PresidentJohn F. Kennedy's vision was put into motion, stretching America toward thegoal of landing man on the moon during the 1960s. A group of daring, talentedmen was specially chosen for the success of this heroic, pioneering effort. Theywere not astronauts but a team of young Grumman engineers about to embark uponan historic journey filled with technical design challenges in an extremelyhostile environment. Their goal: to protect the lives of the many crews ofastronauts that would be ferried to the moon and back.
Roserio(Ross) Bracco was selected as one of the initial group of25 engineers who would begin development of the LEM (Lunar Excursion Module) inNovember 1962 at Grumman's Bethpage, NY, facility. The contractwas completed in 1966 with 21 LEMs built-14 for flight and seven designated as LTA(LEM test article) -1 through -7.
Braccois a graduate of Cooper Union in New York and was one of the first studentsthere to receive a master's degree in mechanical engineering. When I visitedhim recently at the Cradle of Aviation Museum in Garden City, Long Island, NY, where he volunteers, he shared someincredibly interesting memories of his design journey in pursuit of a dream tohave the first man safely set foot on the moon. Most of the pictures in thisarticle were taken at the museum; it has an extraordinary display of LEMhistory, including actual, full-size LEM test articles. One is located in ahuge room simulating the lunar surface and sky, complete with stars and theearth as it looked to Neil Armstrong when he stepped onto the moon's surface.The museum also has an exhibit that chronicles the entire history of flight,including some amazing restorations and models of aircraft. It's definitelyworth a visit!
Ross Bracco at the Cradle of Aviation Museum in Garden City, NY, in front of a display that shows Neil Armstrong taking the first step on the lunar surface.
Braccowas part of the Grumman ascent-stage team in the propulsion area. The ascent stage of the Apollo LEM is the control centerand manned portion of the space vehicle. The vehicle's three main sections arethe crew compartment, midsection, and aft equipment bay and tank section. Thecrew compartment and midsection make up the cabin. The ascent-stage structureconsists of several subassemblies: the front face, cabin skin, midsection, andaft equipment bay.
Braccoshared an interesting story involving the Apollo 13 crew in a periloussituation in outer space and the heroic efforts of the Grumman designers alongwith NASA Mission Control experts to avert a lethal situation and safely returnthese men to Earth. At five and a half minutes after liftoff, astronauts Jack Swigert,Fred Haise, and James Lovell felt a little vibration. The center engine of the massiveSaturn S-II stage shut down two minutes early, causing the remaining fourengines to burn 34 seconds longer than planned. The S-IVB third stage wasforced to burn nine seconds longer to put Apollo 13 in orbit.
At 55 hours and 46 minutes,as the crew finished a 49-minute TV broadcast showing how comfortably theylived and worked in weightlessness, Lovell said, "This is the crew ofApollo 13 wishing everybody there a nice evening, and we're just about ready toclose out our inspection of Aquarius [the LEM] and get back for a pleasantevening in Odyssey [the command module]. Good night." Nine minutes later,oxygen tank number 2 blew up, causing oxygen tank number 1 to also fail. Approximately200,000 miles from Earth, the Apollo 13 command module's normal supply ofelectricity, light, and water was lost.
The message came in theform of a sharp bang and vibration. Swigert saw a warning light thataccompanied the bang and said, "Houston, we've had a problem here."Lovell came on and told the ground that it was a main B bus undervolt. The timewas 2108 hours on April 13.
Next, the warning lightsindicated the loss of two of Apollo 13's three fuel cells, which were thespacecraft's prime source of electricity. With warning lights blinking, one oxygentank appeared to be completely empty, and there were indications that theoxygen in the second tank was rapidly being depleted. The third lunar landing attempt missionwas aborted after rupture of the service module oxygen tank.
Power was a concern. Therewere 2181 ampere hours in the LEM batteries. Ground controllers carefully workedout a procedure that enabled LEM power to be used to charge the command modulebatteries.
Withthe power-producing service module damaged due to an explosion, an innovativeidea involving a roll of duct tape and a technical manual saved the crew fromcarbon-dioxide poisoning. The crew was instructed to rip out plasticized pagesof an onboard manual and get the duct tape ready so they could attach thecommand module's lithium hydroxide canisters (used to remove carbon dioxidefrom the cabin atmosphere) to the LEM environmental system using the square canistersfrom the command module. All noncritical systemswere turned off, and energy consumption was reduced to a fifth of normal.Twenty percent of the LEM electrical power was left when Aquarius wasjettisoned.
As part of an electrical closecall during the mission, one of the control-module batteries vented with suchforce that it momentarily dropped off the line. Had the battery failed, therewould be insufficient power to return the ship to Earth. Luckily, there was nofailure.
Grummanhad greatly overdesigned the LEM so that in this situation it was able to keepthe crew alive until the ship could circle around the moon in a "sling-shot"path to propel it back toward Earth for a safe entry into the atmosphere andsafe splashdown in the ocean. The Grumman designers were sure of the LEM'scapabilities. The mission was classified as a "successful failure"because of experience gained while rescuing the crew.
Anotherof many challenges early on in the LEM development in which Bracco was involvedwas the design of the tunnel and hatch in the LEM through which the astronautshad to climb to enter and exit the LEM. In a ground test, an astronaut's suitwas pressurized and he was asked to proceed through the initially designedcircular hatch. As he took small steps toward the hatch, "walking like a babywith diaper rash," according to Bracco, he could not raise his legs. "Four bigguys picked him up; he bent down toward the hatch and proceeded to fall ontohis stomach." This round tunnel did not allow adequate room for an astronautwearing a bulky spacesuit and backpack to maneuver through it safely.Ultimately, a square hatch was developed, which provided enough added room toallow the crew to successfully manage their way through the hatch.
Square-hatch design for ease of crew exit and entry
Oneparticularly interesting and challenging problem was designing the LEM landinglegs with some sort of shock absorber to gently ease the landing onto thediversely landscaped lunar surface. Conventional shocks would not function in alow-gravity, no-atmosphere environment. The members of the Grumman mechanicalteam put their heads together, and the honeycomb structure came to mind. It waslight but strong and would crumple inside the tube of the landing leg as itbore the brunt of the landing. Success!
The cantilever-type landing gear is attached externally to thedescent stage and folds inward to fit within the shroud of the Saturn Vaerodynamic shell. It consists of four sets of legs connected to outriggers thatextend from the ends of the descent-stage structural beams. Each landing gearconsists of a primary strut and foot pad, a drive-out mechanism, two secondarystruts, two down-lock mechanisms, and a truss. The struts are machined aluminumwith machined fittings mechanically attached at the ends. The foot pads consistof inner and outer layers of spun aluminum that are bonded to a honeycomb core.The formed aluminum tube probes on the foot pads are each equipped with asensing device to sense the distance to the lunar surface when within a fewfeet. The side braces are made of swaged tubing.
Thefamous first words spoken by Neil Armstrong as he descended the LEM laddertoward the lunar surface on July 16, 1969, had a dual meaning. As he jumpedonto the lunar surface Armstrong said, "That's one small step for man, onegiant leap for mankind." He jumped! This was because the LEM had landed moresoftly than expected, and the legs did not crumple as much as expected. Someexperts say that the astronauts, being jet pilots, actually landed the LEMsoftly instead of using the agreed-upon procedure to cut the engines when theLEM was within a few feet of the surface. If the expected impact force hadoccurred, the last rung of the descent ladder, attached to the landing leg,would be located close to the surface. It was not, so Armstrong had to leap tothe ground from a much higher level than planned. Luckily, the low-gravityenvironment allowed him to float gently to the surface.
Neil Armstrong’s leap to the lunar surface
Nothingdesigned for the LEM was without special consideration or significance. Designershad to account for all possibilities. Enormous G-forces at liftoff would crusha man's spinal column if he were not lying on his back. Lunar temperaturesranged from -250 to +250
oF, sometimes within inches of each other,from shadow to sunlight! Bracco was given another seemingly insignificant task:A panel to mount the hydraulic and electrical controls for the LEM thrusters inouter space needed his design expertise.
The RCS (reaction control subsystem) serves to stabilize the LEMvehicle during descent and ascent and to control the vehicle attitude about,and translation along, all axes during landing, rendezvous, and dockingmaneuvers. The RCS consists basically of 16 thrust chambers supplied by twoseparate helium-pressurized propellant-supply sections. The 100-pound thrusterscan be fired in a pulsed or continuous mode and are radiation-cooled. The thrustersand the dual propellant-supply sections make up two parallel, independentsystems. The propellants are identical to those used in the descent and ascentengines. The ascent-system propellants can be used to supply the RCS thrustersin certain operational modes.
The first challenge tobe considered in the design: The panel for these controls would be located in ahigh-vibration area due to the rocket engines. The panel also needed to belight but strong. Bracco conceived another honeycomb core design, 9/16-inch thick,sandwiched between two very thin aluminum sheets. The aluminum was welded byplacing an electrical charge on each metal piece in a gas environment, causinga strong weld like only Grumman experts knew how to do well. Bracco used hisprototype every year since that original design to level and balance hisChristmas tree, which sat on a thick living-room rug at home. The panel weighedonly 2 ounces.
Close-up of the panel that mounted the hydraulic and electrical controls for the powerful thrusters
Still another major challenge Braccoand his team faced was the fact that the LEM was expected to land on the sunnyside of the lunar surface, which meant an environmental temperature of 250
oFand a shade temperature of -250
oF. A low-cost technique was neededto insulate and protect the LEM's structural materials, including the landingfeet. The team decided to use 12 to 18 layers of Kapton or aluminized mylarmaterial sandwiched together in a 70
oF earth clean room and trap theair with a special sealing tape. This trapped air remained permanently at 70
oFand was used in many areas of the LEM, including the cupped landing feet. The"foil" around much of the LEM was made with 2- and 5-mil aluminizedKapton film.
5 LEM lander leg containing crushable honeycomb (foreground) and Kapton-covered foot (background)
The below image shows LEM abortbuttons. With great credit given to Grumman LEM-team designers, we have thisquote: "We ... the builders of the LEM are proud of the missionaccomplishments of the LEM ... and that these two buttons were never usedduring the eight voyages the astronauts took to the moon."
LEM abort buttons
We who witnessedthe first manned landing on the moon will always remember where we were when wewatched it happen on television or radio. The moon's Sea of Tranquility still holds the six historic LEM descent stages.They are a lasting Grumman legacy from the Apollo program and the technicalteams that brought the moon closer to us on Earth.
One of six LEM descent stages still on the moon—the footprints of man’s first encounter in space