By John Keller
BALTIMORE - Torpedo designers from Northrop Grumman Corp. are one year ahead of schedule in delivering the latest electronics upgrades for the MK 48 ADCAP submarine-launched torpedo to the U.S. Navy.
The reason for the schedule speedup: the transition to commercial off-the-shelf (COTS) components, says Dave Prestel, lead electrical engineer on the ADCAP torpedo upgrade program at Northrop Grumman Corp.`s Electronic Sensors and Systems Division (formerly Westinghouse) in Baltimore. ADCAP is short for "advanced capability."
The latest MK 48 modification program, commonly known as ADCAP MODS, began in 1995 and "was one of the Navy`s first acquisition-reform contracts" under guidelines of then-Defense Secretary William Perry`s mandate to use as much COTS equipment as possible, explains Ron Sobecks, the ADCAP MODS engineering manager for development and technology insertion.
"The conversion to COTS came when our production contract was released [in 1995], so from then on we have converted our parts list from military components to COTS components, and we are actively in production now," Prestel says.
Although Northrop Grumman engineers retain mil-spec parts in the ADCAP`s warhead circuitry, "the guidance, power, and receiver for the torpedo must only meet performance specs for the physical envelope," Prestel says. "All internals were at the purview of the company."
The ADCAP MODS program represents a technology bridge between the mil-spec/custom design approach of the early 1990s, and the COTS/open-systems approach that engineers are carrying out on existing and future military electronics projects.
While ADCAP MODS uses the COTS Lucent (formerly AT&T) DSP32C digital signal processor and Motorola 68040 microprocessor, its printed circuit card and backplane data bus retain a custom flavor. The data bus is specific to ADCAP, and the circuit cards are custom 6-by-9-inch designs, Sobecks says.
Still, company engineers in their initial shift to COTS explored what was then new ground by working with suppliers to achieve the right levels of ruggedization in the absence of mil specs.
"We worked with AT&T on thermal and shock to maintain reliability," says Steven Dudek, the ADCAP torpedo program manager at Northrop Grumman. "These boards are ruggedized electronics designed to take shock and vibration."
The upgrade also moves away from mil-spec ceramic packaging certified to temperatures between -55 degrees Celsius and 125 C, Prestel explains. Now engineers are using plastic-packaged devices certified for temperatures between -2 C and 85 C, he says.
Even before designers realized they could shave a year off the ADCAP upgrade program, they were able to reap immediate benefits from using COTS. "We reduced 80 circuit cards to 18 cards by going with commercial designs, and improved processing throughput of the weapon may be an order of magnitude," Dudek says.
Future plans
As Dudek and his team finish the latest installment of their transition to COTS in the ADCAP, they are looking ahead to future MK 48 modifications that will go even farther to enhance the weapon`s capability and introduce commercially developed components.
"Currently with the Navy we are introducing newer, smarter approaches for keeping pace with technology," Sobecks says. "The trend is to go to open systems so we can preserve the Navy`s software investment by making the software transportable. From this point on we are going to 6U VME [printed circuit card and backplane data bus] on our new products."
Navy officials want an electronics architecture common to the ADCAP and to their new Lightweight Hybrid Torpedo (LHT) under development at the Hughes Aircraft Co. Naval and Maritime Systems division (formerly Alliant Techsystems) in Mukilteo, Wash., Sobecks says.
The LHT program will use the 6U VME circuit card form factor and 64-bit backplane data bus, PowerPC-based single-board computers from Radstone Technology in Montvale, N.J., and single-board digital signal processors based on the Texas Instruments 320C40 DSP chip from Mizar Inc. of Carrollton, Texas.
"The CPU card will probably be consistent with the Lightweight Hybrid Torpedo," says Marc Chappo, lead ADCAP MODS systems engineer at Northrop Grumman. "We are looking at the PowerPC, the 320C40, and the [Analog Devices 21060] SHARC DSP. The SHARC is probably one of the hottest devices out there."
Chappo says Northrop Grumman engineers most likely will use the SHARC only in receiver functions on the ADCAP upgrade. For SHARC DSP board support, Chappo says he and his colleagues are considering Spectrum Signal Processing Inc. of Burnaby, British Columbia.
Northrop Grumman engineers are preparing this open-systems architecture for the ADCAP for what they anticipate will be a competition for another ADCAP electronics overhaul perhaps as early as 1999, Sobecks says.
Future ADCAP upgrade competitions most likely will pit Northrop Grumman and Hughes, the nation`s preeminent torpedo manufacturers. Hughes Aircraft is in the process of being absorbed into Raytheon Co., which should be final sometime this fall, says Hughes corporate spokesman Dave Shea.
Lab technicians inspect a MK 48 ADCAP submarine-launched torpedo. Manufacturers are moving COTS components into upgraded MK 48 torpedoes, and plan on moving to more COTS upgrades that will include the PowerPC microprocessor and the VME backplane data bus.
