Pulsar Ballistics

jtg452 wrote:

TFLYTSNBN wrote:Well this is disappointing. Only 2,000 meters per second muzzle velocity from a pulsar pistol. Heck, the sabot rounds from an Abrahms tank is about 1,400 meters per second.

It is interesting as well as easy to estimate the average recoil force from a full auto Pulsar. They come in various calibers and projectile masses. Assume a projectile mass of about 23 grains or about 1.5 grams, a muzzle velocity of 2,000 meters per second, and a fitting rate of 600 rounds per minute or 10 rounds per second.

The mass flow rate is then 15 grams per second or .015 kg per second. Multiply by muzzle velocity of 2,000 meters per second and you get a recoil force of 30 Newtons. This is the equivalent of a 3 kilogram weight in a one gee gravity field.

Modern handgun ammunition rarely exceeds Mach 1.2 or 1.3 (14-1500fps), so a 4 fold increase in velocity would have a tremendous impact on any calculations.

On the other hand, RFC's pulsers are reliant on that velocity to do any sort of damage since the projectiles themselves are extremely light weight. Modern ammunition still has enough projectile weight that momentum retention has an impact on penetration. Mass (weight) retains momentum. Light weight bullets need higher velocities because they shed that momentum faster. A softball rolling on the ground can be stopped by putting your foot on it. Doing the same with a 4 pounder cannon ball leads to the loss of the foot.

Low velocity rounds as the 19th Century buffalo gun rounds (which had muzzle velocities equal to modern handgun rounds but were using bullets that weighed 4 times more) had such remarkable penetration abilities. Muzzle velocities of 12-1400fps were common- yet they were used to kill off the American bison to the point of extinction in little more than a decade.

Your own numbers quoted above put a pulser dart's weight at about 2/3 that of the most common .22LR bullet. At that weight, it had better have some serious velocity if it's going to have any sort of effectiveness down range.

TFTSNBN wrote:Projectile mass is important to achieve penetration, but it is the sectional density, not the mass, that combines with velocity to yield momentum density that dictates penetration.


Even at "only" 2,000 meters per second, those long, slender, Honorverse Pulsar darts have enough momentum density to penetrate a human torso from the top of the skull to the butt. In fact over penetration with minimal wounding from impacts at more normal aspects should be an issue. The only thing that makes these long, slender, hyper velocity pulsar days truly effective is the certainty that they will yaw upon impact. Weber mentions that pulsar days are son stabilized. I haven't calculated the skin rate needed to stabilize them, but it is extremely high. Imagine a 3mm x 25 mm dart yawing upon impact then tumbling at high rpm as it travels through a body like a buzz saw.

BTW, I'm one of the guys that writes the external ballistics programs that "gun experts" use to calculate trajectories as well as doing the internal ballistics calculations needed to determine what recipes are safe for hand reloading.

cthia wrote:Although true about a projectile's mass, that part of the equation can be skirted. Consider an advanced round that is engineered from futuristic materials or processes which is super light weight by comparison but considerably stronger than any conventional round and is engineered to be aerodynamic and resist losing impact energy because of round destruction. Most rounds that are found in a body sustain damage and are crumpled.

Jonathan_S wrote:

cthia wrote:Although true about a projectile's mass, that part of the equation can be skirted. Consider an advanced round that is engineered from futuristic materials or processes which is super light weight by comparison but considerably stronger than any conventional round and is engineered to be aerodynamic and resist losing impact energy because of round destruction. Most rounds that are found in a body sustain damage and are crumpled.

Though for shooting unarmored people round deformation within the body is a major mechanism of energy transfer and resisting over-penetration. Also why hollow point bullets cause wounds that are so much more severe than full metal jacket bullets; the hollow point is designed to deform (mushroom) and spread the bullet to maximize rate of energy transfer into the body.

So a projectile engineered to resist destruction or deformation is likely to do relatively well at penetration cover or armor, but against unarmored targets is likely to punch clean through and impart less damage than a projectile of similar velocity that does deform enough to stop within the body.

Though, if you can build a projectile to tumble within the target instead you can get similar terminal effect.
However it's probably hard to build one that will stay straight when hitting armor or cover, but tumble violently when hitting flesh.

cthia wrote:True, and thanks. I was simply pointing out the variable, in reference to armor-piercing rounds since that is important in the HV.

At the rate of fire, it wouldn't matter if a round goes clean though if there are many such holes leaking life sustaining bodily fluids. In fact, such a weapon would be more desirable against a massed attack like what the Stilthies offered up. One well placed round can conceivably take out two or more combatants. But definitely penetrate armor.

jtg452 wrote:

cthia wrote:True, and thanks. I was simply pointing out the variable, in reference to armor-piercing rounds since that is important in the HV.

At the rate of fire, it wouldn't matter if a round goes clean though if there are many such holes leaking life sustaining bodily fluids. In fact, such a weapon would be more desirable against a massed attack like what the Stilthies offered up. One well placed round can conceivably take out two or more combatants. But definitely penetrate armor.

Rate of fire doesn't have anything to do with individual round effectiveness. At the velocities stated, the mere passage of the projectile through the body will cause catastrophic secondary damage from the sudden energy transfer into the mostly fluid medium of a human body. (See the meteor-tsumani effect I mentioned a few pages back).

The primary wound channel (the hole of the projectile's passage) won't be big enough to 'leak'. The killer in the pulser's case is the secondary wound channel- the destroyed and damaged tissues adjacent to the primary wound channel.

Use a high enough cyclic rate and you can send multiple projectiles down range before the recoil impetus of the first round throws the muzzle off target.

That's part of the theory behind the use of a multi shot burst rather than full auto in the real world. In slower cyclic rate guns, after the 3rd shot, the rounds are tracking high and to one side of the other just from the accumulative effect of the repeated recoil impulses with no time to fully recover. Jack the cyclic high enough and you can get of 2 or 3 shots before the recoil of the first round can throw the muzzle off target from the initial aiming point.

Theemile wrote:

jtg452 wrote:That's part of the theory behind the use of a multi shot burst rather than full auto in the real world. In slower cyclic rate guns, after the 3rd shot, the rounds are tracking high and to one side of the other just from the accumulative effect of the repeated recoil impulses with no time to fully recover. Jack the cyclic high enough and you can get of 2 or 3 shots before the recoil of the first round can throw the muzzle off target from the initial aiming point.

That was the idea of the American 180 I mentioned upstream. The .22 Longrifle imparts almost no muzzle climb, and the high cyclic rate means that you just placed 20 rounds in a palm shaped area at 25 yards.

jtg452 wrote:Wasn't the G11 their caseless test bed, too?

The bullet stuck out of compacted mass of powder that looked like the Pyrodex Pellet that inspired RFC's ammo developments over in the Safehold universe and the gun used an electronic ignition system to fire the round.

Cool cutting edge concept- too bad the bonding used on the powder wasn't impervious to humidity and would break down and militaries already have a problem keeping batteries in the field for the plethora of things that run on them. I don't think that adding something like the primary infantry weapon to that list is a good idea. It's also much more susceptible to EMP because I don't remember reading or hearing that they ever fixed that issue with the G11. High tech is great- until it breaks and you end up facing someone armed with WWI or WWII battlefield pickups that kick your ass.