E.Deorbit (2016) | Hacker News Reader

E.Deorbit (2016)

esa.int

23 pointsacqq19 comments

"The mission is being prepared for approval during the next ESA Council at Ministerial level in late 2016"

Anybody knows what happened then? What's the current status?

A set of slides from a presentation given by Luisa Innocenti, head of the Clean Space program at ESA, seems to indicate ongoing testing and a 2024 launch date. I couldn't find anything more concrete, unfortunately.

http://www.jsforum.or.jp/stableuse/pdf/26%20Innocenti_eDeorb...

Thanks, very good presentation!

There's also a link to the "cleanspace" blog there at the end:

http://blogs.esa.int/cleanspace/

Last post July 6, 2018, the project lives.

Then from there, "The Clean Space Industrial Days 2018" event

https://indico.esa.int/event/234/

will happen: "23-25 October 2018 ESTEC"

Once the proof of concept is demonstrated, an interesting development is to use a robotic arm to disassemble the junk and grind it into fine dust that can be used as propellant for an electrostatic engine: https://arxiv.org/abs/1511.07246

This way, a single mission can hop from orbit to orbit bringing down hundreds of targets instead of a sole suicidal mission.

Another way for serial junk cleanup is to have a number of electrodinamic tethers and attach one on each target after de-tumbling. Even a few hundred meters of conductor materials (carbon fibre) would drastically reduce time in orbit.

“This paper has been withdrawn by the author due to a crucial sign error in figure 1”

Sorry, here's a cached copy: http://erewhon.superkuh.com/library/Space/Spacecraft/Debris%...

Regardless of any redaction errors, the basic idea is sound. While the particle engine is not able to produce the large impulse of ion drives (low specific ionization), it turns out the optimal impulse for such an application is in the 100-200 range. Any higher and the thrust drops too much prolonging the mission duration, for a given amount of electric power available.

For this application the opposite is true: you want maximize thrust and throw away the full mass of the previous target before reaching the next one to be consumed.

“Regardless of any redaction errors, the basic idea is sound.”

As far as I know the basic physics, the whole energy for the movement would still NOT come from the crushed satellite pieces but from some energy source in the satellite destroyer.

Of course, it's electric propulsion so most likey solar. But the unlimited propellant mass allows for a much higher thrust than typical for satellites and quick (days, weeks) orbital hops.

Using nets or arms seems wasteful to me, to be honest; you'd need to bring a new satellite up there for every piece of debris you want to get rid of. Wouldn't it be a lot more convenient to use something like laser ablation to slow down the debris and make it burn up in the atmosphere on its own?

I don't know the process of laser ablation. How would you use it in the context of this mission?

With laser ablation you fire a high-wattage laser as something to turn a very small surface layer to plasma. The expanding plasma cloud imparts an impulse onto the surface it is ablating, which can be used to slow down debris.

https://en.wikipedia.org/wiki/Laser_propulsion#Ablative_lase...

Laser ablation would create debris, wouldn’t it?

Technically, yes. You would cause some plasma to be formed, but I don't think it would in any way worsen the Kessler Syndrome situation.

Surprised to see this posted here! As a student I had a chance to take part in e-deorbit symposium in 2014. Back then they were considering 3 methods for capturing satellites: a net, robotic arm and a harpoon of sorts.

What struck me the most from this conference is realizing how big of an issue space junk can be. From back then I remember the was no rules on disposing of satellites, the owning body could decide for a nice approach and use the fuel to put the satellite in a higher orbit, or slow it down so that it burns in Earth atmosphere. Or they could not give a shit and use the remaining fuel for operations, maximizing the profit.

Are we saying that in the last 70 years or so, we managed to litter space so bad that this is actually a problem?

Help me understand here: aren't we talking about a volume of space with a radial cross section significantly larger than the surface of the earth?

I find it hard to believe we've launched so many things that collisions have become likely.

Any actual data out there on the number of objects in orbit and the likelihood of collision?

What am I missing?

The problem is that if a collision happens it produces a lot of debris on unpredictable orbits. This process can run away and lead to orbital denial: https://en.wikipedia.org/wiki/Kessler_syndrome

The best source is NASA.

https://orbitaldebris.jsc.nasa.gov/

The faq says:

> More than 21,000 orbital debris larger than 10 cm are known to exist. The estimated population of particles between 1 and 10 cm in diameter is approximately 500,000. The number of particles smaller than 1 cm exceeds 100 million.

Don't forget that these tiny fragments can cause significant damage.

You miss that the kinetic energy is proportional to the square of the speed.

https://www.quora.com/Which-one-makes-a-bullet-dangerous-its...

The speeds at which even the smallest debris hit other satellites are immense, compared to what we are used to in our surroundings. International Space Station moves at the speed of 17 thousand (!) miles per hour. Even the small pieces of something else moving at the different speed or direction will be extremely destructive, see again the explanation about how the bullets "work."

Then consider the number of the pieces there and the fact that their movements are "unstable" (as in not keeping the trajectories that are always at the same distance from the Earth).

Only once you understand all that read about:

https://en.wikipedia.org/wiki/Kessler_syndrome

China showed a few years ago that blasting satellites with missiles is neither subtle or sustainable. This kind of thing could be weaponized much more efficiently

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