EXTERNAL-JET PROPULSION ANALOGY FOR PHOTONIC PROPULSION
"BLASTING" MICRO-CRAFT ON JETS OF HIGH VELOCITY WATER

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Figure-1, Sphere-cone micro-craft (0.70 grams) riding on a "blast" of high velocity water

External-jet propulsion uses a narrow jet of high velocity water or conceptually a bank of high power lasers to “blast” micro-vehicles to high velocity. The goal of this work was to create a design analogy for launching micro-sized laser-propelled probes to 20 percent of the speed of light to the nearest stars. However, this work also resulted in the practical capability to launch micro-craft on external jets of high velocity water having a mass of only 0.7 grams, which represents the smallest known reusable jet propelled vehicle in history. A sphere-cone projectile having a hollow interior shaped like a diverging nozzle demonstrated the concept of propelling projectiles to high velocity using the principal of conservation of linear momentum. An extremely narrow streamtube of high velocity water directed into the interior of a sphere-cone successfully demonstrated stable flight and high acceleration for an inherently unstable projectile. For a description of this work download the paper (2.5 MB) from viXra e-print archive.


Figure-2, VisualCFD™ velocity contour plot. Cd = 0.515 and Cdbase = 0.129

VisualCFD™ easily determines Cd for aerodynamic shapes using 3-D source panels to solve the frictionless Euler equations for subsonic compressible flight. The axial drag coefficient predicted by VisualCFD was then inserted into a MathCAD flight analysis that is described in the viXra e-print archive for an accurate flight profile of the projectile.


Figure-3, AeroRocket wind tunnel used to determine sphere-cone projectile drag coefficient

This section presents results from the AeroRocket subsonic wind tunnel used to validate the drag coefficient (Cd) predicted by VisualCFD. The same sphere-cone projectile used for flight testing was mounted in the test section of the wind tunnel mounted on a 0.0 degree angle of attack sting. The following table displays the comparison between results computed by VisualCFD and results determined by wind tunnel test. These results indicate VisualCFD is an excellent way to quickly and easily predict drag coefficient of subsonic projectiles.
  Cd
(Base reference)
% Difference Rn U (m/sec)  T (degrees F)
Air Temperature
VisualCFD 0.515 -3.6 18,000 14.2 90.0
Wind Tunnel 0.534 --- 18,000 14.2 76.0