Posthuman Genetic Modifications (IF)

Hard Science-Fiction Setting

Posthuman genetic modifications are way beyond cosmetic or regrav facilitation, these are invasive changes that take months to achieve and learn the proper use of. All these are modifications applies to a baseline human using gene therapy and surgery. None of them breed true. The Earthforce Medical Service (EMS) is very strict about not allowing the creation of new human sub-species. Such may exist in secret in some habitat, but would have trouble passing any security inspection.

These models of modification are actually quite rare; most genetic posthumans have a number of smaller modifications answering to their specific needs.

Angel

A low-gravity hexapedal, flight-capable human variant with three limb pairs: manipulator arms, legs, and mid-torso wings. Wings hinge from a reinforced scapulo-pelvic girdle and a keeled sternum; they fold flat along back and flanks for confined spaces. Skeleton is light with selective hollows; musculature favors endurance; lungs use avian-like flow with air-sac analogs; a shortened gut prioritizes dense fuels.

Angels function well in spin gravity and can stow wings for ladders, shafts, and suit work. Angels can hover in the middle air of spin habitats and quickly descend the gravity gradient using a compact round brake chute in a waist pack; the chute bleeds speed while the wings handle steering, flare, and landing. Faster and lighter Angels are superlative “middle-air supervisors” for open-volume patrol and response.

Socially, Angels read as different without feeling odd: human face and hands, graceful posture, and a name that softens first impressions. Crews adapt quickly; etiquette centers on wing sheaths in tight spaces.

Operating envelope: Below ~0.15 g, partial wing deployment provides excellent body control, the wings only act as control/brake surfaces. In 0.15–0.30 g Angels can ground-launch, climb, cruise, and soar, requiring more effort in higher gravity in this range. Above ~0.30 g the wings assist steering and flares but cannot sustain takeoff; use a brake chute for landings. Around 1 g angels can only steer if they have a chute; on land they move well but tire quickly. In water, they have more drag and less power than baseline; they really don't work well here. In a vacuum the wings are inert; angels fly only in human-made air.

Costs and limitations: High-energy diet; poor tolerance for bulky/low-quality foods; light bones increase fracture risk under 1 g impacts; prolonged 1 g work raises fatigue and overuse injuries; unsheathed wings tear in clutter; flight performance depends on adequate air density and drops sharply in thin, turbulent, or contaminated atmospheres.

Kobold

A high-gravity/standard-gravity posthuman optimized for endurance, load-bearing, and impact tolerance. Compact and low-slung, with dense bone, heavy musculature, and a supporting tail that acts as a stabilizer rather than a grasping organ. The tail widens stance in gravity, provides a third anchor under shock or load, and serves as a counterweight; in microgravity it works as a reaction tail for orientation and bracing.

Kobolds exhibit reptilian traits: scaled integument resistant to abrasion, heat, and solvents; thickened nails and broad hands for traction and tool grip; skull ridges that mitigate impacts. Facial expressivity is muted by the integument—a social handicap rather than a threat cue—so Kobolds rely on posture and deliberate gestures to emote.

They thrive in 1 g and above, excelling at heavy labor, breaching, and armored suit work. Cardiovascular reinforcement raises everyday working comfort to roughly 1.4–1.6 g, with heavy shifts to ~1.8 g, short tasks at 2.2–2.5 g, and brief harnessed bursts to 4–5 g without injury. As pilots with modern countermeasures they tolerate slightly higher +G envelopes than baseline.

In habitats Kobolds gravitate to the lower decks and steep-gradient spokes where others tire or grow disoriented. Their dense build, vertigo tolerance, and cardiovascular reinforcement let them work comfortably in sectors with 1.2 g and above, such as the industrial sub-surface levels of small habitats. These zones are low-status, and their association with underdecks and slums reinforces prejudice despite their reliability. Baselines view them as essential but unglamorous, a contrast to the Angels circling in the middle air.

Culturally, Kobolds are seen as dependable but alien. In Jovian polities their superior high-g tolerance in cockpits and assault roles provokes prestige anxiety and gatekeeping from baseline elites, feeding prejudice despite their utility.

Operating envelope: in microgravity kobolds can use their tails to orient their bodies, this helps them work at baseline despite their heavy builds. Low gravity is their worst gravity interval, they heavy bodies jump and balance poorly. Kobolds thrive from 1 g up to 1.3 g and can tolerate up to 4 g for limited periods. They sink in water, but as long as they remain moving they operate at just under baseline.

Costs and Limitations High metabolic demand; reduced sprint speed and agility; poor swimmer. Light expressivity can impede social rapport. Tail and scales pose snag/abrasion risks in cluttered spaces.

Lemure

A microgravity posthuman built for spacecraft and freefall habitats. The body is light and long-limbed, with grasping hands and feet and a prehensile tail for anchoring and maneuver. Large forward-facing eyes and a tuned vestibular system give precise orientation in three dimensions; fine tactile filaments on the skin provide contact feedback. Appearance reads as slim, big-eyed, and tailed — some call it goblinlike.

Lemures excel at clambering, bracing, and rapid translation in microgravity, and remain competent in Low Gravity (0.15–0.35 g). In Earth Standard Gravity they fatigue fast and are poor at heavy load-bearing. Vision is low-light biased: bright sunlight or a glowing spin axis causes glare and delayed adaptation; visors and baffled lighting are routine kit.

Operating envelope: in microgravity the Lemure use their prehensile tail, handlike feet, and brachiation-like movement to best advantage, making them fast and precise. Low gravity strains their endurance, but they retain much of their agility; if there is enough clutter they can branchiate. Earth standard gravity is not friendly to Lemures; they tire quickly, they are still limber but can't branchiate like the much smaller animal they are named after. In water they are near-baseline—buoyant and comfortable at the surface, but inefficient at depth.

Costs and limitations: reduced 1 g endurance, light sensitivity in unbaffled illumination, and snag risk for tail in cluttered spaces.

Melusine

An aquatic human modification for long-duration work in high-pressure oceans, including Earth’s abyssal zones and alien seas (e.g., Europa). Retaining separate legs, Melusines use fin-like feet for propulsion and control. Oxygen is extracted from water via trailing branchial fans—vascularized, skirt-like arrays that grow continuously and expand under hypoxia; in dry or hazardous conditions they remain short or retracted.

To survive extreme pressure, Melusines employ collapsible lungs that are deflated before submersion, eliminating internal air volume and shifting respiration to the external fans. Residual gases are absorbed via a high-perfusion pulmonary interface, preventing nitrogen narcosis and decompression sickness (no pressurized gas is breathed at depth). Internal air cavities (e.g., sinuses) are filled with fluid.

Melusines excel in deep-sea mobility, temperature/pressure tolerance, and sustained submersion—making them suited to subsurface exploration and aquatic colonization. They operate near-baseline in low gravity and have a slight advantage in microgravity due to low inertia and stabilizing control surfaces.

Operating envelope: in microgravity Melusines benefit from the three-dimensional orientation they use under water, but tend to oversteer when using their feet fins. At low gravity they are hindered by fins and their branchial fans, but they carry their weight well. At 1g, they are hindered like in low gravity but more seriously they have trouble carrying their weight unsupported by water in such a heavy gravity. They thrive in water, maneuvering readily and resistant to pressure and cold.

Costs and Limitations: High-energy diet and high ambient moisture requirements; reduced mobility and fatigue risk in 1g; respiratory fans are vulnerable to desiccation and abrasion when exposed; bones are light and somewhat fragile (though not critically so). Standard environments remain usable via lungs and protective gear, but prolonged dry exposure without hydration/sheathing degrades performance.

Satyr

A low-gravity surface specialist for airless worlds. Satyrs keep near-human stature and proportions but carry strengthened lower limbs and goat-like split hooves for traction on rock and cut faces. Long elastic tendons store and return energy for efficient bounding; ankles and knees are reinforced for repeated ballistic hops. A short, non-prehensile tail and tuned vestibular system stabilize attitude in flight; dense hoof keratin and pads shed abrasive dust. Soft, close leg hair insulates joints without snagging suits; small horn buds and slightly pointed ears mark them as posthuman without drifting into the uncanny. Official designation: Satyr; polite colloquial: faun.

Built for low-g operations (~0.15–0.40 g), Satyrs clear rubble fields in long, controlled arcs, plant tools with sure footing, and climb steep cuts like goats. Hands stay fully dexterous; torso mass sits low for balance and fall safety. Socially they blend into mixed crews; “faun” styling shows up as personal fashion, not a separate culture. Their legs enable stationary vaults and rhythm hops even in 1 g.

Satyr field gear is built around the feet. Satyr-spec vacuum boots complement the natural hoof on regolith, ice, and broken ground—widened dust-shedding soles with tunable stiffness, microspines/sipes, inflatable pads for regolith, and spikes for ice. These boots can be worn without a suit, but the bare hoof handles most habitat terrains on its own. Vac suits also integrate microthrusters at the center of mass for mid-arc trim and landings, with seals, gaiters, and anti-static coatings as standard.

Operating envelope: excels on airless low-g surfaces and in dust-choked cuts; adequate in microgravity (prefers tethers/rails for translation); serviceable in 1 g but slower and knee-limited for sprints and long treks; sligltly below baseline in aquatic settings.

Costs and limitations: terrain surprises can injure on landing; knee/ankle overuse risk in 1 g; poor swimmer; continuous dust management; bounding is unsafe in windy atmospheres with crosswinds.