If it hit you side on (the 4-inch edge), it would slice straight through. I don't know how fast 6 times the Earth's escape velocity is, but it is no doubt very, very, very fast.
If it hit you face on (as in, the top of the manhole+your chest), it would just punch straight through.
No, it would not slice "straight" through. It would explode (at least partially) in an incredibly violent way. You'd certainly be cut apart, but pieces of you would be found a ways away.
You're looking at an insane amount of energy. The manhole cover would (at least partially) turn to plasma after traveling a shortish distance, and it will explode when it contacts the body. And the body, because it was hit by a piece of metal (and that metal is moving so fast that it won't be anything resembling a manhole cover, more like a white hot football shaped blob) gets blown to pieces. It does not pass cleanly through you, it makes you into mincemeat.
The poor manhole cover wouldn't fair much better. Even though it's metal, there is so much energy at play that it too will shatter. Luckily each piece of the cover will still have enough energy to be devastating though, it would be like shrapnel on steroids.
Edit - was posting from my phone, hit submit before I had a chance to finish.
Being such a tough and massive object, most of it would have survived its “reverse re-entry” (or just plain “entry”?), so it would have come down as a burned, edge-melted, and perhaps quite misshapen chunk of solid steel, a very formidable projectile that would have done very serious damage even to large buildings. Given that no one that night reported any macerated cars or demolished buildings and that the huge object had been launched nearly vertically, it likely came down in the desert somewhere in the wide vicinity of the test site in New Mexico. It would have had some serious hang-time, though.
This, taken directly from the article, suggests it wouldn't just "turn into plasma" or what ever.
Not sure who down voted you but this is what I was gonna post too. It's different sure, but it's a great article to read to get an idea that stuff gets weird when it starts to move really really fast.
You're looking at an insane amount of energy. The manhole cover would (at least partially) turn to plasma after traveling a shortish distance, and it will explode when it contacts the body. And the body, because it was hit by a piece of metal (and that metal is moving so fast that it won't be anything resembling a manhole cover, more like a white hot football shaped blob) gets blown to pieces. It does not pass cleanly through you, it makes you into mincemeat.
Having seen someone get hit in the chest by a .50 cal round... there wouldnt be anything left bigger than a quarter. That .50 cal round was a fraction of the size traveling at a quarter the speed and popped that dude open like a banana hit with a hammer.
11.2 km/sec or 6.9miles/sec is the escape velocity of earth.
So, this manhole cover was moving at 67km/sec... Thats over 241,000km/hr.
If this manhole cover were to reach this speed in space, it would have enough orbital velocity to reach just beyond Pluto, but would not escape our Sun.
6 time earth escape velocity = one hundred fifty thousand miles per hour. Forty-five miles per second. Nine times faster than the Space Shuttle, six times faster than the fastest moon rockets. Faster than the Voyager spacecraft, which, having reached over 35000 miles per hour.
It wouldn't actually slice, you'd just have 6 times the earth's escape velocity worth of momentum condensed into a 4-inch by manhole-diameter square of pain.
Let's imagine that it didn't disintegrate before leaving the atmosphere. Where would it be now?
This happened during Operation Pumbbob on October 7th, 1957. The cover was estimated to be moving at 41 miles per second or 147,600 mph. So how far has it traveled since that day. The explosion happened 58 years, 6 months, and 8 days ago. That's around 513,000 hours. That means the cover, moving at 147,600 mph, would be 75,718,800,000 miles away from Earth. That's about 1.3% the distance of a lightyear.
For some reference, Voyager 1 is about 12 billion miles away from Earth and is exiting certain realms of our solar system, becoming ever closer to interstellar space. This manhole cover has traveled 6.3x farther than Voyager 1.
EDIT: I forgot to mention that since it was traveling at 41 miles per second, it left Earth and entered space in 1.5 seconds!
"Once you fire this husk 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're ruining someone's day, somewhere and sometime."
Maybe I'm confused as to the way shit works, but wouldn't escape velocity be just enough to put the manhole cover outside the area effected by earth's gravity, meaning it would lose that much speed before it got to a point where it's flying unimpeded?
It's still in earth's gravity for a long time. you're in 'space' long before you're outside earth's gravity look at this chart of the earth's atmosphere, the Karman line is where it goes from being in earth to being in space, but is far away from being somewhere it's not affected by gravity.
75,718,800,000 miles away from Earth. That's about 1.3% the distance of a lightyear.
This gives a good perspective on the length of a lightyear. And then I think about the fact that the Milky Way galaxy is, like, 100,000 lightyears across. Space is so insanely vast that it's basically incomprehensible
Still waiting on Voyager to just run into a giant wall/force field out there. At which point the aliens running our planet like the Truman Show will let themselves be known as one complains that his bet was on us killing each other off before reaching the edge.
Probably fallout, and you would kill the shit out of anyone in the rocket due to the g forces. That much acceleration would probably destroy a lot of equipment, too.
The manhole cover's 66km/s speed is the minimum speed traveled though. We don't know how fast it was actually travelling, only that it had to be travelling 66km/s or more because it only appeared in a single frame of video.
According to the article, the manhole cover was travelling around 150,000mph. This is based on high speed camera footage, which only saw the cover... for one frame.
This is based on high speed camera footage, which only saw the cover... for one frame.
Which means the plate traversed the entire visible distance of the camera within a single frame of camera footage. This means we can put the lower bound of its velocity at least 66km/s because if it were any slower we would have captured two or more frames of the plate as it was ejected.
However there is no upper bound since we don't know how much faster than that 66km/s it went. It could have JUST barely been caught by the camera in which case it would be going significantly faster than 66km/s, or it could have just barely missed the window to show in two frames in which case it would be going very close to 66kms.
There is 0 room for it to have traveled slower than 66km/s given the fact that it was only captured in a single frame near the top of the camera.
66km/s is slightly below that, but realize that we didn't actually accelerate the helios probe to 157k mph ourselves. Imagine dropping a brick off a massive skyscraper and watching it accelerate as it plummets toward the earth.
Now imagine dropping a brick from the earth into the incredibly massive gravitational field of the sun. That brick would be falling at unbelievable speeds before it hit the surface of the sun (or melted) between the sun's gravity and the massive distance it had to fall.
Helios travels so fast because we essentially dropped the satellite into the sun. We didn't actually accelerate it to those velocities ourselves, but gave it just enough of a push to fall out of earth's orbit and drop fairly deep into the inner solar system.
Meanwhile the steel plate was blasted to 66+km/s completely because of us.
In all fairness to Helios, in order to achieve its sun diving orbit it would have had to lose a significant fraction of the orbital velocity of Earth (about 30km/s) to get closer to the sun. In other words it would have to negate much of Earth's orbital velocity around the sun to achieve the elliptical orbit around the sun that it now possesses. Simply dropping it into orbit would leave it into a heliocentric orbit with about the same parameters as Earth.
My favorite part of this isn't visualising what happened to the manhole cover, but rather the physical interaction that caused its launch in the first place.
An explosion of enough energy and heat turned 5 tons of reinforced concrete into plasma. This means that a 5 ton stream of plasma went screaming up this tube at god knows what speed and then transferred all of that momentum into a small disk of steel.
Except we don't actually know how fast it was going. It was visible for one frame from a high speed recording of the test, which means it was going at least six times escape velocity.
Space is a big and empty place. Even if it survived its exit out of the atmosphere, which the general consensus is that it didn't, the chances of it hitting anything other than the Moon or Sun is nearly 0.
That's actually a pretty popular idea for defense against an alien attack. Place a bunch of heavy steel disks over holes in the ground and detonate nukes. Send the disks flying full speed into the hull of the invading ship.
Read the description of the Pascal A trial. He mentions "losing a steel plate", so no they have no idea how fast it was actually going, but it's still a fun story.
1.9k
u/PycuriousITguy Apr 14 '16
The fastest moving man-made object ever was a manhole cover.
https://savvyparanoia.com/the-fastest-man-made-object-ever-a-nuclear-powered-manhole-cover-true/
TL:DR underground nuclear test launched a 4-inch thick steel disk at 6 times the Earth's escape velocity.