Stealth (was Re: This funny Rosswel bussines)

James Rogers (
Sat, 12 Jul 1997 15:26:11 -0700

At 10:04 PM 7/11/97 -0400, Michael Lorrey wrote:
>There are physical limits to stealth capability. Any "Stealth" vehicle
>can still be seen by radar from a certain range of angles. A stealthed
>vehicle is designed so that the large majority of angles at which radar
>is likely to hit it at are such that they are reflected in a direction
>different from that which it came from. This is passive stealth, which
>if maximized, is usually hard to detect. Incidentally, the flying saucer
>is the most stealthy shape useful in a flying vehicle.
>Active stealth, which can more effectively hide a vehicle from detection
>equipment designed for a specific range of emanations, will require the
>use of electrical, magnetic, or gravitational fields, all of which are
>capable of being detected by additional specialized gear.

You are presuming that alien "stealth" capabilities are similar to our own.
The well-known stealth capabilities of the US military is first or second
generation and relatively passive. The current experimental (mostly
classified) generation is starting to utilize active stealth techniques
which have vastly enhanced capabilities. Primarily utilizing advanced
"active" materials and smart composites, I have seen some *very impressive*
new stealth capabilities. I was on the engineering and science side of it,
but the US military was fairly drooling over the results.

>The most effective possibility is materials which absorb as much
>incoming radiation as possible. Some such materials are used today to a
>limited extent for radar absorption, but are only effective in absorbing
>diffused radar. The main beam reflection must still be redirected. It
>cannot all be absorbed. Even if fully absorptive materials are
>developed, it will then be possible to detect vehicles by the absence of
>background radiation, that which is being absorbed by the vehicle.

Some of the newer active materials can not only protect against several
forms of direct radiation without redirection, but they can generate a tiny
amount of return noise as well. The residual noise (a result of
imperfections in the materials) produces a much cleaner return spectrum
without the "hole" normally associated with some passive forms of stealth.
I know people have been working on computer controlled versions of these
materials that let you modify the return characteristics in realtime. I
understand that the computer controlled versions can not only give you the
full amplitude spectrum (from no return at all to a full strength return),
but can also modify some characteristics of the return signal. A very cool
technology with a ton of possible real world uses.

-James Rogers