Posted in Science & Nature

Bird Strike

An airplane flying across the sky faces many dangers. But a very common yet not well-known type of accident is the bird strike. Just as the name suggests, a bird strike is when a plane collides with a flying bird. This may not sound so dangerous, but considering a plane typically flies at 800~900km/h, the energy from the collision is quite significant. If a plane flying at 800km/h collides with a 5kg bird, the energy generated is 92 tonnes. This is not only enough to instantly kill the bird, but also enough to damage the plane.

The most common type of bird strikes is when a bird collides head-on with the windshield or gets sucked into the engine. The latter can cause severe damage to the engine and even cause it to fail. For example, in 1960 a plane flying above Boston collided with a flock of starlings, leading to all four of its engines failing and causing it to crash, killing 62 passengers. Since birds typically fly below an altitude of 9000m, bird strikes most often occur during take-off and landing. However, there are case reports of much higher altitude crashes, with the record being held at 11300m.

According to statistics, the most common type of bird involved are waterfowls and gulls, with 15% of bird strikes being severe. Bird strikes cause $1.2 billion worth of damage annually worldwide and has cost 200 lives since 1988. The first bird strike occurred with the invention of the airplane, as recorded by the Wright brothers (inventors of the modern airplane). As bird strikes cause so much damage, airports place many countermeasures to prevent them. The most frequently used methods are driving away birds from runways by using scarecrows and other methods, or modifying the plane and engines to be more bird-resistant.

Posted in Science & Nature

Nuclear Explosion

Nuclear weapons are quite possibly the most dangerous weapons mankind has ever developed. Through the use of nuclear fission, atoms are split to release the massive amounts of energy contained within, causing a gargantuan explosion. When a typical nuclear bomb detonates, energy is released in various forms: blast energy (40~50%), heat (30~50%), radiation (5%) and fallout (5~10%). The distribution of the energy varies according to the type of bomb (e.g. neutron bombs produce significantly more radiation than heat and blast energy).

The initial damage that follows a nuclear explosion is from the blast energy, much like a conventional weapon. The sheer amount of kinetic energy creates a shockwave that pulverises everything in its path, travelling at speeds over 1000km/h. In addition, the heat from the explosion, over ten million degrees celsius at one point, causes vaporisation of all matter within a certain radius, causing a massive release of gases, fuelling the shockwave from the expansion. In the case of the bomb that destroyed Hiroshima, all structures within 1.6km were vaporised and those within a 3.2km radius suffered moderate to severe damage. A modern nuclear weapon is at least tens of times more destructive and will affect a significantly larger area.

At the same time, thermal radiation spreads out in all directions much like sunlight. Thermal radiation travels far further than shockwaves and can cause severe burns and eye injuries (flash blindness) to people in the vicinity (if they are close enough, they will spontaneously combust or melt). Near ground zero (point of explosion), a firestorm may erupt from the sheer amount of heat energy, as observed as a fireball. 

Next comes the indirect effects.
Ionising radiation is produced when atoms are split and these have detrimental effects on living organisms. Not only are they responsible for mutations in the genome, leading to deformed offspring, sterility and cancer, but if there is sufficient radiation, a person will immediately die from acute radiation poisoning.
The same radiation, especially gamma rays, creates what is called an electromagnetic pulse (EMP). EMP is caught by metal objects and induces a high voltage surge, destroying unshielded electronic devices. Sometimes, nuclear bombs are detonated at very high altitudes so that only the EMP affects the ground, damaging enemy communications and destroying entire power grids.
Lastly, radioactive material rains from the sky for long periods of time, also known as fallout. Fallout causes continuous radiation damage in affected areas.

A nuclear bomb is truly a weapon of mass destruction as it utilises various forms of destruction to devastate all life forms within an area spanning several kilometres, even killing over the course of time in the form of radiation.