MARS LANDING TUTORIAL FOR SFS


Unlike a Mars Return Mission, a Mars landing mission is cheaper. Depending on the purpose, there can be:
  • Hard Mars Landing (as performed by the first historical probes who landed on Mars);
  • Soft Mars Landing (as performed by most of the spaceships who sent probes and rovers to Mars);
    • Payload Delivery Missions (they bring probes and rovers to Mars);
    • Supply Missions (if you have a space colony and want to expand it).










Basics

Depending on what payload you intend to send to Mars, you will need a larger or a smaller launch vehicle. The Delta-vrequirement for a Mars mission is not too much. Most of the fuel will be spent to reach Low Earth Orbit.
Mars has a small gravity, but a relatively large Sphere of Influence. Because of this, it is not hard to reach the target. After reaching low Earth orbit and entering the Launch Window, there is room for additional Trajectory Correction Maneuvers. In addition, the Martian atmosphere can be used to Aerobrake.
A major disadvantage is that Mars has a rarefied atmosphere, which is unable to slow down a ship completely. In order to do so, a ship needs to use many parachutes or to conduct an engine burn.

The Ship




If the purpose is just to bring a Capsule or a Probe to the surface of Mars, then one can easily use the Spaceflight Simulator Model Ship, which is shown on the desktop icon (top-right image). The ship needs some improvements. The best way to do this, is to remove the top parachute, replace it with a Structural Part and attach 3 parachutes on it. The ship will use its boosters at liftoff, then its first stage to get low Earth orbit. The second stage is more than enough to reach Mars.
If the purpose of the mission is to bring a rover or other supplies for a Mars colony, you have to build a much larger ship.

Landing




There are multiple ways to land on Mars:

Hard Landing

This is the most simple way to bring something down. Just set an impact trajectory. your ship will hit Mars and nothing will survive. Because the atmosphere does not slow down a ship enough, the speed of the impact will be huge. This is an option only when a Space Agency wants to be the first to touch the surface of a planet.

Partially Hard Landing

This usually happens accidentally. The pilot fails to estimate when to fire engines or to estimate the weak effect of an Aerobrake. This will result in a partial destruction of the ship.

Soft Landing

In order to do so, fix the trajectory as a tangent to the Martian surface. This way, the atmosphere will slow down your ship enough to land.
The Martian atmosphere can be used to safely to Aerobrake. By setting the flight path with periastron at 11 km high, a ship will usually be slowed enough to enter orbit. The second time the ship passes through the atmosphere, it might still reach space at apoastron. If you want your probe to become an Orbiter, conduct an engine burn at apoastron. Well, usually during the third pass through the atmosphere, the ship will be slowed enough not to reach space again.
Aerobrake can be used to slow down a ship in another manner. By setting the flight path to nearly touching the Martian surface (a periastron at less than 2 km high), the ship will not escape back into space.
Finally, during the last moments of descent, the ship will need to open its parachutes and/or conduct engine burns.

Fixed Point Landing

See also: Fixed Point Landing.
This is the most challenging part. Before everything, you need to have something on the surface (another ship or a rover, anything that help you pinpoint the landing location).
The ship needs to enter Mars orbit. Then, when the ship is above target, it must turn on the engines and burn retrograde. Repeated course corrections are needed. The effect of Aerobrake is too small and the ship will need to conduct multiple engine burns in order to land safely at the designated point.
The use of a parachute in the last part of the descent can be helpful. Also, the use of RCS Thrusters can be a good idea, to correct trajectory.

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