Entry, descent and landing is a part of a spacecraft's mission when it enters the atmosphere, goes down and lands on the surface.
Entry[]
The first part of this phase is well, atmospheric entry. The rocket enters an atmosphere of a planet. During this stage, the rocket heats up, and the velocity starts to decrease. Also in this time at the start of that stage the rocket fires retrorockets to slow down a little bit.
What happens?[]
At the start of this stage, things are quite normal. The rocket is about the temperature of space. Retrorockets are firing. Trajectory correction maneuvers are used for the spacecraft to land on its landing footprint. Then, the rocket heats up, then slows down at it gets deeper into the atmosphere. It glows red (because of ionized plasma), usually at a hot temperature of around 1000 to 3500 degrees Celsius. Heat shields are used to protect the rocket from burning up into the atmosphere. At the end of this phase the velocity goes down drastically.
Descent[]
The second part is, descent. Things are quite different than in the first phase. The velocity drops so fast, that parachutes are now enough to be deployed for further slowdown. This effect is weak on planets with thin atmospheres, such as Mars and Pluto.
What happens?[]
At the early part, the rocket is still slowing down due to the atmospheric drag. Retrorockets continue to fire, and the heat shield is sometimes jettisoned. Usually, the parachute is deployed, to slow down the rocket even more.
Parachute deployment[]
The parachute is then deployed, to slow down the rocket to a safe speed. Sometimes, retrorockets fire even the parachute is deployed.
Landing[]
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The last part is landing. The rocket is now reduced into a safe speed to land. If a rocket has no parachute it uses retrorockets to slow down.
What happens?[]
At the early parts, the rocket is still slowing down to safely land. The landing gear is deployed. Some seconds before touchdown, the rocket is now in the lower parts of the atmosphere. Then, at the moment of touchdown, the parachute cuts, dust on the planet is spreading in all directions, and the phase of landing and the stage of entry, descent landing is done.
Retrorocket Soft Landing[]
The rocket uses fuel to slow down. It must be at the right speed to safely land on the surface, or else it is destroyed.
Landing Gear and Landing Legs[]
At the middle of this stage, the landing gear is usually deployed, for example, landing legs. There are even complex structures than that, for example the airbags, used by the Spirit and Opportunity rovers, the skycrane, which is used to slow down rovers, such as the Curiosity rover, and even more.