Leveraging Centripetal Acceleration to Combat the Challenges of Spaceflight

Abstract

Since the beginning of human spaceflight in 1961, humans have endeavored to overcome challenges with each mission to improve the safety and efficiency of the space industry. However, a new challenge arises with modern-day space programs eyeing long-term travel to Mars and beyond. The lack of gravity on long-duration missions potentially damages astronauts’ circulatory, neurologic (specifically brain), and musculoskeletal systems. To combat this, an artificial force of gravity must be created. A force such as this can be generated using centripetal acceleration, or the rotation of an object, which creates an outward-directed force. Through the controlled rotation of a large, ring-shaped spacecraft, astronauts could mitigate the impacts of microgravity on the human body. This paper includes the possible concepts, logistics, costs, and implications of utilizing centripetal acceleration in future space missions, offering insights into feasibility, benefits, and potential applications for future spaceflight.

Introduction/Background

Prolonged exposure to microgravity can potentially compromise multiple physical aspects of the human body. After an extended period in space, astronauts experience muscle atrophy, reduced bone density, as well as more permanent damage in fluid redistribution that affects vision and the brain, as well as cardiovascular deconditioning. While astronauts currently have a schedule that includes hours of exercise each day on the International Space Station, these measures only partially mitigate the damage. Thus, researchers have begun to explore possible solutions to this problem, and the most promising one yet is leveraging centripetal acceleration in space. 

The most viable concept for generating artificial gravity with our current technology is through centrifugal acceleration. This would involve a large, ring-shaped spacecraft that would rotate, forcing acceleration to the outer rim, thus mimicking gravity. However, this idea is not new. It was introduced in the 1940s by Werner von Braun, who proposed a massive, rotating space station ( [3] Clémet, Burkley, Paloski, 3). This idea was then popularized by the book and movie "2001:  A Space Odyssey," directed by Stanley Kubrick in 1968. The backdrop included an expansive, rotating, circular space station that provided artificial gravity for the comfort of its guests ( [3] Clémet, Burkley, Paloski, 3). 

Formal studies regarding this design began in the 1970s. A notable prototype was conceptualized by Stanford students via a space station consisting of a large tube measuring 130 meters in diameter. This tube would measure over five kilometers long and be bent in the form of a ring. Once rotated at 1 rpm, the space station would generate a comfortable Earth-like gravity for its inhabitants ( [3] Clémet, Burkley, Paloski, 3). However, these concepts were ultimately unfeasible for the time’s technology. Other proposals included large modules connected through two ends of a large tether, generating the same effect as a conventional ring, but with fewer parts. However, this concept would have faced several logistical challenges, such as launch vehicles, construction feasibility, and technological limits. Yet another design suggested a smaller centrifuge measuring two meters in diameter; the limitations of this prototype are the differing rotational speeds for the head and feet, thus making it uncomfortable for its occupants ( [3] Clémet, Burkley, Paloski, 6).

Testing of animals has been conducted since the early days of the Space Age in the 1960s. Soviet experiments with turtles, fish, and especially rats showed promising effects of using centripetal acceleration. Results after 10-20 day-long missions have shown that centripetal acceleration has a protective effect on the integrity of the cardiovascular system, as well as the muscles and bones. This was all compared to animals who were not subjected to artificial gravity ( [3] Clémet, Burkley, Paloski, 7). 

Currently, astronauts on the ISS use exercise regimens that incorporate the Advanced Resistive Exercise Device (ARED) and treadmills (Lloyd, 2023). This helps combat muscle and bone atrophy in microgravity; however, they may not be sufficient for long-duration missions to destinations such as Mars (7-9 months) or even outside the asteroid belt to Jupiter’s moons. The machines are also cumbersome and take up a lot of space, which poses a challenge for designers to innovate a new prototype (Lloyd 2023). 

NASA also mentions the use of medications to combat this issue. For example, drugs used to prevent bone loss on Earth may also be successful in preventing bone and muscle loss in both astronauts and animal models in space (Lloyd 2023). This has been tested before in Rodent Research 19 (RR-19) (Lloyd 2023). 

Regarding the potential for muscle atrophy, NASA is currently developing advanced technologies, such as tissue chips, to stimulate tissues with electrical pulses to mimic physiologic muscle contractions; initial findings of this research have been favorable and provide an opportunity for further elaboration. (Lloyd, 2023).

Main Body

NASA engineers believe that the choice of artificial gravity depends on whether the crew is to be stationed in continuous or intermittent gravity conditions, thereby assigning a large-radius spinning vehicle or a small centrifuge model for the individual mission ( [2] Clémet, Burkley, Paloski, 9).

Continuous - Spinning vehicle: A Von Braun-style space station would represent this best, as exemplified in "2001: A Space Odyssey," which would be the ideal design. This prototype consisted of a large toroid, or ring shape, 75 meters in diameter and constructed of several rigid modules, joined together by an inflatable material. Imagine 4-8 spokes of a central core, with rigid, short, circular modules at the ends. These modules would then be connected with softer, inflatable modules. This was envisioned in the earlier days of the space program from the 1950s to the 1970s, but remains a promising option with iterations of the original design  ( [2] Clémet, Burkley, Paloski, 10). Rigid modules would be launched using conventional rockets and act as adapters between the inflatable modules. The inflatable modules would then be able to bend from rigid module to rigid module, and function as the habitable areas of the space station. Based on earlier Von Braun concepts, this space station would likely be constructed using robotics and be able to house roughly 50-100 astronauts. The space station would begin rotating using thrusters or very small amounts of propulsion, to be used infrequently (no air resistance or gravity slowing it down). 

Continuous - Tether: Tested during the 1960s Gemini era, a tether system to simulate artificial gravity is also a viable option ( [2] Clémet, Burkley, Paloski, 11). A variable-length tether that can connect two spacecraft a few hundred meters apart has been considered to be the most acceptable design for a space station ( [2] Clémet, Burkley, Paloski, 11). While tether strength is a concern, several studies have been conducted, as the source mentions, which prove tether failure is unlikely. These examples from a previous study that the NASA study mentions are reason enough to satisfy the argument that a tether is relatively safe when being used to attach spacecraft ( [2] Clémet, Burkley, Paloski, 11). 

Intermittent deployment: A 2-meter radius centrifuge offers an alternative to a constantly rotating spacecraft that is both large and costly. A smaller spacecraft can have an artificial-gravity module that spins infrequently for the crew ( [2] Clémet, Burkley, Paloski, 13). This can enable astronauts to stand or walk within the limited space. However, as the radius decreases from 2 meters, astronauts would have to adopt a crouched position due to space constraints as well as discomfort due to different spinning speeds for the head and feet. This is an unlikely solution due to possible complications with orientation and health of the body ( [2] Clémet, Burkley, Paloski, 13). 

Contemporary: Currently, the most feasible solution would attach flexible, inflatable modules to rigid modules deployed by large spacecraft.  A good example of this technology is SpaceX's Starship, which has a high payload capacity. This form of construction is a proven concept, as the ISS was constructed by assembling dozens of modules. This technology would be able to be used in long-term space missions, specifically, ones that can replace the ISS. For example, a crewed space station in LEO (Low Earth Orbit) or around the Moon would allow its crew to remain for longer durations, as there is no longer a concern for travel time. A large spacecraft can be constructed and deployed to Mars or Jupiter’s moons; while it may take more effort than launching a single spacecraft, the health risks for the crew would be mitigated in this model. 

The largest challenge facing this concept is neither the logistics nor the structural weaknesses. NASA believes that the biggest challenge is the Coriolis forces, which astronauts must face depending on the size of the spacecraft (Beard, 11). The Coriolis force can be described as the differences in velocity that different parts of the body experience when in a space station ( [2] Clémet, Burkley, Paloski, 6). For example, the equation F = 2m ω v ( [2] Clémet, Burkley, Paloski, 6). NASA stresses that the vectors of all parts of the body should be in alignment; otherwise, astronauts will experience extreme discomfort. This means that the head of the astronaut must spin at close to the same speed as their feet, even if the head is closer to the center of the space station ( [2] Clémet, Burkley, Paloski, 6).

Some tradeoffs are associated with pursuing this type of technology. For example, the commitment to a project such as this one is very long-term, expensive, and complicated. A large spacecraft would have to be built over the years, much like the ISS, and be tested for it to be crew-safe. The costs for a space station that utilizes centripetal acceleration would likely be the same, if not more than the ISS, as the scale would be much larger, in both pressurized and unpressurized volume. However, this project would provide astronauts and crew with a comfortable and familiar environment for their time onboard. Trips to Mars or even crew rotations on science stations would have less potential for compromising the health of the astronauts, a concept that NASA is contending with today. Currently, NASA astronauts' efforts to stay fit on the ISS are insufficient to maintain their physical integrity, especially after they land on Earth. While tissue chips and new exercise equipment may be a contemporary solution, they still do not fix the problem of the physiologic changes (such as fluid shifts) that occur to the human body when exposed to microgravity (Elberfeld, 9). Having a constant force of gravity on a space station that utilizes centripetal acceleration will not only enhance the viability of space exploration but also open the doors to making it more accessible to the public. 

NASA states that having a constant force of artificial gravity similar to the forces that we experience on Earth has the potential to decrease or eliminate the negative effects astronauts currently experience in microgravity (Elberfeld, 9). Exercise will no longer be a necessity and will only be a mere choice for astronauts if bones and muscles are subjected to 1g of force or even a partial g (Elberfeld, 9). Fluid will be directed back toward the lower body and other proper storage areas, relieving the current challenge of tissue swelling and displacement, which can at times cause permanent health conditions for current astronauts (Elberfeld, 9). Thus, replicating gravitational forces, which align with human physiology, is the most viable solution, outperforming exercise, drugs, or electrical stimulation of muscles. Recovery time will also be less than that of today if astronauts are subjected to a downward force, eliminating the need for reintegration on Earth or the Moon and Mars (Elberfeld, 9). 

The modern era of space exploration has ushered in many private companies that are trying to leverage the power of centripetal acceleration on space stations to provide a more comfortable environment for astronauts. One of the only official programs is by VAST Space, a private company that is pursuing many ventures in outer space. A notable project is developing artificial gravity space stations to make space exploration more accessible to laypeople. This prototype can be further developed to be marketable to the private sector. Many have shown their interest in leveraging artificial gravity, including private space company Blue Origin. Using centripetal acceleration as an achievable way for artificial gravity will likely be common in the future when exploring deep space on long-term missions.

For such a large-scale project to be executed, new sectors of space exploration must be developed, the most important being space manufacturing. Large space stations, hundreds of meters in diameter, cannot simply be built with modules docking together like the ISS was built. Entire construction platforms, along with crews and robotics, repeatedly assembling multiple modules, need to be leveraged to complete a large task. For example, NASA’s ISM (In-Space Manufacturing) objective outlines space production being self-sufficient, and to construct within space, rather than deploying pre-built equipment into space (Prater, 4). NASA is currently eyeing 3D printing as well as robotics as a form of in-space manufacturing, as these resources are easily accessible and can be used for construction in outer space. Prater mentions using asteroids as a source for materials, likely for 3D printing and as a platform to construct products (Prater, 7). 

Missions such as these can be contracted to private companies, such as SpaceX or Blue Origin, as they have been participating in the human space program since establishing the Commercial Crew Program (Donaldson, 2025). Launch vehicles such as SpaceX’s Falcon 9 or Starship are inexpensive, reusable, and have a large payload capacity that can be used to send modules, robotics, materials, and crews to construct such a project. Contracting to private space companies from large government organizations such as NASA would be a reasonable investment. NASA currently does not have vehicles that can construct such a project on this scale. While a space station such as this one can be used for scientific purposes, companies such as VAST Space, Sierra Space, or Blue Origin see more comfortable and accessible space travel through the eyes of space tourism, something that is beginning to evolve. These companies have developed plans for in-space hotels, inflatable modules for a more comfortable climate, or rapidly reusable rockets to shuttle cargo into space. 

Artificial gravity through leveraging centripetal acceleration in space has the potential to greatly enhance human life by addressing the major health challenges associated with long-term weightlessness, such as muscle and bone atrophy, organ degradation, and fluid displacement. By simulating Earth-like gravity using centrifugal force in rotating space stations, this technology allows for longer, safer, and healthier stays in space with less physical stress for astronauts. It supports a larger vision of a space economy, allowing for scientists, engineers, and civilians to live and work outside of Earth’s environment without suffering consequences to their health. Using centripetal acceleration in space is not only about making it a healthier stay for astronauts, but also making space more accessible for all. 

Currently, this technology has an optimistic future. Many private space companies, large and small, are proposing large space stations, as well as hotels and tourist attractions that leverage centripetal acceleration to support the comfort of their guests. Many of these companies are proposing to build hotels or tourist attractions. With launch vehicles in development such as SpaceX’s Starship, testing of inflatable modules for Sierra Space, and the growing involvement of robotics and artificial intelligence in space exploration, this concept could become more feasible than originally thought. Not only will private companies use this technology, however. For long-term missions to Mars and beyond, astronauts will need to stay fit and in a comfortable gravity environment. This is where this technology can be used to benefit scientific purposes, keeping astronauts and scientists healthy on long-term space missions. 

The largest unforeseen problem that such a project will bring is public interest. During the Apollo era, the United States visited the Moon for less than a decade until we won the Cold War, and were therefore disincentivized to pursue space exploration. This is not a one-time occurrence; however, interest in space programs ultimately leads to delays or cancellations. Programs such as the Space Shuttle or Constellation were cancelled due to public disinterest or lack of funding. This will likely be an obstacle for a feat such as this one. The decision is ultimately up to the culture and climate of the era. 

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