Risks of Space Travel
When a spacecraft (or any other object) enters the Earth's atmosphere, it experiences a dramatic range of Forces, Temperatures and Pressures. All of these have the capability to injure or kill astronauts, and so spacecraft designers have to go to great lengths to build craft capable of withstanding these conditions.
Effect of Temperature
When a object enters the atmosphere, it can be travelling at incredibly high speeds (Orion will re-enter at over 20,000 mph), which when passing through the increasing dense air, will cause the spacecraft to reach incredibly high temperatures (over 2,200 K). Without protection, the spacecraft would burn up on re-entry, and so the spacecraft has to be protected using a heat shield.
A Spacecraft's heat shield consists of thousands of small tiles made of fibre-glass, epoxy resin and other heat resistant materials. The heat shield protects the spacecraft due to its very high Specific Heat Capacity. This means the tiles can absorb a large amount of Heat Energy, preventing the capsule itself from overheating.
The tiles are also ablative, which means they are designed to burn off during re-entry, which takes more Heat Energy away from the spacecraft itself.
The video below shows a brief description of the science of heat shields.
Calculating the Effects of Re-Entry
When a spacecraft enters the atmosphere, it loses an incredible amount of Kinetic Energy, which following the law of conservation of Energy, is converted into Heat Energy.
The following calculation allows the change in the spacecraft's Temperature to be found:-
1. Calculate the loss of Kinetic Energy (1/2mvu2 - 1/2mvv2).
2. Loss in Kinetic Energy = gain in Heat Energy.
3. Use Eh = cmΔT to find change in Temperature.
A spacecraft of mass 5000 kg enters the atmosphere at a speed of 1000 ms-1 and is slowed by the atmosphere to a speed of 300 ms-1. If the Specific Heat Capacity of the materials used to build the spacecraft's heat shield is 12000 Jkg-1°C-1, what is the temperature increase of the heat shield?
Lost Ek = (0.5 x 5000 x ( 1000 )2 ) - ( 0.5 x 5000 x ( 300 )2)
Lost Ek = 2.5x109 - 2.25x108
Lost Ek = 2.275x109 J
Eh = cmΔT
ΔT = Eh / cm
ΔT = 2.275x109 / (12000 x 5000)
ΔT = 38 °C
The Dangers of Space Flight
As can be seen above, one of the major challenges of space flight is building a spacecraft that can withstand the heat of re-entry. This requires the use of materials and shapes to reduce the Heat transfer to the craft itself.
This is, however, not the only risk of space flight. In order to withstand the extremes of temperatures and pressures experienced in space, specialised protective suits must be worn. The image below shows how the Apollo-era spacesuit was designed to protect its wearer:-
The video below shows the effect of exposure to space on the human body.
Dangers of Space Flight Case Study : Space Shuttle Columbia
On February 1st, 2003 the NASA Space Shuttle Columbia was destroyed during re-entry of the Earth's atmosphere, with the loss of all seven astronauts on board. The images below show the Columbia during its final take off, as well as a close-up of the section of foam that became detached during launch.
During take-off, a small section of the protective foam from the shuttle's main fuel tank broke free and struck the underside of the Space Shuttle. This impact most likely caused a 15-20cm diameter hole in the protective heat shield (black sections of above images). This foam detachment was observed on the launch cameras but at the time, the damage was not understood and it was decided to continue with the mission as normal.
Upon re-entry, this hole in the heat shield allowed superheated gases (at temperatures over 2,200 C) to enter the wing of the shuttle, causing the shuttle to break apart whilst travelling at speeds of ~Mach 19, killing all on board.
The video below shows footage of the foam Impacting the Shuttle as well as recreations of the likely effects:-
As an Astronaut, you would join a special group of people who fly into space to do scientific research that reveals more about our universe.
You’d train to be a spacecraft pilot or a member of the crew with the European Space Agency.
The job means that you'd probably spend several months on a space station such as the International Space Station (ISS).
You’d maintain and repair the space station to make sure that the environment on board will keep you and your fellow astronauts alive.You also carry out scientific experiments. For example, you might look at the effects of weightlessness on the body or how low gravity or ‘microgravity’ affects processes like crystal growth.You could also be doing Extra Vehicular Activity or ‘spacewalks’ to repair the spacecraft or complete research experiments.
Around two and a half hours a day would be used for exercise to counter the effect of the low gravity on your muscles and bone density. Living conditions will be cramped and you'd need to meet the challenge of sleeping, eating and washing in the same environment.
When you’re not on a mission you could spend time keeping your skills current, and promoting space exploration and human spaceflight. This would be through activities like educational events, talks and magazine interviews.
Astronaut with NASA
Astronaut with the ESA
A Career as an Astronaut
Salary: from £48,800 per year
Astronaut working hours: On a mission you would work to a set schedule. This would tell you what time to wake up, go to sleep and the tasks you would carry out each day.
Typical entry requirements: Space agencies such as NASA, the European Space Agency (ESA) and Roscosmos recruit a new astronaut class every four years - competition is fierce.
You would need to be highly skilled in a relevant technical or scientific field.
This could include a background in scientific research or as a pilot. You would usually be educated to scientific postgraduate/doctorate level (SCQF Level 11/12).
You would also need to pass rigorous physical and mental health tests.
The UK Space Agency is a member of the ESA so British citizens can apply to become ESA astronauts.
Alternatively, you can gain relevant flight experience and scientific/engineering qualifications within the Royal Air Force.
Working with technology
Attention to detail
Developing a plan