Post on 24-May-2022
THE HISTORY OF SPACEFLIGHTQ U A R T E R L Y
spacehistory101.com2018 - Vol. 25 - No. 3
A HISTORY OF SOVIET/RUSSIAN MISSILE EARLY WARNING
SATELLITES - PART II
DEVICES TO CONTROL UNMANNED APOLLO FLIGHTS
AN INTERVIEW WITH HAROLD B. FINGER:
NUCLEAR INVESTIGATIONS
REAL SPACE MODELING
GEORGE ABBEY:THE ASTRONAUT MAKER
BOOK REVIEWS
71 Chasing New Horizons: Inside the Epic First Mission to Pluto Book by Alan Stern and David Grinspoon
Review by Michael J. Neufeld
72 Space Science and the Arab World: Astronauts, Observatories and Nationalism in the Middle East Edited by Jӧrg Matthias Determann
Review by Christopher Gainor
FEATURES
3 A History of Soviet/Russian Missile Early Warning Satellites—Part II By Bart Hendrickx
27 Devices to Control Unmanned Apollo Flights By Edgar Durbin
ORAL HISTORY
39 An Interview with Harold B. Finger: Nuclear Investigations Interview by Kevin M. Rusnak
BIOGRAPHY / BOOK REVIEW
58 George Abbey:
The Astronaut Maker—How One Mysterious Engineer Ran Human Spaceflight for a Generation
Book by Michael Cassutt Profile and review by Glen E. Swanson
ARCHIVES & MUSEUMS
66 Real Space Modeling By Keith J. Scala
ContentsVolume 25 • Number 3 2018
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An image from a September 1964 Aerojet reportshowing the locations of test instruments overlaid ontop of a graph showing the fast neutron and gammaray radiation flux around the NERVA nuclear rocketengine at power.
Please note that two words (GAGE and etimated) aremisspelled in the original image. Credit: Aerojet
FRONT COVER CAPTION
Images Courtesy: Heritage Auctions
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By Edgar Durbin
Introduction Several Apollo missions were
flown without crews to test space-
craft hardware and software to avoid
risk to astronauts. These missions
tested equipment and rehearsed
maneuvers that would be performed
under astronaut control during oper-
ational flights. To replace the astro-
nauts for these tests, NASA devel-
oped three devices.
The first was needed for mis-
sion AS-201, the only Apollo space-
craft launched on a Saturn rocket
that did not carry a Primary
Guidance, Navigation, and Control
System (PGNCS).
The second was used on mis-
sions AS-202 and Apollos 4 and 6.
These four missions tested
Command Module (CM) reentry.
The third device controlled the
Lunar Module (LM) during Apollos5, 9, and 10. Many components
were developed for the Apollo pro-
gram, including the spacecraft,
launch vehicle, mission control,
tracking network, and other ele-
ments. Table 1 lists Apollo launches
using Saturn IB and Saturn V rock-
ets. Shaded area denotes missions
carrying the control devices dis-
cussed in this article.
F E A T U R E
DEVICES TO CONTROL UNMANNED APOLLO FLIGHTS
Table 1. Saturn IB and V launches in the Apollo program. The launch vehicles for the missions discussed inthis article are shown in Figure 1.
MISSION LAUNCH VEHICLE RESULTAS-201 26-Feb-66 Saturn IB - CSM Sub-orbital unmanned CM reentry, SM engine test
AS-202 25-Aug-66 Saturn IB - CSMSub-orbital unmanned CM reentry, SM engine test withPrimary Guidance and Navigation System (PGNCS)
AS-203 5-Jul-66 Saturn IB Earth orbit of S-IVB stage, S-IVB restart
Apollo 1 27-Jan-67 Saturn IB - CSM Fire in CM on launch pad, killed crew
Apollo 4 9-Nov-67 Saturn V - CSM - LTAFirst Saturn V flight, unmanned CSM Earth orbit, test ofS-IVB restart, CM reentry
Apollo 5 22-Jan-68 Saturn IB - LMUnmanned LM Earth orbit, test of descent and ascentengines
Apollo 6 4-Apr-68 Saturn V - CSM - LTAS-IVB failed to restart, TLI demo aborted, unmannedCM reentry
Apollo 7 11-Oct-68 Saturn IB - CSM Manned CM Earth orbit and reentry
Apollo 8 21-Dec-68 Saturn V - CSM Manned CSM lunar orbit
Apollo 9 3-Mar-69 Saturn V - CSM - LMManned CSM and LM Earth orbit, EVA, separation andrendezvous
Apollo 10 18-May-69 Saturn V - CSM - LM Manned lunar orbit and partial lunar descent
Apollo 11 16-Jul-69 Saturn V - CSM - LM Manned lunar landing, EVA (Extravehicular Activity)
Apollo 12 14-Nov-69 Saturn V - CSM - LM Precision manned lunar landing near Surveyor 3, EVA
Apollo 13 11-Apr-70 Saturn V - CSM - LMSM oxygen tank explosion aborted mission, shortenedto translunar return
Apollo 14 31-Jan-71 Saturn V - CSM - LM Manned lunar landing, EVA
Apollo 15 26-Jul-71 Saturn V - CSM - LMManned lunar landing, exploration in Lunar RovingVehicle (LRV), lunar subsatellite launch, EVA
Apollo 16 16-Apr-72 Saturn V - CSM - LMManned lunar landing, exploration in LRV, lunar sub-satellite launch, EVA
Apollo 17 7-Dec-72 Saturn V - CSM - LM Manned lunar landing, exploration in LRV, EVA
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Mission Vehicles The Launch Escape System (LES) at the top of the
vehicles carrying a CM could pull the astronauts away
from a malfunctioning Saturn early in the launch. The
LES was jettisoned soon after the first stage had shut
down and the second stage ignited. The Spacecraft
Lunar Module Adapter (SLA) was designed to house the
LM, but was empty on AS-201 and AS-202. Apollos 4and 6 carried LM Test Articles (LTA), test vehicles that
did not leave the SLA. Apollos 5, 9, and 10 carried LMs
that maneuvered after separation from the SLA and the
CM. The Instrument Unit (IU) contained the navigation,
guidance, control, and communications systems that
controlled the mission up to separation of the spacecraft
from the S-IVB.
Figure 2 shows the combined Command Module
and Service Module (CSM). Three of the four Reaction
Control System (RCS) clusters of rockets attached to the
SM that determined CSM attitude can be seen. The bell-
shaped nozzle of the Service Propulsion System (SPS)
rocket engine is at the bottom of the figure. High-pres-
sure helium forced SPS propellants2 out of their tanks
into the combustion chamber. However, in the weight-
less condition of orbital and coasting flight, liquids can
drift away from the outlets leading to the combustion
chamber. To prevent helium from entering the combus-
tion chamber, it was necessary to settle the fuels by
“ullage” burns of the RCS to force the liquids to the out-
lets before opening the fuel valves.
The CM appears in Figure 3. The pitch, roll, and
yaw RCS engines gave full control of CM attitude after
separation from the Service Module.
Figure 2. Command ServiceModule (CSM).3Figure 1. Launch vehicles for missions
discussed in this article.1
through the atmosphere. The non-orbitalflight lasted 37 minutes, starting at CapeKennedy and ending with splashdown ofthe CM in the Atlantic 8,476 km away. SeeFigure 4. (The legend for Figure 4 and thelist of major events are given in Table 2.)
The Saturn IB vehicle had two pow-ered stages: the S-IB first stage and the S-IVB second stage. The S-IB lifted the mis-
sion to 58.9 km altitude 62.0 km downrange in 2.44minutes.6 It separated from the S-IVB, which fired itssingle gimbaled J-1 engine for 7.56 minutes7 and shutdown at 250.5 km altitude 1592.3 km downrange.(The step in the trajectory during the early part of theS-IVB firing was due to the difference between thethrust of the S-IB and the S-IVB. At the end of the S-IB flight the acceleration due to the eight H-1 enginesof the S-IB (thrust/mass) was 41.6 m/sec2, whereas atS-IVB ignition its single J-1 engine producedthrust/mass of only 7.25 m/sec2)8 As the S-IVB/CSMvehicle continued to coast, the Instrument Unit con-trolled a pitch down of 109.15 degrees9 to put theCSM in the attitude at which the Service Modulewould later fire its Service Propulsion System(SPS).10 The CSM separated from the S IVB andfired the RCS for 18 sec in the +X direction (towardthe pointed end of the CM) to increase their separa-tion. The CSM coasted through its apogee of 492.0km11 and ignited the SPS for three minutes. The SPSwas turned off and then restarted for a second, shortburn of ten seconds. Two RCS +X translation maneu-vers settled the SPS propellants.
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Figure 3. Command Module (CM).4
Table 2. Major events ofAS-201 mission.13
First Device: Automated Control System
Apollo-Saturn 201 (AS-201) had manyobjectives. The Apollo Program FlightSummary Report list of AS-201’s goals cov-ers three-and-a-half pages.5 It was the first—Saturn IB flight; Mission controlled by theMission Control Center (MCC) in theManned Spacecraft Center (MSC) inHouston; Flight of the Block I CommandModule (CM) and Service Module (SM);Start and restart of the Service PropulsionSystem (SPS), the main rocket carried by theSM; Recovery of the CM after reentry
LABEL EVENT TIME (sec) VEHICLE
1 Launch 0.0 S-IB
Start pitch and roll 11.20 S-IB
Roll stop 20.55 S-IB
Pitch stop 134.39 S-IB
2 S-IB cutoff 146.9 S-IB
S-IB/S-IVB separation 147.76 S-IVB
S-IVB ignition 149.35 S-IVB
LES tower jettison 172.64 S-IVB
3 S-IVB cutoff 602.9 S-IVB
S-IVB pitch down start 613.95 S-IVB
4 S-IVB pitch down end 728.3 S-IVB
5 S-IVB/CSM separate 844.9 S-IVB
RCS +X translation 1 on 846.7 CSM
RCS +X translation 1 off 864.6 CSM
6 CSM apogee 1020.0 CSM
RCS +X translation 2 on 1181.2 CSM
7 SPS burn 1 start 1211.2 CSM
RCS +X translation 2 off 1212.2 CSM
8 SPS burn 1 end 1395.2 CSM
RCS +X translation 3 on 1395.7 CSM
9 SPS burn 2 start 1410.7 CSM
RCS +X translation 3 off 1420.7 CSM
10 SPS burn 2 end 1420.7 CSM
11 C/SM separate 1455.0 CSM
12 Blackout start 1580.0 CM
13 Blackout end 1695.0 CM
14 Drogue parachute deployed 1855.4 CM
15 Main parachute deployed 1908.4 CM
16 Splashdown 2239.7 CM
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Figure 4. Trajectory andevents of AS-201.12
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Figure 5. AS-201 automated control system block diagram and interfaces.15
The Command Module for
AS-201 carried an automated con-
trol system to perform functions
that in an operational spacecraft
an astronaut would make by inputs
to the PGNCS. The device con-
trolled the CSM Reaction Control
System (RCS); Service Propulsion
System (SPS) start and stop;
CM/SM separation; CM RCS;
Parachute deployment; Reception
of uplinked commands. Figure 5
shows the system block diagram.
The components on the right side
of this diagram, outside the dashed
box defining the automated control
system, were part of the Block 1
Command Module.
The Stabilization Control
Subsystem (SCS) included two
gyro assemblies with three body-
mounted gyros that sensed space-
craft attitude.14 The automated
control system had an Attitude
Reference System (ARS) that was
backup to the SCS gyros.
When the S-IVB
Instrument Unit sensed separation
of the spacecraft, it signaled the
Automated Command Control
(ACC) to start the Sequential
Timer. This timer, developed for
the Agena B, controlled 22 events
for missions lasting up to 2,498
seconds. The normal events are
listed in Table 3. The timer used a
motor-driven mechanism to rotate
cams to open and close 22 switches
at times determined by the shape of
cams. Changes to the program
could be made up to two weeks
before integrated testing began at
KSC, by cutting new cams.
Another timer for abort events
could store 14 times. The selection
of abort or normal program was
signaled by the Instrument Unit
(before separation) or by Mission
Control from the ground.16 Before
the SPS fired, its gimbals were set
to point its thrust through the vehi-
cle center of mass, which changed
during a mission as fuel burned off.
Without this preliminary setting,
when the SPS turned on, excessive
RCS fuel would be used to keep the
vehicle accelerating in the correct
direction.
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Table 3. Events controlled by sequence timer for normal mission.17
The block diagram of a fully oper-
ational CSM with astronaut and
PGNCS appears in Figure 6. The
dashed box indicates components
missing from AS-201. Two of
these astronaut controls are shown
in Figure 7 and Figure 8.
Interfaces to the SCS for these
devices and the others missing
from AS-201 were used by the
automated control system.
Commands to the SPS could be
transmitted through the PGNCS
interface. The +X translation com-
mands could use the translation
control interface. Pitch and roll
commands might pass through the
rotation control interface.
EVENT TIME COMMENT
1 Start normal timer. 663.1 IU signal to start separation sequence.
2 Tape recorders OFF. 665.2
3S-IVB/spacecraft separation signal ON.Uncage SC gyros.
843.2
4S-IVB/spacecraft separation signal OFF.Plus-X translation ON.
846.7 First RCS burn, of 18 sec.
5 Plus-X translation OFF. 864.6
6 Plus-X translation ON. First gimbal position set. 1181.2Second RCS burn starts 5 min (316.6 sec)after the first, to settle SPS fuel in tanks(ullage burn).
7 Primary SPS gimbal motors ON. 1196.1
8Secondary SPS gimbal motors ON. Remove primarymotors ON command.
1197.1
9 Remove secondary motors ON command. 1197.1
10 Arm SPS thrust solenoids. SPS thrust ON. 1211.2
11 Tape recorders ON. 1321.9
12 Plus-X translation OFF. SPS thrust OFF. 1395.2 SPS and RCS burns end after 3 min (184 sec).
13 SPS thrust ON (secondary source on SPS control). 1395.4
14Plus-X translation ON. SPS thrust OFF.Second gimbal position set.
1395.7 Third RCS burn, to settle SPS fuels.
15 SPS thrust ON. 1410.7 Second SPS burn, for 10 sec.
16 SPS thrust OFF. Plus-X translation OFF. 1420.7
17 Pitch rate (-5 deg/sec) ON. 1424.1 The CSM pitches over 90 deg in 18 sec.
18 Pitch rate (-5 deg/sec) OFF. 1442.1
19 CM/SM separation start. SCS entry mode ON. 1454.2 8 sec later the CM separates from the SM.
20 Pitch rate (-5 deg/sec) ON. 1462.6 The CM pitches over 82.5 deg in 16.5 sec.
21 Pitch rate (-5 deg/sec) OFF. Roll rate (+5 deg/sec) ON. 1479.1 The CM rolls 180 deg in 36 sec.
22Ross rate (+5 deg/sec) OFF. Arm 0.05g backup. ELSactivate.
1515.1
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Figure 9 Mission AS-202 Command Module altitude duringentry.21
Figure 8. Translation control.20
Second Device: Mission Control Programmer
Mission AS-202 was another suborbital test of
CM reentry launched by a Saturn IB. The major dif-
ference from AS-201 was the presence of the PGNCS.
It oriented the CSM for SPS firing after separation
from the S-IVB, while for AS-201 the IU set the CSM
attitude before separation. The PGNCS cued RCS and
SPS firing on AS-202, whereas these events occurred
on AS-201 at predetermined times. Also, the PGNCS
controlled CM attitude during entry to achieve a one-
skip trajectory. See Figure 9.
Figure 6. Interfaces available to the automated control system.18
Figure 7. Rotation control, aka controlstick steering (CSS).19
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Figure 10. The three components of the Mission Control Programmerinstalled in place of CM crew couches.24
Table 4 Key commands input to theMission Control Programmer.26 SeeFigure 11 for a diagram of the MCP andits interfaces. The MCP contained morethan 1,050 relays.27
Apollo 4 was the first flight of a
Saturn V launch vehicle, and put a
CSM and a LM Test Article into
Earth orbit. The orbital mission
allowed a period of “cold soak”
which achieved the thermal condi-
tions of an operational mission. The
CM was oriented for four-and-one
half hours with the sunlight perpen-
dicular to the CM hatch, so that a
thermal gradient was created across
the surface of the heat shield. Other
changes from AS-201 and AS-202were the start and restart of the SPS
without ullage burns of the RCS,
and a simulated Translunar
Injection (TLI) burn by the S-IVB
that raised the CSM to an altitude
much higher than earlier missions.
This produced a higher entry veloc-
ity and a heating rate similar to the
maximum conditions during a lunar
return.22
Although the mission plan for
the Apollo 6 mission was similar to
that of Apollo 4, several failures
caused Mission Control to order an
alternate program. The S-IVB did
not start for its scheduled TLI burn
so the SPS was used instead to
achieve the planned apogee (12,000
n mi). The MCC cancelled the sec-
ond burn of the SPS due to the extra
use of fuel to make up for the S-
IVB failure, and the entry velocity
was lower than Apollo 4. Near the
end of the first stage (S-IC) firing,
large 5 Hz oscillations exceeded the
spacecraft design criteria, causing
pieces of the SLA to shake loose
from the vehicle.
The Mission Control
Programmer (MCP) took the place
of an astronaut on missions AS-202,
Apollo 4, and Apollo 6.23 It con-
sisted of three components, shown
in Figure 10: the Attitude and
Deceleration Sensor (ADS), the
Spacecraft Command Controller
(SCC), and the Ground Command
Controller (GCC).
The ADS contained
accelerometers to back up accelerom-
eters in the PGNCS. Several events
were triggered by the start of entry,
which occurred at approximately
400,000 feet altitude, when decelera-
tion due to the atmosphere reached
0.05 g. This was sensed by the
PGNCS and the ADS. If the PGNCS
failed the ADS also provided backup
measurement of spacecraft attitude.
The MCP accepted keying com-
mands from four sources and sent
sequence commands to spacecraft
components. The SCC took inputs
from three sources, and the GCC
received inputs from the Mission
Control Center. For AS-202 the SCC
received the eleven key commands
from the PGNCS listed in Table 4.
Two of these commands were deleted
for Apollos 4 and 6. Other key com-
mands to the SCC came from Launch
Control at KSC while the mission
was on the launch pad and from the
Instrument Unit before separation of
the CSM from the S-IVB.25
SOURCENUMBER OFCOMMANDS
EXAMPLES
PGNCS11 (9 for Apollos
4 and 6)
Flight director attitude indicator alignment / Gimbalmotors / G&N fail / 0.05g / Positive-X translation /CM and SM separation / G&N entry mode / G&Nchange in velocity ΔV mode /G&N attitude controlmode. G&N abort* / Positive- or negative-Z antennaswitching* (* Removed for Apollos 4 and 6)
IU 4S-IVB restart / LES jettison / Liftoff /S-IVB-CSM separation
LaunchControl
12Arm/disarm pyrotechnics / Switch off logic buses /Operate flight recorders / Restart MCP
MCC 59
Fuel cell purge / Lifting entry / SPS on-off / Pitch-roll-yaw / Ullage / RCS propellant on-off / LESjettison / Antennas on-off / CM-SM separation /Radios on-off
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Figure 11. Mission control programmer interfaces.28
Third Device: Lunar ModuleMission Programmer
Apollo 5 was the first flight of
the Lunar Module. It tested the
descent engine, separation of the
ascent and descent stages during a
simulated aborted landing, and the
ascent engine. Despite several mal-
functions the mission objectives
were met. Under control of the
PGNCS, the LM separated from
the S-IVB and began to execute the
planned program. The LM
assumed a cold soak attitude for
three hours, and then reoriented for
the first descent engine firing. The
first malfunction came at four sec-
onds after the start of the first
descent engine burn, when the
PGNCS shut down the engine pre-
maturely due to “incomplete sys-
tem coordination.”29 The MCC
shifted control from the PGNCS to
the LM Mission Programmer
(LMP). The LMP directed the sec-
ond and third firing of the descent
engine, the separation of the
descent and ascent stages, and the
first ascent engine firing. Then the
MCC returned control to the
PGNCS. The next malfunction
occurred as the PGNCS operated
the RCS to maintain vehicle atti-
tude but burned too much fuel
because its calculations used the
mass of the LM at the time of the
first malfunction before staging
and the use of fuel during three
engine firings. Control was
returned to the LMP for the second
firing of the ascent engine. In the
last malfunction, the LMP closed
the fuel interconnect valves, lead-
ing to fuel depletion for the RCS,
and the vehicle began to tumble
while the ascent engine was firing.
The trajectory reconstruction esti-
mated that the LM impacted in the
Pacific Ocean 400 miles west of
Central America.30
See Figure 12 for a compari-
son of planned and actual events
during Apollo 5. Note that there
was a one-and-one-half hour peri-
od between the first ascent engine
firing and the second, during which
PGNCS control of the LM led to
excessive RCS fuel expenditure.
The Apollo 9 mission was a
manned flight test in Earth orbit of
the CSM and LM. The CSM had
performed well on two previous
manned missions, Apollos 7 and 8,
so the principal objective of Apollo9 was the first manned flight test of
the LM. The LM separated from
the CSM and practiced descent,
ascent, and rendezvous maneuvers.
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Figure 13. Lunar Module mission programmer block diagram.36
Figure 12. Control of Apollo 5 events.31
After docking with the
CSM and crew transfer to the
CSM, the unmanned LM was jetti-
soned and the ascent engine was
fired to fuel depletion. The only
unmanned portion of the mission
was the last firing of the LM ascent
propulsion system, which put it in a
highly elliptical orbit (3,761 x 127
miles).32
Apollo 10 was a manned mis-
sion to the Moon with the LM sep-
arating from the CSM in lunar
orbit, descending to nine miles
above the surface of the Moon, and
rejoining the CSM. After the LM
crew reentered the CSM, the LM
was jettisoned and the unmanned
ascent stage fired to fuel depletion,
putting it into a solar orbit.33
To control the LM during
unmanned flight, the Lunar
Module Mission Programmer
(LMP) was developed by NASA
and the LM contractor, Grumman
Aerospace. The LMP could also
replace some functions of the
PGNCS if the latter malfunctioned.
The LMP consisted of four compo-
nents: a program reader assembly
(PRA), a digital command assem-
bly (DCA), a program coupler
assembly (PCA), and a power dis-
tribution assembly (PDA).34 The
PRA contained a program written on 35mm film read by a photodiode array.
It had a capacity of 64 kbits (about one-third the size of the rope memory of
the LGC).35 PRA words were 8 bits long, and the program consisted of
sequences. The film drive was bidirectional, so that the MCC could select
which sequence to run. During Apollo 5, sequences III and V were executed
while the LMP was in control of the vehicle. The DCA, a UHF transceiver
and coder, received ground commands to control the LM. These commands
could be input to the LM Guidance Computer (part of the PGNCS), to the
PRA, and to the PCA. The PCA connected the LMP to the reaction control
system; the descent engine; the ascent engine; and the explosive devices sub-
system that separated the ascent and descent stages. The PCA contained a
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decoder that received digital com-
mands from the LGC or from the
PRA and sent signals to the switch-
ing subassembly. That contained a
prime matrix of relays and another
matrix that could be controlled
from the ground to replace relays in
the prime matrix that malfunc-
tioned. Figure 13 is a block dia-
gram of the LMP and its interfaces.
Initially on the Apollo 5 mis-
sion, after nose cone jettison and
SLA panel deployment, the
PGNCS controlled the LM to sepa-
rate from the S-IVB stage, to reori-
ent into the attitude it would hold
for a three-hour cold-soak, and to
maneuver to the attitude for firing
the descent engine. It initiated the
descent engine firing, but shut it
down after just four seconds of the
planned 38 second firing. The LM
Guidance Computer (LGC) entered
idle mode (P00) after premature
shutdown, and the Mission Control
Center transferred control to the
LMP and commanded the PRA to
read sequences III and V. Modified
versions of the LMP flew on
Apollos 9 and 10 to arm the ascent
engine for its last firing. Figure 14
shows that while the LGC could
issue ascent engine on/off com-
mands, they would not be per-
formed without prior astronaut
commands to pressurize and arm
the engine. Pressurization involved
opening six explosive valves, a
one-time operation. During Apollos9 and 10, astronauts performed the
pressurization during ascent. For
the final firing of the ascent engine
to fuel depletion, it was only neces-
sary for the LMP to close the arm
switch.
For Apollo 9 the LMP omitted
the PRA and replaced the PCA with
the ascent-engine arming assembly
(AEAA). The Apollo 10 version of
the LMP replaced the UHF DCA
with the Unified S-Band digital
uplink assembly and incorporated an
AEAA which could not only arm the
ascent engine but could switch from
PGNCS control to Abort Guidance
System control to execute the burn to
fuel depletion. Subsequent models of
the LM incorporated the AEAA into
the Control Electronics Section.38
However, Apollo 10 was the last mis-
sion to fire the ascent engine to
depletion. Table 5 shows that during
Apollo missions 12, 14, 15, and 17
the RCS was used to effect a con-
trolled deorbit of the ascent stage.
Controlled deorbit ended with impact
at a known location, which allowed
calibrated measurement of data from
seismometers left on the Moon. The
LGC initiated the maneuver after the
MCC signaled from the ground.39
No deorbit was ordered during
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During Apollo 16, after ascent stage
jettison from the CSM, attitude control of
the LM was lost and controlled deorbit
was not possible.
The devices and their components
used to control unmanned Apollo space-
craft are shown in Table 6. The functions
of the components are shown in the first
column. The sequential timer of AS-201
was a mechanical clockwork device sim-
ilar to that used on the V-2. It was
replaced on Apollo 5 by a film strip,
which was the backup to the program
stored on the LGC. The interface compo-
nents in the last row were made of relays,
diodes, and time delays.
AcknowledgmentsThe author is grateful for the many suggestions
made by his wife, Mariana T. Durbin, who copy-
edited this article.
About the Author Edgar Durbin has worked part-time at the
Smithsonian Institution National Air and Space
Museum, Department of Space History, since retir-
ing from government service in 2002. Most of his
research there has been on the navigation, control,
and guidance of rockets. He received a bachelor of
arts degree in mathematics from Harvard University
in 1962, a bachelor of arts degree in physics from
Oxford University in 1964, a doctorate in physics
from Rice University in 1972, and master’s degree in
public administration from the Kennedy School of
Government at Harvard in 1977.
Notes1 Postlaunch Report for Mission AS-201, NASA MSC, 6 May1966, Figure 4.0-1, p. 4-2; Postlaunch Report for Mission AS-202,NASA MSC, 12 October 1966, MSC-A-R-66-5, 4-2; Apollo 4Mission Report, NASA MSC, January 1968, MSC-PA-R-68-1, 13-2.
2 The SPS used Aerozine 50 (a 50/50 mix by weight ofhydrazine and unsymmetrical dimethylhydrazine) as fuel andnitrogen tetroxide (N2O4) as oxidizer. They immediately react oncontact (hypergolic).
3 S.I. Jimenez and B.C. Grover, Apollo Training: Apollo Spacecraft& Systems Familiarization. Course Number APC-118, NorthAmerican Aviation, Space Division, Downey, CA. 15 August 1967.
4 Apollo Operations Handbook, Command and Service Module,Spacecraft 012, SM2A-03-SC012, 12 November 1966, Figure 1-3.
5 Apollo Program Fight Summary Report, Apollo Missions AS-201 through Apollo 16, NASA Office of Manned Space Flight, June1972. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740013403.pdf
6 Postlaunch Report for Mission AS-201, Table 5.0-I.
7 Results of the First Saturn IB Launch Vehicle Test Flight AS-201, NASA MSFC, 6 May 1966. Table 4-I.
8 For vehicle mass, see AS-201 Results Table 6-II. For thrust,see AS-201 Results Figure 9-6 and Figure 8-2.
9 AS-201 Results, Figure 12-14.
10 Gene F. Holloway, Automated Control System for UnmannedMission AS-201, NASA JSC, July 1975, NASA TN D-7991, Table II.SPS burn 1 started 1211.2 sec. AS-201 Results, Table 4-1,Achieved Separation Attitude 728.31. 1211.2-728.31=482.89sec= 8.05 min.
11 Postlaunch Report for Mission AS-201, Table 5.0-I, 5-7.
12 Postlaunch Report for Mission AS-201, Figure 2.0.1
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Apollo 11, and LM-5 made an uncon-
trolled deorbit to an unknown crash site.
MISSION SPACECRAFT UNMANNED MANEUVERApollo 9 CSM 104, LM-3 Ascent engine fired to depletion
Apollo 10 CSM 106, LM-4 Ascent engine fired to depletion
Apollo 11 CSM 107, LM-5 None
Apollo 12 CSM 108, LM-6 RCS fired to controlled deorbit
Apollo 13 CSM 109, LM-7 Mission aborted
Apollo 14 CSM 110, LM-8 RCS fired to controlled deorbit
Apollo 15 CSM 112, LM-10 RCS fired to controlled deorbit
Apollo 16 CSM 113, LM-11 None
Apollo 17 CSM-114, LM-12 RCS fired to controlled deorbit
Table 6. Evolution of control devices.
MISSION AS-201 AS-202, Apollo4 & 6 Apollo 5 Apollo 9 Apollo 10
SPACECRAFTCONFIGURATION
CM withoutPGNCS
CM with PGNCSLM withPGNCS
LM withPGNCS
LM withPGNCS
CONTROLDEVICE
Automatedcontrol system
Mission ControlProgrammer
LM MissionProgrammer
LM MissionProgrammer
[A]
GROUND COM-MUNICATIONS
RadioCommandControl
GroundCommandController
DigitalCommandAssembly
DigitalCommandAssembly
DigitalUplinkAssembly
PROGRAMSequentialTimer
[B]ProgramReaderAssembly
[B] [B]
ATTITUDEREFERENCE
AttitudeReferenceSystem
Attitude andDecelerationSensor
[B] [B] [B]
INTERFACE TOSPACECRAFT
AutomatedCommandControl
SpacecraftCommandController
ProgramCouplerAssembly
AscentEngineArmingAssembly
AscentEngineArmingAssembly
Notes: [A] Function was performed by components of the Communications System and ControlElectronics System of the Lunar Module. [B] Functions were performed by the PGNCS.
Summary
Table 5. Maneuvers of unmanned Lunar Modules40
Q U E S T 25:3 201838
13 AS-201 Results, Table 21-1, 261; Table4-1, 8; Postlaunch Report for Mission AS-201, Figure 20-1, 2-3.
14 Michael Interbartolo, Apollo Guidance,Navigation, and Control (GNC) HardwareOverview, NASA JSC, 2009. Briefing slides,PDF 60 pages.
15 Holloway AS-201, 2, Figure 1.
16 Holloway AS-201, 2.
17 Holloway AS-201, Table II, 4.
18 Adapted from Figure 2.3-1, ApolloOperations Handbook Command andService Module Spacecraft 012, 2.3-2,North American Aviation, 12 November1966, SM2A-03-SC012.
19 Apollo Operations Handbook Commandand Service Module Spacecraft 012, Figure2.3-8, 2.3-58.
20 Adapted from Figure 2.3-8, ApolloOperations Handbook Command andService Module Spacecraft 012, 2.3-58 andfrom Interbartolo, Apollo GNC Overview.
21 Ernest R. Hillje, Entry FlightAerodynamics from Apollo Mission AS-202,NASA MSC, October 1967, NASA TN D-4185,Figure 5.
22 Apollo 4 Mission Report, NASA MSC,January 1968, MSC-PA-R-68-1, Section 1.0.
23 The spelling “programer” (one m) wasused consistently in the 1975 ApolloExperience Reports about the MCP and theLMP. The spelling used in the 1966 MSCpostlaunch report on mission AS-202 was“programmer.”
24 Gene F. Holloway, Mission ControlProgramer for Unmanned Missions AS-202,Apollo 4, and Apollo 6, NASA JSC, July 1975,TN D-7992, 3.
25 Holloway, Mission Control Programmer.
26 Holloway, Mission Control Programmer.
27 Holloway, Mission Control Programmer, 43.
28 Holloway, Mission Control Programmer,Figure 4 with changes.
29 The MSC made a change in the missionplan that was not communicated to the LGCdesigners at MIT. Don Eyles, Sunburst andLuminary, An Apollo Memoir, 4; Final FlightEvaluation Report Apollo 5 Mission, NASAOffice of Manned Space Flight, October1968, D2-117017-2 Rev. C, 29.
30 Apollo 5 Mission Report, NASA JSC,March 1968, MSC-PA-R-68-7, 1-2.
31 Apollo 5 Mission Report, Figure 2-1, 2-6.
32 Apollo 9 Mission Report, NASA MSC,May 1969, MSC-PA-R-69-2, 7-9.
33 Apollo 10 Mission Report, NASA MSC,August 1969, MSC-00126, 3-2.
34 Jesse A. Vernon, Lunar Module MissionProgrammer, NASA JSC April 1975. NASA TND-7949.
35 Eldon C. Hall, General Design Charact-eristics of the Apollo Guidance Computer, MITInstrumentation Laboratory, May 1963, 4.
36 Diagram based on text description inVernon, LMP.
37 Lunar Module News Reference,Grumman Aerospace Public Affairs, MP-16.https://www.hq.nasa.gov/alsj/LM_%20NewsReference_%28267_pp%29.pdf
38 Apollo Operations Handbook LunarModule LM 10 and Subsequent, Vol 1,Subsystems Data, Grumman, LMA790-3-LM10 and Subsequent, 2.1-24. https://www.hq.nasa.gov/alsj/LM10HandbookVol1.pdf
39 Apollo 12 Spacecraft Commentary,NASA MSC, 473/1. https://www.jsc.nasa.gov/history/mission_trans/AS12_PAO.pdf
40 Various mission reports.
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