The Ram Accelerator: Review of Experimental Research Activities in the U.S.

Bruckner, A. P.; Knowlen, C.

doi:10.1007/978-3-319-26018-1_4

Cited by 2 publications

(6 citation statements)

References 82 publications

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“…The theoretical thrust vs. Mach characteristics of TCRA propulsive mode predict quite well the multistage performance of a 38-mm-bore ram accelerator, as shown by the experimental velocity-distance data in Fig. 3-right, which supports the assumption that the end state of the propulsive cycle is indeed thermally choked [13]. In this particular experiment, an 80-g accelerator projectile was accelerated from 1.1 to 2.6 km/s in a 16-m-long test section.…”

Section: Introductionsupporting

confidence: 69%

“…Third, peak velocity of thermally choked ram accelerator is significantly reduced when projectile fins are extended into the projectile throat (point of maximum projectile cross-section) region to better stabilize it as it moves through smooth bore tube [13]. Similar peak velocity reductions were observed in a rail-stabilized ram accelerator using axisymmetric projectiles [15].…”

Section: Introductionmentioning

confidence: 63%

“…Since the projectile is sub-caliber, it is stabilized by projectile fins in a smooth bore tube or with rails mounted on the sidewalls for axisymmetric projectiles. Researchers at the University of Washington Department of Aeronautics and Astronautics have carried out theoretical and experimental research on the ram accelerator since late 1980s [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Ram accelerator velocity regimes are categorized based on velocity of the projectile relative to Chapman-Jouguet detonation velocity (VCJ) of premixed fuel and oxidizer; i.e., subdetonative, transdetonative and superdetonative.…”

Section: Introductionmentioning

confidence: 99%

“…First, heat release of the propellant must be reduced to about 1/3 of which is available (by adding inert diluents), which leads to peak thrust levels of only about 1/3 of the theoretical maximum in order to establish stable operation [13]. Experiments with propellants having larger heat release (less diluent) resulted in the undesirable situation of the combustion wave surging past the projectile, causing the diffuser to "unstart" [14].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, these operating conditions result in extreme pressure spikes because the thermally choked ram accelerator propulsive mode generates pressure ratios of 10-20 times the fill pressure (depending on in-tube Mach). The resulting high pressure at the base of the projectile exerts significant loads on both the projectile and launch tube [13].…”

Section: Introductionmentioning

confidence: 99%

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Transient computational fluid dynamic modeling of baffled tube ram accelerator

Daneshvaran

Knowlen

2017

55th AIAA Aerospace Sciences Meeting

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The minimum entrance Mach number that allowed supersonic projectile transit through a baffled tube filled with inert gas and the thrust generated in reactive flow were examined. The primary parameters considered were chamber-to-projectile diameter ratio, projectile geometry, baffle thickness, baffle spacing and baffle geometry. Axisymmetric and three-dimensional simulations used a dynamic mesh for a projectile moving at constant Mach (ranging from 1.8 to 5.1) through stationary baffles. The maximum baffle thickness and minimum baffle spacing at velocities near the minimum allowable entrance Mach number were both found to be ~53% of the projectile diameter. Further reducing the baffle spacing resulted in the projectile pushing a normal shockwave ahead of it like in a jet engine unstart. It was also found that thicker baffles and closer baffle spacing increased the projectile drag coefficient. Reactive flow phenomena were investigated by first establishing the combustion on the projectile in a smooth bore tube before it entered the baffled-tube section. A key finding from premixed methane and oxygen propellant simulations was that aftward-slanted baffles generated higher thrust than when the baffles were normal to the projectile or forward-slanted. This increase in thrust was associated with more complete propellant combustion in the annular baffle chambers around the tail and base sections of the axisymmetric projectile, as well as immediately behind it. It was also determined that residence time of the propellant during combustion process in the vicinity of the projectile at any given baffle, influences the overall thrust production. As the projectile Mach increases, both the propellant residence time and overall thrust level decrease. 6. Baffled tube parameters include chamber-to-projectile diameter ratio (dc/dp), baffle thickness (tb), and chamber width (wc

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Section: Introductionsupporting

confidence: 69%

Section: Introductionmentioning

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Transient computational fluid dynamic modeling of baffled tube ram accelerator

Daneshvaran

Knowlen

2017

55th AIAA Aerospace Sciences Meeting

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Baffled-Tube Ram Accelerator Operation with Inclined Baffles

Knowlen¹,

Byrd²,

Dumas³

et al. 2017

53rd AIAA/SAE/ASEE Joint Propulsion Conference

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The baffled-tube ram accelerator is a device that has the potential to accelerate axisymmetric projectiles in the velocity range of 0.5 to 3 km/s. Preliminary experiments in a 38-mm-bore device demonstrated that only about 30 to 50% of the theoretical thrust is attained using a baffle geometry that is effectively a solid washer with a center hole bored out with a slight projectile clearance. Recent transient CFD modeling results indicate that significant improvements in thrust generation capability can be realized by inclining the baffles toward the approaching projectile. With this configuration, reactive flow simulations showed that the combustion goes to completion closer to the projectile base than in the original baffle orientation, resulting in a doubling of thrust. Newly fabricated baffles based on this concept are undergoing testing. The results of these upcoming experiments with the new inclined baffle design will be presented.

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The Ram Accelerator: Review of Experimental Research Activities in the U.S.

Cited by 2 publications

References 82 publications

Transient computational fluid dynamic modeling of baffled tube ram accelerator

Transient computational fluid dynamic modeling of baffled tube ram accelerator

Baffled-Tube Ram Accelerator Operation with Inclined Baffles

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