MISSION CONTROL CENTER 
STS-70 Status Report #11 
 
Tuesday, July 18, 1995, 5 p.m. CDT 
 
  Discovery completed another trouble-free day on orbit as the crew
continued to tend a host of experiments ranging from optical studies
to biological investigations.
 
  Today the crew activated one study for the first time thus far, the
Microencapsulation in Space experiment, a device that will attempt to
produce a timed-release antibiotic medication in weightlessness. The
lack of gravity allows the encapsulation process to be performed with
much greater purity than can be achieved on the ground, according to
experimenters. The automated investigation will operate while the crew
sleeps.
 
  Earlier, the crew downlinked video images of bioreactor tissue
cultures that were described as better than any seen before by
investigators who are working to qualify the machinery for use on
orbit. The video showed orange colon cancer cells coalescing into
globules, some of which were described by Mission Specialist Mary
Ellen Weber as being as large as a pea. The bioreactor is a rotating
cylinder in which cells can be grown suspended in weightlessness
aboard the shuttle thus making them more perfect than ground-grown
cultures. The bioreactor experiment has now moved to its second phase,
an observation of the currents created in the fluid inside the device
that uses colored plastic beads to record the movements.
 
  Also this morning, the crew noted a small nick on the outside of one
of the shuttle's exterior window panes apparently caused by the impact
of a micrometeorite sometime during the sleep period. The tiny crater
is estimated to be only a sixteenth of an inch in diameter and one
thirty-second of an inch deep, posing no problems for the spacecraft.
The exterior window pane alone is more than half an inch thick, and
several more window panes -- together almost two inches thick -- are
located between the exterior and the interior of the cabin.
 
  In other work, the astronauts continued observations of Earth using
the HERCULES video camera and of the shuttle itself using the Windex
experiment. Windex observed the environment around the shuttle during
a simultaneous waste and excess drinking water dump from the
spacecraft.
 
  Mission Control put the crew to bed for the day with the theme from
the movie Starman.  The eight-hour sleep period began at 2:42 p.m. CDT
today. The crew will awaken at 10:42 p.m. tonight.
 
-end-