STABILO

Stabilo was a suborbital manned spaceflight platform engineered by ArcaSpace to be launched from the stratosphere utilising the world largest solar balloon produced by ArcaSpace

The development of the Stabilo program commenced at ArcaSpace following the conclusion of the Ansari X Prize Competition. The platform was designed around an innovative tractor rocket engine configuration, placing the crew capsule at the rear of the vehicle to maximize pilot safety and abort capabilities.

Architecture & Innovation

Tractor Engine Configuration

The vehicle featured a forward-mounted monopropellant rocket engine. By exhausting reaction gases away from the airframe structure at a 20° nozzle angle, the tractor configuration enabled maximum crew safety during all phases of flight. Although the nozzle vectoring resulted in a minor 6% thrust loss, ArcaSpace engineers prioritized maximum abort safety—compensating for the thrust delta with an increased propellant mass and longer burn duration.

The propulsion system utilized hydrogen peroxide (H2O2) monopropellant, yielding a 100% eco-friendly reaction that decomposes purely into oxygen and superheated water vapor.

Composite Pressurized Fuel Tank

Constructed entirely from high-strength composite materials, the spherical fuel tank was pressurized with nitrogen. In this unique architecture, the monopropellant rocket engine mounted directly onto the primary fuel tank structure.

Reaction Control System (RCS)

For attitude control in the vacuum of high altitude and near-space, Stabilo utilized an RCS network consisting of 6 cold-gas nitrogen thrusters.

Pressurized Crew Capsule & Abort System

By placing the capsule at the base of the stack, the abort protocol was significantly simplified: in an emergency, the crew capsule could gravitationally detach from the rocket booster and deploy its independent recovery parachute.

Internal Environment: Pressurized at 0.8 bar, featuring integrated navigation, flight control, and life-support systems (LSS).
Visibility & Access: Equipped with three panoramic portholes for pilot visibility and a lateral, auto-pressurized hatch operable from both inside and outside the craft.
Re-entry Aerodynamic Stabilizer: A specialized parabolic structure mounted atop the capsule automatically stabilized the craft during atmospheric re-entry, reducing pilot workload to a minimum.

Flight Sequence

Stratospheric Launch: Transported over a 1h 45min ascent under a 12,400,000 ft³ (350,000 m³) solar balloon to a launch altitude of 76,000 ft (23,000 m). Launch occurred vertically, releasing directly through the thin balloon envelope.
Powered Ascent: Upon ignition, the vehicle accelerated on a steep vertical trajectory, reaching a maximum velocity of 3,960 ft/s (1,200 m/s) while limiting acceleration loads to approximately 4g.
Inertial Climb & Separation: Following engine shutdown, the crew capsule separated from the booster stage. The RCS controlled capsule orientation as the vehicle climbed inertially past an apogee of 100 km (suborbital space).
Atmospheric Re-entry: The RCS oriented the capsule heat-shield-down during initial entry. As dynamic pressure increased, the top aerodynamic stabilizer maintained passive vertical alignment.
Recovery:
- Booster Stage: Main parachute deployed at 4,000 m at a speed of 400 km/h.
- Crew Capsule: Main parachute deployed at 4,000 m at 350 km/h, securing a gentle touchdown speed below 7 m/s.

Stabilo Technical Specifications

Length: 6 m
Diameter: 1.3 m
Launch weight: 1,000 kg
Thrust in vacuum: 3,000 kgf
Engine start altitude: 23,000 m
Propellant: HP 70%
Maximum speed: 1,200 m/s
Maximum altitude: + 100 km
Boost acceleration: 4 g
Reentry deceleration: -4.6 g
Crew: 1

Stabilo Flight Milestones & Mission History

Mission 1 - December 2, 2006

Launched on December 2, 2006, Mission 1 utilized what was at the time the world's largest solar balloon to lift the Stabilo crew capsule to an altitude of 48,200 ft (14,700 m).

The launch, flight profile, and maritime recovery executed flawlessly, proving the reliability of ArcaSpace's flight avionics and parachute recovery systems. The mission successfully demonstrated ArcaSpace's capability to transport and safely recover a payload from above 85% of the Earth's atmosphere. The vehicle traveled 42 miles (68 km) from its launch point and the event was broadcast live on national television.

Stabilo 1B Evolution

Following Mission 1, ArcaSpace developed Stabilo 1B. The revised architecture transitioned to a traditional pusher engine configuration, allowing for reduced fuel consumption and integration of a higher-performance thermal rocket engine, while retaining the proven composite capsule and tank designs.

Stabilo 1B Technical Specifications

Length: 6 m
Diameter: 1.3 m
Launch weight: 1,000 kg
Thrust in vacuum: 3,600 kgf
Engine start altitude: 23,000 m
Propellant: HP 70%
Maximum speed: 1,200 m/s
Maximum altitude: + 110 km
Boost acceleration: 5 g
Reentry deceleration: -5 g
Crew: 1

Stabilo 1B Flight Milestones & Mission History

Launched from the Cape Midia Air Force Base, Mission 2 was executed in close operational coordination with the Navy, Air Force, and Civil Aviation authorities.

The carrier solar balloon system ascended to an altitude of 39,400 ft (12,000 m). Following a 90-minute mission profile, the Stabilo 1B vehicle was located on the sea surface by the Navy vessel Saturn, guided by real-time satellite telemetry links and Air Force radar tracking.

Stabilo