Shooting blocks of Uranium from planet to planet

  1. This idea stems from the Pascal B nuclear test, which placed a 900kg steel plate over a shaft in where a nuclear explosive was detonated: http://en.wikipedia.org/wiki/Operation_Plumbbob#Propulsion_of_steel_plate_cap

    The plate shot up at an estimated 66km/s, or 6x escape velocity. Say you could shoot blocks of weapons grade Uranium from planet to planet, moon to planet, or vice versa. If I understand correctly, the compression when the block lands on the planet's surface would be enough to cause a fission reaction right? These blocks would be small enough to be almost undetectable before it's too late, but big enough to cause serious damage on landing. Unlike the Pascal B test, the launch would be less of an abrupt blast, and more like a slow acceleration so the Uranium wouldn't blow up inside the shaft/gun barrel from compression. Instead of one block, you could shoot a shotgun blast of blocks to maximize the chances of hitting a target.

    So this could be used as a weapon, or possibly a means of terraforming a planet. If you could shoot fission/fusion devices accurately to, say, the ice cap of Mars, you could cheaply sublimate enough CO2 to cause a positive feedback loop and heat up the planet. Also, a means of redirecting asteroids on a collision course with Earth. Would this work? I don't know much about nuclear physics beyond the wiki page.
     
  2. jcsd
  3. SteamKing

    SteamKing 9,133
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  4. DrDu

    DrDu 4,245
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    ...if there were no atmospheric friction...
     
  5. Say the block was adequately heat shielded so that it could survive the launch and reentry. Would the force of impact be enough to trigger a fission reaction?

    Also, I thought the fallout had a relatively short half life, right?
    http://www.straightdope.com/columns...did-hiroshima-and-nagasaki-recover-so-quickly

    Second, most of the radionuclides had brief half-lives--some lasting just minutes. The bomb sites were intensely radioactive for the first few hours after the explosions, but thereafter the danger diminished rapidly. American scientists sweeping Hiroshima with Geiger counters a month after the explosion to see if the area was safe for occupation troops found a devastated city but little radioactivity. Water lilies blackened by the blast had already begun to grow again, suggesting that whatever radioactivity there had been immediately following the blast had quickly dissipated.

    Which isn't good for terraforming, the more fallout at the poles, the more heat and the more ice melted/sublimated.
     
  6. It helps to do some back-of-the-envelope calculations on these things in order to understand the magnitude of the challenge of changing a planetary atmosphere. Say you could generate a 1 megaton nuclear explosion this way. A megaton is 4E15 Joules. The total mass of the Martian atmosphere is 2E16 kg, mostly CO2. Say you wanted to increase the atmospheric pressure 10X, in order to make a significant change. So you need to add 2E17 kg of CO2 to the atmosphere. The heat of sublimation of CO2 is about 600 kJ/kg, so you need about 1E23 Joules of energy to do this. This would require between 10 million and 100 million 1 megaton explosions, assuming all of the energy goes into vaporizing CO2 (which of course it won't). Does this still sound like a good idea?
     
  7. SteamKing

    SteamKing 9,133
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    Hey, if you don't mind some radioactivity in your crops or water supply, go for it. Different types of fallout have different effects on living things. Your thyroid gland can retain radioactive iodine which will eventually give you thyroid cancer. The radiation which your body can tolerate when it is kept outside is one thing. When you ingest radioactive material, your body has almost no way to protect itself from the damaging effects of radiation on tissues.

    It also matters where the bombs are detonated. Air bursts high in the atmosphere generate the least amount of fallout, but winds high in the atmosphere disperse this material over a larger area. Ground bursts generate a great deal of fallout because of irradiation of the soil.

    Surprisingly, the worst fallout problem is generated by underwater explosions, like those done at Bikini atoll. The contaminated water and other debris means that radiation quickly enters the food chain and persists over many years. The islanders were evacuated from Bikini before the tests commenced, and allowed to return briefly after the tests ended. However, when it became clear that the islanders were developing increased cancer due to the fallout, they were evacuated again and the atoll is considered uninhabitable today.
     
  8. Iodine-131 has a half life of 8 days, whether it's in your thyroid or not. So a couple of months after the release it is essentially all gone. Not that that makes planetary uranium bombardment a great idea, but...
     
  9. Let's see how minimal we can make the acceleration during launch - making the most generous assumptions. We'll have no friction after launch so all we need is escape velocity (11,200 M/s). We'll use the deepest bore every accomplished (12,262 M). So the time spent during the acceleration is about 2.19 seconds (t=2*d/v). So the acceleration will be 5115M/s² (a=v/t) or about 522g's.
    I'm wondering if a fission bomb device could be constructed that would remain functional after 522g's for 2.19 seconds?
     
  10. SteamKing

    SteamKing 9,133
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    It doesn't matter that I-131 has a half-life of 8 days. This stuff is taken up by the body and stored in the thyroid gland unless you take a dose of KI (potassium iodide) to keep the body from accumulating the hot stuff. The damage to the thyroid gland is done while the I-131 is stored there.
     
  11. If you start with 1 gram of I-131, wait 120 days, and then ingested it. You will be ingesting approximate 1 grams of Xenon gas and 32 micrograms of I-131. That's about 0.1% of the mean lethal dose. So coating Mars with I131 would not spoil the planet forever - or even for a year.
     
  12. mfb

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    It is highly questionable if that steel plate ever escaped earth. Asteroids of that size disintegrate long before they reach the denser parts of the atmosphere.

    I would be surprised if that is not possible.
    There is a big disadvantage, however: You need a nuclear explosion to launch the object. It is way more convenient to use a regular rocket to deploy a regular nuclear warhead. The object is slower, it will certainly (well, at least >95%) survive the way through the atmosphere.
     
  13. I'm glad I found a discussion already answering my questions. If rather than shooting the uranium at the surface a hole was bore to the center of the of the planet. After which the uranium could be inserted. My thoughts were of using a rail run style projectile into the Moon. The object projected would need to provide the mass for a magnetic field and gravity. If I understand some of the mechanics of what creates the magnetic field the molten element will need to spin.
     
  14. SteamKing

    SteamKing 9,133
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    It's not clear what putting uranium into the center of a plane would do for you, assuming that a means to drill to the center of a planet were available (which is not currently feasible, even on earth).
     
  15. The goal is to make a molten metal core that generates a magnetic field similar to that on Earth. The actual thought I had was to shoot bullets from a rail gun into the moon comprised of nickel and iron. I'm too tired right now to confirm but if memory serves that's what we've proven the Earth's core is comprised of. Even if this weren't feasible a lesser form of device may be potentially able to produce the necessary conditions for the surface of a celestial object to hold an atmosphere. The first being the magnetic field that creates the gravity that holds the right elements on the surface, or is it the mass that makes the gravity an the elements that generate the magnetic field. In combination they are the infrastructure for an M class planet. It's all math and the elements are part of the equation. What's dense and creates a magnetic fields when spinning and really hot or both?
     
    Last edited: Jan 2, 2015
  16. Nugatory

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    Take a look at Phyzguy's post #5 in this thread, and try applying that style of back-of-the-envelope thinking to your idea.
     
  17. If what he's proposing is done closer to the center of the planet. The effects of fusion and fission devices in subsurface atmospheres is, I'm sure, a closely guarded secret. The biggest fear from uranium sounds like fallout, but if the gravity of a planet is great enough wouldn't it pull the radioactive particle toward the center or do I have it all wrong?
     
  18. SteamKing

    SteamKing 9,133
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    What exactly is a 'subsurface atmosphere'?
     
  19. I think a better way to have said that is a sub surface pressure. The atmosphere of an M class planet has several layers. We live in one of them. Oxygen is a liquid at another. Iron and nickel are liquid at others, ect. I guess we name the atmospheres based on their characteristics, which seems to be based on proximity to the center of the planet.
     
  20. Nugatory

    Staff: Mentor

    This thread has gone far off-topic, and when posts about "M class planets" appear, it's time to close it.
     
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