The significance of P/N and S/N on NASA items

26 May 2016

The significance of P/N and S/N on NASA items

I don't do logos, I try to keep it real. There is no "strap line" for these straps, just the authentic part and serial numbers, typed or stamped. So what do they mean? Quite a bit, as it turns out. But before diving in, some context: why the numbers to begin with?

There's a quick answer to that - superficially, the part numbers were controlling what went into the space capsule on the way out, and were itemised in the storage list (see Official collection of Apollo Stowage lists) while the serial numbers were documenting discrepancies in performance, so failed items could be improved after the astronauts returned (e.g. Apollo 11 Post-Flight Report on Suits/PLSSs/etc.).

Part numbers in detail

According to the diagram from the above, SEB12100030 means: NASA Center Designation (S) multi-assembly drawing (E) of "Crew Systems" Supplying Division (B) crew personnel equipment (12) drawing number 100030. 

The explanation is as follows:

1st Letter is always S and serves as the NASA designation.

2nd letter: Type of engineering drawing (i.e. documentation). Mandatory but open to interpretation based on supplying division. Most common seems to be catch-all "E". E= Assembly drawing (defn: assembled relationship, both separable and inseparable). Others seen include:

L= Source control (e.g. manufacture's specification)
K= Drawings in book form.
H= Wiring harness set up.

3rd Letter: Supplying Division (according to stowage lists for Apollo), e.g.
B = Crew Systems
D = Space Physics

After Apollo, this indicated Program (e.g. B=Apollo, C= Skylab, F= ASTP, D = Space Shuttle, Z= multiprogram, etc.) as defined in JSC Policy Reference (JPR) 8500.4. Initially I made the error of assuming "B" originally meant Apollo based on this document when first publishing my findings, and this was even repeated by OMEGA Watch Co. in their publicity material for their Speedmaster presentation box watch straps.


1st/2nd numbers, use. e.g. 

12 = Crew Personal Equipment
16 = Operational comms
40 = Survival

8 digit number and dash number - unique ID and sub configuration. Dash numbers -001 to -099, -101 to -199, and -201 to -299 are reserved for individual components or detailed parts on detail drawings. Other ranges have different specialist meanings.

Some examples of other part numbers:

Gemini Project
CF55032 - Longines
CF55033 - Omega
CF55034 - Rolex
Apollo Project
SEB12100039-001 Chronograph with case 105,003
SEB12100039-002 Chronograph with case 105,012 (w/ crown guard)
SLB16100920-303 Headsets 
SLB40100193-301 Pocket knife
SKB32100082-371 Lunar surface maps
SHB42100120-203 Sternum Harness
SEF33101018-305 Hasselblad camera
SED33110636-301 Carl Zeiss lens

Serial Numbers in detail

Here, I rely on Jerry Goodman's 1972 dissertation towards an MSc in Design/Development of Spacecraft & Module Crew Compartments

Serialization is an important tool for the control of crew equipment, etc., that make up the crew station. It allows identification and traceability of specific hardware items which have been used for critical fit and function checks, and formal flight crew reviews. It allows one, therefore, to be able to specify the exact item one wants from a shelf full of like items. In the integration of such items with the S/C [space craft], it is essential that records show which items were used for critical fit and function checks. Although comparable items are supposed to be interchangeable, there are times when this is not so. At times, there are peculiarities between mating items which account for some electrical connectors mating readily, while items of identical part number mate with difficulty. In addition, the characteristics of items such as batteries, flow valves, portable life support systems, etc., vary enough among items to merit a detailed performance record. In the case of the Extravehicular Mobility Unit (Space Suit Assembly) used on the lunar surface, such data are known, published, and used during actual missions. Serial numbers are included in the data for the Flight Readiness Review and other S/C reviews. Before flight of the first manned Apollo CM, it was discovered the contractor had no plans for serialization of crew station items. Serialization was then imposed by contractual direction, and proved essential for crew station monitoring and control. At times, critical orientation or alignment calls for marks to be made when items are mated and aligned. In such cases, the specific hardware used may be the only hardware where such correct, verified alignment could be duplicated. The records, in such cases, specify the serial numbers of the items used. Serialization also aids in evaluating the history of problems with any item. The history of each is documented and accompanies the item through testing, preflight inspection, etc.

I should add that I never use a serial number from genuine NASA artifacts that I can see from auction catalogues or NASA image archives.

Concluding remarks

P/N and S/N and even an audited design document SEB12100030 might seem an awful lot of bureaucracy for a humble watchband, but in my experience in regulated industries, it is often (always?) easier to not elect items for quality exceptions, and then be obliged to go through a risk assessment to support that decision. Indeed, the Apollo program in general gave the world management processes to handle very complex and difficult undertakings safely, which is arguably one of the moon landing's greatest legacies.

In terms of numbers of dollars or of men, NASA has not been our largest national undertaking, but in terms of complexity, rate of growth, and technological sophistication it has been unique... It may turn out that [the space program's] most valuable spin-off of all will be human rather than technological: better knowledge of how to plan, coordinate, and monitor the multitudinous and varied activities of the organizations required to accomplish great social undertakings. 

Dael Wolfe, Executive Officer, American Association for the Advancement of Science, editorial for Science, 15 November 1968 copied from Project Apollo: A Retrospective Analysis § The Program Management Concept.