Digital Models Expedite Crusader Redesign.

Simulation lab turns massive engineering data into sharp visuals

When the Army decided to trim down the weight of the Crusader field artillery system by 20 tons, the prime contractor redesigned the vehicle in less than seven months. What made this possible, officials said, was the sophistication of the manufacturer's computer-aided simulation technology.

By Pentagon standards, seven months is an unusually fast turnaround for a major weapon system redesign. Before digital design technology became the norm in vehicle manufacturing, making such drastic changes in engineering drawings would take several years.

Computer-aided design has been around for decades and is used in most Pentagon weapon programs today. But Crusader officials claim that they have pushed this technology farther than other defense programs or other industries, such as the automotive and aeronautical design.

The Crusader field artillery program, made by United Defense LP (UDLP), in Minneapolis, began in 1994. It was designed to replace the aging Paladin self-propelled howitzers currently in the Army inventory. The system consists of a self-propelled howitzer and an ammunition resupply vehicle. The two pieces weighed 110 tons, which was acceptable in the early stages of the program.

But approximately 18 months ago, the Army announced it would undergo a socalled "transformation" process to become a lighter, more mobile force. That meant Crusader had to be slimmed down, or it would not fit into the Army's war-fighting strategy.

At UDLP's armaments division in Minneapolis, engineers, designers, number-crunching executives and Army officers have been watching the redesign unfold in front of their eyes at the company's "visual integration lab."

Major modifications were made on both vehicles. The 55-ton howitzer was trimmed to about 40 tons (not including armor kits and ammunition). Half of the resupply vehicles, which initially were tracked, will be wheeled.

The U.S. Army spent $355 million on Crusader this fiscal year.

The visual integration lab, which was installed in 1998, is one among only 35 such facilities in the United States, said David Crowell, the company's marketing manager. Typically, this type of facility would be found in the entertainment industry, Crowell told reporters during a tour of the plant last month.

"The big thing that this allows you to do is work in real time," he said. Computers process massive amounts of engineering data, allowing Crusader officials to "see how it ought to work before you do any simulations. ... We reduced the acquisition cycle for major systems by a third."

The visualization technology facilitates easy "what-if" iterations of different design changes, explained Crowell. "We can strip it down and build it back up. ... Within two months, we were able to tell the Army whether we could take the 20 tons off the vehicle. Within seven months, all the design options had been completed."

The computer-aided engineering design tool used for Crusader is a commercial software package called Pro-Engineer. "We take the master data base--the design of the Crusader--and we bring in the [software] tool and then run the system and subsystems in real time," Crowell explained. Crusader's design has more than 2 million lines of software code. The tools also are commercial software, called dVISE version 6.0.2 and dVMockup.

During a demonstration for reporters, UDLP engineers ran a "visualization sequence" which showed the three components of the system: the howitzer and both the tracked and wheeled resupply vehicles.

Because the digital mockups exactly replicate the real vehicles, Crowell said, "we could achieve a great deal of confidence in the redesign and that it's going to work.

"All the tools are linked by a dynamic object model," Crowell said. UDLP simulation experts designed that model. "That is the glue that holds all of the timelines and the designs together so we can actually operate and understand the behavior" of the Crusader system.

The same technology had been used to design the original, heavier Crusader. But when it came time to overhaul the design, Crowell said, "We pushed the envelope on virtually every design tool that exists."

UDLP engineers often have invited the various software developers of the design tools to the lab "to discuss how their tool has to be better to do what we want to do," he said. "We made those companies [improve] those tools."

Before the redesign, Crusader was scheduled to join Army units by 2005. Congressional funding cuts, as well as the redesign, pushed that deadline to 2008. Nevertheless, said Crowell, "I don't think anyone can beat the design cycle we've got going right now."

Unlike any other howitzer in the Army today, Crusader has a fully automated capability to load the 100-pound rounds inside the howitzer and inside the resupply vehicle. The design of thousands of moving parts has to be perfect to avoid break-downs and jams during firing operations. The system has no manual back-up, so "reliability is a huge issue," said James E. Unterscher, Crusader's program director at UDLP. The precision of the digital design tools help achieve those demanding parameters, he said. That is how the company has been able to run more than 25,000 tests, Unterseher told National Defense.

Changes made to take 20 tons off the weight of Crusader:

* The number of projectiles in the howitzer was cur from 60 to 48. In the resupply vehicle, instead of 130 rounds, it now carries 100. The quantity of propellant charges per vehicle was reduced from 260 to 208. That saved about two-thirds of a ton. The 155mm projectiles are 3 feet long and 6 inches in diameter. The cannon will fire 10 rounds a minute.

* The howitzer was made about 1.5 feet shorter and 4 inches narrower. Reductions in the length and the width combined saved 3.4 tons.

* The engine was changed from a 12-cylinder diesel to a turbine. The smaller engine translated into a 3.5-ton weight savings. Additionally, the use of lighter materials and composites throughout the vehicle helped save about 9 more tons.

* Armor protection was not included as part of the basic vehicle, but was packaged into removable kits. The armor kits can be attached before a battle engagement. That helped cut the weight by more than 4 tons.

Its redesign notwithstanding, the future of Crusader remains unclear. Defense Secretary Donald Rumsfeld directed a Pentagon-wide review of weapon programs, and Crusader will be among the most scrutinized systems, said defense experts. One problem, several experts said, is that the Army has not articulated specifically what role Crusader will have in the future force.