Evening star., 1962-08-09
5EMINI
Spoceship Return Depends
On Computer-Pi|ot Team
GEMINI
Continued Frnrn par. a.,

senses changes in velocity in
all three planes. It then makes
q computation to find out Il
q zero-hft trajectory viii drop
the spacecraft at the predicted
point"
Unlike Mercury, whose re-
entry was a matter of "fire
the retros and let her drop. /"
Gemini's return to earth win
De precise and manageable. It
consists Of two phases: re-en-
try, in which the computer does
the flying correcting course to
bring the spacecraft at last into
a 20-by-20-mile ball park" at
an altitude Of about $4,000
feet; and landing. in which the
Astronaut takes over and pi-
lots the craft to a three-point
touchdown on a normal-sized
landing field somewhere within
the ball park"
Actual re-entry begins when
the pilot pushes q button to
fire retro-rockets. His time cue
comes from the on-board COM
puter, which gives him a pam
el-hght warning several min
utes IN advance, a second one
about half-a-minute before
hand, and the "go" signal at
the proper instant to fire.
As in the Mercury re-entry,
the spacecraft is flying with
its blunt end forward so as to
have its heat shield bear the
brunt Of re-entry frictional
heating. This means the crew.
men are facing backward. Also
like Mercury, the Gemini craft
starts its re-entry in a slow.
stabilizing roll. But there the
similarity ends, owing to
Gemini's capacity for aerody-
manic lift. This lift Is achieved
by designing the spacecraft
with its center of gravity about
three inches off the center line
Of the long axis, instead of di-
rectly on the center line as in
Mercury.
So long as the computer
senses the re-entering space
craft to be aimed correctly it
leaves the craft in its rolling
mode and makes no trajectory
corrections. This roll keeps the
offset center Of gravity rotat-
ing around the crafts long
axis, thus cancelling out any
lift. The computer is designed
so it cannot accidentally put
the spacecraft into too steep a
descent; such negative lift"
could have catastrophe results.
If the computer sees the
crafts trajectory straying off
course, it halts the slow roll
and adjusts the future course
by changing the relative loca-
ton Of the spacecraft's center
of gravity. This raises the
blunt end of the capsule to
provide lift. Oddly enough, at
the time the craft is in a
maximum-lift condition the as
tronauts are flying not only
backward but upside down as
well.
Chute Is Elected l,.
The computer's Job is fin
ished when the descending
craft - now coming straight
down, blunt end furst-is some
where over the ball park"
about $4,000 feet UP. A small
drogue parachute is elected,
starting deployment Of q huge
sail-like canopy called a para
glider.
The paraglider, also known
as the Rogallo wing for its in
ventor, Francis M. Rogallo Of
NASA's Langley Research Cen
ter, Hampton, Va, is expected
to give the astronaut as much
control as the pilot of an Kills
airplane enjoys. Fully de-
ployed, the paraglider will look
vaguely like a child's folded
paper airplane. It will be about
40 feet long and triangular in
shape, with its leading edges
and certain other parts inflated
by air pressure for structural
rigidity.
Deployment of the paraglider
is expected to re gradual and
far more gentle than the quick
tug of an opening parachute.
For a few seconds, as 1t un-
folds, the big cloth sail will re-
semble a partly inflated balloon.
1t will damp side-to-side oscil-
lation of the descending space
craft and also slow the rate
of fall. Then, as it acquires
its normal shape and begins
to function as a glider, the wing
will tilt the spacecraft over sol
that the crewmen at last are
sitting upright and looking for
ward through their front-fac-
ing windows.
Thus prepared for landing,
the pilot switches from space
man to airplane driver. His
sole remaining task will be to
put the craft down just as he
would land an Kills. Like the
Kills, Gemini will have skids
on which to land. A nose skid,
put down automatically when
the paraglider is deployed. will
replace the tiny nose wheel Of
Kills, but the tail skids, lowered
by the pilot just before land
ing, will be practically identi-
cal to those on the swift rocket
plane.
Gable Links Into Steering
How does the pilot fly the
spacecraft on final approach?
Just as he would fly an air
LOST