A brief history of space
After the launch of a new US spaceplane and plans for a mission to Mars within the next few decades, we take a look at outer space.
A brief history of space
As late as the 17th century it was assumed that space could not be empty, and René Descarte argued that the entire universe must be filled. This was gradually shown to be wrong through work on air pressure by Blaise Pascal, Florin Périer and finally Otto von Guericke, who demonstrated that the density of the Earth’s atmosphere decreases with increasing altitude, and concluded that there must be a vacuum between the Earth and the Moon.
Astronomers began to get an idea of the scale of our galaxy in 1838 when Friedrich Bessel made the first successful measurement of the distance to another star, working out that 61 Cygni is more than 10 light years away. What we now know to be other galaxies were thought to be contained within our own galaxy until 1923 when Edwin Hubble measured the distance to the Andromeda galaxy.
Getting to space
The boundary of where space begins is not well defined. A common working definition is the Kármán Line at a height of 62 miles. This is where an aircraft would have to travel at a speed greater than orbital velocity to get enough lift from its wings to stay in the air.
The US defines an astronaut as someone who has flown above 50 miles, while NASA use 76 miles as their re-entry altitude, the point at which atmospheric drag is noticeable and the space shuttle can switch from steering with thrusters to maneuvering like a conventional aircraft.
In 1903, Konstantin Tsiolkovsky became the first person to realise that getting to space using chemical fuel would require a rocket made up of multiple stages. The idea was developed further by Herman Oberth 20 years later in his thesis By Rocket Into Planetary Space.
To achieve orbit, the horizontal velocity is as important as the altitude. To stay in orbit at the Kármán line requires a speed of around 18 000 miles per hour. It takes 20 times more energy to gain enough speed for a low-earth orbit than to simply climb to that altitude. A German V2 rocket was the first to cross the Kármán line during a 1944 test flight, and in 1957 the Soviet satellite Sputnik 1 became the first man-made object to orbit the Earth. This was followed in 1961 by Vostok 1, in which Yuri Gagarin made the first human spaceflight.
Space travel in the near future
Until recently, only governments had the necessary resources to reach space. The first privately funded human spaceflight took place in 2004, when SpaceShipOne, developed by Mojave Aerospace Ventures, reached more than 62 miles twice in two weeks to win the $10m Ansari X Prize. The technology was then licensed by Richard Branson’s Virgin Galactic, which plans to build a fleet of five spacecraft twice as large as the original, offering commercial trips into space for an initial price of $200 000 each.
Meanwhile, the US Air Force launched its X-37B test vehicle on April 22 as part of a programme aimed at developing a reusable space vehicle to succeed the space shuttle, and President Obama has predicted that astronauts will reach Mars by the middle of the 2030s.