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Comment by rlt | Hacker News Reader

If Starship achieves full and “rapid” reusability then it seems like it would be a lot more feasible to collect and deorbit space junk.

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Most of the list is rocket bodies which are quite large, and rendezvous is already challenging when everybody is collaborating, rendezvous with a tumbling uncontrolled giant piece of junk is even more difficult.

Astroscale is working on that in collaboration with various space agencies, they're currently planning a mission (ADRAS-J2) to connect to an uncontrolled rocket body and deorbit it circa 2027: https://arstechnica.com/space/2025/02/astroscale-aced-the-wo...

Theoretically, a cheap option is to modify Starlink with enlarged argon tanks to rendezvous and "shepherd" large debris into lower orbits. Add LiDAR (DragonEye) and "Push Me Pull You" argon thrusters and it can exert a gentle push even when the debris object is uncontrolled and tumbling.

I'm somewhat surprised SpaceX hasn't tackled this problem yet. Even including just one StarCleaner every 2-3 Starlink launches could make a huge difference.

SpaceX even has the perfect test satellite. RatSat was their first successful launch in 2008, and it's barely decayed despite saying it would only last five to ten years.

https://forum.nasaspaceflight.com/index.php?topic=44753.0

And to answer the cost question, Astroscale is charging $8-100 million [0] per LEO junk removal mission (small numbers for small failed comms sats, big numbers for a spent upper stage).

The objects in the article are all at the bigger end. Presumably Aeroscale have started with a technically easier mission than some of the 50 in the article, but they will also eventually benefit from economies of scale. So you can estimate the cost to remove the 50 bodies in the single digit billions.

[0] https://www.kratosspace.com/constellations/articles/astrosca...

Starship launch costs are hypothetical, but pundits are estimating one to two hundred dollars per kg, or about ten million per launch. This would shave a significant amount off the cost of launching something big enough to de-orbit a large target, like an upper stage. Still, even if you spitball a figure like 20 million for each removal that’s still a billion dollars in total.

"Is charging" for an activity which is wreathed in hypotheticals. Surely it's "proposes charging"?

No, it's signed two contracts already according to the link.

I'm sure the contracts are more complicated than "this amount of money for this job" but the price, at least, is not hypothetical.

Starship lowers launch costs. One can launch more Astroscales with Starship.

It’s not necessary. But it helps turn what is currently research curiosity into something someone can fund at scale.

That tumbling should be conveniently predictable in absence of aerodynamics, but then even the best prediction would leave you with a tough nut to crack. I guess trying to solve that problem could be very helpful as a reality check to reign in any space mining fantasies?

You can deorbit things by pushing them "up" from Earth which lowers their perigee on the other side of the orbit.

A ground based high energy laser could ablate material from Earth which would provide propellant mass and incrementally knock objects into deorbiting trajectories.

And what happens to the ablated material? One large stage that is easily tracked via radar is preferable to tens or hundreds of milimetre size chunks that could potentially flake off while ablating the surface of a rocket stage or derelict satellite.

Ablation turns the material into individual molecules.

Yes, when done perfectly in a lab. Under less than ideal conditions, temperature gradients cause cracks and then flakes are released and expelled.

Drag brings those flakes to the ground.

Flakes of solid material are typically far more than dense than structures made of the same material. Therefore flakes' orbital lifetimes are likely longer than structures made of the same materials.

Pushing "up" on an orbiting body causes no change to the altitude at the other side of the orbit (that is, 180 degrees around the orbit). However, it does raise the orbital altitude 90 degrees ahead, and lowers it 270 degrees ahead.

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