For almost the entirety of human history we have been confined to the ground. What does it take to leave our planet and get into space?
Gravity gets us down
Taken almost for granted, gravity is the universal force that holds us onto the planet’s surface. Escaping our planet’s gravitational pull is something we only managed to achieve in the last 200 years. In that time, we have progressed from the Montgolfier Brothers’ paper balloon to the giant rockets we ride into space.
Energy vs elegance
Powered flight through the air was achieved through an elegant balance between airflow and lift and a relatively small input of energy to move along. To get into space we have to sacrifice the airflow and lift generated by the atmosphere. This means that our energy requirements become much greater.
To provide the enormous amounts of energy to push rockets into the air, we use the chemical reaction, combustion. The explosive combination of fuel and oxygen has so far powered all our space exploration.
Combustion’s main advantage over other reactions is its simplicity. If the ingredients are mixed in the right proportions, the resultant reaction can be controlled.
While simple, the use of combustion means we must sacrifice some efficiency. To lift large payloads into orbit requires large amounts of fuel which, is itself, is added payload. Due to this complicated relationship a rocket is generally 85% fuel and just 15% rocket. Most of this material comprises the engines and fuel tanks, leaving usually just 1-4% of the mass available for what you want to send to space. Until recently, almost all these rockets have been single-use: an expensive way to get all our heavier payloads into space.