Type: High Altitude Long Endurance
Program:Powerplant: 1 x 60 kW (65 bhp max, derated from 80 hp) Rotax 912,
later 1 x 100 hp Rotax 914 piston engine
Significant date: 27 April 1993 (D-1), 23 August 1994 (D-2)
In the early 1990s, while the Air Force was working on endurance UAVs for reconnaissance applications, the US Ballistic Missile Defense Organization (BMDO, now the Missile Defense Agency, or MDA) initiated the RAPTOR (Responsive Aircraft Program for Theater Operations) ballistic missile defense program. The idea was to use a high-altitude long-endurance (HALE) UAV to orbit on the edges of a battle area and detect launches of short-range theater ballistic missiles (TBMs). The UAV would then perform a "boost phase intercept (BPI)", shooting down the TBMs in the boost phase with extremely fast "hypervelocity" interceptor missiles named Talon. The RAPTOR/Talon theater ballistic missile defense concept was invented by Dr. Nicholas J. Colella from Lawrence Livermore National Laboratory (LLNL) and now Chief Technology Officer and an Executive Vice President of Angel Technologies Corporation.
The first aircraft developed by the BMDO was the RAPTOR/Talon demonstrator, which was designed and built by Scaled Composites for the program, and initially designated the Model 226 Quiver, although the Raptor name soon took precedence. This high-altitude long endurance UAV program began with a contract award from LLNL to Scaled Composites on June 5, 1992. The company was responsible for the airframe design and fabrication, while subcontractors RPM and TMS developed the two-stage turbocharger system that provided air at near sea level pressure to the Rotax 912 aero-engine at cruising altitudes above 60,000 feet (18 km). Additionally, Scaled was responsible for the design, manufacturing, and development of the high-altitude propeller system, a 2-blade all-graphite controllable pitch unit. Program executor Lawrence Livermore installed a computerized data acquisition system on the altitude chamber for engine tests along with technical support during engine build up. LLNL also supported development of flight control computers to provide navigation and autopilot functions.
The Demonstrator was a conventional cantilever wing monoplane with twin canted vertical tails. It was constructed entirely from composite materials. A ground station was equipped with a two-way radio link to remotely control the Demonstrator and to monitor aircraft health and status information that was telemetered back. When fitted with its high altitude engine, the Demonstrator was launched from atop a vehicle. This was an effective means of providing ground clearance for its 14 foot propeller and gave more flexibility for takeoff aborts. The UAV landed unpowered, with the prop stopped in the horizontal position, on a pair of weight-saving belly skids. In order to satisfy rigorous performance criteria of flight up to 65,000 ft and 48-hr plus endurance, a high fuel fraction and light weight composite structure were necessary.
The UAV (which in fact was an OPV) was designed to carry a 68 kilogram (150 pound) payload of infrared search and track sensors, plus two 22.7-kilogram (50 pound), kinetic-kill, hypervelocity Talon missiles, each with a range of almost 100 kilometers (60 miles). The structure is the same type that was used on the record setting around-the-world Voyager aircraft. The wings and fuselage were oven cured prepreg graphite tape with honeycomb core. In order to minimize tooling costs, the fuselage was a simple slab sided shape cut from flat honeycomb and graphite panels. Scaled also designed, developed, and tested all Raptor flight controls, including autopilot, autonomous navigation, and emergency recovery systems.
In addition to the search and tracking sensors, the UAV was designed to carry two small hypervelocity guided missiles named Talon (Theater Application - Launch On Notice). The Talon was to have a maximum range of 145-200 km (90-125 miles) at a speed of Mach 9. It would cruise at 450 km/h (280 mph) and 20,000 m (65000 ft) for 50 hours. It would be guided towards the target by the RAPTOR UAV and use its own seeker for terminal homing. The missile was to be a "hit-to-kill" vehicle without an explosive warhead. Despite these performance figures, the Talon was to weigh no more than 18 kg (40 lb). In the end, no actual Talon missiles were built and flown before the RAPTOR/Talon program was terminated. At some point, Israel had joined the USA in researching the RAPTOR/Talon project, and even considered a UAV BPI concept, but then decided it made more sense to target the launcher rather than the missile, an approach termed boost-phase launcher intercept.
As the BPI (Boost Phase Intercept) concept included optical sensing of rocket plumes from low altitudes (2 km) through burnout from an air vehicle at 18-20 km, at a long range (i.e. approx. 20-100 km), the presence of clouds could interfere with optical sensing, the Institute for Defense Analyses was asked to estimate the Probability of a Cloud-Free Line of Sight (PCFLOS) at locations and times of concern for the RAPTOR/Talon. . After some counter-intuitive estimates which provided varying results, discrepancies were addressed, and the PCFLOS was determined for paths from 18 km altitude above all clouds to 2 km, at a slant range of about 20-100 km at two extremely different locations (Baghdad, Iraq, and Seoul, Korea) for January and July at average cloudiness. Estimates made by a variety of methods were generally consistent with this finding.
Scaled Composites and Lawrence Livermore took the Demonstrator from final design through fabrication to the first test flight in under a year. The first flight of the Raptor occurred April 27, 1993, just ten months after contract award. Funds expended at this point were only about $800,000. Initial flight testing used an unmodified normally aspirated Rotax 912 engine with a 3-blade fixed pitch propeller, but in order to reach altitudes of 65,000 ft, the Raptor used a two-stage turbocharged, 100 hp (some sources give 80 hp), highly modified horizontally opposed four cylinder Rotax engine modified to operate with twin turbocharging in series with an intercooler. This propulsion package was successfully tested in an altitude chamber to over 70,000 ft altitude.
Concurrent with low altitude test flights, LLNL and Scaled Composites taxi tested the high altitude engine and prop atop a truck at typical flight speeds. During initial tests, the airplane was flown in a manned "Safety Piloted" configuration, with the pilot supervising low altitude remote control flights sitting on an exposed "saddle" on the back. The safety pilot was provided manual controls which can over-ride control system commands in order to allow testing of changes to the flight control system with minimal risk to the airframe. This somewhat novel approach allowed rapid development of the vehicle handling qualities and evaluation of the flight controls at low cost and program risk. During its flight tests, the Raptor verified its low-altitude performance, structural integrity, and control system operations.
In addition to the Scaled Composites RAPTOR/Talon UAV, BMDO also worked on a solar-powered endurance UAV named "RAPTOR/Pathfinder" that would provide long-range sensors to help RAPTOR/Talon target TBMs (see inset left). However, BMDO found itself on increasingly shaky financial and political grounds as the 1990s progressed, and finally abandoned the RAPTOR/Talon and RAPTOR/Pathfinder. However, the idea of using UAVs for BPI hasn't gone away, and some industry officials still believe the Pentagon's RAPTOR/Talon concept of launching an interceptor from an unmanned aircraft may make a comeback. But one industry expert doubts its feasibility, noting that a missile launched from a high-altitude UAV would probably have insufficient range or speed to reach the target. It may be preferable to have a sensor on a UAV to detect the ballistic missile's launch, although the additional warning time provided by the unmanned aircraft compared with early warning satellites would likely be minimal, he noted.
The #1 aircraft completed 19 flights during Fiscal Year 1994, either unmanned or with Doug Shane or Mike Melvill on the saddle, but was lost in February 1994 due to a servo failure on an unmanned flight.. A replacement UAV was completed with a wider fuselage (so that the pilot could ride inside), first flew in August. 23, 1994. and performed a second flight before October in preparation for high-altitude, long-endurance missions later in the calendar year. With the end of the RAPTOR program, the UAV was not scrapped, and in 1995, was transferred to NASA under the Environmental Research Aircraft and Sensor Technology (ERAST) program as a flying testbed for technologies applicable to future high altitude UAVs.
At NASA, the Demonstrator-2 (or D-2) tested technologies that could result in long-duration (12 to 72 hours), high-altitude vehicles capable of carrying science payloads. Key technology development areas included lightweight structures, science payload integration, engine development and flight-control systems. Typical payload includes TDRSS satelite transponder or NASA Payload Environment Data system (PEDS). In late 1996, the D-2 was flown to test the vehicle's ability to communicate over the horizon using a Tracking and Data Relay Satellite System. The D-2 resumed flights in August 1998 to test a triply-redundant flight control system that would allow remotely piloted high-altitude missions.
Population: 2 [N62270 (c/n 001), N2272C (c/n 002), both deregistered]
Crew/passengers: unmanned (initially 1 pilot)Main sources:
Though not a Scaled Composites project in any way, RAPTOR/Pathfinder
was conceived to complement the RAPTOR/Talon in operation. It was
really nothing more than the AeroVironment HALSOL experimental UAV,
with solar cells.
Its wing was covered with solar panels that generated peak power of 11.4 kW to drive its eight small electric motors. The RAPTOR/Pathfinder could carry a payload of 41 kilograms (90 pounds), and was to evaluate the possibility of a HALE with potentially infinite endurance. However, it was not an effective solar HALE UAV. Initial flights were still on battery power, and though it could fly using solar power, the battery storage system didn't have the capacity to keep the aircraft flying all night long.