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OnlySlightlyCrazy

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  1. OnlySlightlyCrazy

    General Naval Warfare News/Technology thread.

    Perhaps you're misunderstanding the survivability onion. The destructive capability of modern naval weapons is such that you *can't* effectively counter enemy weapons at the "Penetrate" layer of the onion. (Though warships are still pretty decent at the "Don't be K-Killed" category barring the Norwegians.) The ability to fight an EM war where you avoid detection, recognition, engagement, and being hit is a far more effective form of survivability, since you avoid being hit in the first place. Enemy steel on your steel is never a good thing, regardless of how well armored you think yourself to be. An excellent practical example of this is Pico's sterling work How to Hide a Task Force. By fighting in the EM spectrum, a USN CBG was capable of operating with impunity despite being in range of very capable enemy strike complexes which was more than capable of killing them dead.... except they couldn't.
  2. OnlySlightlyCrazy

    Bash the F-35 thred.

    https://www.documentcloud.org/documents/3514589-Executive-Summary-of-VMFA-121-Support-of-Red.html I'm significantly concerned about how poor the F-35's readiness is, especially with the overly-complex F-35B version. A properly thorough analysis of the program should result in cancellation any day now.
  3. OnlySlightlyCrazy

    Partial Review of Driel's "Weaponeering"

    I finally got around to doing a review of the Acquisition Chapter. Apologies to @N-L-M for the delay, and apologies in advance for the length. This topic comes at perhaps an opportune time given a previous conversation with @Sturgeon regarding the Survivability/Lethality Onion. In this model of lethality, a target must be First, Seen Once Seen, Acquired Once Acquired, Hit Once Hit, Penetrated Once Penetrated, Destroyed With survivability obviously working in reverse. This model has proven quite robust and is extremely popular amongst those studying weapon systems and their survivability. Its terms are generally self explanatory, though it's worth clarifying the first two. Seeing refers to the perception of any given object via some form of sensor. Acquisition, then, refers to processing the perceived object *as a target*, by some form of identification or feature recognition. That pretentiousness aside, Driels in this chapter will address both topics; the US Joint Munitions Effectiveness Manual (JMEM) considers them in three parts: Target Detection, Target Recognition, and Target Identification under the titular Target Acquisition model. Detection under JMEM’s model correlates most closely with “See” under the Onion, with the remaining two falling under Acquiring the target. Driels begins by outlining several historical physiological and psychological models for Target Detection, before describing the work by Johnson which is at the core of the US Army’s Acquire model. Terrain, run-in effects, and conversion of range to probability of launch are accounted for, and the factors are combined with the Acquire model to describe the JMEM’s Target Acquisition model. Unlike the prior chapter, this chapter is much more explicitly focused on Air-to-Surface weaponeering. While the physiological and sensor models will obviously hold true for a variety of detectors, they are used here exclusively to create a model for the range and probability at which an aircraft will detect some ground target. Terrain masking is equally applicable to cases beyond that of Air-to-Surface, but such things as run-in effects and the minimum time taken to bring an aircraft to a required heading are limited in their application. Published in 1970, the JMEM Air-to-Surface Target Acquisition Manual divides the acquisition process into the aforementioned three steps of detection, recognition, and identification. Their exact definitions have been included here to preserve the granularity. Blackwell’s research during WW2 began with experiments into the contrast values required to just discriminate circles projected on a screen. Importantly, target size in Blackwell's model is angular in a fashion evident to anyone familiar with MOA. Beginning with a definition of contrast as C = abs val of (Luminance of Stimulus - Luminance of Background)/(Luminance of Background) And of relative contrast as Cr = actual target contrast / threshold contrast This definition becomes clear when one examines the situation where Cr = 1, wherein threshold conditions apply and detection probability is 50%. A table of threshold contrast values has been included here, followed by detection probability as a function of the relative contrast. Practically speaking, to predict detection with this model would require calculating the angular size of the target, then calculating the actual contrast of the target, looking up the threshold contrast, calculating the relative value, and finally determining the probability of detection with the graph. Evidently a complex and lengthy process, these limitations motivated the creation of further detection models. Overington’s model seeks to correlate the target size and target contrast to the point at which the target is just detectable. This begins with the assumption that the target generates a stimulus between two adjacent retinal receptors between which the boundary of the target and background is located, the magnitude of which will obviously depend on the magnitude of the contrast. Through a complex series of equations that do not bear reiterating, a relationship is drawn between .163 * Contrast = K1 * nReceptors + δ Where K1 is some constant and δ is the minimum stimulus the brain can detect. From this equation, a threshold contrast value can later be obtained. A great deal of care is paid to the amount of receptors which will be stimulated - the minimum even when seeing very small objects (eg stars) is cited as nine.To account for this, a value of nReceptors = 9.9[(height + width)^2 + .83]^.5 is derived, where height and width of the object are in mrads. Overington then solves K1 and δ experimentally; they depend on the retinal luminance, which is itself dependent on the scene luminance and the pupil diameter. These equations are not directly solved, and the reader will have to content themselves with the relation of K1 = 15.4 Retinal Luminance-.5 + .48 And δ = .00125 Retinal Luminance -.5 + .0004 With Retinal Luminance equal to pi*pupil diameter squared * scene luminance * 1/4 We can obviously now simplify our earlier equation into Contrast Threshold = (K1 * nReceptors + δ)/.163 Which is in good agreement with the Blackwell model from earlier. It would later be discovered, however, that these models under-predicted the threshold contrast luminescence. Testing conducted by Johnson in the 1950s wherein observers viewed the side of an M48 (a tank not know for it’s small size, as N-L-M will doubtless attest) showed that the threshold value was higher by around a factor of three compared to the Blackwell and Overington models. My only brief complaint with this section is that it would benefit from a lengthier comparison between the predicted values and the empirical values for threshold contrast. The history and physiology is interesting, of course, if somewhat dry if all we are given is a simple “it does not work by this factor”. Johnson’s Frequency-Domain Experiments grew out of these simple “detection” tests, beginning with the fact that mere detection is not sufficient for many military tasks, and that neither a threshold data nor model existed for the tasks of recognition or identification. Initial experiments showed that a nonlinear scaling existed of contrast required with range, which led Johnson to model targets in a frequency rather than spatial domain, best explained visually here. Each pair of black and white (practically, gray and dark gray) lines is a cycle, and the cycles per milliradian is the cycle frequency. The equivalence between a cycle frequency and a target is constructed as follows. 1. A small image of a military target is projected onto a black screen. 2. An observer is rolled into a position where he can just detect that there is an object on the screen. 3. The image is replaced with a rectangle made of very high cycle frequency bars. The frequency is reduced until the observer can just determine the number of bars. 4. The rectangle is replaced by the image, and the observer is wheeled forward until he just recognizes it. Step 3 is repeated. 5. Step 4 then 3 are repeated with the observer having to identify the target. The procedure's results have been included here. This is a strikingly robust and useful model, and has proven sound even when applied to a number of passive sensors such as FLIRs, TVs, and image intensifiers. With it, we can predict acquisition ability of a sensor by measuring its ability to resolve contrast modulated bar patterns. In this passage, Driels discusses an extremely fascinating way of looking at sensors, in a method that’s surprisingly easy to follow given his early work in the chapter. The model seems so simple and robust that one questions why the earlier models are even included, as the Acquire Model to soon be discussed uses Johnson’s work rather than the earlier physiological models. The US Army’s Acquire Model makes use of Johnson’s Frequency-Domain work, while accounting for significantly more factors. The model begins by calculating the critical dimension (sqrt of the presented area) in mrads, and then selecting an intrinsic contrast value based on the illumination, background, detector, and filters. The attenuation due to atmospheric factors is also taken into account, though the JMEM model only accounts of distance and meteorological factors. Using these factors, the apparent contrast at the sensor is calculated, with Apparent Contrast = Intrinsic Contrast * Sky to Ground Luminance * e(-3.91 * Range Kilometers / VIS) VIS represents the atmospheric visibility, and is defined as the range at which contrast is diminished to 2% of Intrinsic Contrast. The sensor in question is then analyzed using Johnson’s method described earlier. A common measurement standard is a four-bar pattern which can be of varying frequency - ie, the bars can be very few or very many milliradians wide. For a given frequency, the illumination through the sensor is increased from zero until the bars are just able to be distinguished, and this value of contrast is paired with the frequency to construct a Minimum Resolvable Contrast curve. A particular value of frequency for a given apparent contrast on this curve is a Spatial Frequency, yielding N cycles resolved = SF * critical dimension / Range Acquire then features a probability for some task (either Detection, Recognition, or Identification) as a function of the ratio between the number of cycles resolved and the number required for a 50% chance of that task being accomplished, included here. This is a very powerful result, and is again presented quite cleanly and clearly. I appreciate these two passages a great deal more than the earlier parts, especially since they seem most easily applicable to things outside the A2S realm. Flight profile accounts for the fact that an aircraft does not always approach the target directly down the line of sight, and that several actions must occur for a successful attack even after the target is detected. The aircraft must decide to attack, must roll into and then execute a turn before exiting the turn and operating the weapon system - respectively XD, XRI, XRO, XOP, and RMIN in the diagram here. These will combine with the beginning kinematics and geometry - the turn radius of the aircraft r and nose angle ⍺ - to produce the following RRQ equation. RRQ = (A cos ⍺ + r sin ⍺) +- Sqrt[ (A cos ⍺ + r sin ⍺ )^2 - (A^2 - B^2)] This minimum range to maneuver and launch will be included further along in the model in addition to the maximum range for detection. An omission which may be deliberate is the possibility to reverse engineer a target approach to maximize the possibility of detecting the target in time to launch a weapon. Searching refers to the process of moving the sensor’s field of view, the solid angle which it can actually “see”, over the entirety of the solid angle the sensor is capable of moving, referred to as the field of regard. Driels places this towards the end of the chapter, but it appears best suited to address earlier. The US Army’s Acquire model expresses the probability of detection as P = P1 x P2, where P1 is some time-independent probability of detecting the target, and P2 the conditional probability for some amount of time, best explained below. Terrain has the effect of blocking almost all sensors used by aircraft, with the particular quandary that terrain can vary quite rapidly and unpredictably. (Something anyone attempting to learn land navigation can attest to.) Driels constructs a workable model for the angle at which an aircraft’s sensors are unmasked as follows - for a given “type” of terrain, place an observer at some random point. The observer measures the angle to the highest terrain feature along a given bearing, which is the unmask angle. This repeats this for the entire circle, producing a cumulative probability distribution of the unmask angles, and the process may be repeated for a variety of terrain types to any desired level of granularity. The JMEM target acquisition model covers flat farmland, smooth desert, rolling farmland w/ close forests, rolling desert, flat farmland with close forests, gently rolling hills, rough desert, and sharply rolling hills with trees, though it should be evident that any particular terrain type could be easily calculated. The omission of any form of urban terrain is puzzling, however, and the question of which existing terrain to model it with is thought provoking. Perhaps sharply rolling hills with trees? That this 2004 book does not cover the acquisition of targets in urban terrain is no great discredit, as it has likely been accounted for in more recent versions of the JMEM acquisition model, but it certainly merits further discussion moving forward to a doubtless more urbanized battlefield. There are now models in hand for the two major limits on range of detection, terrain and visibility, and from this Driels proceeds to construct a conversion between range and the probability of detection and launch. This equation, and the cumulative probability that one can derive from it, accounts for not only the distance the aircraft must close to before detecting the target, but also the time taken to search the volume available to the sensor suite and the minimum time/distance required to maneuver the aircraft to launch position. The constant K accounts for the skill level of the pilot, Pmax is assumed to be 1, R is the smaller of the unmask range or the visibility detection range established earlier, RRQ is the minimum range to maneuver and drop. A series of calculations have been performed in the chart here - these seem to be far lower than occurs in reality, potentially due to the choice in parameters. Driels then details the usage of the JMEM Target Acquisition Model, a screen of which is included here. (Note that PL is significantly higher than his table earlier.) Inputs to the model can be taken from the Joint Air-to-Surface Weaponeering System (JAWS), as well as additional information regarding the target, vision conditions, weapon trajectory, and launcher kinematics - the latter two obviously determining RRQ. In Summary, the chapter examines physiological models of detection by Blackwell and Johnson, addresses their implementation in the US Army’s Acquire model, and then details the Joint Munitions Effectiveness Manual’s use of Acquire and the additional information its model includes. This chapter is interesting and offers a great deal of unexploited potential - the models are all extremely fascinating, and I can easily imagine their direct applicability towards S2S or passive A2A detection. Crucially, however, the acquisition models all appear to completely negate *active* sensors, possibly for reasons of confidentiality. Still, the fundamentals behind the two-way radar equation aren’t that complex, and could easily be slotted into the existing maximum range of visibility parameter. Beyond that, it is an interesting chapter, and one of the most insightful in the book. I think I'm done with the book for now. I may do some simulation of infantry fires by plagiarizing Driels' direct fire chapter, but that is a tale for another day.
  4. 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.
  5. OnlySlightlyCrazy

    Aerospace and Ordnance discussion/news.

    "In the past few years, the threat scope has changed dramatically, as Soviet operations have expanded, and the Chinese bomber force has been modernized with the introduction of the Badger H-6K." Lel. "A Super Hornet with three external fuel tanks and a full air intercept load of 6 AIM-120D has rather limited effective combat radius of around 400 miles." If only there was a long-ranged multirole fighter in production which hadn't lost out to the F-16. Makes one wonder. "allow for the Super Hornet to widen the engagement range of a carrier strike group in the BMD role." I'm unsure if that's anywhere near as feasible as you think it is. Overall, I'm in favor. Give us the turbo-dick version of the AIM-120, but put it on your real fighters instead.
  6. As a side note, the US can no longer claim that M855A1 fragments by accident. "A noteworthy feature of the fielding of M855A1 is the inclusion of the terminal effects protocol for testing soft target performance during lot acceptance testing to ensure Soldiers are getting consistent ammunition. The M855A1 is the first round to undergo such a rigorous test during lot acceptance." (An Army Outgunned-A Response Anonymous. Military Review; Fort Leavenworth Vol. 92, Iss. 6, (Nov/Dec 2012): 102-103.) Not that we ever should have, mind. Bullets exist to kill, we gain nothing by being bashful about it.
  7. OnlySlightlyCrazy

    How Not to Post in the Historical Warfare Section

    @N-L-M @A. T. Mahan What makes the green grass grow? BLOOD BLOOD BLOOD!
  8. OnlySlightlyCrazy

    How Not to Post in the Historical Warfare Section

    I would, at least, like to compliment Peasant for sticking to his guns despite being horrendously overmatched qualitatively and quantitatively, and getting slaughtered as a result. In this, he does the IJN proud.
  9. OnlySlightlyCrazy

    Starter Firearm Thread

    Man transformation Thursday Monday is wild as as all hell.
  10. OnlySlightlyCrazy

    Starter Firearm Thread

    A big part of the reason why this advice is so valuable is that mainstream = cheap and easy accessories. No, you don't need to rice your handgun out at first, but having access to the best holsters, cheap and good magazines (as opposed to cheap or good), and easily accessed spares for if/when things breaks is reassuring. Agreed, but I would like to add something. As I'm sure Sturgeon can attest (having held everything from the first to the latest AR-15s), the AR is delightful in large part because of it's modularity. Although it won't be an issue for you within the first, say, 1-2 years of owning and shooting an AR-15 (possibly more!) the dated components of a Colt 6920 are primarily in the upper receiver group, which is not legally a firearm. It is thus entirely possible to keep your existing AR-15 and buy or build a new, hyper-modern, whiz-bang upper receiver and install it on your rifle merely by popping a few pins. There is a lot of upward growth potential in a rack-grade 6920 when you're ready to do so.
  11. You wouldn't mind gracing us with an estimated G7, would you?
  12. You should drop some more info on 5.7 Hermes. And enter it into NGSC
  13. OnlySlightlyCrazy

    Aerospace and Ordnance discussion/news.

    My naive response to that is that the Target Detection Device needs to be as far forward as is practical in order to keep your warhead on target when it fuzes and detonates. (At 25kft a Mach 2 missile will pass the entire length of an F-4 Phantom in .06 seconds, which is before you address the fact that the target is moving and you need time for your continuous rod to get on target.) This is a shared configuration with the AIM-7, also a continuous rod warhead missile. Given that the R-27 is a 1980s era missile, it's also possible that the autopilot is electromechanical, not digital, and therefore cannot be trivially removed from the seeker via cable. All this is, of course, speculation.
  14. OnlySlightlyCrazy

    Aerospace and Ordnance discussion/news.

    I should probably clarify what is the grognard's opinions - and these are opinions, he hasn't seen any actual design documents on the R-27/AA-10 - and what are my own assumptions working off of what he posited. Grognard (almost verbatim): The [R-27...] was designed as something that would counter the AIM-7F missile and would have better maneuverability and expanded F-Pole over the Sparrow. The missile is much larger than Sparrow, particularly the longer range variants. The stuff he's seen says that the AA-10 has Canard control. I guess you could take your choice whether its Canard or Mid-body wing control. In any event, the control fins are place closer to mid-body than to the nose. These mid-body control finds need to be larger to generate maneuvers because the moment arm between the center-of-pressure and center-of-gravity is much smaller than for true canard or tail control. The sparrow also has large wings for this reason. Given the large size of the control surfaces, he suspects that the designers were trying to provide “wing-like” surface for long range flight profiles that are quoted. The higher aspect surfaces are of higher aspect ratio, and that in turn provides an improved lift-to-drag ratio on lifting surfaces. This is the only missile he can recall that has control surfaces extended out past the tail fins. The longer (and narrower) control surfaces would concentrate the dynamic loading such that the individual surfaces would have the center of pressure closer to the control hinge axis. This means the surfaces can be rotated with less torque than something like the AIM-7. As such, the control surface actuators would require less power to operate and would most likely respond faster while still maintaining sufficient force to affect the body rotation during maneuvering. He thinks the drawback of this design is that the wings would interfere with conventional launch rail systems, and would not fit into internal weapons bays. This may be why you don’t see a lot of this design; however, from an aerodynamic perspective, he thinks the long, narrower fins are more efficient both in reducing drag and in minimizing control torque requirement. OnlySlightlyCrazy: One of the leading factors in a missile's RMax is it's battery life - many missiles can aerodynamically hit targets much further than their battery can last out to. Thus, having more efficient control surfaces on a missile desiring long range makes sense. As to why the fins are midbody - that's the swappable nosecone bit that Colli shared. That image also explains the forward angle on the midbody fins; you want your fins to be as large as possible since they're midbody, and you want them as far forward as you can get them without intruding into the autopilot or Target Detection Device sections. Thus, having it swept forward means you get a wider fin farther forward, and get to not intrude into other necessary components. That forward sweep is frankly the only usual part of the fin - combining a forward sweep with a conventional fin geometry is what gets you the axe-body. I'm happy to take a crack at further questions myself, or forward them to said grognard before he retires and or dies.
  15. OnlySlightlyCrazy

    Bash the F-35 thred.

    An F-35B has crashed near Marine Corps Air Station Beaufort, South Carolina. Pilot safely ejected, no clue as to cause yet. Airframe appears to be a complete loss given the size of the smoke plume.
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