Before we go into details about space travel, we have to first take into account, the hindrances to space travel. This is essential because, the problems posed in launch of the space vehicle to be sent to space, plays an important role in the selection of appropriate fuels, method of producing energy for launch, the design of the vehicle and so on. So, before we start, let us study the problems faced in escaping earth.
1) Earth's Gravity
The first and foremost problem to be dealt by any man aspiring to start on his voyage to space is gravity.
Earth is a pretty massive object and thus any object on the surface of the earth (irrespective of its size) experiences a very large pull by earth and hence virtually remains bound to earth.(see - Newton 's gravitational law)
So as to break these bonds with earth, the object attempting to leave earth must be given a certain velocity called as the escape velocity. (See physics world)
The value of escape velocity is 2.38 Km/s If the object doesn't attain escape velocity, it will either crash back into the Earth, or orbit around it, as satellites or space shuttles do.
By Newton 's first law, any mass whose motion is accelerated decelerated or has its direction changed will resist this change by developing reaction force.
Additional energy must be supplied to the object, keeping these forces in consideration.
2) Atmospheric Resistance
Another problem encountered while ascent is resistance of atmosphere. Air resists moving objects. As the velocity of this moving body increases, the resistance also increases.
So additional energy (energy that the space vehicle requires for overcoming air drag) must be supplied to it along with the energy required to overcome gravity and to travel in free space.
These problems must be taken into account when the space vehicle is being constructed. Let us now see the materials used in the construction of the vehicle.