*****PTSC NEWS FLASH***** STEALTH AT SEA
Stealth technology to stay under wraps
Stacey Evers
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Jane's Defence Weekly
Page 22
Stacey Evers reports on the low-profile progress of US stealth technology and its most promising developments
The USA's first stealth ship, the DD 21 land attack destroyer, will not begin entering the fleet in numbers until 2010. This gives the US Navy only a few more years to explore technologies that can reduce the surface combatant's magnetic, acoustic, infrared, radar and visual signatures.
Despite being open about its need for stealth, however, the navy wants to keep its specific research as low-observable as the technologies themselves. "Signature stuff is [classified] secret or higher. It's really tightly controlled," a navy spokeswoman said.
Officials with the navy's surface warfare division recognise that the DD 21 will probably not be stealthy so much as low-observable. This means the ship will be able to disrupt an enemy sensor's ability to detect, target and engage, but will not necessarily be completely undetectable.
Some of the more promising emerging technologies include composite and radar-absorbing materials that are in various stages of development. The Naval Research Laboratory (NRL) is working on a low-solar-absorbance topside enamel ship paint that would reflect solar radiation and reduce a ship's infrared signature.
The coating does this by replacing carbon black, which absorbs solar energy, with a mixture of red, yellow and blue pigments to create a grey colour that is transparent in the infrared (IR) spectral region. This formula preserves the low-visibility, haze-grey visible colour while reflecting several times more energy than carbon black in the IR region.
Other engineering solutions for low-observable ships involve ship shaping, hull design, decluttering the topside, coatings, and antenna designs. Signature requirements for the DD 21 may require a redesign of all topside components and their associated systems, according to navy officials.
"For the DD 21, the entire ship design is being approached from a systems engineering perspective," naval surface warfare experts said in a written response to questions from Jane's Defence Weekly. "Signatures now play a critical role in the design decision process for overall ship performance and for every system that has an observable characteristic such as radar cross-section, IR or acoustics."
Related to this potential redesign is a low-observable, multi-function stack advanced technology demonstration (ATD) programme being sponsored in FY98 by the USN Office of Naval Research (ONR). Engineers will demonstrate a surface ship composite exhaust stack with embedded multi-function satellite communications array antennas. This technology is expected to increase a ship's information warfare capability while reducing topside signature, volume, weight and mast antenna population.
Other methods for reducing IR signature include 'designing out' hot spots and exhaust plumes or using passive and active mixing/cooling measures to diminish the hot spots, the navy said.
The area of antenna redesign has received great emphasis from the navy. In FY99, the ONR anticipates funding a shipboard multi-function/multi-band receive shared aperture ATD to develop and demonstrate radar, electronic warfare and communication functions in a low-observable, dynamically reconfigurable, receive-only phased-array aperture.
Some work on multi-function radio frequency (RF) devices is already being pursued through the Advanced Multifunction RF Systems, which would integrate radar, communication and electronic warfare capabilities. The system, operating between 500MHz and 20 GHz, would be common to ship and air platforms such as the DD 21, Joint Strike Fighter, CV X and F/A-18E/F.
The programme has focused on critical technologies such as structurally embedded antennas, highly discriminating wide-bandwidth filters, and wide-bandwidth radiating elements. Recently, the focus has been placed on seven technology needs, including transmit/receive isolation and low-profile radiating elements.
The ONR recently awarded Patriot Scientific Corp a development contract for its ionised gas antenna, which would be used to transmit and receive RF signals for potential stealth communications.
Unlike a resonating metallic antenna, the Patriot technology is designed to allow RF devices to go undetected immediately after transmission, eliminating unwanted ringing and making signal processing harder to trace.
Photograph: Although the Arsenal Ship programme has been disbanded, much of the development work will be applicable to other low-observability/ stealth projects. (Photo: Northrop Grumman)
11/19/97
Copyright Jane's Information Group Limited 1997
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