Unless it is a really large (KG plus) piece of debris - which such a shield wouldn’t be able to stop anyway - the actual net momentum transferred isn’t significant. It’s the point loading over such a short area and time due to the delta in velocities that causes the damage.

It’s also why being shot in a bullet proof vest with anything man portable doesn’t knock a person backwards (in real life), but gives them a heck of a bruise.

Without the vest, the bullet would go all the way through them, or create a huge wound cavity. [https://whitemountainforensic.com/wound-ballistics-motion-ef...]. Which is what causes the desired fatal effect.

Even when shot with something bigger (such as a tank round), there is no time for the momentum to transfer to their body without destroying it - for the same reason it is impossible to ‘throw’ an egg 20 yards by hitting it with a hammer.

These orbital debris are much much much faster than any known traditional bullets (17 km/s is 55,000 fps or 17x faster than the fastest common cartridge), so the effect is even more pronounced.

Interestingly, there was work by Newton that models these types of penetrations pretty well. They only start to apply to high speed bullet impacts around 3k+ FPS. The type of impact damage becomes noticably different then, with say 5.56/223 Remington on mild steel having an impact crater that looks remarkably like a asteroid impact crater at close range, but a normal ‘flat’ crater/dent at long range once the velocity has dropped significantly.

Once you past the speed of sound in the materials involved, it’s quite predictable based on the density of the material and the length of the projectile.

[https://en.m.wikipedia.org/wiki/Impact_depth]

It’s why modern tank penetrators are made of long, thin rods of high density material (such as depleted uranium or tungsten), and move very fast. They’ll penetrate essentially anything, with only depth varying based on density, because no material is able to transfer the force within itself effectively to ‘reject’ the penetration in time.

Spacing armor also helps, as it gives room for projectile fragments to break apart and lose energy over more area instead of efficiently transferring momentum directly into the point loaded part of the armor, which can dramatically reduce the impact depth in practice.

[https://en.m.wikipedia.org/wiki/Spaced_armour]

Angling the armor on the timescales involved in these impacts isn’t going to meaningfully deflect any penetrators though. It does, however, improve the effective depth of the armor. The forces involved in trying to redirect the later parts of the projectile based on the forces subjected to the first parts of the projectile don’t really work once you pass the speed of sound in the material.

[https://en.m.wikipedia.org/wiki/Sloped_armour]

Counter intuitive based on our normal life experience, but true.

So having many widely spaced layers of hard (to fragment the penetrator) then soft (to ‘catch’ fragments without transferring shock very well into later layers, hence spreading out the force over a wider area and often time) material in as ‘fluffy’ or an armor as possible is the most weight efficient way to stop very high speed projectiles - which is why it is used in space, because weight efficiency is really important.

Notably, heavier/denser versions of this (due to space constraints and the need to stop slower moving and heavier projectiles than in space) are widely used in newer generation main battle tanks in the form of chobham style composite armor. [https://en.m.wikipedia.org/wiki/Chobham_armour]

In those cases, sometimes adding explosives on top can help, as the penetration detonates it, and the resulting shockwave helps disrupt the projectile. [https://youtu.be/zK77-8kJ69c?si=PxMue9goABlfuiXY]

There are some neat videos of simulated tank armor penetrations on Youtube (look for “apfsds penetration test” for one example) that shows what is going on in pretty good fidelity.

So, to summarize - the aggregate force is not a real issue, it’s the damage done by the nature of the very high speed penetration. Think more ‘gamma radiation’, less ‘brick’.