Ex - Tesla. Kairos Society Fellow. SpaceX OpenLoop. TEDx speaker.
It’s been the dream of many space enthusiasts from the 1960s to live in an intelligent artificial gravity space station ever since it was popularized by NASA chief scientist Von Braun and the legendary film: ‘Space Odyssey: 2001’.
Unfortunately, generating artificial gravity for astronauts was not a priority for NASA as astronauts were able to reduce some of the impact of weightlessness on their bodies thanks to a ruthless exercise regimen. Further, a ship that contains a centrifuge for generating artificial gravity would be extremely expensive to launch to orbit. So, NASA ended up sticking with a compact and modular station that is more affordable with their budget and that doesn’t deal with weightlessness risk and accepted the risks it posed to astronauts in the international space station.
Below is a comprehensive list of health risks astronauts face in the zero-g space station. Weightlessness risks are highlighted in the red box.
Over the past few years, new reports have come out that most astronauts are now facing visual impairments, immunosuppression, osteoporosis, and risk potential brain damage that cannot be tackled by their exercise regimen.
Currently one of the biggest concerns is VIIP (Visual Impairment/Intracranial Pressure) syndrome which structurally changes the shape of the eyeball and in some cases can create blind spots.
Reference: Alperin N., Bagci A.M. (2018) Spaceflight-Induced Visual Impairment and Globe Deformations in Astronauts Are Linked to Orbital Cerebrospinal Fluid Volume Increase. In: Heldt T. (eds) Intracranial Pressure & Neuromonitoring XVI. Acta Neurochirurgica Supplement, vol 126. Springer, Cham
Japanese Space Agency (JAXA) ran an experiment with mice onboard the ISS Kibo.
Centrifuges were used to generate artificial 1G gravity.
It was found that the artificial gravity generated did, in fact, negate the effect weightlessness had on visual impairment.
Below are the CAD model and cross-section of the centrifuge used by JAXA to carry out the experiments.
radius= 0.15m, centripetal acceleration=9.81m/s^2, angular velocity= 77.2 rpm
Artificial gravity centrifuge experiments on Kibo also found that mice lost less bone mass when in 1G artificial gravity.
Further studies have shown that there could be potential brain damage if the astronauts stay in weightlessness long enough. Src: MUSC researchers, press release: https://www.telegraph.co.uk/science/2017/11/01/humans-may-need-fake-gravity-reach-mars-without-brain-damage/
Dr Michael Antonucci, at the Department of Radiology and Radiological Science at MUSC said
“Designing a space vehicle with artificial gravity might be a way of minimizing the changes that occur in a microgravity environment.”
“Artificial gravity does not countermeasure for just one thing; it addresses all physical systems,”
says Gilles Clement, the lead scientist for artificial gravity in the Human Health Countermeasures Element of the Human Research Program at NASA’s Johnson Space Center in Houston.
The solution to weightlessness related health issues? Intelligent artificial gravity space stations and spacecraft for long stays in space
Src: Nautilus-X potential design by NASA
1. Decreasing the cost per kg substantially (pending)
For massive structures (artificial gravity space stations) to be built in space, it has to be first affordable to do so. Previous rockets were just too expensive to allow any government entity to sustainably fund a massive space station. Even the international space station is an international government effort to reduce the financial burden on any single government.
Reusable rockets are changing the game when it comes to making space accessible. Below is a chart referencing the estimated cost per kg for some famous rockets.
SpaceX’s BFR which is currently in the design and prototype stage might further drop the cost per kg to LEO to a few hundred dollars when it’s in full use. This could be a game changer.
2. Decreasing the total mass of the space station to reduce the cost of launch substantially (pending):
There are 2 proposed ways structures can be built with high strength and low mass: Tensegrity and Trusses.
Tensegrity is ‘the characteristic property of a stable three-dimensional structure consisting of members under tension that are contiguous and members under compression that are not.’ src: Oxford
NASA recently funded research on tensegrity approach to building an artificial gravity space station
NASA is even considering using tensegrity rovers for planetary missions in the future.
Trusses can be easily folded or be disassembled in a modular way to be reassembled in orbit.
The main support structure on the ISS is a truss. Different sections of the truss were brought on different space launches.
Src: Canadian space agency
So the main spokes and rim of the artificial gravity space station can be designed as trusses in order to reduce weight and join them together in a modular fashion.
For starters, it can also be a truss mast which spins on the center.
Ref: NASA's Multigenerational Independent Colony for Extraterrestrial Habitation
A perfect low weight design has yet to be perfected but would be a game-changer.
3. Intelligent gimbals to point solar panels toward the sun (current)
Beta Gimbal Assemblies (BGA)
Bearing Motor Roll Ring Module (BMRRM).
These gimbals are critical to sustain the presence of the station in space. Pointing the solar arrays to the sun allows the station to have electricity around the clock. Electricity is essential to maintain operations and power onboard electronics and other embedded systems
These gimbals can be set up in an open-loop control or be part of an intelligent system where it is a closed feedback loop with sun tracking sensors (like Adcole).
4. Reaction Control Thrusters with PID control & sun sensors to control and monitor the spin rate (current)
It is critical that the space station has a stable spin rate.
Hypergolic RCS (Reaction control system) thrusters similar to R-4D can be used on each end of the mast of the intelligent artificial gravity station to control the spin
(seen in picture - RCS thrusters on the end of the mast)
Further, ADCOLE Coarse Sun Sensors positioned along the truss will help us monitor the spin rate of the station by calculating how much time it takes for the Adcole sensor to view the sun twice in its field of view.
ref: Coarse Sun Sensor Detector (Cosine Type)
‘The Coarse Sun Sensor Detector is a single detector model used for applications including solar array pointing, sun acquisition, and failsafe recovery.’ src: adcole.com
The RCS thruster and the Adcole sensor can be potentially set up in a PID control loop such that based on feedback from the Adcole sun sensor, the RCS thruster can do spin rate corrections.