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Mission 2 · Faults & Safe Mode

Survive the Eclipse

EarthEarth's shadowSunCubeSat · in sunlight

2D drawing · + and − zoom, 0 resets

Illustrative orbit, Sun in the orbit plane.

Educational simulation · simplified physics, illustrative values · not flight data

Learn · step 1 of 2

Orbit and shadow

Goal: Change the altitude and see how long each orbit, and each eclipse, lasts.

500 km
One orbit
94.5 min
In shadow
35.7 min
Share in shadow
38%
Orbital period
T = 2π × √(r³ ÷ μ)
r = 6,371 + 500 = 6,871 km → T = 5668 s = 94.5 min
T in seconds · r from Earth's centre in km · μ = 398,600 km³/s² for Earth

Higher orbits are bigger circles travelled more slowly, so each lap takes longer.

Share of the orbit in shadow
f = asin(R ÷ r) ÷ π
= asin(6,371 ÷ 6,871) ÷ π = 0.378
R = Earth's radius, 6,371 km · r = orbit radius · f as a fraction

Earth blocks the Sun for part of every orbit. From higher up, Earth covers less of the sky, so a smaller share of the orbit is in shadow.

As the satellite flies higher, the share of each orbit spent in shadow…

About this mission

Keep a CubeSat's battery alive through Earth's shadow: size the power system, read live simulated telemetry, inject faults and use safe mode.

You will

  • Find the orbit period and eclipse length
  • Size the battery and watch three orbits
  • Inject a fault and recover with safe mode

Concepts in this mission

  • Orbital period
  • Eclipse fraction
  • State of charge
  • Safe mode and hysteresis

Part of the Faults & Safe Mode track, with its course description and a lesson plan for each age level.

About the model

An educational simulation, not a validated engineering tool. The physics is real but simplified and the numbers are illustrative values chosen for learning; each step says what it leaves out. Do not use it to design real flight hardware.

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