QUESTION:
Why all the saftey after the shuttle lands?  Is it becasue of explosive or
poisonous gases?  Also, can you give me an estimate on the speed at which it
touches down on the runway?

ANSWER from Jenny Lyons on March 28, 1997:
Launches and landings are certainly very exciting events.  Watching
a Shuttle launch is a powerful experience.  The sound and vibration
(even from where we are, 3 miles away) resonate right through you,
and night launches are so bright, they literally turn night into day.
I hope sometime you'll have the opportunity to see one in person!

Shuttle landings, at least for me, are a much more up-close-and-personal
experience.  And they are no less powerful.  As you probably know, the
Orbiter returns to Earth as the world's heaviest glider.  There are no
engines and no thrust, just the force of gravity pulling it down.  In
the Convoy, we are positioned near the end the runway as it lands.  We
catch our first glimpse of the Orbiter around the same time we hear the
two sonic booms, just a few minutes before touchdown.  The Orbiter is
still at an altitude of about 20,000 feet, traveling almost 500 miles
per hour.  From our perspective, it seems to drop like a rock out of the
sky.  It soars down to the runway with a roaring noise from the wind
rushing by, and glides to a stop about 9,000 feet from where it
originally touched down.  Touch down speed is usually about 200 knots.

After landing, the first people to approach the Orbiter are our "Safety
Assessment Team."  Before we give the astronauts the O.K. to remove
their protective suits or send any more of our Convoy personnel in, we
have to verify that everything is safe in and around the Orbiter.  You
are exactly correct in that the Safety Assessment Team has equipment to
sniff out both poisonous AND explosive gases.  They use protective
breathing equipment while they test the air around the Orbiter's vent
doors and exhaust ports.  The Orbiter is still "hot," with pressurized
tanks of toxic fluids and gases like nitrogen textroxide,
monomethylhydrazine and ammonia.  There is also always the potential for
leakage of other very flammable fluids and gases like hydrogen and
oxygen.  Once the Safety Assessment Team verifies that the atmosphere
around the Orbiter is clear, the rest of the Convoy can move in closer
and begin our work to help the astronauts out, remove time-critical
space experiments and prepare to tow the Orbiter off the runway.