Risks of Manned Space Exploration (SQA National 5 Physics): Revision Note

Risks of manned space exploration

• Space exploration poses significant risks for astronauts due to the extreme environments they are subjected to

• Some of these risks include:

  • fuel load on take-off

  • potential exposure to radiation

  • pressure differential

  • re-entry through an atmosphere

Fuel load on take-off

• Launching a spacecraft from Earth requires a large thrust to overcome the Earth's gravitational pull

• To achieve take-off and maintain enough thrust to reach space, rockets must burn a large quantity of fuel

  • At launch, the fuel makes up around 90% of the total mass of the spacecraft

• Risk to astronauts:

  • The rocket fuel is highly volatile

  • Therefore, a small spark or mechanical failure could ignite the fuel and cause an explosion

Photo credit: NASA (opens in a new tab)

Exposure to radiation

• Outside Earth’s protective atmosphere and magnetic field, astronauts are exposed to:

  • cosmic rays (high-energy particles from space)

  • solar radiation (charged particles from the Sun)

• Risk to astronauts:

  • Ionising radiation can damage cells and cause DNA to mutate

  • Therefore, astronauts are at an increased risk of developing cancer or, in severe cases, acute radiation sickness

Effect of radiation on a living cell

Pressure differential

• Inside a spacecraft or spacesuit, astronauts require the internal pressure to be equal to atmospheric pressure (the pressure at sea level on Earth)

• Outside, in space, the external pressure is almost zero

  • This creates a large pressure differential, i.e. the difference between internal and external pressure

• Risk to astronauts:

  • The pressure difference produces a large outward force on the spacecraft

  • If a breach (rupture) occurs, e.g. due to impact from space debris, in the spacecraft's hull or in a spacesuit (during a spacewalk), air would rush out very quickly

Re-entry into the atmosphere

• When a spacecraft returns to Earth, it enters the atmosphere at a very high velocity

• Friction between the spacecraft and the air generates heat energy, which causes the temperature to increase significantly

  • This is because the work done by friction transforms kinetic energy into heat

• Risk to astronauts:

  • If a spacecraft is not protected from the heat, it could suffer a catastrophic failure or 'burn up' in the atmosphere

Heat shielding

• To protect the astronauts and the spacecraft, heat shielding is required

• Heat shields are made from insulating tiles with a high specific heat capacity and a high melting point, which allows them to

  • absorb a large amount of heat energy

  • radiate the heat energy back into the atmosphere

• Heat shields are also coated with a substance with a high specific latent heat, which allows it to

  • absorb a large amount of heat energy without raising the temperature of the spacecraft

  • carry the energy away into the atmosphere as it melts (vaporises)

Heat shielding on the space shuttle