Horizon Apogee — Orthrus Propulsion
IGNITION‑MACH BOOSTER DELTA
Models the first-stage booster mass required to reach ram/scramjet takeover speed, and shows what that saved mass is worth in additional payload or range.
ΔKE ∝ m·(Vign²−Vlaunch²)
01 — Base System —
Reference vehicle. Defaults reflect X‑51A‑class figures.
02 — Orthrus‑Derived System —
Lower ignition Mach = shorter boost phase = smaller booster.
03 — Cruise Fuel Assumptions —
Drives the Breguet-style range scaling law below. Not the booster propellant — that specific energy is inferred separately.
⚠ L/D and propulsive efficiency above are placeholder figures carried over from the legacy (X‑51A‑class) engine cycle. Orthrus's actual propulsive efficiency at a given Mach/altitude has not been characterized here and may differ meaningfully — treat range outputs as illustrative until Orthrus-specific cycle data replaces these values.
Silhouette height is proportional to system mass, not physical length — illustrative, not to aerodynamic scale.
Explore the Payoff — Same Total Mass
At the base system's total mass (— lb), the Orthrus-derived stack can carry a bigger vehicle: — lb vs. — lb baseline. Drag either slider — they share the same mass budget, so pushing one back gives the other more room.
Logarithmic in mass ratio, not linear — each added lb of fuel buys slightly less range than the last, exactly as a real cruise vehicle behaves.
The payload slider spends mass headroom directly; the range slider spends it as fuel and solves the Breguet equation for the required mass. Moving one automatically gives back mass to the other since both draw from the same fixed headroom (— lb).
⚠ Range figures use the legacy engine's L/D and propulsive efficiency (Section 03). Orthrus's own propulsive efficiency has not been independently characterized and may differ — these are placeholder, not measured, values.
Method Notes booster scaling · range law · disclaimers
Booster scaling. Booster mass is scaled on the kinetic energy the booster must impart to the stack: ΔKE ∝ m · (Vign² − Vlaunch²), holding effective propellant energy density, structural fraction, and drag/gravity losses constant between the base and Orthrus cases. First-order approximation — it does not independently model burn time, boost-phase drag, or how booster structural fraction shifts at very different booster sizes.
Inferred specific energy. Back-calculated from the base case as E = ½·mvehicle·(Vign²−Vlaunch²) / mbooster. This is a delivered/effective figure (net of booster structure mass, gravity and drag losses), not the raw chemical energy density of the propellant.
Range scaling. Uses the energy-equivalent Breguet range equation with an effective exhaust term efuel·η/g in place of specific impulse. First-order cruise estimate, not a full mission trajectory.
Legacy efficiency disclaimer. L/D and overall propulsive efficiency (Section 03) are placeholders inherited from the legacy X‑51A‑class engine cycle, chosen only to make the range law computable. Orthrus's actual propulsive efficiency across its Mach/altitude envelope has not been characterized here and may differ meaningfully from a conventional scramjet cycle — range outputs should be treated as illustrative, not predictive, until real Orthrus cycle data is substituted.
Speed of sound. A single value is applied to both cases so the Mach-based ratio stays self-consistent; change the altitude preset if ignition/launch happen at meaningfully different conditions.