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<!DOCTYPE HTML>
<HTML>
<HEAD>
<title>Chariots For Apollo, ch6-2</title>
<meta http-equiv=Content-Type content="text/html; charset=UTF-8">
</head>
<BODY BGCOLOR="#FFFFFF">
<p>
<h2>External Design</h2>
<p>
Houston and Grumman engineers had spent a month in negotiations and
technical groundwork before signing the contract on 14 January 1963.
Although ratification by NASA Headquarters was not forthcoming until
March, Grumman forged ahead, devoting most of the first three months to
establishing a practical external shape for the vehicle.<a href =
"#source1"><b>1</b></a><p>
Cooperation between customer and contractor got off to a fast start. In
late January, officials from the Houston Apollo office visited Grumman
to review early progress, to schedule periodic review meetings, and to
establish a resident office at Bethpage similar to the one already
operating in Downey. Then, following a tradition that had proved
effective in other programs, the Houston office set up spacecraft and
subsystem panels to carry out technical coordination. Thomas J. Kelly
had directed Grumman's Apollo-related studies since 1960, earning for
himself the title "father of the LEM," but the vehicle that
finally emerged was a "design by committee" that included
significant suggestions from the Houston panels, notably Owen E.
Maynard's group<a href = "#source2"><b>2</b></a>
<p align=center>
<img src = "images/c145a.jpg" width=580 height=213 ALT="LM generations">
<p>
<cite>Lunar module generations from 1962 (above left; the vehicle
originally proposed by Grumman) to 1969 (a model of the version that
landed on the moon). The second and third from the left are renderings
for 1963 and 1965.</cite>
<p>
<hr>
<p>
Using Grumman's initial proposal for the lunar module as the departure
point for continuing configuration studies and refining subsystem
requirements, the team that had guided the company through its proposal
spearheaded the design phase. When the contractor assigned 400 engineers
to this task, an optimistic air about how long it would take pervaded
both Bethpage and Houston. The job took longer than the six to nine
months originally anticipated, however, because of special efforts to
guard against meteoroids and radiation and to incorporate criteria
imposed by the unique lunar environment.
<p align=center>
<img src = "images/c145b.jpg" width=409 height=578 ALT="Webb inspects docked S/C">
<p>
<cite>NASA Administrator James Webb examines models of the lunar and
command modules in docked position.</cite>
<p>
<hr>
<p align=center>
<img src = "images/c145c.jpg" width=579 height=410 ALT="Underside of LM">
<p>
<cite>The underside of the lunar module descent stage shows fuel tank
installation.</cite>
<p>
<hr>
<p align=center>
<img src = "images/c145d.jpg" width=566 height=422 ALT="Descent stage drawing">
<p>
<cite>The drawing of the stage indicates positions of components.</cite>
<p>
<hr>
<p>
Basic elements in Grumman's proposal remained the same: the lunar module
would be a two-stage vehicle with a variable-thrust descent engine and a
fixed-thrust ascent engine; and the descent stage, with its landing
gear, would still serve as a launch pad for the second, or ascent,
stage.<a href = "#explanation1"><b>*</b></a> But almost everything else
changed. As a first step in defining the configuration, Grumman formed
two teams to study the ascent stage. One group examined a small cabin
with all equipment mounted externally, and the other studied a larger
cabin with most equipment internal. The findings of the two teams
pointed to something in between. The spacecraft that ensued was ideally
suited to its particular mission. Embodying no concessions to aesthetic
appeal, the result was ungainly looking, if not downright ugly. Because
the lunar module would fly only in space (earth orbit and lunar
vicinity), the designers could ignore the aerodynamic streamlining
demanded by earth's atmosphere and build the first true manned
spacecraft, designed solely for operating in the spatial vacuum.<a href
= "#source3"><b>3</b></a><p>
At a mid-April 1963 meeting in Houston, Grumman engineers presented
drawings of competing configurations, showing structural shapes, tankage
arrangements, and hatch locations. Grumman and Houston officials then
worked out the size and shape of the cabin, the docking points, and the
location of propellant tanks and equipment. The basic structure and
tankage arrangement was cruciform, with four propellant tanks in the
descent stage and a cylindrical cabin as the heart of the ascent stage,
which also had four propellant tanks. Still to be resolved were
questions of visibility, entrance and exit, design of the descent engine
skirt (which must not impact the surface on landing), and docking and
hatch structures.<a href = "#source4"><b>4</b></a><p>
In late April and early May, Maynard (chief of spacecraft integration in
MSC's Spacecraft Technology Division) summarized for Director Robert
Gilruth the areas still open for debate, especially the landing gear and
the position of the landing craft inside the launch vehicle adapter.
Another sticky question, he said, was the overall size of the vehicle,
which dictated the amount of propellants needed to get down to the moon
and back into orbit. The lunar module structure, especially the descent
stage, would be wrapped around the tanks; as the tanks were enlarged,
the vehicle design would have to grow to accommodate them. There was one
ray of light, however; Marshall was talking about increasing the lifting
capability of the Saturn V launch vehicle from 40,800 kilograms to
44,200. With that capability, the target weight for the lander could be
pegged at between 12,700 and 13,600 kilograms, instead of the 9,000
kilograms listed in the proposal.<a href = "#source5"><b>5</b></a><p>
One early concern, though not directly connected with external design,
was the firing of the ascent engine while it was still attached to its
launch pad, the descent stage. The exhaust blast in the confined space
of the interstage structures - called FITH for fire-in-the-hole - could
have untoward effects. Some observers feared that the shock of engine
ignition might tip the vehicle over. And what would happen if the crew
had to abort during descent, shed the descent stage, and return to lunar
orbit? This would require extra fuel, posing yet another weight problem.
Scale model tests in 1964 allayed these misgivings to some degree, but
the real proof had to wait for a firing test in flight of a full-scale
vehicle.<a href = "#source6"><b>6</b></a><p>
Although the descent structure, with its four propellant tanks, appeared
practical from the standpoint of weight and operational flexibility, the
ascent stage was harder to pin down. Nearly two years passed before the
cabin face, windows, cockpit layout, and crew station designs were
settled. By late 1963 Grumman engineers had begun to worry about the
weight and reliability of the four-tank arrangement, with its
complicated propellant system. They recommended changing to a two-tank
model, and Houston concurred. Redesign delayed the schedule ten weeks at
an added cost of $2 million, but the system was much simpler, more
reliable, and lighter by 45 kilograms. Yet the change brought its own
problems. Because oxidizer was heavier than fuel, four tanks had allowed
the engineers to put one tank of each on either side of the cabin for
balance. With only two tanks, some juggling had to be done to maintain
the proper center of gravity. The fuel tank was moved farther outboard
than the oxidizer, giving a "puffy-cheeked" or
"chipmunk" appearance to the front of the vehicle.<a href =
"#source7"><b>7</b></a><p>
Also shaping the face of the ascent stage were its windows. Windows were
basic aids for observation and manual control of the spacecraft, and the
pilots expected to use them in picking the landing site, judging when to
abort a mission, and guiding the spacecraft during rendezvous and
docking with the command module.<p>
The importance of visibility was recognized early in Houston's studies
and stressed in Grumman's original proposal. In both, large windows
afforded an expansive view. Grumman had featured a spherical cabin like
that of a helicopter, with four large windows so the crew could see
forward and downward. This design was discarded because large windows
would require extremely thick glass and a strengthening of the
surrounding structure. The environmental control system would have
trouble maintaining thermal balance. Two smaller windows could replace
the four large ones, but the field of view would have to remain very
much the same. To get the required visibility with smaller and fewer
windows, Grumman had to abandon its spherical cabin design. The new
cylindrical cabin had a basically flat forward bulkhead cut away at
various planar angles; the large, convex windows gave way to small,
flat, triangular panes (about one-tenth of the original window area)
canted downward and inward to afford the crew the fullest possible view
of the landing area.<a href = "#source8"><b>8</b></a><p>
Grumman's change to a cylindrical cabin posed another problem. A
spherical shape is simple from a manufacturing standpoint, because of
the relative ease in welding such a structure. The new window
arrangement and front face angularity made an all-welded structure
difficult. The Grumman design team wrestled with the new shape and in
May 1964 adopted a hybrid approach. Areas of critical structural loads
would be welded, but rivets would be used where welding was impractical.
Grumman neglected to inform Houston of the switch in manufacturing
processes, but a Houston engineer noticed the combination of welding and
riveting while on a visit to Bethpage.<p>
Toward the end of May, there was a series of reviews and inspections of
Grumman's manufacturing processes. NASA representatives looked at
welding criteria, mechanical fastening techniques, and the behavior of
sealant compounds under temperature extremes and a pure oxygen
atmosphere. The contractor demonstrated that its part-riveted structure
showed very low oxygen-leak rates in testing. Although Manned Spacecraft
Center officials tentatively approved the change, they left an engineer
from the MSC Structures and Mechanics Division in Bethpage to watch
Grumman closely. Marshall experts visited Grumman from time to time to
extol the virtues of an all-welded design and to warn of the problems of
mechanical fabrication. But the peculiarities of the lunar module made a
mix of the two techniques almost inevitable.<a href =
"#source9"><b>9</b></a>
<p>
<hr>
<p>
<a name = "explanation1"><b>*</b></a> The descent engine had another
possible chore: to act as a backup propulsion system if the service
module engine failed to fire on its way to the moon. No special
modification to the descent engine was required, but the docking
structure on the spacecraft had to be strengthened to withstand the
shock of the firing.
<p>
<hr>
<p>
<a name = "source1"><b>1</b>.</a> Ernest W. Brackett to Assoc. Admin.,
NASA, "Go-ahead of LEM contract," 11 Jan. 1963, annotated,
"1/11/63 3:30 p.m. - Seamans' office (Mary Turner) says Webb has
initialed 'go ahead.' Called Dave Lang and gave him the go-ahead";
James L. Neal memo, "Distribution of Contract NAS 9-1100 and
Exhibits 'A' through 'E,'" 19 March 1963, with enc., "Contract
for Project Apollo Lunar Excursion Module Development Program,"
signed 14 Jan. 1963 by Neal for MSC and E. Clinton Towl for Grumman;
Raymond L. Zavasky, recorder, minutes of MSC Senior Staff Meeting, 4
Jan. 1963, p. 5; Robert S. Mullaney, interview, Bethpage, N.Y., 2 May
1966.<p>
<a name = "source2"><b>2</b>.</a> MSC Director's briefing notes for 29
Jan. 1963 Manned Space Flight Management Council (MSFMC) Meeting; MSC,
"Consolidated Meeting Plan, Initial Issues," MSC-ASPO, 18 Feb.
1963. Much of the material on the LEM was brought to the authors'
attention by William F. Rector III, who graciously allowed us to use his
personal papers and notebooks, in which he set down day-to-day events
all during his tenure as LEM Project Officer (PO) for MSC; Mullaney
interview.<p>
<a name = "source3"><b>3</b>.</a> Saul Ferdman, interview, Bethpage, 2
May 1966; Rector to PE, "Request for study effort data," 13
March 1964; Rector to LEM Proc. Off., "Request for CCA for Study
Efforts," 6 May 1964; James L. Decker to Grumman, Attn.: Joseph G.
Gavin, Jr., "LEM Program Status," 10 July 1963; Jerry L.
Modisette to ASPO, MSC, Attn.: Robert L. O'Neal, "Report on
discussions of RCA and Grumman radiation work at Grumman, July 11
1963," 24 July 1963; Decker to Grumman, Attn.: Mullaney,
"Meteoroid Environment," 16 Oct. 1963; Apollo Mission Planning
Task Force, "Use of LEM Propulsion Systems as Backup to Service
Module Propulsion System," 27 July 1964; Milton B. Trageser to MSC,
Attn.: R. Wayne Young, "Impact of LEM Propulsion Backup to Service
Propulsion System," 16 Sept. 1964; Owen E. Maynard memo,
"Action items," 1 Dec. 1964; Dale D. Myers to Dep. Admin.,
NASA, "LM 'Lifeboat' Mode," 3 Aug. 1970, with encs.; Thomas J.
Kelly and Eric Stern, interviews, Bethpage, 3 May 1966; Mullaney
interview; Rector, interview, Redondo Beach, Calif., 27 Jan. 1970;
Kelly, "Apollo Lunar Module Mission and Development Status,"
paper presented at AIAA 4th Annual Meeting and Technical Display, AIAA
paper 67-863, Anaheim, Calif., 23–27 Oct. 1967, pp. 6-7; Stanley P.
Weiss, "Lunar Module Structural Subsystem," Apollo Experience
Report (AER), NASA Technical Note (TN) S-345 (MSC-04932), review copy,
June 1972.<p>
<a name = "source4"><b>4</b>.</a> MSC, LEM Mechanical Systems Meeting
no. 2, "LEM Configuration," 17 April 1963; Grumman,
"Vehicle Configuration Study Briefing," 17 April 1964; Grumman
Monthly Progress Report (hereafter cited as Grumman Report) no. 3,
LPR-10-6, 10 May 1963, pp. 3-4, 7-8; notes, Maynard, "Design
Approach Tentatively Agreed Upon" [ca. April 1963], with encs.<p>
<a name = "source5"><b>5</b>.</a> MSC Director's briefing notes for 30
April 1963 MSFMC meeting; Kelly to MSC, Attn.: Robert O. Piland,
"LEM Propulsion Tank Sizing," 28 Feb. 1963; Zavasky, minutes
of MSC Senior Staff Meeting, 3 May 1963, p. 4.<p>
<a name = "source6"><b>6</b>.</a> MSC Consolidated Activity Report for
Assoc. Admin., OMSF, NASA, 19 July–22 Aug. 1964, p. 23.<p>
<a name = "source7"><b>7</b>.</a> Grumman Reports nos. 10, LPR-10-26, 10
Dec. 1963, p. 16, and 11, LPR-10-27, 10 Jan. 1964, p. 1; Project Apollo
Quarterly Status Report no. 6, for period ending 31 Dec. 1963, p. 3;
Rector to Grumman, Attn.: Mullaney, "LEM Program Review," 17
Jan. 1964; Stern interview; Rector to LEM Proc. Off., "Change from
4-Tank to 2-Tank Configuration Ascent Stage," 24 March 1964.<p>
<a name = "source8"><b>8</b>.</a> Robert R. Gilruth and L[ee] N.
McMillion, "Man's Role in Apollo," paper presented at
Institute of Aerospace Sciences Man-Machine Competition Meeting, IAS
paper 62-187, Seattle, Wash., 10–11 Aug. 1962, pp. 5, 10-11; Robert W.
Abel, "Lunar Excursion Module Visibility Requirements," NASA
Program Apollo working paper No. 1115, 15 June 1964; [Grumman],
"Some Notes on the Evolution of the LEM," typescript by
unknown author, 8 Aug. 1966, p. 1; Orvis E. Pigg and Stanley P. Weiss,
"Spacecraft Structural Windows," AER TN S-377 (MSC-07074),
review copy, July 1973.<p>
<a name = "source9"><b>9</b>.</a> MSC, ASPO Weekly Management Reports,
7–14 May and 28 May–4 June 1964; Mullaney interview; Rector TWX to
Grumman, Attn.: Mullaney, 22 May 1964; LEM Contract Eng. Br. (CEB),
"Accomplishments," 11–17 June 1964; Rector to Grumman, Attn.:
Mullaney, "Manufacturing Review Meeting," 16 June 1964, and
"LEM structural design and fabrication," 22 June 1964; Joseph
F. Shea to MSFC, Attn.: Harold Landreth, "Request for meeting at
MSFC concerning joining methods for spacecraft," 23 June 1964;
Rector to Grumman, Attn.: Mullaney, "Meeting at MSFC concerning
joining methods for spacecraft," 22 June 1964; W. Richard Downs to
Chief, Structures and Mechanics Div., "Report of trip of Dr. W. R.
Downs to Marshall Space Flight Center, Huntsville, Alabama, on June 30,
1964," 8 July 1964.
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