Taking Starship for a spin to create a little gravity
It turns out the biggest challenge in a manned mission to Mars may not actually be getting there…. It is surviving months without gravity and being able to walk off the spaceship when we arrive.
Any plan for manned missions to Mars must take into account the effects the long duration spaceflights required to reach the red plane will have on the astronauts. The effects of micro-gravity on the human body are no joke. Our bodies are designed to work in a 1g environment and without the pull of gravity things go wrong in a hurry. Fluids build in in the wrong places, blood volume drops, muscles atrophy, and eyesight and bone density declines. The longer the time in space, the worse the impact. If you have ever watched the return of any astronaut who just completed a multi-month mission in space you will notice they are often carried out of the space craft on a stretcher. It can take days or weeks for their bodies to start functioning normally after being reintroduced to gravity. This recovery period poses a major problem for a Mars mission that needs healthy astronauts to walk off their own spacecraft after a six-month journey to put together the base that will help them survive.
Creating true gravity is still outside our technological reach so companies like SpaceX may look to use a low-tech solution to solve the problem. So to create artificial gravity, we just need to take our Starship for a spin… literally.
When an object is spun around a center point (like a weight on a string spinning around your hand) the inertia of that motion on the object produces a force called Centrifugal force that (to the object) feels like gravity. Technically it is not a true force as Newton’s laws spell them out, but it is a force concept that produces the results we want. From the point of view of the object in motion, gravity is “pulling” it in a straight line away from the center point of rotation. You have experienced this type of “artificial gravity” if you have ever been on an amusement park ride that spins you in circles in a cylinder and you are held against the wall while the floor drops away.
Using centrifugal force to create artificial gravity in space was first proposed back in the early 1900s by the Russian scientist Konstantin Tsiolkovsky. NASA did some very early experiments with it during the Gemini and Skylab programs but no real-world applications were ever developed.
One of the first serious proposals in terms of a Mars mission came in the 1986 NASA Jet Propulsion Laboratory proposal “The Case for Mars: Concept Development for a Mars Research Station.” The study proposed that a three section ship connected at a center hub by a truss system. All three ship sections were proposed to spin around the connected hub and use centrifugal force to produce artificial gravity similar to the 1g experienced on earth.
This type of system was deemed critical to the health of the astronauts both throughout the journey and so they could effectively work on Mars without significant health issues from the journey.
A modern spin on this was proposed in 2019 by Youtuber SmallStars in which a modified SpaceX Starship with a rotating central core and connected truss system acted as a hub for two manned Starships. This proposal merges the NASA theoretical 1986 proposal with the potentially viable SpaceX Starship system in development today. Most interestingly, in 2021 Elon Musk acknowledged that SpaceX is considering a system along these lines.
The system SmallStars proposed uses SpaceX Starship technology that is already in development and could be adapted with some modifications to provide the necessary gravitational force the astronauts need. SmallStars proposed that his “Gravity Link Starship (GLS)” be attached on each side by a 100-meter truss to two separate starships giving the system a diameter of ~200 meters.
Using the Spin Calculator we can see this setup allows a relatively slow three rotations per minute rate to generate Earth standard 1g at the center decks of each rotating starship. The starships would rotate to point inward toward the GLS for the journey to Mars effectively restoring normal gravity and function inside the ships.
An added bonus to the GLS concept is that fragile but necessary equipment like a solar panel array and deep space communication equipment could be placed on the stationary portions of GLS to generate constant power and create a stable communication link with earth. These could be tied into the rotating Starships via an umbilical line and effectively offload the weight and complexity of these systems to the GLS which will not land on Mars.
A concept like the GLS to provide artificial gravity is a critical piece to the Mars Blueprint in that it ensures astronauts arrive on Mars healthy and fit for the required missions.