ntuck@neu

03 - To the Mun

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HW03

  • Is posted
  • Goal: Write a script to land on the Mun
  • Three steps:
    • Launch
    • Transfer to Munar orbit.
    • Land

Part 1: Mostly Manual Mun Mission

  • Going to the mun.

Part 2: Keplerian Mechanics

  • Solid video: https://www.youtube.com/watch?v=AReKBoiph6g

Part 3: Mun Mission Problems

Landing Script

You can probalby get away with just landing wherever, and retry if you hit a crazy slope or something.

One strategy is to calculate and execute a perfect "suicide burn", where you burn at full throttle until you hit zero speed exactly when you hit zero altitude.

Another strategy is to set a progressively lower maximum speed as the vessel gets closer to the surface.

We can estimate start time by taking into account thrust, speed, distance, and local gravity.

Example:

  • We're at 100km
  • We're falling at 1000 m/s
  • We're accelerating at 10 m/s^2 due to gravity.
  • We can thrust at 20 m/s^2 up
  • That gives us the ability to slow at 10 m/s^2
  • We'll hit in 100 seconds if we thrust to cancel our acceleration.
  • We can slow to zero in 100 seconds.
  • It's a little early for a suicide burn, but probably a good time to start a more conservative burn.

Transfer to Munar Orbit

Transfer burn:

  • Start: In a low, circular-ish orbit, coplanar with the Mun.
  • First, we want a transfer orbit - where our apoapsis will be in the Mun's SOI when we get there.
  • So we need to burn up our apoapsis to the Mun's altitude.
  • Problem: Where in our orbit do we do the burn?
  • Solution: On the opposite site of Kerbin to where the mun will be when we get to apoapsis.
  • Where will the Mun be? It'll get as much time to move as it takes us to get there.

Orbit burn:

  • Once we get to the Munar SOI, assuming we're not hitting the Mun, we need to circularize at periapsis.