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Comment by ianhawes | Hacker News Reader

New satellites should be equipped with appropriate armor and shielding at this point. Space debris isn’t going anywhere and will likely increase exponentially.

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I suspect that it would take an impractical amount of armor to defend a satellite against a missile with thousands of kph relative velocity

They meant against debris, not missiles. Still easier said than done though. If nothing else, armor would add a lot of weight, which is a major factor when you're launching things into orbit.

An ASAT weapon isnt going to hit much harder than debris. For circular orbits of the same altitude, just a few degrees off on the orbital planes and the velocity difference is in the km/s.

True. Armoring against either one isn't going to be practical.

I think this is another one of those (sub) threads based on a false premise. Shielding on spacecraft and the ISS is totally a thing, because there is a clever way to make practical armor that is light weight. The keyword is "Whipple shield".

"There are over 100 shield configurations on the International Space Station alone"

Whipple shields might succeed in protecting the important parts of the spacecraft, but the kinetic energy of the projectile is still getting absorbed no matter how great your armor is -- and if a spacecraft lacks the propulsion needed to correct its orbit afterward, then there's nothing it can do to defend itself. What good is being intact if your orbit has been irreparably destabilized? (Apart from giving crew some time to abandon a station via their "lifeboats".)

And none of those aim to shield the ISS from an anti-satellite weapon. It probably wouldn't even slow it down. Note the title of this article and that's just the debris of the hit, not the actual hit itself.

What are you alluding to? You think a "weapon" or its byproducts travels much faster than regular debris? Or is more massive?

I assumed the size of the cloud, the quantity and dispersion, is what's making them shelter.

This from the article:

"It is standard space station procedure for astronauts to pile into their vehicles in case of any kind of emergency in case they need to evacuate the space station."

...suggests there could be factors other than the direct vulnerability of the people.

Yes, 'the other factors' are that they are potentially entering a debris field with unknown composition. That alone warrants precautions.

A weapon aimed at ISS would presumably be tailored to that particular application, but at orbital velocities a retrograde projectile would destroy the ISS quite efficiently, even if it had a modest mass. Compared to that this debris cloud is a walk in the proverbial park.

Most modern armor seems to aim to disrupt a projectile before it can penetrate.

The wikipedia page says this type of armor is in use on the ISS already:

"Whipple shields consist of a relatively thin outer bumper spaced some distance from the main spacecraft wall. The bumper is not expected to stop the incoming particle or even remove much of its energy, but to break up and disperse it, dividing the original particle energy among many fragments that fan out between bumper and wall. The original particle energy is spread more thinly over a larger wall area, which is more likely to withstand it. A direct analogy is that a lighter bullet resistant vest is needed to stop a load of birdshot than a single rifle bullet with the same total mass and kinetic energy."

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

Even on Earth, I have the impression that modern armor is a long way from just using thicker steel:

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

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

You can link to wikipedia pages all day long but in reality there just isn't any viable defense against a collision at orbital velocities with anything that weighs more than a couple of grams. Also: whatever armor you want to put on your space ship needs to be launched first and brought up to the same speed as the rest of the vehicle, and this amount of mass will have to be accelerated again every time you want to fix your orbit.

> anything that weighs more than a couple of grams

So where are you reading about the size distribution of the debris?

Here

https://en.wikipedia.org/wiki/Kosmos_1408

and here

https://www.reuters.com/world/us-military-reports-debris-gen...

A 2.2 ton satellite + whatever the mass of the anti satellite weapon creates a cloud of 1500 trackable fragments, so fragments large enough to be tracked by radar from Earth.

See here:

https://www.nasa.gov/mission_pages/station/news/orbital_debr...

"There are approximately 23,000 pieces of debris larger than a softball orbiting the Earth. They travel at speeds up to 17,500 mph, fast enough for a relatively small piece of orbital debris to damage a satellite or a spacecraft. There are half a million pieces of debris the size of a marble or larger (up to 0.4 inches, or 1 centimeter) or larger, and approximately 100 million pieces of debris about .04 inches (or one millimeter) and larger. There is even more smaller micrometer-sized (0.000039 of an inch in diameter) debris.

Even tiny paint flecks can damage a spacecraft when traveling at these velocities. A number of space shuttle windows were replaced because of damage caused by material that was analyzed and shown to be paint flecks. In fact, millimeter-sized orbital debris represents the highest mission-ending risk to most robotic spacecraft operating in low Earth orbit."

So, that's 2.2 tons, split up into 1500 larger pieces (anywhere from a few cm upwards) which is > 5% of the larger pieces that were already in orbit, and a multitude of smaller objects. Each of these has the capability to damage or destroy other spacecraft in that orbit.

Here's what a paint-chip can do to the ISS. https://www.popsci.com/paint-chip-likely-caused-window-damag...

Or worst:

"This is the damage a tiny speck of space debris can do at 15,000mph"

https://bigthink.com/hard-science/heres-the-damage-a-tiny-sp...

Main battle tanks still get destroyed by missiles, the "appropriate armor" you're talking about is fantasy.

>Space debris isn’t going anywhere

It literally is. Space debris in low orbits falls back into the atmosphere. Just stop making more of it and the skies will clear up over time (a few years at most, for most stuff in LEO.)

The average relative velocity between objects in LEO is ~10 km/s with a maximum of about 14km/s [1]. You would have a very hard time shielding against even tiny pieces of metal at those speeds.

[1] The new SMAD

There is no appropriate armor or shielding for debris coming at that kind of velocity

An exponential increase would make space travel impossible in a fairly short time.

An exponential increase is exactly what will happen, once it reaches a certain threshold.

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

Add armor to new space stations, and build lunar colonies!

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