and visibility; others will be designed to support artificial soil for farming, animal shelters, and other permaculture buildings.

The space between the two layers may be used to accommodate fuel cells, batteries, oxygen and hydrogen storage and other equipment.  Here, the temperature will have to be maintained within limits acceptable to such equipment, not for humans.  Therefore, maintenance work in this space will require protective suits and oxygen masks, but not necessarily space suits.

The axis of the Buckyglobe will be developed into the Stem, with a Spoke in its centre.  The Stem accommodates all circulation (staircase and elevator), a power train (or electromagnetic catapult) and various service conduits and cables.   It also has a docking module and thrust rockets at the end.

A special computer will regulate the acceleration and deceleration required to maintain a constant gravity level in the Buckyglobe.

The neighboring Buckyglobes will be visible up in the sky.   The Hub can also be seen over the head.  The overwhelming image of the Earth will be present everywhere.  This will be psychologically reassuring.  The Hub will appear like a second sun, radiating solar rays and contributing to natural light.   

The curvature resulting from the 500m revolution radius translates into a slope of 2.60%. To simplify construction, the floor structure may be designed with straight structural elements and creating stepped levels as required, introducing stairs and ramps for communication between levels.  The largest storey is 26m wide; this would require a total stepping of approximately 675mm.  If the floor needs to be curved for improved comfort, this can be achieved with a light concrete topping which can add thermal mass for energy efficiency.

The architecture will be functional and pleasing and the building will be able to grow like a tree, in phases.  Resembling an evergreen tree, the stem/trunk will support two stepped building blocks.  Each building level will have a slightly different gravity, which offers many opportunities, functionally and for medical research.

The dwellings and the various amenities, such as daycare, school, hotel with restaurant, shops, medical clinic, fitness clubs, theatre, offices, etc., can be located according to the most suitable gravity level.  For example, people with reduced mobility would probably prefer less gravity.  On the other hand, it would be unpleasant to have food jumping off your plate in the restaurant, or feeling too light in the movie theatre.

This space will receive artificial rain produced by condensation from the air/vapor barrier.   The interior skin around the “south” pole will be covered with thicker soil and could be used for farming.  The inevitable dust created in the Buckyglobe will be deposited here due to centripetal force and will turn into fertile soil.  A small collection pond for storing water could be created here as well and would become an essential component of the ecosystem.

HUB

The Hub is composed of two main bodies, resembling the mechanics of a bicycle:  The wheel is connected to the Buckyglobes (which would be part of the tire) by the stems (spokes) and revolves around the fixed spindle, through magnetic levitation.

The two rings will be designed as a giant electromagnet (dynamo in a reversed action).  The Rotor is made up of many electromagnets placed in concentric circles.  The Stator would store batteries and other equipment. The circulation between the revolving and the fixed bodies will be done in the transfer rings, using moving escalators and walkways.  An air seal ring will prevent air from escaping into space.

The Hub will incorporate a nuclear reactor, possibly of fusion type, after the current research and experimentation would be completed, and would potentially transmit energy to Earth through a technology that still remains to be established (i.e. high-power waves, such as laser beams).

The Hub will accommodate docking facilities and workshops where the components received from Earth will be prepared for assembly in space by Robcons. Due to its microgravity, the Hub can include highly robotized manufacturing of new products and compounds that would be very difficult, or even impossible to produce on Earth.

The thrust to induce rotation will be provided by a system of booster engines (i.e. ion rocket) mounted at the end of the stem.   A second system will fire outwards on the axis as needed to maintain the Buckyglobe at a constant distance from the HUB before it is taken over by the centripetal force.  These engines will also act in case of emergency to maneuver the Buckyglobe and stabilize its position vis-à-vis the HUB in case it would malfunction or the tethering cables would fail.

In an initial phase of development, before a connecting stem is constructed, the Buckyglobe will be kept in balance on a spoke and tether cables system, that would also incorporate power and communication conduits.

STEM (SPOKE)

The Stems accomplish several tasks.  First, they support the Buckyglobes and other space modules.  Then, they connect the Buckyglobes to the Hub and provide circulation throughout the entire system.  The stems transmit the spinning motion from the Hub’s Rotor to each Buckyglobe.  Finally, they incorporates mass drivers (or catapults), also called electromagnetic guns, for projecting transportation shuttles and cargo shells into space.

In the initial phases, before the Stems are constructed, Spokes will be needed to provide a minimum compression capability for keeping the spheres at constant distance from the Hub.  This will be achieved with sections of pipe of approx. 1m diameter, sufficient to allow a construction crew to go through it.  The diameter and length of the sections will depend on the carrying capacity of the lunching rockets or space shuttle which will bring the 3STAR components into space.  They could also be used to store other cargo during this process.

Due to the large distance between the Hub and the Buckyglobes, tension cables will probably be required to prevent the Spokes from bending.  These cables are placed at critical nodal points on the Spoke and will be integrated in the Web. 

The Stems shall have a built-in capacity for expansion, so that future modules can be added.  The cylindrical sections shall be designed to also carry cargo from Earth the first time they are sent to the space station.  They shall also be designed to receive attachments for various services and future expanded nodes.  These will break down the Spokes into more manageable travel segments and will shelter various amenities, utilities, storage and manufacturing facilities.

For flexibility and security, each Stem and Buckyglobe shall have its own station for generating power and all basic elements such as oxygen, hydrogen & nitrogen, all required for subsistence.  This station shall be located somewhere between the Hub and the geodetic sphere.

WEB (SOLAR SAIL)

The Web will be designed to have a multitude of roles.  First, it ensures the stability of the entire system, through tension cables acting like a spider web.  The cables will link the critical nodes located on the Hub, Stems and Buckyglobes.  This will be especially important before the Stems or Spokes are completed, when booster rockets will achieve continuous tensioning.

Here again we learn from nature; spider webs are among the strongest structures in nature (if not the strongest), when we consider the strength they achieve per unit of material used.

The web could also support solar panels and could act as a Solar Sail that uses radiation pressure.  There is always the possibility that 3STAR will have to be moved to another orbit around the Earth, or in the distant future to another location in the solar system, or beyond.  Then, the Solar Sail will prove to be very useful.

Finally, the web will support power and communication cables and a giant antenna for deep space communication.

SPACE CONSTRUCTOR

The construction of the 3STAR would require the development of a versatile space construction vehicle for installing the various components and for providing transportation between the ISS and 3STAR before the Stems are in place.  After the interior links are established, its role would be limited to transporting larger objects that exceed the capacity of the Stem elevators, and of providing exterior maintenance and repairs.

This space vehicle should be able to accommodate 2 workers in a protected environment, and should have the minimum facilities required for work shifts lasting several hours.  It should have several robotic arms and have extended visibility from its cabin, through a television camera system.

The Space Constructor needs to be carefully planned to minimize the impact on the Earth’s environment and the risk to erection crews.  The entire vehicle should be manufactured on Earth and be able to fit into a cargo ship or into a cylindrical component of a lunching rocket.

ROBCON

The geometry of the ROBCON (Robotic Constructor) consists of two main volumes: a tetrahedron with truncated vertexes and a triangular prism, both with chamfered edges.  This shape creates maximum functional space and structural integrity with minimum air volume and materials required (i.e. the largest space is provided where needed, at the seats level).  The tetrahedron accommodates two communicating (but independent) Command Cabins with swivel seats and large television screens for maximizing external views, separated by an emergency sliding door.

Bumpers mounted on the truncated vertexes of the tetrahedron, facilitate maneuvering by preventing damage from potential collisions and three telescopic magnetic landing legs ensure stability in any position.

The Utility Cabin has several functions.  It creates an access vestibule from the Service Compartment, is used as a change room for space suits, and also has a snack bar.   But most importantly, it provides an emergency shelter and has a dry toilet.

The triangular prism encloses the Service Compartment, which is divided into three chambers. The Air Lock provides pressurization and access through an exterior hatch and a floor hatch into the Utility Cabin.  Another chamber services the manoeuvring thrust system.  The third chamber accommodates the folding robotic arms which, when not used, are tucked between the upper edges of the triangular prism and the base of the tetrahedron.

The control cabin can accommodate a crew of two.   Below each row of command seats there are two robotic arms that fold against the body of the triangular prism in inactive position, so each worker can use two independent arms.

The core incorporates upper and lower manoeuvring thrust systems, which will require very frequent starting and stopping.  To eliminate a possible failure of ignition, hypergolic propellants should be used (they spontaneously burn when they are combined), such as liquid Hydrogen or Hydrazine combined with Peroxide.  Unsymmetrical Dimethylhydrazine [(CH₃)₂NNH₂], also known as UDMH, is another useful propellant.  Another option is to use cold gas propulsion.

Furthermore, carriers may be attached on all three sides, for transporting various components, such as geodetic struts and panels for constructing the Buckyglobe.

Following the completion of Research, Design and Development, which will include laboratory experimentation on a scale model, all components of 3STAR can be manufactured simultaneously on Earth; then, they would be sent into space, and assembled near the ISS.