PAART | MESOCAMBRIAN | CAMBRIAN | PART 2.5

OTHER CONCEPTS | SPACESHIP DESIGN & SPACE WARFARE | PART 3 - A PRACTICAL APPROACH

OUT TO THE BATH TUB FIELD TESTING

It's been one year since the last time we talked about Space Warfare here on Hard Sci-Fi.

Let's recap what happened of the course of the previous two posts:

PART 1 - MOST SHIPS IN SCIENCE FICTION MAKE NO SENSE

PART 2 - WHY COMMON COUNTER ARGUMENTS MAKE EVEN LESS SENSE, EVEN IN-UNIVERSE

In Part 2, I left the post on a cliffhanger about disruptive camouflages - highlight to a more sci-fi approach to Dazzle camouflage.

Amongst other types of camouflage, I had also included chemicals that disguise the ship as another object like a comet, and reflective panels that can be tweaked in order the flash light-rays into or away from the enemy (also known as mirrors).

This time, I'm willing to test some of those approaches, in a simple observation test, simulated in a 3D modeling software.

So, meet our test ships:

NSC 042 - SCITALIS

This design is inspired by the myriad of accurate and cool-looking spaceships created by MarkPoe

The Nuclear-Powered Support Cruiser 's role is to ensure the security of high-value targets by supporting the escort effort with massive suppressive firepower, hence why it has a ridge along it's hull, from where 75x 80mm Fast-Pace Artillery guns (FPA), and 6x 300kg Kinetic-Kill Disperser weapons (KKD) - per side.

So basically each broadside holds 75x machine guns and 6x shotguns.

Why this ship carries relatively small machine guns and a couple of shotguns are because of two reasons.

1. The sharp acute holes of the bullets are meant to be very hard to find and repair compared to the amount of damage to O2, electronics and heatsink systems on the enemy - firing along a path line grants more potential hits and suppressive fire. 

2. Shotguns are crude in space, and mainly if the enemy is accompanied - granting sector clearance nearby because of the nearly invisible but deadly pellets (and there is 300kg of them per shot), such weapons can also intercept HTK vehicles and drones inbound, making very large projectiles or missiles not so useful from certain angles.

The name Scitalis, refers to the medieval beast that sports beautiful shiny marks - pretty straight forward.

The four plates are shielding the fuel tanks against debris and projectiles, the two skirts are sections of parabolic surfaces, so incoming kinetic projectiles are ricocheted away from the ship's hull, the internal reflection angles were carefully chosen so any shots fired against them wouldn't redirect the bullets to sensible parts of the beaming and engines.

The standard combat instance for this ship would then be facing the enemy at 3/4, with minimal exposition of sensible parts and maximum weapon coverage (like the top-right window view).

A Critical Analysis on Discovery's [Alien Planet]

WHY DISCOVERY'S 'ALIEN PLANET' IS BAD

Alien Planet is a 94-minute docufiction, originally airing on the Discovery Channel, about two internationally built robot probes searching for alien life on the fictional planet Darwin IV. It was based on the book Expedition, by sci-fi/fantasy artist and writer Wayne Douglas Barlowe, who was also executive producer on the special. It premiered on May 14, 2005. - Wikipedia

So, as an enthusiast of Science-Fiction, you and I have heard and stumbled upon Extraterrestrial - Alien Worlds (2005), The Future is Wild (2002), and Alien Planet (2005), among others.

I recall seeing those somewhere else earlier, maybe on Animal Planet and Discovery channel - my favorites as a kid and the places where it was initially exhibited, and definitely on later months during quarantine.

A couple hours ago I decided to get my hands on Discovery's docufiction Alien Planet. And honestly, with the amount of people I saw and heard from, elevating this work up high in the sky as a great reference to science fiction and worldbuilding, I must admit I'm pretty much disappointed with the show.

Assume you are no science person, and you'll see why is that - and now I get why many people may regard this a great show, while actually is more of a fiction fantasy thing than actual hard science as some may hoist it,

Before I get stoned by you hard fans of Wayne D. Barlowe's work, I will only refer to what is presented on the show, and point what is misleading and straight out fiction about it, I got my hands on a copy of the book hoping for some answers on the matter, and this post might get a second part - so, let's get into it.

FIRST IMPRESSIONS

The show opens with an impacting line:

We now take a simulated journey scientifically verified by leading experts - to a planet called Darwin IV - Narrator, 1:40 into the show

Alright, they have brought us Jack Horner (Curator of Paleontology at the Museum of the Rockies in Bozeman, Montana) and Victoria Meadows (Professor with the Astronomy Department and Director of the Astrobiology Program at the University of Washington) - so they might have checked on something, right?

They make it very clear to the audience they did put a lot of effort into fact checking every aspect of the work they were doing, as stated:

It seemed utterly important to me that the foundation to create a world, was to make sure the world was acceptable to the science community. - Wayne D. Barlowe, 2:45 into the show.

Now we put together a team of scientists to have a look at that concept, and to make sure that the laws of Physics and Chemistry were all represented in that model. - Victoria Meadows, 2:55 ITS.

By this point, I was expecting the next Interstellar (2014), by stated amount of effort and specialists on the matter - and they expend the next few minutes explaining the ship and interstellar travel.

LIFE ON DARWIN IV

As soon as we arrive, we are presented to a pair of creatures (apart from the microbes on a nearby pond), one which is a two legged T-rex analogue predator, and the other is a two legged large prey.

At first, this might sound reasonable, both may be related, until you notice the prey apparently descends from a 4-legged animal, which frontal and back pairs of limbs fused into a front and back limb.

Now, won't discuss the actual feasibility of this form of motion - but the actual process which lead to this animal in the first place, because, imagine how actually inefficient would be the transitional forms from quadruped to biped in this case - and how exactly that turned out to be a viable solution when you could have gotten smaller? Stronger? developed antlers or something else? But then nature comes with the hardest way, make it biped in the less efficient way possible.

The predator is rather intriguing, as the rest of the creatures of the show also are - it is actually the first to be introduced, and we are informed it cannot see properly, as it uses sonar to identify it's surroundings - along with other creatures we will see later, and that by the night creatures produce bioluminescence.

So... WTH is happening here?

SONAR... REALLY?

Because, as we've seem so far into the show (+20min), and we will continue to see that, there is plenty of sunlight available - of course, there is this thick layer of clouds and atmosphere partially blocking most of sunlight, but there is still sufficient light that plant-life can make good use of.

Low light plants can sustain photosynthesis with around 10~15 W/ft², or about 107,6~161,4 W/m² of fluorescent lighting - which means that theoretically you could grow plants in an asteroid or planet 3,5 AU away from the Sun, further than that only algae and mosses may grow, but only to a certain extent, given the ambient is maintained warm enough so they don't freeze.

Darwin IV orbits the largest member of a binary system, and being in the HZ, should receive similar amounts of lighting Earth does, the planet does host vegetation, and the planet does receive a decent lighting - even through the dense water vapor atmosphere, often cloudy as we see depicted. - and even so, creatures on Darwin IV for some reason haven't evolved eyes, or at least proper vision - instead recurring to sonar, making howls and roaring to scan their surroundings, when those conditions actually favor eyesight in every way, although not as much as on Earth.

See, as explained on the post about Animal Vision, eyesight is actually a pretty game changing evolutionary step,  it basically shaped life on Earth, and other ways to scan it's environment like sonar and pit organs wouldn't appear for a couple hundred millions years after eyesight was already established, and they did appear as auxiliary senses to vision.

It seems very unlikely life would develop other way in that sense, having to come up with sonar rather than developing decent eyesight to it's environment, and given the worst scenario - that Darwin IV lies on the outer edge of the habitable zone and receives less light than Earth, it wouldn't justify sonar still, as creatures could use larger eyes, pit organs or UV sensing rods to further increase image exposure, all of which are actually more likely and energy efficient than using sonar.

Another problem with sonar, is that the way we actually use sonar on Earth is very different than the way portrayed in the show, and implies the breaking of some basic already well established strategies in nature.

In the sea, sonar turns out to be pretty useful, the water as a denser medium than air transmits sound waves quicker and more intensely, and given light does not penetrate well further than 200m into the water - sonar is a viable tool to use.

Sonar, depending on the frequency you are using, works as both a pulsating flashlight, or as a faint x-ray of the environment.

If you use high-frequency sound in your sonar, the small waves will bounce off objects like you were emitting light in the dark, ie, your readings would be unable to reach for example behind a whale, or a rock.
If you use low-frequency sound, small objects such as little fish, or details on surfaces are ignored, but the lower frequency waves can bend around corners of a certain size with ease, and thus giving you some faint reading from behind objects.
Use a mix of both, and you can pretty much scan your surroundings no problem, HOWEVER that assumes you are actually totally immersed in such medium.

The problem with sonar use for active hunting is the same with sonar in underwater warfare, and the same with radar in space warfare. If you can see them, they can see you.

Submarines and ships often use passive sonar, either from listening to animals like whales and dolphins, the engine of their own ship or enemy ships, or sonar buoys in the area, because if they use Active Sonar, they will ping your position every time the sonar ticks.

Air isn't a good medium for sound, half the energy of the ping will be discharged onto the ground around you, and nearly the other half onto the air above you, you're only using a ring which is a couple meters tall to detect prey or predators, your best chance against them is high-frequency sonar like a bat, because low-frequency will just go around objects and not bump into something else to come back to you (like the seafloor or a coral reef), sonar on the air medium as portrayed is very energy wasteful and then no more efficient than actual eyesight in plain daylight.

One could argue that camouflage would trick eyesight in that case - but UV and IR markings can be used and are used by reptiles and birds to identify comrades and prey, so it isn't far fetched such system would be used in another planet by life, also, Darwin IV lacks the savanna vegetation that gives animals like lions their camouflage advantages, there isn't much about the Darwinian landscape that you can mix into for camouflage, eyesight again would be a great tool against any of those threats.


And thus no real apex predator would use active sonar for hunting, unless it was extremely necessary like in the dark, as bats and dolphins do, and much less use low frequency sounds to do so, because you will be just pinging your position much before you reveal from your ambush spot, it would be actually much easier if the presented predator actually sat and waited listening to it's prey approaching it's killzone and then launched an attack - much by the contrary of what is said by minute 27:42, the animal presented is a walking waste of evolution points, there are much more efficient ways to be an ambush predator, and it does in the less efficient way.

Even the T-rex isn't believed anymore to be an active predator anymore, but partially a scavenger.

The second predator, the gliding vampire alien, actually makes a lot more sense than the first presented on that matter.

Sonar, as an active communication tool is otherwise good for reasons already shown.


Bioluminescense is cited multiple times, we are informed that besides mainly using sonar, eyesight is still a thing, though poorly developed (somehow), and we will tackle that later on.


A LIVING... JET FIGHTER?

The third predator shows at 49:22 ITS, a flying creature that hunts in pairs, impales and drains prey in the air.

The flying creatures do not use their wings and tail in the way you would expect a typical flying creature to do so, beat their wings around and tip their tail to the side to maneuver, no.

These flying predators are actually using jet propulsion to fly (53:25 ITS) - by combusting methane in 4 pods located in their wings (2 on each side).

Now, apart from other creatures, this flying predator is one I actually wanted to investigate the first time I saw it.

At first my thoughts were, there is no real, feasible way the creature can produce the liters of methane required for sustained flight they way it appears to need.

One of my works as a Chemical Engineering student was to plan a methane gas generator, and after going through the research to do so, you too will be rather upset of how little methane you can make over the course of days compared to amount of work, which might enough to cook a meal, but no enough for a rocket also.

To plot that, we will need a way to measure the creature's size, and velocity, to estimate it's mass and fuel consumption.

Now for that, I recurred to Darwin IV's wikipedia page to get the planet distance to it's star, so I can calculate the apparent size of the main sun in the sky, and use the 53:10~53:14 scene to estimate the creature's velocity, knowing it's stated size at 53:18.

50ft = 15,24m

Darwin A angular size in the sky: 0,617º

I took two prints, one at 53:12 and the other at 53:13, a ~1 second interval.

First, we range the distance between the creature and the imaginary line that passes through the viewer and the sun.

On the next step we do the same.

Here is the frames collated together, from the angular size of the animal, and knowing it's true wingspan, we can calculate it's distance from the viewer, the line connecting both lines that pass through have somewhat between 83m and 102,2m, these 20-ish meters can be considered the curve the animal does on flight while turning around so we will stay with with 83m direct measure.

Bellow is an schematic of what is happening on the scene, and how we calculate the speed from this scene.

So it turns out that our little living jets fly at Mach 2,84 - as on the portuguese wiki (link further bellow) cites, Darwin IV's atmospheric pressure is around double that of Earth's (due more air present),  the actual speed is Mach 2,6 because on a denser atmosphere, sound travels faster (376,63m/s in this case).

Fandom wiki says it is actually 880km/h, but as we could measure in the show, it is 4x as fast.

There is no mention to the creature's mass so far, on Earth,  the largest flying animal, the Quetzalcoatlus, had a wingspan of 10~18m, weighing about 200~250kg.
However is clear that the animal portrayed is far from having the same body structure and thus weigh class as the largest known pterosaur.

The way the creature maneuvers thorough the show suggests it's external structure is mostly composed of some time of thick hide, and the hard structures are apparently limited to it's head and sharp lance.

To first make a rough estimate of it's volume, I went after a top view image of the creature onto the Alien Planet fandom wiki, and then masked out the surroundings as shown.


Then going into Image Summarizer, I set the color cluster to 6, the precision to 100px, and the final result is that the red part of the image is ~85% of the pixels.

The image is 933x677 px, which makes the total number about 631.641 pixels - we only care about the remaining 15% of them, ie, 94.746,15 px, which is the total area of the creature. The creature in turn is 792px wide, what makes each px about 2x2cm (actually 1,924x1,924cm).
The flat area of the creature is then about 35,07m².

The mean height of the creature is similar to it's body horizontal length, which is like a cylinder, the wing is thinner after the last burning pod, about 1/4th the head height. These are our parameters.

With a body 46px wide, ie, 88,5cm wide, that gives us body height of ~88,5cm too, and it also makes our wing thickness about 22,12cm.

Wing tips can be covered by a right triangle 230x110px, making each wing tip 12.650px² in area, or about 4,68m² on each wing.

Given that, we have a body volume of: 35,07 - 2(4,68) = 25,71m² * 0,885m = 22,75m³

Wing tip volume: (2*4,68) * 0,2212m = 2,07m³

Total volume: 24,82m³

For perspective;

Mammalian muscle tissue have a density of 1.060kg/m³, and human bone is 1850kg/m², assume this animal is 70/30 meat and bone, and we get an average density of 1.297kg/m³, which then makes this animal's weight about................ 32,19 tons.

Even if we make the bones lighter, say about 1.250kg/m³, we get 27,35 tons.
And if you make the creature out of water, you get 24,82 tons.

Give it an internal cavity of 40% (from an original bulk of 25t) and it is still weighing about 15 tons.

For our next calculation, let's cap a low-end moderate estimate of 20 tons to the creature.

The creature has 4 similarly sized "engines", so I will assume they have the same power.

Methane could produce an exhaust velocity of 3.800 m/s depending the chamber where it's being combusted, LH2/LOX fuel engines for comparison produce over 4.500 m/s.

The rocket equation calculator says the creature would have to combust ~5.840kg of methane in order to reach speeds of 3.505km/h, but that's about it - once you've reached that top speed you're out of fuel.

The thrust of one engine, considering a mass flow rate of 10kg/s, and Darwinian gravity (0,6G), is about 22.344N. Times 4, we get 89.376N, which gives us an acceleration of 4,46m/s² which might seem slow, but is enough to get the creature into top speed in ~3min40s.

To get the total flight time, we have a combustion of 40kg/s and 5.840kg of fuel, that renders us about 146s of flight, or 2min26s, and that's not even speaking of the maneuvers.
For 10 minutes of flight, it would have to carry 24tons of methane, or somehow, collect and instantly produce fuel on the fly in large amounts.

Speaking of which, if the creature produces methane inside it's body to further burning, from the digestion of food. Then, by biogas production standards, each 1kg of food would yield 400 l of gas, or about just 222g of methane, not really taking into account the time needed to do so, which is of at least 40~80 Earth days.

Even if it had some magical cocktail of bacteria that could do it 4x faster, you would need 10~20 days still to convert the fuel, it would need to also eat ~5x the weight of the desired amount of fuel to produce, ie 5*5,8tons = about 29tons of food.

And that's the actual problem I talked about, there is actually no feasible way for the creature to even acquire such quantities of fuel, let alone have sustained flight.

Even so, sonar isn't the best way to equip such a hunter, the sonar ping is useless when you have 4 jet engines strapped to your wings, the sheer noise coming from the combustion is enough to produce the ping you need, the actual problem would be to turn these off at a safe distance so the prey knows you are there already but can't really track your direction by your propulsion noise.


And remember:

Now we put together a team of scientists to have a look at that concept, and to make sure that the laws of Physics and Chemistry were all represented in that model. - Victoria Meadows, 2:55 ITS.

SO WHAT THE H*** JUST HAPPENED OVER HERE???

After that, all of the other animal problems will be addressed later on, let's talk about the world where this is all set...

THE CLIMATE OF DARWIN IV MAKES NO SENSE

I cannot reproduce original Expedition content, however I can show you what other artists have done based of it's material, and here is a map of Darwin IV.

And here is a globe model, highlights to the Amoebic Sea:

Let's take notes on what is portrayed and compare to what would we really see based on what we can take from the map.

PORTRAYED:

Surface Temperature (assume it's average surface temp): about 20~21°C (8:30 ITS)

Darwin IV's oceans evaporated long time ago, changing the climate to it's current state (37:42 ITS)

Sunlight Received: 79% that of Earth's*

Distance to it's star: implied to be around 2AU*

Orbital Period: 1,6 Earth years*

Atmospheric Pressure: 2 atm*

*Source: Portuguese wiki on Darwin IV


CALCULATED:

Main Star Mass: ~3,12 Msol (A0V star, expected lifespan of 582Myr, 295x the Sun's luminosity) calculated from orbital period and orbital distance using Kepler's Third Law.

Main Star Size: ~3.229.331,7 km (calculated from stellar mass/diameter relationship)

Sunlight Received: 73,9x that of Earth's

Surface Temperature: 570ºC (473ºC without atmosphere)

Atmospheric Pressure: 47,82atm (atmospheric half-life is greater than 1Gyr, so the planet is pretty much an evaporating Venus-analogue)

Climatic Index: 73,9 (MERCURY ZONE)


Funny that when we look at the data, our view of the planet shifts from this:

To this:

DARWIN IV'S EVOLUTIONARY TREE IS A MESS

Or very questionable to say the least, the show presents us to a dying planet, which is having it's oceans evaporated - for what I could initially deduce, the planet would have a pretty weak magnetic field around itself, what would lead to the solar wind slowly blowing the water off its upper atmosphere over the eons, and given Darwin IV is a small planet when compared to Earth (just about 6.563km in diameter), it seems to be the case, that would also explain why, even though the oceans have evaporated, why the animals don't experience the weight of billions of tons of water above them, because there isn't that much water in the atmosphere either, once it evaporates, it gets lost to space forever.

The point is, that this seems to be a rather recent event in the planet's history, a few hundred million years to get to the extreme we are presented to in the show.

What I will now call The Recent Catastrophe Theory -  would justify the craziness of the wildlife present in the planet, as the sole survivors of the receding oceans of Darwin IV.

Here is what I propose:

Millions of years ago, Darwin IV used to be a colder and richer environment, like Earth is.
In it's ever changing tectonic process, the configuration it established would trigger a runaway greenhouse effect - with the combined evaporation of water from now desertified areas and from massive amounts of greenhouse gases released by volcanoes, which seems like it is the case, as there is a massive equatorial array of mountains, and wide spread lava plains throughout the surface, think of something like The Great Dying, but much, much worse, in a way it completely changes the worlds geography over the following million years, that reduces much of the pre-existing biodiversity, leaving only the tips of the tree for us to try put together, so rather than all creatures being closely related, you have pockets of creatures that are closely related, which evolved during or post catastrophe, and these pockets are then not related to each other by millions of years predating the Catastrophe, and now that much of the geographical barriers have been removed, like mountains or even oceans themselves, you have creatures that used to inhabit different parts of the world until a dozen or a hundred million years ago when it all changed, and everything looks radically different from what you would actually expect.

Darwin IV in that sense, would be the same to arrive at Earth sometime in the future and see Tigers competing with Lions and Wolves for Hippos in the Australian outback, or have harpies and flamingos in New Zealand - which still would be pretty relatable on a basal sense.

At first, I thought of making a cladogram of the creatures portrayed, but after facing this possibility, I had to toss idea away - however sometime ago a fellow deviant, Dragonthunders, tried to piece Darwinian biosphere together in a forum thread, and here is the result:

As I said before, it wouldn't be so hard at first, you can clearly relate creatures in groups, but you have to make massive stretches to relate groups between themselves, Darwinian biosphere is paradoxically diverse and at the same time so poor we can't properly relate the aliens with 100% accuracy.

CONCLUSION?

Darwin IV is a poor rendition of Triassic Earth. - M.O. Valent

Discovery's Alien Planet showed itself to be a more artistic work than a work SCIENTIFICALLY VERIFIED BY LEADING EXPERTS as it is advertised - and so far I'm very upset, and my expectations are comically low for the matter, as there will be tons of other material I will have to read with J. Jonah Jameson's spirit...

That's me having to read Expedition now...

- M.O. Valent, 18/07/2020

OTHER CONCEPTS | SPACESHIP DESIGN & SPACE WARFARE | PART 2

MAYBE SPACE IS LIKE THE SEA...
...OR IS IT?

When your enemy fire lasers and don't even have shields

This post is a follow up to my previous one about Spaceship Design & Space Warfare.

After reading some comments on forums about that post in particular, and some other discussions on the theme, I decided to make a follow up post, as an extended argument - exploring in-universe ideas so we make sure we are at least, certain we are exploring the world to it's potential.

Before you all point the phasers and blasters at me, I would like to again state that I'm trying to get Hard Sci-Fi on the matter, ie, try analyze the viability of an aspect, based on what we know today - when talking about in-universe logic, I will do as I often do discuss conspiracy theories and not poke the HOW, but poke the AFTER of an aspect, and try to see if the observed consequences to a certain aspect are really the ones that would apply - ie, in this case, let's just accept it is possible in the first place, and then explore what would actually happen after.

In relation to Star Trek in particular, as I noticed it is an often brought up topic, which is rather, unusual? From my POV at least - I mean, every other universe has it's little bit of "nonsense" (fiction), I personally included Magic and a mechanism in which it is "possible" in my stories, so again, it isn't like I'm a science-nazi - coming back to Star Trek, it is unusual for me that, besides some in-universe stuff makes real sense, some major plot points just don't, like the characters not using spacesuits every time they go on ground missions.

Yeah, let's lay on the soil of a alien planet, just the kind of place that contain most of the foreign and potentially harmful microorganisms possible - after the insides of an alien itself

WHAT WE DISCUSSED IN THE PREVIOUS POST

After taking a look at some problems, and how they could be solved, regarding navigation and protection, I have established 4 rules for spaceship design.

RULE 1

A spaceship will be always under the Newton's 3 laws, and as such, will not suffer friction in space and decelerate if stopped it's engines, and will continuously accelerate if it continuously fire it's engines.

A spaceship should be able to move in all 3 axes, in both negative and positive vectors of those, for stable navigation and positioning in space.

RULE 2

Windows, are a weak spot, no matter what they're made of, what worries is not that they could break, is that they do expose the interior to dangerous radiation, as explained in FTL DEPICTION, near light-speed and faster-than-light travel expose the ship hull to dangerous UV, X-rays and Gamma radiation.

  As well, in cruisers and aircraft carriers, is fairly natural that the majority of the crew do not see the sun for the entirety of the mission - nothing too strange so far. So, little to no windows across the hull, if there is windows, make sure they are slim and can be shielded at any moment.

RULE 3

We don't need an external horizon sense - Up or Down sides of a ship, we would want to make it cylindrical or with as many symmetry axes as we can, to make steering and defense evenly possible across the hull.

RULE 4

Heat is a serious problem. On Earth, vehicles, weapons and people can exchange heat with the environment. In space, we need to deal with irradiation of heat, the ship needs to get rid of extra heat from it's functioning and exposure to sunlight, the problem is to balance the compactness of space ship with the large area needed to irradiate it away at a decent rate.

For this, we would never want to coat our ship in black paint or use dark materials to construct it's hull. Make it visually as bright as possible is the way to go, or at least as reflexive into the UV and Infrared as possible.

Rules 3 and 4 was also kind of applicable to WWI, in the form of Dazzle Camouflage, which disrupts a ship's silhouette at the distance, making it harder to tell direction of movement, or weakpoints unless you observe it for a long period of time, a precious time in war. More on that later.

THE DISCUSSION

Now let's take a look at some points regarding that post.

Rear-facing engines are a N O P E, or are they?

What one is doing when building large rear-facing engines is sacrificing agility for linear acceleration and in some cases this makes sense. 

Ironically, the hard scifi setting that he describes would be one that might favor linear acceleration to some extent. After all if you have several seconds to react to enemy fire then you only need a certain amount of agility. On the other hand, linear acceleration in such a setting is your strategic mobility.

In what way this makes any sense I have no idea, unless both sides agreed to have a medieval jousting, moving only forwards, and the one who shoots first has MORE chance of winning.

whooosh!

In the case of only rear-facing engines, and that you would have several seconds to react, it is true to an extent - except there ain't much you can really do in space in that situation, but to accelerate and rush through the enemy line of fire. Again, it's not the sea, so you don't have tiny little flaps in your ship's hull to steer it in any other direction, so Linear Acceleration isn't really an option.

In the case of the ship having other thrusters, which would be ideal, you have way more options of evasive maneuvers, however, these thrusters should be able to turn or move your ship around within a certain degree of freedom, in which case, if they would be considerably less powerful than your main thrusters, you then just gave your ship a large and predictable turning circle.

Turning circle of the RMS Titanic in a presentation about evading that one iceberg

Giving your ship a large turning radius can be considered a great problem because maneuvers may take on some considerable time, and space that may not be available for your because of the enemy line of fire or physical obstacles.

If the ship has several thrusters of similar power, they can overcome the issue in any direction within the same safe window of time, or at least, rotate the ship in order the evade incoming fire.

Just imagine how many times would Neo have been shot - if his only option was to run towards Agent Smith.

Ships have no real reason to be within visual distances from one another in the...

STAR TREK UNIVERSE

Let's first consider:

- Virtually all ships are capable of superluminal travel (FTL), and tracking objects at these velocities.

- Virtually all ships have some level of energy/force shielding.

Given these factors, it actually make sense that ships would have to get damn near face to face in order to harm each other, look at how dismissive Worf was about that one alien ship using lasers as it’s primary weapons, it implies that they’re near to completely useless against proper shields and that doesn’t even touch on the trek ships just being able to warp out of the way of the laser beam (assuming that they noticed it being fired from a light-second plus range, which I give like 50/50 odds). 

The other big thing about the shields is that the debris clouds from defeated ships become much less of an issue as even the deflector shields (the ones used at warp speeds to keep the ship from getting turned into an expanding cloud of debris by those various hydrogen atoms floating a few feet away from each other) should be able to handle that considering what they’re actually meant to do. 

On the other hand, at much closer distances charged particle weapons become much more effective and devastating as the beam doesn’t have time to spread out as it would over vast distances like it would for light-seconds and beyond and they’re able to carry enough energy to chew away at the opposing side’s shields.

So are we lead to attack at close range because ranged weapons are virtually ineffective against those ships. And somehow they can't really fire relativistic weapons at these distances, when their enemy wouldn't have 2 billionths of a second worth of time to process any data and plan ahead at all... Yeeeaa?

Or the fact that lasers would actually be more useful than charged particle weapons, because photons have no charge, if the shielding blocks the incoming fire through detecting the electric potential of physical projectiles, then yes it would make lasers or photon torpedoes the most efficient kind of weapon against conventional treknology. What again, bring back the relativistic weapons a plus, as it doesn't need to directly hit the target, any sufficient large debris like an asteroid or probe sent with this exact purpose can blast sufficient X-rays and Gamma rays to blind, fry, and overheat the ship's crew and hull.

So yea, the Federation would then opt for maintaining a safe distance in order to avoid being fried by RWs, while also close enough to launch efficient ranged subluminal projectiles.

Given the USS Enterprise lenght is about 642,5m, I'm pretty sure that 2,5km is NOT the UFP's minimum safe engagement distance

Star Trek indirectly states that RWs are a common type of weapon, and the battles take on having thousands of kilometers between ships - so most of the great battles we remember from the movies are abnormal cases.

Except on the case for Star Wars :(


CAMOUFLAGE IN SPACE?
Here is how NASA identifies asteroid sizes:

Different sized objects with varying compositions may be at first indistinguishably at distance, because a larger reflective area with a lower albedo can compensate for a smaller reflective area with higher albedo, however that's how visible light interacts with matter.

In the Infrared spectrum, darker objects absorb more heat energy than whiter objects, and thus, these objects passively glow in infrared to some extent.

Assuming two objects are the same distance from the Sun, and that they are so small their internal heat is negligible. The only thing affecting their temperature is their size and albedo.

Assuming they'd have the same albedo, the larger object has more surface area to receive heat from, and would be hotter.

The problem with camouflage in space is the fact that space is rather full and empty at the same time.
In a way, you can never be fully mix in the environment, you either will emit more energy than your surroundings or be colder than it, either way, they see you.

For perspective, the Voyager 1 uses beamed radio signals directly at Earth to communicate, these beams are only 23W in strenght, as of 2014, when Voyager 1 was at a distance of 100 AU, the signal strength here on Earth was that of a billionth of a billionth of a Watt (≲1 attowatt).
As of 8 june 2020 (today), Voyager 1 is still rather contactable, and at ~148,67 AU the signal is only 45,6% as strong as in 2014.

A relatively light 2.500 ton ship made of steel, 10K above background noise temperature bears about ~3,2MWh worth of energy - from a 100 AU distance to the observer, it's signal would be about 141,7 thousand times brighter than Voyager 1. At 1 AU, the signal strenght is of ~1,4 nW.

Now imagine the massive cruisers in popular sci fi movies, again the USS Enterprise, which weights 4,96 million tons, and as nobody seems freezing inside the ship, I can only assume it is at LEAST about 15ºC, or ~288K, temperature of objects in the Kuiper Belt at 40 AU are no hotter than 50K, at 100 AU then, the Enterprise would be the only glowing object in the Infrared spectrum.

Early 21st century techonology (a.k.a. current tech) can swipe across the skies in a matter of hours - less than an entire day, you don't even need a full celestial scan for this kind of purpose, if you're expecting the enemy to come a particular direction, like the Gas Giants of your system - if they need gravitational assists to maneuver. We can even detect distant planets hundreds of lightyears away using slight variations in starlight.

If an interstellar/interplanetary invasion is a true concern to the world it takes place, you can deploy radars or telescopes in the lagrange points of other planets or in an inner orbit around your parent star, in this way, you can rely on both paralax between your ship's POV and the radar's POV in relation to a target to range it, if we with current technology can spot and track the dimmest objects, a society really concerned with the matter may really make sure it can really know what's up there.

It isn't like we won't notice them coming until they cross the Lunar perimeter.

DISRUPTIVE CAMOUFLAGE IN SPACE THEN?

Based of that, and the fact combats would indeed take place within non-visual ranges, but would still be detectable right away, we can design camouflage add-ons to make way harder to estimate the size and specific shape of the ship instead.

This could be done by either painting the ship or by adding reflective or absorbent panels to the ship, to make it appear smaller or bigger (more distant or more closer) than it really is and thus throw the first enemy shots off by some hundreds or thousands of kilometers. 
Mobile reflective plating could easily flash the reflectivity of the ship with a random stroboscopic effect making it virtually impossible to pinpoint in 3D space within a certain range - making for a real Space Dazzle Camouflage.

The use of this techinique can also counter-shade the ocultation of background stars or celestial bodies, to the point that your ship's passage in front of a star or distant planet can be mistaken with background noise - in which case, you would need to have the slight idea from where they might be watching you so you can beam the light in the right direction.

Other forms of space camouflage could be the releasing volatile chemicals such as ammonia, water and methane - to disguise as a comet, though they would look at you even more because of the new comet.

Navigating on the shadow (blocked part of the sky) of a planet could be quite effective until you're close enough to "rush" towards your target - this would require you to know well the planetary motions of the target system. Like, despite the Enterprise being several orders of magnitude brighter than the Voyager 1 for instance, or brighter than the Kuiper Belt objects, it could pretty much hide behind Jupiter down to 5,2 AU into the system.

Omni-directional radio emissions would be rather stupid as well, a more delicate but safe method is needed, low energy beamed / laser communication would be more viable between ships in a fleet, at sub-AU distances, 24W comms may be even an overkill in energy / data transmission, beamed comms can't be intercepted unless the enemy is in between the transmissor and the receiver, plus into the beam's cone.

And that's all I can think on the topic without being redundant about some obvious factors like the inverse square distance law, or throwing in handwavium hulls.

The thing is, even though you can be detected on the system's edge, there will be probably weeks before you both can engage in any meaningful combat, unless you travel at near lightspeed or superluminal speeds, a couple hours or minutes at least, in which case, all this camouflage thing may be a waste of time if you can just hop in and out range without warning. And even so, it isn't so feasible the combat may occur within more than a Lunar Distance (about 400.000km) away unless at least one side has mastery on RWs.

- M.O. Valent, 09/06/2020