What if it “landed” (more like impacted) at a 90° angle to the comet’s direction of travel? Discounting the extreme difficulty of timing that right (like trying to hit a bullet with a smaller bullet, whilst wearing a blindfold, riding a horse — haha), wouldn’t it dramatically decrease the impact energy?
Think about a car travelling 60mph, and you want to climb aboard. You can either jump on the hood (and likely get made into paste) or jump onto the side and immediately have a 60mph 'jerk' forward.
In either case, you are going from 0 to 60 more or less instantly and the results on your fleshy meat body will be the same.
You could try to run real fast in front of the car, away from it, but you are limited by your meat body's technology to ~10mph. You still hit the car at a difference of 50mph. Meat paste once again.
To avoid a painful collision, you'd need to get up to speeds of about 57mph, which is pretty hard for your body to do. And if you could get up to 57mph, why do you need tha car? There's no friction in space, so you'd just keep going until something bumped you.
If you lasso the car with a deceleration rig or an elastic cord you can accelerate safely tho because it adds delay to how fast the energy is transferred to you.
Yep, the trick is that the lasso needs to be able to stretch enough to accelerate more slowly. You'd also need whatever harpoon you fired into the comet to be able to survive thousands of times its own mass in acceleration.
