Multimedia Mania/abacus-multimedia-mania.iso/dp/0096/00967.txt

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$Unique_ID{bob00967}
$Pretitle{}
$Title{Apollo Expeditions To The Moon
Chapter 3: Saturn The Giant}
$Subtitle{}
$Author{Von Braun, Wernher}
$Affiliation{NASA}
$Subject{saturn
engines
first
stage
rocket
flight
launch
new
orbit
stages
see
pictures
see
figures
}
$Date{1975}
$Log{See Saturn V Engines*0096701.scf
See Command Module*0096702.scf
}
Title:       Apollo Expeditions To The Moon
Author:      Von Braun, Wernher
Affiliation: NASA
Date:        1975

Chapter 3: Saturn The Giant

     With the launch of Sputnik on October 4, 1957, the Soviet Union had
inaugurated the Space Age.  It had also presented American planners with the
painful realization that there was no launch vehicle in the U.S. stable
capable of orbiting anything approaching Sputnik's weight.

     Responding to a proposal submitted by the Army Ballistic Missile Agency,
the Department of Defense was in just the right mood to authorize ABMA to
develop a 1,500,000-pound-thrust booster.  That unprecedented thrust was to be
generated by clustering eight S-3D Rocketdyne engines used in the Jupiter and
Thor missiles.  The tankage for the kerosene and liquid oxygen was also to be
clustered to make best use of tools and fixtures available from the Redstone
and Jupiter programs.  The program was named "Saturn" simply because Saturn
was the next outer planet after Jupiter in the solar system.

     Gen. John B. Medaris, commander of ABMA and my boss, felt that for a good
design job on the booster it was necessary for us also to study suitable upper
stages for the Saturn.  On November 18, 1959, Saturn was transferred to the
new National Aeronautics and Space Administration.  NASA promptly appointed a
committee to settle the upper-stage selection for Saturn.  It was chaired by
Dr. Abe Silverstein who, as associate director of NASA's Lewis Center in
Cleveland, had spent years exploring liquid hydrogen as a rocket fuel.  As a
result of this work the Air Force had let a contract with Pratt & Whitney for
the development of a small 15,000-pound-thrust liquid hydrogen/ liquid oxygen
engine, two of which were to power a new "Centaur" top stage for the Air
Force's Atlas.  Abe was on solid ground when he succeeded in persuading his
committee to swallow its scruples about the risks of the new fuel and go to
high-power liquid hydrogen for the upper stage of Saturn.

     In the wake of Gagarin's first orbital flight on April 12, 1961, Saturn
gained increased importance.  Nevertheless, when the first static test of the
booster with all eight engines was about to begin, at least one skeptical
witness predicted a tragic ending of "Cluster's last stand." Doubts about the
feasibility of clustering eight highly complex engines had indeed motivated
funding for two new engine developments.  One was in essence an uprating and
simplification effort on the S-3D, and it led to the 188,000-pound-thrust H- 1
engine.  The other aimed at a very powerful new engine called F-1, which was
to produce a full 1.5-million-pound thrust in a single barrel.  Both contracts
went to Rocketdyne.

     Following up on the recommendation of the Silverstein committee, NASA
awarded a contract to the Douglas Aircraft Company for the development of a
second stage for Saturn that became known as S-IV.  It was to be powered by
six Centaur engines.  On September 8, 1960, President Eisenhower came to
Huntsville to dedicate the new Center, named after Gen. George C. Marshall. It
was to become the focal point for NASA's new large launch vehicles, and 1 was
appointed as its first director.

Determining Saturn's Configuration

     The first launch of the Saturn booster was still five months away when,
on May 25, 1961, President John F. Kennedy proposed that the United States
commit itself to land a man on the Moon "in this decade." For this ambitious
task a launch vehicle far more powerful than our eight-engine Saturn would be
needed.  To determine its exact power requirements, a selection had to be made
from among three operational concepts for a manned voyage to the Moon: direct
ascent, Earth orbit rendezvous (EOR), and lunar orbit rendezvous (LOR).

     With direct ascent, the entire spacecraft would soft-land on the Moon
carrying enough propellants to fly back to Earth.  Weight and performance
studies showed that this would require a launch vehicle of a lift-off thrust
of 12 million pounds, furnished by eight Fl engines.  We called this
hypothetical launch vehicle Nova.  The EOR mode envisioned two somewhat
smaller rockets that were to rendezvous in Earth orbit where their payloads
would be combined.  In the LOR mode a single rocket would launch a payload
consisting of a separable spacecraft toward the Moon, where an onboard
propulsion unit would ease it into orbit.  A two-stage lunar module (LM) would
then detach itself from the orbiting section and descend to the lunar surface.
Its upper stage would return to the circumlunar orbit for rendezvous with the
orbiting section.  In a second burst of power, the propulsion unit would
finally drive the reentry element with its crew out of lunar orbit and back to
Earth.

     As all the world knows, the LOR mode was ultimately selected.  But even
after its adoption, the number of F- 1 engines to be used in the first stage
of the Moon rocket remained unresolved for quite a while.  H. H. Koelle, who
ran our Project Planning Group at Marshall, had worked out detailed studies of
a configuration called Saturn IV with four F-1's, and another called Saturn V
with five F-1's in its first stage.  Uncertainty about LM weight and about
propulsion performance of the still untested F-1 and upper-stage engines,
combined with a desire to leave a margin for growth, finally led us to the
choice of the Saturn V configuration.

[See Saturn V Engines: Dr. von Braun standing next to one of the five engines
at the after end of the Saturn V.]

     Despite the higher power offered by liquid hydrogen, Koelle's studies
indicated that little would be gained by using it in the first stage also,
where it would have needed disproportionately large tanks. (Liquid hydrogen is
only one twelfth as dense as kerosene, so a much larger tank volume would have
been required.) In all multistage rockets the upper stages are lighter than
the lower ones.  Thus heavier but less energetic kerosene in the first stage,
in combination with lighter but more powerful hydrogen in the upper stages,
made possible a better launch-vehicle configuration.

     Saturn V, as it emerged from the studies, would consist of three stages -
all brand new.  The first one, burning kerosene and oxygen, would be powered
by five Fl engines.  We called it S-1C.  The second stage, S-II, would need
about a million pounds of thrust and, if also powered by five engines, would
call for the development of new 200,000-pound hydrogen-oxygen engines.  A
single engine of this thrust would just be right to power the third stage. The
Saturn 1's 5-IV second stage was clearly not powerful enough to serve as the
Saturn's third one.  A much larger tankage and at least thirteen of Pratt &
Whitney's little LR-10 engines would be required; this did not appear very
attractive.

     When bids for the new J-2 engine were solicited, Pratt & Whitney with its
ample liquid-hydrogen experience was a strong contender.  But when all the
points in the sternly controlled bidding procedure were counted, North
American's Rocketdyne Division won again.

     North American had been involved in the development of liquid fuel rocket
engines since the immediate postwar years and the Navajo long range ramjet
program.  The engines it developed for the Navajo booster and their offspring
later found their way into the Atlas, Redstone, Thor, and Jupiter programs.
For the testing of these engines NAA's Rocketdyne Division had acquired a
boulder-strewn area high in the Santa Susana mountains, north of Los Angeles,
that had previously served as rugged background for many a Western movie.  The
Santa Susana facility would henceforth serve not only for the development of
the new J-2 engine, but also for short duration "battleship" testing of the
five-engine cluster of these engines powering the S-II stage. (Safety and
noise considerations ruled out the use of Santa Susana for the
1.5-million-pound-thrust F-1 engine.  Test stands for its development were
therefore set up in the Mojave desert, adjacent to Edwards Air Force Base.)

Choosing the Builders

     How many prime contractors, we wondered, should NASA bring in for the
development of the Saturn V? Just one, or one per stage?  How about the
Instrument Unit that was to house the rocket's inertial-guidance system, its
digital computer, and an assortment of radio command and telemetry functions?
Who would do the overall systems engineering and monitor the intricate
interface between the huge rocket and the complex propellant-loading and
launching facilities at Cape Canaveral?  Where would the various stages be
static-tested?

     Understandably, the entire aerospace industry was attracted by both the
financial value and the technological challenge of Saturn V.  To give the
entire plum to a single contractor would have left all others unhappy.  More
important, Saturn V needed the very best engineering and management talent the
industry could muster.  By breaking up the parcel into several pieces, more
top people could be brought to bear on the program.

     The Boeing Company was the successful bidder on the first stage (S-1C);
North American Aviation won the second stage (5-11); and Douglas Aircraft fell
heir to the Saturn V's third stage (S-1VB).  Systems engineering and overall
responsibility for the Saturn V development was assigned to the Marshall Space
Flight Center.  The inertial-guidance system had emerged from a Marshall
in-house development, and as it had to be located close to other elements of
the big rocket's central nervous system, it was only logical to develop the
Instrument Unit (IU) to house this electronic gear as a Marshall in-house
project.  IU flight units were subsequently produced by IBM, which had
developed the launch-vehicle computer.

     Uniquely tight procurement procedures introduced by NASA Administrator
Jim Webb made it possible to acquire billions of dollars' worth of exotic
hardware and facilities without overrunning initial cost estimates and without
the slightest hint of procurement irregularity.  Before it could issue a
request for bids, the contracting NASA Center had to prepare a detailed
procurement plan that required the Administrator's personal approval, and that
could not be changed thereafter.  It had to include a point-scoring system in
which evaluation criteria technical merits, cost, skill availability, prior
experience, etc.-were given specific weighting factors. Business and technical
criteria were evaluated by separate teams not permitted to know the other's
rankings.  The total matrix was then assembled by a Source Evaluation Board
that gave a complete presentation of all bids and their scoring results to the
three top men in the agency, who themselves chose the winner.  There was
simply no room for arbitrariness or irregularity in such a system.

     The tremendous increase in contracts needed for the Saturn V program
required a reorganization of the Marshall Space Flight Center.  Most of our
resources had been spent in-house, and our contracts had either been let to
support contractors or to producers of our developed products.  Now 90 percent
of our budget was spent in industry, much of it on complicated assignments
which included design, manufacture, and testing.  So on September 1, 1963, I
announced that Marshall would henceforth consist of two major elements, one to
be called Research and Development Operations, the other Industrial
Operations.  Most of my old R&D associates then became a sort of architect's
staff keeping an eye on the integrity of the structure called Saturn V, and
the other group funded and supervised the industrial contractors.

     That same year Dr. George Mueller had taken over as NASA's Associate
Administrator for Manned Space Flight.  He brought with him Air Force Maj.
Gen. Samuel Phillips, who had served as program manager for Minuteman, and now
became Apollo Program Director at NASA Headquarters.  Both men successfully
shaped the three NASA Centers involved in the lunar-landing program into a
team.  I was particularly fortunate in that Sam Phillips persuaded his old
friend and associate Col. (later Maj. Gen.) Edwin O'Connor to assume the
directorship of Marshall's Industrial Operations.

     On September 7, 1961, NASA had taken over the Michoud Ordnance plant at
New Orleans.  The cavernous plant - 46 acres under one roof - was assigned to
Chrysler and Boeing to set up production for the first stages of Saturn I and
Saturn V.  In October 1961 an area of 13,350 acres in Hancock County, Miss.,
was acquired.  Huge test stands were erected there for the static testing of
Saturn V's first and second stages.

     Shipment of the oversize stages between Huntsville, Michoud, the
Mississippi Test Facility, the two California contractors, and the Kennedy
Space Center in Florida required barges and seagoing ships.  Soon Marshall
found itself running a small fleet that included the barges Palaemon, Orion,
and Promise.  For shipments through the Panama Canal we used the USNS Point
Barrow and the SS Steel Executive.  For rapid transport we had two converted
Stratocruisers at our disposal with the descriptive names "Pregnant Guppy" and
"Super Guppy." Their bulbous bodies could accommodate cargo up to the size of
an S-IVB stage.

An All-up Test for the First Flight

     In 1964 George Mueller visited Marshall and casually introduced us to his
philosophy of "all-up" testing.  To the conservative breed of old rocketeers
who had learned the hard way that it never seemed to pay to introduce more
than one major change between flight tests, George's ideas had an unrealistic
ring.  Instead of beginning with a ballasted first-stage flight as in the
Saturn 1 program, adding a live second stage only after the first stage had
proven its flight-worthiness, his "all-up" concept was startling. It meant
nothing less than that the very first flight would be conducted with all three
live stages of the giant Saturn V.  Moreover, in order to maximize the payoff
of that first flight, George said it should carry a live Apollo command and
service module as payload.  The entire flight should be carried through a
sophisticated trajectory that would permit the command module to reenter the
atmosphere under conditions simulating a return from the Moon.

     It sounded reckless, but George Mueller's reasoning was impeccable. Water
ballast in lieu of a second and third stage would require much less tank
volume than liquid-hydrogen-fueled stages, so that a rocket tested with only a
live first stage would be much shorter than the final configuration. Its
aerodynamic shape and its body dynamics would thus not be representative.
Filling the ballast tanks with liquid hydrogen?  Fine, but then why not burn
it as a bonus experiment?  And so the arguments went on until George in the
end prevailed.

     In retrospect it is clear that without all-up testing the first manned
lunar landing could not have taken place as early as 1969.  Before Mueller
joined the program, it had been decided that a total of about 20 sets of
Apollo spacecraft and Saturn V rockets would be needed.  Clearly, at least ten
unmanned flights with the huge new rocket would be required before anyone
would muster the courage to launch a crew with it. (Even ten would be a far
smaller number than the unmanned launches of Redstones, Atlases, and Titans
that had preceded the first manned Mercury and Gemini flights.) The first
manned Apollo flights would be limited to low Earth orbits.  Gradually we
would inch our way closer to the Moon, and flight no. 17, perhaps, would bring
the first lunar landing.  That would give us a reserve of three flights, just
in case things did not work as planned.

     Mueller changed all this, and his bold telescoping of the overall plan
bore magnificent fruit: With the third Saturn V ever to be launched, Frank
Borman's Apollo 8 crew orbited the Moon on Christmas 1968, and the sixth
Saturn V carried Neil Armstrong's Apollo 11 to the first lunar landing.  Even
though production was whittled back to fifteen units, Saturn V's launched a
total of two unmanned and ten manned Apollo missions, plus one Skylab space
station.  Two uncommitted rockets went into mothballs.

     But let us go back to 1962.  To develop and manufacture the large S-II
and S-IVB stages, two West Coast contractors required special facilities.  A
new Government plant was built at Seal Beach where North American was to build
the S-II.  S-1VB development and manufacture was moved into a new Douglas
center at Huntington Beach, while static testing went to Sacramento. The
Marshall Center in Huntsville was also substantially enlarged.  A huge new
shop building was erected for assembly of the first three S-1C stages.  A
large stand was built to static-test the huge stage under the full 7,500,000-
pound-thrust of its five F-1 engines.  These engines generated no less than
180 million horsepower.  As about I percent of that energy was converted into
noise, neighborhood windows could be expected to break and plaster rain from
ceilings if the wind was blowing from the wrong direction or the clouds were
hanging low.  A careful meteorological monitoring program had to be instituted
to permit test runs only under favorable weather conditions.

     Although the most visible and audible signs of Marshall's involvement in
Saturn V development were the monstrous and noisy S-1C engines, equally
important work was done in its Astrionics Laboratory.  The Saturn V's
airbearing-supported inertial guidance platform was born there, along with a
host of other highly sophisticated electronic devices.  In the Astrionics
Simulator Facility, guidance and control aspects of a complete three-stage
flight of the great rocket could be electronically simulated under all sorts
of operating conditions.  The supersonic passage of the rocket through a high-
altitude jet stream could be duplicated, for instance, or the sudden failure
of one of the S-II stage's five engines.  The simulator would faithfully
display the excursions of the swivel-mounted rocket engines in response to
external wind forces or unsymmetrical loss of thrust, establishing the dynamic
response of the entire rocket and the resulting structural loads.

     The Saturn V's own guidance system would guide the Apollo flights not
only to an interim parking orbit but all the way to trans-lunar injection. It
fed position data to the onboard digital computer, which in turn prepared and
sent control signals to the hydraulic actuators that swiveled the big engines
for flight-path control.  As propellant consumption lightened the rocket, and
as it traversed the atmosphere at subsonic and supersonic speeds, the gain
settings of these control signals had to vary continuously, for proper control
damping.  Serving as the core of the Saturn V's central nervous system, the
computer did many other things too.  It served in the computerized pre-launch
checkout procedure of the great rocket, helped calibrate the telemetry
transmissions, activated staging procedures, turned equipment on and off as
the flight proceeded through various speed regimes, and even watched over the
cooling system that stabilized the temperatures of the array of sensitive
blackboxes within the IU.  So although the working flight lifetime of the
Saturn computer was measured in minutes, it performed many exacting duties
during its short and busy life.

     In planning the lunar mission, why did we plan to stop over in a parking
orbit?  The reason was twofold: For one, in case of a malfunction it is much
easier and safer for astronauts to return from Earth orbit than from a high-
speed trajectory carrying them toward the Moon.  A parking orbit offers both
crew and ground controllers an opportunity to give the vehicle a thorough
once-over before committing it to the long voyage.  Second, there is the
consideration of operational flexibility.  If the launch came off at precisely
the right instant, only one trajectory from the launch pad to the Moon had to
be considered.  But as there was always the possibility of a last-minute delay
it appeared highly desirable to provide a launch window of reasonable
duration.  This meant not only that the launch azimuth had to be changed, but
due to Earth rotation and to orbital motion the Moon would move to a different
position in the sky.  A parking orbit permitted an ideal way to take up the
slack: the longer a launch delay, the shorter the stay in the parking orbit.
Restart of the third stage in parking orbit for translunar injection would
take place at almost the same time of day regardless of launch delays. (As it
happened, all but two of the manned Apollo-Saturns lifted off within tiny
fractions of a second of being precisely on time.  One was held for weather
and the other was held because of a faulty diode in the ground-support
equipment.)

     Why was the big rocket so reliable?  Saturn V was not over-designed in
the sense that everything was made needlessly strong and heavy.  But great
care was devoted to identifying the real environment in which each part was to
work - and "environment" included accelerations, vibrations, stresses, fatigue
loads, pressures, temperatures, humidity, corrosion, and test cycles prior to
launch.  Test programs were then conducted against somewhat more severe
conditions than were expected.  A methodology was created to assess each part
with a demonstrated reliability figure, such as 0.9999998.  Total rocket
reliability would then be the product of all these parts reliabilities, and
had to remain above the figure of 0.990, or 99 percent. Redundant parts were
used whenever necessary to attain this reliability goal.

     Marshall built an overall systems simulator on which all major subsystems
of the three-stage rocket could be exercised together.  This facility featured
replicas of propellant tanks that could be loaded or unloaded, pressurized or
vented, and that duplicated the pneumatic and hydraulic dynamics involved.
Electrically, it simulated the complete network of the launch vehicle and its
interfacing ground support equipment.

The Perils of Pogo

     An important Marshall facility was the Dynamic Test Tower, the only place
outside the Cape where the entire Saturn V vehicle could be assembled.
Electrically powered shakers induced various vibrational modes in the vehicle,
so that its elastic structural damping characteristics could be determined.
The Dynamic Test Tower played a vital role in the speedy remedy of a problem
that unexpectedly struck in the second flight of a Saturn V. Telemetry
indicated that during the powered phases of all three stages a longitudinal
vibration occurred, under which the rocket alternately contracted and expanded
like a concertina.  This "pogo" oscillation (the name derived from the child's
toy) would be felt particularly strongly in the command module.

     Analysis, supported by data collected in engine tests, confirmed that the
oscillation was caused by resonance coupling between the spring-like elastic
structure of the tankage, and the rocket engines' propellant-feed systems.
Susceptibility to pogo (a phenomenon not unknown to missile designers) had
been thoroughly investigated by the Saturn stage contractors, who had
certified that their respective designs would be pogo-free.  It turned out
that these mathematical analyses had been conducted on an inadequate data
base.

     Once the problem was understood, a fix was quickly found.  "In sync" with
the pogo oscillations, pressures in the fuel and oxidizer feed lines
fluctuated wildly.  If these fluctuations could be damped by gas-filled
cavities attached to the propellant lines, which would act as shock absorbers,
the unacceptable oscillation excursions should be drastically reduced.  Such
cavities were readily available in the liquid-oxygen pre-valves, whose back
sides were now filled with pressurized helium gas tapped off the high-pressure
control system.  After a few weeks of hectic activity, a pogo-free Saturn
flight no. 3 successfully boosted the Apollo 8 crew to their Christmas flight
in lunar orbit.

Artificial Storms at the Arm Farm

     The connections between the ground and the towering space vehicle posed a
tricky problem.  An umbilical tower, even higher than the vehicle itself, was
required to support an array of swing-arms that at various levels would carry
the cables and the pneumatic, fueling, and venting lines to the rocket stages
and to the spacecraft.  The swing-arms had to be in place during final
countdown, but in the last moments they had to be turned out of the way to
permit the rocket to rise.  There was always the possibility, however, of some
trouble after the swing-arms had been disconnected.  For instance, the hold-
down mechanism would release the rocket only after all five engines of the
first stage produced full power.  If this condition was not attained within a
few seconds, all engines would shut down.  In such a situation, unless special
provisions were made for reattachment of some swing-arms, Launch Control would
be unable to "safe" the vehicle and remove the flight crew from its precarious
perch atop a potential bomb.

     These considerations led to the establishment, at Marshall, of a special
Swing-arm Test Facility, where detachment and reconnection of various arms was
tested under brutally realistic conditions.  On the "Arm Farm" extreme
conditions (such as a launch scrub during an approaching Florida thunderstorm)
could be simulated.  Artificial rain was blown by aircraft propellers against
the swing-arms and their interconnect plugs, while the vehicle portion was
moved back and forth, left and right, simulating the swaying motions that the
towering rocket would display during a storm.

     Throughout Saturn V's operational life, its developers felt a relentless
pressure to increase its payload capability.  At first, the continually
growing weight of the LM (resulting mainly from additional operational
features and redundancy) was the prime reason.  Later, after the first
successful lunar landing, the appetite for longer lunar stay times grew.
Scientists wanted landing sites at higher lunar latitudes, and astronauts like
tourists everywhere wanted a rental car at their destination.  How well this
growth demand was met is shown by a pair of numbers: The Saturn V that carried
Apollo 8 to the Moon had a total payload above the IV of less than 80,000
pounds; in comparison, the Saturn that launched the last lunar mission, Apollo
17, had a payload of 116,000 pounds.

[See Command Module: Command module circling the Moon.]