Hello All,

Has anyone ever experimented with solid-fuel (or liquid-fuel) ramjet powered models? I was inspired to consider this by the Estes Teros scale-like ramjet missile kit (see: www.spacemodeling.org/jimz/est1285.htm ), which was similar to NACA solid-fuel ramjet test vehicles that were launched at Wallops Island, Virginia, as described in Reply #7 and illustrated in Reply #8 in this "Ye Olde Rocket Forum" posting (see: http://www.oldrocketforum.com/showt...80&page=1&pp=10 ).

Such models could be quite simple; here is a diagram of a solid-fuel ramjet (see: www.islandone.org/LEOBiblio/SPBI104.HTM ) and a paper on solid-fuel ramjet artillery projectiles (see: http://xrayct.com/documents/data/IBS19/LD24_403.pdf ). A Teros-like model ramjet vehicle would be boosted by a conventional model rocket motor, perhaps with a second motor (a 13 mm mini motor) mounted in the rear of the diffuser center body to ignite the solid ramjet fuel and to provide some additional velocity if needed. (In a sufficiently small model, a single 18 mm rocket motor could boost the model to a high enough speed to provide sufficient pass-through airflow velocity for the ramjet as well as ignite the ramjet fuel with its exhaust plume.)

Ramjets can function at much lower airspeeds than previously thought. The third of the following web sites (see: www.456fis.org/D-21_RAMJET.htm , www.onera.fr/conferences-en/ramjet-scramjet-pde/ and www.okieboat.com/Ramjet%20history.html ) gives examples and descriptions of low-velocity ramjet operation.

The solid ramjet fuel could be a mixture of common mold-makers' Room Temperature Vulcanizing (RTV) rubber and aluminum powder (similar to composite rocket propellant *without* the AP [ammonium perchlorate] oxidizer, in other words). As with some full-scale solid-fuel ramjet vehicles, a small amount of an oxidizer (AP, potassium perchlorate, or potassium nitrate) added to the rubber/aluminum powder fuel would prevent the ramjet from "flaming out" due to momentary fluctuations in the airflow through the engine.

Such model ramjet engines (either solid-fuel or liquid-fuel) would make possible not only Teros-type ballistic models, but also realistic R/C scale models of ramjet missiles such as the Bloodhound, Bomarc, and Talos. Given the high specific impulse and relatively long burn times of ramjet engines, such models might easily be able to fly faster than Mach 1.

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