“6.5 k/s _seems_ fast, but is it?”

Not really. As you noted, low Earth orbital speed is just about 8 km/s, so an object in an orbit just 60° different would have a closing speed of 8 km/s, too. If it comes from outside Earth orbit, it would be at least 40% faster than orbital speed. Things travel fast in space, so collisions can be catastrophic. That is what the shield is for — it is the one that gets perforated by the disintegrating projectile so that the inner hull (pressure vessel) is only struck by much smaller and much slower debris or gas from the initial collision.

“6mm is important for “will it penetrate?”, but what’s the mass?”

The energy to be dissipated is only linearly proportional to the mass, but it is proportional to the square of the speed, which is clearly the important parameter for this test.

6.5 k/s _seems_ fast, but is it? It looks (via two seconds of searching) as if 9mm bullet velocity is between 900 and 1200 feet/sec. A foot is 0.0003048 kilometers. Clearly they did more than point a 6mm pistol at it and pull the trigger. That makes it seem fast. Orbital speed obviously varies, but LEO seems to be (equally fast search) around 29,000 km/h, which is about 8 km/sec. 6.5 seems both fast and reasonable (the odds of a “head-on” collision in orbit would seem to be small).

6mm is important for “will it penetrate?”, but what’s the mass? A 6mm diameter hollow plastic sphere is very different from a metric ton tungsten rod with a 6mm tip. Is there anything “interesting” about 6mm? Too small to see on radar? Arbitrarily chosen because of how the test rack works?

Not penetrating is obviously better than penetrating, but what makes this test meaningful/interesting? (
A rhetorical question, but if anyone knows, that would be awesome.)

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