Exploring Space Is All about Gravity
All living things in our world evolved in a 1 G (gravity) environment. There is gravity in interstellar and interplanetary space but much lower than the 1G we experience on Earth. Astronauts have experienced microgravity on the International Space Station and orbiting space capsules. A small number of astronauts have experienced longer exposure to this microgravity on the Space Station. As of the date of this blog, two astronauts are in the middle of a mission there, investigating how microgravity affects space mariners over the long-term, in this case twelve months. This will provide space agencies with more knowledge that can be used to design and engineer spacecraft that will carry astronauts safely into the Solar System, on missions that will take years before returning to Earth. This is the next big step in space exploration.
As a teenager, I watched a live telecast of the first moonwalk, one of the greatest achievements in human history, in an international virtual classroom with 500 million other people. It was a riveting, exhilarating, nail-biting experience. Nobody was bored or daydreaming in class that day! We learned firsthand, looking at those images of Buzz Aldrin and Neil Armstrong bouncing along the surface of the Moon, what lower gravity on the Moon looked like. We immediately understood the difference between 1G, Earth’s gravity, and the Moon’s gravity, 15% of 1G, something that sparked inquisitive imaginations.
The unexplored frontier in space is much further away now since the first Moon landing in 1969 because scientists and engineers at space agencies around the world have pushed back the boundaries of the unknown in the Solar System and the Universe. NASA has launched robots to explore other planets in the Solar System. Two of the most famous, launched in 1977, the Voyageur robots have now travelled beyond the Solar System, both of them over 20 billion kilometers from Earth.
Along their flight paths, these robots used the gravity of planets to slingshot their way to the outer reaches of our Solar System, past the Kuiber Belt and Oort Cloud and into the Heliosphere. Voyager 1 is now past the Heliosphere into interstellar space. Voyager 2 is almost there, on the outer edge of the Heliosphere. Gravity from Jupiter and Saturn provided an assist, or boost that enabled the efficient propulsion of these spacecraft along their flight paths, on missions that have taken them further from Earth than any man made object before them. These missions are now over 38 years in duration and will keep going on, maybe forever.
Will Hunter has gone well beyond the Kuiber Belt and Oort Cloud in Mission 32. He has travelled to the Outer Belt on the far side of the Near Universe, a distance one way of 80 trillion kilometers, a distance usually measured in light years (4 LY). In the story he is away for 9 months in real time, meaning if he had returned directly to Earth he would have arrived 9 months later, which he did not. How Will’s spaceship crossed 160 trillion kilometers in 9 months will be the subject of another blog about the underlying science of space flight in Will Hunter’s Mission 32 story.
Gravity is critical if humans are to have normal physiological and musculoskeletal system function over long periods of exposure in space. That’s why NASA is studying the effects of long-term exposure to microgravity by having two astronauts live on the Space Station for 12 months. Long-term space travel will require spacecraft that maintain 1G. Ships ferrying humans over long distances in the future will create that gravity artificially. In Mission 32, it was achieved by engineering spacecraft to rotate at a rate of revolutions per minute that generate a centrifugal force of 1G, or in other words, artificial gravity. The vessels rotate along their longitudinal axis in the direction being travelled. Safety issues were also considered in the spacecraft designs. Ice and dust particles moving through space from events such as collisions of celestial bodies, or from distant supernovae could damage a spacecraft. The longitudinal rotation and shape of the vessels provide the most efficient design, with the smallest exposure to hazards in flight, while providing normal 1G for the space mariners enjoying the ride. These were the factors considered in designing the flagship Hercules and the shuttles in the Mission 32 story.