NASAfacts

National Aeronautics and Space Administration

Design reference mission: Search and rescue in wooded, mountainous area

Target environments AAM, UAM, and complex, cluttered 

environments 

ATTRACTOR: Autonomy Teaming and TRAjectories 

for Complex Trusted Operational Reliability

Autonomous systems (AS) are crucial to realizing 

the vision of new, complex transportation modes, 

such as advanced air mobility (AAM) and urban air 

mobility (UAM). A chief barrier to induction of AS into 

aviation is insufficient understanding of AS reliability 

in time-critical and safety-critical environments—

an obstacle to certification. ATTRACTOR is aimed 

at building a basis for certification of classes 

of autonomous cyber-physical-human systems 

(CPHS) via establishing metrics and models of 

trustworthiness and trust in multi-agent team 

interactions, analyzable trajectories, explainability 

of computational algorithms (explainable artificial 

intelligence, or XAI), and persistent modeling and 

simulation, in the context of missions planning and 

operation. By “building a basis for certification,” 

we mean acquiring an understanding of when a 

system is trustworthy and developing computable 

means to estimate trustworthiness and trust in 

order to eventually inform functional requirements 

that contribute to certification. The outcomes are 

applicable not just to aviation but to all domains that 

rely on autonomous systems.

The ATTRACTOR team has developed a CPHS for 

trajectory-based, mixed-reality multi-agent missions. 

To provide context for the development, search and 

rescue (SAR) has served as the design reference 

mission. ATTRACTOR comprises the following 

components: trajectory planning and management; 

navigation in challenging environments; persistent 

mixed-reality modeling and simulation; human–

machine teaming and interaction; visual recognition 

and XAI; testing and evaluation; anomaly detection; 

metrics and models of trust and trustworthiness; 

technology integration; and demonstrations in 

simulation and flight. Most components have been 

integrated into the CPHS. Both the system and 

contributing components were found to be feasible.
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ATTRACTOR Accomplishments

The integrated CPHS built in ATTRACTOR has proven to 

work reliably and safely in mixed-reality (simulation and 

flight) demonstrations, such as single-vehicle and multiplevehicle conflict-free trajectory management in challenging 

and cluttered environments. ATTRACTOR has developed a 

multi-center distributed mixed-reality capability (physical and 

virtual environments operating concurrently) in its Baseline 

Environment for Autonomous Modeling (BEAM), critical for 

generating statistically meaningful, challenging environments 

for testing AS. The project has also successfully applied 

the adaptive stress testing (AST) system to verification of 

trajectory management algorithms and has developed an 

anomaly detection system for recognizing an onset of offnominal conditions in complex operations. ATTRACTOR has 

also investigated several promising approaches to improving 

explainability of machine learning algorithms used for object 

recognition during SAR. 

In a collaboration with the Massachusetts Institute of 

Technology, ATTRACTOR has successfully demonstrated 

Search and Rescue Under the Canopy (SARUC) in a forested, 

GPS-denied environment.

Transition Opportunities

ATTRACTOR’s work extends to multiple disciplines and 

offers numerous opportunities for transition to government 

and civilian organizations as well as private industry. 

Organizations engaged in SAR and humanitarian deliveries 

have already expressed interest in technology transition 

from ATTRACTOR. Here at NASA, ATTRACTOR’s work will 

continue in multiple areas: 

• Work on fundamental autonomy capabilities is being 

transitioned from NASA’s aeronautics domain to the space 

domain; these technologies include coordinated trajectory 

generation, path/motion planning, swarming, semantic 

object classification, detect and avoid, mission/task 

planning, and trust/trustworthiness. 

• ATTRACTOR’s modeling and simulation environment, 

BEAM, is being tailored for NASA Transformational 

Tools and Technologies (TTT) activities on autonomous 

frameworks, concepts, and scenarios for dynamic 

coordination of autonomous agents.

• ATTRACTOR’s work on human–autonomy teaming (HAT) 

has transitioned to other NASA projects: TTT/Reconnection 

and Micro-Scale (RAM), System-Wide Safety (SWS), and 

Air Traffic Management–eXploration (ATM–X).

For more information, contact: 

Dr. Natalia Alexandrov, n.alexandrov@nasa.gov

Dr. B. Danette Allen, danette.allen@nasa.gov

Trustworthiness:

Assurance the CPHS performs as required

Trajectory management has been proven to 

generate realizable trajectories. All ATTRACTOR 

components contribute to trustworthiness of CPHS.

Analog of cluttered 

environment in simulation

Reality in flight 

through physical maze

Trust:

Readiness to rely on another agent

Facilitate trust in 

autonomous systems 

by using domain 

expert knowledge to 

identify anomalies 

and their precursors. 

Explain anomalies 

during operations.

Certification

Mixed-reality simulation-to-flight platforms will play 

a crucial role in understanding of complex system 

behavior to inform certification requirements.