About as much as it cost to get it to orbit. LEO orbital velocity is approximately 18,000 mph, escape velocity is approximately 25,000 mph, but the energy involved is the square of the velocity.
"Ending up in the sun" would require eliminating the orbital velocity of Earth's orbit around the sun, approximately 66,000 mph. If you're dealing with such energies, it's much easier in theory to use solar sails to provide very light, but continuous, thrust for years.
"Dropping junk into orbit" is a real concern as private companies join the industry, rather than merely military sponsored national spacecraft. It does make the problem more urgent and encourages more active solutions, such as restricting the ejection of spacecraft and requiring registration for them, but that's a very awkward international legal effort NASA has been involved in for decades.
66000mph??? surely there is a vector where it’s already heading towards the sun and all we need to do is lift it up out of orbit not stop the object dead and reverse its direction? That would require a lot less energy.. I’m Probably wrong I’m no rocket scientist
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