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.  

The video below shows the conditions NASA's new Orion Capsule will experience during re-entry. 

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 (mass = 200 kg)  is 120,000 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 / (120,000 x 200)

ΔT  = 95 °C

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.