As with the wartime Me 163 rocket fighter, the P.154 was to have relied on a jettisonable, three-wheeled "dolly" for its ground-running /take-off action and have to land on a skid-equipped belly for the return trip.
Beyond the proposed internal rocket engine, which would have been an in-house Saunders-Roe-developed rocket motor, the design was also proposed with additional take-off thrust by way of rocket boosters and another idea involved the installation of a compact turbojet for propulsion power for the return trip home.
In terms of armament, the P.154 was envisioned as having two retractable housings at the rear section of the fuselage to contain 25 x RP aerial rockets each. Only later was thought being given to supporting 2 x "Blue Jay" air-to-air missiles. In either case, both weapon arrangements were strictly intended for the interception role and mainly for large enemy warplanes such as bombers (whose airframes often went on to double as reconnaissance platforms due to their inherently good range).
While never built, SARO engineers provided some estimates for their proposed creation: it would have a maximum speed reaching nearly Mach 2.5 at altitudes of 60,000 feet and climb-rate would be in excess of 13,500 feet-per-minute - qualities brought about by the focus on rocket propulsion (though at the expense of limited range due to excessive fuel burn). The aircraft was to have reached 60,000 feet in a little over two minutes and, beyond this, the structure would see a running length of 37 feet with a wingspan of 26 feet. Gross weight was to reach nearly 13,300lb.
At any rate, the P.154 was not furthered beyond its paper stage though Saunders-Roe's own "SR.53" development, detailed elsewhere on this site, at least went on to make it to the prototype stage before being terminated.
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