ASM-180A Damocles II anti-satellite missile

Two ASM-180A Damocles II carried on underwing pylons of Boeing 747-3 Trijet
ferry and launch aircraft

The ASM-180A “Damocles II” is a rocket-propelled, three-stage, air-launch-to-orbit (ALTO), quick responsive anti-satellite (ASAT) weapon designed for captive-carry and launch from an underwing pylon or under- or over-fuselage mounting point. It is a fully autnonomous launch and leave weapon with a telemetry datalink to allow assessment of mission success. The launch aircraft carries the rocket into the upper stratosphere above conventional weather that can affect safety and reliability. The air launch technique has no azimuth constraint allowing placement into any target orbit and inclination without fuel and energy depleting dogleg manoeuvres required by a direct ascent launch profile. The aircraft orbits in a “race track” pattern to line up with the launch azimuth and releases the rocket at an optimum drop point that is ~10% of the altitude with ~5% of the delta-V required to achieve a generally stable orbit. The operational coverage allowed includes low Earth (~500-1,200 km), heliosynchronous (~600-800 km), medium Earth (5,000-20,000 km) and geostationary/geosynchronous (~36,000 km) orbits. The missile is a carrier rocket for a dual payload of 120 kg (264½ lb) independently manoeuvering hit-to-kill MK 2 “Damocles” Orbital Kill Vehicle (OKV-2) that allow a multiple intercept capability targeting two satellites in the same orbital plane e.g., a high value target and a co-orbiting defensive satellite (DSAT), or increase kill probability against a repositionable or manoeuvrable spacecraft. It can be launched at short notice requiring only a few hours to complete mission preparation including the updating of trajectory software with the orbital elements of the target. High launch cadences are possible with rapid turn around times of the launch aircraft to provide a high volume of fire for the rapid attrition of satellite constellations.

Background and development

The ASM-180A is a third-generation ASAT weapon developed by Aerodyne Inc. as a successor to the ASM-179A Damocles based on a license-built derivative of the ASB-11A Pegasus XL small launch vehicle (SLV) developed in the 1990s by Orbital ATK in a captive-on-bottom launch configuration. The goals of the Damocles II program was to achieve higher reliability, maintainability and availability (RMA) to reduce costs and signifcally improve tactical flexibility and operational responsiveness. The ASM-180A achieves these goals by a simplification of system architecture from a winged booster requiring carriage under the belly of a specially modified aircraft and pre-launch processing (payload integration and fueling of the upper stage) in ISO Level 8 (100k class) clean room conditions, to a ready-to-fire all-up-round (AUR) i.e., fully assembled missile configuration that can be quickly mated to a launch aircraft on the flight line. The rocket has a 0.55 propellant mass fraction for high performance, using both solid propellants and hybrid propellants that allow safe storage to wait for activation at an intentionally unknown time, and a reduction of ground handling infrastructure and crew to increase the number of sites the weapon can be deployed from.

Description

Missile

The ASM-180A is released at a drop altitude of 13,716 m (45,000’) at a speed of Mach 0.8 at the apogee of a parabolic arc in a 30° pitch-up angle to reduce delta-V, free-falling for five seconds to ensure safe separation from the aircraft before ignition of the first stage motor to begin the cilmb-out into orbit. It is a three stage rocket with a constant cylindrical wingless airframe consisting of two single-pulse solid-propellant rocket motor stages, a third restartable and throttleable hybrid-propellant rocket motor upper stage, and a spacecraft bus with dual manoeuvrable kill vehicle payloads. Cruciform clipped-tip delta stabilising fins are positioned at the base of the first stage and a clamshell aerodynamic fairing encapsulates the upper stage and spacecraft bus. It has a has an overall length of 24.08 m (79’) and a launch weight of 21,545.6 kg (47,500 lb) with the rocket motor casings, interstages, fins and fairing constructed from filament-wound carbon/phenolic (CP) composite monoqoque structural shells of high stiffness/weight ratio and thermal stability. The rocket nozzles comprise a carbon/phenolic exit cone with carbon-carbon (C/C) throat lining of low ignition loss rate and good ablation profile. All three stages are naturally unstable and are actively stabilised and steered by a thrust-vector control (TVC) system using direct-drive electric actuators to gimble the engine nozzle to provide pitch and yaw control.
The first two stages are powered by high performance solid-fuel rocket motors loaded with a castable high-energy ammonium perchlorate composite propellant (APCP) consisting by weight 8% powdered aluminium (Al) fuel, 55% ammonium perchlorate (AP) oxidizer and 17% polybutadiene acrylonitrile (PBAN) fuel-binder. They consist of the Aero 60-1 first stage which is 12.5 m (41’) in length and 1.52 m (60”) in diameter with a 1.83 m (72”) finspan powered by an air-ignitable motor for air-drop launch; and the Aero 50-2 second stage which is 9.15 m (30’) in length and 1.27 m (50”) in diameter with a vacuum-ignitable motor of increased expansion ratio for high altitude performance. The upper (third) stage is powered by a hybrid (mixed solid and liquid-fuel) rocket motor loaded with a long-term storable propellant formulated by weight from 72% ammonium dinitramide (ADN) oxidizer, 16% lithium hexahydridoborane and aluminium (LHA) in a powdered suspension as fast burning fuel and 12% polydicyclopentadiene (PDCPD) as a polymeric hydrocarbon fuel-binder. The highly reactive fuel is manufactured with a microencapsulating agent that prevents premature reaction with foreign sources allowing safe storage and handling. It consists of the Aero 48-3 third stage which is 2.13 m (7’) in length and 1.22 m (48”) in diameter with a restartable and throttleable vacuum motor allowing multiple engine startups/cutoffs and throttlling to provide orbit injection and circularisation, two impulse Hohmann transfer orbit and phasing, and velocity trim for accurate placement into an engagement basket to intercept a single or double target.
The digital avionics architecture is based on silicon-on-insulator (SOI) technology consisting of radiation-hardened microprocessors and logic-based controllers, and radiation-tolerant memory, Flash storage and SpaceWire avionics buses. The processors run DO-178C certified mission-critical software in a VxWorks deterministic, priority-based preemptive real-time operating system (RTOS) environment. The flight control/mission computer is hosted on the spacecraft bus consisting of a low-power compact PCI Meteor Single Board Computer (SBC) with 32-bit MPC8548 PowerQUICC III processor, 2 GB of SDRAM and 1 GB of Flash memory. The computer provides pre-launch checks and guidance and control through ascent and during on-orbit operations, optimizing energy (fuel consumption) while manouevering, and continuously monitoring the vehicle's health and performance throughout the mission. The guidance and navigation and control (GN&C) systems uses a Kalman filter to process mixed pure inertial, GPS-only, and blended GPS/INS navigation data inputs from a Honeywell Space Integrated Global Positioning System/Inertial Navigation System (SIGI) to provide the required target placement accuracy corrected for errors.

Kill Vehicle

The MK 2 “Damocles” Orbital Kill Vehicle (OKV-2) is 1.83 m (6’) in length and 0.61 m (24”) in diameter powered by a single solid propellant rocket motor with a high expansion ratio main nozzle. It is a kinetic energy warhead containing no explosive content except for any residual fuel at the time of impact. It has four divert control system (DCS) and six attitude control system (ACS) nozzles redirecting hot engine gas using ‘bang-bang’ on/off valves to provide quick responsive roll, pitch and yaw control authority. The avionics system is based on a Honeywell Spacecraft On-Board Computer (OBC) with radiation-hardened 32-bit PowerPC 603e processor (RHPPC) with 32 MB SRAM and 4MB EEPROM. It generates non-linear six-degrees-of-freedom (6DOF) adaptive control laws derived from a linear quadratic regulator (LQR) with additional linear quadratic integration (LQI) for orbit injection and course corrections, and high-order sliding mode (HOSM) guidance laws for end game guidance. It processes input from a three-axis strapdown inertial navigation system (SINS) comprised of accelerometers and gyroscopes to provide attitude, velocity and position data, and a laser imaging, detection, and ranging (LIDAR) terminal homing system consisting of a transmitting pulse laser source, transmitter optics, receiver optics, and photodetector. The latter can acquire target images against the cold space background with far field search (~20 km) with target recognition by processing three-dimensional point cloud data and collect range and velocity data with near field accuracy (<100 m) to compute the final hit-to-kill intercept trajectory. Precision manoeuvering allows extremely accurate application of kinetic energy in body-to-body contact to allow destructive and non-destructive effects to minimise fragmentation debris and risk of Kessler syndrome. Using a low speed collision a target satellite can be deflected into an unusable orbit or attitude where it is unable to effectively use instruments, antennas and photovoltaic cells, or into a lower orbit where aerodynamic drag will induce it to naturally deorbit.

Carrier Aircraft

The dedicated air launch platform developed for the ASM-180A is a special mission aircraft based on the Boeing 747-3 Trijet widebody air freighter that can self-deploy with up to two weapons (one under each wing) for a total of four kill vehicles. The airframe is based on the shortened fuselage and low mounted high aspect ratio swept-back wings of the 747SP (Special Purpose) variant developed for long range and high frequency operations. The aircraft is modified from a quad to trijet configuration with two under wing engines and centre aft engine fed by a dorsal S-duct intake ahead of the tailfin. The wings are redesigned with repositioned pylons (described below) and leading edge Krüger flaps, trailing edge Fowler flaps and raked wingtips (winglets) to better optimize lift and fuel efficiency to retain extended operations (ETOPS) certification with only three engines. The pylon adaptors are mounted inboard of the engine pods with wide clearance and mechanical and electrical interfaces for captive-carry and launch of air launched rockets up to 22,679.6 kg (50,000 lb) in mass. The fuel system is modified for drop operations with a dynamic load balancing system to improve aircraft stability. It uses cross-feeds to transfer fuel between main, wing and tail fuel tanks for optimum control of the centre-of-gravity (CG) to compensate for asymmetric loads during carriage and undesirable yaw during drops.
The aircraft has a high strength-to-weight ratio composite and aluminium alloy honeycomb semi-monocoque i.e., stressed skin fail safe fuselage, and cantilever wings and tailfin and variable incidence tailplane on the empennage. Airframe modifications include removal of all interior fittings and equipment from the main cargo deck and underfloor cargo holds to save weight, structural reinforcement of the fuselage and wings to sustain high loadings, and fitting of strengthened landing gear with larger tyres for operation from austere runways. The powerplants are three General Electric GEnx-2B67 dual rotor, axial flow, high-bypass turbofan engines. They provide propulsion and bleed air for ground power i.e., engine starting for self-deployment, cabin ventilation, pressurisation and air-conditioning, anti-icing, de-icing, and ice protection systems, and in-flight electrical power to avionics and mission equipment. The aircraft has substantially analogue hydromechanical primary controls i.e., cables, pushrods, etc, on the elevator and airelon systems boosted with electric flaps, with only the engines having digital fly-by-wire controls provided by BAE FADEC 3 engine control units.
Flying controls are duplicated for both crew, consisting of a steering column with yoke, twin rudder pedals and dual throttle quadrants for responsive but full-time flying. The flight deck is a two-crew ‘glass’ cockpit with an electronic flight instrument system (EFIS) with six 8-by-8-inch LCD displays that show primary flight and navigation data and two 20-inch LCD displays showing aircraft annunciators. Three triple independent flight control computers and dual digital air data computers include autopilot and flight director to reduce pilot workload. The avionics suite includes a Rockwell Collins multiscan weather radar, Class 2 terrain collision avoidance system, transponder and GPS navigation systems, radio beacon and GPS landing systems, multiband digital radio communication system and aircraft intercom. Missions are managed from a two-crew launch control centre (LCC) aft of the flight deck with MIL-STD-810G ruggedized crew stations with 32-inch IPS-LCD displays and high performance computers in 19-inch 5U rack mounts.
The classic 747 upper deck is configured with crew comfort and rest facilities to reduce fatigue including a self-service galley, four-bunk crew crew rest area and aircraft lavatory. Crew survivability is enhanced by standard safety equipment with inflatable evacuation slides and liferafts that deploy from doors and personal survival gear stowed in the cabin, and aircraft survivability by an airborne missile protection system (AMPS) that can detect, classify and counter multispectral (infrared, laser and radar guided) missile threats.

Operators

Etoile Arcture

• Etoile Arcture Aerospace Forces

The Great state of Joseon

• Royal Joseon Air Force

Rapaldegia Bagazis

• Bagazian Air Force

Monavian Empire

• Monavian Royal Space Corps

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Guided missiles of Etoile Arcture

Air-to-orbit	ASM-179A Damocles - ASM-180A Damocles II
Air-to-air	AIM-221A Loki - AIM-222A Ambush - AIM-255A Sledgehammer
Air-to-surface	AGM-189B/C Scimitar - AGM-220A Tiamat - AGM-223A Ajax - AGM-224A/B/C/D Nemesis - AGM-225A/B/C/D/E Locust - ADM-240A Razorback
Surface-to-air	MIM-191B (SL) Krait - RIM-191B (VL) Sea Krait - FIM-192A Scorpion - RIM-199A Xyston - RIM-201A/B Tempest - MIM-201B Tempest - RIM-202A/B Typhoon - MIM-202B Typhoon
Surface-to-surface	FGM/MGM/RGM-189A/B/C Scimitar - MGM-195A/B/C/D Banshee - BGM/RGM-223A/B Ajax - UGM-223A/B Sub-Ajax - BGM-224E/F Nemesis - BGM/RGM/UGM-225A/B/C/D/E Locust - RUM/UUM-239B Cyclone - RGM-241A Muraena