EXHIBIT 21

DRS TECHNOLOGIES, INC.    SUBSIDIARIES OF THE COMPANY AS OF MARCH 31, 2008

|SUBSIDIARY                                 |  | STATE OR COUNTRY
OF FORMATION
|------------------------------------------ |  | -----------------------------
|NAI Technologies, Inc.                     |  | New York                     
|DRS Surveillance Support Systems, Inc.     |  | Delaware                     
|DRS Technologies UK Ltd.                   |  | United Kingdom               
|DRS Systems Management Corporation         |  | Delaware                     
|Laurel Technologies Partnership            |  | Delaware                     
|DRS Power & Control Technologies, Inc.     |  | Delaware                     
|DRS Power Technology, Inc.                 |  | Delaware                     
|DRS Tactical Systems, Inc.                 |  | Florida                      
|DRS Intelligence & Avionic Solutions, Inc. |  | Ohio                         
|DRS Sensors & Targeting Systems, Inc.      |  | Delaware                     
|DRS Unmanned Technologies, Inc.            |  | Delaware                     
|DRS Data & Imaging Systems, Inc.           |  | Delaware                     
|DRS Data & Imaging Systems Limited         |  | United Kingdom               
|DRS Hadland Ltd.                           |  | United Kingdom               
|DRS Technologies Canada, Inc.              |  | Delaware                     
|DRS Technologies Canada Company            |  | Canada (Nova Scotia)         
|DRS C3 Systems, LLC                        |  | Delaware                     
|DRS Sonar Systems, LLC                     |  | Delaware                     
|MSSC Company                               |  | Pennsylvania                 
|Tech-Sym Corporation                       |  | Nevada                       
|DRS Test & Energy Management, Inc.         |  | Delaware                     
|DRS EW & Network Systems, Inc.             |  | Delaware                     
|DRS Signal Solutions, Inc.                 |  | Delaware                     
|DRS Training & Control Systems, Inc.       |  | Florida                      
|T-S Holding Corporation                    |  | Texas                        
|DRS EW & Network Systems (Canada) Limited  |  | Canada                       
|DRS International, Inc.                    |  | Delaware                     
|DRS Systems, Inc.                          |  | Delaware                     
|Night Vision Systems, LLC.                 |  | Delaware                     
|Canopy Technologies, LLC                   |  | Delaware                     
|DRS Tactical Systems Global Services, Inc. |  | Florida                      
|DRS Homeland Security Solutions, Inc.      |  | Delaware                     
|Walkabout Computers UK Limited             |  | United Kingdom               
|DRS Codem Systems, Inc.                    |  | Delaware                     
|Engineered Support Systems, Inc.           |  | Missouri                     
|ESSI Resources, LLC                        |  | Kentucky                     
|Engineered Coil Company                    |  | Missouri                     
|Engineered Electric Company.               |  | Missouri                     
|DRS Sustainment Systems, Inc.              |  | Delaware                     
|Universal Power Systems, Inc.              |  | Delaware                     
|DRS Technical Services, Inc                |  | Maryland                     
|DRS Mobile Environmental Systems Co.       |  | Ohio                         
|3083683 Nova Scotia Limited                |  | Canada (Nova Scotia)         
|Pivotal Power, Inc.                        |  | Canada (Nova Scotia)         
|PCA Electronic Test Ltd.                   |  | United Kingdom               

---



QuickLinks