The complexity and expense of space programs dictate fabrication and inspection test procedures that insure reliability of space vehicles and associated ground equipment.

Non-Destructive testing (testing without destroying) provides many of these procedures. Radiography is one of the most effective methods of nondestructive testing, and it is with radiography that this handbook is concerned.

The purpose of this handbook is to provide the fundamental knowledge of radiography required by quality assurance and test personnel to enable them to: ascertain that the proper test technique, or combination of techniques, is being used to assure the quality of the finished product; interpret, evaluate, and make a sound decision as to the results of any radiographic test; and recognize those areas of doubtful test results that require either retest or assistance in interpretation and evaluation.

Because of the penetration and absorption capabilities of X and gamma radiation, radiography is used to test a variety of non–metallic products and metallic products such as welds, castings, forgings, and fabrications.

Since it is capable of revealing discontinuities (variations in material composition, or density) in a variety of dissimilar materials, radiographic testing is one of the primary nondestructive test methods in use today.

Radiographic testing usually requires exposing film to X rays or gamma rays that have penetrated a specimen, processing the exposed film, and interpreting the resultant radiograph.

There are many variables in these procedures and successful completion of any test is dependent upon understanding and control of the variables. Details of the requirements for, and the variables concerned with, radiographic testing are discussed in this handbook.

Specimens tested by destructive–test methods usually become bent, twisted, notched, chipped, or broken during the testing and are worthless for further use.

Consequently, destructive testing can test only a certain portion of the articles fabricated and it must be assumed that the remainder are equal in quality to those tested.

Nondestructive testing, however, determines the quality of a specimen without destroying it, permitting testing of all articles and materials that are to be used.

Five methods of nondestructive testing are currently in common use: magnetic particle, liquid penetrant, eddy current, ultrasonic, and radiographic.

Each method has peculiar capabilities and limitations qualifying it for specific uses. In each instance of nondestructive test, it is necessary to analyze the test specimen and determine which test method will best obtain the desired results. In many instances, more than one method may be required.

The basic reason for nondestructive testing (NDT) is to assure maximum reliability of the finished product.

Since complex systems are fabricated from many articles that are readily tested by radiography, it is the task of responsible personnel to determine whether radiographic test results insure the required reliability.

To accomplish this task, standards have been set and test results must come up to these standards.

It is imperative that personnel responsible for radiographic testing be trained and highly qualified with a technical understanding of the test equipment, the item under test (specimen), and the test procedures.

Quality assurance personnel must be equally qualified. To make optimum use of radiography, NDT personnel conducting tests must continually keep abreast of new developments. There is no substitute for knowledge.

When required by appropriate documentation, every vehicle and support article must be tested using applicable nondestructive testing techniques.

The criteria is part of a building block test philosophy that dictates that each item must be tested individually before it is required to perform in subassemblies that are in turn tested individually before they are required to perform in assemblies.

Using this approach, unsatisfactory and faulty articles are discovered at the earliest possible time, resulting in high system reliability and reduced cost.

Approved procedures for radiographic testing are formulated from analysis of the test specimen, review of past history, experience on like or similar specimens, and information available concerning similar specimen defects.

It is the responsibility of personnel conducting or checking a test to insure that test procedures found to be incorrect or inadequate must be brought to the attention of responsible supervision for correction and incorporation into revised procedures.

Because radiation cannot be detected by any of the five senses, strict compliance with safety regulations is required.

Radiographic NDT processes require the use of X–ray and gamma–ray sources generating great amounts of radiation.

Radiation can cause damage to or destruction of the cells of living tissue, so it is essential that personnel are adequately protected. Radiographic test and quality assurance personnel must be continually aware of the radiation hazard and cognizant of safety regulations.

TAKE NO CHANCES.