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• thaumasiotes 5y ago
  > When you escape earth orbit you have to exceed its orbital velocity around the sun. This doesn't sound right. Orbital and escape velocities for the earth should depend only on the mass of the earth.
  • bagels 5y ago
    You can escape earth's orbit going barely faster, or barely slower than earth relative to the sun, depending on where you're going. This stuff can be confusing, because you're mixing two different reference frames (earth and the sun).
    • hoseja 5y ago
      That sounds like you're assuming you're standing still beforehand. Sure, the effect afterwards might look like you're going around the sun faster/slower than Earth but you started deep in Earth's gravitational well.
    • exDM69 5y ago
      This analysis falls short if you apply three body orbital mechanics. Going barely faster or slower than the Earth in close proximity to Earth will slowly cause Earth's gravity to pull the spacecraft back in. This can mean all sorts of funny shaped trajectories (horseshoe asteroids etc). You need about 11-12 km/s to relative to the Earth to escape Earth's gravitational pull from LEO (only a bit more than it takes to reach the moon). Earth itself is orbiting the sun at about 30 km/s. To not get re-captured, the spacecraft needs to be far enough in distance or the difference in velocity needs to be large enough. How much is "enough" depends on the time scale, but for spacecraft we're talking several km/s.