Ship Design Philosophy

[Condottiere]

Starships: 10 Features that made the VENATOR CLASS the BEST STAR DESTROYER in Star Wars

We continue our 10 Flaws series by looking at why the Republic Venator Class Star Destroyer was the best .

https://www.youtube.com/watch?v=GcB3Z9rG2v0

It's very relateable.

 

[Condottiere]

Spaceships: How Big Are The Ships of The Expanse?

As our Force Recon Scale Charts are now declassified, we can reveal the exact size of The Expanse's spacecraft!

https://www.youtube.com/watch?v=ERqBIsta_iE

 

[Condottiere]

Starships: Engineering, and Primitive and Advanced Capacitors

Force Field Generators project a spherical energy-absorbing shell around a ship, and are therefore known as block globe screens. All energy, whatever its form, that contacts the black globe is absorbed and diverted to the ship's capacitors, doing no damage.

The capacitors contained in the ship's jump drive may be used to store this energy; additional capacitors may also be purchased. The jump drive capacitors mass .5% of the ship's mass, per jump number; for example, a drive capable of jump-3 will include capacitors equal to 1.5% of the ship's mass. Additional capacitors may be purchased at MCr4.0 per ton. One ton of capacitors (in a jump drive or not) will hold 36 EPs.

That's Classic.

Damage points from attacks that strike the globe are absorbed by the globe's capacitors as hit points. The size of the capacitor bank is critical, as (he globe will discharge catastrophically when it overloads. Stored hit points may be drained and convened to energy and stored in other energy banks or used to power the ship's systems ... Maximum conversion rate is I% of capacity per second (240.000 HP or 960 MJ per dton per tum ... Ships that do not have separate energy banks may use their jump accumulators. Each jump-drive module includes accumulators capable of storing 24 GJ (or 6.000 HP). Black globes come with a rudimentary capacitor bank able to store 10.000 HP worth of energy.

That's GURPS; accumulators and capacitors are probably the same thing.

Capacitors are default technology level nine, and my or may not be zuchai crystals, they just happen to be exceptionally efficient at this, though brittly so, as they can't hold the charge more than two pr three hours without causing decomposition.

For the Mongoseverse, jump drive size reduction or increase are the only factors that effect capacitors, cost more of an issue if it's a budget or prototype model.

Since I'll assume that at default, budget option can only be used once, and production and prototype models are an either/or proposition, increasing the energy density is possible to upto thirty percent at technology level twelve at a fifty percent premium, economizing it knocks off twenty five percent from the cost, but increases the size required for that capacity by twenty five percent

Other advantages and disadvantages touch on other aspects of jump drive technology and control.

As the energy of attacks absorbed by the generator is channelled to capacitors, a ship must have sufficient capacitor capacity if it is to avoid overloading its systems and explode catastrophically. Fortunately, if a ship possesses a jump drive, it will have considerable capacitor capacity.

A jump drive will have capacitors equal to twenty percent of its size in tonnes. Additional capacitors may be purchased at a cost of three megacredits per tonne.

Each tonne of capacitor will absorb fifty points of damage.

So that's a possible seventy one and a halfish at technology level twelve.

If a ship with a black globe generator absorbs more damage than its capacitors can handle, the ship automatically explodes, destroyed instantly.

To avoid this, the capacitors can be discharged. For every combat round the black globe generator is switched off, the capacitors will discharge an amount of damage equal to one percent of the ship’s total tonnage multiplied by ten percent of the tonnage of the ship’s power plant.

Probably has to be rethought, since power plant output can and does vary.

 

[Condottiere]

Starships: Venture Class Jump Drive

Still tinkering with it, but having examined Advanced Micro Devices new chiplet design has somewhat inspired me (also, may force me to upgrade before I anticipated since it's rumoured they'll substitute eight core chiplets for the current four core modules).

My intent has always been to design the cheapest, smallest jump drive.

I've managed to separate the most expensive component, the capacitors, from the five tonne overhead. It should be noted that as long as the interface with the jump drive core remain in the same place, capacitorless overheads should be compatible with jump drives constructed at the same technology level, or less, since you have to take into account parsec range, as the jump governor is part of the overhead.

As it would be the budget variant, that would be five tonnes volume, costing 3.375 megacredits.

That leaves another five tonnes to fill out with the core and enough capacitors, which is more parsec tonnage than I actually want, enough for a single jump for the minimum tonnage.

So the question was if I could use an advanced shrink and still stuff in cheaper older technology.

The rules are clear that thirty percent shrink is possible even at minimum tonnage, meaning that the smallest possible volume is seven tonnes at fifty percent premium, though when the capacitors, core and overhead are separate, where would that premium apply?

Leaving that for later, seven tonnes might work for the five tonne overhead, and a two tonne budgeted core if minimum jump volume were eighty tonnes. So, that's two and a half.

A twenty percent shrink would give you eight tonnes at a twenty five percent premium, leaving you a half tonne for capacitors. That's twenty energy points for the budgeted variant, which is a fairly safe two hundred percent of targetted energy points for a hundred parsec tonnes.

Venture Class Jump Drive Module
. overhead
.. technology level
... nine
.. budgeted
... increased size
.. capacitors
... none
.. tonnage
... five tonnes
.. cost
... three and three eighths megaschmuckers
. core
.. technology level
... nine
.. budgeted
... increased size
.. tonnage
... two and a half tonnes
.. cost
... one and eleven sixteenths (1.6875) megaschmuckers
. capacitors
.. technology level
... nine
.. budgeted
... increased size
.. capacity
... twenty energy points
.. tonnage
... half tonne
.. cost
... one and one eighth megaschmuckers
. total tonnage
.. eight
. total cost
.. six and three sixteenths (6.1675) megachmuckers

All I can take from that is it would have to be assembled and the shell manufactured at a minimum technological level eleven facility, though what that would cost is unclear, and probably would involve shaving off some more costs off the above individual components, and then calculating a twenty premium on that.

Another question would be just building a ten tonne, and leaving the twoish tonne empty, or if a filler is required, add that. Threadripper adds dummy die, less likely as maintaining communications between active modules and balance the heat distribution, more likely as place holders.

Filler for all intends or practical purposes would cost nothing, as a dummy die could be failed silicon and would be discarded.

If the shell can't be empty, you could add in dead capacitors, if it requires related machinery and equipment.

That way, you sacrifice volume, two plus tonnes, in exchange for paying only for exact size of jump drive core you need, in this case two and a half tonnes plus enough functioning capacitors.

I would have added the batteries, but felt I couldn't establish if anything not organic to the jump drive itself would be kosher.

 

[Condottiere]

Starships: Engineering, and Chemical Power Plants, huh, yeah, What are they good for, Absolutely nothing

Well, maybe not.

I wouldn't want to transition without a fusion reactor as the primary power plant; however, reactors tend to be closed boxes, and with fission ones, that's probably a good thing.

On the other hand, maintaining and/or repairing them, requires special tools and expertise. That's rather less so with a chemical based power plant.

I think it's a viable option for a scout sized vessel, as long as the crew has access to ready supplies of fuel.

Speaking of which, what fuel does the chemical power plant use?

For orbital trafficking, the short durations aren't an issue, and you'd assue that more advanced models could cut down on the gas guzzling aspect, so energy efficiency should be an advantage.

 

[Condottiere]

Spaceships: Engineering and Solar Panelling

Extendible solar panels provide backup power for a ship’s power plant. They are typically installed in scout or mining ships, extending their range and endurance.

The tonnage consumed by enough solar panels required to power a ship is equal to ten percent that of the main power plant, to a minimum of half a tonne. Solar panels cost a hundred kilocredits per tonne.

If the panels are fitted to a ship without a power plant, then assume the (non–existent) power plant is sized to the ship’s basic systems and a Thrust One manoeuvre drive. A ship equipped with solar panels consumes power plant fuel at one–quarter the normal rate so long as it is only engaged in minimal manoeuvring and does not fire any weapons. Minimal manoeuvring does not include long periods at full thrust, so solar power alone is useless for most commercial and military vessels.

No power plant fuel is consumed, and endurance is considered infinite, if the ship is not manoeuvring or refining fuel. Jump drives cannot be engaged with solar panels deployed. Why?

Anyway.

1. Solar panels' default technological level and power output is directly connected to the power plant or conceptualized virtual power plant that they are supporting or supplementing. That makes a technological level fifteen model very bangish for the buck, since their cost is not dependent on the power plant's, just their volume.

2. At the other end of the scale, you have a dichotomy, as a fission reactor obviously radiates better than a higher teched chemical power plant, though one supposes it does slow down atomic reaction by seventy five percent.

3. I think one assumption that one should not make is that proxying a conceptualized power plant and thrust one manoeuvre drive does not mean that the solar panel actually outputs that amount of power, just that the solar panels would have to be ten percent of volume of the conceptualized power plant, which could well be just a tad of half of default power, basically ten power points for basic ship systems per hundred tonnes, plus ten percent. That would account for that rather precarious issue with running manoeuvre drives at length.

 

[Sigtrygg]

Solar panels have one intrinsic limitation - they can not gather more energy than there is incident. There may be TL improvements that allow nearly 100% capture, but you are still limited to generating no more electricity than there is incident radiation.

For a ship in orbit around the Earth each square metre of panel:

TL6 125 W - 25% degradation per year of use
TL7 250 W - 10% degradation per year
TL8 500 W no degradation if maintained
TL9 750 W
TL10 1kW
TL11 1.25kW (this is the maximum you can get)

This lead me to the inescapable conclusion years ago that collector technology doesn't just gather light it must also absorb neutrinos, gravitational waves, particulate radiation (the solar wind) the lot in order to power a jump drive - the alternative is that there is some as yet unknown to the standard model particle that fusion reactors(and stars) and antimatter/matter annihilation produce that is used in the jump drive (you could handwave dark matter or dark energy at this point).

 

[Condottiere]

Once i started looking seriously at ours, I came to the conclusion that they're supra-efficient, limited only by vague references to acceleration.

Degradation is pretty much linked to general maintenance, in our case one tenth of a percent per annum, and maybe a quirk perhaps every fifty years.

The best visualization I've had is that the ship pulse accelerates: after accumulating enough energy, the panelling is retracted, the thrusters are fired up for a turn or so, and the panelling is then extended again.

 

[Condottiere]

Spaceships: Aerospaceplane

For obvious reasons, I hardly bother looking at technology greater than fourteen, and usually the introduction of fusion reactors marks the lower boundary.

Now, I've no qualms of minimum one tonne power plants for spaceship designs, since they represent economies of scale, though less so with a minimum thirty seven hundred gallon tank. So, let's fill it with lemonade.

This is a technological level seven design, and has a ten tonne minimum streamlined titanium steel non gravitated light hull with aerofoils. Half a tonne at two hundred and thirty thousand schmuckers.

Sensors are limited to a Mark One Eyeball, and the operator is comfortably seated on a single cockpit, with a five bandwidth computer. One and a half tonnes at forty five thousand schmuckers.

A one tonne budgetted chemical power plant with a one tonne fuel tank, and a six hundred kilogramme factor three rocket. The power plant outputs four energy points and costs one hundred and fifty thousand schmuckers, and the tank lasts about thirty three and a half hours at full load, adding some solar panelling will quadruple that; the rocket costs one hundred and twenty thousand schmuckers.

Cargo fifty four hundred kilogrammes.

Optional would be half a tonne of solar panelling at fifty thousand schmuckers, acceleration benches, acceleration couches, brig, mounted or dismounted missile launcher, missiles and/or fuel. Not so sure about the airlock/cargo hatch, maybe a hatchback?

Base cost five hundred and twenty five thousand schmuckers.

Neat business jet and lunar transport.

 

[Condottiere]

Starships: The Sad Truth About Life On The Millennium Falcon

The Millennium Falcon is just about the coolest spaceship in sci-fi history. And it's also an uncomfortable, unreliable, ugly hunk of junk. Sure, it might feel tempting to hop aboard and live out your days as a devilish rogue or a heroic starfighter, but you're probably better off keeping your feet on the ground. Here's a look at why it would pretty much suck to live on the Millennium Falcon...

Moving target | 0:22
Bucket of bolts | 1:05
It's too cramped | 1:36
Gas attack | 2:05
Unwelcome surprises | 2:35
The facilities suck | 3:07
It's boring | 3:43
It's ugly | 4:22

https://www.youtube.com/watch?v=-vkNSp74VIE

But it's lucky, despite it's quirks.

Or maybe luck is a quirk.

 

[Condottiere]

Spaceships: Aerospaceplane

For obvious reasons, I hardly bother looking at technology greater than fourteen, and usually the introduction of fusion reactors marks the lower boundary.

Now, I've no qualms of minimum one tonne power plants for spaceship designs, since they represent economies of scale, though less so with a minimum thirty seven hundred gallon tank. So, let's fill it with lemonade.

This is a technological level seven design, and has a ten tonne minimum streamlined titanium steel non gravitated light hull with aerofoils. Half a tonne at two hundred and thirty thousand schmuckers.

Sensors are limited to a Mark One Eyeball, and the operator is comfortably seated on a single cockpit, with a five bandwidth computer. One and a half tonnes at forty five thousand schmuckers.

A one tonne budgetted chemical power plant with a one tonne fuel tank, and a six hundred kilogramme factor three rocket. The power plant outputs four energy points and costs one hundred and fifty thousand schmuckers, and the tank lasts about thirty three and a half hours at full load, adding some solar panelling will quadruple that; the rocket costs one hundred and twenty thousand schmuckers.

Cargo fifty four hundred kilogrammes.

Optional would be half a tonne of solar panelling at fifty thousand schmuckers, acceleration benches, acceleration couches, brig, mounted or dismounted missile launcher, missiles and/or fuel. Not so sure about the airlock/cargo hatch, maybe a hatchback?

Base cost five hundred and twenty five thousand schmuckers.

Neat business jet and lunar transport.


Let's try upscaling it to my next favourite size, thirty five tonnes.

The hull's still made of light titanium steel, remains streamlined, is non gravitated, and has one and three quarter tonnes of aerofins. 962.5 megaschmuckers.

Operator still reliant on using the Force, and is stuck in a single cockpit, with a five bandwidth computer. One and a half tonnes at forty thousand schmuckers.

Note: I've miscalculated the cost of cockpits, so note the above correction, and that any previous mention of ship system workstation cost should be adjusted to five thousand schmuckers per.

A one tonne budgetted chemical power plant with a one tonne fuel tank, and a twenty one hundred kilogramme factor three rocket. The power plant outputs four energy points and costs one hundred and fifty thousand schmuckers, and the tank lasts about thirty three and a half hours at full load, adding some solar panelling will quadruple that.

The power plant provides just enough for minimal basic functional spacecraft, plus one energy point can be harvested every seven turns to recharge the batteries, if any. Minimum half tonne solar panelling can replace any conceptualized five tonne power plant, so basically the spacecract could be run just with that alone and switch off the chemical power plant, and still have almost sixty percent redundancy.

The rocket costs four hundred and twenty thousand schmuckers.

Cargo 27.15 tonnes.

1'572'500 schmuckers, plus fifty thousand for solar panelling.

 

[Condottiere]

Spaceships: Aerospaceplane, Engineering and My Chemical Romance

The problem with batteries is that they tend to run out of juice, if you can't find a way to recharge them, and seventeen hundred turns in hyperspace ought to do that.

Using a chemical power plant is plausible if you set aside a large enough fuel tank allocation, but once early fusion becomes available, which costs at default the same as the chemical plant per megawatt, it's a rather senseless exercise, unless the issue has to do stealth and an incapability to detect chemical power plants in space.

It might actually be viable as the principle power plant for a rocket powererd and missile armed short duration light attack craft or point defense interceptor, the other ship systems being battery powered, which would only be turned on as the craft enters combat.

 

[baithammer]

This lead me to the inescapable conclusion years ago that collector technology doesn't just gather light it must also absorb neutrinos, gravitational waves, particulate radiation (the solar wind) the lot in order to power a jump drive - the alternative is that there is some as yet unknown to the standard model particle that fusion reactors(and stars) and antimatter/matter annihilation produce that is used in the jump drive (you could handwave dark matter or dark energy at this point).

Collector technology replaces the need for jump fuel not the power the requirement.

 

[Condottiere]

Spaceships: Engineering and How NASA Engineers Use Origami To Design Future Spacecraft

NASA is using origami to build a giant star blocker, in hopes of imaging distant worlds.

https://www.youtube.com/watch?v=Ly3hMBD4h5E

I'm thinking extendible solar panelling.

Also, extendible armour shielding.

 

[Condottiere]

Spaceships: Hulls and Cosmonaut Performs Rocket Surgery, While Spacewalking, With a Knife.

The Latest EVA outside the International Space Station saw one of the cosmonauts taking a knife to the outside of their return spacecraft to collect evidence for the investigation of the origin of a hole in the spacecraft.

https://www.youtube.com/watch?v=Lm_fAsUTvgQ

1. Murder on the Orbital Express.

2. Extensible arm Strela (arrow) boom.

3. Thick thermal blanket to control temperature within spacecraft.

4. Eight layers of fibreglass, fabric (Kevlar?) and foil.

5. Thin aluminium meteorite shield.

6. Littering.

7. Don't dispose of the toilet until you're ready to drop; and now you know, and knowing is half the battle.

 

[Condottiere]

Spaceships: Engineering and Upward Bound Power Satellites

Beaming energy down from satellites in orbit to replace the production of electricity on Earth may solve many of our problems, and avoid a potential economic or ecological crisis such as energy bottlenecks or global warming. Today we will explore how wireless microwave transmission of energy down to rectennas may not only be possible, but could be massively profitable in the near future and spur our exploration and colonization of space.

https://www.youtube.com/watch?v=eBCbdThIJNE

Even if you think on the small scale, you can power drones that follow your ship like pilot fish.

 

[Condottiere]

Spaceships: Engineering, and Little Rockets, Man!

Well, firmpointed big rocket pods.

Anyway, the only advantages that rocket motors have is that move faster up the tech tree than manoeuvre drives, and they are five times cheaper.

I think they're simple to maintain, repair and manufacture in comparison to the alternative.

However, they are gas guzzlers, and it's unclear how they stand in regard to inertial compensation, meaning it's pretty much guesswork if you could maintain acceleration beyond three gees without killing the crew.

Combine that short duration with the normal rotation of twelve hour pilot rotations, you could install them in combat craft that wouldn't be expected to remain long on the line, or far from a mothership.

I think most commercial concerns will upgrade to manoeuvre drives as soon as they can afford it.

I think it will eventually come down to gravitated hulls equals inertial compensation as well, or if it requires a manoeuvre drive to create an inertial compensation field.

 

[Condottiere]

Spaceships: Armaments, Sandcasters and High Explosives

A general-purpose bomb is an air-dropped bomb intended as a compromise between blast damage, penetration, and fragmentation in explosive effect. They are designed to be effective against enemy troops, vehicles, and buildings.

...

General-purpose (GP) bombs use a thick-walled metal casing with explosive filler (typically TNT, Composition B, or Tritonal in NATO or United States service) composing about 30% to 40% of the bomb's total weight. The British term for a bomb of this type is "medium case" or "medium capacity" (MC). The GP bomb is a common weapon of fighter bomber and attack aircraft because it is useful for a variety of tactical applications and relatively cheap.

General-purpose bombs are often identified by their weight (e.g., 500 lb, 227 kg). In many cases this is strictly a nominal weight (the counterpart to the caliber of a firearm), and the actual weight of each individual weapon may vary depending on its retardation, fusing, carriage, and guidance systems. For example, the actual weight of a U.S. M117 bomb, nominally 750 lb (340 kg), is typically around 820 lb (372 kg).

Most modern air-dropped GP bombs are designed to minimize drag for external carriage on aircraft lacking bomb bays.

In low-altitude attacks, there is a danger of the attacking aircraft being caught in the blast of its own weapons. To address this problem, GP bombs are often fitted with retarders, parachutes or pop-out fins that slow the bomb's descent to allow the aircraft time to escape the detonation.

GP bombs can be fitted with a variety of fuzes and fins for different uses. One notable example is the "daisy cutter" fuze used in Vietnam War era American weapons, an extended probe designed to ensure that the bomb would detonate on contact (even with foliage) rather than burying itself in earth or mud, which would reduce its effectiveness. (This was not the first instance of such devices. As early as World War II, the Luftwaffe was using extended-nose fuzes on bombs dropped by Stuka dive-bombers and other aircraft for exactly the same reason. A blast several feet above the ground is many times more effective and has a far greater radius than one that is delayed until the bomb is below the surface.)

GP bombs are commonly used as the warheads for more sophisticated precision-guided munitions. Using various types of seeker and electrically controlled fins turns a basic 'iron' bomb into a laser-guided bomb (like the U.S. Paveway series), an electro-optical guided bomb, or, more recently, GPS-guided weapon (like the U.S. JDAM). The combination is cheaper than a true guided missile (and can be more easily upgraded or replaced in service), but is substantially more accurate than an unguided bomb.

...

A Mk. 82 GP bomb loaded on an F/A-18 Hornet, showing nose fuze and textured thermal insulation
During the Korean War and Vietnam War the U.S. used older designs like the M117 and M118, which had an explosive content about 65% higher than most contemporary weapons. Although some of these weapons remain in the U.S. arsenal, they are little used and the M117 is primarily carried only by the B-52 Stratofortress.

The primary U.S. GP bombs are the Mark 80 series. This class of weapons uses a shape known as Aero 1A, designed by Ed Heinemann of Douglas Aircraft as the result of studies in 1946. It has a length-to-diameter ratio of about 8:1, and results in minimal drag for the carrier aircraft. The Mark 80 series was not used in combat until the Vietnam War, but has since replaced most earlier GP weapons.

...

Since the Vietnam War, United States Navy and United States Marine Corps GP bombs are distinguished by a thick ablative fire-retardant coating, which is designed to delay any potential accidental explosion in the event of a shipboard fire. Land-based air forces typically do not use such coatings, largely because they add some 30 lb (14 kg) to the weight of the complete weapon.[citation needed] Fire is less a danger in a land-based facility, where the personnel can be evacuated with relative ease, and the building be the only loss. At sea, the crew and munitions share a facility (the ship), and thus are in much more danger of fire reaching munitions (which tend to be more closely packed, due to space limitations). Also, losing a munitions storage building on land is far cheaper than sacrificing an entire naval vessel, even if one could easily evacuate the crew.

All Mk80 bombs have both nose and tail fuze wells and can accept a variety of fuzes. Various nose and tail kits can be fitted to adapt the weapon for a variety of roles.

...

The Mark 84 has a nominal weight of 2,000 lb (907.2 kg), but its actual weight varies depending on its fin, fuze options, and retardation configuration, from 1,972 to 2,083 lb (894.5 to 944.8 kg). It is a streamlined steel casing filled with 945 lb (428.6 kg) of Tritonal high explosive.[1]

The Mark 84 is capable of forming a crater 50 feet (15.2 m) wide and 36 ft (11.0 m) deep. It can penetrate up to 15 inches (381.0 mm) of metal or 11 ft (3.4 m) of concrete, depending on the height from which it is dropped, and causes lethal fragmentation to a radius of 400 yards (365.8 m).[3]

Many Mark 84s have been retrofitted with stabilizing and retarding devices to provide precision guidance capabilities. They serve as the warhead of a variety of precision-guided munitions, including the GBU-10/GBU-24/GBU-27 Paveway laser-guided bombs, GBU-15 electro-optical bomb, GBU-31 JDAM and Quickstrike sea mines.[4] The HGK is a Turkish guidance kit used to convert 2000-lb Mark 84 bombs into GPS/INS guided smart bombs.[5]

According to a test report conducted by the United States Navy's Weapon System Explosives Safety Review Board (WSESRB) established in the wake of the 1967 USS Forrestal fire, the cooking off time for a Mk 84 is approximately 8 minutes 40 seconds.


1. How much of that fits into 0.7 cubic metres?

2. Since there is no air resistance in space, you could drop rectangles.

3. Laser guided kits are optional.

 

[Condottiere]

Spaceships: Hulls, Stealth and Salt-infused graphene creates an infrared cloaking device

Infrared emissions that are controlled by salt infusion make good camouflage.

CHRIS LEE - 8/3/2018, 4:09 PM
That's not a Warhol. That's the material described here, showing fine control over whether it's hotter or colder than its surroundings.

I love light and the various manners in which we can control it. It's a good time for me, as we are truly in a golden age of light control. We can manipulate it to see details that would otherwise be invisible. We can guide it around objects so that they are invisible. Light has been made to stand still and dance on the pointy end of pins.

All this control of light is indirect, coming via our control of materials that the light interacts with. Now, researchers have crafted a material that adapts its properties so that its infrared appearance is either hotter or colder than the object it encloses. In other words, hot objects appear cold, or cold objects can appear hot—it's infrared camouflage.

It’s all about those electrons

So, do you make yourself some infrared camo gear? The basic procedure is to control the efficiency with a material that can emit infrared radiation. Take gold as an example. Gold is a nearly perfect metal: it has high conductivity and does not absorb infrared radiation very easily. That means it will reflect incoming radiation; this is why emergency blankets have a thin gold coating: the gold reflects your own infrared radiation back to you to keep you warm.

At the other end of the scale you have something like the black soot from a fire. Soot is not very reflective, so the background infrared radiation is not scattered by the soot. But, if it is placed on a heating plate, it will glow in the infrared. Gold, by contrast, doesn't tend to emit at these wavelengths.

The efficiency with which a material emits (or absorbs) light is described by its emissivity, which scales from zero to one. Gold is very close to zero, while a perfect emitter (like soot) is close to unity.

Emissivity is the knob that the researchers turn to control the infrared appearance of their material. To do this, they make use of the unusual properties of graphene. Graphene is a single layer of carbon atoms, all arranged in a hexagonal pattern. It's not quite a metal; it is more like a semiconductor like the silicon that the CPU powering the device you're reading this on is made from. The difference is that silicon only starts to conduct if you apply a measurable voltage to it, while graphene starts to conduct as soon as the voltage is non-zero (this is called a zero band gap semiconductor). This means that graphene always has electrons available to conduct—but not all that many. And, when you take into account defects in fabrication, the conductivity of some graphene layers can be quite poor.

But, like other semiconductors, the conductivity can be changed by adding impurities that contain additional electrons. For instance, adding a small amount of phosphorus to silicon gives it a higher conductivity, because phosphorus has spare electrons to give up.

A salty blanket

The researchers made a thick graphene layer (around 100 to 150 graphene sheets thick) that had very poor conductivity. As a result, the emissivity of the layer is quite high. Under that layer, they placed a thin coating of ionic fluid. The ionic fluid is, essentially, a liquid salt (not a salt dissolved in water). The liquid salt was sealed in place by a thin layer of transparent plastic and the whole lot was placed on a thin gold electrode.

Under ordinary conditions, the salt layer sits outside the graphene layer, which absorbs and radiates infrared light. However, if a voltage is applied between the graphene layer and the gold layer, then the ions in the liquid move into the graphene, giving it a higher conductivity. As a result, it stops absorbing and radiating infrared radiation and becomes an infrared reflector. Even better, the transition from absorber to reflector is controllable. Different voltages result in different conductivities, so the emissivity of the graphene layer varies continuously from its maximum to its minimum value (0.8 to 0.35).

What does that mean? Well, imagine placing this over a hot plate. If the emissivity is set to its minimum value, the hot plate will appear to be the same temperature as its surroundings: it is hidden. But you can also go the other way: if the emissivity is increased, then the hot plate will appear to be hotter than it otherwise would.

At first this appears counterintuitive: if the layer is glowing hotter than the thing it is covering, surely the material is actively cooling the hot plate. I would say that, on the face of it, this has to be true. But in practice, it depends on a number of factors: the temperature of the object depends on the efficiency of its infrared radiation emission but also on its conduction to the surroundings and convection (the mass motion of warm fluid, like air, carrying heat away). The covering could simply change the balance between these different heat transfer mechanisms rather than actually cool the covered object.

Seeing is believing

The researchers show lots of pictures and movies of their material camouflaging hot objects. They show that the material is flexible, so it could be worn. And, equally important, it is vacuum compatible.

It may come as a surprise, but keeping things cool or warm in vacuum chambers and in space is a proper challenge. Under ordinary circumstances, convection carries the majority of heat away from a warm object—this is why radiators are so good at keeping houses warm. In a vacuum, there is nothing to carry the heat. So, in the end, the only way to control temperature is through changing how efficiently heat is radiated from surfaces. And, now we have a material that can do this. I think that is probably the more important application.

Of course, we don’t know how physically robust the material is or how many emissivity transitions it can do before it stops working. But, assuming these pan out and that the ionic liquid is not too expensive or toxic, then I can imagine this turning up in specialist applications pretty quickly.

https://arstechnica.com/science/2018/08/salt-infused-graphene-makes-for-a-infrared-cloaking-device/

Insaltation.

 

[locarno24]

Spaceships: Armaments, Sandcasters and High Explosives

1. How much of that fits into 0.7 cubic metres?

2. Since there is no air resistance in space, you could drop rectangles.

3. Laser guided kits are optional.

The Mk82 - the 500lb version, and pretty much the lightest - is a couple of metres long by just under a foot across as an 'all-up' round (with a standard nose and tail fitted)

You could fit 5 of those plus some change (which would get used for brackets and grips) in 0.7 m3


The tactical value is.....questionable:
~ Versus a mobile target capable of manoeuvring at several G, ballistic warheads won't achieve much outside pretty much point blank range
~ Might be useful for a stationary target - on the one hand a ballistic target is a bloody easy job for point defence, on the other a non-radiating ballistic object might stand a chance of not being spotted before close range if a target isn't on high alert
~ Something which looks like a freefall bomb is not going to survive a ballistic re-entry and if it could then you might as well make it a warhead-free ortillery round and just hit the target with a lump of bonded superdense moving at orbital speeds.

Obviously they're useful for close air support for in-atmosphere fights.


Probably more relevant is the concept of 'modular' weapons. Having seeker heads, manoeuvring drive fins, main drive tail sections and warheads all be 'interchangeable' components built to common standards gives you a lot of flexibility - firstly your fleet armourers can assemble nukes, standard missiles, multiwarhead missiles or whatever as the mission requires, but also you can store the components more safely (a fuze, by definition, has to be pretty easy to set off even if it's not too powerful, so being able to store it physically removed from the warhead is a basic safety principle) but you can have different manufacturers provide you with bits as needed and as manufacturing capacity is available.

TL12 missile drives are obviously going to be 'worse' than TL15 missile drives, for example, aside from one key virtue - the system fleet dump is full of the bloody things and you can take and use them to rearm NOW instead of waiting a fortnight for a sector flee depot ship to turn up...