The interface where the top and bottom meet (ie the only surfaces normal to the horizon, since they intentionally deleted vertical control surfaces) have relatively sharp edges and curvatures.
Curves are okay, as long as you plan them correctly. The tighter the curve the smaller the radar return. After all, the F-117's corners are (in the limit) just curves with a very tight radius.
The other trick is that (when viewed from the top) all the lines along the perimeter are parallel. That means there are only ~4 azimuth angles where the edges are presented 'face on' to an observer. At all other azimuth angles the radar return will glance off the (importantly, singly-curved) outer edge, bouncing the return signal away from the radar.
Presumably they'll plan flight paths such that these four relatively high-observability vectors will "sweep past" known radar installations rapidly, ideally while the plane is making a turn. All the radar sees is a small, extremely brief blip, which could well be discarded as a bogus radar return (either automatically or by human operators).
No insider information of course, just looking at the shape and applying geometric reasoning.
https://en.wikipedia.org/wiki/Northrop_Grumman_B-2_Spirit
https://en.wikipedia.org/wiki/Northrop_Grumman_B-21_Raider
The interface where the top and bottom meet (ie the only surfaces normal to the horizon, since they intentionally deleted vertical control surfaces) have relatively sharp edges and curvatures.
Curves are okay, as long as you plan them correctly. The tighter the curve the smaller the radar return. After all, the F-117's corners are (in the limit) just curves with a very tight radius.
The other trick is that (when viewed from the top) all the lines along the perimeter are parallel. That means there are only ~4 azimuth angles where the edges are presented 'face on' to an observer. At all other azimuth angles the radar return will glance off the (importantly, singly-curved) outer edge, bouncing the return signal away from the radar.
Presumably they'll plan flight paths such that these four relatively high-observability vectors will "sweep past" known radar installations rapidly, ideally while the plane is making a turn. All the radar sees is a small, extremely brief blip, which could well be discarded as a bogus radar return (either automatically or by human operators).
No insider information of course, just looking at the shape and applying geometric reasoning.