Air Warrior Col. John W. Thompson - KMI Media Group
Air Warrior Col. John W. Thompson - KMI Media Group
Air Warrior Col. John W. Thompson - KMI Media Group
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craft must operate in both heavy and light sea-state and craft speed<br />
environments,” he explained. “What might work well to protect the<br />
operator during a high shock environment may not be ideal for a low<br />
shock environment and vice versa.”<br />
Seaspension Technologies in Largo, Fla., produces shock mitigating<br />
seating equipped with a patented damper and coil system that<br />
automatically reacts to the force being exerted on it. “We basically had<br />
a global damper manufacturer tweak an existing shock absorber with<br />
our input,” said company President Peter Burer.<br />
Seaspension, which started in the recreational boating market,<br />
first supplied shock mitigating seats to the Canadian Coast Guard<br />
around eight years ago. “We’ve had no failures with these shocks,”<br />
said Burer.<br />
More recently, Seaspension delivered custom shock mitigating<br />
seating for use in 35 U.S. Coast Guard specialized emergency rescue<br />
airboats, known as Iceboats. The tripod-mounted seat is designed to<br />
protect the crew from jolts experienced when the boat transitions<br />
from land to ice and water, and during operation in rugged conditions.<br />
Seaspension also has supplied seating to Edgewater Power<br />
Boats of Edgewater, Fla., for vessels that were delivered to the Trinidad<br />
Coast Guard.<br />
Active Shock LLC of Manchester, N.H., which concentrates on<br />
shock absorbers in the automotive space, developed a device for the<br />
U.S. Special Operations Command designed to be incorporated in a<br />
rigid inflatable boat (RIB). That project, developed under a SBIR grant<br />
in 2008, has not been acquired by the U.S. military.<br />
“What makes our shock absorbers unique is that they are controlled<br />
by computer,” said Scott Martineau, the company’s director<br />
of business development. “We use sophisticated algorithms that take<br />
information from a suite of sensors contained in the shock absorbers<br />
themselves to determine the optimum damping rate. In high sea<br />
states, the sensor can detect when the boat goes airborne and prevents<br />
the seat from bottoming out and transmitting the shock to the crew.”<br />
Seaspension, meanwhile, will soon be introducing a shock mitigating<br />
seat for use as either a bulkhead seat or as a replacement for<br />
the Marine Corps’s 11-meter RIB. “The damper system will allow anywhere<br />
from the fifth percentile female by weight to the 95th percentile<br />
male in the Marine Corps to be seated and protected from shocks<br />
without the use of tools or any kind of adjustment,” said Burer.<br />
That would cover women as light as 100 pounds to men as heavy as<br />
250 pounds.<br />
“The mechanism in the damper responds directly to forces,” said<br />
Burer. “The Navy is looking for a seat that can accommodate different<br />
sizes of personnel on a variety of missions subjected to different sea<br />
states without having to adjust the damping mechanism.”<br />
Seaspension’s new device uses a dual-damper system in order to<br />
accomplish that task. “We found it better to incorporate two independent<br />
shock absorbers to regulate those weights,” said Burer. “The seat<br />
is designed to be able to slip right into existing craft in the inventory<br />
of U.S. special operations and foreign militaries as well.”<br />
The principles central to shock mitigation are applicable not<br />
only to seating and the protection of crewmembers, but also to the<br />
protection of equipment mounted on vessels. “We are working on<br />
several new applications for our pedestals to be used as weapons and<br />
equipment platforms,” said Burer. “We recently bid our heavy duty<br />
pedestal as a mount for a .50 caliber gun on a 100-boat contract. We<br />
expect shock mitigation to be used much more in this application in<br />
the future and are actively testing and designing products to meet<br />
this demand.”<br />
14 | SOTECH 8.9<br />
Taylor Devices makes shock mitigation products that have been<br />
used on Navy warships for shock isolation on missiles and missile<br />
systems, radars, electronics consoles, boat davits, and for recoil isolation<br />
on heavy machine gun mounts. These “soft mounts,” which are a<br />
combination coil spring and hydraulic shock absorber, reduce the firing<br />
recoil from the .50 caliber heavy machine gun from 4,400 pounds<br />
to 500 pounds, according to Taylor. This allows the .50 caliber guns to<br />
be used on smaller combatant craft.<br />
The application of shock mitigation technologies can have the<br />
unintended side effect of allowing crews to push a vessel to the limits<br />
of its performance, a phenomenon which has both positive and<br />
negative implications. As crews become more comfortable, they push<br />
the boats harder, and as they push the boats harder, the more they<br />
are likely to be subject to additional wear and tear. That is especially<br />
the case when shock mitigation has been retrofitted onto a<br />
legacy platform.<br />
“As operators feel secure in the seat and comfortable at higher and<br />
higher speeds they have been driving the boats faster,” said Gezari,<br />
referring to the Mark V. “This allows them to run their missions faster<br />
and more successfully. But the boats have also experienced structural<br />
issues as a result.”<br />
For Holmes, special operations crews will best benefit when vessels<br />
are properly designed and evaluated for their shock absorbing<br />
properties from the beginning. The Special Operations Craft Riverine,<br />
he pointed out, does not have the same history of musculoskeletal,<br />
boat-related injuries as the Mark V or the Naval Special Warfare Rigid<br />
Inflatable Boat (NSW-RIB).<br />
“Health monitoring of the shock environment in manned areas<br />
of combatant craft needs to be implemented on all combatant craft,”<br />
said Holmes. “Monitoring of the shock environment will provide data<br />
that will be used to assist future research and measure how effective<br />
proposed systems are against mitigating shock.”<br />
Research is yielding a set of emerging standards that will likely<br />
find eventual widespread adoption and which will help in the measurement<br />
of the shock conveyed to the human body through vessels. The<br />
International Organization for Standardization, a Switzerland-based<br />
group, has released ISO 2631-5, a standard to measure vibration on the<br />
human body over time. Another emerging industry standard relating<br />
specifically to shock mitigating seats is known as SED-8 and is based<br />
on another ISO standard.<br />
“SED-8 measures the amplitude and frequency of incoming<br />
impacts and then measures the outgoing response” of the seat,<br />
explained Burer. “Different seat manufactures employ different kinds<br />
of tests to measure the shock absorbing capacity of their systems.<br />
With this standard, we can measure the effectiveness of the<br />
damper system.”<br />
At some point in the not too distant future, Burer predicted, a<br />
certification program for shock mitigating seats under SED-8 will be<br />
established.<br />
Meanwhile, NSW will be assessing all future combatant craft<br />
for operator exposure to shock levels that could cause musculoskeletal,<br />
boat-related injuries, said Holmes. The current combatant<br />
craft, medium requirements document contains a maximum<br />
spine stress dose shock exposure level, as defined by SED-8 and<br />
ISO standards. O<br />
For more information, contact SOTECH Editor Dave Ahearn at davea@kmimediagroup.com<br />
or search our online archives for related stories at www.SOTECH-kmi.com.<br />
www.SOTECH-kmi.com