Sophisticated new weapons mean today's fighter pilot must be prepared for a host of hidden dangers
DeeDee Doke/LONDON AND ST ASAPH
From chemical agents to laser beams, the dangers to military aircrew are escalating. Protecting aircrews to a high level of impenetrability is assuming greater importance as sophisticated new weapons increasingly target the physical vulnerabilities of the humans working inside the airframe.
In addition to ongoing development of sensors and warning devices to ward off the assault of unconventional weapons, the US services in particular are aiming to create individual components of a mask of impenetrability to protect the eyes and respiratory systems of aircrews - and, ultimately, to safeguard their missions.
"The marketplace is now catching up with the threat," says Brian Taylor of the North Wales-based Thales Optics, a long-standing player in laser eye protection. Last year, Thales, then Pilkington Optics, delivered laser eye protection spectacles to the US Air Force in a quick-turnaround contract following USAF chief of staff Gen Michael Ryan's call for increased aircrew protection in the wake of laser incidents in Bosnia.
"It's an evolving technology," Taylor adds of laser eye protection. "The customer tends to drive it forward, and we're being pushed as far as technology will allow."
One USAF-led project in particular promises to benefit all the US services. The Joint Service Aircrew Mask (JSAM) is intended to integrate nuclear, biological and chemical (NBC) and gravity, or g-force, protection, bridging the often criticised commonality and logistic gaps between the branches - as well as provide a single system to do the work of at least two. "Right now, we don't have a mask that does both jobs," says JSAM programme manager Pat Tiner.
Sean Mahoney, JSAM project manager for Gentex, one of two US firms developing prototypes during the project's product definition and risk reduction (PDRR) phase, says: "It's certainly the most comprehensive respiratory programme to date."
JSAM Prototypes
Although the programme's roots stem from the mid-1980s, the current PDRR phase of JSAM's development began last July with the competitive award of two contracts to, respectively, Gentex of Rancho Cucamonga, California, and Science Applications International (SAIC) of Abingdon, Maryland. Prototypes are set for delivery next January. After the US Government tests the prototypes, Tiner says, one contract will be awarded under "full and open competition" for the completion of development and production. JSAM is due to enter service in June 2006.
The levels of protection prescribed under the key performance parameters for the mask are, according to senior systems engineer John Rogers:
chemical: provide eye and respiratory protection with a quantitative fit factor (QFF) of 20,000 against a vapour challenge of 20,000mg-min/m³. (QFF is the ratio of agent concentration outside the mask to the concentration of agent inside the mask.) Also, it protects against liquid and/or vapour chemical agent permeation through system materials for 16h; biological: provide eye and respiratory protection against biological agents with a QFF of 50,000; anti-g protection: when integrated with a "pressure breathing for g system'' such as COMBAT EDGE (Combined Advanced Technology Enhanced Design G-Ensemble), to provide an effective mask seal up to 9g for 30s. Provide aircrew protection/endurance during air combat manoeuvering flight equal to current systems.The mask is intended for almost all aircraft platforms in the US services - a total of 108 including variants as well as the USAF's upcoming F-22 Raptor and Joint Strike Fighter. Ultimately, however, there may be more than a single JSAM design, says Alex Slate, team leader for NBC protection equipment: "There is a possibility that there will be two to three variants when the programme is finished."
The platforms are broken down into three categories: Tacair, or tactical air, which require g-protection; the heavies, which are fixed-wing aircraft not requiring g-protection; and helicopters. "It may be possible that we have a helicopter variant and a Tacair/heavy variant, or that we have a helicopter/heavy variant and a Tacair variant," Slate says.
JSAM must interface with a number of different helmets, and specific variants will be usable with or without oxygen. "We will also be addressing pilots who sometimes don't wear helmets at all, or for escape and evasion scenarios where a helmet will be a hindrance," Slate adds.
The challenges facing JSAM designers are considerable. First, the system must interface with helmet-mounted systems such as night vision goggles (NVGs) and aircraft weapon systems such as the Boeing AH-64 Apache's Integrated Helmet and Display Sight System (IHADSS) and the Boeing Sikorsky RAH-66 Comanche's Helmet Integrated Display and Sighting System. "These helmet-mounted systems, particularly the AH-64 IHADSS, complicated integration because of their very small eye relief,'' says Rogers, referring to the distance from the cornea of the eye. "The AH-64 integration challenge may require development of a unique variant," he adds.
Design limits
Some cockpits are smaller than others. And in addition to interfacing with NVGs and aircraft weapons systems, JSAM must integrate with the extensive array of in-service personal and life support equipment across the US military fleet. "This limits the overall design space and flexibility available to JSAM designers," says Rogers.
A possible area for innovation, however, is in materials. Gentex's Mahoney says "materials are always a key area in respiratory work".
Rogers explains that today's aircrew respirators have "shortcomings", which he lists as excessive thermal stress, bulkiness, inadequate head mobility, and integration with other life support equipment - all potential materials issues. "New materials will be investigated to determine their potential to reduce these undesirable characteristics of in-service respirators," he says.
Sixteen aircraft, reflecting a variety of US fixed- and rotary-wing capabilities, were selected for interface with JSAM during the preliminary design phase: the Boeing F-15 Eagle and F/A-18 Hornet, Lockheed Martin F-16; Lockheed Martin C-5 Galaxy; Lockheed Martin MC-130 and KC-130 Hercules; Boeing/British Aerospace AV-8B Harrier; Northrop Grumman EA-6B Prowler; Sikorsky Black Hawk variants including HH-60, MH-60 and UH-60; AH-64; Sikorsky RAH-66; Bell AH-1W Super Cobra; and Sikorsky CH-53 Super Stallion.
Also on the list, despite continuing problems with its development, is the Bell Boeing V-22 Osprey tiltrotor. "We plan on testing with the V-22 unless a decision is reached to discontinue the V-22 programme," says JSAM test manager Lt Randy Flores.
Slate says there has been informal discussion about JSAM with the UK Ministry of Defence, which is keeping an eye on the project's development. Conceivably, the UK "may well join" in on JSAM under the USA's Foreign Military Sales (FMS) programme, Slate says, although the USAF says there is no formal agreement with MoD at present.
In both the USA and the UK, laser eye protection technology has received considerable attention for more than a decade. In addition to Bosnia, however, other situations have pushed concern over lasers' increasing availability into the global consciousness.
In the mid-1990s, China's North Industries Corp offered for export sale a laser weapon that was said to be able to cause eye injuries at more than 3km, nearly 5km with a magnifying optic. Last year, a British Airways pilot was dazzled by a laser light show in central London as he flew an aircraft over the city. Today, lasers with injury-inducing potential can be found for sale on the internet. Dr Ilya Eigenbrot of London University's Imperial College, who works with lasers in cancer research, spotted a visor with a collimated beam laser mounted on the front for sale in a London second-hand store. "Government controls are just abysmal," says Eigenbrot on the availability of lasers on the open market.
While laser eye protection has been available to many of the world's militaries for some time, demand is increasing for ever more versatile and flexible gear with a long list of qualifications: peripheral or wrap-around vision; protective against a broad range of wavelengths; capable of being integrated with prescription eyewear, NVGs, life support equipment; able to support the wearer in a variety of lighting conditions; light weight; and able to shield the wearer from ballistic weapons.
Although the USAF began receiving its latest laser eye protection, Thales' Clear Laser Eye Protection Infrared (CLEPIR) spectacles, just last September, the service also last year awarded two PDRR contracts of $1.5 million each to Kaiser Optical Systems and Rockwell Science Center in the race against time to develop the follow-on generation.
"There will be no downselect per se," says programme manager Gary Trammel. "Instead, a new request for proposals for the engineering and manufacturing development [EMD] phase will follow shortly after."
US military co-operation
The US Navy is co-operating with the US Marine Corps and the US Army on two separate programmes to develop enhanced laser eye protection.
The USN-led Joint Advanced Laser Eye Protection Visor is a navy-army programme to develop a day/night (unaided) multiple wavelength visor that protects fixed and rotary wing aircrew in a fixed multiple wavelength environment. It is designed to be compatible as a helmet component with the USN/USMC and Army aviation life support equipment (ALSE), cockpit displays, fire control and weapons systems. Holographic Optics of Millwood, New York, is the primary contractor. The USN/USMC's Laser Eye Protection Improvement Program (LEPIP) EDU-5/P Spectacles differs slightly in form - spectacles instead of a visor - and compatibility. The spectacles are designed to cause minimal visual and physical encumbrance and be compatible with USN/USMC ALSE, aircraft visual displays, night vision systems and weapons systems. Kaiser Optical Systems is the primary contractor on the ongoing $2 million-plus contract, which was also awarded in September 1996.In the UK, work on laser protection technology has been underway at the Defence Evaluation and Research Agency (DERA) and its predecessor organisations for over 15 years. Today, says DERA, its researchers are looking at "any practical method of eye protection with particular emphasis on protection of the bare eye". DERA says its key thrust is looking at tuneable, or adjustable, devices capable of broadband protection - meaning against any wavelength within the visual range of the eye, while still allowing the wearer to function near normally.
US sources believe that tuneable lasers themselves will likely have been developed by 2005.
"Different lasers operate at different wavelengths, and you have to modify and create new designs to meet those needs. You can protect against every wavelength, but what you would have is a tin bucket. It's always a balance - a critical balance," says Thales' Taylor.
For instance, taking a particular colour out of the spectrum for the protective gear "could spell disaster", Taylor says, as it could affect an aircrew member's ability to see portions of a cockpit display that have that colour. To handle that problem, Taylor says, a lens coating would have to be developed that removed only "a small and narrow portion" of that colour in the spectrum.
Many laser eye protective systems rely on filters created by dyes embedded in plastic. The laser light would be absorbed within the filter's thickness, and the laser energy dissipated as heat. Disadvantages of that technology, used in helmet visors, include difficulties in integration with night-vision equipment, darkening the environment too greatly for night operations and making cockpit displays illegible.
Reflective lasers
Research and development into laser eye protection is focusing on reflective technologies - dielectric stacks, hologram and rugate - in which the laser energy is reflected away from the user. At this time, these coatings are applied to the external surface of an optical lens blank made from polycarbonate or CR-39 plastics and then, for holograms and dielectric stacks, a protective cap is applied to create a laminated structure. As applied to polycarbonate by Thales last year in creating the lightweight CLEPIR for the USAF, dielectric films stacked in alternating quarter wavelength layers weaken invisible "out-of-band" infrared- and ultraviolet-frequency light. A hologram is a three-dimensional image formed by the interference of light beams from a coherent light source. Rugate is similar to dielectric stacks, but is corrugated with alternate ridges and grooves. Rugate technology has been successfully applied to glass, but the effects of applying it to plastic are still being determined.
Rugate offers "some increased protection in the visible portion of the spectrum", says senior systems engineer Joseph Jones, who works with the USAF project at Brooks Air Force Base, Texas. "There have been some leaps. But it's not a mature technology."
Observers say that a joint-service approach "seems to be evolving" toward laser eye protection in the US military, with the USA and the UK placing roughly the same high priority on a long-term solution.
Says Thales' Taylor: "Laser eye protection is a moving target."
Source: Flight International
