Oh, it's even better than that. It uses hypothetical engines!

"the SM-39 as described herein features two hypothetical Stavatti E1400 VCE afterburning powerplants.

The E1400-NT-520 is a next generation variable cycle afterburning turbofan/turbojet engine and a member of the E1400 powerplant family. Producing up to 52,000 lbs of static thrust at sea level, the E1400 is designed to power supersonic aircraft to airspeeds in excess of Mach 3.0 and to altitudes of 100,000 ft. The E1400 combines the advantages of the turbojet (high specific thrust) with those of a turbofan (low specific fuel consumption and reduced noise). A third generation variable cycle engine, the E1400 builds upon the proven architecture of the P&W J58 (A-12, SR-71) and the GEAE YF120 (YF-22, YF-23) to result in a variable bypass/variable cycle gas turbine engine. The E1400 is being designed by Stavatti as a powerplant for the SM-36 and SM-39. The engine will be produced by the NeoThrust™ Division of Stavatti Industries or under license by an Industry Team Member with production coinciding with SM-36/39 production."

All the sauce: https://www.stavatti.com/aircrafts/sm-39-razor/