The planned B21 stealth bomber will likely use a pair of unaugmented 28,000lbs-class F135s engines from the F-35 With some tweaks, such as an increased bypass ratio, a version of the F135 could probably produce more than 30,000lbs of thrust while potentially increasing fuel efficiency. Sixty thousand pounds of thrust should be more than adequate for a highly efficient flying wing that’s slightly smaller than the B-2.
The B-21’s electronic warfare systems will most likely be an advanced derivative of the F-35’s AN/ASQ-239 system—which is BAE Systems most advanced product. It is known that BAE Systems offered a much more capable next-generation electronic warfare suite that was rejected because of its lack of maturity. The B-21—with its open architecture design—will be provisioned to accept replacement hardware as time goes on.