Astronomy Paper on Science Fiction – Manned Mission to Mars

Science Fiction – Manned Mission to Mars

The year is 2030, a time when the earth is in great turmoil. Tsunamis, hurricanes, tornadoes, droughts, famines… all the impacts of global warming are just starting to disrupt life. Europe and North America are experiencing immigration in unprecedented numbers, neither because the migrants are escaping persecution, conflicts and wars in their countries, nor because they are pursuing economic prospects; but because they can no longer survive the high temperatures in their countries. Europe and North America have become too warm for their inhabitants but just the right temperature for migrants from South America, the Middle East, Africa and South Asia to survive. But the problem is not just global warming and migration – there is a more frightening threat, one that could turn the entire Earth’s crust upside down – Nuclear War. All political and diplomatic negotiations have failed, leaving war as the last resort. There is not a single safe spot on earth to escape to.  There is only one option left –a place outside earth, a different planet – Mars.

The possibility of relocation to Mars comes as big relief to people on earth, but there is one problem – not everybody can go. The mission is too expensive for ordinary people. Only billionaires and politicians who have stolen (and are still stealing) funds that belong to their states can afford it. However, the good news for a few lucky people is that there are going to be at least two missions. The billionaires and the other rich are going to be the last lot to leave the earth, after at least one mission has been tested and found to have successfully and safely been accomplished. In other words, there is a chance for ordinary people to go, and the rich are willing to pay for it. A lottery is drawn and a few people are lucky to be used as guinea pigs.

The spacecraft is launched at a secret location in the United States to protect it from any potential attack by foreign powers, both physical and cyber. As the chosen few enter the rocket, their hearts beat hard from anxiety and fear. No one knows what lies ahead. But they have to make use of this opportunity. They all enter it and the entrance is sealed. They sit quietly inside, waiting for whatever is supposed to happen next.

About an hour passes and rocket thrusts into the atmosphere, releasing behind it a thick and explosive stream of burning fuel. The velocity and mass of the fuel is high enough to give the rocket a high enough momentum to acquire a velocity that is close to earth’s escape velocity. Escape velocity is the minimum velocity a body needs to escape the gravitational force of a massive body, for example earth (Turner, 2004). In the case of the earth, the value of escape velocity is 40270 Kilometers per hour (Turner, 2004). If the rocket (or any other body) is launched at this velocity, it will acquire enough kinetic energy to cancel out the earth’s gravitational potential energy, which means that it will not need any additional thrust. The engineers are aware of this concept, but because of some engineering constraints, they were not able to design the rocket to achieve the earth’s escape velocity. That means that the rocket is going to need some fuel propulsion to help it escape the earth’s gravity. While it is a disadvantage that because of the technological limitation the rocket is using up fuel, it is good thing because the engineers don’t want the rocket to escape the earth forever, but they want the earth’s gravitational force to hold it in orbit for some time.

However, they don’t want the rocket to use up too much fuel in the early stages of the mission. To take care of the problem, the controllers on the ground make the rocket detach and drop some of its parts. In effect, the mass of the rocket reduces. The reduced mass is now easily propelled by the rocket’s jet of burning fuel. This action reduces the rocket’s fuel consumption. The process is repeated a number of times until the rocket reaches a region above the earth’s atmosphere where the effect of the earth’s gravitational force is minimal. Just as the rocket gets in orbit around the earth, the final part of the rocket is released, leaving only the spacecraft in orbit.

While the rocket is in orbit, the crew experience weightlessness, an effect called zero gravity. The spacecraft itself is not experiencing zero gravity. In fact, the spacecraft is held in orbit by the gravitational force of the earth. The earth’s gravitational force acts as the centripetal force in the spacecraft’s circular motion around the earth, preventing it from escaping into the interplanetary space (Turner, 2004). The spacecraft is actually constantly “free-falling” towards the earth, but its range is so large that it never actually gets closer to the earth’s surface, resulting in its orbital motion. The crew in the spacecraft, however, experience weightlessness. The sensation of weightlessness results from the fact that the rocket is experiencing “free-fall”, and that there is no relative acceleration between the crew and the spacecraft (Turner, 2004). The spacecraft now uses the fuel to maintain the orbit, and to steer and guide the spacecraft, helping it avoid collisions with space wastes in the thermosphere. The spacecraft spends a number of months in orbit.

Wastes from used satellites and other spacecrafts are not the only problems in the thermosphere, which is the part of the atmosphere in which the spacecraft is orbiting the earth. Owing to solar maximum, the spacecraft experiences atmospheric drag, which threatens to drift it away from its orbit and cause a reentry into the earth. It has been observed that the sun’s level of activity varies periodically every eleven years, with the two extremes being solar maximum and solar minimum. Some of the solar activities that change periodically every eleven years are: number of sunspots, amount coronal mass ejections (CME’s), number of solar flares, and levels of solar radiation (Feynman& Gabriel, 2000). The levels of these activities are at their highest at a certain time during the solar cycle, called solar maximum. Due to high solar radiation at this time, the temperature of the thermosphere is double, thus extending the thermosphere and consequently increasing the thermosphere’s density at higher altitudes (Feynman& Gabriel, 2000). This is because the particles and ions in the thermosphere have acquired enough kinetic energy to move upwards and in other directions.  The increased density increases the amount of drag on their spacecraft, threatening to lower its altitude and drift its orbit.

But being drifted from the orbit is not the main problem here. Things could get worse. If the drag is too much, the spacecraft could not just drift away from its orbit, but it could renter the earth. The problem with reentry is that the spacecraft could either burn in the atmosphere or crash onto the surface of the earth. They contact the space station on the ground to inform them that the spacecraft is not moving smoothly due to turbulence in the thermosphere, and they are assured that something is being done about the matter. They don’t know what is being done but they hold their hearts, counting on hope that the impending catastrophe will be averted. Days later, the spacecraft leaves its orbit and rises higher, entering the upper less dense part of the thermosphere.

The fact that they have their spacecraft has risen to the higher less dense part of the thermosphere does not mean that they have escaped the impact of solar maximum. In fact, the rise has just subjected them to an equally dangerous problem – solar flares. Solar flares are very bright flashes, occasionally visible near the solar surface. Solar flares emit atoms, ions and electrons into the interplanetary space at very high energies (Feynman& Gabriel, 2000). On average, solar flares release energy in the range of 1020 joules (Feynman& Gabriel, 2000). These amounts of energy are high enough for solar flares to impact the earth, especially the earth’s upper atmosphere. The fact that the sun is at its solar maximum and the spacecraft is in the upper thermosphere means that their spacecraft is more susceptible to the effect of solar flares. They get a call from the ground station, asking them to turn on the spacecraft’s cameras. They deploy the cameras as instructed and wait for whatever fate has in store.

As their spacecraft is just about to leave the upper thermosphere, it charges directly into a visible aurora, which consequently switches off the spacecraft’s communication system. With no connection to the ground, they can neither communicate with the ground, nor have their spacecraft controlled from the ground. They stare at each other in disbelief, without a word, thinking they are dead and done. As if by a miracle, the communication system switches on, and they count themselves lucky. There is however one thing to worry about –the direct exposure to the aurora has not just disrupted the spacecraft’s communication system, but the exposure is also likely to damage their cells and DNA, and cause radiation sickness (Feynman& Gabriel, 2000). Nobody asks if the people on the ground did it on purpose.

Three weeks after their spacecraft rose to the upper part of the thermosphere, some to the spacecraft’s engine fire, making the rocket leave its orbit and rise into interplanetary space. The spacecraft crosses the magnetopause – the boundary between the earth’s magnetic field and the solar wind – and they plunge directly into the solar wind.  The solar wind is a flux of ions emanating from the corona (or the sun’s outer atmosphere) at a speed close to that of sound (Feynman& Gabriel, 2000). The solar wind does not impact the earth because the earth is protected by the earth’s magnetic field. The wind of charged particles generates its own magnetic field due to the particles’ acceleration, and the earth’s magnetic field repels the magnetic field generated by this solar wind, creating a boundary between the two fields, called the magnetopause (Feynman& Gabriel, 2000). The magnetopause was responsible for protecting them against the direct effects of the solar wind (though it could not protect them from auroras and coronal mass ejections), but now their spacecraft has to inevitably cruise through it. The crew is aware of this danger, and they hold their hearts, hoping that the new part of the journey does not end in a catastrophe.

As they cross the magnetopause and plunge into the solar wind, they are surprised that nothing happens. Suddenly, they get a call from the ground informing them that they have activated the spacecraft’s magnetic field, and that they are calling to find out if the activation has gone right. Their spacecraft is shielded from the solar wind, in the same way that the earth’s magnetic field shields it from the solar wind. At first no one talks back into the phone, but when they realize that silence would make the people on earth think that they are dead, and hence cut communication, they call them to say that they are alright, except that, considering the length of the journey left, they are running out of fuel. The people on the ground giggle on the phone and hang up.

They are scared when a number of engines switch off, but also wonder why an accident is not happening. It happens that the controllers on the ground have turned the spacecraft’s engines off, and intend to exploit gravitational slingshot. Gravitational slingshot is a method of probe propulsion. The method exploits the gravitational force due to asteroids, moons and planets to accelerate, decelerate and steer the spacecraft (Van, 2003). The method achieves propulsion by exploiting the gravitational pull of other heavenly bodies, and maneuver by exploiting the distances and configurations of those bodies. This method therefore does not require fuel. The people on the ground did not bother to explain it to them, and they do not seem to mind what is going on, as long as they are alive. Instead, they are glad that fuel is being saved as they know they are probably going need it at some point along the journey. The spacecraft spends months maneuvering in the interplanetary space, waiting for the opportune moments to approach Mars.

As they finally approach Mars, they start to become conscious of time and notice the difference.  In fact, they are in a “time zone” called Mars time. Mars time is time as it is experienced in Mars. Mars takes about forty minutes longer to rotate about its axis, compared to earth (Dehant, Lognonné & Sotin, 2004). This defines a solar day in mars as approximately 24 hours 40 minutes. This means that a solar day on mars is 40 minutes longer than a solar day on earth. This time difference does not mean much to those in the spacecraft, but those on the ground have to take this time difference into account. The controllers on earth adjust their schedules accordingly to make sure that the landing takes place properly.

Their spacecraft is guided into the Martian atmosphere using the same gravitational slingshot propulsion technique. Deimos and Phobos provide the necessary gravitational force this time. The celestial bodies are Mars’ moons. The two small moons are believed to have been once asteroids, until they were captured by Mars. The controllers on the ground know that the motions of the two moons are different compared to the Earth’s moon. Deimos’ revolution around Mars is almost synchronous to Mars’ rotation, and rises slowly in the east (Dehant, Lognonné & Sotin, 2004). On the other hand, Phobos , contrary to Deimos, rises in the west and sets in the East, only to re-rise after only eleven hours (Dehant, Lognonné & Sotin, 2004). The controllers on the ground need to know the relative motions of the two moons to be able to predict their positions at any given time, and thus properly guide the spacecraft into Mars. Hoping that their calculations and predictions are right, the controllers on earth hold their breath and try their best to steer the spacecraft.

Just as the spacecraft approaches the Martian atmosphere, it sheds off more than a half its weight. The detached part is mainly the part of the spacecraft that has overheated due to friction against interplanetary matter during its millions of miles of travelling through space. The aircraft becomes lighter, which is a good thing because it now needs to switch from gravitational slingshot to fuel propulsion for its entry into mass. The fuel is used to guide the spacecraft rather than propel it. For its entry into Mars, it depends on the gravitation pull of the planet.

The spacecraft enters and descends into the Martian atmosphere at a speed of 12000 miles an hour (Turner, 2004). This high velocity causes a very high friction between the spacecraft’s heat shield and the Martian atmosphere, raising the temperature of the heat shield to approximately 1447 Degrees Celsius (Turner, 2004). But the people inside the spacecraft don’t suffer from the heat. The heat shield has just enough sufficient heat capacity to protect the spacecraft from overheating, helping maintain the temperature inside the spacecraft at room temperature. A part from shielding the people in the spacecraft from heat, the heat shield also functions as a break – the friction between it and the Martian atmosphere partially counters Mars’ gravitational force, and thus slows down the spacecraft’s descent into the planet. It takes the spacecraft a few minutes to slow down to about a thousand miles an hour, at which point the spacecraft releases its enormous parachute. The heat shield, having done its function, is released a few seconds after the deployment of the parachute. The spacecraft finds itself on the Martian surface in a matter of minutes, safe and intact, with everybody inside alive and uninjured.

The crew in the spacecraft stares at the vast surface of Mars through the thick transparent windows of the spacecraft. They had heard Mars referred to as the red planet, and now they could see it with their own eyes. The surface of the planet looks like a large rusted iron surface. The red appearance of Mars is due to the abundance of iron oxide on its surface, giving it that rusty red color that resembles rusted iron (Dehant, Lognonné & Sotin, 2004). They are not able to test if that is true because they don’t have the instruments to do so. Besides, they cannot get out of the spacecraft because Mars’ atmosphere does not have enough oxygen. The Martian atmosphere is made up of 1.89% nitrogen, 1.93% argon, 96% carbon dioxide, and only traces of oxygen and water (Dehant, Lognonné & Sotin, 2004).  It is safe for them to stay inside the spacecraft, using up the oxygen stored in the tanks inside. In the distance, the crew members can see something that looks like a very tall mountain on the surface of the planet. They think it might be Mt. Olympus, the volcanic mountain in Mars they had learnt about in school. They can see it from inside the spacecraft. Mt. Olympus is about three times as high as Mt. Everest (Dehant, Lognonné & Sotin, 2004).

They are left stranded in the spacecraft, not knowing what do and wondering what fate has in store for them. They are not just running out of oxygen gas as time passes, but they are also eating more and more of the limited stock of food they have in the spacecraft. They wonder if there will be any help soon. In fact, they don’t know if there will be any help at all. Somebody calls from earth. They hesitate to pick up but on second thought, they do. They know that if they ignore the call, they will be assumed to be dead and therefore there will be no help. As they expected, the caller is only interested in finding out if they have survived the journey, and whether everyone is alive, and then hangs up. No one knows what awaits them, and they think that it is better not to think about it. They sit quietly, breathing and eating, leaving everything to nature to take its course.

 

References

Dehant, V., Lognonné, P. & Sotin, C. (2004). Network science, NetLander: a European mission

to study the planet Mars. Planetary and Space Science52(11), 977-985.

Feynman, J. & Gabriel, S. B. (2000). On space weather consequences and predictions. Journal

 of Geophysical Research: Space Physics105(A5), 10543-10564.

Turner, M. J. L. (2004). Expedition Mars. London [u.a.: Springer.

Van Allen, J. A. (2003). Gravitational assist in celestial mechanics—a tutorial. American Journal

 of Physics71(5), 448-451.