Physics and Space Travel
The human race has always been fascinated by the concept of outer space and what lies beyond our Earth. Mankind’s innate curiosity has inspired numerous technological advancements that have made it possible for humans to travel into space and explore what was previously only the subject of dreams and imagination. Early writings such as The Brick Moon by Edward Everett Hale illustrate how little was actually known about outer space, and the physical and practical limitations humans must overcome to escape Earth’s gravity. The Brick Moon is a science fiction short story written in the 1800s and it is one of the first known writings to describe the construction and launch of not only an artificial satellite, but also a space station (Wikipedia, 2011). The story The Brick Moon outlines some of the building blocks for modern day space technology and travel but the approach used in the book is impractical for real world application.
The Brick Moon is written from the perspective of one of the main characters and recounts how he and his friends planned, funded, constructed, and eventually launched a satellite or manmade “moon” into space. The purpose of the Brick Moon was to act as a navigational aid for ships at sea. The idea was based around the North Star, which sailors used as a guide to determine their latitudinal location; the inventors wanted to launch the Brick Moon to orbit along the Prime Meridian so that sailors could just as easily gauge their longitudinal location (Hale, 1869). The characters even go so far as to consider the possibility of launching multiple moons to form a ring like Saturn’s around the Earth, but rather than running horizontally it would run vertically. Multiple moons would ensure that at any given time and at any given place on Earth at least one of the moons would be visible (Hale, 1869).
This demonstrates the premise behind contemporary navigational systems and is fundamental to the current Global Positioning System, or simply GPS. A major problem with their plan of launching the moon into a longitudinal orbit along the Meridian lies in the fact that, in addition to circling around the sun, the Earth itself is constantly spinning. Therefore, even if the Brick Moon were to follow a longitudinal orbit, it would not correspond to the same longitudinal line on Earth (Brown, 2000).
To overcome this limitation a modern day GPS establishes one’s exact location using signals transmitted through multiple satellites travelling along different orbital paths in space. The transmissions indicate the current orbital location of the satellite and the time the signal is sent. The GPS receiver then calculates the time it takes to receive each signal and the distance between each satellite to accurately determine the receiver’s precise location (Brain & Harris, 2006). The plan presented for using the Brick Moon as a tool for navigation, although impractical in a real world setting, provided a basis for our current navigational technologies. Moreover, before the GPS became possible or even commonplace, humans had to first figure out how to launch a satellite into space.
The characters in the story were also faced with the challenge of developing a plan to construct and launch the Brick Moon into space. They decided that the Brick Moon must be constructed so it would be large enough to be easily visible from Earth, but it must also be light enough and built with a strong enough material to withstand the launch. In order to satisfy these criteria they determined that they would build a hollow sphere 200 feet in diameter and cover it with 12 million bricks, thereby making it resistant to fire as it travelled through the atmosphere (Hale, 1869).
A sphere of that magnitude is difficult to visualize, so to offer some perspective, the moon they planned to construct would be just over 35 feet larger in diameter than “Spaceship Earth”, the iconic symbol of Epcot Centre at Walt Disney World Resort (Wikipedia, 2011). To launch the moon their plan was to set it at the top of a giant hill, build up momentum by rolling it down the hill on a track leading to a gorge at the bottom, then, using two giant flywheels powered by the rushing water, catapult the sphere into space. In an unlikely sequence of events, the Brick Moon slides down the hill prematurely and launches unexpectedly into space carrying with it 37 people; a few members of the construction crew and their families (Hale, 1869).
While this is a very creative idea, realistically it would be physically impossible to simply catapult an object into space in this manner, especially by accident. Launching an object into space is a very calculated and precise procedure. As discussed in the lectures, the escape velocity, or the speed required to break free of the Earth’s gravitational field, is just over 11 kilometres per second. As such, there is no possible way that the sphere could gain enough momentum rolling down the hill to build up the amount of speed needed to escape the Earth’s atmosphere. Furthermore, as was also discussed in lectures, Isaac Newton’s third law states that action and reaction are equal and opposite forces, meaning that as the sphere hurtled upwards it would experience the counteractive force of air resistance in the opposite direction.
To overcome these challenges, scientists have determined that to escape the Earth’s gravitational pull and launch objects into space it must be done in a series of stages, each stage giving the object another boost of acceleration. When launching a rocket into space the energy expelled by the exhaust out the back of the rocket is what forces it upwards, as the amount of fuel in the tank decreases, the rocket becomes lighter and acceleration increases. Used fuel tanks are discarded to shed excess weight, and back up fuel tanks give the rocket the next stage of acceleration needed to escape the Earth’s gravity (Thinkquest, 2004). Without the extra boosts in acceleration, the sphere would succumb to the gravitational pull and very rapidly plummet back down to the ground with fatal results for those on board. Conversely, if the sphere were to gain enough acceleration to escape the Earth’s gravity the sheer force exerted on the people aboard as it shot upwards would literally flatten them. Although the story does portray a launch that would in fact be physically impossible, it provides a very basic description of what would eventually become a known as a space station.
Space stations have been operational in Earth’s orbit since the 1970s and crew members live and work on the space station. This allows opportunities for researchers to study the long term effects of outer space and weightlessness on humans (Freudenrich, 2000). Crew members on a space station must take special precautions to protect themselves from the harshness of outer space and life aboard a space station is nothing like life on Earth.
Life for the 37 people aboard the Brick Moon, however, did not experience the extreme differences living in space that would actually occur in reality. After the launch of the Brick Moon the inhabitants built new lives for themselves and went on happily living on the surface of the satellite, where the atmosphere remained much the same as that of Earth. They enjoyed a tropical climate, they got regular rainfall, and over time plant life and trees began to grow and flourish. This permitted them to grow their own food and sustain life with seemingly little effort. They made efforts to keep in contact with their friends on Earth, and they did so by lining up and simultaneously jumping up and down on the surface to spell out messages in Morse code. From an observatory on Earth, their friends were able to view these displays and record the messages in chronological logs (Hale, 1869).
There are a number of obvious practical issues and physical impossibilities regarding their survival on the Brick Moon. The first problem is that the atmosphere on the satellite undoubtedly would not be the same as the atmosphere on Earth. Radiation levels in space are hazardous, there is no friction, no oxygen to breathe, no rainfall, and plant life is most certainly not sprouting up on existing satellites in Earth’s orbit. The second problem is that pressure in space is different from pressure on Earth and microgravity or weightlessness can have a detrimental effect on humans physically and psychologically (Houston Television System, 1999). It would be impossible for the Brick Moon inhabitants to simply wander around on the surface as if nothing had changed. Life in outer space, outside the confines of a space station or shuttle, requires the protection of a space suit which regulates the pressure, temperature, environment, and oxygen levels needed for the human body to survive (Houston Television System, 1999). None of these factors were of any consideration for the inhabitants of the Brick Moon, but they are serious factors for humans to be aware of in real world space travel.
Although there are numerous impractical and impossible aspects in the story of the Brick Moon, a great portion of the story talks about how the characters go about raising money to finance the project of building the Brick Moon. The characters spend a lot of time campaigning and convincing the public of the benefits that their proposed Brick Moon will provide, as well as making multiple design changes as the plans progress. This is very similar to the real world in that space travel and exploration requires enormous amounts of money for research and development of new technologies, construction and testing of equipment, as well as training and preparation of astronauts for missions. Space programs rely a great deal on funding from outside sources; be it through government funding or research grants and proposals may undergo a cost-benefit analysis before funding is approved. It is also typical that as plans and development progresses, necessary changes are made to the design of new space technologies to address problems, flaws, or new discoveries.
The Brick Moon is a somewhat prophetic science fiction story about space travel and was ahead of its time in terms of its depictions of scientific inventions such as manmade satellites, GPS, and a space station. However, the techniques used to launch the Brick Moon, as well as the assumptions made about what life would be like for the inhabitants once in space prove that it is a great deal more fiction than science.
Space travel will continue to draw human curiosity which will contribute to the development of new theories, discoveries, and cutting-edge technologies. However, we will be forced to come up with new ideas of how to overcome the physical limitations we experience on Earth, including such things as gravity, and the maximum speed of acceleration or g-force that a human body is able to withstand. It is possible that because of the physical limitations we experience, humans may perhaps never be able to truly comprehend the vastness of space, even with all the telescopes, satellites, space shuttles, space stations, and other remarkable technology devised to study the outer reaches of our galaxy.