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| Apollo 14 command-service module ("spacecraft") with attached adapter ("SLA") being hoisted atop the Staurn V launch vehicle. |
Among the many misnomers I hope to discuss in this blog, my nominee for
“longest period of lip-service without further consideration” is the Apollo
Program’s “Spacecraft-Lunar Module Adapter”, or “SLA” (pronounced “slaw”)[1].
The SLA was the 8.5-m long funnel-shaped structure between the bottom
of the 3.9-m diameter Service Module (SM) and the top of the 6.6-m diameter S-IVB
final stage of the Saturn IB or Saturn V rocket[2].
It started out serving a simple purpose: providing a rigid connection between
the SM and the S-IVB while smoothing the supersonic airflow past them during
launch.
Any device which joins two disparate items, whether in plumbing,
manufacturing or even electronics, is called an “adapter”, so that part of the
name is obvious. In 1962, when the Apollo Program came to include a separate
vehicle for landing on the Moon[3],
the Lunar Excursion Module (LEM), later shortened to Lunar Module (LM), it
became convenient to stow the lander in the adapter for launch. But here is
where the misnomer appeared, in two ways.
First, the LEM was a spacecraft, too, just as surely as the unified Command/Service
Module (CSM) which was the “spacecraft” in “spacecraft-lunar module adapter”. However,
the CSM was designed first, and the LEM was added later, so for a time the CSAM
alone was the Apollo “spacecraft”.
Second, the adapter “adapts” between the spacecraft and the launch
vehicle, and the LM was simply a Johnny-come-lately passenger hitching a ride
in the volume resulting from that structural necessity. Therefore, logically,
SLA should stand for “spacecraft-launch vehicle adapter”.
A representative but not exhaustive search of official documentation[4]
and press reporting[5] of
Apollo developments indicates, surprisingly, that “spacecraft-launch vehicle
adapter” was not the term of choice even before the LM appeared, nor was “spacecraft-lunar
module adapter” the immediately preferred term thereafter. A 1961 document[6]
from the Marshall Space Flight Center (MSFC), which designed the Saturn rocket
family, didn’t even refer to the adapter by name, calling it the “Instrument
Unit”, which was contained in an adjoining piece of the Saturn structure. Other
documents in 1961 to 1963 called it just the “adapter” or “spacecraft adapter”.
A change in the approach to lunar landing led to the appearance of the LEM in
1962, so by June 1963, the adapter was called the “S-IVB adapter”, “S-IVB (LEM)
adapter” and even the “LEM adapter” within the same NASA documents. In 1964 the
press was calling it the “LEM adapter section” and the “Apollo spacecraft
adapter” while the NASA documents were referring to it as the “Apollo adapter”,
the “Spacecraft S-IVB Adapter” and the “CSM/S-IVB Adapter”. The latter two
terms at least had the characteristic of accuracy because they indicated which
two components were being adapted.
At the end of 1964, a NASA document referred to the “spacecraft-launch
vehicle adapter” and used the abbreviation “SLA” for the first time in print;
however, the same document also labeled it the “LEM adapter” in an illustration.
In November 1965, a trade journal mentioned the delivery of the first
manufactured “Apollo spacecraft/lunar excursion module adapter” and “spacecraft/LEM
adapter”. In 1966 the “spacecraft/lunar module adapter” appeared in a NASA
press release, while a NASA briefer labeled it as the “Service Module Adapter”—complete
with a unique abbreviation, “SMA”, for the first and last time—as well as “SLA”
with no expansion. “LM adapter” appeared in a 1967 NASA illustration and “launch
vehicle/spacecraft adapter” in a 1968 official report, but by 1969 the familiar
“spacecraft-LM adapter” seemed to be dominating[7]. Except
for a 1970 contractor document that inexplicably substituted the launch vehicle
for the spacecraft, identifying the “Saturn Lunar Adapter” and the “Saturn
Lunar Module Adapter”, the now-familiar “spacecraft-lunar module adapter” term
has persisted[8].
Other terms in the space lexicon represent similar mindless reptition—here
I’m thinking of “crew” to indicate both an individual astronaut and a group of
them, and “microgravity” when “weightlessness” is just as appropriate and not
guilty of excessive precision—but those are better left to another day and
diatribe.
References
[1] Oral
History Transcript, J. Thomas Markley, interviewed by Carol L. Butler,
Plymouth, MA, 24 June 1999, for the Johnson Space Center Oral History Project,
p. 12-13.
[2] Apollo
(spacecraft), http://en.wikipedia.org/wiki/Apollo_%28spacecraft%29
(last checked 11 June 2012).
[3] Apollo lunar module, http://en.wikipedia.org/wiki/Lunar_Module (last checked 12 June 2012).
[4]
NASA Technical Reports Server, http://ntrs.nasa.gov,
a free repository of NASA and related documentation.
[5]
Newspaper Archive, http://newspaperarchive.com,
an invaluable subscription-based source for decades of U.S. and foreign
newspaper articles.
[6] THE
APOLLO "A"/SATURN C-I LAUNCH VEHICLE SYSTEM, MPR-M-SAT-61-5, July 17,
1961 (NASA-TM-X-69174), pp. 130-134ff incl. fig. 6.1 and 6.2. http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730064291_1973064291.pdf
(last checked 4 June 2012).
[7] Williamson,
M.L. and C.W. Fraley, APOLLO 9 SLA PANEL
JETTISON SEPARATION AND RECONTACT ANALYSIS, MSC INTERNAL NOTE NO. 69-FM-43, http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740072593_1974072593.pdf
(last checked 3 June 2012).
[8]
Duncan, John. “Spacecraft-LM Adapter”, http://www.apollosaturn.com/asnr/SLA.htm
(last checked 3 June 2012).
