Two stage was the Barracuda concept.
-What we do know about the AIM-260 is that the new missile will have the same general diameter and length as AIM-120. This will, among other things, allow it to be carried inside internal weapons bays on stealth fighters that were designed to accommodate the AMRAAM.
The dimensional requirements mean that a ramjet powerplant, as used in the
pan-European Meteor missile, is impossible. So, a new type of solid-fuel motor seems to be a given, perhaps a dual-pulse type to ensure energy across the flight envelope just like on the PL-15. As
Aviation Week’s defense editor Steve Trimble has pointed out, this new propulsion unit could be combined with miniaturization of other components as a way of increasing the fuel load to eke out yet more range. Advanced highly-loaded grain propellant, which is also being developed for use
in other air-to-air missiles, could help improve performance without increasing the overall form factor.
Publicly released documents reveal that QF-16 jets have been regularly supporting the AIM-260 missile program.
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