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Exploration

Bolden Says ARM Is About Planetary Defense But Not Protecting Earth

By Keith Cowing
NASA Watch
January 14, 2015
Filed under ,

NASA Watch founder, Explorers Club Fellow, ex-NASA, Away Teams, Journalist, Space & Astrobiology, Lapsed climber.

7 responses to “Bolden Says ARM Is About Planetary Defense But Not Protecting Earth”

  1. Andrew_M_Swallow says:
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    Using military jargon does that mean this is an Exercise rather than an Operation? Since the NEO is not going to hit the Earth.

    • dogstar29 says:
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      Bolden said if the earth was really threatened by an asteroid we could always call the DOD and have them nuke it.

      • blcartwright says:
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        but they have to be able to deliver the nuke, and the nuke would need to be under the surface of the object, because there is no air in space to create a shock wave

        • dogstar29 says:
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          I guess we would have to call Bruce Willis…Actually as you point out the earlier you know about the threat the easier it is to neutralize. So the most important step now is not to move a small boulder server million miles, when what we need to be able to do is nudge a mountain by 1 cm.sec. The thing we need now is an accurate map of all the asteroids and/or comets that might impact the earth.

        • Tritium3H says:
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          blcartwright, that is not correct. A detonation of a nuke 10 feet below the surface of an asteroid would still create a (massive) shock wave. True, the blast does not create an air blast and air shock…but it creates a material shock, which is damn significant. A nuclear detonation would be used to either disrupt and disperse an asteroid, or to nudge/deflect.

          When adequate lead-time exists to divert the oncoming asteroid or comet (>15-20 years), a “standoff” nuclear blast would deflect it off course. When the time to impact is just a few years, it will be too late for deflection…but a carefully executed nuke strike could prevent most damage by disrupting the asteroid, breaking it into smaller pieces, many which miss the Earth completely. Of those that do reach the Earth, many pieces would burn up in the atmosphere. Fragmentation may reduce a global catastrophe to a local or regional problem.

          In fact, the ideal engagement scenario would be to detonate a thermonuclear device at a stand-off distance from the threat (asteroid or comet), provided enough lead-time exists for the intercept to occur far enough out to allow for deflection. The properties and effects of a nuclear detonation in the vacuum of space is different than a detonation within the atmosphere (i.e. high-altitude, medium-altitude, low-altitude, surface burst). In space, the distribution of the thermonuclear weapon’s total energy output is approx. 80% soft x-ray radiation, with the remainder consisting of hard x-rays, gamma rays, neutrons, and kinetic energy of nuclear debris. As there is no atmosphere to attenuate nor transfer the energy of the X-rays, the radiation goes into heating, ionizing and ablating the surface of the asteroid. This ablation and plasma ejecta causes an impulse (like a rocket) which imparts thrust in the opposite direction…slightly changing the velocity (and thus orbital trajectory) of the asteroid. If an asteroid is intercepted approx. 20 years prior to Earth impact, all that is required to change a direct hit to a comfortable miss is a delta V of only one (1) cm/sec.

      • Andrew_M_Swallow says:
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        I will leave it to someone else to calculate the Isp of a nuclear weapon.

        Since we do not have a space navy NASA and its contractors will be responsible for delivering the nuclear weapons.

        Medium sized asteroids can be diverted, hence ARRM.

  2. dogstar29 says:
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