By Mr. Eric Kowal (RDECOM)May 9, 2011
PICATINNY ARSENAL, N.J. - Xenophon, a professional soldier and writer of ancient Greece, is known for a succinct saying: "Fast is fine, but accuracy is everything."
Modern-day Soldiers who fire mortars and artillery would certainly attest to the importance of accuracy, yet verifying the pointing accuracy of a weapon has long been a problem at many government and contractor test facilities.
Engineers often resorted to inserting a long rod in the cannon bore or scribed a line on the outside of a mortar or howitzer cannon.
They then placed an optical instrument, called a theodolite, at just the right position to align specific points on the long rod, or scribe line, to the vertical hairline of the theodolite.
This process was not only very time consuming, but it was highly dependent on the skill of the theodolite operator, especially when the cannon was at a high angle.
Additionally, the process could only measure azimuth, not both elevation and azimuth.
Enter the Bore Elevation and Azimuth Measurement System (BEAMS), invented and developed by engineers within the Fire Control Systems and Technology Directorate (FCS&TD) at the Armament Research, Development and Engineering Center (ARDEC).
BEAMS provides the Army with a low-cost technique to accurately measure, in a field-test environment, the elevation and azimuth pointing performance of a weapon system so it can be compared against its accuracy requirements.
FAST TRACK DELIVERY
The initial request for such a capability, which was needed for the Naval Surface Warfare Center's 81mm mortar fire control system, came to Robert Pinto in 2007 through PM Mortars.
Pinto, an engineer in the FCS&TD, consulted with John Casper, Competency Manager for the Artillery Fire Control Systems Division of FCS&TD. Casper recommended the use of the dual-theodolite measurement technique. Pinto then developed the method of BEAMS operation along with an Excel spreadsheet to perform the needed computations.
Pinto also worked closely with Jeffrey Gregor, a mechanical engineering technician in ARDEC's BenAfAt Labs at Watervliet Arsenal, N.Y. Gregor was responsible for generating the formal design drawings and producing the technical data package for the laser fixture.
Mechanical fabrication of four laser fixtures was done at the Benet Manufacturing Prototype Center under the direction of Leonard Darcy and his toolmakers: Jack Reckner, Stanley Rysio, Howard Steller, David Hale and David Boudreau.
The result was a 26-inch aluminum alloy laser fixture that, when fitted with lobes to match the 120mm Mortar cannon, weighs six pounds.
"From the time funding was approved to the time a product was developed was roughly 60 days," Pinto said.
The laser fixture was designed to be as small as practicable for ease of operation and transport in an engineering, field-test environment.
USING EXISTING TECHNOLOGY
"Its design provides elegantly-simple functionality and its anodized red finish gives is a modern-art appearance," Pinto said. Red is typically the color of fire-control devices that do not remain on the weapon during firing.
BEAMS uses an existing Army eye-safe laser currently used as a means for zeroing weapon sights from small caliber through grenade launcher.
The laser provides a projection of the tube's axis beyond the end of the cannon which can be viewed with magnifying optics, such as the telescope of a theodolite.
The laser fixture incorporates interchangeable lobes that can be used with various weapon tube calibers, including the 120mm, 81mm, and 60mm Mortars. The BEAMS laser fixture self-centers on the weapon tube axis on non-marring brass pads and spring-loaded plungers.
"By making horizontal and vertical theodolite observations of the laser at two positions along the path of the beam, the three-dimensional coordinates of the two positions can be computed," Pinto said.
In operation the two theodolites are positioned at any convenient locations around the weapon from which they can observe both laser points. The theodolites are oriented to known horizontal and vertical references such as north and the horizontal level plane using conventional surveying methods.
The theodolite operators then measure the horizontal and vertical angles to the opposite theodolite and to each of two points along the laser's path as the laser strikes a screen.
Each of these measurements has a clearly defined aim point which removes subjectivity and operator error from the measurement.
From this data the spreadsheet computes a three-dimensional position of each laser point. From these positions, it computes the elevation and azimuth of the laser line, which is right in line with the elevation and azimuth of the weapon bore.
Depending on the position of the theodolites with respect to each other and to the two laser points, measurement accuracies as fine as 0.05-mils (0.0028-degrees) in elevation and azimuth have been achieved.
To put it into perspective, 0.05-mils is roughly the angle of the diameter of a penny at a distance of slightly less than a quarter-mile.
BEAMS has various advantages:
-- Extremely compact laser fixture with the ability to accurately self-center in the weapon tube.
-- Ability to work with any caliber weapon system.
-- Means to calibrate and verify that the projection of the tube axis is coaxial with the actual tube axis.
-- Means to position the theodolites at virtually any arbitrary position.
-- Clearly defined theodolite aim point.
-- Ability to simultaneously measure elevation and azimuth with precision.
APPLYING BEAMS TO OTHER WEAPONS SYSTEMS
Since its inception, there have been numerous tests involving BEAMS spin-off applications. Most notably, from June 2008 to March 2009 ,the Joint Program Management Office LightWeight 155mm Howitzer, now know as PM Towed Artillery Systems (TAS), became interested in BEAMS to measure the pointing accuracy of the 105mm M119A2 Howitzer.
During that time, Pinto worked closely with TAS and Yuma Test Center (YTC) personnel to design a laser fixture, known as the "Dart" for the howitzer, and to develop the methodology to produce reliable and repeatable measurements on that weapon platform.
In January 2009, YTC personnel visited Picatinny where Pinto trained them on making BEAMS measurements. Later in 2009, Pinto along with YTC personnel conducted BEAMS pointing accuracy tests of PM Light Armored Vehicles' (LAV) 120mm mortar for foreign military sales.
Also in 2009, Pinto and YTC personnel made hundreds of BEAMS measurements for PM TAS'sM119A2 Inertial Navigation System bid sample test.
In 2010, BEAMS was adapted to the cannon of the Rapid Response Force Protection System mortar and used to boresight the weapon.
BEAMS is currently being adapted to work with the 155mm cannon of the M109A6 Paladin to make pointing accuracy measurements of the system's new Dynamic Reference Unit Hybrid Replacement.
Last year, BEAMS received a patent from the U.S. Patent and Trademark Office. It was also nominated as one of Army's Greatest Inventions of the year.