The foundry that made that manhole cover has some great potential advertising claims.
This reminds me of that quote from Mass Effect:
“This, recruits, is a 20-kilo ferrous slug. Feel the weight! Every five seconds, the main gun of an Everest-class Dreadnought accelerates one to 1.3 percent of light speed. It impacts with the force of a 38-kiloton bomb. That is three times the yield of the city buster dropped on Hiroshima back on Earth. That means: Sir Isaac Newton is the deadliest son-of-a-bitch in space! (…) I dare to assume you ignorant jackasses know that space is empty! Once you fire this hunk of metal, it keeps going 'till it hits something! That can be a ship, or the planet behind that ship. It might go off into deep space and hit somebody else in ten thousand years. If you pull the trigger on this, you are ruining someone’s day, somewhere and sometime!”
“What is Newton’s first law of motion?”
“No credit for partial answers!”
That first mass effect can’t be beat for setting the stage and immersing you in the world.
I can hear the VA in my head lmao
Edit: I like mass effect I don’t have a good memory
That quote is not from the first one though, it’s from the second one
Balls exposed 🙀🙀🙀🙀
Citadel lobby, yes.
Ummm, not sure where they got these numbers from but Earth’s escape velocity is not 7000mph and escaping the sun’s gravitational pull (leaving the solar system from Earth) is not 30,000mph. Respectively the numbers are approximately 25,000mph and 94,000mph. You’re welcome.
Gotta love Tumblr. Just massive amounts of disinformation and bullshit all the time.
Also it would have atomized.
That’s 11.2 km/s and 42.1 km/s.
Also, even if the manhole cover was going at above 12 km/s the trajectory has to be right for that to result in orbit. Most paths it would take would result in it going up and then coming back down again. Similarly, if somehow it did manage more than 50 km/s and wasn’t destroyed in the atmosphere, it might have the velocity to escape the sun’s gravity, but probably wouldn’t be on the right path to do it. Most likely it would fall into the sun.
So, assuming the 125,000 mph (55 km/s) velocity is correct, the most likely outcome is that it was a reverse-meteor, something that burned up going up through the atmosphere, not down. And even if it did have enough speed to get out of the atmosphere, and there was enough of it left, it most likely fell right back down through the atmosphere somewhere else, either burning up on re-entry or hitting the ground (or the water) somewhere else.
Ignoring that it burned up and ignoring losses due to drag if it somehow didn’t. Isn’t the point of escape velocity that it explicitly won’t come back down.iar least not on earth. Your trajectory won’t matter as you have enough velocity to escape the gravity of earth and will orbit the sun. Further if you managed the solar system escape velocity you will end up orbiting the galactic core. Trajectory doesn’t matter if you have escape velocity. Correct trajectory just minimizes the delta v needed to reach that escape velocity.
At least that’s all my recollection.
Escape velocity means you could stay in orbit. It doesn’t guarantee anything if you launch at the wrong angle.
That is not the definition of escape velocity. Escape velocity is the minimum velocity to escape a body’s gravity well entirely. Orbital is much lower
Exactly. It’s the minimum speed required to get into orbit assuming you get the direction correct. If you launch vertically, you’ll almost certainly come back down, no matter how far out into space you go. The only consideration is that if you go far enough out you might be influenced by the gravity of something else like the moon which could change your trajectory.
That is not the definition of escape velocity. Escape velocity is the minimum velocity to escape a body’s gravity well entirely. Orbital is much lower
correction to your correction: it would not fall into the sun, falling into the sun is basically impossible, it would just end up in a highly eccentric orbit around the sun.
Yeah, “fall into the sun” was sort of hyperbole. If it truly got out into space and was going fast enough to escape Earth’s gravity, it would start orbiting with earth’s orbit plus some delta. Out of all the possible angles it could leave the earth, there are probably 2 angles where it would directly hit the sun One is the angle that cancels out all the orbital velocity of the earth and sends it directly at the sun, the other is the one that does the same but sends it directly away from the sun. Of all the possible trajectories on the surface of a sphere, only those two tiny solutions would end up with it contacting the sun, everything else would result in an orbit.
Of course, given enough time, it’s pretty likely that if it isn’t collected by a planet, it will eventually end up in the sun. There isn’t much friction in space, but there’s a tiny bit: solar wind, micrometeoroids, etc. Eventually its orbit would decay and it would stray too close to the sun.
yeah, and it is not “research” to check it. They literally teach it in primary school physics.
Not in our freedom schools!
I mean, what for? Knowing that number isn’t a life skill.
94000mph is relative to the sun’s surface. Relative to the Earth’s surface, it is around 37000mph, which means they were still wrong.
Not according to Wikipedia. At Earth relative to Sun is 42.1 km/s = 94,175 mph. From the sun’s surface is 617.5 km/s = 1.38 x 10e6 mph.
42.1 km/s is the speed required relative to the sun’s surface for objects launching from Earth’s surface. You need to look at the value labelled V_te, which is the speed relative to the minor body the object is launching from. In this case, it is 16.6 km/s.
I like how they are implying the speed of light is only 500000mph (as opposed to 671,000,000 mph or 1,080,000,000kph)
?
Ah sorry, I should have specified that the post not only got the escape velocity wrong as you pointed out they also got the speed of light wrong near the end.
I didn’t see that reference but the image is all blurry now.
deleted by creator
Man. I haven’t seen an ifunny logo in so long. Are people still on it?
Responding to the last comment in the image:
You could literally just do reverse Starship Troopers, the movie at least.
You’re a bunch of aliens and blam out of no where the nuclear launched manhole obliterates a holy site on your homeworld, your scientists track the trajectory back to Earth, conclude they must have launched it intentionally, and then launch an interstellar jihad against totally unaware Earthlings.
That reminds drag of Halo, though significantly more silly.
In Halo, the Covenant are on an interstellar crusade for holy artifacts left behind by the Forerunners. When they discovered the planet Harvest, inhabited by humans, they saw tons of artifacts on their scanners. So naturally, they landed on the planet and started blasting the humans to steal the artifacts. But the more humans they killed, the more artifacts disappeared from their monitors. The humans must be destroying the artifacts out of petty spite! What heresy!
The Prophet of Truth is curious about what kind of artifacts the humans have, so he goes to talk to an ancient Forerunner AI they have in storage, Mendicant Bias. Truth shows Bias the symbol that they keep seeing on human worlds. Bias says “You fool, you’ve got it upside down. Turn it around, see? It says Reclaimer. It means a person the Forerunners have chosen to inherit their empire. You’ve just been killing these humans? No wonder the reclaimers keep disappearing, you’re the one who’s doing it!”
So Truth realises that he’s been ordering his troops to kill what should rightfully be considered demigods by his religion, and who he should be worshipping. And he realises that if he reveals this information to the people, he and the other Prophets will lose all their political power since there are Actual Fucking Gods walking around. So naturally, Truth declares a Holy Genocide against humanity so that nobody will ever figure out that he’s guilty of Deicide and that their entire religious political structure is a lie.
You refer to yourself as “drag” in the third person, rather than just say “me”?
No, drag is using drag’s first person pronoun, drag.
Well that’s a drag.
Drag am using it?
Drag’s pronoun isn’t inflected like that.
Or, you just decided on first contact, but, suddenly, ship goes boom after being struck in the propulsion system with a bullet like manhole cover.
It is of course well known that careless talk costs lives, but the full scale of the problem is not always appreciated.
For instance, at the very moment that Arthur said ”I seem to be having tremendous difficulty with my lifestyle,” a freak wormhole opened up in the fabric of the space-time continuum and carried his words far far back in time across almost infinite reaches of space to a distant Galaxy where strange and warlike beings were poised on the brink of frightful interstellar battle.
The two opposing leaders were meeting for the last time.
A dreadful silence fell across the conference table as the commander of the Vl’hurgs, resplendent in his black jewelled battle shorts, gazed levelly at the G’Gugvuntt leader squatting opposite him in a cloud of green sweet-smelling steam, and, with a million sleek and horribly beweaponed star cruisers poised to unleash electric death at his single word of command, challenged the vile creature to take back what it had said about his mother.
The creature stirred in his sickly broiling vapour, and at that very moment the words I seem to be having tremendous difficulty with my lifestyle drifted across the conference table.
Unfortunately, in the Vl’hurg tongue this was the most dreadful insult imaginable, and there was nothing for it but to wage terrible war for centuries.
Eventually of course, after their Galaxy had been decimated over a few thousand years, it was realized that the whole thing had been a ghastly mistake, and so the two opposing battle fleets settled their few remaining differences in order to launch a joint attack on our own Galaxy – now positively identified as the source of the offending remark.
For thousands more years the mighty ships tore across the empty wastes of space and finally dived screaming on to the first planet they came across – which happened to be the Earth – where due to a terrible miscalculation of scale the entire battle fleet was accidentally swallowed by a small dog.
– Douglas Adams, The Hitchhiker’s Guide To The Galaxy
I love the idea that our first message to aliens might be “FRESH WATER ONLY. NO WASTE.”
So has it been replaced ?
RIP jpgd to death
Slightly less recompressed version: https://imgur.com/2UHiL4r
Definitely easier to read thx
ifunny.c😀
Maybe it desintegrated and thus vanished from the consecutive frame?
Atomic blasts are kind of powerful versus an iron lid.
What are the chances it was blasted into the sun?
If the event was near the equatorial near midday then there’s a very very (very) slim chance it was pointed directly at the sun.
If it was pointed directly at the sun, it would miss. Not that this would make the odds any better, but aiming straight at the sun doesn’t work either.
Saying this with only an understanding of orbital mechanics learned from Kerbal Space Program, I’d say the chances are damn near 0%. Hitting the sun is actually pretty difficult and requires a precise amount of Δv (change in velocity). This thing had such a huge Δv that it would have left the solar system.
Sadly, the cover likely did burn up in the atmosphere at those speeds, like a meteorite in reverse.
And for reference, the earth escape velocity from the surface is 11.2 km/s or 25,000 mph, not 7,000 mph.
To escape the solar system from the earth surface, the minimum speed is 16.6 km/s, or 37,100 mph. But this assumes that you launch in the correct direction to take the most advantage of the Earth’s 30 km/s. If you launch in the most disadvantageous direction, you can add another 60 km/s to escape.
So sad about what happened to planet Kerbin.
I’m not so sure.
Let’s compare with the Apollo Command Module heat shield, a remarkably close analogue for the bore cap. They’re a similar weight (3,000 lb for the heat shield, 2,000 lb for the bore cap) and have melting points within an order of magnitude of each other (5,000°F for the AVCOAT heat shield and about 2,800°F for the iron bore cap). They’re even both of a similar shape and aerodynamic profile (disc-shaped and blunt). Both had to travel 62 miles (the distance from sea level to the Karman Line, where atmosphere becomes negligible).
The Apollo CM made that distance in about seven minutes; at 130,000mph, the Pascal B bore cap took at most 1.72 seconds to make the trip.
What was discovered during the development of the Apollo heat shield is that the blunt shape caused a layer of air to build up in front of the spacecraft, which reduced the amount of heating that convected into the heat shield directly. This reduced the amount of heat load that the heat shield needed to bear up under.
Further, it’s also worth noting that the Apollo command modules weren’t tumbling, which the bore cap likely would have been, allowing brief instants during its ascent for the metal to cool before being subjected again to the heat of the ascent.
But probably most critical at all is the remarkably brief amount of time that the bore cap spent in atmosphere. This person did the math on how much power it would take to vaporize a cubic meter of iron, and the answer is 25,895,319 kJ. Now, the bore cap isn’t quite a cubic meter, but we can use all of his calculations and just swap in 907kg (2000lbs):
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To heat the bore cap to iron’s melting point: 0.46 kJ/kg * 907 kg * (1808K-298K) = 630,002 kJ
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To phase change the iron from solid to liquid: 69.1 KJ/kg * 907 kg = 62,674 kJ
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To heat the bore cap to iron’s boiling point: 0.82 kJ/kg * 907 kg * (3023K-1808K) = 903,644 kJ
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To phase change the iron from liquid to gas: 1520 kJ/kg * 907 kg = 1,378,649 kJ
So, in total, 2,974,969 kJ. The Apollo heat shield encountered a peak of 11,000 kJ/m^2/s. Since the Pascal B bore cap was about a meter in diameter and was traveling through the atmosphere for about two seconds, we can very neatly estimate that it absorbed a maximum of 22,000 kJ due to atmospheric compression–not even close to enough to get it to melting temperature.
Interestingly, early missiles actually did use solid metal heat shields; not iron, but titanium, beryllium, and copper. They were effective, but abandoned due to their weight.
I don’t think you can compare the Apollo heat shields to a bore cap being launched into space. For one thing, the Apollo shield started in the very thin upper atmosphere, and they came in at an angle that meant they bled off as much speed/energy as possible in that thin upper atmosphere before going into the thicker atmosphere. In fact, one of the engineers said that if they came in too steep they’d generate too much heat and probably not survive the re-entry.
The layer of air you’re talking about at the front of the spacecraft was what heated up the heat shield. Instead of causing heating via friction, the heat was the result of compressing the air. The amount of compression you’re talking about would be orders of magnitude higher for something starting at 40 km/s in the thick lower atmosphere.
Also, the Apollo heat shield did heat up to 5000F or 2800C but was designed to be ablative, so that the hot layers burned off and flew off to the sides leaving new material to be heated up and burned off. This concrete and metal plug wouldn’t have been designed the same way. Concrete apparently melts at 1200C, and steel is approximately the same, so it’s very likely some of it melted or vaporized, the question is how much.
I don’t know where you’re getting the maximum of 22MJ of energy. The whole point of Apollo not going directly into the atmosphere was to take as long as possible to slow down, going through the thinnest part of the atmosphere for as long as possible. The whole point would be to reduce their energy-per-second as low as possible by taking as many seconds as possible. One reasonable first approximation of the energy would be to integrate the entire energy per second / power for Apollo’s re-entry over the entire 7 minutes (or however long it took until parachutes deployed) and then divide that energy by 2 for the 2 seconds the plug was in the atmosphere.
My guess is that that would have been temperatures well in excess of 1200C which would have made the outer surface start to melt, and most likely a temperature where it just turns to plasma. Would it all have melted / vaporized / plasmafied away? I don’t know, it’s a huge plug. Since it was launched vertically, anything remaining would probably have come right back down. But, that’s assuming it stayed in one piece. I’m guessing it broke apart due to the stresses on it, and breaking apart would have meant more surface area, which would have meant more areas exposed to massive heating, which would have meant more breaking apart.
TL;DR: I doubt it made it out of the atmosphere.
For one thing, the Apollo shield started in the very thin upper atmosphere, and they came in at an angle that meant they bled off as much speed/energy as possible in that thin upper atmosphere before going into the thicker atmosphere.
I don’t know that that makes a huge difference to the physics involved, though it certainly may have.
In fact, one of the engineers said that if they came in too steep they’d generate too much heat and probably not survive the re-entry.
But in that case we’re talking about human survivability, and a chunk of solid iron is going to survive a whole lot longer than humans or delicate instrumentation. It might look a little worse for the wear, but it’s much more likely to be recognizable after the whole experience than anything designed for people.
The layer of air you’re talking about at the front of the spacecraft was what heated up the heat shield. Instead of causing heating via friction, the heat was the result of compressing the air.
But after initial heating, the air cushion begins heating itself up instead of the object, reducing the amount of heat the object receives.
The amount of compression you’re talking about would be orders of magnitude higher for something starting at 40 km/s in the thick lower atmosphere.
But it would also tail off as the bore cap heated, reducing stresses on it as it went higher.
Also, the Apollo heat shield did heat up to 5000F or 2800C but was designed to be ablative, so that the hot layers burned off and flew off to the sides leaving new material to be heated up and burned off.
True, but on the other hand the a Apollo heat shield wasn’t designed to convect heat to other parts of itself. And again, it had a much harder job (keep the Apollo command module at human-survivable temperatures) than the bore cap (not reach the boiling point of iron).
This concrete and metal plug wouldn’t have been designed the same way. Concrete apparently melts at 1200C, and steel is approximately the same, so it’s very likely some of it melted or vaporized, the question is how much.
All the stuff I read only mentioned the iron, but keep in mind that it has to not only reach the melting point but also undergo phase change, which requires a lot more energy.
I don’t know where you’re getting the maximum of 22MJ of energy.
11 kJ per m² per second was the peak amount of energy that the Apollo heat shield encountered. Double that for the approximately two seconds it would’ve been in atmosphere, and it’s a pretty handy approximation since the bore cap was about a meter itself.
The whole point of Apollo not going directly into the atmosphere was to take as long as possible to slow down, going through the thinnest part of the atmosphere for as long as possible. […] One reasonable first approximation of the energy would be to integrate the entire energy per second / power for Apollo’s re-entry over the entire 7 minutes (or however long it took until parachutes deployed) and then divide that energy by 2 for the 2 seconds the plug was in the atmosphere.
You’re right, the total amount would’ve been a way better approximation than the peak. Worth looking into.
My guess is that that would have been temperatures well in excess of 1200C which would have made the outer surface start to melt, and most likely a temperature where it just turns to plasma.
I don’t have any argument with that. I think the outer surface would definitely have begun to melt.
Would it all have melted / vaporized / plasmafied away? I don’t know, it’s a huge plug.
Yep. Even just considering the amount of time it would take for the heat to excite all the molecules in the massive chunk of iron, and then for them all to undergo phase change, I just don’t think it could’ve made it.
Since it was launched vertically, anything remaining would probably have come right back down. But, that’s assuming it stayed in one piece. I’m guessing it broke apart due to the stresses on it, and breaking apart would have meant more surface area, which would have meant more areas exposed to massive heating, which would have meant more breaking apart.
That’s something I couldn’t find information on: is iron’s tensile strength high enough to prevent the thing shattering apart on contact with air? I’m inclined to think it is—chunks of meteorites bigger than a meter have made it through the atmosphere, for instance. The Hoba meteorite is estimated to only be slightly bigger than it is now before its atmospheric entry, and it’s way bigger than the bore cap. Similar composition, too.
TL;DR: I doubt it made it out of the atmosphere.
Either way, I like researching it.
Edit: also, the bore cap starting at the bottom of the atmosphere means that it’s likely it experienced less fracture stress, since the air would’ve accelerated with it rather than being static.
For one thing, the Apollo shield started in the very thin upper atmosphere, and they came in at an angle that meant they bled off as much speed/energy as possible in that thin upper atmosphere before going into the thicker atmosphere.
I don’t know that that makes a huge difference to the physics involved, though it certainly may have.
Of course it will make a difference. The whole challenge is about managing the heat build-up, which is the energy per second (i.e. power). If you hit the thin upper atmosphere you’re encountering less material, so less friction / pressure, so less heating. It means you can keep the heat on the heat shield in a manageable range, rather than putting it at a temperature where it would melt or explode.
the air cushion begins heating itself up instead of the object, reducing the amount of heat the object receives.
No, both heat up. The air cushion transfers its heat to the object next to it. At the kinds of pressures we’re talking about, you might even be getting nitrogen plasma rather than just nitrogen gas.
But it would also tail off as the bore cap heated, reducing stresses on it as it went higher.
If it went high enough for that to matter. If it disintegrated in the lower atmosphere it wouldn’t matter that the air got thinner in the upper atmosphere.
chunks of meteorites bigger than a meter have made it through the atmosphere, for instance
Is a metre the original size, or the final size? Also, reverse meteors (something starting with its maximum speed in the lower atmosphere) are doing things the hard way. Rather than getting slowed down initially by the thin upper atmosphere and then only hitting the thick atmosphere once they’re slower, they start out in the thickest atmosphere. OTOH, a meteor is a random collection of rock and metal formed by gravity in space. A pure metal plug cast on Earth is probably going to be a lot less prone to breaking apart.
the bore cap starting at the bottom of the atmosphere means that it’s likely it experienced less fracture stress, since the air would’ve accelerated with it rather than being static.
That doesn’t make sense to me. Something in a thicker medium is going to experience more stress. Try pushing a cracker through the air vs. through water vs. through gelatin. Which medium will cause the cracker to crack first? Obviously it’s the thicker medium.
Most of this is going to be “eh, agree to disagree” because we just don’t have enough data. But I do want to call out a couple of things:
No, both heat up. The air cushion transfers its heat to the object next to it.
Over time, yes. But the bore cap doesn’t have very much of it. Heat transfer is not instantaneous; would it be long enough for the air to transfer its heat to the object, before the object reaches the Karman Line? Radiation is pretty quick (like, speed-of-light quick), but conduction is much slower; particularly when one of the bodies (the air) is an insulator. And with iron being an excellent conductor, any heat transferred will be spread throughout the body more quickly than it can be absorbed.
If it disintegrated in the lower atmosphere it wouldn’t matter that the air got thinner in the upper atmosphere.
True, but it’s not like there’s a line (er, well, I mean, not a physical demarcation…there is the Karman Line, but…ah, you know what I mean). Atmospheric density is a decreasing gradient from the ground to the Karman Line. So as it approaches its mechanical and physical limits, the amount of energy acting upon it decreases millisecond by millisecond. Is that enough to save it? Shrug. Not enough data. But it’s possible.
Is a metre the original size, or the final size? [of the meteorite chunk]
Actually it’s almost three meters, and as far as we can guess that was about its original size. Though in fairness, it was entering the atmosphere at a steeper angle and may even have come down entirely in “dark flight.” Still, there are other large meteorites which have impacted at a size greater than 1 meter across, though obviously we have no way to confirm exactly how big they were before they landed.
Rather than getting slowed down initially by the thin upper atmosphere and then only hitting the thick atmosphere once they’re slower, they start out in the thickest atmosphere. […] Something in a thicker medium is going to experience more stress. Try pushing a cracker through the air vs. through water vs. through gelatin. Which medium will cause the cracker to crack first? Obviously it’s the thicker medium.
True! But remember, the “reverse meteor” (great phrase, btw) is not hitting the stationary atmosphere at full speed like a regular meteor (or space capsule) does. The iron plug accelerated (incredibly quickly, but it did accelerate) while already in contact with the air above it. This means that the air accelerated at the same rate the iron did, reducing the fracture forces that would seek to crack it. Imagine the difference between swishing your hand in a swimming pool vs. slapping the surface of a swimming pool; it may require more force, but it won’t hurt as badly.
OTOH, a meteor is a random collection of rock and metal formed by gravity in space. A pure metal plug cast on Earth is probably going to be a lot less prone to breaking apart.
Oh, great point, and one I hadn’t thought about. Something that’s an aggregate of 80% iron and 20% “other stuff” isn’t going to have nearly as much tensile strength as a homogeneous plate of iron.
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I’m not so sure… At those speeds, it would’ve taken under 10 seconds to completely clear the atmosphere. Even with intense compressional heating, I don’t think it would’ve been in contact with the atmosphere long enough to completely vaporize — although it probably didn’t look much like a manhole cover anymore by the time it escaped.
It was being propelled by a nuclear blast. The speed was calculated from 1 frame of a high speed camera. It most definitely vaporized.
I don’t think melting is the issue here. I think it literally disintegrates at those speeds. Like, this is Mass Effect mass driver level of impact with the atmosphere.
For reference, RICK ROBINSON’S FIRST LAW OF SPACE COMBAT: “An object impacting at 3 km/sec delivers kinetic energy equal to its mass in TNT.”
Assuming the lid is travelling 55km/s, it’s well beyond that point. The atmosphere it’s travelling through is basically a solid at that speed. Even if it isn’t heating due to the friction (and waiting for heat flow), it is heating due to the compressive force of being slammed into the atmosphere. It’s very likely the whole thing vaporized.
But I could be wrong, and some alien SOB is going to have a bad day when the manhole cover slams into their ship in interstellar space.
The atmosphere is just about 10 kg/m^2 in sectional density; the manhole cover was very likely higher than that, wouldn’t that mean the cover’s mass should have come out at the other side, intact or not?
Would vaporization slow the material though? Perhaps the end result wasn’t a manhole escaping the solar system but a huge collection of microscopic metal fragments scattershot that direction. Which really makes the Mass Effect quote even more relevant to a huge amount of aliens somewhere.
Vaporization would certainly slow the material. It’s transitioning kinetic energy into thermal.
Also, the vaporized iron would disperse outward rather than stay coherent.
It would spread outward a bit, but the entire kinetic energy and momentum in the system would remain the same. But, the more it broke apart, the more surface area it would have. The more surface area, the more surface exposed to heating. The more heating, the more it would break apart. I’m guessing that it was a silicon, iron and oxygen plasma without individual grains by the time it hit the upper atmosphere.
Yes, it absolutely would have vaporized before exiting the atmosphere.
Here’s a video on the subject: https://www.youtube.com/watch?v=mntddpL8eKE
How to solve the Three Body Problem.
In Stargate SG1 they do that to destroy and invading alien ship approaching Earth.
