WO2023220504A2

WO2023220504A2 - Baffled start section for ram accelerator

Info

Publication number: WO2023220504A2
Application number: PCT/US2023/064194
Authority: WO
Inventors: Carl Thomas Knowlen; Brian LEEGE
Original assignee: University Of Washington
Priority date: 2022-03-11
Filing date: 2023-03-10
Publication date: 2023-11-16
Also published as: WO2023220504A3

Abstract

A ram accelerator for accelerating a projectile is provided. The ram accelerator includes a baffle section configured to start the projectile in the ram accelerator without an obturator. The ram accelerator generally includes a tube having a projectile bore; and a baffle section operably coupled to a proximal end of the tube. The baffle section has an annular baffle wall defining a central bore axially aligned with the projectile bore; and a propellant chamber arranged adjacent to the annular baffle wall, wherein the propellant chamber is configured to enclose a propellant. The propellant can be ignited as the projectile passes through the baffle section by pressure created by the projectile, by an ignition source, or by a flame carried by the projectile to start the ram acceleration of the projectile.

Description

BAFFLED START SECTION FOR RAM ACCELERATOR

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Provisional Application No. 63/318,882, filed March 1 1 , 2022, the disclosure of which is hereby incorporated by reference herein in its entirety for all purposes.

BACKGROUND

A ram accelerator accelerates projectiles to extremely high velocities using jet-engine- like propulsion cycles based on ramjet and/or scramjet combustion processes. The device operates by propelling a projectile through a stationary' tube filled with a combustible gaseous propellant mixture. The ram accelerator may be suitable for use in applications involving large payloads, such as non-rocket space launch.

In conventional powder-propelled firearms, propellant is burned behind the projectile in a breech, generating high pressure gas which expands as it pushes the projectile down the barrel. As the projectile moves faster, the propelling gas must expend more energy to continue accelerating the projectile. However, once the projectile reaches a critical velocity, the propellant gas exerts only enough force to overcome friction, and thereafter the projectile begins to slow down if the barrel is too long.

Conversely, a ram accelerator functions by filling a launch tube (barrel) with propellant to accelerate the projectile. With a properly shaped projectiie/tube, a unique propulsive cycle can be initiated in which the projectile compresses and ignites the propellant as it travels through the tube. This results in a combustion pulse being accelerated down the tube, where the combustion pulse is self-synchronized with the tailing encl of the projectile. In use, the projectile rides its own combustion wave down the length of the launch tube, allowing the projectile to accelerate to speeds far greater than can be achieved by a conventional powder- propelled firearm.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of the claimed subject matter will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a perspective view of an embodiment of a ram accelerator having a baffled start section formed in accordance with aspects of the present disclosure;

FIGURES 2A and 2B are perspective and side cross-sectional views of the ram accelerator having the baffled start section of FIGURE 1;

FIGURES 3A and 3B are perspective and cross-sectional views of a baffle of the baffled start section of the ram accelerator of FIGURE 1; and

FIGURE. 4 is a perspective view of a baffle with an ignition port in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

The detailed description set forth above in connection with the appended drawings, where like numerals reference like elements, are intended as a description of various embodiments of the present disclosure and are not intended to represent the only embodiments. Each embodiment described in this disclosure is provided merely as an example or illustration and should not be construed as preferred or advantageous over other embodiments. The illustrative examples provided herein are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. As will be described in more detail below, the present disclosure provides examples of ram accelerators having baffled start sections that are capable of accelerating a projectile to relatively high velocities. These and other use case examples described herein should not be considered limiting to the scope of the present disclosure.

Although embodiments of the present disclosure may be described with reference to a configuration of a rani accelerator having ten baffle members in the baffled start section, as shown in the FIGURES, one skilled io the relevant art will appreciate that the disclosed embodiments are illustrative in nature and therefore should not be construed as limited to such an application. It should therefore be apparent that the disclosed technologies and methodologies have wide application, and therefore may be suitable for use with any suitable number of baffle members, or baffle members having different shapes, number of chambers, etc. Accordingly, the following descriptions and illustrations herein should not limit the scope of the claimed subject matter.

FIGURE l is a perspective view of an embodiment of a ram accelerator assembly 100 ('"assembly 100”) having a baffled start section assembly 110 (“baffled assembly 1 10”), and FIGURES 2A and 2B are perspective and side cross-sectional views of the assembly 100, each formed in accordance with aspects of the present disclosure. The assembly 100 has a projectile inlet 102 at a proximal end of the baffled assembly 1 10, a projectile outlet 104 at a distal end of the assembly 100, and a projecti le bore 106 (see FIGURES 2A and 2B) extending axially through the assembly 100, through which an accelerated projectile 130 travels during use of the assembly 100. Although not shown, the projectile inlet 102, the projectile outlet 104, and/or the transition between the baffled assembly 110 and the tube segments 120 can include frangible diaphragms or a fast-actuating valves that opens prior to projectile arrival.

As shown in FIGURES 1, 2A, and 2B, the baffled assembly 110 includes a plurality of baffle members 112 (denoted 112a--1 12j in the FIGURES), the features of which will be described in detail with reference to FIGURES 3A and 3B below. As noted above, although ten baffle members 112a i 12j are shown in the FIGURES, the embodiments described herein may be suitable for use with any number of baffle members configured to start the ram accelerator without the need for an obturator. In other embodiments, the baffled assembly 1 10 is formed from a single component, formed in a clamshell configuration, or the baffle members can include multiple baffles (e.g., five baffle members with two baffles each configured in an assembly creates ten baffles). The number of baffles and the spacing thereof can be adjusted to accommodate a variety of entrance velocities and fill pressures.

The assembly 100 can also include a plurality of tube segments 120 (denoted 120a - 120d in the FIGURES), which can separate the assembly 100 into smaller sections to aid in, e.g , transportation, manufacturing, storage, assembly, cost, etc. In a similar manner to the baffle members 112, any number of tube segments 120 can be used to form the tube of the assembly 100, including a single tube segment. In some embodiments, the tube segments 120 are railed, e.g., including a rail 108 shown in FIGURE 2B, such that an axisymmetric projectile can be guided through the projectile bore 106 by the rail 108. In other embodiments, the tube segments 120 are smooth-bored and a finned projectile (not shown) can be guided through the projectile bore 106 by protruding fins on the projectile. In further embodiments, additional baffle members (e.g., the baffle members 112 or the like) can be positioned between the tube segments 120 to sweep back combustion-driven waves to avoid unstarting the projectile 130.

The conventi onai starting process for a ram accel erator in vol ves using a tube-occluding obturator that compresses residual launch tube gas through multiple shock reflections between the projectile and entrance closure (e.g., the frangible diaphragm or fast-actuating valve that opens prior to projectile arrival ). The obturator produces a region of hot gas that ignites the propellant as the projectile enters the ram accelerator. In conventional ram accelerators, the obturator mass and geometry' are tuned to enable operation of the obturator in the proximity of the projectile for sufficient duration to establish combustion behind the projectile, and then be rapidly decelerated after propellant ignition to allow the combustion products to expand as the projectile travels toward the outlet and keep the combustion driven shock wave from unstarting the projectile. The conventional process can be used with, e.g., smooth-bore ram accelerators (SBRA with fin-stabilized projectiles), railed-tube ram accelerators (Rl'RA with axisymmetric projectiles guided by rails), and baffled-tube ram accelerators (BTRA with baffles spaced at intervals less than the axisymmetric projectile shoulder length). These conventional configurations require a two-piece projectile assembly with the obturator having parasitic mass that increases the requisite launch gun breech pressure. Additionally, the obturator must be blown down and out of the tube or otherwise removed from the system prior to reloading propellant and re-firing the ram accelerator.

The baffled assembly 110 can be used to start the ram acceleration effect on the projectile 130 without an obturator. The baffled assembly 110 includes a series of baffle members 112 arranged axially aligned at the start section of the assembly 100. The configuration of the baffle members 112 allows a propellant to be included in the chambers created by the baffles, where the propellant is ignited by the compression of the residual launch tube gas (e g., air) by the projectile 130. The propellant quantity and concentration in the baffle areas of the baffled assembly 110 can be adjusted based on the projectile and baffle configurations, with such tuning allowing the projectile to reach the desired starting velocities prior to the projectile leaving the baffled assembly area and without unstarting the projectile. In these embodiments, the baffled assembly 110 and the tube segments 120 can contain different propellants that are each tuned to accelerate the projectile 130 to the desired velocity within the respective sections of the assembly 100

In some embodiments, the propellant in the baffled assembly 110 is less energetic based on a delay factor in the baffled assembly 110 and to start the ram accelerator, while the propellant in the tube segments 120 is relatively more energetic to accelerate the projectile 130 to the desired velocity. For example, the propellant in the tube segments 120 can be configured to accelerate the projectile 130 up to the desired muzzle velocity, while the propellant in the baffled assembly 110 can be configured to accelerate the projectile 130 to a desired start velocity upon entering the tube segment portion.

Turning now to FIGURES 3 A and 3B, there is shown perspective and cross-sectional views of an individual baffle member 112 of the baffled assembly 110 in accordance with aspects of the present disclosure. The baffle member 112 includes propellant chambers 1 14 (with four chambers denoted 114a- 114d in FIGURE 3 A). Although four propellant chambers 114a-l 14d are shown, in other embodiments any number of chambers may be suitable for use with the assembly 100, e.g., one, two, three, five, or greater. The propellant chambers 114 are separated by radially inwardly projecting fins 1 15 between each propellant chamber 114, with a first fin 115ab separating first and second propellant chambers 1 14a and 114b, a second fin 115bc separating the second propellant chamber 114b and a third propellant chamber 114c, and so on.

As shown in FIGURE 3B, the baffle member 1 12 can include a central bore 1 17 through which the projectile 130 travels during starting of the assembly 100. The central bore 117 can be sized and configured to be closely concentric with the caliber size of the projectile 130 such that the propellant in the propellant chambers 114 ignites based on the compression of the residual launch tube gas, without unstarting the projectile 130. In some embodiments, the central bore 117 is smaller in diameter than the projectile bore 106 such that the baffled assembly 1 10 effectively starts the projectile ram acceleration. Each of the chambers 114 can further include an annular baffle wall 1 18 adjacent to the central bore 117, and a transitional wall 116 configured to increase the axial strength of the annular baffle wall 118 during combustion, and to direct pressure from the cone section of the projectile 130 axially toward the inlet 102 and/or the combustion gasses radially inward toward the projectile 130 as it passes through the baffle member 112.

FIGURE 4 is a perspective view of a baffle member 212 with an ignition port 240 in accordance with aspects of the present disclosure. In some embodiments, the propellant can be ignited prior to the projectile 130 creating a sufficient pressure within the propellant chambers. In these embodiments, a sequence of ignition sources 242 can be distributed in the chambers 214 of the baffle member 212, with the ignition sources synchronized to ignite the propellant during projectile passage. In some embodiments, the ignition sources 242 are high- energy spark plugs that are timed to fire before the propellant is compressed by the projectile 130. In FIGURE 4, a first ignition port 240a is shown extending into a first chamber 214a, and a second ignition port 240b is shown extending into a second chamber 214b. The first ignition port 240a has a first ignition source 242a and the second ignition port 240b has a second ignition source 242b. Although only first and second ports 240a and 240b, and first and second ignition sources 242a and 242b are shown, additional ports and ignition sources may be included in the additional chambers of the baffle member 212, or only a single port 240 and single ignition source 242 is included in the baffle member 212.

In some embodiments, the ignition port 240 as shown in FIGURE 4 can be used with pre-detonation ignition tubes (not shown) that extend from the chamber 214 to a external spark source to direct a high speed flame or detonation wave into the chamber 214 and directed to the projectile shoulder as the projectile 130 passes through the baffle member 212. In further embodiments, a long burning pyrotechnic, e.g., a rocket motor with rapid-burning propellant, can be operably coupled to the projectile 130 and ignited upon launch or shortly thereafter such that the projectile enters the baffled assembly 110 area with a flaming exhaust that promotes combustion of the propellant. A collection of exemplary embodiments, including at least some explicitly enumerated as “ECs” (Example Combinations), providing additional description of a variety of embodiment types in accordance with the concepts described herein are provided below. These examples are not meant to be mutually exclusive, exhaustive, or restrictive; and the claimed subject matter is not limited to these example embodiments but rather encompasses all possible modifications and variations within the scope of the issued claims and their equivalents.

EC A. A ram accelerator for accelerating a projectile, the ram accelerator comprising: a tube having a projectile bore; and a baffle section operably coupled to a proximal end of the tube, the baffle section having: an annular baffle wall defining a central bore axially aligned with the projectile bore, and a propellant chamber arranged adjacent to the annular baffle wall, wherein the propellant chamber is configured to enclose a propellant, wherein the propellant is ignited as the projectile passes through the baffle section to start ram acceleration of the projectile.

EC B. The ram accelerator of EC A., wherein the baffle section comprises a plurality of baffle members arranged axially in a series, and wherein each of the baffle members includes an annular baffle wall and at least one propellant chamber.

EC C. The ram accelerator of EC A., wherein the propellant chamber is a first propellant chamber, and wherein the baffle section further comprises a second propellant chamber separated from the first propellant chamber by a radially inwardly projecting fin.

EC D. The ram accelerator of EC C., wherein the baffle section further comprises a third propellant chamber and a fourth propellant chamber, each of the first, second, third, and fourth propellant chambers being separated from each other by a radially inwardly projecting fin.

EC E. The ram accelerator of EC A., wherein the baffle section further comprises an ignition port extending through the baffle section and into the propellant chamber. EC F. The ram accelerator of EC D., wherein the propellant is ignited by a spark plug operably positioned within the ignition port.

EC G The rani accelerator of EC A., wherein the propellant is ignited by compression of gas by the projectile within the propellant chamber.

EC H. The ram accelerator of EC A., wherein the propellant is ignited by a flame carried by the projectile as the projectile passes through the propellant chamber.

EC I. The ram accelerator of EC A., wherein the central bore is smaller in diameter than the projectile bore.

EC J. The ram accelerator of EC A., wherein the tube comprises a plurality of tube sections operably coupled together.

EC K. A method of starting a ram accelerator without an obturator, the method comprising: operably coupling a baffle section to a proximal end of a ram accelerator tube having a projectile bore, the baffle section having: an annular baffle wall defining a central bore axially aligned with the projectile bore; and a propellant chamber arranged adjacent to the annular baffle wall, wherein the propellant chamber is configured to enclose a propellant; filling the propellant chamber with the propellant; launching the projectile into the baffle section; and igniting the propellant in the propellant chamber as the projectile passes through the baffle section to start the ram acceleration of the projectile.

EC J The method of EC K., wherein the baffle section comprises a plurality of baffle members arranged axially in a series, wherein each of the baffle members includes an annular baffle wall and a propellant chamber, and wherein igniting the propellant in the propellant chamber includes igniting the propellant in each of the propellant chambers of each of the baffle members as the projectile passes through the baffle member. EC M. The method of EC K., wherein the propellant chamber is a first propellant chamber, and wherein the baffle section further comprises a second propellant chamber separated from the first propellant chamber by a radially inwardly projecting fin.

EC N. The method of EC K , wherein the baffle section further comprises an ignition port extending through the baffle section and into the propellant chamber.

EC O. The method of EC N., wherein igniting the propellant comprises energizing a spark plug operably positioned within the ignition port

EC P. The method of EC K., wherein the propellant is ignited by compression of gas by the projectile within the propellant chamber.

EC Q. The method of EC K., wherein the propellant is ignited by a flame carried by the projectile as the projectile passes through the propellant chamber.

EC R. The method of EC K., wherein the propellant is a first propellant, wherein the method further comprises filling the ram accelerator tube with a second propellant having a different energy than the first propellant.

EC S The method of EC R., wherein the second propellant has higher energy than the first propellant.

In the foregoing description, specific details are set forth to provide a thorough understanding of exemplary' embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that the embodiments disclosed herein may be practiced without embodying all of the specific details. In some instances, well-known process steps have not been described in detail in order not to unnecessarily obscure various aspects of the present disclosure. Further, it will be appreciated that embodiments of the present disclosure may employ any combination of features described herein.

The present application may reference quantities and numbers. Unless specifically stated, such quantities and numbers are not to be considered restrictive, but exemplary of the possible quantities or numbers associated with the present application. Also in this regard, the present application may use the term “plurality” to reference a quantity or number. In this regard, the term “plurality” is meant to be any number that is more than one, for example, two, three, four, five, etc. The terms “about,” “approximately,” “near,” etc., mean plus or minus 10% of the stated value For the purposes of the present disclosure, the phrase “at least one of A and B” is equivalent to “A and/or B” or vice versa, namely “A” alone, “B” alone or “A and B.” Similarly, the phrase “at least one of A, B, and C,” for example, means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C), including all further possible permutations when greater than three elements are listed.

It should be noted that for purposes of this disclosure, terminology such as “upper,” “lower,” “vertical,” “horizontal,” “fore,” “aft,” “inner,” “outer,” “front,” “rear,” etc., should be construed as descriptive and not limiting the scope of the claimed subject matter. Further, the use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings

Throughout this specification, terms of art may be used. These terms are to take on their ordinary' meaning in the art from which they come, unless specifically defined herein or the context of their use would clearly suggest otherwise.

The principles, representative embodiments, and modes of operation of the present disclosure have been described in the foregoing description. However, aspects of the present disclosure, which are intended to be protected, are not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restri ctive. It will be appreciated that variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present disclosure Accordingly, it is expressly intended that all such variations, changes, and equivalents fall within the spirit and scope of the present disclosure as claimed.

Claims

CLAIMS The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A ram accelerator for accelerating a projectile, the ram accelerator comprising: a tube having a projectile bore; and a baffle section operably coupled to a proximal end of the tube, the baffle section having: an annular baffle wall defining a central bore axially aligned with the projectile bore; and a propellant chamber arranged adjacent to the annular baffle wall, wherein the propellant chamber is configured to enclose a propellant, wherein the propellant is ignited as the projectile passes through the baffle section to start ram acceleration of the projectile.

2. The ram accelerator of Claim 1 , wherein the baffle section compri ses a plurality of baffle members arranged axially in a series, and wherein each of the baffle members includes an annular baffle wall and at least one propellant chamber.

3. The ram accelerator of Claim 1 or 2, wherein the propellant chamber is a first propellant chamber, and wherein the baffle section further comprises a second propellant chamber separated from the first propellant chamber by a radially inwardly projecting fin

4 The ram accelerator of Claim 3, wherein the baffle section further comprises a third propellant chamber and a fourth propellant chamber, each of the first, second, third, and fourth propellant chambers being separated from each other by a radially inwardly projecting fin.

5. The ram accelerator of any of Claims 1-4, wherein the baffle section further comprises an ignition port extending through the baffle section and into the propellant chamber

6. The ram accelerator of Claim 4, wherein the propellant is ignited by a spark plug operably positioned within the ignition port

7. The ram accelerator of any of Claims 1-4, wherein the propellant is ignited by compression of gas by the projectile within the propellant chamber.

8. The ram accelerator of any of Claims 1-4, wherein the propellant is ignited by a flame carried by the projectile as the projectile passes through the propellant chamber.

9 The ram accelerator of any of Claims 1 -8, wherein the central bore is smaller in diameter than the projectile bore.

10. The ram accelerator of any of Claims 1-9, wherein the tube comprises a plurality of tube sections operably coupled together.

11. A method of starting a ram accelerator without an obturator, the method comprising: operably coupling a baffle section to a proximal end of a ram accelerator tube having a projectile bore, the baffle section having: art annular baffle wall defining a central bore axially aligned with the projectile bore; and a propellant chamber arranged adjacent to the annular baffle wall, wherein the propellant chamber is configured to enclose a propellant; filling the propellant chamber with the propellant, launching the projectile into the baffle section; and igniting the propellant in the propellant chamber as the projectile passes through the baffle section to start the ram acceleration of the projectile.

12. The method of Claim 11, wherein the baffle section comprises a plurality of baffle members arranged axially in a series, wherein each of the baffle members includes an annular baffle wall and a propellant chamber, and wherein igniting the propellant in the propellant chamber includes igniting the propellant in each of the propellant chambers of each of the baffle members as the projectile passes through the baffle member.

13. The method of Claim 1 1 or 12, wherein the propellant chamber is a first propellant chamber, and wherein the baffle section further comprises a second propellant chamber separated from the first propellant chamber by a radially inwardly projecting fin

14. The method of any of Claims 11-13, wherein the baffle section further comprises an ignition port extending through the baffle section and into the propellant chamber.

15. The method of Claim 14, wherein igniting the propellant comprises energizing a spark plug operably positioned within the ignition port.

16. The method of any of Claims 11—13, wherein the propellant is ignited bycompression of gas by the projectile within the propellant chamber.

17. The method of any of Claims I T 13, wherein the propellant is ignited by a flame carried by the projectile as the projectile passes through the propellant chamber.

18. The method of any of Claims 11-17, wherein the propellant is a first propellant, wherein the method further comprises filling the ram accelerator tube with a second propellant having a different energy than the first propellant.

19. The method of Claim 18, wherein the second propellant has higher energy than the first propellant.