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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

www.spacehistory101.com

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

Q U E S T 25:3 201827


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

Q U E S T 25:3 201828


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.


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


7 SPS burn 1 start 1211.2 CSM


8 SPS burn 1 end 1395.2 CSM


9 SPS burn 2 start 1410.7 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

Q U E S T 25:3 201829

Figure 4. Trajectory andevents of AS-201.12

Q U E S T 25:3 201830


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.

Q U E S T 25:3 201831


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

Q U E S T 25:3 201832


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

Q U E S T 25:3 201833


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

Q U E S T 25:3 201834


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.

Q U E S T 25:3 201835


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

Q U E S T 25:3 201836


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

Q U E S T 25:3 201837

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


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 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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