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Showing content with the highest reputation on 11/06/2018 in all areas

  1. 5 points
    The full title of this work is "Weaponeering - Conventional Weapon System Effectiveness" by Morris Driels, who teaches at the USN Postgraduate School, and the cover of the edition I have in hand can be seen below. The book aims to "describe and quantify the methods commonly used to predict the probably of successfully attacking ground targets using air-launched or ground-launched weapons", including "the various methodologies utilized in operational products used widely in the [US military]." Essentially, this boils down to a series of statistical methods to calculate Pk and Ph for various weapons and engagements. The author gave the book to my mother, who was a coworker of his at the time, and is of the opinion that Driels is not as smart as he perceives himself to be. But, hey, it's worth a review for friends. I will unfortunately be quite busy in the next few days, but I have enough spare time tonight to begin a small review of a chapter. I aim to eventually get a full review of the piece done. Our dear friends @Collimatrix and @N-L-M requested specifically chapter 15 covering mines, and chapter 16 covering target acquisition. Chapter 15 Mines The mine section covers both land mines and sea mines, and is split roughly in twain along these lines. The land mine section begins with roughly a page of technical description of AT vs AP, M-Kill vs K-Kill, and lists common US FAmily of SCatterably Mines (FASCAM) systems. The section includes decent representative diagrams. The chapter then proceeds to discuss the specification and planning of minefields, beginning with the mean effective diameter of a mine. Driels discusses a simplified minefield method based on mine density, and then a detailed method. The simplified method expresses the effectiveness of the minefield as a density value. Diels derives for the release of unitary mines from aircraft NMines = Fractional coverage in range * fractional coverage in deflection * number of mines released per pass * reliability * number of passes and for cluster type NMines = FRange * FDefl * NDispensers * Reliability dispenser * NMines per Dispenser * Reliability Submunition * number of passes and then exploits the evident geometry to express the Area and Frontal densities. Most useful is the table of suggested minefield densities for Area Denial Artillery Munition and Remote Anti-Armor Mine System, giving the Area and Linear densities required to Disrupt, Turn, Fix, and Block an opponent. Whereas the simplistic method expresses effectiveness as a density, the detailed model views the targets and mines individually, assuming the targets are driving directly through the minefield perpendicular to the width and that there is only one casualty and no sympathetic detonations per detonation. The model computes the expected number of targets destroyed by the minefield, beginning with the Mean Effective Diameter and the PEncounter based on distance from the mine. Driels derives the number of mines encountered which will be encountered, not avoided, and will engage the target. I can't be arsed to type the equations in full, so here you go. The section concludes with an example calculation using the detailed mine method. Overall, this shows the strengths and weaknesses of the book fairly well - it is a reasonable derivation of open-source statistical methods for predicting Pk and Ph and the number of sorties required, but US-specific and limited in scope and depth. The treatment of Sea Mines begins by describing the various types and uses of said mines, importantly noting that they have both defensive and offensive uses, and that the presence of the threat of mines is equally important as the actual sinking which occurs. There are three classifications of sea mines, contact, influence, and controlled. Shallow water mines are treated trivially, considering them equivalent to land mines with Blast Diameter in the place of MED, and assuming that the mines cannot be avoided. Deep water mines are approached in a similar manner, with the desire to determine the number of mines needed to achieve the required probability of damage, and planning missions from there. Two features of sea mines must be considered, however - mine actuation by passing of the target, and mine damage to the target. The probability of activation is, unfortunately, dependent on the depth of the mine and distance, forming a series of stacked bowls as below. The mean value of PActivation is the statistical expectation of the curve. Because I don't feel like screencapping another equation, the Width of Seaway where an actuation can occur is qualitatively merely the area under the actuation curve calculated for a specific mine and target combo. The damage function is also of interest - because we require the mine to both actuate and damage the target, this limits our earlier area under the curve to that area integrated to the limits of the damage function. The selection of mine sensitivity plays a very large role in the effectiveness of our mines. A high setting will lead to many more actuations than damages, which can be indicated by the ratio of the actuation area and the damage area from earlier. Setting the actuation distance equal to the damage distance means that every actuation causes damage, but the probability of actuation is only around 42%. The compromise which selects some Areadamage / Areaactuation of around .8 to .93 is generally preferred. This gives us several useful terms - PA+D = Reliability * Areadamage / Widthminefield . The probability that the first ship to transit a minefield is referred to as the threat, or Threat T = 1 - (1 - PA+D)^NMines = 1 - (1 - Reliability * Areadamage / Widthminefield ) which can obviously be solved for NMines to get the desired number of mines for a desired threat level. Anti-submarine mines are an interesting subset of deep sea mines, as they turn the problem from two-dimensions to three. Driels accounts for this by replacing the mine damage width with the mine damage area, to no one's surprise. Driels claims that the probability of actuation and damage is PA/D = Damage Area / (Width * Depth of minefield). Despite my initial confusion, the reliability term safely reappears in the threat definition below. T = 1 - (1 - (Reliability * Area damage)/(Width * Depth of minefield))^NMines, with a solution for number of mines for given threat level fairly easily taken out as before. Lastly, there is a summary of topics for each chapter, though unfortunately they are qualitative descriptions. Including the final derived equations in this part would be a major benefit, but is overlooked. Ah well. They are quite good for review or refreshing the material. As before, this is a relatively interesting if shallow engagement with the statistical methods to calculate Pk and Ph and the number of sorties required. Going more into detail regarding selecting Threat values or common (unclass) parameters would be interesting, but is lacking. Assuming I don't slack off tomorrow, I should have most or all of the Target Acquisition chapter covered.
  2. 4 points
    Anti-air bobcat design to take away driver's hearing in maximum efficiency SH11 155mm SPG
  3. 4 points
  4. 3 points
    guided artillery shell and GLATGMs
  5. 2 points

    I Learned Something Today

    Today I learned that before Senator Joe McCarthy became famous for his anti-communist campaign, he lobbied for the commutation of death sentences given to a group of Waffen SS soldiers convicted of war crimes for carrying out the 1944 Malmedy massacre of American prisoners of war. McCarthy was critical of the convictions because of allegations of torture during the interrogations that led to the German soldiers' confessions. He charged that the U.S. Army was engaged in a coverup of judicial misconduct, but never presented any evidence to support the accusation. Shortly after this, a poll of the Senate press corps voted McCarthy "the worst U.S. senator" currently in office.
  6. 1 point
    if disagree == True: person = "small penis" * Just had to.
  7. 1 point
    UCF has a database of smokeless powders (apologies if this has already been posted ITT or another) SMOKELESS POWDERS DATABASE
  8. 1 point

    Bash the J-20 thread.

  9. 1 point
    shit ton of HJ-10 NLOS ATGM
  10. 1 point
    300rpm 76mm autocannon i bet this is how this thing sounds like when it fire
  11. 1 point
  12. 1 point
    Damn Americans can't stay away from our bacon hot dogs! Just don't get massacred by cocky elementary school children with snowballs....
  13. 1 point

    Turkish touch

  14. 1 point
  15. 1 point
    speanking of TH-495 variants and from romanian magazine "Știință și Tehnică" 1993-06:
  16. 1 point
    Forecast International's old report on the TH 495 mentions an AGS version in the section "variants": I don't think that they ever made an AGS prototype, but the six-wheeeld TH 495 prototype was fitted with two different medium caliber turrets.
  17. 1 point
    The bolt group of this carbine repeats the bolt of the Garand rifle.
  18. 1 point

    Israeli AFVs

    I saw some parts of this system on upgraded Merkava 3s. https://below-the-turret-ring.blogspot.com/2017/06/merkava-with-ears-its-alwacs.html SH_MM posted in his blog about this (or similar) system. Here it is on Arjun
  19. 1 point

    Polish small arms.

    More pictures from MilMag:
  20. 1 point

    Bash the J-20 thread.

    During night exercises
  21. 1 point

    Fucking NERA everywhere

    A perforated armor scheme for use against a long rod penetrator wouldn't work quite the same way as perforated armor screens on APCs work. Those are mainly to stop 12.7mm and 14.5mm AP projectiles, and the defeat mechanism is often by breaking the penetrator in half. Against a long rod penetrator the mesh would be designed to take advantage of the fact that LRPs yaw into sloped surfaces: Even a very slight angle of attack of the LRP would enormously reduce its sectional density and make it much easier for the rest of the armor array to stop the penetrator.
  22. 1 point

    Fucking NERA everywhere

    I suspect that the metal in the NERA package does make a difference. The latest M1 variants and IIRC latest T-90s are supposed to use titanium in the fancy tryhard frontal composites.
  23. 1 point

    Tank Myths

    No, absolutely not. The only thing related to thermal energy during hydrodynamic penetration is the impact flash, nothing else. It's still being debated whether or not the jet is actually melted or not. Which doesn't even matter since hydrodynamic penetration does not depend on thermal energy even in the slightest. With hydrodynamic penetration the only thing that has a significant effect on the penetration distance is density. Even the strength of the materials are not always relevant. Yes, they have an effect on penetration, but on very high impact velocities the penetrator strength is assumed to be 0. And no, velocity doesn't matter when you're above the hydrodynamic limit of the materials involved. As a matter of fact, an accurate calculation for the penetration depth of a hydrodynamic penetrator is simply p=L*sqrt(ρp/ρt). Which is to say: Penetration depth = Length of penetrator multiplied by the square root of the penetrator density divided by the target density. Source: "Armour; Materials, Theory and Design" by Paul J. Hazell
  24. 1 point

    Tank Myths

    T-72 autoloaders have eaten the arms of enough Soviet tank crewmen that the Russian Army was able to form an entire battalion of slavic Def Leppard tribute bands.
  25. 0 points