Heat beam

Would it be possible to make a machine that would emit a beam of heat energy, said beam tapering off after a set distance?

That would certainly make it easier to mow the lawn . . .

Any input at all would be appreciated!

Like a light sabre, a beam that just goes out so far, then stops abruptly?

No. Not without something to stop it at the other end.

Beam of heat energy = infrared laser.

A high-powered heat gun is pretty effective, but only at very short range. It’s basically a blowdryer that’s amped up a lot. Good for peeling paint.

Er… all light is “radiant heat.” It doesn’t have to be invisible.

Put your hand in the beam of a twenty watt CW green laser and see if you don’t detect a scent akin to burning hair. Look at a light bulb filament and you’ll see some heat radiation.

For cutting grass you’ll want a laser frequency which isn’t reflected well. Plants look fairly white in the IR bands, so maybe a blue laser would work better.

Ideally you’d want to surround your yard with mirrors. This would “recycle” the beam if it should happen to miss a grass blade on the outward trip. It would also keep birds, pets, and small children from developing char marks.

On the other hand, maybe a water-jet cutter would work better. Nikola Tesla clamed that his device was effective over huge distances. It used electrically-accelerated mercury droplets.

You could use a multiple ir-laser approach to build a grass incinerating system. Make each individual beam too weak to do more than lightly warm a blade of grass, and build an elaborate guidance system to converge a couple dozen beams at a precise, variable point in space. With proper guidance software, you could trim your lawn one blade at a time. Building such a system would be enormously expensive.