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.

Angel

A low-gravity hexapedal, flight-capable human variant with three limb pairs: manipulator arms, legs, and mid-torso wings. Built for sustained flapping and soaring in ~0.15–0.30 g, Angels retain full hand dexterity and can work and walk in 1 g.

Anatomy & Propulsion Mid-torso wings hinge from a reinforced scapulo-pelvic girdle and a keeled sternum anchoring enlarged pectorals. Wings are multi-segmented and fully foldable, wrapping along the back and flanks for confined spaces. Skeleton is light with selective hollows; musculature favors endurance. Lungs use avian-like flow with air-sac analogs to sustain burst power and long glide phases. Gut volume is reduced; metabolism prioritizes dense fuels.

Operating Envelope In 0.15–0.30 g, Angels can ground-launch, climb, cruise, and thermal/soar; short takeoffs and wing-assisted leaps are routine. Below ~0.15 g, true flight is impractical; wings act as control/braking surfaces in air-filled spaces. In microgravity, partially deployed wings and tail surfaces provide superior body control, stability, and low-energy translation; in vacuum they are inert. Angels function in spin-gravity habitats and can stow wings for ladder, shaft, and suit work.

Costs and Limitations High-energy diet; shortened gut constrains bulky or low-quality foods. Bones are light and more fracture-prone under 1 g impacts; prolonged 1 g work increases fatigue and injury risk. Wings are vulnerable to tearing if unsheathed in cluttered environments. Flight requires adequate air density; performance degrades sharply in thin, turbulent, or contaminated atmospheres. Hydration, sheathing, and conditioning mitigate most risks.

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 fluid-filled.

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.

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.