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Interstellar Flight: Perspectives and Patience

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94 points JPLeRouzic | 2 comments | 25 Jun 25 16:35 UTC | HN request time: 0.563s | source
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os2warpman ◴[25 Jun 25 17:54 UTC] No.44380049[source]▶
>To get around thousand-year generation ships, we are examining some beamed energy solutions that could drive a small sail to Proxima in 20 years.

The odds of a spacecraft hitting a single particle of dust while in space are 100%.

A spacecraft hitting a single particle of dust at 0.2c will impart tens of millions of joules into the body of the spacecraft, the equivalent of getting hit with hundreds of pulses from the most powerful laser ever created by humanity-- simultaneously.

Or concentrating several kilogram's worth of TNT into the size of a particle of dust and detonating it.

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1. umpalumpaaa ◴[25 Jun 25 18:59 UTC] No.44380754[source]▶
"A 0.1 µm interstellar dust grain (≈10⁻¹⁴ kg) striking a spacecraft at 0.2 c carries ≈20 J of kinetic energy—millions of times below “tens of millions of joules.” Reaching 10–50 MJ would require a ≈0.14 mm grain (≈10 µg), vastly rarer than ordinary dust, and even that impact equals only a few shots from the world’s highest-energy laser (~2 MJ per pulse), not “hundreds.”"
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2. os2warpman ◴[25 Jun 25 19:51 UTC] No.44381232[source]▶
I used something something 10^-10 for my dust. To reach ~50MJ.

As far as the laser goes, ~2MJ is the total output. Energy that reaches the fuel pellet due to inefficiencies throughout the path of the laser, the actual "hitting power", is hundreds-ish kJ.