Top all-time · #8859
Hop's Blog
Personal blog · hopsblog-hop.blogspot.comscience
Hop's Blog is a personal blog at hopsblog-hop.blogspot.com about science. Since 2014, 9 different Hacker News readers have linked it 21 times, most often “Travel on Airless Worlds (2014)”. The last post was in 2023, but the archive is still widely read.
Too few sampled comments (6) to say how often HN recommends it.?
Why HN links it
Hop David's blog covers space tethers, lunar sky hooks and space elevators, orbital dynamics and the rocket equation, plus a fact-check list. One commenter calls it excellent and says to read it chronologically.
Summarised by Claude from a sample of 6 HN comments that link here. Each comment is marked recommending, critical or neutral (citing without judging); how this works.
Most-linked posts?
- Travel on Airless Worlds (2014)2 people · 2 mentions · first linked 2018-05-15
What Hacker News says?
When mass parameter is big, use of WSBs is interesting. But mass parameters for sun-earth or sun-Mars are tiny. I've expressed my skepticism for ITN between earth and Mars: http://hopsblog-hop.blogspot.com/2015/04/potholes-on-interpl...
Comment linking /2015/04/potholes-on-interplanetary-superhighway.html
on “New Horizons: Nasa spacecraft speeds past Pluto”Submitted Travel on Airless Worlds (2014) as a story · 38 points
HN discussionPutting an elevator (or more likely a sky hook) at a lunar Langrange point makes some sense, because the tether doesn't have to reach the entire distance if we allow for 0.2km/sec injection/drop-off speeds. That's important, because lunar elevator/hooks are much longer than earth based equivalents, even though their strength and taper ratios are much more achievable (e.g. polyethylene 4:1). You'd want to keep launch…
Comment linking /2015/05/eml2.html
on “Japan starts space elevator experiments”Submitted Travel on Airless Worlds Part II (2014) as a story · 4 points
HN discussionhttp://hopsblog-hop.blogspot.com/2016/04/liftport-lunar-teth...
Comment linking /2016/04/liftport-lunar-tether.html
on “Earth-Moon Fire Pole”Submitted Orbital Tethers as Momentum Capacitors as a story · 1 points
HN discussionThere has actually been a lunar elevator proposed, the most massive part lying at Earth Moon Lagrange 1. In my opinion, not practical. I took a look using Xylon: http://hopsblog-hop.blogspot.com/2016/04/liftport-lunar-teth... For the numbers I used a safety factor of 1. The slightest nick or scratch would cause a break. Safety factor of 3 is more sensible.
Comment linking /2016/04/liftport-lunar-tether.html
on “Earth-Moon Fire Pole”Submitted Phobos--Panama Canal of the Inner Solar System as a story · 1 points
HN discussionFor more on space tethers, check out Hop David's excellent blog (cited as such in the article), wherein a laypersons understanding of orbital dynamics and momentum exchange is developed in posts spanning several years. http://hopsblog-hop.blogspot.com Best read in chronological order.
Comment linking /
on “Space Tethers: Stringing Up the Solar System”Much of Murphy's math and physics are wrong. For example to get delta V to go to Mars he adds earth's 11 km/s escape velocity to the 3.6 km/s Mars injection velocity. A freshman aerospace student could tell the speed of a Mars bound ship in a hyperbolic earth orbit is sqrt(11^2 + 3.6^2). I've done a number of posts calling out Murphy's bad arguments: https://hopsblog-hop.blogspot.com/2014/02/the-most-common-de... ht…
Comment linking /2018/06/space-meow-boys_30.html
on “Exponential Economist Meets Finite Physicist (2012)”Tom Murphy has an ax to grind. He fancies himself a modern day Paul Revere shouting the urgent message "Peak Oil is coming! Peak Oil is coming!". Anything that might lead us to complacency he attempts to debunk. So of course he will slam the possibility of space resources. But his "math" is wrong. See http://hopsblog-hop.blogspot.com/2012/02/in-his-blog-strande...
Comment linking /2012/02/in-his-blog-stranded-resources-tom.html
on “Drilling surprise opens door to volcano-powered electricity”I would call Tyson a good spokesman for science if he had a high regard for rigor and accuracy. But he does not. http://hopsblog-hop.blogspot.com/2016/01/fact-checking-neil-...
Comment linking /2016/01/fact-checking-neil-degrasse-tyson.html
on “Carlo Rovelli on the ‘greatest remaining mystery’: The nature of time”There are several. Here's one. http://hopsblog-hop.blogspot.com/2016/08/lunar-sky-hook.html https://hopsblog-hop.blogspot.com/2016/04/liftport-lunar-tet... There's also a wikipedia article: https://en.wikipedia.org/wiki/Skyhook_(structure)
Comment linking /2016/04/liftport-lunar-tether.html
on “The tyranny of the rocket equation (2012)”An elevator anchored to the earth and extending past geosynchronous orbit is wildly implausible. However orbital vertical tethers are doable with Zylon. A series of 3 orbital tethers could move stuff between LEO and the lunar neighborhood. http://hopsblog-hop.blogspot.com/2016/08/tran-cislunar-railr... Both Musk and Bezos seem well on their way to reusable boosters. But reusable upper stages is another story. An upp…
Comment linking /2016/08/tran-cislunar-railroad.html
on “Toray carbon fiber to carry SpaceX's Mars ambitions”>But really, these are ballistic trajectories. Are we going to put everyone in G suits? I assume you mean because minimum-energy ballistic trajectories[1] come into the atmosphere very steeply, so the G-forces are much higher. But by using flatter trajectories (closer to an orbit than a parabolic "hop"), you reduce the angle of entry considerably, at the expense of using more fuel. The result is that for Earth-to-Ea…
Comment linking /2014/06/travel-on-airless-worlds.html
on “SpaceX's plan to fly you across the globe in 30 minutes [video]”A space elevator on Earth is very hard to build and would require exotic materials which we can't yet synthesize in bulk. But you can make a decent lunar space elevator with Kevlar. http://hopsblog-hop.blogspot.com/2012/09/beanstalks-elevator...
Comment linking /2012/09/beanstalks-elevators-clarke-towers.html
on “People Are Still Trying to Build a Space Elevator”Two things. He's obviously an expert in astrophysics but his explanations are condescending and "well actually", like he is trying to convince you how smart he is. That's given him a reputation as a blowhard online. Outside of that field, his takes are your typical "genius in one thing believes he's a genius in everything". Someone even made a list of his mistakes: https://hopsblog-hop.blogspot.com/2016/01/fact-chec…
Comment linking /2016/01/fact-checking-neil-degrasse-tyson.html
on “I'm Scared About Biological Computing”
