Three Propellants.
Purpose-Built.
Every mission profile has a different propellant problem. Forge, Ember, and Glacier are each engineered around the job they're built to do, not retrofitted to do all three.
Forge-1
Forge-1 is our sea-level workhorse: an oxidizer-rich staged combustion engine running RP-1 and liquid oxygen, built for the dense, high-thrust job of getting a heavy vehicle off the pad. Seven of them power Horizon's first stage, with deep throttling and in-flight relight for boostback and landing.
| Propellant | RP-1 / LOX |
| Cycle | Oxidizer-Rich Staged Combustion |
| Thrust (Sea Level) | 230,000 lbf (1,023 kN) |
| Isp (SL / Vac) | 285s / 312s |
| Chamber Pressure | 2,720 psi (187 bar) |
| Dry Mass | 1,630 kg |
| Throttle Range | 40–100% |
| Restart | In-Flight Relight |
| Powers | Horizon Stage 1 (×7) |
Ember-200
Ember-200 is a full-flow staged combustion engine running methane and liquid oxygen — the cycle that keeps turbine inlet temperatures lowest while extracting the most performance from the propellant. It's rated for 40 flights and powers both stages of Pathfinder, with a vacuum-optimized variant, Ember-200V, on stage two.
| Propellant | CH4 / LOX |
| Cycle | Full-Flow Staged Combustion |
| Thrust (SL / Vac) | 195,000 lbf / 215,000 lbf |
| Isp (SL / Vac) | 327s / 358s |
| Chamber Pressure | 4,350 psi (300 bar) |
| Dry Mass | 1,480 kg |
| Throttle Range | 20–106% |
| Rated Reuses | 40 Flights |
| Powers | Pathfinder Stage 1 (×9) & Stage 2 (×1, Ember-200V) |
Glacier-90
Glacier-90 is the highest-efficiency engine we build: a closed expander cycle running liquid hydrogen and liquid oxygen, with a long, slender vacuum-optimized bell. It's a single-engine upper stage built for restartable, precision burns — exactly what's needed to hit GTO and cislunar targets.
| Propellant | LH2 / LOX |
| Cycle | Closed Expander |
| Thrust (Vacuum) | 90,000 lbf |
| Isp (Vacuum) | 449s |
| Chamber Pressure | 1,480 psi (102 bar) |
| Dry Mass | 540 kg |
| Restart Capability | Up to 6 In-Flight Restarts |
| Cumulative Burn | 1,100s |
| Powers | Horizon Stage 2 (×1) |
Twelve Stands.
One Site in Huntsville.
Every engine we fly is qualified on the same stands that ran its very first hot fire — sea-level and altitude-simulating cells covering all three propellant families.