- in-order to escape Earth’s gravity, a spacecraft must be launched a particular velocity (speed and direction).
- minimum velocity needed for a spacecraft to combat gravity and stay in orbit around the Earth is called the orbital velocity.
- when a spacecraft reaches 140% of the orbital velocity, it can break free of Earth’s gravity – this is called the escape velocity.
- the trust (push) that launches a spacecraft comes from powerful rockets called launch vehicles.
- launch vehicles are divided into sections called stages, which fall away as their task is done.
Launch Vehicles – Stages
- first stage
the first stage lifts everything off the ground, so its thrust must be greater than the weight of the launch vehicle plus the spacecraft – falls away a few minutes after take off.
- second stage
the second stage is then needed to accelerate the spacecraft towards space; after the two launch stages fall away.
- third stages
the third stage put the spacecraft into orbit, staying in orbit 125 miles above Earth – a spacecraft flies at more than 5 miles per seconds.
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