MIT ICAT Technology Considerations for Advanced Formation Flight Systems Prof. R. John Hansman MIT International Center for Air Transportation MIT ICAT How Can Technologies Impact System Concept y Need (Technology Pull) ? Technologies can fulfill need or requirement ? Technologies can overcome barriers (limitations, constraints, etc.) y Opportunity (Technology Push) ? Technologies can Create Opportunities ? New Capabilities ? Competitive advantage ? Cost ? Performance ? Maintenance ? Other MIT ICAT Formation System Concept is Itself a Technology y Needs ? Efficient Transport ? Fuel ? Cost DCrew, Maintenance… ? Operational Access (Noise, Runways) ? Flexibility ? Others y Opportunity ? Different design space if use multiple vehicles ? Overcome constraints (eg runway width, single departure point) ? Performance ? Fuel efficiency, crew ? Development of key technologies enable formation flight ? Flexibility ? Runway Throughput MIT ICAT What are the Key Technologies for Formation Flight y Start with Fundamental Abstraction of System or Concept (many ways) ? Functional ? Operational ? Concept of Operations ? Physical ? Component ? Constraint ? Information y Based on Abstract view, identify ? Technology needs ? Key questions ? Potential opportunities y Useful to sketch elements to visualize system ? Multiple views MIT ICAT What are the Key Technologies for Formation Flight MIT ICAT What are the Key Technologies for Formation Flight y Overall Concept Questions ? Concept of Operations? ? How does form up occur ? Station keeping requirements ? Failure Modes ? Existing elements or New ? Vehicles ? Control Systems ? CNS ? Other y Concept Scale Opportunities/Costs ? Performance gains estimate ? Fuel ? Capacity ? Costs ? Development ? Deployment y Concept Technologies Reqs ? Formation design ? Station Keeping ? Com ? Nav ? Surveillance ? Control MIT ICAT What are the Key Technologies for Formation Flight y Communications y Navigation y Surveillance y Control (Station Keeping) ? Intent States ? String Stability y Vehicle Configuration ? Aero/Performance ? Control y Propulsion y Degree of Autonomy y Flight Criticality ? Hardware ? Software y Low Observability y Others? MIT ICAT Communications y Requirements ? Communicate necessary information between formation elements and command node (LAN and Air-Ground) ? Bandwidth ? Low-Observable? ? Synchronous vs asynchronous y Constraints ? Spectrum ? Antenna Location y Technologies ? Radio ? UHF, VHF, MMW ? Optical ? Laser ? Protocols MIT ICAT COMMUNICATION y Voice ? VHF (line of sight) ? 118.0-135.0 Mhz ? .025 spacing in US, 0.083 spacing in Europe) ? UHF ? 230-400 Mhz (guess) ? HF (over the horizon) ? Optical (secure) y Datalink ? ACARS (VHF) - VDL Mode 2 ? VDL Modes 3 and 4 (split voice and data) ? HF Datalink (China and Selcal) y Geosynchronous (Inmarsatt) ? Antenna Requirements y LEO and MEO Networks y Software Radios y Antenna Requirements MIT ICAT Generic Avionic System Software Hardware Antenna Sensor Databus Flight Data Recorder Black Box Input Device Display MFD Interface Unit DatalinkAntenna Power Cooling MIT ICAT Navigation (relates to Surveillance) y Requirements ? General Navigation (medium precision) ? Station Keeping (high precision) ? Integrity ? Availability y Constraints ? Existing nav systems ? Loss of signal y Technologies ? GPS/Galileo (need Differential) ? Code vs Carrier Phase Approaches ? IRS/GPS ? Sensor Based Approaches for Station Keeping ? Image (Visible, IR) ? Range Finders (Laser, Ultrasonic) MIT ICAT GPS From http://www.colorado.Edu/geography/gcraft/notes/gps/gps_f.html (Courtesy of Peter Dana. Used with permission.) MIT ICAT Inertial Reference Unit y Integrate acceleration from known position and velocity ? Velocity ? Position y Need Heading ? Gyros ? Mechanical ? Laser y Can get Attitude ? Artificial Horizon (PFD. HUD) y Drift Errors ? IRU unusable in vertical direction (need baro alt) ? Inflight Correction ? DME ? GPS ? Star Sighting for Space Vehicles y Measurement Give Attitude Also y 777 Analytical Redundancy MIT ICAT Surveillance y Requirements ? Observed states of lead elements sufficient to form-up and maintain station keeping either manually or by automatic control ? Feed forward states (intent) y Constraints ? Sight Angles ? Installation (weight, cost, power, etc) ? Cooperative Targets y Technologies ? Automatic Dependant Surveillance Broadcast (ADS-B) ? Image Based Systems (Vis, IR) ? Radar (X Band, MMW0 ? Range Finders (Laser) ? Sensor Fusion Systems MIT ICAT ADS-B Bob Hilb UPS/Cargo Airline Association (Image removed due to copyright considerations.) MIT ICAT RADAR y Wavelength λ ? S Band (10 cm) ? X Band (3 cm) ? Ku Band (1 (cm) ? Millimeter Wave (94 Ghz pass band) y Radar Range Equation y Beamwidth Θ ? Θ = λ/D ? D = Diameter of Circular Antenna ? Pencil beam vs Fan Beam y Mechanically Steered Antennas ? Scan and Tilt MIT ICAT INTENT REPRESENTATION IN ATC y Intent formalized in “Surveillance State Vector” y Accurately mimics intent communication & execution in ATC ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? D(t) states, nDestinatio T(t) states, trajectory Planned C(t) states, target Current A(t) states, onAccelerati V(t) states,Velocity P(t) states, Position Traditional dynamic states Defined intent states Surveillance State Vector, X(t) = FMS Current target state, C(t) Destination, D(t) Planned trajectory, T(t) MCP PILOT MIT ICAT RADAR SURVEILLANCE ENVIRONMENT y Allows visualization of different (actual or hypothetical) surveillance environments ? Useful for conformance monitoring analyses of impact of surveillance A/C INTENT CONTROL SYSTEM AIRCRAFT DYNAMICS Position, P(t) Velocity, V(t) Accel., A(t) PILOT INTENT Target states, Guidance mode Nav. accuracy e.g. ANP Control surface inputs A/c property e.g. weight Trajectory, Destination Position Mode C altitude RADAR SURVEILLANCE SYSTEM ACTUAL SYSTEM REPRESENTATION MIT ICAT ADS-B SURVEILLANCE ENVIRONMENT y Potential access to more states (e.g. dynamic and intent) y Need to assess benefits for conformance monitoring A/C INTENT CONTROL SYSTEM AIRCRAFT DYNAMICS Position, P(t) Velocity, V(t) Accel., A(t) PILOT INTENT Target states, Guidance mode Nav. accuracy e.g. ANP Control surface inputs A/c property e.g. weight Trajectory, Destination Position, Baro altitude Heading, Speeds Roll, ... Target states ACTUAL SYSTEM REPRESENTATION Trajectory ADS-B SURVEILLANCE SYSTEM Other useful states??? MIT ICAT Control y Requirements ? Maintain Station Keeping sufficient to achieve formation benefits ? Tolerance to Environmental Disturbances ? String stability y Constraints ? Certification ? Failure modes ? Available states y Technologies ? Performance seeking control ? Multi-Agent Control Architectures ? Distributed Control Approaches ? Leader-Follower Schemes ? Fault Tolerant Systems ? Redundancy Architectures MIT ICAT Automation y Requirements ? Form up and station keeping may need to be automated y Constraints ? Reliability, integrity ? Certification ? Failure Modes y Technologies ? Flight Directors ? Autopilots ? Intercept systems MIT ICAT Software y Requirements ? High Integrity Implementation for Formation ? Formation requirement exceeds specs for current vehicles (eg 777) y Constraints ? Failure Modes y Technologies ? DO 178B ? ?? MIT ICAT Aero-Configuration y Requirements ? Mission based requirements (you will define) ? Formation based requirements ? Special Control Requirements y Constraints ? Stability and Control (CG) ? Formation and non-Formation operation y Technologies ? Conventional approaches modified by formation considerations ? Asymmetric ? Formation optimal vs single optimal DLead - High WL, Low AR >> high vortex DTrail - Low WS, High AR >> Low drag ? Vortex Tailoring ? Unique configurations or control systems MIT ICAT Configuration y Symmetric vs Asymmetric y Variable ? Formation vs Free Configurations y Formation Specific Considerations ? What is the optimal aspect ratio for overall performance y Are there special, non-classical control needs? y What are takeoff and landing considerations y In-flight physical hookups MIT ICAT Propulsion y Requirements ? Take-off, balanced field length >> drives thrust ? Cruise efficiency ? Response time y Constraints ? Operational in formation and non formation configuration y Technologies ? Unmatched multi engines (shut down in cruise, eg Voyager) ? Broad operating envelope engines (SFC hit) ? Tow Schemes MIT ICAT Propulsion Voyager MIT ICAT Formation Transport Example: C-47 (DC-3) towing CG-4 Cargo Gliders http://www.atterburybakalarairmuseum.org/CG4A_C47_color_photo.jpg Courtesy of the Atterbury-Bakalar Air Museum. Used with permission. MIT ICAT What are the risk considerations for technology incorporation y Readiness ? NASA Technology Readiness Levels (TRL) y Vulnerability ? High (Key Element on Which Concept Based) ? Medium (Performance or Capability Enhancing, Competitive Factor) ? Low (alternatives available) y Competitive Risk ? Goes both ways y Certification Risk y Operational Considerations ? Issues are discovered in field operations ? Tracking Programs ? Unanticipated uses of technology MIT ICAT What are the risk considerations for technology incorporation y Readiness ? NASA Technology Readiness Levels (TRL) y Vulnerability ? High (Key Element on Which Concept Based) ? Medium (Performance or Capability Enhancing, Competitive Factor) ? Low (alternatives available) y Competitive Risk ? Goes both ways y Certification Risk y Operational Considerations ? Issues are discovered in field operations ? Tracking Programs ? Unanticipated uses of technology