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Kear_Bear_3747 t1_jajfhid wrote

Reply to comment by lagavulinski in NASA’s DART data validates kinetic impact as planetary defense method | DART altered the orbit of the asteroid moonlet Dimorphos by 33 minutes by mepper

In space, objects will absorb all of the momentum of the object. That’s basic Newtonian Physics, dealing with Inertia.

On Earth it matters because there are other forces in play like Gravity and Friction so kinetic energy can dissipate in different ways, whereas in space there’s nothing to arrest that energy, it will impart itself on whatever object it collides with.

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lagavulinski t1_jajh7fb wrote

Thanks for the explanation. However, I believe you and I aren't discussing the same thing. I do agree with your explanation of Newtonian physics though.

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coriolis7 t1_jajr75p wrote

Not exactly. Momentum is always conserved, but the kinetic energy is not. A fully elastic collision preserves kinetic energy, while a partially inelastic collision does not.

In both cases m1 x v1(initial) + m2 x v2(initial) = m1 x v1(final) + m2 x v2(final).

However, only in the fully elastic collision does the following hold: [m1 x v1(initial) + m2 x v2(initial)] / 2 = [m1 x v1(final) + m2 x v2(final)] / 2

It doesn’t matter if it’s in space, in a lab, or wherever.

I think what the above redditor was saying is that because the outer material was more loosely held, more of the material could be ejected. That ejected material has additional momentum. Even though the probe never bounced off (ie elastic collision) the ejected material made the collision act as partially elastic.

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workingdad83 t1_jaju14g wrote

Oh yeah. 2√(brdsrntreel)+2 carry the 4. See I can just push a lot of buttons too.

Joking. I know you are smarter than me, and I was lashing out. I'm sorry.

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coriolis7 t1_jak3dle wrote

Sorry about the formatting, it makes a lot more sense when you see it properly formatted. The unformatted above is kinda dry to the eye.

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gdpoc t1_jajjufm wrote

Doesn't it also matter whether what you're hitting is an isotropic homogeneous solid and how much of that is aggregate v fill when we talk about celestial body surface composition?

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ResponsiblePumpkin60 t1_jajzk3m wrote

I think the only thing that matters is how much energy is lost from ejecting impact debris off into space. If none is ejected, then no energy is lost.

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