I think the counter to shielded tanks would not be “use an attack that goes slow enough not to be slowed by the shield”, but rather one of
Deliver enough cumulative kinetic energy to overwhelm the shield, or
Deliver enough kinetic energy in a single strike that spreading it out over the entire body of the tank does not meaningfully affect the result.
Both of these ideas point towards heavy high-explosive shells. If a 1000 pound bomb explodes right on top of your tank, the shield will either fail to absorb the whole blast, or turn the tank into smithereens trying to disperse the energy.
This doesn’t mean that shields are useless for tanks! They genuinely would protect them from smaller shells, and in particular from the sorts of man-portable anti-tank missiles that have been so effective in Ukraine. Shields would make ground vehicles much stronger relative to infantry and air assets. But I think they would be shelling each other with giant bombs, not bopping each other on the head.
Against shielded infantry, you might see stuff that just bypasses the shield’s defenses, like napalm or poison gas.
Re 1, we worldbuilders can tune the strength of the shield to be resistant to 1000 pound bombs probably.
Re 2, I’m not sure, can you explain more? If a bomb goes off right next to the tank, but the shockwave only propagates at 100m/s, and only contains something like 300lbs of mass (because most of the mass is exploding away from the tank) then won’t that just bounce off the armor? I haven’t done any calculations.
The ‘missing’ kinetic energy is evenly distributed across the matter within the field. So if one of these devices is powered on and gets hit by a cannonball, the cannonball will slow down to a leisurely pace of 50m/s (about 100mph) and therefore possibly just bounce off whatever armor the device has—but (if the cannonball was initially travelling very fast) the device will jolt backwards in response to the ‘virtual impact’ a split second prior to the actual impact.
With sufficient kinetic energy input, the “jolt backwards” gets strong enough to destroy the entire vehicle or at least damage some critical component and/or the humans inside.
A worldbuilder could, of course, get rid of this part too, and have the energy just get deleted. But that makes the device even more physics-violating than it already was.
Kinetic energy distributed evenly across the whole volume of the field does not change the relative positions of the atoms in the field. Consider: Suppose I am in a 10,000lb vehicle that is driving on a road that cuts along the side of a cliff, and then a 10,000lb bomb explodes right beside, hurling the vehicle into the cliff. The vehicle and its occupants will be unharmed. Because the vast majority of the energy will be evenly distributed across the vehicle, causing it to move uniformly towards the cliff wall; then, when it impacts the cliff wall, the cliff wall will be “slowed down” and the energy transferred to pushing the vehicle back towards the explosion. So the net effect will be that the explosive energy will be transferred straight to the cliff through the vehicle as medium, except for the energy associated with a ~300lb shockwave moving only 50m/s hitting the vehicle and a cliff wall moving only 50m/s hitting the vehicle on the other side. (OK, the latter will be pretty painful, but only about as bad as a regular car accident.) And that’s for a 10,000 lb bomb.
We could experiment with tuning the constants of this world, such that the threshold is only 20m/s perhaps. That might be too radical though.
I think the counter to shielded tanks would not be “use an attack that goes slow enough not to be slowed by the shield”, but rather one of
Deliver enough cumulative kinetic energy to overwhelm the shield, or
Deliver enough kinetic energy in a single strike that spreading it out over the entire body of the tank does not meaningfully affect the result.
Both of these ideas point towards heavy high-explosive shells. If a 1000 pound bomb explodes right on top of your tank, the shield will either fail to absorb the whole blast, or turn the tank into smithereens trying to disperse the energy.
This doesn’t mean that shields are useless for tanks! They genuinely would protect them from smaller shells, and in particular from the sorts of man-portable anti-tank missiles that have been so effective in Ukraine. Shields would make ground vehicles much stronger relative to infantry and air assets. But I think they would be shelling each other with giant bombs, not bopping each other on the head.
Against shielded infantry, you might see stuff that just bypasses the shield’s defenses, like napalm or poison gas.
Re 1, we worldbuilders can tune the strength of the shield to be resistant to 1000 pound bombs probably.
Re 2, I’m not sure, can you explain more? If a bomb goes off right next to the tank, but the shockwave only propagates at 100m/s, and only contains something like 300lbs of mass (because most of the mass is exploding away from the tank) then won’t that just bounce off the armor? I haven’t done any calculations.
2 is based on
With sufficient kinetic energy input, the “jolt backwards” gets strong enough to destroy the entire vehicle or at least damage some critical component and/or the humans inside.
A worldbuilder could, of course, get rid of this part too, and have the energy just get deleted. But that makes the device even more physics-violating than it already was.
Kinetic energy distributed evenly across the whole volume of the field does not change the relative positions of the atoms in the field. Consider: Suppose I am in a 10,000lb vehicle that is driving on a road that cuts along the side of a cliff, and then a 10,000lb bomb explodes right beside, hurling the vehicle into the cliff. The vehicle and its occupants will be unharmed. Because the vast majority of the energy will be evenly distributed across the vehicle, causing it to move uniformly towards the cliff wall; then, when it impacts the cliff wall, the cliff wall will be “slowed down” and the energy transferred to pushing the vehicle back towards the explosion. So the net effect will be that the explosive energy will be transferred straight to the cliff through the vehicle as medium, except for the energy associated with a ~300lb shockwave moving only 50m/s hitting the vehicle and a cliff wall moving only 50m/s hitting the vehicle on the other side. (OK, the latter will be pretty painful, but only about as bad as a regular car accident.) And that’s for a 10,000 lb bomb.
We could experiment with tuning the constants of this world, such that the threshold is only 20m/s perhaps. That might be too radical though.