External Payload Deployment System for Cylindrical UUVs

Navy SBIR 21.2 - Topic N212-123
ONR - Office of Naval Research
Opens: May 19, 2021 - Closes: June 17, 2021 (12:00pm edt)

N212-123 TITLE: External Payload Deployment System for Cylindrical UUVs

RT&L FOCUS AREA(S): Autonomy;Microelectronics;Networked C3

TECHNOLOGY AREA(S): Ground / Sea Vehicles;Sensors;Weapons

OBJECTIVE: Develop an external payload deployment system for cylindrical unmanned underwater vehicles (UUVs. Example payloads may be sensors, markers, or communications relays. The system will not interfere with the operation of the UUV and will respond to UUV commands to detach and activate.

DESCRIPTION: There are many UUV missions that would benefit from leave-behind technology. However, the UUV market is dominated by cylindrical UUVs, making development of an external payload deployment system technically challenging. Despite the technical difficulties involved, the potential for UUV navigation, communication, environmental monitoring, and surveillance payloads make this SBIR topic a worthwhile endeavor. The main technical challenge is that such a system will modify the hydrodynamic behavior of the host UUV and will therefore affect its controllability and maneuverability. Another important technical challenge is minimally invasive command and control communications between the UUV and the external payload.

Most current UUVs cannot leave behind useful technology when they encounter something of interest. In many retrieval scenarios, precisely placing an acoustic beacon would aid the following retrieval mission normally undertaken with work class Remotely Operated Vehicles (ROVs). In another scenario, placing a communications relay, where underwater communications starts to degrade, would avoid the loss of communications with a vehicle. In yet another scenario, leaving a trail of small markers may aid feature-based navigation in featureless environments. For these scenarios, the most versatile and fastest integration approach would be to mount an external payload onto the vehicle and have this payload receive instructions without having to make physical connections to the vehicle’s systems.

Technology proposed under this effort should develop an external payload for cylindrical UUVs up to 21" in diameter that minimizes interference with UUV hydrodynamics and vehicle control while limiting reduction to mission endurance. Additionally, the payload should communicate with the UUV payload computer using connections that do not pierce the UUV hull. Proposers should also understand and demonstrate the flight stability of the payload when dropped, and determine the accuracy of the deployment relative to the intended location. The design must have a robust buoyancy compensation system for the payload such that the changes to the UUV’s Center of Gravity and Center of Buoyancy are not detrimental. Deployment should be effective over a limited range of UUV altitudes and speeds (less than 5 m altitude and speed of less than 5 m/s).


  • UUVs Under Consideration: Cylindrical main body with a diameter of between 5 and 21 inches and length less than 20 ft.
  • Buoyancy: Neutral when attached to UUV / Negative when detached from UUV
  • Hydrodynamic Forces: Should not appreciably change UUV Center of Gravity or Center of Buoyancy and not require UUV controller modification
  • Communications: no through-hull modifications
  • Detachment: on-command from UUV
  • Payload drop accuracy: determined by program @ UUV min speed: 1 m/sec and UUV min depth 3 m
  • Parasitic drag after release: minimal less than 10% over unmodified vehicle drag
  • Payload drag (before or after detachment): should not decrease UUV mission time by more than 25%
  • Adaptable buoyancy in variety of seawater densities – including freshwater
  • Anticipate standard mil spec environment, shock, vibration, transportability testing in Phase II/III
  • Carry load: module that weighs up to 5 kg in air

Testing for standard mil spec compliance (environment, shock, vibration, and transportability) will occur in Phase II and III.

PHASE I: Demonstrate the feasibility of a concept for an external UUV payload that satisfies the previously listed design criteria for a cylindrical vehicle. Smaller diameters that the 5 inches in the design criteria can be proposed, as long as there is evidence that the payloads would provide a useful function. Analysis on initial hardware and software concepts will be completed to determine the optimal design and feasibility in the projected use case. Either modeling using semi-empirical methods [Refs 1, 4, 5] and simulations [Refs 2, 3] or in-water tests will be performed to justify the approach. An analysis will also be made of the most effective command and control communication approach that will not require perforation of the UUV hull. Develop a Phase II plan.

PHASE II: Develop and fabricate two to three prototype systems for evaluation. Precise evaluation metrics will be developed in consultation with the appropriate acquisition program office. The prototype demonstration should show applicability to current UUV form factors and mission requirements. Perform detailed analysis on ruggedness and compatibility with Navy UUV handling, storage, and environmental operating conditions. Testing will be conducted by both the performer and by Navy personnel on Navy assets. Cost effectiveness and manufacturability feasibility should be addressed as part of the prototype test and evaluation.

PHASE III DUAL USE APPLICATIONS: Applying the knowledge gained in Phase II, build an advanced UUV payload system that meets appropriate technology readiness level (TRL) metrics set by the acquisition program office. Support the Navy for test and validation of the system for certified Navy use. Explore the potential to transfer the payload delivery system to commercial use (e.g., oil and gas industry). Develop manufacturing plans to facilitate transition to a UUV program of record.


  1. Severholt, J. "Generic 6-DOF Added Mass Formulation for Arbitrary Underwater Vehicles based on Existing Semi-Empirical Methods." Master’s Thesis, Royal Institute of Technology of Sweden, June 20, 2017.
  2. Liu, A.; Chen, G.; Feng, J. and Hu, J. "Research on the Hydrodynamic Characteristic of Conformal Semi-Ring Wing Configuration." 2017 International Conference on Computer Systems, Electronics and Control (ICCSEC), pp. 78-82.
  3. Zhou, J. and Wang, S. "Dynamics Modeling and Maneuverability Simulation of the Unmanned Underwater Vehicle Hanging Torpedoes Externally." 2009 International Asia Conference on Informatics in Control, Automation and Robotics, Bangkok, 2009, pp. 207-210.
  4. Perrault, D. "Sensitivity of AUV added mass coefficients to variations in hull and control plane geometry." Ocean Engineering, vol. 30, April 2003, pp. 645-671.
  5. Humphreys, D.E. and Watkinson, K.W. "Prediction of acceleration hydrodynamic coefficients for underwater vehicles from geometric parameters." Naval Coastal Systems Laboratory Tech Report NCSL 327-78, Panama City, Florida, 1978.

KEYWORDS: Unmanned underwater vehicle; UUV; payload, navigation, communication, surveillance, hydrodynamic forces


The Navy Topic above is an "unofficial" copy from the overall DoD 21.2 SBIR BAA. Please see the official DoD Topic website at rt.cto.mil/rtl-small-business-resources/sbir-sttr/ for any updates.

The DoD issued its 21.2 SBIR BAA pre-release on April 21, which opens to receive proposals on May 19, 2021, and closes June 17, 2021 (12:00pm edt).

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