Multimedia Mania/abacus-multimedia-mania.iso/dp/0096/00968.txt

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$Unique_ID{bob00968}
$Pretitle{}
$Title{Apollo Expeditions To The Moon
Chapter 4: The Spaceships}
$Subtitle{}
$Author{Low, George M.}
$Affiliation{NASA}
$Subject{apollo
spacecraft
module
flight
lunar
oxygen
changes
lm
moon
system
see
pictures
see
figures
}
$Date{1975}
$Log{See Service Module*0096801.scf
See Wally Schirra*0096802.scf
See Reentry Test*0096803.scf
}
Title:       Apollo Expeditions To The Moon
Author:      Low, George M.
Affiliation: NASA
Date:        1975

Chapter 4: The Spaceships

     On April 3, 1967, NASA 2, a Grumman Gulfstream, was taxiing for takeoff
at Washington National Airport.  Bob Gilruth, Director of NASA's Manned Space-
craft Center and 1 (his Deputy at that time) were about to return to Houston
after a series of meetings in Washington.  But just before starting down the
runway, the pilot received a cryptic message from the tower: return to the
terminal and ask the passengers to wait in the pilot's lounge.  Soon arrived
Administrator Jim Webb, his Deputy Bob Seamans, George Mueller, the head of
Manned Space Flight, and Apollo Program Director Sam Phillips.  Counting Bob
Gilruth, everybody in the NASA hierarchy between me and the President was
there.

     Jim Webb, using fewer words than usual, came right to the point: Apollo
was faltering; the catastrophic fire on January 27 that had taken the lives of
three astronauts had been a major setback.  All its consequences were not yet
known; time was running out on the Nation's commitment to land on the Moon
before the end of the decade.  Then the punch line: NASA wanted me to take on
the task of rebuilding the Apollo spacecraft, and to see to it that we met the
commitment.

     Thus began the most exciting, most demanding, sometimes most frustrating,
and always most challenging 27 months in my career as an engineer.  Not that
Apollo was completely new to me.  Six years earlier I had chaired the NASA
committee that recommended a manned lunar landing and provided the background
work for President Kennedy's decision to go to the Moon.  In the intervening
years I had not been involved in the day-to-day engineering details of the
Apollo spaceships - met 27 months later, sitting at a console in the Launch
Control Center during the final seconds of the countdown for Apollo 11, I had
come to know and understand two of the most complex flying machines ever built
by man.

Two Magnificent Flying Machines

     But in April 1967 these machines were essentially strangers to me.  How
were they designed?  How were they built and tested?  What were their
strengths and their weaknesses?  Above all, what flaw in their design had
caused the fire, and what other flaws lurked in their complexity?

     First there was the command and service module - the CSM - collectively a
single spacecraft, but separable into two components (the command module and
the service module) for the final minutes of reentry.  It was built by North
American Rockwell in Downey, California, a place which would become one of my
many "homes" for the next 27 months.  The command module was compact, solid,
and sturdy, designed with one overriding consideration: to survive the fiery
heat of reentry as it abandoned the service module and slammed back into the
atmosphere at the tremendous speed of 25,000 miles an hour.  It was a
descendant of Mercury and Gemini, but its task was much more difficult.  The
speed of reentry from the Moon is nearly one and one-half times as fast as
returning from Earth orbit; to slow down from that speed required the
dissipation of great amounts of energy.  In fact, there is enough energy at
reentry to melt and vaporize all the material in the command module several
times over, so the spacecraft had to be protected by an ablative heat shield
that charred and slowly burned away, thereby protecting all that it
surrounded.  The command module was also crammed with equipment and
subsystems: and of course three men lived in it for most of the lunar journey,
and one of them for all of it.  It was cone-shaped, with a blunt face for
reentry; it was 11 feet long, 13 feet in diameter, and weighed 6 tons.

     The service module was the quartermaster of the pair.  It carried most of
the stores needed for the journey through space; oxygen, power-generation
equipment, and water as a byproduct of power generation.  More than that, it
had a propulsion system bigger and more powerful than many upper stages of
present launch vehicles.  It made all the maneuvers needed to navigate to the
Moon, to push itself and the lunar module into lunar orbit, and to eject
itself out of orbit to return to Earth.  The service module was a cylinder 13
feet in diameter and 24 feet long.  Fully loaded it weighed 26 tons.

     Then there was the lunar module (LM, pronounced LEM, which had actually
been its designation - for lunar excursion module until someone decided that
the word "excursion" might lend a frivolous note to Apollo).  LM was the first
true space-ship; it was hidden in a cocoon during the launch through the
atmosphere because it could operate only in the vacuum of space.  Built by
Grumman in Bethpage, New York (another of my many homes away from home), it
was somewhat flimsy, with paperthin walls and spindly legs.  Its mission was
to carry two explorers from lunar orbit to the surface of the Moon, provide a
base for them on the Moon, and then send its upper half back into lunar orbit
to a rendezvous with its mother ship, the CSM.  Designed by aeronautical
engineers who for once did not have to worry about airflow and streamlining,
it looked like a spider, a gargantuan, other-world insect that stood 23 feet
tall and weighed 16 tons.  When Jim McDivitt returned from Apollo 9, LM's
first manned flight, he gave me a photograph of his Spider in space, with this
caption: "Many thanks for the funny-looking spacecraft.  It sure flies better
than it looks."

     These were the Apollo spacecraft: two machines, 17 tons of aluminum,
steel, copper, titanium, and synthetic materials; 33 tons of propellant; 4
million parts, 40 miles of wire, 100,000 drawings, 26 subsystems, 678
switches, 410 circuit breakers.

     To look after them there was a brand-new program manager who would have
to leap upon this fast-moving train, learn all about it, decide what was good
enough and what wasn't, what to accept, and what to change.  In the meanwhile,
the clock ticked away, bringing the end of the decade ever closer.

Complex Subsystems Performed Vital Functions

     At the heart of each spacecraft were its subsystems. "Subsystem" is
space-age jargon for a mechanical or electronic device that performs a
specific function such as providing oxygen, electric power, and even bathroom
facilities.  CSM and LM subsystems performed similar functions, but differed
in their design because each had to be adapted to the peculiarities of the
spacecraft and its environment.

     Begin with the environmental control system - the life-support system for
man and his machine.  It was a marvel of efficiency and reliability, with
weight and volume at a premium.  A scuba diver uses a tank of air in 60
minutes; in Apollo an equivalent amount of oxygen lasted 15 hours.  Oxygen was
not simply inhaled once and then discarded: the exhaled gas was scrubbed to
eliminate its CO, recycled, and reused.  At the same time, its temperature was
maintained at a comfortable level, moisture was removed, and odors were
eliminated.  That's not all: the same life-support system also maintained the
cabin at the right pressure, provided hot and cold water, and a circulating
coolant to keep all the electronic gear at the proper temperature. (In the
weightless environment of space, there are no convective currents, and
equipment must be cooled by means of circulating fluids.) Because astronauts'
lives depended on this system, most of the functions were provided with
redundancy - and yet the entire unit was not much bigger than a window air
conditioner.

[See Service Module: Service module.]

     How do you generate enough electric power to run a ship in space?  In the
CSM, the answer was fuel cells: in the LM, storage batteries.  Apollo fuel
cells used oxygen and hydrogen stored as liquids at extremely cold
temperatures that when combined chemically yielded electric power and, as a
byproduct, water for drinking. (In early flights the water contained entrapped
bubbles of hydrogen, which caused the astronauts no real harm but engendered
major gastronomical discomfort.  This led to loud complaints, and the problem
was finally solved by installing special diaphragms in the system.) The
fuel-cell power system was efficient, clean, and absolutely pollution-free.
Storing oxygen and hydrogen required new advances in leakproof insulated
containers.  If an Apollo hydrogen tank were filled with ice and placed in a
room at 70 degrees_F, it would take 8.5 years for the ice to melt. If an
automobile tire leaked at the same rate as these tanks, it would take 30
million years to go flat.

     "Houston, this is Tranquility." These words soon would be heard from
another world, coming from an astronaut walking on the Moon, relayed to the
LM, then to a tracking station in Australia or Spain or California, and on to
Mission Control in Houston with only two seconds' delay.  Communications from
the Moon were clearer and certainly more reliable than they were from my home
in Nassau Bay (a stone's throw from the Manned Spacecraft Center to downtown
Houston.  At the same time, a tiny instrument would register a reading in the
astronauts' life-support system, and a few seconds later an engineer in
Mission Control would see a variation in oxygen pressure, or a doctor a change
in heart rate: and around the world people would watch on their home
television sets.  Behind all of this would be the Apollo communications system
designed to be the astronauts' life line back to Earth, to be compact and
lightweight, and yet to function with absolute reliability; an array of
receivers, transmitters, power supplies and antennas, all tuned to perfection,
that allowed the men and equipment on the ground to extend the capabilities of
the astronauts and their ships. (Later on, when the computer on Apollo 11's LM
was overloaded during the critical final seconds of the landing, it was this
communications system that enabled a highly skilled flight controller named
Steve Bales to tell Neil Armstrong that it was safe to disregard the overload
alarms and to go ahead with the lunar landing.)

     If you had to single out one subsystem as being most important, most
complex, and yet most demanding in performance and precision, it would be
Guidance and Navigation.  Its function: to guide Apollo across 250,000 miles
of empty space; achieve a precise orbit around the Moon; land on its surface
within a few yards of a predesignated spot; guide LM from the surface to a
rendezvous in lunar orbit; guide the CM to hit the Earth's atmosphere within a
27-mile "corridor" where the air was thick enough to capture the spacecraft,
and yet thin enough so as not to burn it up; and finally land it close to a
recovery ship in the middle of the Pacific Ocean.  Designed by the
Massachusetts Institute of Technology under Stark Draper's leadership, G&N
consisted of a miniature computer with an incredible amount of information in
its memory; an array of gyroscopes and accelerometers called the inertial-
measurement unit; and a space sextant to enable the navigator to take star
sightings.  Together they determined precisely the spacecraft location between
Earth and Moon, and how best to burn the engines to correct the ship's course
or to land at the right spot on the Moon with a minimum expenditure of fuel.
Precision was of utmost importance; there was no margin for error, and there
were no reserves for a missed approach to the Moon.  In Apollo 11, Eagle
landed at Tranquility Base, after burning its descent engine for 12 minutes,
with only 20 seconds of landing fuel remaining.

     But the guidance system only told us where the spacecraft was and how to
correct its course.  It provided the brain, while the propulsion system
provided the brawn in the form of rocket engines, propellant tanks, valves,
and plumbing.  There were 50 engines on the spacecraft, smaller but much more
numerous than those on the combined three stages of the Saturn that provided
the launch toward the Moon.  Most of them - 16 on the LM, 16 on the SM, and 12
on the CM - furnished only 100 pounds of thrust apiece; they oriented the
craft in any desired direction just as an aircraft's elevators, ailerons, and
rudder control pitch, roll, and yaw.

     Three of the engines were much larger.  On the service module a 20,500-
pound-thrust engine injected Apollo into lunar orbit, and later brought it
back home; on the LM there was a 10,500-pound-thrust engine for descent, and a
3500 pounder for ascent.  All three had to work: a failure would have stranded
astronauts on the Moon or in lunar orbit.  They were designed with reliability
as the number one consideration.  They used hypergolic propellants that burned
spontaneously on contact and required no spark plugs; the propellants were
pressure-fed into the thrust chamber by bottled helium, eliminating complex
pumps; and the rocket nozzles were coated with an ablative material for heat
protection, avoiding the need for intricate cooling systems.

     Three other engines could provide instant thrust at launch to get the
spacecraft away from the Saturn if it should inadvertently tumble or explode.
The largest of these produced 160,000 pounds of thrust, considerably more than
the Redstone booster which propelled Alan Shepard on America's first manned
spaceflight. (Since we never had an abort at launch, these three were never
used.)

     There were other subsystems, each with its own intricacies of design,
and, more often than not, with its share of problems.  There were displays and
controls, backup guidance systems, a lunar landing gear on the LM and an Earth
landing system (parachutes) on the CM, and a docking system designed with the
precision of a Swiss watch, yet strong enough to stop a freight car. There
were also those things that fell between the subsystems: wires, tubes,
plumbing, valves, switches, relays, circuit breakers, and explosive charges
that started, stopped, ejected, separated, or otherwise activated various
sequences.

A Tragic Fire Takes Three Lives

     Apollo in January 1967 was adjudged almost ready for its first manned
flight in Earth orbit.  And then disaster.  A routine test of Apollo on the
launching pad at Cape Kennedy.  Three astronauts - Grissom, White, and Chaffee
in their spacesuits in a 100-percent oxygen environment.  A tiny spark,
perhaps a short circuit in the wiring.  It was all over in a matter of
seconds.  Yet it would be 21 months before Apollo would again be ready to fly.

     By April 1967, when I was given the Apollo spacecraft job, an
investigation board had completed most of its work.  The board was not able to
pinpoint the exact cause of the fire, but this only made matters worse because
it meant that there were probably flaws in several areas of the spacecraft.
These included the cabin environment on the launch pad, the amount of
combustible material in the spacecraft, and perhaps most important, the
control (or lack of control) of changes.

     Apollo would fly in space with a pure oxygen atmosphere at 5 psi (pounds
per square inch), about one-third the pressure of the air we breathe.  But on
the launching pad, Apollo used pure oxygen at 16 psi, slightly above the
pressure of the outside air.  Now it happens that in oxygen at 5 psi things
will generally burn pretty much as they do in air at normal pressures.  But in
16 psi oxygen most nonmetallic materials will burn explosively; even steel can
be set on fire.  Mistake number one: Incredible as it may sound in hindsight,
we had all been blind to this problem.  In spite of all the care, all the
checks and balances, all the "what happens if's," we had overlooked the hazard
on the launching pad.

     Most nonmetallic things will burn even in air or 5 psi oxygen unless they
are specially formulated or treated.  Somehow, over the years of development
and test, too many nonmetals had crept into Apollo.  The cabin was full of
velcro cloth, a sort of space-age baling wire, to help astronauts store and
attach their gear and checklists.  There were paper books and checklists, a
special kind of plastic netting to provide more storage space, and the
spacesuits themselves, made of rubber and fabric and plastic.  Behind the
panels there were wires with nonmetallic insulation, and switches and circuit
breakers in plastic cases.  There were also gobs of insulating material called
RTV. (In Gordon Cooper's Mercury flight, some important electronic gear had
malfunctioned because moisture condensed on its uninsulated terminals.  The
solution for Apollo had been to coat all electronic connections with RTV,
which performed admirably as an insulator, but, as we found out later, burned
in an oxygen environment.) Mistake number two: Far too much nonmetallic
material had been incorporated in the construction of the spacecraft.

     There is an old saying that airplanes and spacecraft won't fly until the
paper equals their weight.  There was a time when two men named Orville and
Wilbur Wright could, unaided, design and build an entire airplane, and even
make its engine.  But those days are long gone.  When machinery gets as
complex as the Apollo spacecraft, no single person can keep all of its details
in his head.  Paper, therefore, becomes of paramount importance: paper to
record the exact configuration; paper to list every nut and bolt and tube and
wire; paper to record the precise size, shape, constitution, history, and
pedigree of every piece and every part.  The paper tells where it was made,
who made it, which batch of raw materials was used, how it was tested, and how
it performed.  Paper becomes particularly important when a change is made, and
changes must be made whenever design, engineering, and development proceed
simultaneously as they did in Apollo.  There are changes to make things work,
and changes to replace a component that failed in a test, and changes to ease
an astronaut's workload or to make it difficult to flip the wrong switch.

     Mistake number three: In the rush to prepare Apollo for flight, the
control of changes had not been as rigorous as it should have been, and the
investigation board was unable to determine the precise detailed configuration
of the spacecraft, how it was made, and what was in it at the time of the
accident.  Three mistakes, and perhaps more, added up to a spark, fuel for a
fire, and an environment to make the fire explosive in its nature. And three
fine men died.

[See Wally Schirra: Wally Schirra makes sure his crew cannot be trapped.]

And then the Rebuilding Began

     Now time was running out.  The race against time began, with only 33
months remaining from April 1967 and the end of the decade.  The work to be
done appeared to be overwhelming and dictated 18-hour days, seven days a week.
My briefcase was my office, my suitcase my home, as I moved from Houston to
Downey, to Bethpage, to Cape Kennedy, and back to Houston again.  At
Tranquility Base, the Sun would only rise 33 more times before 1970.

     Rebuilding meant changes and changes meant trouble if they were not kept
under perfect control.  Our solution was the CCB, the Configuration Control
Board.  On it were some of the best engineers in the world: my two deputies,
Ken Kleinknecht and Rip Bolender; Apollo's Assistant for Flight Safety, Scott
Simpkinson; Max Faget, Houston's Chief Engineer; Chris Kraft, the Chief of
Flight Operations; Deke Slayton, the head of the astronauts; Dale Myers for
North American Rockwell; and Joe Gavin for Grumman.  The Board was rounded out
with Chuck Berry for medical inputs and Bill Hess for science.  It was
organized by my technical assistant, George Abbey, who knew everything about
everybody on Apollo, and who was always able to get things done.  I was its
chairman and made all decisions.  Arguments sometimes got pretty hot as
technical alternatives were explored.  In the end I would decide, usually on
the spot, always explaining my decision openly and in front of those who liked
it the least.  To me, this was the true test of a decision to look straight
into the eyes of the person most affected by it, knowing full well that months
later on the morning of a flight, I would look into the eyes of the men whose
lives would depend on that decision.  One could not make any mistakes.

     When I wasn't sure of myself or when I didn't trust my judgment, I knew
where to go to get help -- Bob Gilruth, my boss, who himself had been through
every problem in Mercury.  An extremely able engineer, Bob had acquired great
wisdom over the years dealing with men and their flying machines.  Bob was
always there when I needed him.

     The CCB met every Friday, promptly at noon, and often well into the
night.  From June 1967 to July 1969 the Board met 90 times, considered 1697
changes and approved 1341.  We dealt with changes large and small, discussed
them in every technical detail, and reviewed their cost and schedule impact.
Was the change really necessary?  What were its effects on other parts of the
machine, on computer programs, on the astronauts, and on the ground tracking
systems?  Was it worth the cost, how long would it take, and how much would it
weigh?

     We redesigned the command module hatch to open out instead of in, because
the old hatch had been a factor in trapping Grissom, White, and Chaffee inside
their burning craft.  This may sound simple, but it wasn't.  An inward-opening
hatch was much easier to build, because when it was closed it tended to be
self-sealing since the pressure inside the spacecraft forced it shut.  The
opposite was true for an outward-opening hatch, which had to be much sturdier,
and hence heavier, with complicated latches.

     We rewired the spacecraft, rerouted wire bundles, and used better
insulation on the wires.  We looked at every ounce of nonmetallic material,
removed much of it, and concocted new materials for insulation and for
pressure suits.  We invented an insulating coating that would not burn, only
to find that it would absorb moisture and become a conductor, so we had to
invent another one.  Pressure suits had to shed their nylon outer layer, to be
replaced with a glass cloth; but the glass would wear away quickly, and shed
fine particles which contaminated the spacecraft and caused the astronauts to
itch.  The solution was a coating for the glass cloth.  We solved the problem
of fire in the space atmosphere of 5 psi oxygen; but try as we might, we could
not make the ship fireproof in the launch-pad atmosphere of 16 psi oxygen.
Then Max Faget came up with an idea: Launch with an atmosphere that was 60
percent oxygen and 40 percent nitrogen, and then slowly convert to pure oxygen
after orbit had been reached and the pressure was 5 psi.  The 60-40 mixture
was a delicate balance between medical requirements on the one hand (too much
nitrogen would have caused the bends as the pressure decreased) and
flammability problems on the other.  It worked.

     Weight is a problem in the design of any flying machine.  Apollo, with
its many changes, was anything but an exception.  Problems are always easier
to solve if one can afford a little leeway for making a change, but difficult
and expensive if there is no weight margin.  In the command module, we found a
way to gain an extra 1000 pound margin by redesigning the parachute to handle
a heavier GM.  This margin made other CM changes relatively simple, and
certainly less costly and time consuming.

     For LM there was no such solution.  We had to shave an ounce here,
another there, to make room for the changes that had to be made.  It was
difficult, lengthy, and expensive.

Testing and Retesting to Get Ready for Flight

     We tested for "sneak circuits" (inadvertent electrical paths), discovered
some, and made changes.  We ran a "failure mode and effects analysis" a search
for all the "what happens if's" and made more changes.  We tested, and
retested, and changed and fixed and tested again.  We set off small explosive
charges inside the burning rocket engines, and to our horror found the
all-important LM ascent engine was prone to catastrophic instability - a way
of burning that could destroy the engine on takeoff and leave the astronauts
stranded on the Moon.  Much to the consternation of my bosses in Washington,
we sent out new bids and selected a different contractor who built a new
engine faster than anyone believed possible.  But it worked.

     No detail was too small to consider.  We asked questions, received
answers, asked more questions.  We woke up in the middle of the night,
remembering questions we should have asked, and jotted them down so we could
ask them in the morning.  If we made a mistake, it was not because of any lack
of candor between NASA and contractor, or between engineer and astronaut; it
was only because we weren't smart enough to ask all the right questions. Every
question was answered, every failure understood, every problem solved.

     We built mockups of the entire spacecraft, and tried to set them on fire.
If they burned, we redesigned, rebuilt, and tried again.  By vibration we
tried to shake things apart; we tested in chambers simulating the vacuum of
space, the heat of the Sun, and the cold of the lunar night.  We subjected all
systems to humidity and salt spray, to the noise of the booster, and the shock
of a hard landing.  We dropped the command module into water to simulate
normal landings and on land to test for emergency landings; we plopped the
lunar module on simulated lunar terrain.  We over-stressed and overloaded
until things broke, and if they broke too soon, we redesigned and rebuilt and
tested again.

     The final exam came in flight.  First the command module was tested with
only the launch-escape tower, against the possibility of a Saturn exploding on
the launch pad.  Then we launched the GSM on a special booster, the Little Joe
II, to see whether it would survive if the Saturn should fail in the
atmosphere, when air loads are at their peak. (There is a big difference
between manned and unmanned flight.  If the launch vehicle should stray off
course while lifting an automated payload, the range safety officer could
press a button and destroy booster and payload together; in manned flight the
spacecraft would first be separated from the errant booster, which would then
be blown up before it wandered off, leaving the GM to be carried to safety by
the launch escape tower.  This separation maneuver demanded the utmost in
speed and power.)

     The CSM, unmanned, was flown twice on the Saturn 1B (1,600,000 pounds of
thrust).  Then, on November 9, 1967, came the most critical test of all:
Apollo 4, the first flight of the Saturn V (7,500,000 pounds), would subject
the CSM to the lunar return speed of 25,000 mph.  After achieving an altitude
of 10,000 miles, the spacecraft's engines drove Apollo back down into the
atmosphere at unprecedented speed.  Temperatures on the heat shield reached
50000 F, more than half the surface temperature of the Sun.  The heat shield
charred as expected, but the inside of the cabin remained at a comfortable 700
F.  A major milestone had been passed.

[See Reentry Test: Charred but perfectly intact, the CM here had passed its
most severe test of reentry at a speed of 25,000 mph.]

    Apollo 5 on January 22, 1968, was the first flight test of LM - an
unmanned flight in Earth orbit that put the lunar module through its paces.
There were problems.  The computer shut down the LM's descent engine
prematurely on its first burn.  But then the flight controllers on the ground
took over and continued the flight with an alternate mission.  Now another
question arose: Should we repeat this flight?  Grumman felt we should; 1
disagreed.  After considerable technical debate, we decided that the next
flight with LM would be manned which it was, 14 months later.

     Apollo 6, three months after Apollo 5, was to be a simple repeat of
Apollo 4, but it wasn't.  The Saturn had problems, and so did the spacecraft
adapter - that long conical section which joined the CSM to the booster, and
which also served as LM's cocoon. (The spacecraft itself did a beautiful job.)
After a fantastic piece of detective work by Don Arabian, our chief test
engineer, we found a flaw in the manufacturing of the honeycomb structure of
the adapter, and how to fix it.

     October 11, 1968.  Eighteen months since that day in the pilot's lounge
at Washington Airport when 1 said yes, 1 would take on Apollo. Eighteen of the
greatest months an engineer could ask for.  In that time 150,000 Americans had
worked around the clock, dedicating their skills and their lives to forge two
of the most magnificent flying machines yet devised: CSM and LM.  It was a
beautiful morning in Florida, just the kind of morning for another launch.
This time Apollo was ready for its men.