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
The Virgin craft basically acted like a ballistic missile. It fired up, coasted up as far as the rocket burn would take it, then fell down. It did not get out of gravity, for gravity clearly pulled it back down.
Other space craft need to get into orbit, so they need to get up to higher speeds to avoid falling back down. Higher speed demands more fuel and more power.
Latest Answers