A spacecraft that takes off on a runway, with rocket engines that do not require external oxygen, seems like a safer approach to get off the ground than being strapped to a controlled explosion.
In: Physics
Going up to space is not hard, the problem is to move sideways so you do not hit the ground when gravity is pulling you towards the earth.
The international space station ISS is a low earth orbit at 400km above the earth. You need to go sideways at a speed of 7,4 km/s to orbit earth there so the rocket needs to accelerate you to that speed parallel to the ground.
You also need to go up there against gravity and through the drag of the atmosphere. The getting up part is like accelerating to 2km/s.
So a total acceleration of 9.4km/s is required to go to ISS. 2/9.4=0.21 so 20% if the acceleration the rocket does is to go up and 80% is used to move fast sideways.
So Virgin’s spaceplane can be smaller than the rocket used to reach orbit because it only needs to do 20% of the work. 20% of the work do not mean the rocker is 20% of the size it will be a lot smaller. Rockets are the primary fuel, were are talking of over 90% fuel by mass. So most fuel initially is used to lift fuel that you need later.
Neither a rocket to ISS or Virgin’s space plane escapes earth’s gravity only problems that are sent to other bodies in the solar system can be considered to have done that. The gravity at ISS altitude of 400 km is 90% of the gravity at ground level, ISS is in freefall it has not escaped earhts gravity The Viring space plane only to go to 100km
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