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My write up on the Traveller world of Egurgadi, a high tech world of on the edge of the Imperium which is mostly a ship yard and university. The world itself is home to alien marine sophonts who take no interest in the affairs of humaniti.
https://blog.notasnark.net/2021/05/egurgadi.html
#travellerrpg #worldbuilding

Egurgadi
 
Okay, so I've decided to actually work on a Space Carrier VARUHARA board game system, even if only to help me study tactics and strategy for the story.

I'm adapting my ideas to line drawing, because that lets me keep a record I can refer to and refine.

That means drawing lines on millimeter graph paper; each map consists of multiple 8.5x11 sheets (with margins, since printers don't print edge-to-edge). So each sheet is just 20x25cm.

Scale is designed for Earth out to GEO, or a bit more than 80,000km across. At a scale of 1cm:1000km, that's about 80x80, or 5x5 sheets (100,000km x 125,000km).

SCALE = 1cm to 1000km

SHEET = 20cm x 25cm

MAP = 5x5 sheets (100,000km x 125,000km); without corners this is 21 sheets

Earth is the center sheet, consuming about 64% of the width. The area within Earth's circle is optionally used for orbit inclination tracking, for true 3D movement.

Earth is surrounded by rings indicating gravity strength.

The use of millimeter graph paper enables really good precision - down to a fraction of a millimeter, or less than 100km.

An intercept is registered if two line segments cross (and optional inclination indicates close enough Z match). This is a bit of a fudge, but I think it's close enough for my purposes.

However, to achieve greater precision I use a "Tangent Vector Movement System". A ship's position is implicitly defined by a tangent between a PAST dot and a FUTURE dot. The line segment between these dots is tangent to the ship's true position and path.

The way it works is that time is broken into "measures", and the dots are projections of the ship's tangent into the PAST and FUTURE times, on measure breaks. Each measure is broken down into four quarters.

MEASURE = 4000 seconds (about 1 hour)
QUARTER = 1000 seconds (about 17 minutes)

Using this tangent system makes it easier to visualize future positions, and reduces how much work is needed because units orbit without thrusting most of the time.

The actual position of a ship is implicitly designated by a point along this tangent. For example, on quarter 2, the ship is at the midpoint of the tangent. But you don't actually draw this point if you don't want to.

More thoughts later ...

#gizmo #worldbuilding #SpaceCombat #SpaceTechnology #SpaceCarrierValhalla
 
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Space Carrier VARUHARA notes - Stealth tactics in space


I've redesigned the spacecraft in Space Carrier VARUHARA to emphasize stealth.

The Valhalla is a late war carrier designed for rapid production at the expense of redundant systems and flexibility.

STEALTH DESIGN

Valhalla's angular shape assists radar/lidar steatlh.

The short side is the main sunshade; it's mirrored to reflect sunlight into a narrow cone. Most of the time, the ship hides in the shadow of this sunshade.

The long side is also a mirrored sunshade. This allows aiming the catapult when needed.

The other sides are black, to eliminate reflections of moonlight/planetlight.

All sides are cooled by liquid helium or liquid hydrogen. Liquid hydrogen is used in interplanetary space because it has much better heat of vaporization, but liquid helium is used when it's necessary to "bottle up".

The main thrusters are hidden within tunnels, so they are only visible in a narrow cone. They use pulsed operation to increase expansion ratio so the exhaust is cold. The propellants used are:

1) (Molecular) hydrogen - this is the main propellant used, heated by fission reactor. Hydrogen is hard for enemy sensors to detect, but easier than helium. Specific impulse is 850s.

2) helium - this propellant is used when extra stealth is needed. It is also heated by fission reactor. Specific impulse is 600s.

3) LH2/lox - Hydrolox is used in situations where relaxed stealth is practical, because LH2 consumption is halved and LOX is a conveniently dense fuel. In particular, it's used for the main transfer burns at planetary periapsis. The exhaust is normally very visible because ice particles reflect sunlight. But this isn't a problem when thrusting in the night shadow of a planet/moon. Specific impulse is 450s.

STEALTH TACTICS

When in orbit in contested space, the ship "bottles up" during most of the orbit. This means cooling the outer surfaces with helium, and melting ice to absorb internally generated heat. If helium supply is low, hydrogen is used instead - although this makes the ship warm enough to see with helium cooled sensors.

At periapsis, the ship refreezes the ice with liquid hydrogen. This hydrogen will be difficult to see against the background of the much warmer planet.

At all times, the boiled off helium and hydrogen will be run through the reactor before being expelled out of a main thruster. You might as well get some maneuvering thrust out of it, to hopefully throw off enemy predictive tracking. Even when the reactor is shut off, the core will remain hot.

Even though most military spacecraft have similar stealth abilities, a completely unseen approach is rare. The occasional detection by sunlight beam or star occultation is enough to provide a rough idea of where enemies are located - but this data isn't frequent or precise enough to provide a firing solution. Pre-war theory was "there is no stealth in space", meaning that an approaching attacker will always be detected and always be tracked well enough for lasers to prevail. Long range stealth missiles destroyed many laser battleships until crews changed tactics to emphasize stealth. New warship builds tended to be missile bus carriers to save costs compared to laser battleships and to reduce minimum reactor waste heat generation.

The perception is that laser battleships were made obsolete by missile bus carriers, but in fact the case is not so clear cut. At the time of the war, stealth had an edge over sensors. But if sensors regain the edge, then high power beam weapons could regain the advantage.

SENSORS

Valhalla's main sensors are:

Helium cooled thermal telescopes. These can see anything that isn't itself helium cooled, although not against a planet/moon.

Optical cameras - occultation sensing. These stare at the background stars and detect the dimming or distinctive diffraction pattern of a passing object. This can see anything, but at limited range and can't track.

Optical cameras - sunlight/thruster sensing. The cameras may also get lucky seeing reflected sunlight or a thruster. In this case, the detection may last long enough to get a rough heading.

Scanning Electron Beam/Telescope. Shine an electron beam onto a target; observe with a telescope. This can see anything at short range, including against a planet background. Electron beam telescope is particularly useful for stealth spacecraft because they are deflected by ambient magnetic fields. As such, the target has a much less precise idea of where the beam is coming from. In contrast, radar and lidar give the target a precise angular location and thus a precise direction to point tracking sensors back.

Neutron beam. The neutron beam is a weapon, but it can also be used to find out stuff about enemy targets. In particular, they can be used to distinguish decoys and detect nuclear warheads and materials.

Valhalla lacks radar, depending entirely on fighters/drones for radar sensing. Most military spacecraft have radar stealth, so this limitation is accepted.

WEAPONS

Valhalla's main weapons are:

Valhund fighters. Valhalla can catapult a Valhund up to 250m/s in 5s; it can slow down incoming fighters with a volley of reusable bullets. Each Valhund is armed with a hydrogen/hydrolox gas gun that launches small triple missile burgers. Hydrogen is used for low muzzle velocity; hydrolox is used for high muzzle velocity at the expense of stealth. Each missle burger can immediately split up into three short range missiles, or it can act as a single two stage missile. The "buns" act as the first stage, but retain a small amount of fuel so they can act as orbital "space mines". The "meat" acts as the second stage.

Hydrogen gas gun. Valhalla has a gas gun which can shoot reusable bullets at an extremely high rate. It's optimized for use in fighter braking, and mounted near the reactor. However, it can be used as a short range weapon.

Neutron beam. Neutron beams were developed just before the war, using plasma wakefield acceleration within a solenoid magnetic field. The solenoid means that the ambient electrons rushing into the plasma wake "miss" the exact center of the beamline and form a strong magnetic field at the beamline. This moving magnetic field accelerates the neutrons (which have a magnetic moment). Neutron beams are not very efficient, so few countries anticipated their importance in the war. But they would be able to disable nuclear warheads and cause most guidance electronics to fail.

Valhalla lacks electron beam armament. The neutron beam is powered by an electron accelerator parallel to the catapult, but this electron beam has too much self repulsion to be a practical weapon. It does, however, use the electron beam in a low power mode for the scanning electron beam telescope.

Valhalla lacks laser armament. Pre-war warships typically had heavy laser armament, but this required them to use large hot radiators and/or large solar arrays. Either way, they were highly visible and the advances in stealth missiles made them too vulnerable. Late war warships would typically have much smaller reactors insufficiently powerful for heavy lasers.

Valhalla lacks missile launchers; it depends entirely on its fighter wing to launch missiles.

DEFENSE

Obviously, the main defense is stealth - avoid detection, and try and throw off tracking. But there's also Whipple shielding - 3 layers of metal sheet to defend against random space debris and small bullets/fragments. Additionally, burger missiles are used to shoot incoming missiles (Valhalla lacks missile launchers, but at least one Valhund should normally be nearby defending the ship.) The neutron beam has limited effectiveness against late war missiles, but the ability to neutralize nuclear warheads alone justifies its continued use. The gas gun is not really an effective weapon, with a low muzzle velocity and light unguided bullets. But it's better than nothing as a last ditch defense.

LOGISTICS

Apparently this isn't obvious to everyone, but it's actually really easy to dock and receive supplies from supply ships in space. Here on Earth's ocean, ships can't just dock with each other due to the way the ocean moves. But in space, there's no ocean. So, Valhalla was not designed to carry a bunch of long term supplies on board. Stealth supply drone ships are bigger, and are shaped like square base obelisks. Despite being larger, supply drones are less expensive than warships.

Even less expensive are civilian supply ships and stations. Usually Valhalla breaks stealth to directly receive supplies from civilian ships, relying upon stealthy hydrogen propulsion later on to throw off tracking. It's also possible to tug cargo containers and tanks with a Valhund fighter, using a large sun shield for some semblance of stealth carrying the containers/tanks to/from Valhalla. However, this is more time consuming and costly, so Valhalla doesn't bother. It's currently patrolling in the Jupiter system, where hydrogen fuel supplies are not so available (most spacecraft only pass through the Jupiter system for its gravity boost). So its operations heavily emphasize conserving hydrogen.

Valhalla's current patrol orbit passes by Callisto, given the crew a view of its namesake crater about twice a month. Before the war, Callisto had LH2 refineries, but these were destroyed in the war. Most of Callisto's current industry revolves around cheaper and more storable methane fuel, along with lox, water, and carbon dioxide. These supply civilian stations just fine, but neither Valhalla nor its Valhund space fighters can use methane fuel. In contrast, its Dauber scouts use pre-war modular booster packs. Methane-lox boosters aren't very stealthy, with water and CO2 ice particles in the exhaust. So, Dauber scouts from Valhalla try to only make mid-course return thrust maneuvers in the shadow of Jupiter or Callisto. (The initial catapult boost and gas gun braking are stealthy enough, but a mid-course maneuver is usually required to return back to the carrier.)

#gizmo #worldbuilding #SpaceCombat #SpaceTechnology #SpaceCarrierValhalla
 
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Dragon Hunting Notes: Sailback Dragons


As an aside, Sea Dragons exist in my dragon hunter setting. However, humans do not really hunt them, so whatever. They:

1) Have a body plan similar to an oarfish

2) Fly like nothing on our Earth, using their entire body as a flying wing

3) Use sidewinding to move on the ground

4) Swim like a snake or eel

Sailback dragons are legless reptiles. They were initially somewhat small, and developed stickle-back spines as a defense from constrictor snakes. These spines became a spiny neural sail from head to tail.

Forest sailbacks began to glide from tree to tree using their bodies for lift like flying snakes. However, flying snakes are flattened horizontally, while sailbacks are flattened vertically. This means sailbacks can fly, even though flying snakes can only glide. The natural snake-like undulating motion produces thrust like flapping wings.

Ironically, sailbacks did not last in forest environments. Their flying wing body plan may have been fine for wrapping around the nearest tree, but pterosaurs could nimbly maneuver between branches for longer flights. Pterosaurs and snakes muscled out sailbacks from forests.

Sailbacks moved to coasts and rivers, occupying mostly seabird niches. They were excellent divers and swimmers, much better than pterosaurs.

Sadly, the K-T event almost wiped out sailbacks. Birds flooded into their niches, leaving the remaining sailback survivors as evolutionary relics. By the time humans arose, a sailback dragon was a rare and spectacular sight.

It will be a long time before humans understand how sailbacks fly. They look like snakes magically suspended in the air; their undulating motion looks nothing like flapping wings. Foreign scientists will be skeptical of their existence. Even after dead bodies will force them to admit that these wingless dragons exist, they will long refuse to accept they can fly.

Actually, when viewed from directly below, the body wing is apparent, but most of the rare sightings would be from an angle where the undulating motion would be the most visible thing.

Regardless of foreign skepticism, natives celebrate sailback dragons as noble magical creatures. This contrasts with the (well earned) reputation of pteropod dragons as cruel and evil. Dragon hunters are skeptical of their existence, so obviously they have no interest in hunting sailbacks.

OTOH, sailors worldwide fear giant flightless sea serpents, which occupy the niche of our large toothed whales, such as sperm whales. In myths, these sea serpents are often regarded as related to pteropod dragons, but in fact they are only distantly related. Even though dragon hunters dismiss sea serpents as mere sea stories, most will go along with the myths if they can get a "free" ride for protecting a ship.

To get some idea of how this would look, see this video:



The drone in the video only waves incidentally, but that wave motion is how a sailback dragon would fly.

#gizmo #dragons #pterosaurs #RPG #WorldBuilding
 
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Dragon Hunting Notes: Pteropod Dragons


Here's my take on dragons for a dragon hunter setting. They:

1) Fly like pterosaurs

2) Run like tyrannosaurs

3) Have armor like crocodilians

4) Spread fire like firehawks

In this fantasy world, pterosaurs had scute armor because they evolved from crocodyliforms. Stronger winds, increased air density, and reduced gravity helped increase their max weight and size beyond Quetzalcoatlus.

Some pterosaurs survived their K-T event. These evolved from quadrupedal pterosaurs into bipedal "pteropods" ("wing feet"). The pteropods took over niches left behind by large theropods. Bipedalism let them get even bigger than before, thanks to running launch.

Pteropod arms are powerful, used for both flying and running. Their hind legs are almost vestigial, being used only to help shape the wings for maneuvers in flight, and help fold away the wings on the ground.

The "knees" are actually wrists. The "ankles" are actually finger roots. The "feet" are actually fingers, ending in hooves.

The stiff armor scutes are like an exoskeleton. This makes the body pretty stiff, but the neck can still bend well side-to-side so the pteropod can preen itself.

Different pteropods had different lifestyles. Some spent most of their time on the ground; some went flightless. These went extinct when their megafauna food sources were killed off by hominids. Others were vulture-like, but they shrank along with the food supply. The remaining giant pteropods are the "true" dragons - dragons that can "breathe" fire.

Dragons don't project fire like a flame thrower, but rather they hold burning brush/twigs in their beaks which they use to set other things on fire. They control the fire by exhaling through the mouth to fan the flames, or closing their beak to keep it from burning too hot.

Dragons strategically set fires, like firehawks, to flush out and trap herds. Then, they can slay the concentrated animals left and right on the ground, expending little effort for a lot of food. Thus,they don't depend on megafauna like their extinct relatives. (This strategy would have been too risky for flightless pteropods, but the "true" dragons can fly if needed to escape the fire.)

These dragons are very intelligent, as fire hunting requires a lot of intelligence to pull off. Some use flint to initiate fire on demand. Others use lava if available; others may maintain ongoing fires. In all cases, fire hunting only works in dry conditions with a herd in a position within suitable fuel. Dragons can rest in a reduced energy state to wait out wet conditions, and then soar to scan for a herd in a good position.

Ironically, hominids caused dragons to increase in size. Before hominids, dragons were mostly social pack hunters. But these smaller dragons were vulnerable to hominids with spears. The bigger solitary dragons were too tough for hominids to take on, and they got even bigger and tougher without food competition from the pack hunters.

These dragons are an utter terror for humans. Obviously livestock and humans are easy snacks, and this is a big problem when a dragon hasn't been able to fire hunt in a while. But also, dragons like to randomly set human stuff on fire just to see them scurrying around. This isn't just malice, it's an evolved play behavior to practice fire setting and study how fire propagates and corrals prey. However, the human victims just see a dragon taking sadistic pleasure in watching them suffer.

So, these dragons are tough, they're big, and they're cunning. And the humans have incentive to hunt and kill them ... if they can ...

#gizmo #dragons #pterosaurs #RPG #WorldBuilding
 
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