n

•••

DISCOVERER XXVII

(Thor 322/APIV6M21—

SYSTEM TEST EVALUATION

AND

PERFORMANCE ANALYSIS REPORT

(35-Day Report)

Title Unclassified

Contract AF 04(647)458
CLASSIFICATION CHANGED TO

APPROV

PLUMMER

ER, DISCOVERER PROGRAM

CE SYSTEMS

SSD-T61-30 1111101111111.C - 461-3 46240.0

10

25 August 1.V.

Copy No.'"°—C-

/0 "

DISCOVERER XXVII

(Thor 322/AgoniaUf)_

SYSTEM TEST EVALUATION

AND

PERFORMANCE ANALYSIS REPORT

(35-Day Roport)

Title UnaIsmailia

Contract AF 04(647)-558

Proporod under authority of AFBM Exhibit 60.06

Paragraph 1.4.1

Prepared by

TEST DATA ANALYSIS

62-42

DOTACRACIED AT 3 VIAR ROOM*

oscustarat wet I; Iva

coo 01113:011 MU*

APPROVED:

R. WELLER

ENGINEERING DIRECTOR

SPACE SYSTEMS

rt:Ir!fi stk.

'f•

This dosernont contains Information tho•noti000l defonso of the United Stertos within

the mooning of the Esplownpo Laws, Tide It, U. S. C., See. 793 and 794. Its transmission or

'the roveledien of its eontords In any moaner to an ornrothorbod penon is prohibited by low.

45 •-.2 7 6 9

LOCKHEED AIRCRAFT CORPORATION ACE DIVISION

. •
r 4-21 6 g

MISSILES and SPACE DIVISION

LMSC-446240- 10

Discoverer XXVII (Thor 322/Agena 1110) at Liftoff From Complex S14-75-3, Pad 4, VAFB

LOCKHEED AIRCRAFT CORPORATION
LMSC -446240-10

FOREWORD

Administered by the Air Force Space Systems Division (AFSSD), the

Discoverer Program has as its principal objectives the development

of Thor-boosted Agena satellites, capable of functioning as carriers

for scientific materials, and the recovery of capsules ejected from

orbiting Agenas.

As prime contractor, Lockheed Missiles and Space Company, Space

Systems Division, has overall responsibility for developing the

program. Development of the Thor as a booster rocket for the Agena

satellite has been carried out by the Douglas Aircraft Company.

This document is the final system test evaluation and performance

report for the flight of Discoverer XXVII from Vandenberg Air Force

Base on 21 July 1961. The report has been prepared in compliance

with a requirement of Contract AF 04(647)-558 and in accordance

with Paragraph 1.4.1 of LMSD-445158-B, Discoverer Program.

iii

6 r -276 g

LOCKHEED AIRCRAFT CORPORATION 1111111111111=1111111 MISSILES and SPACE DIVISION
11111111111iii

LMSC -446Z40-10

SUMMARY

Discoverer XXVII, consisting of Thor booster 322 and Agena satellite 1110, was launched on

the first attempt from Vandenberg AFB, Thor Complex SM-75-3, Pad 4, on 21 July 1961. The

Agena carried a recoverable research payload in a Mark V capsule.

Beginning at liftoff, a divergent oscillation developed in the booster's pitch plane and continued

until 59.62 seconds, when the Discoverer began to disintegrate. Disintegration of the Agena was

preceded either by structural failure of the adapter, followed by automatic actuation of the destruct

mechanism, or by structural failure of the Agena's propellant tanks at the midbody, followed by

hypergolic reaction of the propellants.

An investigation by DAC has revealed that the malfunction which led to flight failure was within

the Thor's main-engine pitch-rate shaping network. An open-circuit wiring error prevented pitch

rate signals from reaching main-engine controls.

V

LOCKHEED AIRCRAFT CORPORATION MISSILES and SPACE DIVISION
LMSC-446240-10

CONTENTS

Page

FOREWORD

SUMMARY

ILLUSTRATIONS AND TABLES is

SECTION 1 INTRODUCTION 1-1

SECTION 2 FLIGHT PERFORMANCE 2-1

Prelaunch Operations 2-1

Launch and Ascent 2-1

Flight Mechanics 2-1

Thor Subsystems Performance 2-5

vii

LOCKHEED AIRCRAFT CORPORATION MISSILES and SPACE DIVISION
LMSC-446240-10

ILLUSTRATIONS

Flows

Frontispiece Discoverer XXVII (Thor 322/Agena 1110) at Liftoff From Complex

SM-75-3, Pad 4, VAFB

2-1 Velocity During Thor Boost 2-3

2-2 Altitude During Thor Boost 2-3

2-3 Flight-Control System (Pitch Plane) 2-6

2-4 Shaping Network Schematic 2-8

TABLES

• Table Ent

2-1 Sequence of Flight Events 2-2

ix

LOCKHEED AIRCRAFT CORPORATION MISSILES and SPACE DIVISION
LMSC -446240 -10

SECTION 1

INTRODUCTION

The principal objectives of the Discoverer Program are (1) the development

of Thor-boosted Agena satellites capable of functioning as carriers of scientific material, and (2) the recovery of capsules ejected from the satellites.

Additional objectives for the program are the perfecting of equipment, techniques, and procedures for launching Thor-boosted Agena satellites; attaining

orbit; and the recording, transmitting, receiving, and processing of satellite

functional and environmental data, as well as geophysical and capsule-recovery

data. It is also intended that system operational techniques and procedures,

including tracking-station, control-center, and launch-base training, will be

refined as the program progresses. Specialized tests, including aeromedical

research, will be conducted during the series of flights.

An important long-range objective of the Discoverer Program is the refinement

of the equipment and procedures which will be used in the more advanced

MIDAS and Samos Programs, as well as in future deep-space probes.

Of the 27 Discoverer-Agena satellites launched from Vandenberg AFB to date,

18 have been injected into orbit. Present plans call for the launching of nine

additional satellites in the Discoverer Program.

1-1

LOCKHEED AIRCRAFT CORPORATION MISSILES and SPACE DIVISION
L MSC -446240-10

SECTION 2

FLIGHT PERFORMANCE

' PRELAUNCH OPERATIONS

The launch countdown of Discoverer XXVII (Thor 322/Agena 1110) from Thor

Complex SM-75-3, Pad 4, was initiated at 0615 PDT on 21 July 1961 and

proceeded to liftoff after 9 hours and 21 minutes. Three holds totaling 56 minutes were imposed during the count.

LAUNCH AND ASCENT

Liftoff of Discoverer XXVII was successfully accomplished at 1535:00.46 PDT,

with a clean umbilical disconnection and only minor pad damage.

Beginning at liftoff, booster instability in the pitch plane was evident. This

instability ultimately resulted in structural failure of the Discoverer at approximately 59.62 seconds. A sequence of flight events is included as Table 2-1.

Tracking data obtained from the Mod II VERLORT at VTS and substantiated

by FPS-16 skin-track radar at PMR show that the ascent trajectory of the

Discoverer was nominal until approximately 56 seconds. Thereafter, it deviated (Figs. 2-1 and 2-2). When the Agena's S-band beacon was lost at

approximately 184 seconds, the Agena was at 13,000 feet downrange. Data

indicate that the Agena reached a maximum altitude of 34,500 feet, whereas

the Thor continued upward and farther downrange. Loss of FPS-16 track at

approximately 60 seconds prevented the plotting of the Thor's full trajectory.

FLIGHT MECHANICS

Beginning at liftoff, a diverging, rigid-body oscillation in the vehicle pitch

plane was recorded. The frequency of the oscillation was approximately

2-1

LOCKHEED AIRCRAFT CORPORATION MISSILES and SPACE DIVISION
LMSC-446240-10

Table 2-1

SEQUENCE OF FLIGHT EVENTS

EVENT

SYSTEM TIME

(SEC)

FLIGHT TIME

(SEC)

Liftoff 81300.46 0

Thor Pitch Oscillation Starts 81300.46 + 0 +

Thor Roll Program Complete 81315.46 15

Agana Pitch Actuator Oscillations Stop 81340.46 40

First Major Positive Pitch Rate Starts 81347.98 47.52

Second Major Positive Pitch Rate Starts 81357.09 56.63

Flash at Agana Nose (probably sun reflection) 81359.27 59.27

Agana Telemeter Signal Loss 81360.08 59.62

Agana CWAT Signal Loss 81360.08 59.62

Ayala Pitch Accelerometer Indicates Maximum G's Prior to Failure 81360.08 59.62

Alma Accelerometers Fail (all indicate zero volts during

intermittent telemeter reception) 81360.08 59.62

Thor Fuel-Pump Inlet Pressure Drop Starts 81360.08 59.62

Thor Electrical Power Loss (except telemetry) 81360.08 59.62

Thor Main-Engine and Vernier-Engine Cutoff (70% Pc ) 81360.21 59.75

Flame Near Adapter Section 81360.27 59.81

Two Small Flames Near Tail of Thor 81360.44 59.98

Solid Flames on Thor 81361.29 60.83

Last Evidence of Agana Telemeter Operation 81375.83 75.37

Thor Telemeter Signal Strength Drops 81376.27 78.64

White Burst of Gas (probably escaping liquid oxygen) 81379.27 78.81

Thor Commutators Stop 81379.90 79.44

Destruct Armed 81393.46 93.00

Destruct Command 81395.56 95.10

LOCKHEED AIRCRAFT CORPORATION MISSILES and SPACE DIVISION
A DATA

VTS VERLORT

POINTS FROM /

I!—,PREDICTED

VELOCITY

INERTIAL__

/

)

/

/

/

_.----1------"----,

60"

--(=-TaTY 4111

EARTH REFERENCE

ACTUAL INERTIAL

ACTUA- VELOCITY

A A

6000

1

g

Si

200

40

0

20 40 60 110 100 140 160

4411100.10401 TIME FROM LIFTOFF (SEC)

Figure 2-1 Velocity During Thor Boost

Li ACTUAL

PROM

DATA

YTS VERLORT

POINTS

/

/

/

.

/

/

/4114"-PREDICTED ALTITUDE

/

/

i

ACTUAL ALTITUDE

AO 100 120 100

TIME FROM LIFTOFF (SEC)

Figure 2.2 Akita. During Thor Boost

2-3

LOCKHEED AIRCRAFT CORPORATION 1111111em MISSILES and SPACE DIVISION
LMSC-446240-10

0. 3 cps, which is the natural 'rigid-body frequency of the Discoverer. The

oscillation was apparent on the Thor pitch attitude error, pitch rate, engine

pitch position, and normal accelerometer data. (Loss of the Thor's controlsystem pitch-rate damping would cause such an oscillation.) At approximately

10 seconds after liftoff, a similar oscillation was apparent in the yaw plane,

but at a considerably lower amplitude. The cause of this yaw-plane oscillation

was structural cross-coupling from the pitch plane.

All Thor pitch-plane parameters went off scale 10 seconds after liftoff. The

oscillation continued to diverge until the main engine reached a maximum

gimbal of plus or minus 7 degrees. Up to 47.52 seconds, the pitch motions

were relatively symmetrical about the flight path; however, at this time, a

large pitch-up motion began. This was followed by a second pitch-up motion

of greater magnitude beginning at 56.63 seconds, which led to vehicle breakup at 59.62 seconds.

The following events occurred at approximately 59.62 seconds, substantiating

Discoverer disintegration at this time: (1) Thor electrical power in the transition section was lost, which in turn initiated main- and vernier-engine cutoff;

(2) Thor fuel-pump inlet pressure began to drop; (3) Agena normal accelerometer went to the band edge in the positive direction (+3.25 g's, pitch-up);

(4) Agena telemetry data were lost when signal strength dropped below the

threshold of reception. Weak, sporadic signals indicated continued Agena

telemetry operation from 59.62 to 75.37 seconds. These indications provided

no useful data on commutated channels other than to show that the commutators

and VCO's continued to operate. All three continuous channels used for accelerometers indicated zero volts (not zero g's) during the intermittent reception

period after 59.62 seconds. This suggests a failure in accelerometer circuitry

as a result of Agena structural failure. (5) The Agena continuous-wave acquisition transmitter signal was lost, probably because of damage to the antenna

system shared with the FM/FM telemetry system.

The following events were recorded by motion pictures taken from Mount

Tranquillone and by a T-33 aircraft (because the weather was overcast from

2-4

LOCKHEED AIRCRAFT CORPORATION 111111111111111111111

ani MISSILES and SPACE DIVISION
LMSC -446240-10

approximately 1000 to 2000 feet, photographic coverage taken from the launch

complex was inadequate for evaluative purposes): Flames first appeared near

the adapter area at 59.81 seconds. (Agena telemetry recorded loads in excess

of structural integrity at 59.62 seconds.) By 60.83 seconds, flames and

smoke enveloped the Discoverer. Still ascending, the Thor emerged from the

smoke almost tail first, trailing flames from the forward fuel tank section.

At approximately 78.81 seconds, a burst of white smoke was emitted from

the remaining portion of the Thor. The liquid oxygen tank is believed to have

exploded at this time.

The high loads imposed upon the Agena at Discoverer breakup could have precipitated either of the following sequences:

Excessively high flight loads could have caused the midbody to

break immediately forward of the fuel tank in the vicinity of

Station 294. This break would probably cause the rupture of the

Agena tanks, followed by failure of the remaining structure.

Failure could have occurred at the separation interface,

Station 388. 55, either by shear or by tension loads. If this

occurred, the destruct mechanism would have been actuated

because of premature separation of the Agena from the booster.

Thor telemetry signal strength dropped at 78. 64 seconds, and the commutators

began slowing down. Both transducer-regulated 5-volt supplies began to drop

at 78.71 seconds. By 79.44 seconds, Thor Channel 14 and 15 commutators

had stopped. At 93 seconds, the destruct system arming signal was sent;

and at 95.1 seconds, the command-destruct signal was transmitted. Since

both the Thor and Agena had disintegrated by this time, it is doubtful that the

destruct signal had any effect. At 292 seconds, the Thor telemetry signal

strength increased for a few seconds and several sync pulses were recorded.

At 312 seconds, the Thor telemetry carrier signal was lost when the Thor

impacted in the ocean.

THOR SUBSYSTEMS PERFORMANCE

With the exception of the flight-control system, Thor propulsion, hydraulic,

electrical power, and instrumentation subsystems performed satisfactorily.

2-5

LOCKHEED AIRCRAFT CORPORATION MISSILES and SPACE DIVISION
SHAPING

NETWORK

VEHICLE

DYNAMICS

ATTITUDE

GYRO

AC AMPLIFIER

DEMODULATOR

n:,?n DC AMPLIFIER

VALVE-ACTUATOR

AC

AMPLIFIER

DEMODULATOR

V 

RATE

GYRO

TO VERNIER

ENGINES

* 

INSTRUMENTATION POINTS TO VERNIER

ENGINES

SHAPING

NETWORK

ti..SIETWOit APIWK

LMSC -446240-10

Flight-Control System 

Operation of the Thor flight-control system was unsatisfactory from liftoff,

when a diverging, rigid-body oscillation in the pitch plane began, as discussed

under "Flight Mechanics. "

By comparing the phase and amplitude of main-engine pitch position with that

of the rate and attitude demodulator output data, the main engine was found

to be lagging the attitude signal by approximately ZOO degrees. This value

was theoretically shown to be the correct engine response if the rate demodulator signal were not received at the d-c amplifier input. The main engine

was responding to the attitude error signal only. A schematic of the flightcontrol system (pitch plane) is presented in Figure 2-3.

A comparison of the rate demodulator output with the derivative (slope) of the

attitude demodulator output data showed them to be coincident, indicating

PROGRAMMER

44181140-104114

Figure 2-3 Flight-Control System (Pitch Plane)

2-6

LOCKHEED AIRCRAFT CORPORATION MISSILES and SPACE DIVISION
LMSC-446240-10

proper operation of the pitch rate gyro and its associated a-c amplifierdemodulator. The vernier engines were responding properly to both the

attitude and rate demodulator outputs, further confirming that the pitch rate

gyro and its associated a-c amplifier-demodulator were operating properly.

On the basis of these facts, the malfunction must have been within the main

engine's pitch-rate shaping network.

A postflight review of engineering documentation affecting changes to the

control electronics assembly was made by DAC personnel. It was revealed

that during VA.FB laboratory checks, a pin on the connector between the main

engine shaping network and the programiner was broken. The wire to this

broken pin was moved to a spare pin on the same connector, and the plug on

the programmer side was rewired for continuity. Later, it was necessary

to replace the programmer. However, records indicate that the programmer

connector was never re-modified to match the standard programmer. Therefore, the programmer side of the plug was not compatible with the modified

plug from the main-engine shaping network. The result was an open circuit

which prevented the pitch-rate gyro signal from reaching the main engine

controls. This open-circuit condition is also the only condition that satisfies

all the characteristics encountered during the flight.

The polarity check performed at the launch emplacement did not include a test

of the main-engine shaping network, because this test results in severe gim- ,

baling of the engine. To prevent possible structural damage, the main engine

is temporarily disconnected from the circuitry during this test. Therefore,

when the rate gyros were physically displaced, only the vernier-engines.

responded (Fig. 2-4). Thus, discontinuity in the main-engine shaping network

circuitry was not detected during this test.

Corrective action to be taken on all future Discoverer boosters will be as

follows: (1) The auxiliary shaping network will be removed. This network

was originally installed to raise the d-c loop gains, thereby reducing velocity

direction errors at main-engine cutoff. However, when the BTL guidance

system was added, the need for this network was eliminated. This elimination

2 -7

LOCKHEED AIRCRAFT CORPORATION MISSILES and SPACE DIVISION
LMSC -446240-10

AC AMPLIFIER

DEMODULATOR

SHAPING

NETWORK SHAPING

NETWORK

DC AMPLIFIER

RELAY USED TO BYPASS

AUXILIARY NETWORK

DURING CHECKOUT THIS PLUG WAS

WIRED INCORRECTLY

PROGRAMMER

AUXILIARY

NETWORK

446240-10-005

Figure 2-4 Shaping Network Schematic

2-8

LOCKHEED AIRCRAFT CORPORATION MISSILES and SPACE DIVISION
MUM LMSC -446240 -10

will also obviate the need for the rate gyro signal to be routed through the

programmer. (2) The main shaping network boards within the control electronics assembly will be encapsulated to reduce the possibility of terminals

being broken or shorted subsequent to checkout. (3) The launch emplacement

polarity check will be revised so that complete end-to-end system continuity

and polarity will be confirmed. This will be accomplished by physically

moving the rate gyros and monitoring movement of all engines. (4) Also,

the polarity check will be run three times with a separate meter read during

each run. Previously, all three meters were read simultaneously.

Propulsion System

Thor propulsion system performance was satisfactory until vehicle breakup.

The start sequence, transition to mainstage, and mainstage operation were

normal. Abnormal engine gimbaling in the pitch plane had no detrimental

effect on engine performance or propellant supply and pressurization systems.

Main-engine cutoff was initiated by loss of the forward electrical power supply

at 59. 62 seconds. By 59.75 seconds, the main-engine chamber pressure

reached 70 percent. Since the propellant valves are held open during flight

by electrical power, loss of this power will close these valves and result in

engine cutoff.

Hydraulic System

Performance of the Thor hydraulic system was satisfactory. Although maximum engine excursions were encountered, hydraulic requirements did not

exceed the system capacity.

Electrical Power System 

Performance of the electrical system was satisfactory until the time of vehicle

breakup, when the power supply in the transition section was lost. The

2-9

LOCKHEED AIRCRAFT CORPORATION MISSILES and SPACE DIVISION
LMSC-446240-10

telemetry power supply, which is located between the propellant tanks along

with the telemetry equipment, operated satisfactorily until 79.44 seconds

(when the commutators stopped), although the telemetry carrier signal was

received until Thor impact in the ocean.

Instrumentation System 

Instrumentation system performance was satisfactory until the commutators

stopped at 79.44 seconds. Successful transmission and receipt of all flight

data were recorded up to this time, although random noise and short-duration

dropouts occurred from 36.7 to 57. 5 seconds.

2-10 OEM

LOCKHEED AIRCRAFT CORPORATION 1111111. 1111111111111 MISSILES and SPACE DIVISION
LMSC-446240.10

DISTRIBUTION

Addressee Quantity

AFSSD-TDC 10

Air Force Unit Post Office

Los Angeles 45, California

6594th Test Wing (Satellite) 6

Attn: TWRAT

Satellite Test Center

Sunnyvale, California

AFSSD Field Office

Attn: Lt. Col. W. F. Heisler

Vandenberg AFB, California

Commander 1

Pacific Missile Range

Attn: Code 3200

USN Missile Test Center

Point Mugu, California

D. McCallum 2

Douglas Aircraft Company

Space Systems (Systems Test)

3000 Ocean Park Boulevard

Santa Monica, California

Philco Corporation 1

Western Development Laboratories

Attn: Mr. Jack Keyes

3875 Fabian Way

Palo Alto, California

Headquarters

Air Force Systems Command

Andrews Air Force Base

Attn: SCRBS (Capt. Bristol)

George C. Marshall Space Flight Center 4

Attn: M-L & M-E

Mr. J. L. Starry

Huntsville, Alabama

Goddard Space Flight Center 2

Attn: Mr. R. E. Russey

C/O Anacostia Naval Air Station,

Maryland

LOCKHEED AIRCRAFT CORPORATION MISSILES and SPACE DIVISION
LMSC-446240-10

DISTRIBUTION (Continued)

Addressee Quantity 

Jet Propulsion Lab 1

Attn: Mr. C.C. Pfeiffer

Pasadena, California

Ranger Project Office (SSD) (SSVR) 1

Attn: Lt. Johnson

Air Force Unit Post Office

Los Angeles, California

LMSC Organizations 43

73

68 4276 9

LOCKHEED AIRCRAFT CORPORATION MISSILES and SPACE DIVISION