Re: Blacker than Black

To summarise the summary:

To defeat active sensors, the stealthed object must not reflect in the
range used by the sensor.  The Mk1 eyeball is the receiving element of
a bistatic active system, with the transmitting element usually being
the Sun, but other light sources can be substituted, on an ad hoc
basis.

To defeat passive sensors, the stealthed object must not radiate more
than whatever is behind it, relative to the observer.  Glowing hot
steel in a glowing hot furnace furnace can be hard to see, once it has
matched temperatures.  With the background temperature of space being
about 3K, hiding from infrared sensors is hard.  With Earth's
atmosphere at about 273K, infrared stealth is easier.

The brightness of infrared emissions is proportional to the fourth
power of the temperature, so a stealthy object needs to radiate away
its heat in a direction that is not towards the observer and it must
not pick up heat from the sun, to remain cool.	Black is a bad color
for reflecting heat.  One of the best surfaces for not picking up heat
is burnished copper, but that is far from black, and will be very
bright from certain angles.  Being all-angle stealthy in space is
impossible and making yourself stealthy  to certain observers is hard
enough.  If you intend to do more than hang in space, absent some kind
of inertialess drive, stealth is impossible