Their intent to use GE J85s for the demonstrator is corroborated by the "Boom Fact Sheet" in their press kit: [PDF] https://boom-press-assets.s3.us-west-2.amazo

Their intent to use GE J85s for the demonstrator is corroborated by the "Boom Fact Sheet" in their press kit: [PDF] https://boom-press-assets.s3.us-west-2.amazonaws.com/BoomFactSheet_220825.pdf https://boom-press-assets.s3.us-west-2.amazonaws.com/BoomFac... Three GE J85-15 engines for the XB-1 demonstrator.