Kinetic guns and point defense

The guns

• Every gun in known space is kinetic, which means it fires a solid round.
• A postwar treaty outlawed guided missiles and warheads.
• A COILGUN aims true. An AUTOCANNON hits hard up close. A RAILGUN punches through armor.
• A CANISTER fires a shell that opens into a cloud of pellets.
• A round hits harder when it closes faster, because its energy grows with the square of its speed.
• Past 3 km/s a round melts on impact, so plate weight stops it more than hardness does.
• Steel stops a RAILGUN best, and ceramic an AUTOCANNON.

Turrets and the keel gun

• A HARDPOINT is a mount a gun bolts into, and it decides what the gun can shoot at.
• A TURRET traverses, so it fires in almost any direction.
• A KEEL GUN is bolted along the hull's axis, so it fires only near where the bow points.
• It is the biggest gun aboard, and no hull carries two.
• The helm lays the bow for it by the KEEL GUN standing order.
• The drive pushes along the bow, so a bow laid on a hostile cannot burn away or weave.

Canister

• A canister shell opens on a fuze into a cloud as wide as the target could dodge.
• A slug at a dodging hull usually misses, but lands whole when it hits.
• A cloud nearly always lands some pellets, so its damage is steady but smaller.
• Too far out, no pellet meets the hull.
• Each point defense mount engages 2 rounds a second, so a cloud swamps it.
• Armor stops most pellets.

Drones

• A strike drone hits one system past the armor, and never the hull.
• [7] | launch one, or a salvo from every ready rack.
• Send it at the heaviest gun, the point defense, or the nearest system.
• Each launch spends a drone. It reaches 300 km at most.
• An operator steers 1 drone at a time as a rookie, 2 seasoned, 4 as a veteran.
• An unsteered drone flies its launch line, so a dodge can beat it.
• Point defense can stop any drone inside 40 km.
• DRONE RULE | what the operator launches without asking.

Each value is read from the game code. Sort by any column heading, or filter by grade or by a word.

• A round that hits at 3 km/s carries energy equal to its own mass in TNT.
• Energy grows with the square of speed, so a round at 6 km/s carries four times as much.
• A railgun tops out near 6 km/s, and the rails wear with every shot. A coilgun does not rub the bore, so it avoids that wear.
• A cartridge gun throws its case away, and the case carries the waste heat of the shot.
• A kinetic shotgun hits more often than a single slug but does less to what it hits, and the mirror says buckshot could puncture radiator tubes.
• A bullet defense must hit a fast target, so its hit chance depends on the target's apparent speed.
• A wave of targets can use up the time a defense has, so point defense can be saturated.
• A seeker is a computer in a round, and its range depends on the power the target ship radiates.

• The railgun muzzle speed of 6 km/s is the mirror's figure. The coilgun's 4 km/s and the autocannon's 1.5 km/s are authored to keep the order of ranges between mechanisms. The mirror puts the practical limit of a chemical gun near 1,750 m/s (the Rheinmetall L/55), so the autocannon sits close to that limit (spacegunconvent.php.html).
• The launcher energy budgets are authored so that a Light mount keeps the full rail speed. They cap speed by the rule v = sqrt(2E / m).
• Damage scales with the square of closing speed, as the First Law says. Penetration scales with the two-thirds power, which a comment in the game calls the game's own reading of the page and not a figure the page states.
• A canister fires one shell that carries many pellets, and a fuze opens the cloud as wide as the target could dodge. The game does this so one shell is one round for the locker, the price and the sound.
• Point defense in the game is a cartridge gun, because every gun in this world is kinetic. The mirror's point defense discussion is mostly about lasers and missiles.
• Drones carry no seeker, because the Safeguards compact bans guidance that steers itself. The mirror treats seekers as normal and only limits their range.
• Recoil, rail wear and radio lag are simplified. Recoil is not modeled because a railgun shot moves a 6,000 t hull about 0.02 m/s. Rail wear is modeled by mount size with authored numbers. Radio lag to a drone at 300 km is about a millisecond (the arithmetic here, distance over the speed of light) and is ignored.
• The keel gun's lay cone is bracketed by the mirror: a NERVA engine pivots up to 3 degrees and thrust vectoring stops at about 10 degrees (rocket/controldeck.php.html). The steps between sizes are authored.

1. Atomic Rockets does not provide values for the following:
   1. Canister figures. Pellets a shell, the fuze rule, and the cloud width are authored.
   2. Rate, window, or odds of kinetic point defense in a ship fight. 2 rounds a second and a 5 second window are authored.
   3. Kill vehicle figures. Every drone value is authored.
   4. Turn rate of a heavy or railgun mount. A code comment gives 30 to 115 deg/s for real mounts.

• Phalanx CIWS and the GAU-8 cannon (real system): a cartridge gun fires in short bursts to spare its barrel
• US Navy electromagnetic railgun (real system): rail erosion as the critical weakness, so rails wear and are replaced

• Atomic Rockets, spacegunconvent, Equations (Robinson's First Law of Space Combat): Robinson's First Law: a round hitting at 3 km/s delivers energy equal to its mass in TNT. The figure scales with the square of speed, so a round at 6 km/s has 4 times as much. "kinetic energy equal to its own mass in TNT" (all uses)
• Atomic Rockets, spacegunconvent, Equations (hypervelocity impact): At or above 3 km/s kinetic energy dominates over momentum, and impacts resemble explosions. The shape of the projectile still changes the result. (all uses)
• Atomic Rockets, spacegunconvent, Railguns: The maximum speed of a railgun projectile is about six kilometers a second. (all uses)
• Atomic Rockets, spacegunconvent, Coilgun (Ferromagnetic projectiles): A coilgun pulls its projectile along the middle of the coils, so no bore friction occurs and it avoids the wear and speed limit that touching rails cause. Railguns suffer severe rail erosion. (all uses)
• Atomic Rockets, spacegunconvent, Kinetic Kill Weapons: Cannons, coilguns and railguns all recoil because of Newton's third law. A mass driver is a coilgun tuned as a propulsion system. (all uses)
• Atomic Rockets, spacegunconvent, Equations (Combustion Light Gas Gun and ETC guns): A light gas gun reached 2.5 km/s in a Navy model, and about 3 km/s is the practical limit. Adding electric heat might push a chemical gun to between 3 and 4 km/s. (all uses)
• Atomic Rockets, spacegunconvent, Equations (seekers): The author finds that seeker ranges may be shorter than the ranges assumed for kinetic projectiles. A small rocket fired when a projectile is a few seconds out adds only minor problems for the defense, because anything passing close to a ship is treated as a threat. (all uses)
• Atomic Rockets, spacegunintro, Introduction: Ken Burnside compares a kinetic weapon to a shotgun. Holger Bjerre replies that a kinetic round is less likely to hit because it can be dodged. "more likely to hit, but with reduced lethality" (all uses)
• Atomic Rockets, sidearmintro, Which Gun Is Better?: A slug thrower ejects its case and so gets rid of the waste heat of firing. It also recoils, and it needs ammunition boxes to reload. (all uses)
• Atomic Rockets, spacegunconvent2, Equations (kinetic particle attacks, in the laser cannon section): Heavier particles like ball bearings or buckshot could puncture radiator tubes and let the coolant leak. The author says their effect is unknown, and that a particle big enough to track alone can be burned out by a laser. (all uses)
• Atomic Rockets, spacewardefense, Kinetic PD: Eric Rozier's model of a Phalanx-style gun simulates every bullet. The hit chance depends on the target's apparent speed (muzzle speed plus target speed) and its ability to accelerate. Linking several guns does not simply multiply the odds. (all uses)
• Atomic Rockets, spacewardefense, Laser vs. Missile: The missile side holds that point defense can always be saturated: fire enough missiles, fast enough, and there are more targets than the defense can hit before impact. The laser side disagrees. (all uses)
• Atomic Rockets, spacewardefense, Armor: A Whipple shield (a spaced bumper) is very effective against hypervelocity weapons. Above 10 km/s closing speed armor matters less than blow-through. (all uses)
• Design notes: setting-canon, 2. Safeguards: Safeguards bans the seeker: a guidance package that steers itself is computing with a weapons path. A drone steered by radio has a person in the loop, so it is legal, which is why a drone rack needs an operator aboard. (all uses)