This RR announcement doesn't really change anything; they never had an RR engine planned, they just had RR doing some design studies.
GE F110/F118 is probably the closest off-the-shelf engine to what Boom needs, and of course the core has common heritage with CFM56. I doubt it has the efficiency Boom needs for TPAC, but at least it's something that exists, and with a bit of de-mil work, Boom could actually buy it.
If Boom wants a contemporary engine for their project, they're going to need to cough up the $5B it's going to take to develop, since none of the established players will roll the dice on them.
Originally Posted by
TerryK
Did Boom use GE engine for their small scale test model? I wonder why GE didn't continue to develop full size engine for Boom?
The GE J-85 engine for the Boom XB-1 demonstrator is a 1960s cruise missile engine that was previously repurposed for the T-38 trainer among other platforms. It was just a supersonic-capable engine they could easily acquire, probably second (or more) hand, in the right thrust range. No real involvement from GE.