Method and apparatus for initating stable operation of a ram accelerator
First Claim
1. In a ram accelerator, including a projectile having an aft portion and a linearly extending tube having a bore, at least a portion of which is filled with a combustible mixture of a gaseous fuel and an oxidizer, apparatus for preaccelerating the projectile, and for initiating a stable combustion zone behind the projectile, comprising:
- force generating means for providing a force acting on the aft portion of the projectile so as to accelerate it to supersonic velocity, propelling it into the portion of the tube filled with the combustible mixture; and
throttling means that are independent of the projectile and its profile, for controlling the velocity of a shock wave generated at the aft portion of the projectile as the projectile enters the combustible mixture by controlling the dynamic impulse pressure immediately behind the projectile so that the shock wave does not propagate ahead of it, said throttling means causing the shock wave to instead attach to the projectile, thereby establishing a stable subsonic combustion zone along the aft portion of the projectile in which combustion of the gaseous fuel continues to accelerate the projectile down the bore of the tube.
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Accused Products
Abstract
A method and apparatus for supersonically accelerating a projectile in a thermally choked subsonic combustion mode. A projectile (50) is initially preaccelerated using either a tank (24) of compressed helium or a chemical propellant charge preaccelerator (152). The projectile enters a portion of a tube (22) filled with a combustible mixture (54) of a gaseous fuel and an oxidizer and is propelled by a ram acceleration process as the mixture burns. In several different embodiments, various devices are used to control the velocity of a shock wave generated as the projectile enters the combustible mixture and the dynamic impulse pressure immediately behind the projectile, so that the shock wave attaches to the projectile along an aft portion, thereby establishing a stable subsonic combustion zone along the aft end (64) of the projectile, in which combustion of the gaseous fuel accelerates the projectile down the bore of the tube. In one embodiment, a perforated sabot (52) is used to propel the projectile during preacceleration. The sabot has a plurality of passages (114) extending longitudinally between its front and rear surfaces, which are initially closed with a thin plate (110) during the preacceleration of the projectile. However, the plate is dislodged as the projectile enters the combustible mixture, allowing the dynamic pressure of the shock wave caused by the sabot to dissipate through the open passages.
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Citations
30 Claims
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1. In a ram accelerator, including a projectile having an aft portion and a linearly extending tube having a bore, at least a portion of which is filled with a combustible mixture of a gaseous fuel and an oxidizer, apparatus for preaccelerating the projectile, and for initiating a stable combustion zone behind the projectile, comprising:
force generating means for providing a force acting on the aft portion of the projectile so as to accelerate it to supersonic velocity, propelling it into the portion of the tube filled with the combustible mixture; and
throttling means that are independent of the projectile and its profile, for controlling the velocity of a shock wave generated at the aft portion of the projectile as the projectile enters the combustible mixture by controlling the dynamic impulse pressure immediately behind the projectile so that the shock wave does not propagate ahead of it, said throttling means causing the shock wave to instead attach to the projectile, thereby establishing a stable subsonic combustion zone along the aft portion of the projectile in which combustion of the gaseous fuel continues to accelerate the projectile down the bore of the tube.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for initializing stable ram propulsion of a projectile along a bore of a tube having at least a portion thereof filled with a combustible mixture of a gaseous fuel and an oxidizer, comprising the steps of:
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(a) preaccelerating the projectile upstream of said portion of the tube, so that it enters said portion at a supersonic velocity relative to the combustible mixture; (b) independently of the projectile and its profile, throttling the shock wave caused as the projectile enters said portion of the tube, so that on an aft portion of the projectile, the velocity of the shock wave is approximately equal that of the projectile; and (c) initiating a stable combustion zone immediately behind the projectile, combustion of the mixture in said zone accelerating the projectile along the bore of the tube. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22)
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23. For use in a ram jet accelerator in which a projectile is accelerated to a supersonic velocity prior to entry into a bore filled with a combustible mixture of a gaseous fuel and an oxidizer, a method of establishing a thermally choked mode for propelling the projectile through the bore, comprising the steps of:
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(a) independently of the projectile and its profile, controlling the velocity of a shock wave generated as the projectile enters the combustible mixture so that it does not propagate down the bore at a velocity greater than that of the projectile; (b) creating a subsonic flow over an aft portion of the projectile as it passes down the bore; and (c) initiating a stable combustion zone along the aft portion of the projectile, in which the combustible mixture burns to propel the projectile down the bore. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30)
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Specification