Iron Imperative
An arrow houses micro-ramjet technology. Pores in its shaft brings air which is used for propulsion.
Simuliidae use water currents for absorption of food and excretion.

Problem Statement
We are looking at ways of making everything sustainable and green; cities, industries and food cycles etc. What remains to be tested is war which is as inevitable as anything else. For as long as men remain victim of their egos and profit remains piling, war will never end. So, instead of championing peace as the only solution, can we make wars green too? For a starter, war should be fought outside the cities, like in good old days. When we reflect upon this, we realize that fire-power has much to do with the time in which an individual’s life is losing its worth. A simpler weapon like an arrow needs to be upgraded into a weapon of green war.
Nature Review
The problem calls for organisms that demonstrate an advanced relationship with the fluid (water or air) through which they navigate. One of the most fascinating cases in this regard is the larva of a black fly (Simuliidae). This tiny arrow-like structure aligns itself momentarily, across a water current and uses the force of the current to absorb food and excrete waste. This principle can be mimicked for an arrow which uses cross-winds to its advantage, instead of resisting them.
Technology Review
Since arrow is soundless and no firepower means no thermal tracking, it is most suited for stealth missions.. Many design concepts have been explored and tested which swerve little with the wind. And the internal turbulence and twang of the shaft is used for furthering the projectile. But in order to cover the distances of a bullet, an arrow needs to utilize the energy which drifts across its surface during flight.

Row1Column1: Closeup of Black Fly Larva
Row1Column2: Kinematics and Hydrodynamics of (damsel-fly) Larva
Row1Column3: Closeup of Black Fly Group
Row1Column4: Comparison with Arrow Worm
Row2Column1: Understanding Archery Ballistics
Row2Column2: Wind Dynamics
Row2Column3: Drag Coefficients of Bullets, Arrows and Spears
Row2Column4: True Course and Wind Arrow
Row3Column1: Arrow Tail
Row3Column2: Archery in the Wind
Row3Column3: Smart Arrow
Row3Column4: How to Shoot an Arrow in the Wind
Row4Column1: Magnus Effect on a Ball
Row4Column2: Valuing in Wind
Row4Column3: Cross Wind-Vertical Plane
Row4Column4: On Reading the Windspeed

Nature Gadget
An arrow is designed which flies with the help of multiple variables of wind such as air density, cross-wind and the drag along its surface. There are micro-chipsets (13, 14, 15) of ramjet technology (9, 12-15) which are designed to function for short term, live memory only (21). Air is let in through smart pores (33, 34) running along the shaft. These pores open and close with the spin (31) and dip (36) of the projectile. Air-handling is performed by the microchip which uses incoming air for propulsion (12, 26) only when needed. Since energy cannot be stored onboard and the flight depends solely on the variables of wind, arrow only needs a target (39) within in its conical range, and not a path to follow.

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