Wednesday , February 24 2021

Try landing on Mars in InSight (without explosion)

NASA, Mars, left InSight ashore. Yes, Mars. It's a pretty big deal since a few Mars missions didn't do it. I'm very excited about the missions to Mars.

For this particular task, the earth protected by a heat shield used Mars to slow the atmosphere. After that, he placed a high-speed parachute to further reduce the speed. Finally, the land separated from the parachute and traveled to the last part of the journey using rockets to control the landing.

Now, for the real question, though: Can you be responsible for the InSight landing? What if you made a manual landing? Let's find out.

Before going into the game, let's go to basic physics. Keep this manageability, I'm focusing on the rocket-driven landing section of this mission. During the landing of the spacecraft, there are basically two forces acting on it. There's a downward force and an upward force from spacecraft rockets. The force of gravity only depends on the local gravity field and the mass of the spacecraft. In Mars, this gravitational field is slightly lower than the Earth, about 3.71 Newtons per kilogram (compared to 9.8 N / kg worldwide). This gravitational field is essentially constant at power as long as you are close to the surface of Mars.

Although the gravity field is constant, it is not the mass of the spacecraft. Because he uses his rockets, he loses mass (because the rocket engine works by pulling fuel). This means that the force of gravity also changes a little – but of course the entire spacecraft is not made of fuel. The total mass of the fuel is only 16 percent of the total mass.

The changing mass of the spacecraft also has an effect on its movement. According to the momentum principle, the total force (gravity plus rocket) is equal to the momentum change rate. However, momentum is defined as the product of mass and speed. Thus, a constant net force on the spacecraft means a momentum that changes at an unstable speed because the mass changes. Yeah, it's getting hard.

Okay, let's get into the game. Here's how it works.

  • Start with the spacecraft that is completely fueled and 50 meters above the ground.
  • Set the rocket thrust.
  • The change in rocket speed depends on the amount of thrust.
  • The change in fuel mass depends on the amount of rocket thrust.
  • If you want the rocket to reach the ground while traveling less than 1 m / s (actually it should be slower).

This much. Click "run" to get started and then adjust the slider underneath to launch the rocket. The program also shows the vertical speed and the amount of fuel you have left. This is a dimensional version of the classic video game – Lunar Lander.

It's harder than it looks. The problem is that when we consider the direct connection between force and motion, we make a larger force move faster. Aha! Not too fast. In fact, a larger force makes a larger CHANGE in motion. As the Lander moves down, you must increase the power to prevent it from accelerating as it falls. But if you give a lot of thrust, the land slows down so that it actually accelerates in the opposite direction. This isn't landing – it's leaving.

Now for some homework. Find out if you can safely bring your vehicle to ground (safely). Now, try creating an algorithm for the magnitude of the pushing force (not controlled by the user) that provides the shortest time. It will be fun.

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