Designing realistic mecha and mecha combat

I'm constructing a Real Robot Genre setting that is basically a thematic opposite of Star Wars and Star Trek. The premise of the setting is a galactic-scale civil war between a corporatocratic federation and a network of revolutionaries struggling for independence.

The conflicts of the galactic-scale civil war is fought using Heavy Infantry, a type of heavily armed and armored bipedal Walking Tanks piloted by military personnel. The main role of Heavy Infantry is to mount frontal assaults and hold the defensive center of the battle line.

The main characteristics of a Heavy Infantry fighter are, as of writing:

• Averages between 4-8 meters in height.
• Usually bipedal in nature with hydraulic arms and legs.
• Heavily armored with 'Hyper-Alloy', allowing Heavy Infantry units to resist small arms fire and survive being struck by missiles.
• Use of force-field based shields to absorb the effects of plasma-based weaponry capable of melting metal.
• The use of hybrid nuclear reactors, fueled by Thorium and Helium-3, to power the Heavy Infantry units that generates a continuous electromagnetic pulse field. Engines using diesel or mazut is used by cheaper, low-quality units.

What would realistic mecha combat look like? What would a practical, mass-produced mecha in a realistic setting look like?

I think Armored Core is close to what you're asking about, as a realistic mech sim, but to be more original

I assume that the mecha would more clumsier and less agile, and wouldn't mimic human fighting techniques. I also think they might need more than one pilot per mech, but paradoxicaly the idea gets more play in the more fantastic cousin genre (namely Pacific Rim [afaik] and Franxx).

More obviously I don't think combing mecha is practical in this case transformation might be, but it'd be limited here.

Edited by MorningStar1337 on Oct 14th 2022 at 9:56:10 AM

Ask yourself what battlefield role each mecha model is supposed to fit into. If it's "all of them", you're too far into Master of None territory.

To illustrate, in a setting I'm writing the first mecha model was supposed to be a mobile suit-esque Real Robot with articulate hands and everything but when it was actually put through military trials, it proved to be underpowered, under-armored, undergunned and mechanically unreliable, with the articulate fingers in particular being prone to jamming from the weight load of the weapons they were supposed to hold. The design was sound on paper but the technology itself simply wasn't mature enough at that point.

As a result, the military went "no thanks" and rejected adoption of the mecha. The blueprints subsequently got bought by another corporation who went back to the drawing board and decided to lose the arms and use the resulting weight savings to reinforce the legs, the armor, and use a fixed main armament in the form of an artillery cannon instead of trying to do everything. The result was a machine closer in function to self-propelled artillery than superheavy infantry and utilizing tank tactics like crouching into hull-down firing position behind hilltops, but it worked and was successfully adopted for mass production. It wasn't any better in an urban environment than a tank; in fact, it was even worse because its height made it even more difficult to spot infantry lying in ambush.

The next step was an entirely new model that utilized design cues from the first attempt like articulate hands to hold and use multiple weapon options and even a combat knife for melee, but scaled down into a Mini-Mecha to lessen structural stress, fitted with feet-mounted retractable wheels for faster movement on smooth terrain (and retractable spikes for increased traction on softer ground like snow), harpoons for scaling tall structures and motion-capture controls for the arms instead of something impossibly complex with only a stick. While the Mark II was a two-seater (pilot and gunner) walking artillery for fighting on open terrain (think GDI Titan), the Mark III was a single-seater urban combat IFV with armor primarily designed to stand up to small arms rather than frontline combat. It wasn't meant to replace its predecessor, but to handle a separate doctrinal niche.

A Mark IV also eventually enters evaluation as a replacement for the Mark II, sticking to the same combat doctrine but ditching the armless humanoid shape for a six-legged Spider Tank design for increased load-bearing (and thus armor and weapon loadout) capacity and an overall more stable firing platform.

In parallel a superheavy design also starts to be built, one that uses the lessons of both the Mark II and the Mark III to create a Humongous Mecha that has the versatile humanoid design of the Mark III at a scale factor considerably bigger than the Mark II with Transforming Mecha functionality. It can barely even stand up under its own weight at 1 g - but it doesn't have to because it's designed for aerospace combat, not ground combat. Just like how the Mark II wasn't intended as a tank replacement, this one isn't intended as a fighter replacement either; instead, it's intended to operate as a bomber / gunship with fighter escort. It can dogfight, but not as good as an actual Space Fighter and has a primarily (but not solely) missile-based armament that can launch off-angle anyway, so it's more like an anti-ship Lightning Bruiser than a flyswatter.

In another setting I outlined but haven't gotten around to writing yet, mechas are still primarily urban combat platforms. What justifies their existence was the development of highly efficient and accurate laser-based CIWS that auto-tracks and destroys all incoming high-speed projectiles with enough advance warning, making the mechas near-impossible to kill with artillery, mortars or cruise missiles launched beyond practically spitting distance, barring massively expensive massed bombardment to saturate the flak laser grid with more targets than what it can destroy in time.

The laser grid can also be switched to anti-personnel mode, in which case it automatically and indiscriminately targets and fires upon all human-sized IR signatures in its line of sight without any pilot input required, so attempting to sneak up on it with an RPG to fire from within minimum interception range will get you exploded into Ludicrous Gibs the second you lean out from behind the wall. On the other hand, it bears repeating that anti-personnel mode is indiscriminate because the IR cameras cannot distinguish between friend, foe, or civilians, so it's a friendly fire hazard to begin with and arming it in an urban area is a war crime by international law.

The lasers are not strong enough to harm other mechas and comparatively slower-moving objects like cars don't trigger it either. They will, however, zap the bullets fired by the other mecha, forcing it to either shoot from closer or straight-up go for melee.

@Adept Gaderius As described, combat is going to be a slugfest of ponderous advances and gradually wearing down the enemy's shields.

Personally, I like mechs being used as a kind of combat engineer. Using that dexterity to repair vehicles or clear obstacles and the combination of walking and wheels to travel over a wide variety of terrain.

To elaborate, the Heavy Infantry mechas are designed for mounting frontal assaults and holding the defensive line. These mechas work in conjunction with light infantry, that is lightly-armored conscripted infantry, and armored vehicles such as tanks, planes and space battleships.

The Heavy Infantry redirect attention from enemy fire using its large posture and, in which the heavy armor and force-field shields absorb damage. This allows light infantry and smaller combat vehicles to proceed under the safety. Depending on the equipment and armaments that is wielded or mounted, the Heavy Infantry units would retaliate with salvos in turn.

The major defense mega-corporations manufacture Heavy Infantry units based on standards demanded by the civil war. These Heavy Infantry units are cheaply-made, mass-produced and heavily deployed by the mega-corporations, with certain models and units possessing advanced defense tech such as better armor, longer-lasting shields, and other combat utilities.

Because heavy assaults and holding defense lines often means little to no room to maneuver, Heavy Infantry mechs wouldn't benefit from agility. They might need to withdraw from the frontline to recharge their shields but combat is going to be a drawn out slugfest with each side trying to focus fire to bring down mechs one after another. It's going to look like Napoleonic infantry fights. Basically two lines exchanging blows until one breaks.

As for how they look it'll probably depend on the manufacturing tech and the exact specifications of the weapons.

Other functions of Heavy Infantry units include expeditionary warfare in environments unsuited for conventional military vehicles such as jungles, highlands, and urban environments.

The manufacturing tech is based on mass-production by manual labor assembling components by hand or machining tools, and using smaller piloted machines to assemble the Heavy Infantry units. Such heavy utilization of manual, non-automated labor is the result of distrust and hostility towards automation of industry and artificial intelligence.

The weapons used by the Heavy Infantry units are divided into two types - mounted and portable. Mounted weapons are armaments that are attached to a Heavy Infantry unit, which can only be manually removed by crews, whereas portable weapons are armaments that are carried by Heavy Infantry units, which can be dropped for repairs or reloading.

Examples of mounted weapons include Vulcan rotary cannons, Screaming Mimi rocket launcher, and M114 howitzer. Examples of portable weapons include the 80-watt range plasma rifle, .50 BMG machine rifle, and the revolving mortar.

This is essentially working at cross purposes. For the assault role it's usually better to be bigger and heavier than your opponent as it's assumed that it'll either hold a chokepoint or try to take it.

Maneuvering through rough terrain, however, generally favors lighter designs with lots of horsepower. Take the WW 2 jeep for example. 54 hp for 1 metric ton.

Now you can go ahead and make mechs a jack of all trades but you're going to have to answer why tanks aren't used in the assault role.

In the setting, tanks are used in assault roles, but Heavy Infantry units often substitute for tanks in rough terrain and environments unsuited for tanks such as industrial parks, non-terraformed planets, and montane areas. Most Heavy Infantry battles take place in such environments, especially in rebel-controlled industrial areas and barren planets used for resource extraction.

The deployment of Heavy Infantry units by the government is a response to the rebels hijacking and modifying piloted mechas, originally used for construction and industrial duties, as improvised fighting vehicles.