301–310 of 414 posts
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One nuke will kill any realistic sci-fi material. And guidance for those is a cheap and tested.
Nukes are a lot less effective when there is little or no atmosphere to push on.
Very cool. One thing I wish was better shown: space is close, it's just hard to go up. Our liveable breathable atmosphere is razor thin compared to the size of earth. In most cases, 100km is less than the distance between sizeable metropolitan areas. It's a day long bike ride. Air runs out less than a bus ride across town. A 15k jog/hike would put you in the stratosphere. Those jet aircraft that seem so high are clos…
Likewise, it is crazy to me when I realised how thin our oceans are. I used to think of them as super deep (I mean, they are) but even the Mariana trench is a mere 0.2% of the Earth's radius. Average ocean depth is more like 0.05%.
Very cool. One thing I wish was better shown: space is close, it's just hard to go up. Our liveable breathable atmosphere is razor thin compared to the size of earth. In most cases, 100km is less than the distance between sizeable metropolitan areas. It's a day long bike ride. Air runs out less than a bus ride across town. A 15k jog/hike would put you in the stratosphere. Those jet aircraft that seem so high are clos…
In a parallel universe where Africa is covered by world powers, Mount Kilimanjaro would make a pretty good launch facility. Reduced rocket equation needs for being nearly 3 miles high. If you start in thinner atmosphere you need less fuel to punch through it. You’re also higher when you hit Max Q. This is essentially what Scaled Composites and Virgin Galactic were trying to do with their cargo plane system, only you…
I don't know of any launch sites significantly above sea-level, the marginal performance increase wouldn't be worth the logistical nightmare. It's easier to fly up a 747 than build a launch facility on top of a mountain.
I love this page and I donated, but I was (naively) expecting it to get to geosynchronous altitude, which is the actual top of a space elevator. Of course, that would require a page 420 times longer, and I don't know if a browser would even support it.
https://neal.fun/size-of-space/>
There are a few sites which let you scroll through the solar system, from the Sun or Earth IIRC. Here's one:
https://onotherplanets.com/solarwalk>
Ah, and "If the Moon Were Only One Pixel", which is what I'd had in mind, shared by @stared https://news.ycombinator.com/item?id=45641839>:
https://joshworth.com/dev/pixelspace/pixelspace_solarsystem....> (2014)
(HN discussions: https://news.ycombinator.com/item?id=44266828> (4 months ago), https://news.ycombinator.com/item?id=21735528> (6 years ago) https://news.ycombinator.com/item?id=32936581> (3 years ago).
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You can reach space using air breathing jets. You can’t stay in space using air breathing jets.
I don't think there are any physics reasons why it'd be impossible, but certainly we can't do it with existing technology. You'd need an air breathing jet that could get a vehicle to go about five or six times faster than any current such engine has ever achieved (i.e. around mach 20-30), which is perhaps ridiculous, but I don't think it's necessarily impossible, just something we don't know how to do. There have bee…
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That didn't sound right to me, and so I checked it as follows: Estimate for a standard classroom globe at 13" in diameter (I'm seeing a rnage of 12-14 inches as typical). I'm reporting in inches because that is what came up first and most of the globes are for sale in the US. Mixing units here, but, it works out. But, in meters, the diameter of the Earth is 12,742,000 m on average. if we use the 'Karman line' as defi…
https://en.wikipedia.org/wiki/Atmosphere_of_Earth#Pressure_a... 90% of the atmosphere is below 16 km. 16 km * (12" / Earth diameter) :: https://www.wolframalpha.com/input?i=16+km+*+%2812%22+%2F+Ea... 0.015 inches, 0.38 mm ... and tossing sheets of paper into that ( https://www.wolframalpha.com/input?i=thickness+of+paper ) ... 16 km * (12" / Earth diameter) / thickness of paper :: https://www.wolframalpha.com/input?i=…
I think this thread would also be loved by the nerdy folks at https://Reddit.com/r/theydidthemath
>Above this altitude is known as the "death zone", because there isn't enough oxygen for human life. Being pedantic, this should be "there isn't enough oxygen for sustained human life". An acclimatised climber can survive tens of hours.
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If you somehow manage to get magnetic fields involved, so you are not afraid of friction with the cable itself, at 1.3 max apparent acceleration/deceleration (after a turnover) and including earth’s gravity you get 116min to geostationary. If you account for various inefficiencies like taking it slow in the lower atmosphere Ant whatnot, it still should be in the matter of hours. So totally feasible and even comfortab…
> If you somehow manage to get magnetic fields involved, so you are not afraid of friction with the cable itself, at 1.3 max apparent acceleration […] This means that half-way after 58 minutes, the climber is traveling at 0.3 * 9.81 m/s² * 60 * 58 ~= 10.2 km/s ~= 36,720 km/h (!!!) relative to the cable. A tiny imperfection or wobble is going to make the climber crash into the cable, destroying both. A climber with a…
A maglev train is several centimeters from the rail; if someone made the carbon nanostructures (the only known material strong enough are atomically precise carbon nanotubes or graphene, but the entire length has to be atomically precise you can't splice together the shorter tubes we can build today) this badly wrong, the cable didn't survive construction.
> Even at a voltage of 1 kV, that's around 1,500,000 A
Why on earth would you do one kilovolt? We already have megavolt powerlines. That reduces the current needed to 1500 A. 1500 A on a powerline is… by necessity, standard for a power station.
We even already have superconductor cables and tapes that do 1500 A, they're a few square millimeters cross section.
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If you somehow manage to get magnetic fields involved, so you are not afraid of friction with the cable itself, at 1.3 max apparent acceleration/deceleration (after a turnover) and including earth’s gravity you get 116min to geostationary. If you account for various inefficiencies like taking it slow in the lower atmosphere Ant whatnot, it still should be in the matter of hours. So totally feasible and even comfortab…
> If you somehow manage to get magnetic fields involved, so you are not afraid of friction with the cable itself, at 1.3 max apparent acceleration […] This means that half-way after 58 minutes, the climber is traveling at 0.3 * 9.81 m/s² * 60 * 58 ~= 10.2 km/s ~= 36,720 km/h (!!!) relative to the cable. A tiny imperfection or wobble is going to make the climber crash into the cable, destroying both. A climber with a…
I love this guy. Re playing this gem https://neal.fun/stimulation-clicker/