Ballistics - get someone talking about bullets and before you know it it's gotten all "hollow-point" this and "deforming-round" that.
Sometimes a bullet can go right through someone and out the other side, without too much disruption. This requires that the bullet is sharp, and that its tip isn't deformed on impact. If both these requirements are met, the entry and exit wounds on such an encounter can be surprisingly small.
What if it were the same with asteroids?
All you'd need to do would be to lengthen the asteroid along its axis of travel (assuming this axis is the one that will eventually pass through the earth) and apply enough heat to shape the asteroid into a long, thin, sharply tapered form, perhaps applying a shiny teflon coating to the front (if only to make it look good)
Thus, when the asteroid impacts, rather than mushrooming out into a wide area and delivering all of its energy onto the surface and into the atmosphere, it might instead slip beneath the crust and either come to a stop safely below ground, or maybe, zip out the other side, no (or at least relatively less) harm done. Less damage, at least, than a cataclysmic plasma-ball followed by a millenium-long perpetual darkness type scenario.
Obviously, it's preferrable to avoid being hit by an asteroid in the first place - but if it absolutely can't be avoided, then maybe reprofiling the impacting body in order to minimise the effects might be a preferable (and in contrast, more practical) solution.-- zen_tom, Mar 01 2012 http://newyork.ibti...lsar-star-earth.htm [2 fries shy of a happy meal, Mar 01 2012] Federal .22lr Specifications http://www.discount...&utm_campaign=36452This isn't the fastest .22 out there. In fact it one of the slower ones, but it's the brand I buy so I went with it, and the delicious "crack" that it emitts upon being fired let's me know it's super-sonic [MikeD, Mar 04 2012] 540grns @ 1550 ft/sec http://www.garrettc...idges.com/4570.htmlBroad Meplat Bullets (Very not pointy) [MikeD, Mar 04 2012] Brilliant! And as a bonus, a massive hole through the Earth will be a boon to the mining industry.-- hippo, Mar 01 2012 Spacelathe!-- calum, Mar 01 2012 Ha - I love the spacelathe take - which could be employed when mining asteroids for their mineral wealth, the leftover husks being shaped like great cosmic balusters.-- zen_tom, Mar 01 2012 What about making them boomerang-shaped?-- nineteenthly, Mar 01 2012 Why not make the Earth into a doughnut shape instead? The advantage is that the work can be done here, instead of out in space.-- pocmloc, Mar 01 2012 // Less damage, at least, than a cataclysmic plasma- ball// now there's a statement.-- MaxwellBuchanan, Mar 01 2012 [19thly] I'm not sure I see how that would help - boomerangs tend to impart their energy very much through a kind of clobbering action, which is almost precisely the type of thing we want to avoid here.
If we are choosing to look at this from the vantage point of analogous aboriginal weapons, we probably want to preferentailly consider the pointy ones, rather than spend too much time considering options at the more clubby end of the spectrum.
[pocmloc] a capital suggestion - by changing the Earth into a torus, we make the planet "asteroid agnostic" and can get on with worrying about more pressing problems.
[MaxwelBuke] quite right - in fact, with careful planning and some minor nudges one way or the other, the entry/exit points might be so adjusted to limit the damage to some area of little note or value, like Basingstoke or Croydon, for example.-- zen_tom, Mar 01 2012 [+]... sufficient mass and careful trajectory and we can get other planets too... solar kebab.-- FlyingToaster, Mar 01 2012 My concern is that if the tip were not sufficiently sharp, the asteroid would be repurposed into a cue, wielded by the great cosmic Higgins.
[EDIT: looks like I am copying the great cosmic [zen_tom]]-- calum, Mar 01 2012 "I read of one planet off in the seventh dimension that got used as a ball in a game of intergalactic bar billiards. Got potted straight into a black hole. Killed ten billion people." "That's mad." "Yes, only scored thirty points too."-- hippo, Mar 01 2012 I think that [nineteenthly] makes a good point. Boomerangs return to where they came from, thereby saving the earth.-- normzone, Mar 01 2012 //Boomerangs return to where they came from, thereby saving the earth //
But they work on aerodynamics. A boomerang- shaped asteroid would change direction about as much as a boomerang thrown by me does.-- theleopard, Mar 01 2012 // get someone talking about bullets //
Really?! Are you seriously giving me leave to talk about bullets?
// Sometimes a bullet can go right through someone and out the other side //
It's called blow-through, and it's why cops shouldn't carry 9mm sidearms.
// This requires that the bullet is sharp //
No, it doesn't. The 9mm PB is a handgun round that is notorious for blow-through, and it's about as sharp as the end of your pinky finger.
// without too much disruption //
Nuh-uh, sorry. Any bullet fired from a rifled barrel that has sufficient energy to penetrate and exit the target, even a full-metal-jacket (or 'ball') round, will leave a wound cavity significantly larger than the bullet's diameter due to the hyperbaric shockwave it generates as kinetic energy is transferred from the hard bullet into the much softer flesh around it. The only reason hollow-points and similar deforming or frangible bullets (potentially) do more damage is because they transfer _all_ of their energy into the surrounding flesh rather than retaining enough to exit the body.
// the entry and exit wounds on such an encounter can be surprisingly small. //
Yes, but due to properties mentioned above, the bullet will spin and tumble on an erratic course through the body, leaving huge cavities and, due to the force of its passage, severly damaging flesh and organs that it never even touches. The .223 (5.56 mm NATO) round, which is used in the M-16 assault rifle and variants thereof, was intentionally designed to tumble inside the body in order to cause horrific wounds instead of outright fatalities (in war, a wounded soldier is a far greater drain on resources than a dead one). There are documented cases of single .50-caliber bullets (1/2" diameter, or 12.7mm) completely severing limbs from the body, causing partial decapitations, and wreaking similar carnage that to the layman might seem disproportionate to the size of the bullet itself. Even .30-cal (7.62mm) bullets have been known to leave exit wounds the size of a grapefruit. Incidentally, all of the bullet types discussed in this paragraph have sharp points.
The magnitude of damage done by a bullet is not determined solely by its shape or expansive properties, but also by its velocity, balance, material composition, and rate of spin imparted by the rifled barrel. How all this applies to a bullet-shaped asteroid striking the Earth at a precisely calculated trajectory I don't know, but I doubt it would leave a 'clean' wound. My gut tells me that it might do _more_ damage, as it would be aerodynamic and thus would lose less energy to atmospheric resistance, and that the deeper penetration and resulting hyperbaric shockwave below the Earth's crust would cause more widespread seismic disturbance than an un-modified asteroid of equivalent mass impacting on the surface. All of that, however, is layman's conjecture.-- Alterother, Mar 01 2012 Which suggests to me that what we want to do is band the earth in such a way that bulletised asteroid #1 will create by impact and exit the toroid earth, leaving subsequent asteroids with a less hittable target.
A question: is the tumbling, expanding and damaging of the bullets to an appreciable extent a result of them being metal. If so, do these objections fly off if we assume the asteroid is made of diamond and is sharpened to an atomically perfect point?-- calum, Mar 01 2012 The tumbling has more to due with the shape and the balance of the bullet, so no, it's not important the bullet be made of metal, only that it be composed of two or more workable materials of different densities. The reason metal is used is because everything else tends to either shatter or splatter when it impacts the target.
Expanding bullets, i.e. hollow-points, also rely on the shape of the bullet, but must be made of something very ductile and yet adherent to its form, like lead. Frangible rounds are made with engineered weak points that cause them to fragment after penetration.
Whether or not a bullet is pointed has little to do with its penetrative qualities (except in the case of special ammunition such as armor-piercing bullets). Most rifle calibers and a handful and hangun calibers are made with pointed tips because they travel at very high velocities and therefore have delicate aerodynamic tolerances... or that's the simple answer, at least.
As for the last bit about a perfectly honed solid diamond asteroid/bullet, I can only speculate, but my speculation would begin with this: diamonds are brittle. You can smash one with a hammer. A bullet made of diamond would probably be dust before it left the barrel of the gun. If somehow this could be prevented, yeah, it could go zipping right through a soft target, but would likely be pulverized when it hit anything harder than wood.-- Alterother, Mar 01 2012 Damn it!That's the basic premise of the great Canadian novel I haven't gotten around to finding time to finish yet.
Early in the formation of the solar system the Earth was peppered by very large diamond fragments. [link]Because of their composition and shape the fragments left very small impact craters but penetrated almost to the core of the planet itself.The shock waves from the massive release of subteranean heat and gas created masive caverns on both sides of the core which solidified as the core reformed.
Connected by submerged fissures and magma-tubes the caverns on the impact side of the planet gradually wear away and expose the diamond fragments allowing light to penetrate deeply enough so that parallel evolution on an entirely alien scale happens below the surface.
muhahaha-- 2 fries shy of a happy meal, Mar 01 2012 Apparently, the 'Hollow Earth' mythos has yet to hit Canada...-- Alterother, Mar 01 2012 With bullets, doesn't it basically go pointed tip <-> supersonic, rounded tip <-> subsonic?
//... sufficient mass and careful trajectory and we can get other planets too...// So fashion the meteor into a needle, and sew several planets together.-- spidermother, Mar 01 2012 //supersonic... subsonic// rifle-bullets start off supersonic, pistols' usually subsonic; both trying to avoid passing through the transonic zone in flight and messing up accuracy. But there's rounded rifle shells: granted I think the newer designs are all pointy.-- FlyingToaster, Mar 01 2012 Rounded bullets... has anyone made a Reuleaux bullet, in an attempt to leave a square exit wound?-- mitxela, Mar 01 2012 //there's rounded rifle shells// The only rounded rifle rounds I've seen are definitely subsonic.-- spidermother, Mar 01 2012 .45-70, .50-90 Sharps, 6.5mm M-S, .30-30 Winchester, .30 Carbine... to name a few: all round tipped, very supersonic rounds. What rifle ammunition is subsonic ? barring some, but not all, rimfire rounds... and not including pistol ammunition fired from a rifle.-- FlyingToaster, Mar 02 2012 I'm bunning the idea for creativity and for what would be a good idea if it were workable.
I don't think pointing an asteroid is possible or practical, but the thought of spreading the impact forces down into the deeper parts of the Earth is certainly interesting.
I think it would be a good thing over all, but if it worked just wrong, you'd get an instant volcano.-- baconbrain, Mar 02 2012 (Disclaimer: I know very little about guns) I'm fairly sure the common .22 caliber ammunition typically used in Australia for rabbits etc. is subsonic; it's certainly very low powered.
(Further reading suggests that they are .22 short rounds, which are in fact primarily pistol rounds; but used in rifles, and definitely subsonic.)-- spidermother, Mar 02 2012 ah, ya got me: most .22 calibre "Long Rifle" rimfire (most common ammunition in the world) cartridges are subsonic... but pretty well everything else leaves the barrel at far past Mach 1 or even 2, pointy or round-nosed.
(.17 rimfire which is "the new .22lr", is pointy)-- FlyingToaster, Mar 02 2012 Except for the boomerang shaped ones - while even slower, they are used primarily by reloaders who desire optimal economy and re-use everything except the bang.-- normzone, Mar 02 2012 Almost all handgun and rifle calibers have supersonic muzzle velocities. Special subsonic rounds are sold on the specialty market.
Here is reduction of my somewhat limited knowledge on the round vs. taper issue:
The tip shape of a bullet is usually designed with a purpose in mind, but in general, rounded bullets are slower and used over shorter ranges. That's a very, very general statement. Also, some older rifle calibers such as .22 long, .45-70, .50-90 Sharps, and .30-30 Winchester are round because, well, you don't fix what ain't broke. Though 'smaller' than rounded .22s, .17 HMRs are pointed because the cartridge contains the same amount of propellant, thus the lighter bullet goes like a bat outta hell.-- Alterother, Mar 02 2012 <LouCostello> Sooo ... let me get this straight: Sharps are round? </LouCostello>-- mouseposture, Mar 02 2012 No, Sharps' are blunt, but lots of rounds are sharp.-- Alterother, Mar 02 2012 Sharps, and thutty-thuttys, an' them .45-70 Guvvermints was put in tube-fed guns, an' they's mo bad juju in puttin' a pointy bullet in a tube fed. 'Cept iff'n its a rim-fire.-- lurch, Mar 02 2012 A good example of the tip design being influenced by a specific purpose. I admit that I copied those from a previous anno because they also fit my point that the munitions industry rarely changes things that work well, preferring to offer improvements as paralell products rather than replacements. It was easier than pulling a few different ones off the top of my head. I suppose another example would be the .500 Jeffery, which is round-tipped because it is a gigantic low-velocity round designed to take down huge African mammals at medium ranges. It, too, fits as an example of an old cartridge that meets its purpose and needs no improvement.-- Alterother, Mar 02 2012 Alternatively, we could lower the probability of an asteroid hitting Earth, by creating a large number of duplicate Earths (to save costs, these might be holograms). If there were, say, nine of these (which would make the night sky look lovely) then only 10% of the time an asteroid hits Earth would it hit 'our' Earth.-- hippo, Mar 03 2012 bit of an inconvenience to the hologram people though.-- FlyingToaster, Mar 03 2012 Equally logically, we deliberately slam an asteroid into the Earth, on the grounds that the chances of being struck twice are infinitessimal.-- spidermother, Mar 03 2012 No, that's silly, as you well know. We should deliberately *repeatedly* slam asteroids into the Earth on the grounds that it feels so good when it stops.-- mouseposture, Mar 03 2012 Apply directly to the mantle.-- theircompetitor, Mar 03 2012 // Equally logically, we deliberately slam an asteroid into the Earth, on the grounds that the chances of being struck twice are infinitessimal. //
Which is the same logic I apply to confound well-meaning but obtuse members of my community when they say things like "so, you won't be riding any more motorcycles, now, will you?"-- Alterother, Mar 03 2012 Why? Because riding a motorcycle slams you repeatedly into the earth?-- pocmloc, Mar 03 2012 No, because people think they're doing me a favor by clumsily hinting that I shouldn't ride again because I was injured in an accident, and I respond to that by, while keeping a perfectly straight face, asking them what they think the chances are of me hitting the same deer twice (the odds are approximatly 0:0, because the deer was killed).
But we were talking about asteroids. Or bullets. Or was it diamonds? I've forgotten now...-- Alterother, Mar 03 2012 Is it impossible to hit a dead deer?-- pocmloc, Mar 03 2012 No, but it's easier to miss one.-- Alterother, Mar 03 2012 If [8th_of_7] get ahold of the carcass, we may find out if that's true.-- mouseposture, Mar 03 2012 Funny you should mention that; BorgCo R&D and the Heathen Institute for Inadvisably Applied Science and Rhinoceros Husbandry are currently conducting a joint study on asteroid deflection/redirection, using the carcasses of freshly slaughtered Blink Deer* as stand-ins for the asteroids.
*be assured that no innocent, non-teleporting deer are being harmed in this or any other study that we know of.-- Alterother, Mar 03 2012 Not stand ins....I believe they are being fired at the asteroids to deflect them, on the basis that they couldn't miss.-- Ling, Mar 04 2012 You could paint a big dartboard on the ground, and make an international competition. Make money from selling the tv rights.-- not_morrison_rm, Mar 04 2012 I'm pretty sure .22 LR is super-sonic. And many big-game rounds are very, very unpointy and very, very ubersonic.
Check out Broad Meplat Bullets in the nitro-express variety.
[back from i-net search]
Yup, speed of sound @ 20 degrees Celsius = 1126 ft/sec speed of sound @ 40 degrees Celsius = 1163 ft/sec speed of .22lr 1200 - 1250 ft/sec
I was going to mention the 9mm parabellum (also supersonic, which I just found out is named after the latin sentiment si vis pacem, para bellum, which is a shock as I always assumed it was due to the bullet's parabolic profile.... but I digress), as it is infamous for both over-penetration and under-whelming effectiveness, but [alterother] beat me to it.
All this said, I think the idea would work as intended and might I be so forward as to proffer this pointy pastry?-- MikeD, Mar 04 2012 <hmmph>... I thought pistol rounds were subsonic, but it appears that both 22lr and pistol rounds are *just barely* supersonic (and 22lr will usually be subsonic out of a short-barrelled pistol because there's not enough time to burn all the powder before the bullet leaves the barrel... so there).-- FlyingToaster, Mar 04 2012 //... the odds are approximatly 0:0 ...//
In that case I think you should be scared, because anything divided by zero is /undefined/.-- Loris, Mar 04 2012 Yes, [FT]. The 22 cal *long Rifle* round might not be "up to speed" in a *short pistol*.
<smugly adjusts tie>
All that silliness aside, I think if you could tune the ballistic profile of an asteroid so as to facilitate it's penetration through the crust, then the damage it inflicted on the crust would be much, much less... unless the increase in pressure inside the mantel caused massive volcanic ejection, and tectonic plate shifting world-wide.-- MikeD, Mar 04 2012 // 22lr will usually be subsonic out of a short-barrelled pistol //
The muzzle velocity of any caliber cartridge will vary to some extent depending on the gun it's fired from. Also, if a 'barely supersonic' round like the .22 is fired at a point- blank target, it simply may not displace enough air to produce a 'whipcrack'.
There is a famous anecdote about Bill Donovan, WWII OSS chief and father of the CIA, walking into the oval office while Lyndon Johnson was on the phone. Donovan emptied a bag of sand into a wastepaper basket, produced a prototype silenced .22 (an example of which can be seen in the Spy Museum in Washington D.C.) which was loaded with standard .22 LR (the distinction is important because sub-sonic .22s have a terrible ballistic profile), and fired several shots into the sand. Supposedly, LBJ knew nothing about it until he hung up the phone and Donovan told him what he'd done. While this story may be apocryphal (though it certainly fits with Donovan's character and is an often repeated tale), it is an entirely feasible scenario. I've fired a different variety of 'silenced' .22, and the bullet made no discernable sound at a range of about 15 ft. Other, larger calibers can produce more bullet noise than discharge noise when fired using high-quality suppressors.-- Alterother, Mar 04 2012 //All that silliness aside, I think if you could tune the ballistic profile of an asteroid so as to facilitate it's penetration through the crust, then the damage it inflicted on the crust would be much, much less... unless the increase in pressure inside the mantel caused massive volcanic ejection, and tectonic plate shifting world-wide.//
And surely it would allow all those huge monsters that live down there to escape and wreak havoc. A very irresponsible idea.-- Gordon Comstock, Mar 06 2012 The problem with big asteroids is not the impact, but the dust at impact, which is the reason that shooting them out of the sky would never work, right?
We ought to shoot the astroids with a moist goo, that way they clump rather turn to dust?-- bob, Mar 06 2012 [Gordon Comstock] No worries. Those monsters have evolved to live under extremly high pressure and temperature. They'd either freeze or explode.
What we need to worry about is this: Who wants a projectile that does minimal damage to the skin, and expends most of its kinetic energy disrupting internal organs? A trophy hunter, that's who. What evidence do we have that [zen_tom] isn't some extraterrestrial bwana sahib looking for -- ahem - - pointers on how to bag a planet?-- mouseposture, Mar 06 2012 If he was, he'd have proposed a Nosler-tip asteroid.-- Alterother, Mar 06 2012 Goddamit [Alterother] you had to mention that, did you? We'd bloody well better hope there are no alien planet-hunters hanging around the Halfbakery.-- mouseposture, Mar 06 2012 That would explain a few people.
// The problem with big asteroids is not the impact, but the dust at impact, which is the reason that shooting them out of the sky would never work, right? //
The dust at impact is the problem, but that dust comes from the earth, not the asteroid. If you look at a crater, all that empty volume went up into the sky as dust (and rocks, too). The volume of the asteroid is much, much less.
This idea is based on reducing that Earth-origin dust on impact.
// We ought to shoot the astroids with a moist goo, that way they clump rather turn to dust? //
Creative, but not so good. If the asteroid is made of dust--a rubble-pile asteroid--it will break apart in the air, make a fireball high up, and do nothing worse to the ground than set trees on fire, then provide a few tons of nuclei for raindrops to put the fires out. If you glue the rubble pile together, it will make it to the ground, blow a few zillion tons of bedrock into the air, and make a nice backdrop for the torches of the mob hunting you.-- baconbrain, Mar 06 2012 // We'd bloody well better hope there are no alien planet- hunters hanging around the Halfbakery. //
Just the one, as far as I know.-- Alterother, Mar 07 2012 Two.-- blissmiss, Mar 07 2012 Can't help thinking that if you had the time, money and technology to go up to the asteroid, reform it on the move, and coat it's point with teflon, you could probably work out a much better way of just blowing the thing to smithereens for a lot less effort.
Definitely not as cool though.-- goff, Mar 07 2012 //Can't help thinking//
Try harder.-- MaxwellBuchanan, Mar 07 2012 random, halfbakery