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Spin gravity cities fabricated from Near Earth Asteroid rubble piles

A cylindrical, spin gravity space settlement constructed from asteroid rubble like that from the Near Earth Asteroid Bennu. The regolith provides radiation shielding contained by a rigid container beneath the solar panels. The structure is spun up to provide artificial gravity for people living on the inner surface. Credits: Peter Miklavčič et al.*

Scientists and engineers* at the University of Rochester have conceived of an innovative way to capture a Near Earth Asteroid (NEA) and construct a cylindrical space colony using it’s regolith as shielding. In a paper in Frontiers in Astronomy and Space Sciences they propose a spin gravity habitat called Bennu after the NEA of the same name. Readers will recall that NASA’s OSIRIS-REx spacecraft launched in September 2016, traveled to Bennu, collected a small sample in October 2018 and is currently in transit back to Earth where the sample return capsule will reenter the atmosphere and parachute down in Utah later this year.

Near Earth Asteroid Bennu imaged by the spacecraft OSIRIS-REx. Credit: NASA Goddard Space Flight Center

It would be ideal if an asteroid could be hollowed out for radiation shielding and spun up to create artificial gravity. However, it is shown in this paper that this would not work for larger solid rock asteroids because they don’t have the tensile strength to withstand the rotational forces and smaller rubble pile asteroids (like Bennu) would fly apart because they are too loosely conglomerated.

The problem is solved by containing the asteroid in a carbon fiber collapsible scaffolding that initially has the same radius of the asteroid. As the container is spun up, the centrifugal force will cause the disintegrating rubble to push open the expandable cylinder to its final diameter.

“…a thick layer of regolith is created along the interior surface of this structure which forms a shielded interior volume that can be developed for human occupation.”

The mechanism to initiate the rotation of the structure is interesting. Solar arrays on the outer surface would power mass driver cannons which eject rubble tangentially exerting torque to produce spin.

Detailed engineering analysis and simulations are performed to calculate the stresses on a Bennu sized asteroid to create a cylindrical space colony 3 kilometers in diameter. This structure would have a shielded livable space of 56 square kilometers, an area roughly equivalent to Manhattan.

The authors conclude that the physics of harvesting small asteroids and converting them into rotating space settlements is feasible. They note that this approach would cost less and be easier from an engineering standpoint then fabrication of classic O’Neill cylinders. Concepts for asteroid capture and utilization have already been covered on SSP such as TransAstra’s Queen Bee and SHEPHERD.

The University of Rochester News Center provided a good write up of the paper last December.

* Authors of cited paper: Miklavčič PM, Siu J, Wright E, Debrecht A, Askari H, Quillen AC and Frank A – (2022) Habitat Bennu: Design Concepts for Spinning Habitats Constructed From Rubble Pile NearEarth Asteroids. Front. Astron. Space Sci. 8:645363. doi: 0.3389/fspas.2021.645363

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The business of asteroid mining

APS-1, an asteroid prospecting satellite conducting a spectral survey of 5000 Near Earth Asteroids (NEA). Credits: Asteroid Mining Corporation.

The Asteroid Mining Corporation wants to open the resources of the solar system toward a brighter interplanetary future. AMC claims that it does not need to mine an asteroid to be commercially successful, at least initially. The small start up proposes a practical transitional approach based on incremental successes to pay the bills while capitalizing on technological innovations to achieve the ultimate goal of mining an asteroid.

They plan to start with a remote sensing mission called Asteroid Prospecting Satellite (APS-1) to survey Near Earth Asteroids (NEA) to identify which are the most viable candidates for mining. AMC will then sell this data to customers interested in their own mining operations.

The next mission would be an Asteroid Exploration Probe (AEP-1) capable of visiting multiple targets and including a small landing probe to survey the mineralogical, metallurgical and molecular constituents of the most promising high platinum bearing Asteroids identified by APS-1, and test mining equipment.

AEP-1, an asteroid exploration probe visiting a promising NEA to confirm mineral content and test mining equipment. Credits: AMC.

The ultimate goal of AMC’s effort is the worlds first asteroid mining mission called Asteroid Mining Probe (AMP-1) designed to extract 20 tons of platinum. The AMP-1 spacecraft would be marketed to other customers around the world and would help establish the infrastructure for an extraterrestrial economy.

AMP-1, Earth’s first commercial asteroid mining mission. Credits: AMC
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NEO Robotic Friend for crewed asteroid reconnaissance

The crewed asteroid exploration vehicle NEO Robotic Friend in two different operational modes. Credits: Luca Levrino, et al.*

In a paper presented at the 65th International Astronautical Congress, Toronto, Canada in 2014 and posted to Acedemia.edu, a team of students* from Italy and Germany discuss an innovative small unpressurised vehicle designed for mobility and maximization of human agility for safe crewed exploration of near earth asteroids (NEA). They named their brainchild NEA Robotic Friend (NRF).

Though conceived when NASA was focused on the Asteroid Redirect Mission (ARM) architecture with the emphasis on developing technology to expand beyond the Moon toward eventual missions to Mars, the NRF could have practical applications in the next phase of space settlement when humans have established a beachhead on the moon and are ready push out into the solar system.

The vehicle was designed to enable safe human proximity EVA operations around a NEA independent of the type of asteroid. Another primary design objective was to investigate, test and validate the use of key technologies for deep space exploration including the ability to collect surface and core samples storing them so that they could be analyzed on Earth. Finally, the platform was envisioned to have the ability to perform in-situ experiments, with real-time data analysis.

* The reference paper was the result of a project within the Alta Scuola Politecnica, joining together students from Politecnico di Torino and Politecnico di Milano. The authors are Luca Levrino, Chiara Gastaldi and Maria Antonietta Viscio from Politecnico di Torino, Italy. Alessandro Ciani, Margherita Censi, Alessandro Cingoli, and Paolo Maggiore from Politecnico di Milano, Italy. Ricardo Repenning from Technische Universität München, Germany