<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>ben_w</author><text>Energy is the biggest problem, but it’s far from the only one.&lt;p&gt;Consider the ISM: at 0.086 c, ionised helium is the same thing as 14 MeV alpha radiation. Low density regions within the galaxy are 0.2–0.5 particles&amp;#x2F;cm^3; 0.2&amp;#x2F;cm^3 * 0.086 c is ~5e12 particles&amp;#x2F;m^2&amp;#x2F;second, or about 9.9 watts&amp;#x2F;m^2 if it was all He4 and therefore 14MeV&amp;#x2F;particle or about 2.5 W&amp;#x2F;m^2 for Hydrogen at the same speeds, which is bad enough given what keeping that up for years will do to any solid hull, but molecular clouds can be 10^2-10^6 particles&amp;#x2F;cm^3 and the upper bounds of that is ~10 MW&amp;#x2F;m^2.&lt;p&gt;Even without Relativity (which makes it worse), if you double the speed the kinetic energy per particle quadruples &lt;i&gt;and&lt;/i&gt; you also double the number of particles per unit time.</text><parent_chain><item><author>Johnny555</author><text>If we could solve the energy problem, humans could go pretty much anywhere in the galaxy on a 1G ship. (ok there are other issues like actually building the ship, supplies (or a biosphere that can support life for decades), shielding,  but that&amp;#x27;s all easier with unlimited energy).&lt;p&gt;For example, a ship could travel 1,000 light years to the Orion Nebula in only 15 years (as perceived by those on the ship). And since they are living in 1G, a lot of the detrimental effects of long-term space travel are eliminated.&lt;p&gt;Of course, to an observer on earth the trip would take over 1000 years, so don&amp;#x27;t expect to hear how the trip went.</text></item></parent_chain></comment><story><title>A Roadmap to Interstellar Flight (2016)</title><url>https://arxiv.org/abs/1604.01356</url></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>nerpderp82</author><text>If you take your whole civilization with you, it doesn&amp;#x27;t matter how fast or slow you go, you are already where you need to be.</text><parent_chain><item><author>Johnny555</author><text>If we could solve the energy problem, humans could go pretty much anywhere in the galaxy on a 1G ship. (ok there are other issues like actually building the ship, supplies (or a biosphere that can support life for decades), shielding,  but that&amp;#x27;s all easier with unlimited energy).&lt;p&gt;For example, a ship could travel 1,000 light years to the Orion Nebula in only 15 years (as perceived by those on the ship). And since they are living in 1G, a lot of the detrimental effects of long-term space travel are eliminated.&lt;p&gt;Of course, to an observer on earth the trip would take over 1000 years, so don&amp;#x27;t expect to hear how the trip went.</text></item></parent_chain></comment><story><title>A Roadmap to Interstellar Flight (2016)</title><url>https://arxiv.org/abs/1604.01356</url></story>