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Our First Moon Scout Heads for the Pad
Its three feet planted on rugged test terrain,
with pantograph arm extended, TV humming and high-gain antenna oriented toward distant
target, this is how Surveyor might look after making a soft landing on the moon.
This year a talented robot will try to "check out" the moon. Called "Surveyor,"
he's got three legs, electronic eyes and chemical senses
By Thomas E. Stimson, Jr.
Before we try to place human explorers on the moon, we are going to send up mechanical
men who will land on their three feet, look around and tell us what they see.
After one of them has touched down, he'll report what the lunar surface is like.
He'll scratch the ground with one hand to learn whether it's hard or soft. He'll
reach out with another hand to feel if micrometeorites are showering down.
This mechanical American will be pretty human in other ways, too. His eyelids
will close during landing, to keep dust out of his television eyes. If he suffers
too much from the searing heat of the lunar day, he'll adjust his interior temperature.
He'll go to sleep when the sun goes down, shutting off all of his senses except
his sense of feel for moonquakes, and use stored-up battery energy to avoid freezing
to death.
As a photographer, this extraordinary American will take stereo pictures and
transmit them back to earth so we can see what he sees, in three-dimensional color.
The name of this mechanical man is Surveyor. And, to carry the simile one step
further, his father is Caltech's Jet Propulsion Laboratory and his mother is Hughes
Aircraft Company. Both parents expect great things of their offspring.
The first Surveyor, in a planned series of at least seven attempts, will leave
for the moon later this year. The project is the last exploratory step before Apollo,
the manned space-craft that is scheduled for a moon landing in the early '70s.
Surveyor's role is to provide us with answers to questions such as these:
• Is the moon covered with a laye1· of dust? If so, how deep is it? (Despite
radar information and close-up photos taken by Ranger VII, this question continues
to generate controversy. Several scientists connected with the Ranger project maintain
that the lunar surface is essentially firm. Other scientists with equally good credentials
say just the opposite; they think the dust is deep enough to swallow up a space
vehicle.)
• Will moon dust clog mechanical purrs or even turn an Apollo spaceman into
a walking dust ball? (There's some evidence that dry dust in a high vacuum tends
to collect and cling to any surface.)
• Are tiny meteorites constantly raining down on the moon? (With no atmosphere
to slow them down, the high speed particles could slice through a space suit or
even the spaceman himself.)
But the first four Surveyors won't come up with all the answers. Instead of carrying
the full "lunar laboratory," they'll be outfitted mainly with flight instruments
designed to report the accuracy of the approach to the moon, how successful the
landing is and, if some-thing goes wrong, exactly what the nature of the trouble
is.
Landing strength is tested by dropping Surveyor from various
heights. Tether arrangement is used to duplicate the one-sixth earth gravity of
moon
Eugene Giberson, Surveyor project manager for JPL, explains that without these
pioneer flights there would be no way of correcting a malfunction. So, first the
vehicle will be proved out, then the full laboratory will be transported.
Giberson compares the job of making a soft landing on the moon to performing
a launch at Cape Kennedy in reverse. That is, the vehicle approaches at high speed,
at an angle. Then it must tilt tail-first toward the surface, slow itself down while
maintaining perfect balance, then drop in at almost zero speed into the preselected
site. And, adds Giberson, Surveyor must do all of this by itself after having spent
66 hours in the hostile environment of space.
Anatomy of an Atlas-Centaur. Drawing shows Surveyor cocooned
inside nose fairing atop Centaur upper stage, first rocket to use liquid hydrogen
fuel
After 66-Hour Trip (left panel), Surveyor will get command from
earth to turn and point big retrorocket straight down (right panel). Sixty miles
above target, rocket will ignite to slow craft from 6000 to about 400 m.p.h.
Even the blast-off from earth will be more critical than were the earlier moon
shots. Ranger VII was first put into parking orbit around the earth, then was fired
toward the moon at exactly the right time. This called for relighting the rocket's
second stage while in orbit, a tricky operation by remote radio command.
To avoid possible failure, the first Surveyors will be fired at the moon by direct
ascent. Each will travel toward a point in space that will be occupied by the moon
at the moment the vehicle gets there. The period of time in which the rocket can
be launched (the "launch window") is no more than an hour per day at best, on no
more than four or five days per month.
When Surveyor closes to within 1000 miles of the moon the craft will turn (on
command from earth) so that its big retro-rocket points straight down. At 60 miles
altitude the rocket will ignite and push backward with enough thrust to slow Surveyor
from its earlier 6000-mile-per-hour speed to less than 400 m.p.h. Explosive bolts
that hold the retro case (now burned out) will then free the case and allow it to
drop away.
Now RADVS goes to work. (Pronounced "radviz," the initials stand for Radar Altitude
Doppler Velocity Sensor.) One RADVS beam projects straight down to measure the altitude
and the vertical drop speed. Three other beams, at angles, will measure the craft's
speed and direction of travel across the moon's surface. RADVS automatically operates
three small vernier gas jets that will cut horizontal travel to zero, at the same
time reducing the drop velocity to 12 feet per second. The jets shut off at 15 feet
altitude to avoid stirring up moon dust, and Surveyor impacts at parachute speed.
Cutaway shows one of Surveyor's two TV "eyes." They are designed
to take close-ups, scan the horizon and produce stereo pairs for viewers on earth
Technician tests arm. It can whack at the lunar crust like a
pick and is strong enough to break a half-inch concrete slab or dig hole 20 inches
deep
Being realistic, Giberson expects there may be failures. "If only one of the
first four craft makes a successful soft landing, that will be a spectacular achievement,"
he says.
Surveyor is eight feet tall and its hinged, shock-absorbing legs spread out to
a diameter of 13 feet. It is designed to land softly on slopes of up to 15 degrees
and has actually landed safely, in rehearsals on earth, on 30-degree slopes.
The first thing Surveyor will do after landing is a little "housekeeping." It
will tilt its solar panel to the sun to begin acquiring more electric energy. Then
it will orient its high gain antenna toward earth for maximum radio strength.
These chores attended to, it will begin accepting and decoding radio commands
from earth: "Take a good look at yourself with the wide angle TV vidicon so we can
see if you received any landing damage. Now, look down at your legs so we can see
whether they are buried in dust."
One Job After Another
Meanwhile, on a different frequency, Surveyor will be transmitting a telemeter
report from its 24 touchdown sensors, on such things as time of contact of each
foot pad and the force with which each one struck, and whether any sliding or rolling
occurred after impact.
From the start, Surveyor has been an exciting challenge to its designers at Hughes
Aircraft. To develop a machine that can determine the nature and strength of the
lunar surface, provide information for maps, determine seismic activity and even
if the moon has a liquid core, analyze the chemical composition of the surface,
and do a score of other jobs-this is a tremendous task. Then add three complications:
The scientific payload cannot exceed 65 lbs., everything that Surveyor learns must
be relayed a quarter of a million miles to earth, and the moon craft must be able
to "live" in a 500-degree temperature range.
All this seems like an impossible assignment and yet, by combining pure science
and down-to-earth engineering, the Hughes' staff has reached solutions that appear
simple, once they are explained.
Built-in Temperature
How, for instance, can the electronics equipment be kept at between 0 and 125
degrees F. when the outside temperature climbs to 260 degrees F. during the day,
and then plummets to minus 240 degrees at night?
"Actually, battery energy will maintain a comfortable inside temperature at night,"
explains Sheldon C. Shallon, Hughes' chief scientist for Surveyor, "and thus the
real problem is daytime heat dissipation.
"So, for once, the electronics 'black boxes' are pure white, for maximum reflection
of the sun's heat. Inside the white skin there's a super-insulation of 75 layers
of aluminized Mylar, crinkled so that one sheet touches the next only here and there.
"If the inside temperature still climbs too high, bimetallic switch buttons will
click together and provide a metal heat channel to a glass window that has a mirrorlike
one-way coating. The window admits very little outside heat, yet can radiate a great
deal of interior heat."
Does the system work? The electronics white boxes have been "baked" under a solar
simulator (heat lamps) in a vacuum chamber. And they have been chilled with liquid
nitrogen until their temperature was that of the utter cold of the lunar night.
The system works perfectly.
Can Break Concrete
Again, how would you design a device to "determine the mechanical characteristics
of the lunar surface?"
On Surveyor the answer is simple and direct. The "soil sampler" is merely an
instrumented pantograph arm that has a reach of four feet, extended, and that swings
left or right on command. Spring-loaded, it can whack at the surface like a pick
(it's strong enough to break half an inch of concrete). It can dig a hole 20 inches
deep, can claw a furrow by retracting itself and meanwhile measure the drawbar pull.
These operations will be performed upon radio command from technicians stationed
in Jet Propulsion Lab's operations room in Pasadena, who will watch the results
on television. If small rocks happen to be in the way, the mechanical arm can push
them to one side and then attack the material below.
To analyze the composition of surface materials, a beam of alpha particles from
radioactive curium is used. The "scattering" of the alpha particles provides a rough
measurement of the elements that are present, such as calcium or iron. The device
can distinguish between meteoritic and igneous rocks.
A seismograph bolted to the spacecraft's frame not only will detect moon quakes,
if any, it will also determine if there is much expansion and contraction of the
surface because of temperature changes and will even pick up the impact of meteorites
hitting at a distance.
Cameras' "Eyeball" Moves
-One of the most sophisticated portions of the lunar lab is its television section
and, in particular, a pair of "survey" TV cameras. They can look almost all of the
way around the horizon and take stereo picture pairs of about a third of the adjacent
area. The cameras are actually stationary: they peer into pan-and-tile mirrors in
their hoods. It is the hood and mirror "eyeball" that moves, guided by tiny motors.
Obeying radio commands, the cameras will change from close-up wide angle to semitelescopic,
will change lens apertures from f/4 to f/22 and will even change filters to permit
construction of true color photos on earth. By stereo-ranging, distances to features
such as cliffs and craters will be measured so accurately that topographic maps
can be prepared.
Blood Will Boil
A century or so ago, "civilized" nations used to deport some of their worst criminals
to awesome parts of the earth where the heat, insects and disease soon killed them
off. Today, paradoxically, we are planning to dispatch three of the fittest, bravest
Americans to a hell far worse. On the moon the daytime temperature is above the
boiling point of blood. At night, without protection, you would freeze in a microsecond.
There is no air, no water.
To fire men out into space toward the moon, land them there and then bring them
safely back to earth, will be the most fantastic undertaking yet attempted by mankind.
Surveyor, the "mechanical American" will lead the way.
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