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!
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.
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....
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).
Did you account for the weight of storage? Because I would think the tyranny of the rocket equation for such a low ISP would cause various levels of impossibility, not to mention the problem of getting enough thrust.
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...)
> 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.
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.
That whole "tyranny of the rocket equation" thing is why I am surprised the actual first stage for launching a rocket is NOT a ground based reusable "up-chucker".
Basically, I would have thought that any momentum that can be imparted to the rocket before it has to rely on its self propulsion would be a huge help. Not talking about eliminating self propulsion, just an assist so the rocket could carry a larger payload or be smaller or whatever.
IE like a variation on Jules Verne's big gun for throwing the payload up there but engineered to be plausible and having the rocket still be self propelled. And safe.
But we don't seem to do this. So why?
Edit: First part of video [0]. Apparently it's not completely dumb. Just stupid-hard/impossible to do practically at the size required for big rockets and payloads. But small ones might work. Maybe.
Building your rocket to survive the upchucker costs more than the savings from being upchucked.
Chuckers are the optimal large scale solution for airless bodies, but they're horizontal. You spread the acceleration out over a very long distance so you don't need a super beefy spacecraft and your humans won't turn to goo. Basically, a maglev train except it has track above as well as below and it doesn't have a maximum speed. Wrap one around the lunar equator and it can eject anywhere from sundiver to interstellar escape with human-tolerable acceleration.
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.
Failures rate is even less a suitable indicator. Going up 100km is achievable by a simple single stage solid fuel rocket. Going to orbit requires way way more complexity, including a giant first stage that can fail in atmosphere.
The best way I’ve seen it described is that the first 9.8 m/s² of thrust only makes you hover in place. So the more g forces you generate the higher the efficiency of the engine - as long as thrust per kg of fuel doesn’t dip too far.
This all changes in outer space, where 0.01g is a valid propulsion mechanism for long duration missions.
Yup. Look at the launch trajectory of the Webb telescope. The upper stage engine was too weak for the orbital insertion and the booster had to waste energy putting it higher than need be so the upper stage engine had altitude to trade for time to keep the telescope from hitting the atmosphere.
But it was the optimum solution because that engine had a long burn to take it to L2. Hauling less engine to L2 was worth more than the loss of the engine not being powerful enough to fight gravity.
Actually, not quite. You tolerate a bit of extra fire in exchange for reduced gravity loss. Going straight up until you clear atmosphere is not the minimum energy trajectory.
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.
> 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)
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.
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.
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!
"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.
> 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.
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.
Nobody has been able to build one, but I'm not aware of any proof that it's impossible. You need some way to build an engine that doesn't appreciably slow the air that's passing through it.
I've worked out one that "can" be built (it's beyond ridiculous, though.)
Build towers around the equator. Build a ring around the equator on those towers. Build a ring inside the ring, maglev supports. Evacuate the ring, spin the inner ring above orbital velocity. The objective is to generate as much outward force as the weight of the entire assembly including the towers.
Do it again, on top of the first one. Keep doing it until you reach synchronous orbit. If you want to go higher the inner ring is not moving, exerting downward force countering the outward force of the rest of it being above orbital velocity.
Forces:
1) Compression on the towers. Note that this goes to zero as tower height goes to zero.
2) The outward force on the ring exists across the whole ring, but the downward force of supporting the towers only exists where there is a tower. Your ring needs to be stiff enough to counter this. But, again, note that this force goes to zero as the space between towers goes to zero.
3) Maintaining a very hard vacuum in the structure.
We know how to do #3, the others must have answers. Thus it can be built.
Nothing else is feasible with current technology, the taper of the cables is highly dependent on the strength of the material (in tension, an elevator is based on always pulling out as the upper end isn't hooked to anything.) You need much better than anything we can currently do before the taper blows up so badly you can't build it.
> 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.
Fountain--while it could be done in a perfect world I do not believe it would be feasible and the whole thing is so vulnerable to disruption. Dragon's Egg got it very wrong, if one of your fountain bits misbehaves it misbehaves very badly. They're moving way above orbital velocity if they hit something that energy is promptly liberated. The Cheela couldn't catch those rings, they had to be moving at high relativistic speeds and would have hit with something akin to antimatter level force.
Orbital rings--only if you have elevators. Remember, the Ringworld is unstable. So is every other planetary ring.
I do not recall numbers on hooks so I will not address them.
The Moon has a whole different set of problems. There is no synchronous orbit, elevators must go above synchronous orbit, so the normal version can't exist. Nor can anything stand up to be yanked around by the Earth.
But there are two cases that avoid the yanking problem: pointed towards and pointed away from Earth. Current cables are good enough for a useful Earth-pointing cable. The free end dips below synchronous orbit, but it's moving very slowly. You do what people think rockets do--go up. It takes a lot less energy to catch the cable than it does to even reach orbit.
How to have such a cable in an environment with geosynchronous satellites is another matter...
There's also another interesting cable situation. Cable on Mars? Iffy--and those two moons would be a major problem. But flip the problem over--put the cables on the moons. The low end dips into the atmosphere at aircraft-type speeds. The cables can toss to each other. The high end can capture/eject to Earth or the asteroid belt.
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.
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%.
I might have messed it up, but as a follow up to your follow up, I think the depth of the ocean is comparable to the width of a single human hair compared to the head.
If you inflate a 18cm diameter head to the size of our planet, a 75um hair would be about 5km wide - which is about the average depth of our oceans.
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.
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.
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.
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.
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.
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.
> 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.
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.
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.
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!
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.
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!!
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.
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.
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.
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?
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.
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.
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.
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.
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.
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.
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.
> 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.
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.
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.
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.
If you blow the cable apart at a few important points the mass that falls either hits fairly near downrange from the tether, or does not hit at all. Have a group of range safety officers for the charges and a law that when on duty they are expected to shoot any politician that contacts them. (I'm thinking of Fukushima. We need to vent the reactor or it will blow! You can't vent until the city has been evacuated. The reactor didn't listen to the politicians.)
> 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.
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?
At first I was confused by this because the Kármán 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.
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?
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.
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.
> 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.
Orbital and escape velocities??? The elevator is sitting over a stationary spot... it's moving at earth's rotational velocity. Only the portion above the GEO anchor is moving at orbital velocity.
But it has altitude. The stuff that's low down doesn't have a lot of orbital velocity, blow the cable and it falls nearby. And the stuff far away has enough velocity that it goes into a very eccentric orbit rather than hitting the atmosphere.
Just because it's moving below circular orbital speed doesn't mean the periapsis is in the atmosphere.
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.
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.
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.
> 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?
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.
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.
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.
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.
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).
Yup, it's not like a video game where you get instant notification/identification.
And it's why we have been so worried about Russian nukes--they have used liquid fueled birds, they can't be held ready to launch. Such birds are pretty much only useful for a first strike as they won't be able to launch them once incoming missiles are detected unless they're being held at launch ready (and they can't do that for too long.)
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.
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.
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.
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)
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.
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.
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.
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.
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.
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.
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.
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.
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.
#1 is one of the things they typically get wrong in stories.
Climbing the cable is a nightmare, especially as it gets thicker as you go up. Thus do not climb the cable! Rather, when the cable is built a whole bunch of anchors are built into it. You are not climbing the cable, you are climbing a track on the side of the cable. The cable's job is to support the track plus any load on it.
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.
> 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 :-)
> 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.
Have you ever seen a megavolt power line? Note how far apart the wires are. They are actually a bit farther apart than they really need to be because it is designed to tolerate a large bird with spread wings, but they still need quite a bit of distance. I believe you can tolerate a closer spacing once you're out in space and have no possibility of a plasma arc.
Indeed, I have not, however, I have looked up the breakdown voltage of vacuum at those altitudes, as long as the graph wasn't completely fictional, in that part of space even just 2 cm (barely, but it does) support a megavolt.
> 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.
> 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).
Dielectric strength of vacuum is 20kv/inch. Thus your megavolt needs 50 inches of separation at an absolute minimum. And you're operating this in space where you have ionizing radiation. Free electrons with a big voltage differential? You're describing a vacuum tube.
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.
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
Thanks! I found a funny hack: DVD logos generate stimulation per bounce, so ... let them fly for a few seconds, then resize window to small size and back. Lot of bounces as the logos get caught by the moving edge :).
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.
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.
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.
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).
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".
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.
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.
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.
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.
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.
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.
> 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...
- 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
> 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).
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.
> 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.
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.
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.
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.
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
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.
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!
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.)
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!
To get to the Kármán 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 3.5×10^5 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!
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.
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.
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)
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?)
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.
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.
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
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.
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.
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?
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.
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).
Why isn't there an elevator to the highest altitude where an elevator could be built, and then spacecraft can propel from there. It should still reduce fuel costs and the cost to construct space craft?
Would powering the cable permanently, with a power station at the bottom and a constant feed of water for super-heated steam thrusters work? Just throwing scifi at it. I'm just curious why it has to be one component or why the weight can't be supported by propulsion. I'm guessing the TL;DR is the numbers just don't work out?
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?
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.
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.
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
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.
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.
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.
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).
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?
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.
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 :)
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.
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.
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.
Loved this site. Only thing I could think to add would be the ability to click each item and be taken to a wiki page or some further source of information about the object.
> On June 21, 1972, Jean Boulet of France piloted an Aérospatiale 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.
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.
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.
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.
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)
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.
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 Kármán 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 Kármán line is at only 0.28% of the way to GEO. Using a logarithmic scale would have maybe helped, but not sure...
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.
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.
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.
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.
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).
