On 8 Jul 2006 09:38:44 -0700, "Rich" wrote:

Saw a footage of liftoff last July 4th. When the boosters separated
from external tank, did the shuttle's engine take over or had it been
running since launch? There is no smoke/trail coming from the
shuttle's engine, unlike the boosters. Why is there no smoke?


The Shuttle's three Main Engines ignited at T-6.6 seconds before
liftoff. They burn liquid hydrogen and liquid oxygen. They produce an
orange flame during the startup, but quickly turn to clear, or blue
flame with no smoke trail. The byproduct of this is mostly water
vapor.

The launch pad uses water from a nearby water tower to prevent shock
waves damaging the shuttle when it is on or just off the pad and the
engines are running. Some of the water dumped onto launch pad is
vaporized by the engines, resulting in a huge, billowing, white cloud
of steam.

The Solid Rocket Boosters burn ammonium perchlorate and produce an
orange cloud of smoke.

Once the SRBs burn out, there's no more water being turned to steam at
that altitude and no SRBs producing orange smoke, so the Shuttle
becomes almost invisible.

Brian