Large UAV platforms–like Global Hawk, Predator, Fire Scout, Taranis and others–have a seemingly endless appetite for greater onboard compute density. The payloads aboard those systems are enabling ever greater autonomy for the UAV and its mission. The movement is toward more capable radar systems that fit into the same space, and in some cases more compact radar electronics to make room for other payload electronics.

Next-generation UAVs have shifted their internal architectures from a scheme of multiprocessing of big, power-hungry boards based on general-purpose processors to a strategy of relying on more integrated boards sporting powerful DSP-capable FPGAs. The original Global Hawk, for example, embedded around 40 processor boards. At least 30 of those boards were replaced by a couple of FPGA-based cards.

It isn’t just straight processing integration that the FPGAs provide. They’re most efficient at the DSP-kinds of functions done on board like radar processing and SIGINT. When the earlier version of Global Hawk used a multicomputer system made up of only general-purpose processors, it was inefficient when it came to many of the computing tasks. By instead letting FPGAs concentrate operations like repetitive convolutions–such as data reduction and manipulation–the general-purpose CPUs are off-loaded to focus on data-dependent control operations, which they’re good at.

Modular Radar System

An example of where this FPGA-based compute density is playing a role is the Multi-Platform Radar Technology Insertion Program (MP-RTIP). The MP-RTIP is a modular, active electronically scanned array radar system designed to be scaled in size so that it can be carried on board different platforms. Mezzanine form factors like PMCs and XMCs are well represented in the MP-RTIP program.

Earlier this month Northrop Grumman got approval to begin a portion of MP-RTIP Radar System Level Performance Verification (RSLPV) flight testing. The approval comes following a successful test readiness review for the MP-RTIP sensor’s Synthetic Aperture Radar imaging mode. This radar is slated for the RQ-4 Block 40 Global Hawk currently in production. The goal of the RSLPV test program is to verify that the radar meets operational requirements established by the Air Force, including Synthetic Aperture Radar (SAR) Spot image capabilities, SAR Swath imaging wide area capability, and Ground Moving Target Indicator (GMTI) capability to detect and track moving vehicles on the ground.

For RSLPV, the sensor is being flown on Northrop Grumman’s Proteus aircraft (Figure 1) as a surrogate for the first Block 40 Global Hawk. By verifying sensor performance on Proteus, the sensor testing has progressed without impact to production, significantly lowering the risk with regard to the Global Hawk’s operational capability. The first Block 40 Global Hawk, AF-18, has been built at Palmdale, CA, and is undergoing testing in preparation for its first flight later this year.

Cooling Enables Use of Faster Processing

Another method of boosting compute-density aboard large UAVs is the concept of using advanced cooling solutions that enable integrators to use boards that are less environmentally rugged in and of themselves. The problem can be addressed by using sealed, air-conditioned or pressurized compartments. These include both the U-2 Dragon Lady (ASIP program–Air Force Signals Intelligence Payload) and RQ-4 Global Hawk UAV. In both cases, alternative cooling solutions were needed to accommodate the upgrades. Meanwhile, other UAV platforms such as the MQ-1 Predator and MQ-9 Reaper don’t have any conditioned space, yet they had similar requirements for improved sensor capabilities and their designers likewise wished to leverage existing air-cooled board sets. The article “UAVs Embrace the Benefits of Direct Spray Cooling” in this section discusses how direct spray cooling enclosures help solve those problems.

Last summer Northrop Grumman’s ISR Systems Division awarded SprayCool a contract to provide its liquid-cooled enclosures for the ASIP-1C program. The SprayCool enclosures will house SIGINT electronics for the Air Force’s SIGINT-equipped MQ-1B Predator UAV (Figure 2) in support of Predator’s tactical warfighting role, sometimes described as a hunter/killer/scout mission. Under this contract, the SprayCool Multi-Platform Enclosure (MPE) was selected as a component in the ASIP-1C sensor payload for SIGINT-equipped Predator aircraft.

One trend that exemplifies the U.S. military’s direction for large UAVs is a move toward payloads that enable ever greater autonomy for the UAV and its mission. This includes doing more of that processing on the UAVso that a more refined set of information can be transmitted to war fighters on the ground. Traditionally almost all UAV-captured data has been transmitted to the ground and processed for interpretation and decision making. By boosting onboard processing muscle, UAVs should be able to relay the results of their data to the ground for decision making. The benefit is reduced reliance on data link rates in certain applications, particularly imagery collection. If processing of data and decision making can be performed on board the UAV itself rather than via a communication link with the ground, the more efficiently the craft can be used.

Onboard Image Processing

Along those lines, SRC Computers last fall shipped the first onboard signal data processor (SDP) for Lockheed Martin’s Tactical Reconnaissance and Counter-Concealment Enabled Radar (TRACER) program. Using dual-band low frequency synthetic aperture radar, TRACER can immediately downlink images and processed results from Predator-class UAVs to ground units in all-weather, day or night conditions.

SRC’s system features an architecture that provides compute-intensive reconfigurable processing in a compact form factor. It allows users to execute existing code, or easily develop and compile new code, to take advantage of the power of the reconfigurable MAP processors in the system. The SDP is comprised of a multi-MAP system that weighs 80 pounds and consumes less than 600W of power while being functionally equivalent to about 100 Power PCs for this application.

Another UAV that relies heavily on slot-card boards is the Fire Scout Vertical Takeoff and Landing Tactical Unmanned Aerial Vehicle (VTUAV). While not technically a Joint Army/Navy program, the two branches are cooperating closely on it. The Army has selected Fire Scout as its Class IV UAV for its Future Combat Systems program. The Navy version, much further along in its development, achieved first flight in January 2006. The event marked the first time a UAV performed vertical landings on a moving ship without a pilot controlling the aircraft. Embedded computers and the payload interface unit aboard the MQ-8B Fire Scout are 3U CompactPCI boards supplied by GE Fanuc Intelligent Platforms.

Payload Tests for Fire Scout UAV

Last fall Northrop Grumman accomplished a pair of key system test flights with its company-owned MQ-8B Fire Scout. In October it flew its new Airborne Surveillance, Target Acquisition and Minefield Detection System (ASTAMIDS) (Figure 3) for the first time aboard a UAV. Using a tactical common data link, the company team at the developmental Tactical Ground Segment, a ground-based payload control center, successfully operated the Payload Command and Control and Imagery Data Collection systems in ASTAMIDS while it was airborne. The test showed how a Fire Scout can carry ASTAMIDS far beyond the point of U.S. ground forces to detect the presence of minefields and sight enemy locations without putting a single soldier at risk.

In other tests, Northrop Grumman demonstrated continuous combined payload coverage on its MQ-8B Fire Scout by successfully downlinked simultaneous digital video from both a Telephonics RDR-1700B multi-mode maritime radar and a FLIR Systems, Inc. Star SAFIRE(r) III electro-optical/infrared sensor using its tactical common data link developed by Cubic Defense Applications. The multi-sensor Star SAFIRE(r) III provides domestic and international customers a state-of-the-art capability for meeting real-time video requirements for electro-optical and infrared imagery. The successful 40-minute flight took place at the Yuma Proving Ground in Arizona.