with manipulator arms to close with and grapple uncooperative bits of orbital detritus.
“I’m not detritus, yet!”
“But you will be.”

Assuming the politics can be worked out, the direct ascent vehicle can be a fraction of the size and cost. of the debris to be deorbited. The 750 kg defunct sat at 7,500 m/s orbital velocity smacks 75 kg of blanket at 0 m/s velocity from a suborbital launch. Theoretically the sat would experience a 750 m/s deorbit impulse that would put it in the ocean in a fraction of an orbit. In operation though, the solar arrays and other lightweight appendages would lose much more velocity while the dense main body would receive a smaller impulse. Say the main body of 500 kg only smacks 5 kg of the total. That would provide only a 75 m/s of deorbit impulse which may or may not get the job done. This with a vehicle with a mass ratio of <4 and payload of 75 kg which is easily RTLS.

The direct may not be the best, it is just the most economical I know of at this time. Especially as testing could be done on even smaller scale with the various 1-10 kg chucks flying around. After solving the political and the financial, the technical can happen fairly rapidly.

Similarly a few years ago both Boeing and Lockheed had satellites fail on-orbit due to the failure of a part by a subcontractor. The article announcing the failure of the Boeing satellite had Boeing’s name all over it but not the name of the subcontractor. Contrast that to the Space News article announcing the failure of the Lockheed-built GOES Next satellite, which mentioned only the subcontractor but not Lockheed.

It’s not just the mainstream media that is lopsidedly biased.

A simple system can be modified for space, it’ll need a better guidance system with gyros.

Launch a platform in high orbit with 10 to 20 guided missiles a board. Sooner or later, all satellites will pass beneath it that are not geosynchronous.

When the target passes beneath the platform, launch controlled missile to match orbit and speed with a proximity detector timed just before soft Impact to wrap up the satellite. Allow Gyro package slow rotation to get orientation correct, then fire the remaining fuel to deorbit the package at the correct time over the proper ocean.

Not fancy, but practical and doable for problem satellites. Smaller versions for sweeping debris/chunks out of the sky may also work. (Picture a large chunk of foam adjusting attitude and direction on a collision course with smaller pieces as it slowly falls out of orbit.)
Space laser, mounted to platform, can deorbit the smallest pieces. (firing only over water of course)

Putting aside the non-trivial matter of who will pay to do orbital garbage collection, there is no need for human crew in the loop. That would radically increase the minimum cost of the vehicles required for no functional gain. It would also require incurring the ongoing expense of supplying crews and rotating them periodically. In essence, human-crewed debris-chasing vehicles would be small space stations that would also do a bit of trash pickup as a sideline. The tail would wag the dog.

Current AI tech is more than adequate to enable an entirely autonomous space tug with manipulator arms to close with and grapple uncooperative bits of orbital detritus.

The best orbits in which to both test, then operationally deploy, such technology are the sun-synchronous ones. Not only are most of the problematical DoD and NOAA weathersats in such orbits but so are a very high percentage of dead cubesats and other smallsats that were deployed there by rideshare missions – particularly SpaceX’s Transporter series. Many companies use these missions to try out new technology and the items deployed display a fairly high rate of stillbirth and infant mortality. That makes the sun-synchronous orbits target-rich environments for debris removal.

There are a number of such orbits that all have nearly the same inclinations and differ mainly in altitude. It’s a much less energy-intensive job to significantly change the altitude of an orbiting object – like a debris-hunting tug – than it is to significantly change its orbital inclination.

To minimize total delta-V change requirements still further, it might make sense to deploy multiple debris-chasing tugs – each at a different sun-synchronous orbital altitude. One could also deploy one or more propellant depots at each altitude to service the tug or tugs operating there.

The good and bad about hypergolics—they can last a long time up there.

SpaceX ISS deorbit tug could be the design to handle other such space junk.

The hypergolics should allow it a long time to fulfill its mission—de-orbiting itself and its final target end of life.

Blackwing1: From my post:

Note I do not expect or want the government to take the lead in this. This issue is mostly a need of the satellite industry, of which the world’s governments are merely just one more participant. This industry should band together to set up a fund to pay for this work, with those governments joining as just one more partner.

This had been the traditional way things were done in America before World War II. The government might have been a player, but the private sector led and did not want that government to play a large part.

We have to get back to that mindset.

I still believe that this is a great opportunity for free-market enterprise in space. A simple brute-force “tug” could be put in orbit, with large grapples and some big thrusters for the sole purpose of changing the orbits of these pieces of junk, and then return back to it’s own orbit. It would almost have to be manned, given the difficulty of matching orbits and spin with the debris, but having it’s own docking station, routinely re-supplied with fuel and consumables, is not beyond reach.

The bigger question is who would pay for the re-entry destruction of defunct satellites; probably either the owners (if private) or launchers (if state-owned).