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  1. Upper Vortex Flap - A Versatile Surface For Highly Swept Wings While several types of leading edge devices exist for enhancing vortex lift at high angles of attack, the interesting thing about "upper vortex flaps" is that they also work well at low angles of attack. The CV variant of the X-32 had these inboard of its conventional leading edge slats to provide better low speed handling characteristics (e.g., lower AoA at approach and landing speeds) given it's initial pure delta configuration.
  2. Actually, it appears that that is the case in those two examples. I think the Borg Warner system IS described by the "incomplete" wiki figure, albeit laid out a bit differently (i.e., the balance shaft and idler gear perform the same function as the "steering input" bevel gears). The Borg Warner video is kind of confusing because it appears that the rotor of the TV motor rotates in the opposite direction of the "vectoring torque." As I understand it, the TV rotor drives a second, coaxial sun gear within the right wheel ring gear, the second sun gear driving a second carrier having planets that engage both a support member and the ring gear of the right wheel planetary gearbox. Accordingly, when the TV rotor spins CCW torque is vectored to the right wheel as depicted in the video by the CW "vectoring torque," and vice versa. The balance shaft and idler transfer and the reverse the direction of the "vectoring torque" with respect to the ring gear of the left wheel planetary gearbox. I think the clutch in the Borg Warner system is just there to improve efficiency when the propulsion motor isn't in use at all. That MUTE system is a fair bit more complicated, but it appears to work using the same, simple principle. I couldn't really tell what was going on in the YouTube video, but I did find this paper. Figure 5, reproduced below, has a diagram of a further evolution of the system depicted in the YouTube video, which seem to mostly differ in how the "superimposing electric machine" is integrated. In Figure 5, the left wheel is directly driven by the carrier in the spur gear differential, the carrier being driven by the planets depicted as hashed lines (I'll refer to these as the "primary left wheel planets") that interface with the ring gear, which driven the via the electric drive motor gear train. The spur gear differential planets represented by the solid lines (I'll call these the "primary right wheel planets") rotate with the carrier and in doing so drive the sun gear connected to the right wheel. The superimposing electric machine drives the interconnecting sun gear, and thus the primary left wheel planets and carrier) via the planets of the right-most carrier in the superimposing gear (I'll refer to these as the "secondary left wheel planets/carrier"). The planets of the left-most carrier in the superimposing gear (I'll refer to these as the "secondary right wheel planets/carrier") are connected to the secondary left wheel plants by an idling ring gear. Because (i) the primary left wheel planets only interface with the "interconnecting sun gear" and ring gear and (ii) the primary right wheel planets only interface with the right wheel sun gear (although both are carried by the carrier directly driving the left wheel), the right and left wheels can rotate at the same speed when driven by only the electric drive motor and at different speeds when torque is added/subtracted via the superimposing electric machine. Torque can be vectored to the left wheel and away from the right wheel by running the superimposing electric machine in a first direction and a vice versa by running in a second direction because the idling ring gear reverses the direction of the applied torque between the secondary left wheel planets/carrier and the secondary right wheel planets/carrier. I think/hope that makes sense. I think passenger vehicles like these systems seem to be designed for can get away with the fatigue loads that these systems will likely place on the drive shafts, as opposed to isolating wheels/sprockets via multiple differentials/clutches, because the duty cycle and loads are probably relatively light. Trying to turn a 20+ ton tracked vehicle is an entirely different proposition. I'm sure you could do it with beefy enough components, but I can see why adopting a bit more complex and sophisticated system would start to become appealing. Standby for a post and document dump covering split torque transmissions as applied to helicopters as soon as I can get around to writing it up. I think moving away from planetary reduction gear boxes could open up some interesting possibilities as far as helicopters, particularly compound helicopters, are concerned.
  3. I'm no expert, but according to wikipedia , this drawing is incomplete. Wikipedia says this is, " [a] Differential steering mechanism, either double-differential minus the clutches, or triple-differential minus the brakes. More specifically, I believe they mean a Maybach double differential with clutches to disconnect the "slowed" (i.e., not sped up) sprocket when steering torque is applied. Alternatively, the diagram could depict an "ordinary" double differential transmission, but the diagram's "epicyclic gears" are not correctly drawn as differentials, as in the transmissions depicted here or here. To depict a triple differential transmission, the steering torque is input into the steering half shafts via yet another, third differential (the diagram is missing a carrier having idler(s) between the steering half shafts) and brakes and/or clutches on the steering half shafts selectively engage and/or disengage to effect a steer. If you haven't already, you might want to revisit Coli's link. So, yes, you are correct in that the diagram does not include means for controlling the reactive torque applied to the drive input by the slowed sprocket when the steering input is driven. If the drive input and steering input were independently driven, you might be able to get away with that kind of set up for a while, maybe.... But the various multi-differential transmissions differ, more or less, in how to address the issues you have raised.
  4. It's actually being developed by a Québécois company, but close enough. That's the Mawashi Uprise exoskeleton. It was also discussed here at 3:42:30. I want me some "Ranger legs"! The whole episode is great.
  5. With these long-ogive, EPR-style bullets, how far does the shank of the penetrator extend relative to the cannelure? The steel penetrator and copper slug of M855A1 and M80A1 seem to mate up right at the cannelure for whatever reason. For M855A1 it appears that joint is slightly below the cannelure such that the neck of the cartridge reinforces that joint a bit, but it looks like that joint is slightly forward of the neck and cannelure for M80A1. Is there any sort of limit on how far forward of the neck that this joint can extend (e.g., to provide sufficient structural integrity)? Or is it just a matter of balancing the mass of the components that determines where that joint ends up?
  6. Hydrogen's energy density (about 10 MJ/L for liquid hydrogen) may be on the order of 2-4x better than the best batteries, but it's still pretty much crap compared to other gaseous and liquid fuels (diesel is about 35.8 MJ/L). And hydrogen comes with a side of severe storage headaches regardless of whether it is stored as a liquid or high pressure gas. If you have access to a power grid, water, and stuff that'll burn, and aren't that concerned with overall process efficiency, there are plenty of well-established ways of producing methanol, ethanol, methane, and various other synthetic fuels from those feed stocks. And if you count among your citizens a billionaire or two with plans to harness in-situ resource utilization for manned missions to Mars, perhaps they can figure out how to fit a synthetic methane plant (22.2 MJ/L) into a handful of shipping containers. Methanol (15.6 MJ/L) does a little worse than methane in terms of energy density but is also relatively simple to produce and, conveniently, is a liquid at room temperature that can be blended with other liquid fuels to stretch their supply. In something as volume-constrained as an AFV, as opposed to something that is more mass-constrained (like a rocket), hydrogen is a particularly poor choice. Hydrogen, however, is also a fantastic cryogenic coolant. Railgun augmenting coils and coilgun drive coils happen to like cryogenic coolants because they reduce resistive losses and/or raise the critical current and critical fields of any superconducting materials used therein. The general rule of thumb, even for HTS materials, is that useful operating temperatures max out at about 1/2 the critical temperature, except for very low field/current applications. Accordingly, liquid hydrogen at 20-ish K and supercritical hydrogen at 33-ish K are attractive coolants for HTS materials. A good setup might be to use a first stage liquid or supercritical helium cryocooler to cool the coils directly and to use cryogenic hydrogen as fuel and as a cryogenic heatsink for the first stage helium cryocooler. In any event, you're still probably talking about some sort of 120+ ton, 60 foot articulated MBT monstrosity or the worlds most expensive 120mm mortar carrier.
  7. Which seems to be exactly what BAE is doing with their "Dispensing" charge. There's barely any room for explosives anyway Things might get more interesting with larger bore rail and coil guns due to the scaling factors of the various components. This paper contemplates a 12" coilgun firing projectiles 155mm in diameter, excluding the fixed control fins. The guidance package volume fraction isn't nearly so bad.
  8. As a platoon commander, would rather have to ask company command for those attachments or ask company HQ to look after your CGs and GPMGs while you're rifle squads are on some sort of ninja mission? I'm not saying that the platoon would be 60 guys forever and always. CG rounds weight 6+ pounds each. Your'e going to need several bodies to lug a useful number around. While we're at it, why not distribute the load of a GPMG team amongst 5 guys instead of 3 and give them a DMR? Assaulting a small hamlet (e.g., 2-4 structures) after maneuvering on foot through restrictive terrain? Those 60 guys could give you two GPMGs on tripods in a support by fire position, two 15-man assault squads with 2 fireteams and a CG each, (i.e., two 15-man squads) and a 10-man squad in reserve. Battalion 81/120s or Brigade 105/155s drop smoke during the initial assault. The CGs accompanying the assault squad take out any fortified positions that could not be observed during initial reconnaissance or lay smoke if the respective assault squad needs to make a hasty retreat. IDK, I'm just an interested amateur. My interest is mostly motivated by figuring out how we might best incorporate the CGs that seem like a much better solution than whatever the current flavor of interim XYZ is that DOD wants to foist on the "light" infantry to achieve "overmatch." Additionally, I'm trying to think of ways to keep combat loads under 60 pounds or so.
  9. Fair enough, but a USMC platoon with the 13-man squads is already at 43 men. My 60-man platoon gains 17 men because of a slightly larger platoon HQ and two 5-man CG teams. Is it better to expect a 12/13-man squad to lug around a CG in addition to everything else or expect a platoon commander to employ a couple of dedicate CG/mortar teams? I arrived at the "super-platoon" solution in order to incorporate a couple of CGs without overloading the squads. And if, for example, it make sense to delete the two drone operators or one drone operator and one medic from the platoon HQ and add an assistant platoon commander to give that 22 year-old a bit of experience in the assistant role, , and maybe add a platoon staff sergeant, I'd have no objection. Precisely, so is the 60-man platoon I laid out above a super-platoon or miniaturized company?
  10. I think you're overstating the difficulty of storing a handful of extra weapons systems in a COP or gun truck and understating the difficulty of "simply" adding the manpower (and the logistics that come with it) of a weapons platoon to the company. Moreover, a weapons platoon might train together, and they might move together, but they're hardly ever going to fight together because every squad leader is going to be clamoring for support from a GPMG, CG, or mortar team. To keep the company at around 200 men, my company would have three 60-men platoons and a HQ but no weapons platoon. The weapons platoon is essentially distributed amongst the maneuver platoons. I think that has a few advantages. First, company HQ doesn't need to constantly make decisions as to which requests for weapons platoon assets get approved and which don't. Second, each platoon leader has an all-arms, all-effects combat team that should let him steamroll enemy squads, even if they're dug in. Third, I think my the maneuver squads would have a chance to develop better teamwork with the GPMG team and CG/mortar team that'll be supporting them. It's not as if they must be trained on the additional weapons systems. It's also possible that one grenadier might be certified on the CG and the other might be certified on the commando mortar (likewise wrt the gunner and assistant gunner on the CG/Mortar team). I view giving the Joes/Grunts a couple more goals to work towards as being an advantage. This stuff is small potatoes compared to requirements for artillery shells, fuel, and water. It might be a challenge to provide all of hit, but hardly insurmountable.
  11. In this scenario, is there any meaningful difference between a 12/13-man USMC squad with one SAW-equipped fire team and a 9-man Army squad with an attached 3-man MG team? The only one I can think of is that the USMC platoon commander knows that that the de facto MG teams are “his” and not toys that the company commander is passing around. IMHO, instituting a more flexible platoon organization and arms room concept would address these deficiencies way better than merely throwing gear at the squads. If I were SecDef Mattis for a day, I'd change the TO&Es such that the infantry platoons, Army and USMC, include at least a couple 5-man MG teams and at least a couple 5-man CG/Mortar teams. I like 5-man building blocks because they make it easier to go all Generation Kill and have each squad roll around the AO in a couple of humvees or together in a single 10 + 2 APC. My notional 60-man infantry platoon that might look something like this: (3) x 10-man Infantry squads including: (1) x squad leader (1) x assistant squad leader (4) x riflemen (2) x grenadiers (2) x assault gunners (2) x 5-man MG Teams including: (1) x team leader (1) x machine gunner (1) x assistant gunner (1) x ammo bearer (1) x marksman/spotter (2) x 5-man CG/Mortar Teams including: (1) x team leader (1) x CG/Mortar gunner (1) x assistant gunner (1) x ammo bearer (1) x marksman/spotter (1) x 10-man Platoon Command Section (1) x platoon commander (1) x platoon sergeant (2) x RTOs (2) x drone operators (2) x medics (2) x runners/drivers I’d give the platoon commanders and/or squad leaders a good bit of flexibility to decide how they want to organize their squads at the fireteam level. In close terrain (e.g., urban environments), they could organize each squad into two balanced 5-man fireteams with the squad leader leading one fireteam and the assistant leading the other fireteam (team leaders might be designated on an ad-hoc basis or based on experience). In more open terrain (e.g., Afghanistan), they could organize into a 5-man fireteam including both assault gunners and another 5-man fireteam including both grenadiers. The “arms room” concept would be desirable because the assault gunners and grenadiers could be equipped differently in each scenario. In the balanced fireteam scenario, each assault gunner could carry something like a Knight’s LAMG or M27 IAR and each grenadier could carry M320s on their hips. In open terrain, the assault gunners could draw a GPMG from the armory, with one assault gunner acting as the assistant gunner, and the grenadiers could similarly draw a CG or 60mm mortar from the armory. I figure the GPMG would probably be used as an LMG on a bipod and the 60mm as a “commando" mortar. On top of flexibility at the fireteam level, the platoon commander would also know that he can count on having at least a couple of MG teams and a couple CG teams to play with. Like the grenadiers, I’d give the CG teams the option of drawing CGs or 60mm mortars from the armory but employing the 60s off the tripods were possible. I'd put a couple of gunnery sergeants at company level to oversee training of the MG and CG/Mortar teams, essentially acting as respective MG and CG/Mortar platoon leaders on training evolutions.
  12. And the article completely glosses over unpowered exoskeletons. Based on the paper below, it seems like there are plenty of challenges in designing a good unpowered exoskeleton, but it is encouraging that the weight and inertia of a 11.7 kg passive exoskeleton only increases the "metabolic cost of transport (COT)" by 5%. http://biomech.media.mit.edu/wp-content/uploads/sites/3/2013/07/Walsh-2007_A-QUASI-PASSIVE-LEG-EXOSKELETON-FOR-LOAD-CARRYING-AUGMENTATION.pdf "Metabolic data show that the zero-impedance exoskeleton increases metabolic COT by 23% compared to the loaded backpack, and 12% compared to the quasi-passive exoskeleton, highlighting the benefits of spring and variable-damping mechanisms at the ankle, knee and hip. Finally, the added-mass condition increases the COT by only 5% compared to the standard loaded backpack, suggesting that added mass alone cannot explain the 10% COT increase caused by the quasi-passive exoskeleton." "One might expect that the added mass and inertia itself might fully explain the COT increase of the quasi-passive system. However, as noted in the results (Sec. 7), the added-mass condition only increases the COT by 5% compared to the loaded backpack. What might be the cause for the 18% difference between the zero-impedance exoskeletal COT and the added mass COT? Since the joint springs are removed in the zero-impedance case, the increase in COT cannot be attributed to a destabilization of the wearer’s walking pattern due to the release of stored elastic energy. Further, since active knee damping is not utilized on the zero-impedance exoskeleton and friction in the joints is minimized by the use of high-quality bearings, energy losses at the joints of the exoskeleton likely do not substantially contribute to the 18% increase in COT. We therefore conclude that the dominant causes for the observed COT increase are added mass and kinematic constraints imposed on the wearer." "More likely is that the exoskeleton applies kinematic constraints on the human wearer due to poor collocation of the joints and/or a restrictive interface between the exoskeleton and operator, forcing an unnatural, inefficient movement pattern. It has been shown that changes in natural gait increase the physiological energy expended during locomotion." Mawashi seems to be developing a much more advanced exoskeleton, at least in terms of ergonomics. It would be interesting to see what a collaboration with Bionic Power could yield with respect to an exoskeleton that is quasi-passive/energy-harvesting.
  13. Report to Congress on Navy Laser, Railgun and Hypervelocity Projectiles
  14. Thank you, Sturgeon, for your wonderful TFB article today. Like you, I've come to view light infantry as a primarily weight-constrained force. In general, trading firepower for lighter weight is advantageous with respect to the currently over-burdened U.S. infantryman. As you acknowledge in the article, generating suppressive fires via DMR rather than LMG is a weight-efficient means of achieving a suppressive effect in many of circumstances. I, however, do not believe that a belt-fed weapon is necessarily a dead end in the AR/DM role within the squad. There is at least one belt-fed weapon that can achieve very good accuracy: the HK21. The HK21, of course, achieves this by having much more in common with a battle rifle than a traditional LMG or GPMG, namely the closed bolt operating system, hammer, and fixed, top-mounted scope mount of the G3 from which it is derived. While the roller-delayed operating system may itself be a dead end, the HK21 provides a template that could inform future designs in that a belt-fed weapon can retain many of the advantages a traditional magazine-fed weapon if the magazine well is merely replaced by a belt-feed mechanism. The downside is that reloading the HK21 is arguably even slower and more cumbersome than a traditional LMG/GPMG. In the tear-down portion of that video, Mr. Vickers notes that one work around is use a starter tab. I, for one, would not want to be fumbling around trying to find the starter tab when my fine motor skills go out the window as rounds are impacting around me, so reloading without ANY belt handling is desirable. While H&K tried to develop a linkless feed system for the HK21, it didn't go anywhere. I'm dubious that a linkless feed system could be made light enough and sufficiently reliable for infantry use. If one goal of a future M249 replacement is that it share ammo with squads ARs, I agree that something along the lines of the M27 makes a lot of sense. I also believe that a GPC is a dead end, and that a two-caliber system for the infantry is probably the way to go. Ideally, my proposal is that the military replace 5.56x45mm with a cartridge optimized for a vld-epr bullet in the 50-77 grain range (i.e., an optimized SCHV round) and replace 7.62x51mm with a cartridge optimized for a vld-epr bullet in the 90-120 grain range, all concepts that I believe Sturgeon, among others, has touched on over the years. Ideally a composite case having a traditional extractor groove would be used. To summarize Sturgeon's work, the 7.62 replacement is, in essence, a composite-cased .264 USA (or possibly closer to 6.5mm Creedmoor) firing a 6.5mm vld-epr bullet. Let's call it a medium caliber, high velocity (MCHV) round. While I do not advocate equipping all members of the squad with a MCHV weapon, I do believe that having one or two MCHV DMRs within the squad would be desirable and that replacing the M249s with these makes the most sense. From a logistics point of view, it would be desirable to distribute all SCHV rounds in magazines and all MCHV rounds in belts, other than perhaps accurized MCHV loadings. For this reason, I think it would be worthwhile to investigate a conceptual successor to the HK21 as a SAW/DMR. One change that I advocate is moving to a gas-operated system with a fixed barrel, preferably a LW-profile barrel with a carbon fiber overwrap to increase rigidity, surface area, and thermal conductivity. The SCAR 17 with a lengthened upper receiver to accommodate a constant-recoil system might be a good starting point. The grunts would primarily use the weapon in semi-auto, but a limited full-auto capability would be available for engaging maneuvering infantry at a distance and in close ambushes. Reloading would still be an issue. This is where we borrow from the best SAW that never was, the XM248. The XM248, among its many innovations, used a cam-driven sprocket to advance the belt. While WeaponsMan unfortunately passed away recently, his great discussion of the feed mechanism lives on. While the XM248 promised belt-handling-free reloading, the ammo boxes did have potentially fragile exposed "plastic grippers" that held the first round in the feed position. Additionally, there is the potential for misalignment of the belt and feed sprocket during reloading. While, I don't consider these to be deal breakers, we might do better in terms of reliability by integrating the feed sprocket with the ammo box. The ammo box would hold a round in the feed position via an anti-backup pawl, as in the XM248 design. While carrying around a feed sprocket in each "magazine" would add weight, I doubt there would be any penalty in terms of weight or bulk versus drum magazines, and it would enable truly care-free reloading. I imagine they'd actually be significantly less bulky than drum magazines and no heavier, if not slightly lighter, if a plastic belt is used. I propose 60-75 round drums as being standard. A backup, loose-belt adapter could be carried and inserted into the "magwell" if only loose belts for the GPMGs were available. The cam assembly, however, does prevent the use of a traditional hammer and trigger mechanism. We might get around this by using a linear hammer, as in the QBZ-97, or use the slightly more complicated cam system of the HK21. What do y'all think?
  15. Sturgeon's SAW post on TFB got me thinking about the XM248 and an idea of mine. Here are a few relevant XM248 documents and links. Somebody needs to find one and give Ian a call. Ford Aerospace XM248 Technical Manual XM235 '461 Patent XM235 '074 Patent Weaponsman Links: XM235: http://weaponsman.com/?p=11494 XM248 - Part 1: http://weaponsman.com/?p=11558 XM248 - Part 2: http://weaponsman.com/?p=11661
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