stealth technology
AEROSPACETESTINGINTERNATIONAL.COM // SEPTEMBER 2019 39
Despite the technology now
dating back to the 1970s,
there are still many
misconceptions about what
stealth technology is, how it works and exactly what it
does. Stealth doesn’t make an aircraft completely
invisible. Instead, stealth applied features make an object
smaller in terms of its radar return. A radar can still see
or detect stealth platforms - it simply does this at a much
shorter range.
During the late 1970s and early 1980s, stealth use
was limited to two main techniques. Reflecting radar
waves away or absorbing as much of the
radar wave pattern as possible, leaving
only a small return to be detected by the
emitting site.
Its practical application in the US was
1998
Year the F-117, the
world’s first stealth
aircraft, made its
by Soviet mathematician and physicist,
Peter Ufintsev, in his 1964 paper titled
“Method of edgewave in the physical
theory of the fraction”. Ufintsev’s paper
determined the basics of radar wave
behavior and that the strength of the
radar return was related to its edge configuration, not its
size. The paper also explained how to calculate the
radar cross section (RCS) across a winged-surface and
along its edge.
first flight
The theory proved that, although reducing the RCS
is a major component of stealth, it is not the only one.
Lowering the RCS can make an aircraft’s infrared,
ultraviolet, electromagnetic, visual and acoustic
signatures more pronounced to the extent that they can
become the prime means of detecting stealth platforms.
Therefore, to be truly stealth, these signatures also need
to be reduced. Ufintsev’s study determined the basics of
stealth and defined the look of the second-generation of
stealth aircraft.
STEALTHIER TECHNIQUES
Second-generation stealth technology would adopt the
edge-aligned planform technique that, when used with
specially developed radar-absorbent
material (RAM), would provide the best
capabilities at the time to hide an aircraft.
The technique worked by reflecting and
dispersing radar energy away from the
source, making it difficult to detect and
track. Although the types such as the
F-117 was able to divert radar energy
away from its source, it could still be
detected by passive receivers as it made
its way through enemy airspace. So, for
stealth pilots at the time, mission profiles and tactics
played a significant role, with air crews planning their
missions so they could avoid the then known
vulnerabilities of the aircraft.
This idea of using tactics to mask the known stealth
flaws of the F-117 would prove disastrous. On March 27,
1
WHAT IS A RADAR
CROSS-SECTION?
A specific parameter of
a reflective object that
depends on many factors,
radar cross-section is
measured in units of m².
The calculation of the
radar cross-section is only
possible for simple objects.
The surface area of simple
geometric bodies depends
on the shape of the body
and the wavelength, or on
the ratio of the structural
dimensions of the object to
the wavelength. If absolutely
all of the incident radar energy
on the target were reflected
equally in all directions, then
the radar cross-section would
be equal to the target’s cross
sectional area as seen by
the transmitter. In practice,
some energy is absorbed
and the reflected energy is
not distributed equally in all
directions. Therefore, the radar
cross-section is quite difficult
to estimate and is normally
determined by measurement.
The target radar cross
sectional area depends on:
• The airplane’s physical
geometry and exterior
features,
• The direction of the
illuminating radar,
• The radar transmitters
frequency,
• The used material types
“Stealth is just a vital as it has always been,
but has to be balanced with agility and the
capability to deploy weapons quickly”
1 // Ten years after the F-117
was developed the
advancement of super
computers allowed
Northrop Grumman to
develop a smooth
contoured design with a far
greater wing sweep
(Photo: USAF)
/AEROSPACETESTINGINTERNATIONAL.COM