June 16, 2024
1 Solar System Way, Planet Earth, USA
Discovery

On the Shoulders of Atlas: Remembering the Apes, the Men, and the Failures of Project Mercury's Orbital Drive (Part 1)

Spectacular views of the December 2019 launch of an Atlas V with Starliner's first uncrewed orbital flight test (OFT-1). Photo credit: Mike Killian/AmericaSpace.com

As United Launch Alliance (ULA) counts down to a revised No Before (NET) target of 4:43 pm EDT on Tuesday, May 21 For the long-awaited Crew Flight Test (CFT) of Boeing's CST-100 Starliner, NASA veterans Barry “Butch” Wilmore and Suni Williams are set to become the first humans to launch atop a Mighty Atlas rocket from the astronaut Gordon “Original Seven” Mercury. copper flew its day-long Faith 7 mission in May 1963. After launch from the historic Space Launch Complex (SLC)-41 of Cape Canaveral Space Force StationWilmore and Williams will spend at least eight days “docked” aboard the International Space Station (ISS) performing a series of flight test objectives before returning to a parachute- and airbag-assisted landing in the southwestern United States.

Flanked by fellow NASA astronauts Mike Fincke and Jessica Wittner, CFT Commander Barry “Butch” Wilmore expresses his well wishes at the Kennedy Space Center (KSC) on April 25. Photo credit: Jeff Seibert/AmericaSpace

Becoming the first people to travel on an Atlas rocket in more than six decades, Wilmore and Williams will add their names alongside Project Mercury luminaries John Glenn, Scott Carpenter, Wally Schirra and Gordon Cooper. And except for a slight twist of fate, two others, fellow “Original Seven” veterans Deke Slayton and Al Shepard, also came tantalizingly close to flying an Atlas.

Unsurprisingly, the Atlas-D of the Project Mercury era was a far cry from today's gargantuan Atlas V. With a height of 28.7 meters (94.3 feet), the rocket that lifted Glenn, Carpenter, Schirra and Cooper had a mass of 120,000 kilograms (260,000 pounds) and a liftoff thrust of just over 163,000 kilograms (360,000). pounds). Compare that to the current Atlas V, with its Common Core Booster (CCB), dual-engine Centaur upper stage (DEC), and a pair of Aerojet Rocketdyne-equipped AJ-60 solid-fuel boosters, and an entirely different beast emerges: a beast that measures 52.4 meters (172 feet) tall, weighs 590,000 kilograms (1.3 million pounds) and rises from the Earth under a thrust of 725,750 kilograms (1.5 million pounds).

CFT pilot Suni Williams will make her third space flight. Photo credit: Jeff Seibert/AmericaSpace

Atlas originated in 1946 as an Air Force-led concept for America's first intercontinental ballistic missile (ICBM) and initial studies were awarded to Convair Corp. of San Diego, California, leading to Project MX-774, described as “a sort of Americanized version of Nazi Germany's infamous V-2 missile. Its novel design would control the rocket by rotating its motors, using hydraulic actuators that responded to commands issued by gyroscopes and an autopilot function.

Put on the back burner for a few years by President Harry S. Truman, the ICBM effort earned the nickname “Atlas” in 1951, and by mid-decade Convair was deeply entrenched in the details of the new missile. Its structure (nicknamed the “gas bag”) used paper-thin stainless steel sections stiffened by pressurization with helium.

The long-awaited Crew Flight Test (CFT) must wait until at least Friday, May 17 for launch, following Monday's thwarted attempt. Photo credit: Jeff Seibert/AmericaSpace

The result was a sharp reduction in the Atlas's airframe-to-weight ratio: its “empty” weight was less than two percent of the propellant weight, and yet the airframe as a whole was still capable of withstand extreme aerodynamic loads. Meanwhile, North American Aviation's Rocketdyne Division developed a three-engine design for the missile, with two boosters and a “sustainer,” along with small verniers.

In its Project Mercury incarnation, the Atlas-D, the rocket structure benefited from a thicker, stronger skin and employed radio-inertial guidance systems to detect aerodynamic forces and calculate and adjust its positioning, speed and direction. And in December 1958, the Space Task Group (STG) at NASA's Langley Research Center (LaRC) in Hampton, Virginia, formally selected Atlas as its preferred launch vehicle for Project Mercury's manned orbital missions and commissioned nine flight units.

Video credit: Retro Space HD, via NASA/YouTube

Its inaugural suborbital flight with an attached unmanned Mercury capsule, known as Mercury-Atlas (MA)-1, lifted off from Launch Complex 14 at Cape Canaveral at 9:13 a.m. EST on July 29, 1960. The first part of the Ascent took place without incident. But one minute after takeoff, the pressure difference between the rocket's liquid oxygen and fuel tanks suddenly reached zero and contact was lost.

That morning the cloud cover over the Cape was so thick that visual and photographic evidence was almost impossible, but telemetry data indicated that the walls of the Atlas had ruptured due to vibrations caused by mechanical resonance in the adapter connecting the rocket and the Mercury capsule. The pile reached an altitude of 13 kilometers (8.1 mi) before descending to impact the Atlantic Ocean; Remarkably, the Mercury capsule maintained its structural integrity and was recovered (albeit crumpled) from the water.

The ill-fated MA-1 takes off on July 29, 1960. Photo credit: NASA

A stainless steel reinforcing “abdominal band” was implemented and the adapter was hardened as part of the corrective steps and MA-2 was launched at 9:12 a.m. EST on February 21, 1961. It climbed to 114 miles ( 183 kilometers), after which the unmanned Mercury capsule separated and performed a ballistic reentry and splashdown in the Atlantic Ocean.

Nine weeks later, at 11:15 a.m. EST on April 25, 1961, MA-3 rose from Earth carrying an electronic mannequin capable of “inhaling” and “exhaling” human-like amounts of gas, heat, and steam. of water. But the Atlas suffered a transient voltage problem during climb, which caused it to not properly execute the maneuvers in the pitch and roll program.

Video credit: Retro Space HD, via NASA/YouTube

“The roll and pitch program typically changed the launch's initial vertical trajectory to a more horizontal one that would take Atlas over the Atlantic,” legendary NASA flight director Gene Kranz wrote in his memoirs. Failure is not an option. “The Atlas continued to inexplicably fly upward, threatening the Cape and surrounding communities.” The range safety officer remotely destroyed the booster 43 seconds after takeoff, but surprisingly the MA-3 capsule survived and fell into the Atlantic Ocean in such good condition that it was reused for the next mission, MA-4.

In preparation for MA-4, the flight-tested capsule was meticulously cleaned and repaired and its heat shield replaced. At 9:04 a.m. EST on September 13, Atlas launched MA-4 into orbit and succeeded where its predecessor had so miserably failed.

Powered by the “reused” Mercury capsule from the April 1961 MA-3 mission, MA-4 blasts off from Launch Complex 14 at Cape Canaveral on September 13, 1961. Photo credit: NASA

And on November 29, the chimpanzee Enos was launched into orbit aboard MA-5 to evaluate the Mercury capsule's life support systems and the Atlas' own performance with a live passenger on board. Enos, who took her name from the Hebrew word for “man,” had received 1,250 hours of training, including psychomotor preparations and flights in satellite dishes, to prepare him for her mission. Speaking shortly after takeoff, President John F. Kennedy drew laughter from the Senate when he announced that the newly launched Enos “reports that everything is perfect and working well.”

Atlas successfully placed MA-5 and Enos into a precise orbit with an apogee of 237 kilometers (147 miles) and a perigee of 159 kilometers (98.8 miles). Originally intended to complete three Earth orbits (the same as those planned for astronaut John Glenn on MA-6, the first manned Atlas mission), MA-5 experienced problems with its attitude control system and forced controllers from flight to interrupting the flight afterwards. two orbits.

The chimpanzee Enos, the first living passenger of the Mighty Atlas, is prepared for launch on November 29, 1961 on MA-5. Photo credit: NASA

However, Enos' flight was far from trouble-free, with the beleaguered chimpanzee weathering failures in his ship's environmental control system and the temperature of his pressure suit rising to an uncomfortable 38.1 degrees Celsius (100.6 degrees Fahnreheit). Failures in the onboard equipment also meant that poor Enos was “rewarded” for operating the correct controls not with banana pellets, but with electric shocks…

Bloodied and described as “excitable” when he was rescued, Enos' flight soon faded as NASA prepared to launch Glenn on December 19 on the first manned Atlas mission. Unfortunately, a series of technical problems involving the MA-6 capsule delayed its launch until January 1962 at the earliest.

Video credit: The Federal File/YouTube

But problems persisted and few were under any illusions that Glenn's flight would be trouble-free. “John Glenn is going to move forward that Gadget?” commented famous rocket engineer Wernher von Braun. “You should get a medal just for sitting on it before taking off!”

Tomorrow the second part of this three-piece story will appear.

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