Hi, Matt.
-=> MATT MC_CARTHY wrote to JIM HOLSONBACK <=-

First, about the 500+ mph thing - - the presentation graphics from
yesterday's roundtable and press briefing are now available at

http://www.caib.us/news/press_briefings/rt030711_present.html

One of the graphics there has the following :

FAQ:  How could the foam be travelling at 500 mph, if it only fell about
      60 feet?
ANSWER"
- Shuttle (including the foam) was moving at 2300 fps or 1600 mph.
- Foam has a very low "ballistic coefficient", much closer to a sheet of
  paper than to a cannon ball.
- Foam slowed down to about 1500 fps in 0.2 sec (about 60 ft of travel).
- Wing hit the foam with a relative velocity of ~800 fps or about
  550 mph.

 MM> Something is missing though in the pictures of the hole that I saw
 MM> attached to the news story I quoted from.

 MM> That nitrogen cannon shot was supposed to be aimed at the leading edge
 MM> of the wing section, to simulate the "actual impact",
yet, the 16" hole
 MM> was shown in a broad flat surface that bore no resemblance to a
 MM> 'leading edge', and further, there were no signs of any 'heat tiles' in
 MM> place.  It was _my_ belief that the leading edge and the underside of
 MM> the wing were covered with heat tiles.

 MM> ???????????
 MM> Makes me wonder...

They moved the impact point a bit for the latest tests -  I forget why
they said they did that.

The hole is in the upper surface of RCC wing panel 8.  If you can go to
the above-cited webpage, the pictures there will make it more clear than
a lot of words could.

The RCC panels are used in the hottest places, like the nosecone and
wing leading edges.  There is a good overall writeup of the Orbiter tps
system available at

www-pao.ksc.nasa.gov/nasafact/tps.htm

Below are some excerpts, with a lot of interesting info deleted for
brevity.

 - - -  JimH.

 **********************
John F. Kennedy Space Center - Orbiter Thermal Protection System
      KSC Home PageSite SearchFAQ'sSite SurveyCustomer ForumNASA
      CentersPrivacy StatementHeadlines

ORBITER THERMAL PROTECTION SYSTEM
KSC Release No. 11-89
February 1989
Materials Chart KSC News Releases KSC Fact Sheets


 There are approximately 24,300 tiles and 2,300 Flexible Insulation
 Blankets on the outside of each orbiter.

 The orbiter's nose cone, including the chin panel, and the leading
 edge of its wings are the hottest areas during re-entry. When
 maximum heating occurs about 20 minutes before touchdown,
 temperatures on these surfaces reach as high as 3,000 degrees F.
 Reinforced Carbon-Carbon (RCC) is a light gray, all-carbon
 composite. RCC, along with inconel foil (metal) insulators and
 quartz blankets, protect the orbiter's nose, chin, and wing leading
 edges from the highest expected temperatures and aerodynamic forces.
 It also is used in the arrowhead area at the forward section of the
 orbiter where the external tank is attached. RCC is used there for
 shock protection during pyrotechnic separation of the external tank
 from the orbiter.


 About 70 percent of an orbiter's external surface is shielded from
 heat by a network of more than 24,000 tiles formed from a silica
 fiber compound. More advanced materials such as Flexible Insulation
 Blankets have replaced tiles on some of the upper surfaces of the
 orbiter.

Coated black tiles-known as High-Temperature Reusable Surface
 Insulation (HRSI)-cover the lower surface of the orbiter, areas
 around the forward windows, upper body flap, the base heat shield,
 the "eyeballs" on the front of the Orbital Maneuvering System (OMS)
 pods, and the leading and trailing edges of the vertical stabilizer
 and the rudder speed brake. The black tiles are located where
 temperatures can reach as high as 2,300 degrees F.

 Coated white tiles-known as Low-Temperature Reusable Surface
 Insulation (LRSI)-are designed to insulate the spacecraft from
 temperatures up to 1,200 degrees F. LRSI tiles were originally used
 extensively, but are now replaced in most areas by Flexible
 Insulation Blankets. LRSI is still used on the upper surface of the
 forward fuselage above the crew windows and on some parts of the OMS
 pods.

Tiles vary in size, thickness and density. HRSI tiles are generally
 6 inches square; thickness varies from 1 to 5 inches. They come in
 different densities: 9- and 22-pound- per-cubic-foot tiles. LRSI
 tiles are larger and thinner, generally 8 inches square and from 0.2
 to 1 inch thick. LRSI tiles come in 9- and 12-pound-per-cubic-foot
 densities.


 Most of the LRSI tiles and FRSI blankets have been replaced by
 Flexible Insulation Blankets (FIBs), composed of a waterproofed,
 quilted fabric with silica felt between two layers of glass cloth
 sewn together with silica thread. The average FIB weighs 4.9
 kilograms or 11 pounds per cubic foot.
 The blankets have better durability, and cost less to make and
 install than the tiles. They are used on the upper sidewalls of the
 orbiter's fuselage, sections of the payload bay doors, most of the
 vertical stabilizer and rudder speed brake areas, the outboard and
 aft sections of the upper wing, parts of the elevons, and around the
 observation windows.
 Some of the HRSI tiles have been replaced by Fibrous Refractory
 Composite Insulation (FRCI-12), which are less dense than the
 22-pound-per-cubic- foot HRSI tiles but comparable in strength. They
 are used around penetrations and leading edge areas.
 


... Inquiring minds want to know. - Bubba
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