In order to overcome the gravity of the earth, the space shuttle must accelerate to a speed of more than 40 thousand kilometers per hour.
In order to make the space shuttle fly quickly, it is necessary to reduce the weight as much as possible. For decades, engineers have racked their brains to solve the weight problem of aircraft. Because fuel accounts for the vast majority of the weight of booster rockets, the best solution is to use a lightweight and ultra-efficient propellant.
The new generation space shuttle will not carry a lot of liquid oxygen, but will absorb the oxygen in the atmosphere at supersonic speed at any time, then compress it, and then use special gas cylinders to make the oxygen burn with the liquid hydrogen carried by the space shuttle itself. After accelerating to several times the speed of sound, the plane will rise vertically into orbit. This novel engine design is called "supersonic ramjet"
In addition to reducing fuel carrying capacity, reducing the weight of the space shuttle itself is also a feasible way. At the end of the 20th century, American scientists designed a light space shuttle that could be put into orbit by single-stage propulsion.
This space shuttle is made of graphite and epoxy resin, and its weight is less than half that of a conventional space shuttle. However, in the test conducted by 1999, the wall of the hydrogen fuel tank made of this material broke. After spending more than $654.38 billion, people can only be forced to give up the plan.