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Message: <blockquote data-quote="Nagol" data-source="post: 7486201" data-attributes="member: 23935">The only way an intermediary helps is if it already has energy that can be used against the target.  If you have to pick up the target and accelerate it, it is only helpful if you have extra time or if energy output of the suit is not the limiting factor for the acceleration.  In other words, if the suit has the force to accelerate a 100 kg human at 50 g, but humans go unconscious at 3 g then the hero could afford to pick up and accelerate about another 1500 kg and stay conscious.Let's change the asteroid's composition to have density of 8 (solid iron) and set the orbit to a ~100 year elliptical.  The math for calculating the instantaneous velocity isn't hard, particularly, but I'm rusty enough not to do it on the back of an envelope.  Let's guess the velocity at 1 AU would be about 3 times the base velocity of a circular orbit with the same period or 20 km/s and further assume its going counter to the planetary motion so we can increase the closing velocity to 50 km/s.To achieve the same kinetic energy of my original assumption 12 million tonnes at 11 km /s, we have ~600,000 tonnes at 50 km/s and it has about a 25 m radius.Let's push the rock further out to say the hero intercepts it 1 hour from Earth (about 180,000 km out).  The necessary deflection is much smaller.  We still need to shift about 1,000 km, but we have 3,600 seconds to complete the shift or merely about 350 m /s. If she picks up 1,500 kg and accelerates at 2 g for the whole trip, it takes a bit over an hour to arrive (4200 seconds) and will be travelling a bit over 40 km/s compared to the Earth.  That gives a relative closing velocity on the target of about 80 km/s.  The 1,500 kg mass in an elastic collision would cause the target to gain about 400 m/s vector (and thus miss Earth) and the 1,500 kg slug would bounce back at nearly 80 km/s.  Since it unlikely the slug could survive those g-forces, the hero would have to evade the expanding shrapnel cloud.Actually, this assumes a side strike appropriately perpendicular to the target's forward motion.  So toss in another hour or so of travel time to line the shot up.</blockquote>

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