Appendix 8

Block II vs. Block I Apollo Spacecraft;

Hardware, Changes, Tests

[From "Manned Space Flight Report: Block II Spacecraft" in House Committee on Science and Astronautics, Subcommittee on NASA Oversight, Investigation into Apollo 204 Accident: Hearings, 90th Cong., 1st sess, 3, no. 4, [sic]* May 10, 1967, 223-35.]

* should be: Hearings, 90th Cong., 1st sess, no. 3, Vol. 3, May 10, 1967, 223-35

Subsystems and Units Unchanged for Block II CSM

New Subsystems and Units in Block II CSM

Docking system
Docking tunnel and probe

Umbilical and pressurization

Rendezvous radar transponder

Sequence controllers
LM docking and separation events
S-band antennas
Flush omnidirectional

High gain

Subsystems and Units Changed in Block II CSM


Command module
Docking provisions, mechanism, and hatch

Extravehicular capability

CM/SM mechanical connection

Scientific airlock available

Service module
Propellant tanks

Empty bay

Internal rearrangement

Structural redesign

Radiator areas

RCS mounting panels


Service module propulsion system
Mixture ratio

Thrust chamber

Gimbal actuator

Service module reaction control
Propellant capacity

Monomethylhydrazine fuel

Crew support:

Environmental control system
Redundant cooling loop

Radiator design and area

Apollo suit

Extravehicular capability

Displays and controls
Panel structure

Electroluminescent lighting

Entry monitor system

Power and communication:

Electrical power system
Radiator area

Distribution bus added

Cable harnessing

Pyrotechnic initiator

Wire deadfacing at separation

Unified S-band
Primary mode for all communications


Simultaneous data and tape dump or TV

Electrical redundancy

Voice VHF
Redundant and duplex

Guidance and control:

Guidance and navigation
Digital autopilot

Computer repackaged

Electronics repackaged

Navigation base support

Stabilization and control system
Revised interface

Electronics repackaged

Redundant attitude display

Atmospheric entry and touchdown:

Redistributed ablative thickness

Truncated apex

Umbilical location

Flush antennas

Earth-landing system
Steel parachute risers

Parachute attach points


Crew Safety Systems

Mission Success Systems

Subsystems with Internal Redundancy

(Subsystem) (Major function)
CM reaction control system Attitude control

Lift vector control

SM reaction control Attitude control

S-IVB/CSM separation

CM/SM separation

Communications system Navigation data

Voice, telemetry, and tracking


Electrical power system Electrical power
Environmental control system Equipment cooling

Cabin environmental control

Sequential events control system Separation signals

Earth-landing functions

Emergency detection system Launch vehicle malfunction
Earth-landing system Atmospheric descent

Uprighting at impact

Backup System Capabilities for Earth-Orbital Flight

Subsystem Major Function Backup
Service propulsion system Deorbit SM-RCS; CM-RCS
Command module reaction control system Attitude control SM-RCS spinup before separation for ballistic reentry
Guidance and control system Attitude, translation, and lift vector control

Control of SPS burns

Stabilization and control system
Stabilization and control system Backup attitude, translation, and SPS control Manual

Flight Safety Systems Changed in Block II

  1. Earth-landing system
  2. Service module reaction control system
  3. Electrical power system
  4. Environmental control system
  5. Command module heatshield
  6. Structural system
  7. Service propulsion system

Environmental Control System Changes for Block II before AS-204 Accident

  1. New radiator design:
  2. Secondary coolant loop:
  3. Repackage environmental control unit (ECU):
  4. LM pressurization capability.
  5. Relocate postlanding ventilation valves.
  6. Redesign steam duct.
  7. Add rendezvous radar cold plates in SM.

Proposed ECS Changes for Block II after AS-204 Accident

Block I - Major Ground Test Programs

Test Article Test Purpose
CM BP-6A Parachute drop-testing of boilerplate CM Flight-qualify earth recovery system by series of aircraft drop tests
SM-001 SPS propulsion ground test Demonstrate SPS performance (oxidizer-to-fuel ratio = 2), 2nd SPS-structure compatibility
SLA Static structural test of spacecraft-LM adapter Test SLA static structural load capability (ultimate)
CSM 004 Static and thermal structural ground test CM static structural load test (ultimate)

CSM static structural load test (ultimate)

CM thermal structural load test (reentry design)

CSM 007 Varied spacecraft testing CM and SM acoustic vibration environment test

CM water-landing impact drop test

Postlanding systems operational/crew compatibility tests (uprighting, postlanding ECS, postlanding communications)

CSM 008 Thermal vacuum test of complete systems spacecraft Demonstration of structural, integrated subsystems and crew compatibility under thermal vacuum environment

White Sands Missile Range Flight Tests

Test Article Test Purpose
BP-6 Boilerplate - LES pad abort flight test Demonstrate launch escape system's pad abort performance
BP-12 Boilerplate - LES transonic abort flight test Demonstrate launch escape system's transonic abort performance
BP-23 Boilerplate - LES high-dynamic-pressure abort flight test Demonstrate launch escape system's maximum-dynamic-pressure-region abort performance
BP-23A Boilerplate - LES pad abort flight test Demonstrate launch escape system's pad abort performance with Canard, BPC, and major sequencing changes
CSM 002 Spacecraft structure - SM boost environment and LES tumbling abort flight Determine actual spacecraft SM's dynamic structural response to boost dynamic loads

Demonstrate launch escape system's tumbling abort performance and plume-impingement-load capability of CSM

Block II - Major Ground-Test Programs

Test Article Test Purpose
BP-6B Parachute drop-testing of boilerplate CM Flight-qualify earth recovery system by series of aircraft drop tests
F-2A Fixture for SPS testing Evaluate performance effects on SPS engine of fuel and oxidizer mixture's ratio change from 2.0 to 1.6
180 degree SM segment Acoustic test article (SM) testing Quality SM structure and systems to launch and boost vibration environment
CM 28-1[sic]* Static and dynamic structural testing Evaluate water impact on CM structure

Docket CM/LM interface static structural tests

CMS 2S-2 Static structural testing Static-test CM and SM structures (ultimate)
CMS 2TV-1 Complete systems spacecraft thermal vacuum testing Demonstrate structural, integrated subsystems, crew compatibility, and life support in thermal vacuum environment

*should be: CM 2S-1

Block II - Revisions of and Additions to Major Ground-Test Programs

Test Article Test Purpose
2TV-1 Complete spacecraft thermal vacuum Qualify fire related changes
004A, 007A Unified hatch qualification Functionally qualify acoustic testing, postlanding testing
CSM Acoustic vibration Demonstrate functional and structural integrity of stacked CSM-SLA
Material Materials evaluation Continue evaluation of non- or low-flammable material
Boilerplate Command module fire test Evaluate fire propagation in flight-configuration CM interior
EMU articles Extravehicular mobility unit qualification Qualify Block II unit with materials change
ECU articles Environmental control unit qualification Qualify Block II unit with all required modifications

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