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What would the explosive yield be?

  1. Sep 13, 2007 #1
    What would the explosive yield of a 100kg, 1 meter long, solid core titanium rod falling to the earth from high-orbit be?
  2. jcsd
  3. Sep 13, 2007 #2
    Assuming the bar's kinetic energy was converted entirely into an explosion, Earth's mass ME=6 x 1027 gm and radius RE=6 x 108 cm, and that the bar b was released from infinity, use Newton's law of gravitation:

  4. Sep 13, 2007 #3
    And if I were to use Newton's law of gravitation what would my answer be? I'd do it myself but I really don't know how. I know next to nothing about physics. Thus I came here to ask this question! :tongue:
  5. Sep 14, 2007 #4

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    Using the above values, it comes to around 6.7*10^9 Joules. Hopefully, I haven't made any mistakes.

    And Athyn, why would you want to know the answer to a scientific question if you can't plug in four values? No offence intended.
  6. Sep 14, 2007 #5
    Mainly it is just laziness. But the question was born from a competition between a friend and I. We are both trying to think of weapon systems that would be cheap to manufacture and would also be incredibly powerful. My idea was to fire a solid-core 100kg titanium rod from a satellite in high orbit.
  7. Sep 14, 2007 #6


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    It would mostly just penetrate the gound. Bunker busters were made from the large heavy cannons of battleships, and would simply pentrate many feet of concrete before their fuses would time out and set off the actual explosion.
  8. Sep 15, 2007 #7
    I don't believe that it would penetrate the ground too much. The force of the impact when it hits the ground would probably obliterate it. And even if it did penetrate the ground, the kinetic force of it slamming into the ground would be immense.
  9. Sep 15, 2007 #8

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    Modern bunker busters wiegh more than 2000 kg and are dropped from heights of more than 10 km, if not more. They penetrate into reinforced concrete more than 20 ft, after which the explosives inside blow up and collapse the bunker. So, it may not be obliterated after all.
  10. Sep 15, 2007 #9


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    I would think that there's also some ambiguity about how it impacts the ground. The most likely scenario is that it will hit end-on, which will maximize penetration. If, for some reason, it lands on its side, the situation changes.
  11. Sep 15, 2007 #10
    To compare this device to a bunker-buster, I believe, would be innaccurate. A bunker buster is an explosive device designed to penetrate deep into the ground and then explode. This weapon would just be a solid titanium rod which slams into the ground after being propelled at great speeds from high-orbit. A weapon such as this would be more accurately compared to a kinetic energy penetrator round, fired by modern tanks.
  12. Apr 17, 2009 #11
    So I did the equation for a 7-foot-tall Tungsten rod with a 6-inch radius, but I had the exact number on an online graphing calculator and my friend distracted me so I closed it. Fortunately I had kindof remembered it this way, the force released would be about 84 Quadrillion times the force in Newtons of Earth's gravity on a 70kg person. Basically, it would be REALLY awesome. But I have no idea how much of that force would be directed outwards since alot of it would just be penetrating power. Presumably though with that much force, even a relatively small surface area would result in a pretty good force translation. If anyone here works for NASA, kinetic energy weapons are considered conventional (at least they will be until the first test firing) and conventional weapons aren't banned by the Space Weapons Treaty OR the SALT II. So...make one and test it please. I'll give $100 to the person responsible for setting Project Thor in motion.
  13. Apr 17, 2009 #12
    why titanium? (or tungsten) over any other metal (or non metal). I don't see the advantage of that. Plus you're making a lot of assumptions about the impact which are definetly false (100% of the impact into KE?). In general, it would be a very poor weapon considering what else you could make for less cost. It would be inaccurate, ungodly expensive (you could probably make a dozen nukes for the cost of getting a payload that heavy into orbit), prone to the local weather and I'm not even sure a metal rod, with no special design pre-cautions taken, would make it through the thermosphere
  14. Apr 18, 2009 #13
    Titanium has a melting point of 1725 degrees Celcius. Impressive, right? Well Tungsten, with the highest melting point of all metals, will not melt until it reaches 3422 degrees Celcius. Even if that wasn't enough, its a simple enough problem to fix by simply putting a small layer of silicone on the tip of the rod. It makes perfect sense to be skeptical since we all know that Earth's atmosphere is useful for destroying space debris before it reaches the surface. However, whenever humans have designed something specifically to re-enter the atmosphere we have a pretty good success rate. If anyone tries to counter that statement with something about Challenger or Columbia, take your issue up with Hiaasenburg not me.

    As for the ACCURACY of the weapon, to presume that we wouldn't be able to hit a fly on the end of a beer bottle at the foot of the Lincoln Memorial with this thing would be a leap. The tungsten pole would be stabilized from the rear by a set of GPS-guided fins that could easily guide it directly to its target once it had been released from orbit. Meanwhile, one of the two orbital Thor platforms would be relaying communications between Ground Control and the delivery system to instantly correct any problems as they happen, and ensure the bombardment is delivered to the appropriate target. Basically, think of it as a smart bomb lacking the warhead. It would still have the computer and flight systems to get it exactly where it needs to be, but rather than exploding when it got there it would just kind of...hit. And who can say what happens after that with certainty? (Unless we try it. PLEASE FOR THE LOVE OF GOD TRY IT!!!)

    Next comes cost, the bane of any Space endeavor. However, the statement that putting one of these in space could instead build several nukes is not only false but likewise it makes no sense tactically. I'll start by explaining my second statement. The purpose of Project Thor was not to create an alternative to nukes, but rather to add yet another tactical asset to the war machine's arsenal. SHOULD the project work in the way every fan of awesomeness wants it to, Kinetic Bombardments could take out massive targets without any nuclear fallout or contamination. Lets say, for instance, you have to clear a beach for troop landings or launch a missile attack on an enemy Naval fleet. If you went with the nuclear option, you would contaminate the beach for your own troops and cause God knows how much of a problem by nuking the ocean. But if you replace those nukes with a series of kinetic bombardments, you have an awe-ing display of firepower with none of the inconvenient aftereffects. In addition, nukes are definitely not as inexpensive as people seem to think they are. Weapons-grade plutonium alone costs untold amounts of money just to refine from its original Uranium state. Not to mention the cost of actually building and maintaining a functional ICBM, and employing teams that work year round to make sure all known missiles are up to par and functional. Maintaining a nuclear arsenal is the farthest thing from cheap. And then there are nuclear inspectors to pay, treaties and international meetings to be had for the construction of new nuclear weapons, registering those weapons, blah blah blah. Nuclear arms have become tainted by bureaucracy. They're no longer even an asset, really. As soon as a nuclear weapon is used, you threaten to unlock a cascade effect as other countries start bickering and considering retaliatory strikes. With project Thor, that isn't an issue. Especially since nobody would have the ABILITY to launch a similar attack. The United States originally developed the atomic bomb, and later the Hydrogen bomb, not as a military asset but as a display of power and resolve. Project Thor would be a continuation of that legacy. Plus it might finally lead to some interesting new developments in the fields of physics, communications, and space-to-Earth travel. You'll have to forgive my tangent, i'm just kind of irritated that we haven't made another dedicated effort to colonize space yet.

    Finally, getting the system into orbit. The plan they seemed to have was to use a dual-satellite launch. One rocket would carry the computer guidance system for the weapon, which would remain in orbit indefinitely. The OTHER rocket would carry the firing cartridge loaded with tungsten rods. Once both satellites were in orbit, they would be able to communicate with one another and with Ground Control to alter their orbits and take them over whatever target they are given. In place, a rod will be dropped and guided by weak thrusters until it enters the Earth's atmosphere. From there, the guidance satellite (with a preset target) would monitor the progress of the rod through the atmosphere and bring it to impact on-target in something like 2 minutes.

    You can look up alot of this information yourself online, anything under the term "Project Thor" or "Rods From God" (I personally like the second one) will usually turn up something about the project. Wikipedia has some good information as well about the strategic and tactical assets of Orbital Bombardments.
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