Lower-frequency surveillance radar allows enemy air defenses to know that an aircraft is in the vicinity, and higher-frequency engagement radar allows integrated air defenses to target a fast-moving aircraft. The concept with the new bomber is to engineer a next-generation stealth configuration able to evade both surveillance and engagement radar technologies.
The new aircraft is being engineered to evade increasingly sophisticated air defenses, which now use faster processors, digital networking and sensors to track even stealthy aircraft on a wider range of frequencies at longer ranges. These frequencies include UHF, VHF and X-band, among others.
New stealthy aircraft will also likely use speed, long-range sensors and manueverability as additional tactics intended to evade enemy air defenses - in addition to stealth because stealth configurations alone will increasingly be more challenged as technology continues to advance.
However, stealth technology is itself advancing - and it is being applied to the B-21, according to senior Air Force leaders who naturally did not wish to elaborate on the subject.
Although the new image of LRS-B does look somewhat like the existing B-2, Air Force officials maintain the new bomber’s stealth technology will far exceed the capabilities of the B-2.
The B-21 has to have allowances for two feet or more of radar absorbent material coatings on every surface or the designers are forced to make trades as to which frequency bands they optimize the aircraft to operate in. As such, to defeat low frequency radars operating in the L, UHF and potentially the VHF bands (this is easier said than done—and could in fact be impossible), a flying wing design is in effect, mandatory.
The Air Force is planning on building significant electronic attack capability into the B-21 airframe (and the LRS family). Electronic attack capability is necessary to counter low frequency radars operating in the VHF band, which are nearly impossible to defeat with airframe shape and low observable materials alone.