NASA Office of Logic Design

NASA Office of Logic Design

A scientific study of the problems of digital engineering for space flight systems,
with a view to their practical solution.

Skylab Lessons Learned

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Lessons Learned from Skylab Officials

Skylab Lesson 1  The Cost of Change

Nothing is free.  The only issue to be addressed is the value against the cost.

Skylab Lesson 2  Plan Conservatively and Execute Boldly

The initial development program plan becomes the measure of progress.  Since research and development programs are, by definition, not completely understood, good management will provide adequate reserves in time, resources, schedule, and performance.  Once the program is underway, indecision costs time and money.

Skylab Lesson 3  Program Variables

Three items can be varied in a development program - cost, schedule, and program content.  Establish the most important factors.  Ensure that your priority matches that of your management.

Skylab Lesson 4  Program Reserve

Plan adequate reserve in resources, schedule, and performance.

Skylab Lesson 5 Program Initiation

Large development programs should not be started until a full estimate of the resources needed is available, with adequate reserves identified.   The resources must include manpower and time requirements as well as funds.   These resources must be fully committed and planned by all levels of decision prior to any large scale beginning of a project.

Skylab Lesson 6  Provide Flexibility in Planning

The late additions to program objectives can be extremely productive and may be more important than the initial detailed objectives.  Prepare the program plan to be able to accommodate good ideas which are surfaced late in the development cycle.  Be prepared to accept new ideas.  Have a sufficient financial reserve in the late years.

Skylab Lesson 7  Organization

It is important that the roles and responsibilities of the program elements be understood by all participants in the development.  For a large program with many dispersed participants, that understanding should be written and recorded.

Skylab Lesson 8  Use a Phase Approach to Development

Skylab Lesson 9  Configuration Control Procedures

The phased approach to development should be complemented by a progressively mature control of hardware design.  Initially, the hardware design is merely conceptual in nature and may be described parametrically, by equations or design parameters, for example.  At this stage, the subsystem designer should have little controls placed upon the details.  The designer should be engaged in trade studies, sensitivity analyses, and design variations which will lead to the next phase of hardware control, "base lining the system."  This base line permits concentration on a specific design and allows detail design to begin.  After a system is base lined, the designer can only change the concept when there is due cause and only after notifying other program elements to assure that each subsystem designer is aware of the design of interfacing subsystems.  At CDR (drawing release) the detail design is complete and then formal Configuration Control should be initiated.  At this time a rigid process should be established which will ensure that a design modification is only undertaken for understood cause and the full cost, and interface impact is analyzed prior to initiating the change.

Skylab Lesson 10  Update Design Requirements

Review design requirements periodically to ensure the hardware continues to reflect the real program needs.  Requirement maturity can affect not only the design, but also the test verification of design as well.

Skylab Lesson 11  Paper Review of Designs

Specific design reviews which are based upon an analysis of drawings can inadvertently overlook important features such as operational incompatibilities.

Skylab Lesson 12  Detailed Scheduling of Work

All fabrication, assembly, and checkout activities should be scheduled in detail, but rescheduled activities (sometimes called unscheduled work) should be even more carefully controlled and scheduled.

Skylab Lesson 13 Use of Common Test Procedures

When a component is to be tested at a number of locations (e.g., the development contractor's plant, the integration contractor's plant, and the launch site), decide upon a single format and approach for the conduct of the test, for control and approval of waivers or fixes, for configuration control, and for documentation in general.  Use the same basic test processes at all of the test sites.

Skylab Lesson 14 Lack of Spares

It is not always economical to provide only one flight article without a ready spare.

Skylab Lesson 15 Indicators of Schedule Status

Skylab Lesson 16 Criticality Assessment

Documentation levels, controls, and redundancies can be determined by assigning a criticality to each subsystem, experiment, or component.  A component determined to be vital for crew safety (Criticality 1) requires a complete set of documentation and controls.  Systems with this criticality are extremely costly to develop and to control since the data package generally begins with the pedigree of the raw material and carefully documents and controls each step of the development, fabrication, and test process.

Components which are required for primary mission success (Category 2) can receive somewhat less rigid treatment although in actual practice the controls on Criticality 2 hardware are almost identical with Criticality 1 components.  Items which affect secondary objectives should be placed in Category 3.  Considerable relaxation of documentation and control is possible for components such as these.  For example, qualification testing can be reduced and verification by analysis is acceptable.   Verification by similarity (i.e., use in a comparable but not identical manner) can be utilized.

Peripheral items, such as cameras, small experiments, and crew equipment of a noncritical nature should be categorized as Criticality 4.  These items require only enough documentation and controls to ensure they are safe and represent no hazard.

Skylab Lesson 17 Reduced Requirements for Experiments

Skylab Lesson 18 Subsystem Managers

Skylab Lesson 19 Use of Committees

Do not use committees for decisions.  Committees are advisors and consultants.

Skylab Lesson 20 Incentive Contracts

Incentive contracts are an effective management tool to ensure a successful development.  Award fee contracts should be considered for R&D contracts.

Skylab Lesson 21 Overruns

Skylab Lesson 22 Safety Concerns

Skylab Lesson 23 Decision Levels

Skylab Lesson 24 Disposition of Discrepancies

Skylab Lesson 25 Provide Operational Flexibility In Design

Skylab Lesson 26 Provide Excess Consumables

Design the systems on any spacecraft for a maximum of expendables and consumables.   Assure that the quantities of these expendable items exceed those necessary for the design mission by a wide margin.

Skylab Lesson 27 Stowage Flexibility

Skylab Lesson 28 Trained Observers

Skylab Lesson 29 New Manufacturing Techniques

Skylab Lesson 30 New Electronic Components

Avoid the use of new electronic techniques and components in critical subsystems unless their use is absolutely mandatory.

Skylab Lesson 31 Single Point Ground

A single point ground should be provided.

Skylab Lesson 32 Deorbit

Skylab Lesson 33 Manufacturing Aids

Skylab Lesson 34  Redundancy Design

When designing redundancies into systems, consider the use of nonidentical approaches for backup, alternate, and redundant items.

Skylab Lesson 35 Combined Environments

Skylab Lesson 36 Rapid Reaction

Skylab Lesson 37. Lesson: Crew Checklists

Crew checklists used to describe operating procedures should be complete but should be kept simple.  Backup procedures, redundant procedures, and trouble-shooting procedures should not appear on the primary checklists but, instead, should be referenced only.

Skylab Lesson 38 The Size of the Command Task

Skylab Lesson 39 Control Moment Gyros

Skylab Lesson 40 Lubrication of Rotating Machinery

If possible, positive lubrication methods should be included in the design of long-life rotating machinery, such as control moment gyros.

Skylab Lesson 41 Investigate All Failure Modes

Do not let concern and investigations of "probable" failure modes divert attention from less likely failures.

Skylab Lesson 42 Designers Should View Their Product

White room restrictions inhibit the detail designers from examining the hardware they are responsible for.  Access to assembly areas should be controlled, but not eliminated.

Skylab Lesson 43 Vent Port Location

Skylab Lesson 44 Structural Analysis Instead of Test

Skylab Lesson 45 Eliminate B-Nuts.  Braze All Fluid Lines

Skylab Lesson 46 B-Nuts

Skylab Lesson 47 Fluid Lines and Cables

Skylab Lesson 48 Stress Corrosion

Skylab Lesson 49 Sliding Aluminum Surfaces

Skylab Lesson 50 Small Orifices

Skylab Lesson 51 Use Fire Control Techniques When Designing Cables

Skylab Lesson 52 Window Design

Skylab Lesson 53 Gaseous Oxygen and Nitrogen

Skylab Lesson 54 Caution and Warning Memory

Skylab Lesson 55 Adjustable Caution and Warning Parameters

Skylab Lesson 56 Waste Management Facility

Skylab Lesson 57 Medical Requirements for Collection of Feces and Urine

Skylab Lesson 58 Software Development

Software development should receive the same attention and rigor as hardware development.  Ground software should not be an exception.  Milestones should be established and tracked with critical attention.

Skylab Lesson 59 Timing System

Skylab Lesson 60 The Need for a Teleprinter

Skylab Lesson 61 Message Identification

Skylab Lesson 62 Teleprinter Workload

Skylab Lesson 63 Two-Way Color Television Requirement

Two-way color television should be provided for all future space programs for effective data flow and communications.  The required bandwidth and power should be made available.

Skylab Lesson 64 Television Tape Recorder Requirement

Skylab Lesson 65 Television Camera Dynamic Range

Skylab Lesson 66 Spacecraft Lighting

Skylab Lesson 67 Private Communications

Skylab Lesson 68 Communications for Morale Purposes

Skylab Lesson 69 End-to-End Communications Tests

Skylab Lesson 70 Configuration of Test Articles

Skylab Lesson 71 Experiment Objectives

Skylab Lesson 72 Schedule Reviews

Skylab Lesson 73 Schedule Adjustments

Skylab Lesson 74. Crew Time

Others - coming soon!

Mr. Dale D. Myers - Associate Administrator for Manned Space Flight

Dr. Christopher C. Kraft, Jr. - Director, Johnson Space Center

Mr. Leland F. Belew - Skylab Program Manager, Marshall Space Flight Center

Lt. General Thomas Morgan (USAF) - Skylab Program Manager, Kennedy Space Center

Mr. Richard G. Smith - Deputy Director, Marshall Space Flight Center; Manager, Saturn Project

Mr. Eugene F. Kranz - Director, Flight Operations for Skylab

Dr. Walter Kapryan - Director, Launch Operations at Kennedy Space Center

Captain Charles Conrad, Jr. - Astronaut, Commander of the first manned Skylab mission

Captain Alan L. Bean - Astronaut, Commander of the second manned Skylab mission

Col. Gerald P. Carr - Astronaut, Commander of the third manned Skylab mission

Dr. Robert A. Parker - Astronaut, Program Scientist, Skylab

Mr. Kenneth P. Timmons - Manager, Martin Marietta Corporation, Skylab Multiple Docking Adapter

Mr. Raymond A. Pepping - Manager, McDonnell-Douglas Astronautics Company

Mr. Fred Sanders - Manager, McDonnell-Douglas Astronautics Company, orbital workshop project.

Mr. Haggai Cohen - Director, Reliability, Quality, and Safety for Skylab

Skylab Kleinknecht   Mr. Kenneth S. Kleinknecht - Skylab Manager, Johnson Space Center

Dr. George E. Mueller - Associate Administrator for Manned Space Flight

Skylab Disher    Mr. John H. Disher - Deputy Director, Skylab Program

Home - NASA Office of Logic Design
Last Revised: February 03, 2010
Digital Engineering Institute
Web Grunt: Richard Katz