Hard Landing

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**Hard landing** is a type of landing when an aircraft or spacecraft impacts the ground without significantly reducing velocity. Hard landings are usually high-velocity impacts, which can damage part or all of the aircraft/spacecraft.

## History

During the Space Race, the Americans and the Soviets performed hard landings on the Moon, Mars and Venus. The goal was to be the first to touch the surface of a celestial body.

Today, a hard landing is practiced when a spacerocket reaches the end of its lifetime. A spacecraft deorbits into the celestial body it was analyzing. This was what happened with the *Rosetta*, *Galileo*, *Cassini*, and *MESSENGER* spacecraft, and many others.

## Principle

A hard landing only requires a trajectory that intersects the surface. For planets with atmospheres, a hard landing is near impossible because a rocket will burn up into the atmosphere. Some pieces of the spacecraft may survive and impact on the surface.

Depending on the strength of gravity and atmospheric drag, the rocket may be completely destroyed or partly damaged.

### Jupiter

Jupiter has a very dense atmosphere and is not advised to aerobrake, even in the cloud tops. A spacecraft entering the atmosphere of Jupiter will certainly break up into bits because of the high velocity. Just like the sun, Jupiter has a liquid surface and any spacecraft (that survived entry) will not find something solid and eventually be destroyed by the intense forces. However, it is still useful to use Jupiter's atmosphere for aerocapture for orbiter missions.

#### Galilean moons

Because the Galilean moons are positioned in a low orbit around Jupiter, the spacecraft will most likely be destroyed. The other moons (Europa and Callisto) have low gravity, so there will be some form of debris surviving after the impact.

### Mars

Because Mars has a rarefied atmosphere, it will burn up; but still, some pieces may get to the surface. Rockets on an impact trajectory will be likely get destroyed by the atmosphere and/or the surface.

#### Mars's moons

For the little moons of Mars, a probe that is being deorbited will suffer some damage after impact, but much of it will remain intact. If a rocket hits one of the moons at great speed, the rocket may be completely destroyed.

### Earth

The Earth has a strong gravitational pull. All lower stages of a rocket are destroyed as they impact/burn up into the atmosphere of the Earth. On Earth, a hard landing is a way to get rid of failed rockets.

#### Moon

It is possible to send a space probe to the Moon and ensure that something might survive (some parts, not astronauts).

To perform a hard Moon landing and survive, the probe must be encircled by protective devices able to absorb the shock of impact. Struts and wheels are best for this. If the probe lands in an angle, it will bounce back into space and crash again. If this is the case, rotate the rocket so that another part will absorb the next impact. If the probe falls towards the Moon on a straight trajectory, rotate it so that the weakest part (fuel tanks and engines) will impact first and absorb the shock of impact.

### Venus

Venus is not an excellent destination for hard landings, as its dense atmosphere will destroy any rocket quickly and will most likely be disintegrated to atoms. Some pieces may survive after it enters the atmosphere. Even if a spacecraft survives entry into the Venusian atmosphere, after a hard landing, there is something left from a rocket that survives impact.

### Mercury

Usually, there will be nothing left after a Mercury hard landing, because Mercury is close to the sun, increasing the Sun's gravitational pull. This is also the reason that Mercury is hard to explore.

### Sun

On the Sun, hard landings are impossible. Any rocket will melt by getting close to the sun.

## Bugs

Sometimes when impacting the rocket will go straight through the terrain (only on celestial bodies that have solid surfaces and if the rocket has a high speed).