[HN Gopher] Space Elevator
___________________________________________________________________
Space Elevator
Author : kaonwarb
Score : 1435 points
Date : 2025-10-20 04:42 UTC (18 hours ago)
(HTM) web link (neal.fun)
(TXT) w3m dump (neal.fun)
| kinduff wrote:
| I always enjoy Neal's pages. I found planes at high altitude very
| interesting, didn't know we could fly that high!
| lproven wrote:
| To quote _Toy Story_ :
|
| "That's not flying, that's just... falling with style!"
|
| Accelerate upwards fast enough, you can so to speak fall
| upwards for a short while before you fall back down again...
| adzm wrote:
| It was enjoyable and informative.
|
| Learned that sprites can be 50km long!!
| fuzzy2 wrote:
| Earlier this year, we were treated to an exceptional photo of
| one: https://www.smithsonianmag.com/smart-news/mysterious-red-
| spr...
| daniel_iversen wrote:
| This was incredible! Couldn't stop scrolling and reading. For a
| kid of a certain age and curiosity it'll blow their mind! I'm so
| grateful the creator made this, shame that his "buy me a coffee"
| isn't a simple PayPal or Apple Pay but you have to put in credit
| card or bank details!!
| anticrymactic wrote:
| PayPal and Apple pay take a significant cut of the transaction.
| CC is a lot less and bank is mostly free of TX fees. Most users
| don't know/don't care, so given the option, they will likely
| take it and funnel their donations to conglomerates.
| jve wrote:
| I don't like to input Cc details into random sites whose main
| business is processing said transactions.
| linsomniac wrote:
| Maybe you'd like one of the banks that provides you with
| limited-use or one-time credit cards? I've been using one
| called Envelope Budgeting for the last few months after my
| previous one shut down. It's $40/year, but that's waived if
| you spend more than $5,000 USD in card purchases. I put the
| Neal.fun on my "Misc" card that I keep at $0 balance and
| transfer money to when I buy something.
|
| I believe there are other services that will also give you
| virtual cards, I'm not familiar with them off hand.
|
| https://envelopebudgeting.com/
| pie_flavor wrote:
| I use https://privacy.com for this, you can create
| virtual cards with total spend limits or spend rate
| limits.
| dmd wrote:
| I'm not understanding this sentiment at all. You'd rather
| input your CC details into a site whose main business _isn
| 't_ dealing safely with credit cards - rather than
| inputting it into Stripe (which is what his site uses),
| whose entire raison d'etre _is_ doing so?
| jve wrote:
| Sorry, I got the expression wrong. You must inverse the
| logic :)
| mbirth wrote:
| But xx% of some amount is still better than 100% of $0. And
| the pure convenience of using PayPal, Apple Pay or things
| like Ko-Fi will probably result in more net donations.
| blueg3 wrote:
| PayPal doesn't cost significantly more than what a small
| online place can get from other payment processors. It's
| something like 3% + $0.50. That's also not much more than
| what a small business can usually get for in person credit
| cards.
|
| This site does use buymeacoffee.com, which appears to be a
| dedicated payment platform. Its transaction fee is apparently
| 5%, which is steeper, but better for these small donations
| because of the lack of a fixed fee.
| sharkjacobs wrote:
| > Apple Pay take a significant cut of the transaction
|
| I don't think this is true
|
| > Apple Pay does not cause additional fees for users and
| merchants.[1]
|
| [1]https://en.wikipedia.org/wiki/Apple_Pay#Cost
| ddoolin wrote:
| How do you pay with PayPal if not putting in your credit card
| or bank details? link is a pretty well-known online wallet and
| much simpler to use than PayPal.
| sojournerc wrote:
| I've never heard of link, so it's the difference between a
| random website and a well established brand. Not that hard to
| understand why someone might be hesitant to put in their cc
| details.
| ai-onehealth wrote:
| Excellent! My wrist started to hurt 0.01% of the way to the moon.
| _def wrote:
| The atmosphere of this reminded me of the game Outer Wilds
| Physkal wrote:
| I was really disappointed not to see a sequel. No new games
| from the developers since.
| Cthulhu_ wrote:
| Its development is really interesting, in that it was more a
| proof of a scientific paper to start with. Anyway one of
| their tweets from September 2024 indicates they're working on
| a sequel, despite their publisher (Annapurna, owned by Megan
| Ellison, daughter of Larry Ellison) having had some issues
| around then.
| nunodonato wrote:
| they are working on a new game. Outer Wilds doesn't need a
| sequel, leave it be, its perfect as it is ::)
| tempestn wrote:
| TIL it's estimated that over 48 tons of meteors hit the
| atmosphere every day.
|
| Regarding actual space elevators though, while they're not sci-fi
| to the extent of something like FTL travel - ie. they're
| technically not physically impossible - they're still pretty
| firmly in the realm of sci-fi. We don't have anything close to a
| cable that could sustain its own weight, let alone that of
| whatever is being elevated. Plus, how do you stabilize the cable
| and lifter in the atmosphere?
|
| A space elevator on the moon is much more feasible: less gravity,
| slow rotation, no atmosphere, less dangerous debris. But it's
| also much less useful.
| lnsru wrote:
| Space elevator was the perfect application for carbon nanotubes
| according my professor few decades ago. I wish humanity could
| unite for such project and enter space exploration phase. But I
| feel it will stay sci-fi forever.
| tiagod wrote:
| Thing is, you're going to invest massive amounts of R&D in
| something that might be impossible, when you could invest in
| actually building stuff in space so you only need to shoot
| humans out there.
| floxy wrote:
| Instead of massive amounts of R&D, why not small amounts
| for the next 100 years? Seems like this is something a tech
| bro could bequeath to humanity, Nobel style. A $250 million
| fund that pay out $10 million per year in grants. And maybe
| some larger chunks when the board of directors sees a good
| opportunity to do larger scale trials.
| Yizahi wrote:
| The problem with space elevator is not only the lack of
| material today, but also the fact that such elevator is an
| ultimate and very fragile weapons platform, you basically get
| stones up the well and then drop them on the enemy. Meaning
| that any authoritarian country would destroy it even before it
| is ever built. And sturdy enough space elevator after it's
| break at any high point would start falling down on the planes
| in a loop, eventually flattening everything in its path when
| higher portions reach supersonic speeds. So unfortunately there
| is low chance it will be built, unless we sort out stuff on the
| planet first.
| pbmonster wrote:
| I don't see it. Why worry about a weaponized space elevator
| when stealth bombers, cruise missiles and ICBMs exist?
|
| If the power building the space elevator wants to bomb you,
| you're going to get bombed.
| tsimionescu wrote:
| The bigger problem I think is the elevator itself. Cutting
| it and letting it fall would be far more destructive than
| any weapon ever fired or even conceived.
| pbmonster wrote:
| Probably no easy task.
|
| Snipping off just the first few kilometers is not
| catastrophically destructive yet, and cutting it down
| further up would require multistage rocket designs,
| sophisticated steering/targeting and potentially
| significant yield (you'd need to cut unobtainium, after
| all...). If you can build a space elevator, you can
| defend against those.
|
| You better thoroughly inspect what cargo you put on the
| elevator itself, of course.
| tsimionescu wrote:
| Only if the material is way over provisioned. In general,
| the higher the intrinsic structural load is on a
| material, the easier it will be to destroy. So, to defend
| from these attacks, you not only need a cable that can
| support its own weight, plus the weight of the desired
| payload, plus some small-is extra tolerance. Instead, you
| probably need a cable that can support, say, twice its
| own weight plus four-five times the payload. Not to
| mention, now you don't only need excellent strength along
| the cable, but also across from it, and extreme heat
| resistance too (all of the strength is irrelevant if it's
| enough to coat some part of the cable in thermite and
| ignite it)
| icetank wrote:
| You only need to defend the easy to reach parts. So the
| base and the cargo pod. To hit the upper parts you need
| advanced rockets and targeting systems.
| tsimionescu wrote:
| Why advanced? It's a stationary target that's 35,000 km
| long. I don't think it would be that hard to hit.
|
| Not to mention, securing the cargo would be an extremely
| difficult task in itself, especially when one of the main
| thinga you'd like to raise through the space elevators is
| rocket fuel.
| vdqtp3 wrote:
| > stationary target that's 35,000 km long
|
| and what, 12" wide? 24"? that's still very difficult to
| target
| tsimionescu wrote:
| In general, the more tensile strength you want in a cable
| made of a given material, the thicker you need to make
| that cable. Now sure, we can imagine whatever magical
| properties we want of our space elevator cable material,
| since no known material that could do this exists anyway.
| But it's far more likely that you'd need a cable that's a
| kilometer or more in diameter to achieve the tensile
| strength needed to support its weight at 35000 km of
| length, than it is to be a few inches wide.
| Yizahi wrote:
| One nuke will kill any realistic sci-fi material. And
| guidance for those is a cheap and tested.
| pbmonster wrote:
| Yeah, but then we're discussing opponents with nuclear
| arsenals and ICBM programs. Those opponents are generally
| reluctant to nuke stuff, or commit acts of war similar to
| nuking stuff.
|
| But yes, a space elevator would be difficult to defend in
| World War III.
| hermitcrab wrote:
| Nukes are a lot less effective when there is little or no
| atmosphere to push on.
| pfdietz wrote:
| They'd cause the surface of the elevator to explode, just
| from energy deposition, down to thicknesses dictated by
| how penetrating the radiation is.
| iberator wrote:
| Easy. You just blow the elevator FROM INSIDE. Plant some
| bomb into the elevator itself and while in half way BOOM!
| pbmonster wrote:
| That's what the entire point about INSPECTING CARGO was
| about.
| bob1029 wrote:
| And hypersonic weapons. If you can get one to fly at Mach
| 20 for at least 10 minutes, you could cover the entire
| surface of the planet with a dozen launchers.
| Yizahi wrote:
| Russia, China, Iran etc. are throwing a hissy fit whenever
| even a small weapons are deployed in the neighboring
| countries. USA too if we are being fair. They won't even
| wait for that opportunity.
| sixQuarks wrote:
| The US throws the biggest hissy fit AND is the biggest
| hypocrite about it as well.
| actionfromafar wrote:
| When the stakes are that high, words such as hypocrite
| don't fit very well. It's all game theory. It bought us
| Pax Americana for a while. Not universally loved but a
| time may (God forbid) come when it will be universally
| _missed_.
| pbmonster wrote:
| I think they mostly throw a fit because medium range
| ballistic missiles allow practically no useful early
| warning.
|
| When the ICBMs go up, early warning radars notice them
| right away and you still have time to act. Leaders can
| make it to helicopters and basement bunkers, bomber
| squadrons can scramble, missile silos can already be
| empty when hit, road mobile ICBM launchers can still
| relocate.
|
| But with a large enough number of MRBMs, your opponent
| might get ideas. They might start thinking about getting
| away with a decapitation strike.
|
| The military space elevator is more like an ICBM in this
| case. There will be ample warning when somebody drops
| something from geostationary orbit (and also when
| somebody drops something from lower up).
| sekai wrote:
| > Russia, China, Iran etc. are throwing a hissy fit
| whenever even a small weapons are deployed in the
| neighboring countries
|
| Because that's all they can do
| pbmonster wrote:
| > A space elevator on the moon is much more feasible: less
| gravity, slow rotation
|
| The slow rotation is a minus, it means you've got to string the
| tether up to L1 instead of "just" up to geo/luna-stationary
| orbit. A lunar space elevator needs to be at least 56000 km
| long, more than 20000 km longer than the one to earth.
|
| > But it's also much less useful.
|
| Yeah, especially because all the things that make lunar space
| elevators a little more attainable also make lunar mass drivers
| a lot more attainable. Why ride in an elevator for a week if
| you also can just be fired from a cannon?
| pfdietz wrote:
| A space elevator is kind of like a vertical mass driver, so
| just build one of those along the surface of the moon with
| modest acceleration, survivable by passengers.
|
| Rotating cables ("rotavators") on the moon seem much more
| practical than full space elevators.
|
| https://en.wikipedia.org/wiki/Momentum_exchange_tether#Rotov.
| ..
| tempestn wrote:
| Ah, good catch. Stand corrected on that one.
| adwn wrote:
| Almost all discussions around space elevators focus on the
| cable itself, how to manufacture and deploy it, and completely
| forget about the issues that would arise afterwards:
|
| 1) How do you attach the climber to the cable without affecting
| its structural integrity? By squeezing it really hard? A
| material that's optimized for longitudinal tension strength is
| probably not very tolerant of lateral compression.
|
| 2) How do you provide power to the climber? A regular electric
| cable can't support its own weight, so either you have to
| attach it to the climbing cable, or you have to make it from
| the same material.
|
| 3) Is it even worth it? The climber needs to cover a distance
| of ~36,000 km, so even at 200 km/h it takes 7.5 days from the
| bottom to geosynchronous orbit. How many climbers and what
| payload can the cable support at the same time? Refer to issue
| #1 regarding limits in speed and mass per climber.
|
| The throughput in tonnes/day is absolutely abysmal in relation
| to the immense upfront infrastructure cost per elevator.
| Compare this to SpaceX's Starship, which is getting closer and
| closer to fully reusable _100 tonnes to orbit in minutes_.
| Space elevators will stay science fiction forever, not because
| they 're infeasible, but because they're useless.
| seer wrote:
| 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
| comfortable.
| adwn wrote:
| > _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 mass of 10 tonnes requires 10^4 kg * 1.3 *
| 9.81 m/s2 ~= 127.5 kN of force to accelerate at 1.3 g. At
| the ~56 minute mark, the climber reaches a speed of ~9,888
| m/s. This means it requires a power output of 127.5 kN *
| 9888 m/s = 1.26 GW (!!!) to achieve this acceleration, plus
| overhead for the power electronics and transmission. Even
| at a voltage of 1 kV, that's around 1,500,000 A (!!!) of
| current that you have to transmit and invert.
|
| If you have a way to reliably transfer that amount of power
| without touching the cable which is moving at 10 km/s
| relative speed, or with touching but without immediately
| melting the cable or the collector, let me know :-)
|
| > _So totally feasible_
|
| lol no
| ben_w wrote:
| > A tiny imperfection or wobble is going to make the
| climber crash into the cable, destroying both.
|
| 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.
| adwn wrote:
| > _A maglev train is several centimeters from the rail
| [...]_
|
| No maglev train _I_ ever heard of travels at 36,000 km
| /h. This is about two orders of magnitude faster.
|
| > _We already have megavolt powerlines._
|
| That's _transmission over long distances_ , but you need
| to handle and transform all that power in a relatively
| small enclosure. Have you seen the length of isolators on
| high-voltage powerlines? What do you think is going to
| happen to your circuit if you have an electrical
| potential difference of 1 MV over a few centimeters?
|
| Yes, you _can_ handle large voltages with the right power
| electronics, but you need the space to do so. For
| comparison, light rail typically uses around 1 kV, while
| mainline trains use something like 15 kV. But a train is
| also 10 to 100 times as heavy as the 10t climber in my
| calculation, so you need to multiply the power (and
| therefore the electric current) by 10 to 100 as well.
| ben_w wrote:
| > No maglev train I ever heard of travels at 36,000 km/h.
| This is about two orders of magnitude faster.
|
| You think the problem is the speed itself, and not the
| fact that trains are close to sea level and at that speed
| would immediately explode from compressing the air in
| front of them so hard it can't get out of the way before
| superheating to plasma, i.e. what we see on rocket re-
| entry only much much worse because the air at the
| altitude of peak re-entry heating is 0.00004% the density
| at sea level?
|
| > What do you think is going to happen to your circuit if
| you have an electrical potential difference of 1 MV over
| a few centimeters?
|
| 1) In space? Very little. Pylons that you see around the
| countryside aren't running in a vacuum, their isolators
| are irrelevant.
|
| 2) Why "a few centimetres"? You've pulled the 10 tons
| mass out of thin air, likewise that it's supposed to use
| "one kilovolt" potential differences, and now also that
| the electromagnets have to be "a few centimetres" in
| size? Were you taking that number from what I said about
| the gap between the train and the rails? Obviously you
| scale the size of your EM source to whatever works for
| your other constraints. And, for that matter, the peak
| velocity of the cargo container, peak acceleration, mass,
| dimensions, everything.
|
| > For comparison, light rail typically uses around 1 kV,
| while mainline trains use something like 15 kV.
|
| Hang on a minute. I was already wondering this on your
| previous comment, but now it matters: do you think the
| climber itself needs to internally route any of this
| power at all?
|
| What you need for this is switches and coils on one side,
| a Halbach array on the other. Coils aren't that heavy,
| especially if they're superconducting. Halbach array on
| the cargo pod, all the rest on the tether.
|
| Right now, the hardest part is -- by a huge margin --
| making the tether. Like, "nobody could do it today for
| any money" hard. But if we could make the tether, then
| actually making things go up it is really not a big deal,
| it's of a complexity that overlaps with a science faire
| project.
|
| (Also, I grew up with 25kV, but British train engineering
| is hardly worth taking inspiration from for other rail
| systems, let alone a space elevator).
| adwn wrote:
| Oh, and 10 tonnes is bus-sized. For infrastructure at
| that scale, you want trains at the very least, and those
| are on the order of 1,000 tonnes. Multiply force, power,
| and current by 100 accordingly.
| lloeki wrote:
| Well if it's contingent to having massive amounts of
| unobtainium and subject to unsolvable engineering reality check
| conundrums then it's just as unlikely as an Alcubierre drive
| which "only" needs exotic matter that allows negative energy.
| tsimionescu wrote:
| While a space elevator doesn't contradict any fundamental
| limits of physics, that doesn't mean it's actually possible to
| build one. There is no reason to be certain that it's actually
| possible to create a material that has the required
| characteristics in terms of tensile strength to support it's
| own weight, plus the weight of the elevator, plus the weight of
| all the additional cabling. It also has to endure the huge
| temperature differences that it will experience along its
| length and from day to night and from season to season.
|
| This is especially true considering that you don't need
| something that barely holds - you need something that you know
| will hold up to many times more weight than it needs to, so
| that it can be safe: the potential energy such a thing would
| store would be enough to dig into hundreds of meters of rock
| all around the world, if it ever crashed. So, you have to
| ensure there is no realistic chance of it ever crashing. It
| also has to be highly non-fragile in other ways, so that a
| madman with a bomb or a freak collision with an airplane or a
| meteor (especially likely in the thin upper layers of the
| atmosphere) won't bring it all down.
|
| This combination of properties may well be completely
| impossible to actually achieve in a material. Even if there is
| no obvious basic law of physics that it would break, that
| doesn't mean that it wouldn't break other, harder to touch,
| derived laws.
| Jolter wrote:
| A terrorist attack on a space elevator happens to figure in
| the first episode of the TV series Foundation.
|
| https://foundation.fandom.com/wiki/Bombing_of_the_Star_Bridg.
| ..
|
| It's about as devastating as you would expect.
| lproven wrote:
| That's odd. The first episode was the only one I watched
| and I don't remember that bit. It might have grabbed me.
|
| A terrorist attack on a space elevator is a pivotal plot
| point in _Blue Mars_ by Kim Stanley Robinson, which IMHO is
| a better work in basically every way than Asimov 's _magnum
| opus._
| Metacelsus wrote:
| Doesn't the space elevator attack happen in Red Mars not
| Blue Mars?
| p_l wrote:
| There's a terrorist attack, sorta, in latter book, but
| Red Mars was admittedly a legitimate military strike, as
| was destruction of Phobos.
| lproven wrote:
| I happily defer. I've reread the trilogy 6 times now and
| they do all blur together a bit.
|
| You look to be right:
|
| https://www.kimstanleyrobinson.info/content/space-
| elevator
|
| And I'm not the only one to notice the cross-reference:
|
| https://www.reddit.com/r/kimstanleyrobinson/comments/pv6z
| h9/...
| CaptainOfCoit wrote:
| > That's odd. The first episode was the only one I
| watched and I don't remember that bit. It might have
| grabbed me.
|
| I think it's the first episode of season 2 or 3, not the
| first season. I remember someone else mentioning it, but
| I've only seen season 1 and don't recall that either.
| mechanicum wrote:
| Definitely S01E01, @ ~55-58 minutes. I just watched it.
| lproven wrote:
| Huh. OK then. I was not taken by it and don't really want
| to watch it again, or the whole thing, so I will take
| your word.
| Frotag wrote:
| Terrorists-attacking-elevator is something that comes up
| multiple times in Gundam 00. Probably as an allusion to
| 9/11 (resistance to a growing superpower), but the in-
| universe explanations are pretty interesting too.
|
| The elevators were developed for cheap space travel but
| unsurprisingly centralized the world's economic development
| around the owner countries. ie the other countries became
| increasingly reliant on them and the world segmented into
| (three) blocs. But the owner countries became increasingly
| protective / paranoid, leading to cold-war era developments
| where each of them secretly researched fancy space weapons
| and stockpiled more and more military assets around the
| elevators.
|
| So some of the attacks were by poorer countries lashing
| out. Some attacks were to expose the military assets being
| hidden in the elevator (outlawed by intl treaty). Though
| most were probably just excuses to show things like giant
| robots vs death star.
| icetank wrote:
| The issue of the line falling back to earth is solved by
| putting the base of the elevator on water. If the top part of
| the elevator was cut of you could even detonate charges along
| the line to make sure all pieces fall into water.
| 0xEF wrote:
| Are we to assume they would be falling straight down?
| Because I'm pretty sure that's wrong. I'm not a physicist,
| though, and am happy to be corrected because every time the
| Space Elevator comes up, I want to know what happens when
| catastrophic failure occurs and how we'd mitigate that.
| speed_spread wrote:
| It would become a giant whip falling faster and faster
| round the equator.
| devilsdata wrote:
| https://en.wikipedia.org/wiki/Space_elevator
|
| > Above GEO, the centrifugal force is stronger than
| gravity, causing objects attached to the cable there to
| pull upward on it. [...] On the cable below geostationary
| orbit, downward gravity would be greater than the upward
| centrifugal force, so the apparent gravity would pull
| objects attached to the cable downward.
|
| So, without defensive countermeasures, the Space Elevator
| would indeed whip around the Earth.
|
| But honestly, if I were designing such a thing, it would
| have break points, and maybe even a whinch at the base,
| to pull the line in. I'd also build it over water, and
| not over a population centre.
|
| But I'm only a software engineer- it's likely a _lot_
| more challenging than this.
| mr_toad wrote:
| A space elevator on Earth would be over 35,000 kilometres
| long. Depending where it broke it could wrap halfway around
| the Earth.
| kqr wrote:
| At first I was confused by this because the Karman line
| is less than a percent of Earth's circumference up, but
| then I realised we're probably talking a geostationary
| anchor or something, which is very nearly a circumference
| up.
| tsimionescu wrote:
| Yes, you need a geostationary orbit for the tether,
| otherwise it would either fall down or spiral away with
| time.
| gambiting wrote:
| Could you make it over double the length needed, so if it
| ever broke it would be pulled away from Earth and float
| into space and not crash into the Earth?
| tsimionescu wrote:
| No. You'd need an even more magical material that can
| witstand at least double the tensile strength (since the
| parts that go above and below the GEO anchor would be
| pulling with about the same force in opposite
| directions). And if you destroyed the GEO point anchor,
| the cable would just split in two - everything that's
| below GEO would fall, everything that's above would float
| away.
| floxy wrote:
| Let's say the cable gets detached really close to the
| geosynchronous tether point (that's the worst case,
| right?). How much of the cable will burn up in the
| atmosphere? What is the density of the carbon nano-tube /
| graphene ribbons? And what is their terminal velocity?
| Has anyone proposed dimension of a graphene ribbon
| tether? Like it is 300 mm wide by 0.01 mm thick?
| pfdietz wrote:
| There's also the issue of the vehicle on the space elevator
| falling back to Earth if it detaches from the space
| elevator (accidentally or deliberately in case of
| malfunction that stops it from moving up). This means each
| vehicle will need rockets on it. At low altitude, the
| rockets are fired to keep the vehicle from reentering the
| atmosphere too fast at a steep angle, killing the
| passengers. At high altitude, the rockets fire to raise the
| perigee enough that the vehicle misses the atmosphere
| entirely (or enters at a very shallow survivable angle).
| There's a cross over point that dictates the delta V the
| rocket must be able to deliver. which if I vaguely recall
| correctly is greater than 4 km/s.
|
| Pure payload capsules with no passengers wouldn't need
| this.
|
| The argument for space elevators is that there's a pretty
| strong limit on how much payload can be launched by rockets
| due to injection of water into the upper atmosphere.
| Starship could arguably reach this limit with plausible
| projected growth rates in traffic.
| actionfromafar wrote:
| Why is the water bad?
| tonyhart7 wrote:
| heavy as fuck
| actionfromafar wrote:
| It would like, rain down hard?
| pfdietz wrote:
| In the stratosphere it both contributes to IR opacity,
| increasing global warming, and can provide ice surfaces
| on which ozone destruction is amplified. The stratosphere
| is normally extremely dry, so even small inputs can have
| an effect that would be invisible in the much moister
| troposphere.
| actionfromafar wrote:
| Aha, so in the stratosphere we should use oxygen / solid
| carbon boosters?
| pfdietz wrote:
| Their Isp is very low, unfortunately, because the
| molecular weight of the combustion gas is too high. Ditto
| for oxygen/carbon monoxide.
|
| Maybe the Isp could be increased by mixing in some
| helium, but helium is very expensive.
| tsimionescu wrote:
| I don't understand why you think that where you put the
| base of a 35000km cable makes a difference for where the
| rest of it would fall. I also don't understand why you
| think that a 35000 km long cable falling in the ocean from
| space would cause any less damage to the planet than it
| falling down on solid ground, or at least why the
| difference would be significant.
| JumpCrisscross wrote:
| > _why you think that a 35000 km long cable falling in
| the ocean from space would cause any less damage to the
| planet than it falling down on solid ground_
|
| They're not obviously wrong.
|
| A lot of the cable is moving at escape and orbital
| velocities. Tensile strength is all that holds it
| together.
|
| If, as the cable fails, you sever the parts above from
| below around escape velocity, you'll significantly reduce
| the length of cable that will ever hit the surface.
| kakacik wrote:
| What would be the wnergy delivered by 35k km of ultra
| strong thick cable falling down with possibly supersonic
| speed? A small bit not much, but such length adds up.
| gtowey wrote:
| I'm wondering if it's one of those paradoxes where by the
| time we are technologically capable of building one, we won't
| actually need it.
| metalman wrote:
| thing is we do have materials strong enough, because as it
| turns out the issue with strength is in flaws between indivual
| molecules in any given material, not so much the type of
| material, and very small amples with perfect molecular bonds
| are plenty strong, but getting consistent perfect molecular
| bonds is the challenge, and if this can be done, other
| technologys ,such as vacume ballons will be possible, such as
| flying citys to go with the space rlevators
| zoomzoom wrote:
| There are designs for untethered structures in orbit that could
| function with current technology, e.g.
| https://en.wikipedia.org/wiki/Skyhook_(structure)
| fijiaarone wrote:
| Have you ever tried to balance a string on its end? It gets
| harder, the longer the string is. There aren't any other
| physics than that.
| hermitcrab wrote:
| I think most plans envisage a large mass (such as a captured
| asteroid) in geostationary orbit to anchor the top of the
| elevator cable.
| JumpCrisscross wrote:
| > _while they 're not sci-fi to the extent of something like
| FTL travel - ie. they're technically not physically impossible_
|
| On Earth.
|
| Zylon or M5 [1] could build an elevator on Mars. Kevlar on the
| Moon.
|
| To drive this home, it's estimated we could build a lunar space
| elevator for less than what Bechtel fleeced NASA for a mobile
| SLS launcher [2][3].
|
| [1] https://en.wikipedia.org/wiki/M5_fiber
|
| [2]
| https://opsjournal.org/DocumentLibrary/Uploads/The_Lunar_Spa...
|
| [3] https://oig.nasa.gov/wp-
| content/uploads/2024/02/IG-22-012.pd...
| retube wrote:
| Was hoping would go to geostationary orbit as an actual space
| elevator would :)
| Terr_ wrote:
| Ditto, although you'd have to scroll about 357 times further.
|
| I suppose it could be livened up by including the orbits of
| things, but there would still be lots and lots of empty space.
| officehero wrote:
| Such a lost opportunity, was hoping for another "space is
| massive" experience like already done in similar interactive
| maps.
| lproven wrote:
| The thing is, the same author has already done that.
|
| https://neal.fun/size-of-space/
| kmacdough wrote:
| Would be boring and space elevators are just for fun. They
| aren't a real idea.
| matt3210 wrote:
| I love this guy.
|
| Re playing this gem https://neal.fun/stimulation-clicker/
| eMPee584 wrote:
| Careful folks! This escalates quickly. Do not use xdotool on
| this.
| dole wrote:
| Grateful it wasn't as long as Infinite Paperclips or Cookie
| Clicker, but still worth it. Great site!
| hakanito wrote:
| Thanks, I spent my lunch hour completing it without cheating.
| Amazing!
| archon810 wrote:
| Damn you! Half an hour later...
| 243423443 wrote:
| I just clicked the temperature thingy in annoyance because I
| don't use Fahrenheit and to my delight, it just switched to
| Celcius
| isolli wrote:
| Mine was automatically set to Celsius ;)
| kqr wrote:
| I did the same. I eyed it suspiciously and thought to myself,
| "This site is really well designed. Do you think if I..." and
| it did switch! The obvious interaction was implemented! Rare
| these days.
| gowld wrote:
| Doesn't work on the the "meters" display, though!
| tonyhart7 wrote:
| the website feels heavy, can we optimize this further?? (not a
| web dev)
| randomtoast wrote:
| I just looked at it in the dev console in a chrome based
| browser and I think it is already pretty optimized. It runs
| very smooth on my device (Thinkpad T480).
| cyode wrote:
| A beautifully executed project here, I bought Neal a coffee.
|
| What evolutionary advantage, I wonder, is there to Ruppell's
| griffon vulture flying at 11400 meters?
|
| edit: units
| rkomorn wrote:
| Not every behavior has an evolutionary advantage.
|
| If anything, "evolution" filters out disadvantages (eg: can't
| survive because your neck's too short and that pesky giraffe is
| eating all the leaves you could reach).
|
| Evolution kills what doesn't work.
| trinari wrote:
| but every behaviour has a cost. In cast of flight altitude
| its energy and distance to food, water, mating zones.
| rkomorn wrote:
| Having a cost and being too costly aren't the same thing
| though.
| hatmanstack wrote:
| Darwin started with survival of the "fit". It changed to
| "fittest" in later editions.
| robocat wrote:
| People focus on the wrong issue so most quotes about
| evolution are highly misleading: the keyword should be
| about reproducing. Survival is almost irrelevant. Darwin
| awards in particular should never be given to anyone with
| kids (unless they kill their kids too).
|
| "Most grandkids" is good but not catchy.
|
| Or Idiocracy "evolution began to favor those who
| reproduced the most".
| rkomorn wrote:
| I agree to some extent but I don't think you can really
| separate the two. You have to survive long enough to
| reproduce enough. For almost all species, reproduction
| implies a non trivial amount of survival.
|
| Edit: actually, "almost all species" is not right. Maybe
| "almost all interesting species"... which is admittedly
| too subjective a take.
| Cthulhu_ wrote:
| Going up there's currents, going down... gravity. Sure it
| costs energy, but there's bound to be a tradeoff. Travel
| distance? Sight range?
| iberator wrote:
| Feets are actually just fine in anything related to aviation.
| actionfromafar wrote:
| I prefer to call them "footsies" or, sometimes "feet".
| balamatom wrote:
| I think you've accidentally invented the antidote to the
| Imperial system: using diminutive/silly synonyms for units,
| and speaking in baby talk to people who insist on using it.
|
| Unironically oughtta work better than that stuff with the
| barleycorns and fortnights.
| actionfromafar wrote:
| Great idea! I'm for it. Be the change you want to see in
| the workplace!
| delta_p_delta_x wrote:
| > Feets are actually just fine
|
| Non-SI legacy units have been grandfathered in and 'accepted
| for common use', but ICAO recommends that SI units should be
| used[1] (eventually). China and quite the majority of the ex-
| USSR, for instance, use metre flight levels[2].
|
| There have been at _least_ two aviation accidents and
| incidents relating to unit mis-conversions. This is two too
| many. As an SI absolutist, everyone should switch to SI or
| units purely derived from SI (so domain-specific stuff like
| parsecs, electronvolts, and binary prefixes, if appropriately
| symbolled are OK). It is an internationally-recognised, and
| nearly universal standard that permeates every aspect of
| human lives.
|
| [1]: https://aerosavvy.com/wp-
| content/uploads/2014/08/an05_cons.p...
|
| [2]: https://en.wikipedia.org/wiki/Flight_level#People's_Repu
| blic...
| sambaumann wrote:
| Wikipedia [1] implies it's to give them an incredibly large
| field of vision to spot prey, though the source it cites [2]
| seems less certain about that
|
| [1]
| https://en.wikipedia.org/wiki/List_of_birds_by_flight_height...
|
| [2]
| https://web.archive.org/web/20131011012320/http://blogs.bu.e...
| vardump wrote:
| The rockets at higher altitudes were all in wrong orientation. In
| reality, they don't fly straight up.
| timonoko wrote:
| Giant Space Bola is much more attractive. It is a 10000 km string
| with capsules at both ends. It rotates in sync with earth so that
| the speed at meeting point is the same. You just hop in and end
| up in space without much effort. Because it is freely floating
| you can move it around to avoid meteor impacts and other such
| shit.
| 243423443 wrote:
| Did you read Seveneves by Neal Stephenson? In the second part
| of the book, they use this and related technologies.
| arethuza wrote:
| I think those technologies are mentioned throughout the book
| - just at a much larger scale in the second part.
| daeken wrote:
| Bolos are used for spin gravity in the first part, but
| that's very different from the rotovators used in the
| second part. Both in concept and design. The key point with
| the rotovator is that the tip is moving at ~0m/s relative
| to the body it's orbiting when it's at its nadir, allowing
| you to just hop/grab on.
| M95D wrote:
| Incomplete. Where's the LEO, GEO, the counterweight?
| rob74 wrote:
| I think the idea behind this was less to showcase an actual
| space elevator and more to showcase what's going on at
| different altitudes. And above the Karman line it would have
| become pretty boring, especially if you want to go up to GEO
| and beyond where the counterweight of a space elevator would be
| located - the Karman line is at only 0.28% of the way to GEO.
| Using a logarithmic scale would have maybe helped, but not
| sure...
| M95D wrote:
| There are other presentations by this guy are long. I don't
| consider the space and the things we put between LEO and GEO
| to be boring.
| tstrimple wrote:
| I loved the visuals but space elevators are far more science-
| fantasy than hard science-fiction. We should move on to sci-fi
| tech that has more realistic applications.
| jaggederest wrote:
| Only for Earth. We already have materials that can do it on the
| Moon (Zylon, for example), though not with great tether-to-
| payload ratios (200:1 or more), and Mars isn't too huge of a
| stretch (huge like the mass of the tether, which would be in
| the thousands to one tether-to-payload ratio. Shipping 50,000
| tons of Zylon to Mars is a different beast)
| l5870uoo9y wrote:
| It is appreciated that you can change the temperature unit by
| clicking on it, and how surprisingly cold and changeable the
| temperature is as you travel up through the atomic sphere (down
| to -84C, -119F).
| petesergeant wrote:
| Some huh! moments...
|
| * Jeez, Everest is tall
|
| * They got a plane to 17km in 1938!
|
| * There was a paper airplane flight at 35km
| everyone wrote:
| An actual space elevator would need to be over 357 times longer
| though right?
|
| Awesome site!
| ta1243 wrote:
| What's really interesting is that a space elevator goes to
| Geostationary orbit by necessity. Getting to 100km vertically
| doesn't save as much as you might think when it comes to getting
| into orbit.
|
| To get into a very low earth orbit from an equatorial launch pad
| at sea level you need about 9.2km/s of Delta-V
|
| To get there from a 100km tall tower, you need about 8km/s of
| delta-V - about 85%.
|
| Think about how much scrolling there was to get to 100km.
|
| To get to the ISS you'd need to scroll 4 times further. Starlink
| and Hubble are another 100km beyond that.
|
| You start having radiation problems if you spend too much time
| above 600km.
|
| Aside from Apollo, the highest a human has been is about 1400km -
| 14 times more scrolling than this page.
|
| To get to GEO would require scrolling over 25 times further than
| even that.
| matheusmoreira wrote:
| How much delta V would be needed to reach, say, a circular
| orbit from GEO altitude?
| ta1243 wrote:
| Zero. By the time you get to GEO your are connected to a
| station which is in Geostationary orbit. Your 35 hour ascent
| at say 1000km/h will have accelerated you sideways to the
| required 3km/second with a sidewards acceleration of 0.002g
| throughout the trip.
|
| Of course you would be looking at a constant acceleration,
| not just a 1000km/hour trip. You'd probably be able to do the
| journey in a couple of hours with a reasonable acceleration
| and a rotating cabin (say 1.1g, meaning acceleration would
| slowly increase from about 0.1g at the surface, then after
| the flip point you'd decelerate at 1.1g). Even then sideways
| acceleration wouldn't be noticable (and your cabin could
| gimbal to just add it to vertical acceleration)
|
| That's the other crazy thing. A space elevator takes forever
| at elevator, or car, or even plane speeds. But with constant
| acceleration/decelleration you can have a trip in airplane
| style seats with cabin crew serving you caviar //
| scratchcards (depending on class of cabin). Your peak
| vertical speed would be in the region of 8km/second - way
| above Earth's escape velocity, but you wouldn't even notice
| the acceleration/deceleration. You'd slow down in under 15
| minutes.
|
| Or you wouldn't and you'd depart Earth at 8km/s, twice the
| escape velocity.
|
| (If you really wanted a fast departure you'd accelerate at
| say 1.2g and get upto 30km/s, twice the speed of New
| Horizons. 1.2g would probably mean you'd have the seatbelt on
| for the whole 40 minute trip)
|
| You could launch cargo to Mars at say 5G, which would get it
| there in between 10 and 45 days depending where it is.
| Obviously you'd have a problem slowing down when you got
| there.
| waxsum8 wrote:
| Lovely, great transitions!
| amelius wrote:
| The other direction:
|
| https://neal.fun/deep-sea/
| stared wrote:
| And "up", but shown sideways, and on a different scale:
| https://joshworth.com/dev/pixelspace/pixelspace_solarsystem....
| "If the Moon were only 1 pixel"
| amelius wrote:
| Neal also made one:
|
| https://neal.fun/size-of-space/
| novoreorx wrote:
| I'm here to find this one, thank you!
| amelius wrote:
| Where is Elon Musk's Tesla?
| fredoliveira wrote:
| Too far away to scroll: https://www.whereisroadster.com/
| nunodonato wrote:
| Wow, I'm really surprised to see some birds flying that high.
| Question: How the heck are they able to live normally at such
| extremely low temperatures?
| gherkinnn wrote:
| Amazing work as always. Paired with Wikipedia it makes for a very
| productive day.
| HelloUsername wrote:
| Previous discussion on 20-apr-2023
| https://news.ycombinator.com/item?id=35629972
| stared wrote:
| How on Earth do we know the maximal altitude for a pterodactyl?
| dpq wrote:
| Amazing work! One minor correction:
|
| > As particles from the sun hit the atmosphere, they excite the
| atoms in the air. These excited atoms start to glow, creating
| brilliant displays of light called auroras.
|
| The process is a bit more nuanced than that. The modern
| mainstream understanding is that the growing pressure of the
| solar wind makes the tail of the magnetosphere "contract" (sort
| of pushing it inwards from the sides), which leads to
| reconnection of magnetic field lines. Once the reconnection
| occurs, the magnetic field lines that remain bound to the
| geomagnetic dipole accelerate the particles on them towards the
| Earth => they slam into the atmosphere, exciting the atoms and
| generating the aurora.
| pfdietz wrote:
| Right. So the solar wind provides the energy that drives the
| aurora, but it's more indirect than just "solar wind particles
| hit the atmosphere". Instead, the solar wind is injecting
| energy into the magnetic field of the magnetosphere, and when
| reconnection occurs some of this magnetic energy is dumped into
| particles in the magnetosphere, some of which can then strike
| the atmosphere.
| hwillis wrote:
| Any discussion of aurora which do not mention space tornados:
| https://en.wikipedia.org/wiki/Space_tornado
|
| Is inherently incomplete. Not necessarily because they're
| needed to explain it, but they do need to be brought up at any
| time possible because they're cool.
| hnuser123456 wrote:
| I feel that way about galactic center filaments. They just
| scream "this region of space is not safe" in the most awe-
| inspiring way to me. 150-lightyear-long, magnetically
| powered, speed-of-light tornados. And there's hundreds of
| them.
|
| https://en.wikipedia.org/wiki/Galactic_Center_filament
|
| https://science.nasa.gov/asset/webb/milky-way-center-
| meerkat...
| kulahan wrote:
| These _are_ cool. I wonder how much they screw with
| satellites etc.? How predictable are they? It seems like it
| 's just a deadly, mostly-invisible wall of energy flying
| around at unbelievable speeds!
| whatsupdog wrote:
| No, thank you. Don't want any existential crisis today!
| pharmhax wrote:
| Neat! It would be amazing to see how the pressure changes with
| altitude in addition to the temperature.
| honkostani wrote:
| I missed that notice at where its says: Here be a near mars
| atmosphere in temperature, pressure (40 kms up) but not as
| hostile composition and with less radiation. Thats five Mt
| Everests high.
| hshdhdhehd wrote:
| Perfect. I think it just needs explanation of Karman line. Why is
| it 100km. What is the meaning?
| 0xEF wrote:
| It's my understanding that the Karman Line the conventionally
| accepted "edge" where you leave the atmosphere and enter outer
| space, but many call this out as a fairly arbitrary point,
| arguing that there is no measurable boundary. Useful as a point
| of reference for positioning, though. Neal possibly just used
| it as a marker but chose to not define it for this reason.
| tiborsaas wrote:
| It's an arbitrary number, which is a good enough measure to
| distinguish an aircraft from a spacecraft.
|
| Karman said that it's about this height where the aerodynamic
| lift and inertia being dominant are reversed.
|
| https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line
| imiric wrote:
| Lovely, as all neal.fun experiments. <3
|
| My favorite is probably https://neal.fun/infinite-craft/
|
| This type of interactive learning experience reminds me of how
| fun it was to browse Encarta back in the day. It was full of
| interesting facts, presented in fun interactive ways. As much as
| I love that we have Wikipedia today, a static web page with text
| and limited multimedia is far less engaging and conducive to
| learning.
|
| I think that Neal Agarwal and Bartosz Ciechanowski should be
| sponsored by the Wikimedia Foundation to create similar
| experiences on Wikipedia. That would do so much to facilitate
| learning for students of all ages.
| FailMore wrote:
| So great. Thank you Neal!
| orangebread wrote:
| WARNING: This guy's site is a trap for people with ADHD/OCD --
| the ease at which I was sucked into every link on his site made
| me nope the heck out.
|
| Beautiful work though.
| CaptainOfCoit wrote:
| Oh no, I scrolled all that way and didn't even reach some
| destination! Where does this space elevator go? No one knows!
| Would have been bit more satisfying if it ended up at a space
| station or something, as I think that's the purpose of the space
| elevator idea in the first place :)
| matheusmoreira wrote:
| I think it could but does not necessarily have to reach a
| station. The elevator just has to clear the atmosphere, right?
| As they say: once you're in orbit, you're halfway to anywhere.
| CaptainOfCoit wrote:
| > just clear the atmosphere
|
| But for what purpose? You just want to float around in a
| elevator carriage, aren't you going somewhere when you go
| with a space elevator?
| matheusmoreira wrote:
| Presumably the elevator would lift cargo, fuel, maybe even
| the actual rocket into orbit where maneuvering is easier.
| Once it's in space and in orbit, substantially less fuel is
| required maneuver.
| mrec wrote:
| There's a big difference between "clear of the atmosphere" or
| "100km up" and "in orbit". Orbit is more about velocity than
| altitude.
| neuronic wrote:
| Congrats, first time I noticeably hear my MBP M4 Pro fans and can
| feel the temperature through the keyboard.
|
| Amazing work, as always. I love neal.fun
|
| Edit: also good to know that paper airplanes have officially beat
| the SR-71, F-104 or X-43B with altitude record.
| mrec wrote:
| I dunno, by that rationale you could argue that Tesla Roadsters
| have officially beaten the X-43B's altitude record, couldn't
| you?
| Oreb wrote:
| How do we know how high pterodactyls were flying?
| flir wrote:
| Came here to ask the same thing. Hoping you get a response from
| an expert. I was vaguely under the impression they were mostly
| gliders... maybe it's something to do with thermals?
| xrd wrote:
| My 8 and 10 year old daughters love this site, often choosing it
| over Roblox during screen time.
|
| This is stunning and perfect.
| slrainka wrote:
| Wow, I just discovered Ruppell's Griffon Vultures from this. What
| a fascinating bird with high flying capabilities!
| tetris11 wrote:
| > Temperatures can reach <something very high> but the molecules
| are spread sobfar apart you wouldn't feel it.
|
| Conceptually I get, it's like being in a cold room that showers
| hot sparks on you from above occasionally...
|
| ...but I feel that the definition of temperature has been abused
| here slightly
| asimovDev wrote:
| I didn't take a look cause I didn't see "reject all cookies"
| button in the cookie popup
| TheDong wrote:
| Did you know if you open a page in a private browser window,
| once you close that page all the cookies vanish? It's even
| better than a button which might not even work.
| asimovDev wrote:
| It's purely out of principle because in a proper cookie popup
| rejecting everything should take the same amount of clicks
| that accepting everything does
|
| I do understand that this is one those generic ones (I saw it
| many times) which the original creator of the website just
| slapped on.
| temperceve wrote:
| This is just lovely. I, for one, have bought Neal a coffee!
| avmich wrote:
| Space elevator is not something which stands on the ground and
| grows up. It is something which lives on geostationary orbit and
| grows down from it to the Earth. If you cut the lower 1 meter of
| it, the rest will hang...
|
| ...that is, until a satellite will hit the cable above. Space
| elevator is built in the equatorial plane, all satellites cross
| it, so eventually every satellite is going to collide with the
| cable. For this reason the space elevator is incompatible with
| existing spaceflight, that's why even with nanotubes it's
| unlikely to be built.
| yreg wrote:
| The sound mixing is so smooth. Is it a simple fade with the right
| choice of melodies or is there more to it?
| pandemic_region wrote:
| That space elevator music 100% made my day, thank you!
| isgb wrote:
| > Space elevators are actually a possible idea being considered
| by scientists. > The hard part is making a strong enough cable.
| And finding enough elevator music...
|
| Most engineers would bring up a lot more issues than just finding
| a strong cable. Also, most attempts with e.g. carbon nanotubes
| have been abandoned ages ago
| https://www.newscientist.com/article/2093356-carbon-nanotube....
|
| - We don't have a good ascent mechanism other than rockets - and
| then we might just use rockets without building an elevator. - We
| don't have a good (and safe) descent mechanism. - Maintenance?
| Protection from space debris? Protection from oscillations?
| Ground-protection if the elevator collapses?
|
| This is dyson-sphere level of fiction. We can do back-of-the-
| napkin calcualtions on how things would work, but the
| practicalities make it completely impossible or impractical.
| mrkickling wrote:
| You didn't even mention the music!
| honkostani wrote:
| The material is actually not a problem, if you consider active
| structures. https://en.wikipedia.org/wiki/Active_structure
| https://en.wikipedia.org/wiki/Space_fountain
|
| Then again, when doing mega structures, a launch loop is more
| plausible.
| bombcar wrote:
| All we have to do is make the global religion require bringing
| a rock to a specific location; after long enough we'll have a
| mountain so high it extends out of the atmosphere!
| kubanczyk wrote:
| This presents a considerable risk of splitting English into
| several languages, none of them intelligible with the others.
| SSLy wrote:
| have you ever been to Newcastle?
| ben_w wrote:
| Aye man, wey aye, went doon there worra bairn, didn't ah?
| Cannae remember much like, was only a wee nipper at the
| time, knaa what ah mean? Me mam an' da took us doon the
| Toon when ah was nowt but a little'un, like. Divvent
| really remember owt aboot it proper, but aye, been the
| once when ah was just a littl' bairn, me. Proper yonks
| ago that was, pet!
|
| (Translation: yes, once as a kid).
| notahacker wrote:
| The deity in question would also have to smite purveyors of
| LLM translation. This might of course not be considered a
| drawback...
| rigmarole wrote:
| Related and recommended: Greg Egan "Phoresis" a sci-fi novel
| of two twin planets in extreme proximity to each other. (I
| think I read it in one of his anthologies.)
| hermitcrab wrote:
| To get to the Karman line (100k) a mountain with a 60 degree
| slope would require a base of 115km. A cone with 115km
| diameter base has a volume of 3.5x10^5 km^3. Which is
| 3.5x10^14 m^3, which is about 10^15 kg of rock. So it is
| going to take you a while!
| bombcar wrote:
| 3.5x105 km3 you say?
|
| 1.08321x1012 km3 is the volume of Earth, feasibility study
| done! _Implement!_
| hermitcrab wrote:
| The molten core probably isn't going to be much use.
|
| Surface area is 5x10^8 km^2. So it it 'only' the first
| ~2m of the crust (~6m if you don't count ocean).
| seanc wrote:
| Kim Stanley Robinson's description of a Martian space elevator
| falling and wrapping twice around the entire planet convinced
| me that they aren't a good idea.
|
| https://www.kimstanleyrobinson.info/content/clarke
| enraged_camel wrote:
| A version of this also happens in the first season of
| Foundation, the Apple TV series based on Asimov's novels.
| joenot443 wrote:
| Would you recommend that show to the HN crowd? The books
| are super well liked around here, for good reason.
|
| Apple's put out a staggering amount of content the last few
| years, I wasn't even aware this one debuted!
| Frotag wrote:
| It's pretty and scratches that scifi itch. I've only read
| a little of the books but it's supposedly an entirely
| different story that coincidentally shares character
| names.
|
| In terms of hardness, it probably on par with Expanse, so
| mostly technobabble with the magical tech only used when
| it's convenient for the plot. The abuse of
| "psychohistory" is particularly egregious. There's so
| many scenes where it's visualized a hologram of scribbles
| and they zoom in on more squiggles while divining the
| future.
|
| But again it's pretty, so if you're okay with drama in
| space, it's maybe a 8/10.
| bananaflag wrote:
| Not the OP, but that show is a severely dumbed down
| adaptation of the books.
|
| For example, each short story almost completely changes
| the cast (of course, with some descendants of characters
| appearing occasionally), as befits a saga that spans
| centuries. No producer was willing to run with that (as
| they didn't believe the audience smart enough to follow
| it would be big enough for the show to make a profit), so
| they introduced cryonics, clones, sorta-AIs (including
| robots out of their original context) to have some sort
| of continuing cast.
|
| Also, the books have a quaint 1940s (NOT 1950s as people
| usually say it) atmosphere, with excitement about
| "atomic" energy (changed to "nuclear" in the 1950s
| publication), distant descendents of the slide rule, and
| generally weird-sounding math and science, that the show
| totally drops in favor of a "contemporary" feel.
|
| And btw, the space elevator scene is lifted from Brin's
| Foundation's Triumph where it is described as a "future"
| event, part of Trantor's fall, predicted by Seldon's
| early team and trickled down to the general population.
| Frotag wrote:
| > For example, each short story almost completely changes
| the cast (of course, with some descendants of characters
| appearing occasionally)
|
| I wish directors were brave enough to kill off characters
| if it serves the plot. I get that there's IRL reasons
| that make it difficult (like contracts, scheduling, etc)
| but each new season accumulates more subplots to the
| point it's like a 30 minute episode is really a
| compilation of 3x 10-minute shows.
|
| This bugs me in multiple-protagonist books too. Just
| feels like an excuse to pad the page count with
| introductions and cliff hangers every POV switch.
| rtkwe wrote:
| It's definitely got problems as an adaptation of the
| Foundation series where it turns one of it's biggest
| themes on it's head by making a few people like Gail
| super special and having the answer to the crises where
| the books were more about setting up groups and
| organizations so that they as a whole had an advantage or
| edge that would be the answer to the crises he forsaw. I
| think it's mainly due to them wanting to have the same
| people across multiple seasons where the books were free
| to throw away the whole cast each time. Setting up new
| characters is much more expensive in shows/movies than
| books where you can just say what someone's 'deal' is and
| give them internal monologues to setup their internality
| where shows can't usually get away with that.
|
| I think separated from that there's a good enough show in
| there.
| shagie wrote:
| > Also, the books have a quaint 1940s (NOT 1950s as
| people usually say it) atmosphere ...
| The next day's hearings were entirely different. Hari
| Seldon and Gaal Dornick were alone with the Commission.
| They were seated at a table together, with scarcely a
| separation between the five judges and the two accused.
| They were even offered cigars from a box of iridescent
| plastic which had the appearance of water, endlessly
| flowing. The eyes were fooled into seeing the motion
| although the fingers reported it to be hard and dry.
|
| If you've got a copy of the ebook, search for "cigar".
| The use of tobacco as a way to demonstrate luxuries
| beyond the regular is there.
|
| In a recent re-reading of the series, I started having
| difficult with it in Second Foundation... and forced
| myself to finish Foundation's Edge. The amount of psionic
| ability and the... for lack of a better word "preaching"
| with the monologues was very much a science fiction of a
| different time.
|
| Foundation (the TV series) had to do updates for modern
| audiences and media. I'm not sure if trying to remain
| perfectly faithful to the books would represent them
| well.
|
| Foundation is a soft sci-fi about interactions between
| individuals and history and society. Trying to maintain
| the incidental harder parts of the written works that
| modern audiences expect to be somewhat consistent of far
| future technology with the 1950s lens on them would be
| quaint and a bit off-putting to people expecting future
| tech. He threw his cigar away and
| looked up at the outstretched Galaxy. "Back to oil and
| coal, are they?" he murmured--and what the rest of his
| thoughts were he kept to himself.
|
| They took the major points, and wrote to follow the
| general path from one point to another given the
| expectations of an audience consuming it often for the
| first time - 80 years after the original was written...
| and given constraints of the format and continuity of
| actors (60 minute episodes rather than as a chapter of a
| short story in Campbell's Astounding Science Fiction).
| jvanderbot wrote:
| I long for a level of posthumanism that you can do things
| like smoke and drink for fun without any worry for long
| term health effects.
|
| What at joy it'd be to fully experience life, not just a
| sanitized productized version, and have the safety net of
| perfect medicine to cure what ails ya.
| lelandfe wrote:
| My friends who wanted an adaption of the series hated it.
|
| My friends who like sci-fi enjoyed it.
|
| It is regardless very striking and high budget.
| Larrikin wrote:
| It's the best possible adaptation of the books as
| possible. They made some changes to allow for having main
| characters. In my opinion they also lighten the down side
| of the Mule story line and how the world works.
| tw04 wrote:
| I'll give apparently a controversial take. The show is
| great. If you're going into it expecting the books to be
| the guiding source material you'll be severely
| disappointed. If you go into it assuming you're watching
| a show that roughly takes high level concepts from the
| books but is its own thing and let it stand on its own, I
| think it's worth watching.
| georgeecollins wrote:
| I'm fine with series not following the books. But the
| show bugs me because it has great production values --
| particularly the third season -- and great actors. But
| the writing and plotting is all over the place ranging to
| very bad. It is a bit dumb and always pretentious. It's
| the 70's version of Battlestar Galactica of our age.
| ajmurmann wrote:
| I also found the pacing to be inconsistent at best.
| pavlov wrote:
| The Lee Pacing is consistently great though.
| senkora wrote:
| This is the issue that I have with many Apple TV+ shows.
| The production value is always very high, but it has no
| correlation with whether the writing is actually good.
| mrguyorama wrote:
| This is just the state of American video media production
| right now.
|
| Projects are massively expensive, including a lot spent
| on "looking expensive", but the writing cannot be as
| expertly crafted because the high expense means upper
| management craves purpose and control and meddles with
| things, and the giant "target" audience means you can't
| do anything interesting.
| MengerSponge wrote:
| Lee Pace is great, and the "genetic empire" is a
| brilliant solution to a hard problem unique to
| television.
|
| Brother Dawn: How often do we make this choice?
|
| Demerzel: You always make this choice.
| hermitcrab wrote:
| It's about 45 years since I read the books, but the whole
| idea of being able to predict the future of human
| societies accurately with maths seems rather silly.
| Especially since chaos theory became mainstream.
| kingkawn wrote:
| If you go into it looking for interesting sci-fi,
| especially the story of the Cleons, you'll enjoy it. If
| you go into it looking for Asimov's Foundation you'll be
| disappointed
| indoordin0saur wrote:
| I greatly enjoyed the first season (haven't seen the
| others) and I'm usually a curmudgeon when it comes to
| modern TV shows.
| noir_lord wrote:
| I enjoyed the first season, for me the others aren't
| remotely as good and I abandoned it halfway through the
| latest season.
| gilbetron wrote:
| The Mars one is much more interesting and traumatic :)
| indoordin0saur wrote:
| A fictional representation of a thing exaggerated for
| dramatic effect and to create plot tension shouldn't really
| convince you of many things at all. They're rarely accurate
| portrayals.
| ben_w wrote:
| In adition to being fictional, what would happen on Mars does
| not reflect what would happen on Earth as the Martian
| atmosphere is so much thinner than ours.
| michaelbuckbee wrote:
| In John Scalzi's Old Man's War, there is a discussion of how
| the more advanced society that they're interacting with
| deliberately put a space elevator on Earth, not because it was
| the easiest or cheapest solution, but as a sort of constant
| reminder of just how much more technologically sophisticated
| they were.
| cmpb wrote:
| Really great book (and series). Though it's not "hard sci-fi"
| by any means, the technology feels real enough to keep my
| brain from focusing on the holes and enjoy the fun
| philosophical and ethical problems that Scalzi comes up with
| shagie wrote:
| IIRC, it started out as a reimagining of Space Cadet by
| Heinlein but instead of the young it was with the old.
|
| After the first book, he then goes to explore all the
| questions that it brought up. The question of identity (to
| me) seems like the most reoccurring question.
|
| Btw, there's a new book in the series. The Shattering Peace
| was released in September.
| gizmo686 wrote:
| Isn't the entire point of the space elevator to be the
| ascent/descent mechanism?
|
| Once you have the cable up, you can grab onto it and pull
| yourself up.
| kingkawn wrote:
| Doesn't the weight of the cable itself let alone any payload
| preclude this from becoming real based on all plausible
| material science
| gizmo686 wrote:
| It's more of the strength-to-weight ratio than just weight.
| But yes, there is no known material that would work as a
| cable for a space elevator.
| bisby wrote:
| A space elevator doesnt just take you to the karman line
| (like in the OP website), to get to orbit, you'd need to get
| up to geostationary height. That's 22,000 miles.
|
| What's the best way to pull yourself directly vertical along
| a cable for 22,000 miles?
|
| What's the best way to descend 22,000 miles quickly, but also
| with a braking mechanism that isn't going to require a heat
| shield?
|
| Some sort of slow cable car going at 10mph even is going to
| take 2200 hours... 1000mph is going to take 22 hours still.
| That's a full day to orbit even going REALLY fast. And
| getting up to 1000mph vertically, for a sustained 22 hours...
| that's not an easy feat.
|
| And if the goal is just to get up past the karman line and
| use the elevator as a stage 1 for a rocket launch and
| detaching from the elevator while suborbital is fine, then
| it's a one way trip, and still need to re-enter the old
| fashion way.
|
| The scale of space makes all of the problems far more
| complicated (edit: not just the cable strength issue, but
| traversing the cable)
| oofbey wrote:
| You don't need to get to geostationary to get to orbit. The
| reason elevators need to get that high is because that's
| the lowest place you could "anchor" the top of the elevator
| to something fixed relative to the earth.
| notahacker wrote:
| Unless we're using it for humans the transit time isn't
| _that_ big a deal; "last mile" orbital transfer times are
| often measured in days anyway.
|
| That "last mile" bit is going to entail independent
| propulsion anyway. Getting to the altitude if the ISS is a
| mere 10 hour trip at a sedately 40kph which isn't
| unpleasant even for humans, but the ISS orbits at nearly
| 29000kph (as will you if you let go of the space elevator
| at that altitude) and the velocities are only half as scary
| at the far end, so your rendezvous anywhere other than one
| specific point in geo is going to be complicated. But
| you've saved the fuel costs of escaping the earth's
| atmosphere that's rather significantly more than the fuel
| costs of other bits of your satellite mission, including
| reentry. (At least until the costs of building and
| maintaining and protecting the elevator are factored in,
| but who knows what unobtanium costs?)
| gizmo686 wrote:
| > as will you if you let go of the space elevator at that
| altitude)
|
| Doesn't the teather have a constant (24 hour) rotational
| period at every elevation? That is significantly slower
| than the ISS
| datadrivenangel wrote:
| Skyhooks may allow for much easier access to space within the
| limits of likely practical carbon nanotube based structures. A
| rotating tether that orbits the planet could be timed to 'catch
| and throw' supersonic aircraft into space. Lots of engineering
| still required, but potentially actually feasible compared to
| space elevators.
| reaperducer wrote:
| _Most engineers would bring up a lot more issues than just
| finding a strong cable._
|
| He did. The elevator music!
| Symmetry wrote:
| Impractical on Earth given existing technology, but there are a
| lot of bodies in the solar system which have enough gravity to
| make them worth while but where they're small enough that the
| materials needed are ones we have right now. The Moon in
| particular.
| thijson wrote:
| I think a space elevator on the Moon would be more practical,
| pointing towards earth. The gravity force is smaller, so
| existing materials could work. There's not as much of an
| atmosphere to deal with. It would go past the L1 point between
| earth and the moon. It could be extended from the poles, where
| it's most likely where bases might exist.
| TiredOfLife wrote:
| I like the white text on white backgroud. Makes very easy to read
| Zobat wrote:
| Interesting how counter intuitive it felt to scroll up from the
| "landing spot". Even with the instructions right there on the
| screen I tried scrolling down at first.
| dzonga wrote:
| does anyone have the link to the money one ? scale of a billion ?
| jvanderbot wrote:
| 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 closer
| than that. Closer than your friends house or the local stadium
| probably.
|
| Look at a map or globe with that in mind and everything feels so
| thin!
| messe wrote:
| > it's just hard to go up
|
| Going up is the comparatively easy part, it's not exactly
| rocket science. Going fast enough sideways so you stay up there
| is the tricky bit.
| aDyslecticCrow wrote:
| > Going fast enough sideways so you stay up there is the
| tricky bit.
|
| nah, thats the simple part. getting up there efficiently is
| the difficulty. once we're up, its just a matter of force
| over time to create a nice orbit.
|
| The faster you go, the more friction you face, and the more
| heat and vibration your equipment must endure.
|
| Going slower reduce friction and stress but use more energy
| just negating gravity. Slow rocket is inefficient rocket.
|
| So we wanna leave the atmosphere as soon as possible, but not
| so fast that the rocket melts or engines collapse.
| Prefferably just below the sound barrier.
|
| once we're up, its pretty chill... until you wanna go down
| again. Slow rocket is alive rocket.
| raducu wrote:
| > once we're up, its just a matter of force over time to
| create a nice orbit.
|
| It depends what you mean by "up there". ChatGpt tells me
| you'd free fall from 1000 km to 100km in about 8 minutes.
| It also did the math that you'd need 1.65G of sideways
| thrust to reach orbital speed. That's quite a bit of force
| for spacecraft sized objects.
|
| If you have an actual space elevator, sure, you can go to
| close to geosynchronous altitude and by that time you'd
| have enormous sideways velocity just by being dragged
| sideways by space elevator and indeed it would be easy to
| propel yourself to orbit (above a certain altitude my
| intuition tells me you could let go of the rope and while
| you'd end up on an eliptise you'd still be in orbit)
| hermitcrab wrote:
| >ChatGpt tells me you'd free fall from 1000 km to 100km
| in about 8 minutes
|
| You trusted an LLM to do the maths when it is just s =
| 5t^2?
| literalAardvark wrote:
| It's not that simple though. The rocket equation still
| applies so it's almost as hard to do (you just get rid of
| atmospheric drag), and failed launches are also extra
| catastrophic.
|
| Even more, your delta v required is still huge. I can't be
| bothered to run the numbers right now but most of the delta
| v is in the orbital velocity, not in the altitude.
| BobaFloutist wrote:
| Delta v feels reductive, since your fighting negative
| acceleration to go up and a fraction of that to go
| laterally, no?
| lazide wrote:
| They're the same thing. Either you go sideways really
| fast, or go straight up really far (geo-synchronous
| distance).
|
| Either way, you need the same total velocity delta.
| JumpCrisscross wrote:
| > _since your fighting negative acceleration to go up and
| a fraction of that to go laterally_
|
| They're both acceleration. At high thrust, virtually
| equivalent.
| advisedwang wrote:
| Energy for 1kg to reach LEO (800km * 1kg * 9.8m/s2) ~ 8MJ
|
| Energy to reach LEO velocity ~ (1/2 * 1kg * (8km/s)^2) ~
| 32MJ
| nroets wrote:
| The rocket fuel needed to produce that 40 MJ weighs close
| to 1 kg, especially when you include the oxidiser. So the
| energy needed to accelerate 1kg of _payload_ to LEO
| velocity is much more.
| aDyslecticCrow wrote:
| But the energy needed is not an indicator of what is
| difficult or dangerous. Leaving the atmosphere intact is
| the most difficult part of launching a rocket going by
| failure rate. Of those that reach space, those that still
| fail often took damage from the launch.
|
| Once you're in space, force over distance until your fuel
| runs out.
| hinkley wrote:
| [delayed]
| Pxtl wrote:
| Which is another part of why a space elevator is nifty - by
| definition it extends out to a distance where you _are_ going
| fast-enough-sideways.
|
| Now, I have no idea how practical it is to build one (Angela
| Collier has a video saying it's kinda ridiculous), but it's a
| cool idea.
|
| https://www.youtube.com/watch?v=Z5aHMB4Tje4
|
| Also since rockets have moved away from hydrolox, it would be
| nice to have a greener launching system.
| raducu wrote:
| > Angela Collier has a video saying it's kinda ridiculous.
|
| There are other concepts like space fountains, orbital
| rings and sky hooks that seem more doable -- especially the
| sky hook seems close to do-able, especially on the Moon.
| BobaFloutist wrote:
| What if we just made a huge mountain? Space ramp? Is that
| anything?
| estimator7292 wrote:
| IIRC there is no material we're aware of that has
| anywhere near enough compressive strength to build that
| high, regardless of how wide the base is.
|
| Space elevators only (theoretically) work because the
| entire structure is in _tension_. And the only material
| we currently know of that can handle the tensile forces
| is carbon fiber.
| block_dagger wrote:
| It's NOT rocket science?
| Retric wrote:
| You can reach space using air breathing jets. You can't
| stay in space using air breathing jets.
| CobrastanJorji wrote:
| 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 been some (failed)
| efforts to get there, like the X-30.
| estimator7292 wrote:
| Can an air breathing jet actually attain those
| velocities? I thought most supersonic aircraft use
| rockets after a certain point
| LeifCarrotson wrote:
| "Most" supersonic aircraft are fighter jets and other
| military aircraft that use jet engines, not rockets. They
| may have afterburners that are much like a rocket that
| just injects jet fuel in the exhaust stream, but that's
| still using atmospheric oxygen.
|
| The issue, I think, is more about balancing drag and air
| intake at appropriate atmospheric densities for different
| speeds. An SR-71 Blackbird could fly at 85,000 feet
| continuously, and a MiG-25 set what I believe is still
| the air-breathing record max altitude by pulling a "zoom
| climb" (accelerating in higher-density air that the
| engines could use effectively, then pulling the stick
| back and coasting up through rarefied air too thin for
| the engines) to 38km or 123,000 feet.
|
| Most experimental hypersonic aircraft use rockets because
| that's what works.
| marcosdumay wrote:
| > Can an air breathing jet actually attain those
| velocities?
|
| There's no theoretical limitation on how fast an air
| breathing jet can move. You just have to redesign
| everything every few mach numbers, and deal with the
| atmospheric drag.
| Retric wrote:
| Basically when you cut thrust you must pass through that
| altitude again or escape orbit.
|
| So either fire a rocket in space to circularize the orbit
| or reach more than Earth's escape velocity 25,020 mph
| (11.186 km/s, 40,270 km/h) ~ Mach 32.6, due to some drag
| in air to thin for any kind of air breathing engine to
| work.
|
| X-30 was aiming far lower ~Mach 20. Nuclear could make it
| more realistic than any form of chemical combustion. It
| might be physically possible using Hydrogen but you're
| talking generating extreme thrust at vastly more extreme
| conditions than the space shuttle's retry.
| tatjam wrote:
| Well you can't reach a high orbit using air breathing
| engines because your impulse must be given within the
| atmosphere, and then your trajectory inevitably re-
| intercepts the atmosphere (unless you achieve an escape
| trajectory) and would decay quickly. You can get around
| this by packing a small rocket engine and circularizing
| on apogee!
| ianburrell wrote:
| There isn't enough air at high altitudes for jets to
| reach space even if you count 100km as space.
|
| The highest jet record is 37km in MiG-25. The scramjet
| record is 33km. I found source that says the limit is
| 40km at Mach 15.
| Retric wrote:
| The MiG didn't reach 37km in level flight, which is
| probably where Mach 15 @40km comes from. Instead the MiG
| was doing a nearly parabolic trajectory starting with
| Mach ~3 worth of kinetic energy.
|
| The NASA X-43A hit Mach 9.6 as an air breathing engine
| (test used a rocket at lower speeds for cost reasons)
| which in theory should be capable of ~65 km assuming it
| could survive a similar maneuver. Actual limits are
| heavily influenced by how much thrust you can generate
| while slowing down etc not just max velocity.
|
| So yea no actually built air breathing aircraft can hit
| space, but it's within the realm of possibility.
| JumpCrisscross wrote:
| You can build a decent sounding rocket with just trial and
| error.
| sebastiennight wrote:
| This is where Douglas Adams was right, of course:
|
| > There is an art, it says, or rather, a knack to flying. The
| knack lies in learning how to throw yourself at the ground
| and miss.
|
| You're not going sideways - you're actively falling
| continuously, but somehow missing the ground for the entire
| length of your orbit.
| lurquer wrote:
| > it's just hard to go up.
|
| Eh. Going up is easy. A Frenchman, a sheep, duck, and rooster
| solved the whole 'up' thing over two centuries ago.
|
| But going DOWN? That's far more difficult. What wonders may lie
| beneath our feet: vast caverns, ore, underground oceans... hard
| to get to though.
| estimator7292 wrote:
| Just dig a big hole, duh
|
| /s
| sebastiennight wrote:
| If memory serves well, Frenchmen solved the problem of going
| up in two ways, and the one you quote seems like a lot of hot
| air to me. I mean, if you follow that line of thought, the
| literature says an American would get to the Moon in 19 days
| or so.
|
| The other French method included two dogs, a bunch of
| chicken, and a very large cannon, which had quite a bit more
| showmanship.
| Liftyee wrote:
| True statement, but disclaimer: your friends may be closer if
| you live in a European city without American suburban sprawl...
| amflare wrote:
| For a standard globe that you might see in a classroom, the
| Earth's atmosphere is about as thick as the paper glued to the
| outside that displays the map.
| andersa wrote:
| That's a fascinating comparison, never seen it visualized
| like that before.
| mk_stjames wrote:
| 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 defining the edge of
| what the atmosphere is, that is 100,000 meters. Solving for X
| ... (13" / 12742000 m)=(X / 100,000 m). gives us an
| atmosphere thickness of approximately 0.1". -----
|
| Paper glued to the globe would have a thickness of maybe,
| 0.004" (thin paper) to 0.012" (like a card stock paper)....
| so that analogy is off by an order of magnitude or more.
|
| Even if you use the mesosphere as the definition for the top
| of the atmosphere, that is still 85,000 meters and thus
| similar.
|
| People can check the numbers I used.
|
| * Perhaps the analogy should go more like: the thickness of
| the cardboard sphere the globe is made out of is about the
| thickness of the atmosphere. Because, having completely
| destroyed a globe once in my youth, I remember the cardboard
| shell being approximately a tenth of an inch thick. But,
| that's maybe not a great reference for the analogy because
| not everyone has cut apart a classroom globe....
| shagie wrote:
| 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 :: http
| s://www.wolframalpha.com/input?i=16+km+*+%2812%22+%2F+Ea...
|
| 4
|
| Note that that's copy paper rather than card stock...
|
| Adjusting this to 5.6km (the 50% atmosphere amount) ...
|
| 5.6 km * (12" / Earth diameter) / thickness of paper :: htt
| ps://www.wolframalpha.com/input?i=5.6+km+*+%2812%22+%2F+E..
| .
|
| 1
|
| So it's a matter of selecting the proper globe, proper
| paper, and proper threshold for the atmosphere.
| vee-kay wrote:
| I just love such nerdy debates on HN on a hypothetical
| scenario/example.
|
| I think this thread would also be loved by the nerdy
| folks at https://Reddit.com/r/theydidthemath
| shagie wrote:
| If I recall correctly... my very first post on Reddit was
| doing calculations for a (practically immortal) person
| eating beans and storing the flatus for a trip to the
| moon (searching shows that this is a not-infrequent
| request). It was only concerned with quantity - not
| storage or the engine.
|
| ... and the source document for the numbers was based on
| a paper that is fairly easy to find given the proper
| keywords in google search...
| https://pubmed.ncbi.nlm.nih.gov/1648028/ (and I learned
| that methane more rare in flatus than not).
| vee-kay wrote:
| Hilarious!
| gertlex wrote:
| I wonder how standard this globe size is. My mental one is
| the one we had at home that was about 15" in diameter I'd
| guess.
|
| Another comment talks about atmosphere being a 1 mm layer on
| a grapefruit... so definition of atmosphere extents might be
| different in these two anecdotes.
|
| (edit: I submitted this comment two minutes after another
| comment did the math on the globe/paper layer version...)
| dhosek wrote:
| And the bumps for the mountains on that globe (assuming you
| had a fancy one) were gross exaggerations:
|
| https://dahosek.substack.com/p/one-million-stories
| rich_sasha wrote:
| 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%.
| hinkley wrote:
| I didn't think that sounded right but went and did the math
| and you're actually round _up_ to .2%. It's .156%. And that's
| already a mind numbingly scary place to be.
| arkmm wrote:
| As a follow-up to this, even though water makes up 70% of the
| Earth's surface, it's only 0.02% of the Earth's mass.
| rsynnott wrote:
| It isn't even necessarily _that_ hard to go up. It's just hard
| to go up _and reach orbital velocity_.
| aquafox wrote:
| > Our liveable breathable atmosphere is razor thin compared to
| the size of earth.
|
| If earth were a grapefruit, our atmosphere would be ~1mm thick!
| hinkley wrote:
| 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 don't
| have to worry about the ignition timing because you're not in
| free fall.
| rozab wrote:
| The most important feature of a launch site is having no
| populated areas downrange. Kilimanjaro would have Mombasa
| downrange.
|
| 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.
| blueflow wrote:
| > The most important feature of a launch site is having no
| populated areas downrange. Kilimanjaro would have Mombasa
| downrange.
|
| This was part of the Plot of Halo: ODST, where fragments of
| the space elevator collapsed onto New Mombasa.
| hinkley wrote:
| The description of a space elevator falling is rendered
| in horrific detail in Kim Stanley Robinson's Mars
| trilogy.
|
| Twice.
|
| Because the only known material strong enough at the time
| was diamond, and diamond doesn't ablate much when falling
| through atmosphere.
|
| One of the early space elevator research companies
| specifically designed a cable that was made by stacking
| successive layers of material both to slowly increase
| carrying capacity by building the tether in iterative
| layers, and hoping it would ablate or at least reach a
| quick terminal velocity in the case of catastrophic
| failure.
|
| It is undoubtedly the case that the senior staff on that
| project were familiar with the Mars trilogy.
| hinkley wrote:
| Mombasa is the shortest path to the ocean from the top of
| the mountain, that's true. However that is not a good angle
| for an equatorial orbit.
|
| What's the downrange safety cone look like for space launch
| sites around the world? A little S curve in your insertion
| orbit would certainly waste a bit of delta V. But not all
| orbits are equatorial anyway.
| chasingthewind wrote:
| I find it curious that the Lockheed Vega is chosen as "Amelia
| Earhart's plane" since most people would probably associate her
| with the Lockheed Electra, the plane she was flying when she
| disappeared. It's analogous to saying that Ernest Shackleton's
| ship was the Nimrod...not wrong, just odd.
| cheraderama wrote:
| Doomscrolling isn't supposed to feel so right...
| cl0ckt0wer wrote:
| I watch AC's video on this, it was quite entertaining:
| https://www.youtube.com/watch?v=Z5aHMB4Tje4
|
| If you like factory games and space elevators, then try
| Satisfactory!
| Sohcahtoa82 wrote:
| I really wanted to enjoy Satisfactory, but I really struggled
| with building a factory in first person perspective.
|
| Factorio, Dyson Sphere Program, Captain of Industry...loved
| them all. Satisfactory? Just wasn't for me.
| bentt wrote:
| Seems like even before we do an elevator, we should get
| _something_ tethered to the ground to be in space. Like...
| anything! That'd be a huge accomplishment.
| kmacdough wrote:
| No engineer actually thinks a space elevator is possible. It
| would be a silly waste of resources.
| hermitcrab wrote:
| >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.
| cauliflower2718 wrote:
| I was wondering about this, because the link shows a bunch of
| birds in the "death zone".
| hermitcrab wrote:
| Different species will have different 'death zones'. I'm not
| sure any bird would stay at that height for 10s of hours
| though.
| jmyeet wrote:
| Space elevators aren't going to happen. Not in Earth's gravity
| well anyway. Even if you can find a material strong enough (and
| that's a big "if"), you still have to traverse 50,000km to get
| from Earth's surface to geosynchronous orbit to get the benefit.
|
| You know what does make way more sense and is way more
| achievable? Orbital rings [1].
|
| Basically, put some copper wire in space, orbit it at ~8km/s, run
| a current through it and then you can reset structures on top of
| it (magnetically) and those structures are _fixed to the Earth 's
| surface_. You can technically run a cable from 100-150km up to
| the surface and run a gondola into LEO. This would transform both
| Earth transport and interplanetary travel. You accelerate
| something on the inside (Earthside) of the ring at ~2G, like with
| a maglev train, and you have enough velocity to escape the Solar
| System.
|
| [1]: https://www.youtube.com/watch?v=LMbI6sk-62E
| hermitcrab wrote:
| This is a really nice piece of work.
|
| Question: Why does the Douglas Skyrocket have its undercarriage
| down at 25km?
|
| Unsolicited feedback: It would be nice to be able to click on an
| item and see some more information. Perhaps just a hyperlink to a
| wikipedia entry.
| lolive wrote:
| Why not scroll up to 36000 kms, so we can reach the end of the
| cable? #iFeelCheated !
| kmacdough wrote:
| Because space elevators aren't actually possible so it doesn't
| really matter.
| xipho wrote:
| Notes on mushroom clouds are sobering.
| cranx wrote:
| This is cool, but the UX of the arrows should follow the scroll
| mode of the device. You drag down on an iPhone to scroll up.
| Following the arrow and dragging up causes nothing to happen
| Aaargh20318 wrote:
| This. Took me a while to realize you have to scroll down, not
| up.
| 01HNNWZ0MV43FF wrote:
| Deep links would _kill_ on this. I'd love to be able to link
| someone to the Blackbird. (25,700 meters)
| nodra wrote:
| Just came to say that this is so cool. Great work.
| GMoromisato wrote:
| 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.
| kmacdough wrote:
| I mean the idea isn't actually real or practical. It's a
| thought experiment that makes for some fun calculus. No one's
| actually going to try and build one.
| gtowey wrote:
| actually geosync isn't the top. You need to extend beyond that
| & have a counterweight that balances the weight of everything
| below the point of geosynchronous orbit. Otherwise it would
| fall down.
| dredmorbius wrote:
| From the same site, there's the Size of Space page:
|
| <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).
| moat wrote:
| That was fantastic.
|
| My biggest surprise (and confusion) was just how high butterflies
| and bumblebees go.
| mikkupikku wrote:
| > _On June 21, 1972, Jean Boulet of France piloted an
| Aerospatiale SA 315B Lama helicopter to an absolute altitude
| record of 12.440 kilometres (40,814 ft).[68] At that extreme
| altitude, the engine flamed out and Boulet had to land the
| helicopter by breaking another record: the longest successful
| autorotation in history.[69]_
|
| I just had to look that up. Absolutely incredible.
| bilsbie wrote:
| Why would cranes fly so high?
| simpaticoder wrote:
| Given the title "Space Elevator" I was expecting some more
| information on a hypothetical space elevator cable. Assuming
| humans can manufacture defect-free nanotubes at any length and
| can combine them into thicker cables, you could specify at every
| height a) the cumulative mass of the cable, b) the thickness of
| the cable at that point, and c) the stress experienced by the
| cable at that point. You could further break c down into the
| gravitational vs centripetal forces on the cable at that point.
| kmacdough wrote:
| Super fun!
|
| I do always have to object to comments like "space elevators are
| possible," "scientists have studied" and "would save money".
|
| It's a fun thought experiment, nothing more (for now). You can do
| some calculus to estimate the necessary strength-to-weight ratio
| based on centripetal and gravitational forces. Single carbon
| fibers seem to meet this optimistic criteria.
|
| But there are many forces left out. Many practicalitites left
| unconsidered. Why? Because there is no scientific community that
| believes it's vaguely achievable with near-future technology.
| It's simply not worth investing the outrageous resources required
| to do a vaguely useful viability analysis.
| dima55 wrote:
| I like looking at these, but does why does it have to redline my
| cpu?
| jedberg wrote:
| I like how the height is measured in metric but the temp is
| measured in imperial.
| nopakos wrote:
| You can click on it to change to Celsius!
| melenaboija wrote:
| Holy guacamole, common birds like cranes fly high.
|
| https://en.wikipedia.org/wiki/List_of_birds_by_flight_height...
| araes wrote:
| The biplane part (Caproni ca 161) right after the "you should put
| on a spacesuit" comment got my notice, so I checked. Actually
| vaguely fascinating that in 1938 the Italians had Mario Pezzi
| wear an electrically heated pressurized suit [1], an airtight
| helmet [2][3], and sit inside of a pressure cylinder [4] to fly
| at 17,083 m (56,047 ft) in a propeller-powered biplane. Seems to
| have barely been mentioned afterward though, as it's difficult to
| even find imagery.
|
| [1] https://en.wikipedia.org/wiki/Mario_Pezzi_(aviator)
|
| [2] https://static.thisdayinaviation.com/wp-
| content/uploads/tdia...
|
| [3]
| https://www.enricopezzi.it/fam_pezzi/mario_pezzi/images/MP_1...
|
| [4]
| https://www.reddit.com/media?url=https%3A%2F%2Fi.redd.it%2F4...
| mcv wrote:
| I honestly expected to be scrolling for a couple of days to reach
| geostationary orbit.
| grishka wrote:
| I get it that it requires yet-impossible materials to build a
| space elevator that goes all the way to space, but what if we
| instead build one that only extends high enough to clear the
| thickest layers of atmosphere, so rockets could be launched from
| there for massive fuel savings?
| tgsovlerkhgsel wrote:
| We can't practically build a tower that tall. A space elevator
| would work by hanging off a counterweight (possibly more space
| elevator cable) which means it needs to go past geostationary
| orbit.
| vpribish wrote:
| the space elevator has to go a LOT higher than that. also, the
| landing gear is down on the reentering shuttle. The big thing
| people don't get is that orbit is about sideways speed not
| altitude and this does nothing to address it. I don't get the
| hype for this, it's cute but not much at all.
| ebbi wrote:
| "Temperatures in the thermosphere can reach 2,500degC, but
| molecules are so far apart that you wouldn't even feel it."
|
| I don't have a science background. But how does this work? If you
| can't feel it, how would you measure it?
|
| Space boggles my mind I love it!
| shmerl wrote:
| Cool, I had no idea bumblebees can fly that high.
| DavidPiper wrote:
| I found this strangely emotionally affecting. Probably on account
| of the music, but I was really struck the vastness and loneliness
| as the elevator went higher and higher (and we're still nowhere
| close to the moon).
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