LO Principles Flashcards
Objective of stealth
Increase survivability by REDUCING THE PROBABILITY OF DETECTION and exposure to engagement by threat system
Describe active signature/ examples
ALL THE OBSERVABLE EMISSIONS FROM AN AIRCRAFT
- RF Signals: comm, navigation, radar
- Acoustic: engine noise, prop noise
- Infrared: engine exhaust, skin temp
Describe passive signature/examples
ALL THE OBSERVABLE SIGNALS FROM AN AIRCRAFT RESULTING FROM EXTERNAL ILLUMINATION
- EO/Visual
- EM (radar)
Countering RF Active Signature Collectors:
Counter threat data collectors with ____________ designs.
Low Probability of Intercept (LPI)
Acoustic Signature Reduction: _________ are the primary source of noise
Engines
Radar signature is dominated by………
Shape
Why is RCS the most critical signature of most aircraft?
Radar provides all weather, long range detection capability (early warning)
Radar provide target range, azimuth, and velocity data (target tracking)
Stealth is enhanced by …. (3)
- Forcing Threats to use active sensors sparingly
- Using intel data to minimize onboard active and passive sensor exposure
- Use tactics that combine w/ order of battle as well as man made environment
Define RCS
RADAR SIGNATURE IS EXPRESSED AS AIRCRAFT RCS.
- Amount of energy scattered back to radar by a target
- Measure of power expressed as dBsm
Explain the factors that determine RCS size
Target Aircraft Factors: Azimuth, Elevation
Viewing Radar Factors: Frequency, Polarization
*** Vertically polarized waves generate significant return from wing TRAILING EDGES; Horizontally –> wing LEADING EDGES.
*** To reduce detection range by half (3 dB), the RCS must be reduced by 16
List 4 basic methods to make an aircraft stealthy
SHAPING (most important)
Absorption
Cancellation
Transparencies
Describe shaping
Reflect radar energy into any direction other than back to the radar site.
***AIRCRAFT SHAPING TO BOUNCE ENERGY IN SPIKES***
Describe absorption
Utilize RAM to turn radar energy into heat
Describe cancellation
Actively or passively reflected radar waves add together to cancel each other out
Describe transparencies
Allow radar energy to pass thru the material w/ minimal reduction in energy or change in wave characteristics
Describe faceted shaping
Orient flat surfaces to deflect radar energy away from threat radar
example: F117
Describe compound curve
Replace straight edges with curved edges to reflect less radar energy towards threat radar
Example: B2
Describe planform alignment
Return a radar signal in a very specific direction away from the radar emitter (all in the same alignment)
Example: F22
Goals of radar absorption materials
- Reduce specular and multibounce reflections
- Reduce energy diffracted from trailing edges or discontinuities by absorbing energy as the wave travels along the surface
List types of absorbers
- Resonent absorber (specific frequency)
- Nonresonant absorber (range of frequencies)
Characteristics of E-RAM
Resonant, causes waves to cancel each other out
- Narrowband
- Thick, but light
Characteristics of MagRAM
Nonresonant, coating with ferromagnetic materials
- Broadband
- Thin, but heavy
Characteristics of large volume RAS
Nonresonant, radar absorbant structure
- Broadband
- Thick, but light
How does the aircraft surface breaks and gaps affect total RCS
Residual reflections are caused by surface discontinuities, more significant with higher frequencies.
Reflections reduced by:
- Coating aircraft with RAM
- Filling gaps with RAM
