Rocket on lift off

Building the Moon rocket

Rocket engines and fuel cells were two technologies that got a boost from the NASA Moon programme. E&T talks to the engineers who were there.

The Apollo programme was a triumph of management in meeting the enormously difficult systems engineering and technological integration requirements. James E Webb, the Nasa administrator at the height of the programme between 1961 and 1968, always contended that Apollo was much more a management exercise than anything else, and that the technological challenge, while sophisticated and impressive, was always within grasp.

Two of the key components on the momentous voyage were the rocket engines that hurled the Saturn V launch vehicle into space and brought it home safely, and the fuel cells that provided power during the long voyage.

From 1967 to 1973, there were 12 Apollo flights powered by the Saturn V launch vehicle, which contained 30 to 34 rocket engines designed, developed and manufactured by the company now known as Pratt & Whitney Rocketdyne.

Apollo 11, the first to land men on the Moon, used 30 Rocketdyne engines. Five F-1 booster engines provided 7.5 million pounds of first-stage thrust. Five J-2 engines boosted the second stage with over a million pounds of thrust. The third stage used a single J-2 engine to place Apollo 11 in Earth orbit and then, with a second burn, out of orbit on the way to the Moon. Nineteen smaller engines were used to provide propellant settling, reaction control steering, and the all important lunar ascent to rendezvous with the command capsule in Moon orbit.

A man that cut his teeth on the Apollo project 40 years ago was Bob Biggs, now a principal engineer at the company. Biggs began his career at Rocketdyne in 1957 as a performance analysis engineer on the Jupiter intermediate range ballistic missile programme. He was transferred to the F-1 programme in 1960, a year before the first engine test.

"My first assignment was to develop procedures for starting the engine," Biggs explains. "I was assigned to the F-1 engine system project office for nine years and held the positions of lead development engineer, engineering supervisor and development project engineer."

Keeping it simple

From the outset, simplicity was the major guiding principle of the F-1 design. It was originally defined as a single thrust chamber rocket engine that would burn liquid oxygen (LOX) and kerosene (RP 1), based as much as possible on proven technology.

The major challenge at the beginning of the programme was the engine's sheer size. A giant by even today's standards, the F-1 is almost 20ft long, over 12ft across and weighs over nine tonnes. The delivered thrust of 1.5 million pounds was 10 times as high as the highest thrust production engine and the chamber pressure exceeded current pressures by a factor of two.

Although the giant engine was simple, it was not developed without problems. "Its very 'bigness' created a brand new territory for technical problems," Biggs says. "Despite the similarities in functions, there was such a quantum jump in size that some things simply could not be scaled up from the earlier smaller engines."

The most significant problem was also the most expected one and yet the most difficult to resolve. Combustion technology and injector design were more art than science in the late 1950s. Stable combustion was achieved by trial and error design changes, followed by long test programmes to accumulate adequate statistical data to have confidence in the design.

Biggs picks up the story: "Early component and engine tests were plagued with instability. A vibration monitor was used to sense the onset of instability and quickly terminate the test. Referred to as a rough combustion cut-off (RCC) device, it prevented a lot of hardware damage that would have occurred if the instability were to be allowed to run its course."

Eventually, dozens of tests were terminated by the device which was renamed the combustion stability monitor at a time when management became sensitive to names that conveyed negative thoughts.

For two years, various injector changes were tested and a gradual, but steady improvement was noted. But, just as it appeared that the problem was under control, instability struck with a vengeance.

Destructive combustion

On 28 June 1962, a combustion disturbance occurred with unprecedented ferocity. The initial shock was violent enough to cause the high pressure fuel ducts to rupture and the resulting LOX-rich operation completely destroyed the engine. No safety cut-off device could have prevented the total engine loss, and before the problem was finally solved, two more engines would be lost.

Marshall Space Flight Centre and Rocketdyne formed special teams to deal with the problem. "Over the next two years, a multi-faceted approach involving both teams and combustion research consultants resulted in the development of a dynamically stable injector," Biggs says.

"It was agreed that in order for the engine to be considered 'man-rated' it must be capable of repeatedly damping out a deliberately induced instability (a bomb detonated in the combustion zone) in less than one-tenth of a second."

By the beginning of 1965, qualification tests proving dynamic stability were completed and approved by MSFC. "Although many critical changes were made it is generally thought that the most significant one was the development of a baffle installed on the face of the injector," Biggs says. "The baffle is made up of two concentric circular fences and 12 radial fence segments. They combine to divide the injector face into 13 compartments designed to 'de-tune' the various unstable frequencies. A similar baffle had been used to solve an Atlas engine instability some years before, however, attempts to 'scale-up' the design had proven unsuccessful early in the programme."

Engine testing was accomplished at Edwards Air Force Base in the Mohave Desert on six test positions in five test stands. The programme worked six days a week and, much of the time, 10 hours a day. At times of extreme pressure, which threatened the schedule, staff meetings would be held on Sunday. The large number of test positions for a single engine development programme was a measure of the very high priority assigned to the Apollo programme.

Saturn V lifts off

The first Saturn V vehicle was moved to the launch pad for a count down demonstration test (CDDT) in the autumn of 1967. "The new launch facility with its computer-driven countdown and automatic sequences had a lot of bugs to work out," Biggs continues. "Supporting the CDDT required me to spend the entire month of October at Cape Canaveral to get through a 36-hour countdown. That did not reduce my glee at being the Rocketdyne F-1 engineering representative on the launch support team for the first launch - truly the most pleasurable thing I have ever done.  

"I stood at the large window of the newly-completed firing room to watch the spectacular event. Apollo Saturn 501, bigger than the Statue of Liberty, lifted off and climbed skyward. The sound of the five F-1 engines was unbelievably awesome, even from three miles away. It sounded more violent than the Space Shuttle and contained a low frequency component that tuned in and caused a vibration of my rib cage, and even a lower frequency displacement of the large window in front of us.

"The rib-rattling sound caused the usually poised Walter Cronkite to lose his composure and he took several distinct steps backward in his mobile broadcast booth. For me, the feeling of euphoria was indescribable. A mixture of joy, pride and awe overwhelmed me. It was the high point of my 50-year career."

In time, 12 Saturn V vehicles flew, half of them placing men on the Moon. In all these flights, the F-1 engines performed flawlessly, ending its career being used to boost the Skylab space station into orbit. In 13 flights, 65 F-1 engines performed with 100 per cent flight reliability.

The first fuel cells

The development and manufacturing of the fuel cells was handled by Connecticut-based Pratt & Whitney Aircraft (PWA). Newly-qualified engineer Henry DeRonck was part of the team that developed the world's first truly operational fuel cells.

He was a green 22-year-old with, he readily admits, far more hair than he now possesses. It is hard to imagine how different the working environment he faced 40 years ago was to that enjoyed by the modern graduate engineer. "I was driving an American muscle car, everybody smoked and one of the major concerns at that time was Vietnam," DeRonck says. "Most people my age were concerned about being called into military service; the war protest movement was just starting to really gear up then.  And, of course, there was Woodstock.

"It was, indeed, exciting. However, I was a new, young engineer right out of college, so didn't really appreciate how fortunate I was. I do remember watching the Moon landing, and thinking that it was a historic event, and that I was pleased to have played a small part in it. As for pride, there was a great sense of pride among all who worked on the programme - we had done something that hadn't been done before.

"My role was very limited. I came into a group that was building the actual delivery fuel cells. After a few months of learning the ropes, I was assigned to oversee the build of one of the fuel cells that was used on Apollo 11."

The Apollo fuel cells were the world's first truly operational fuel cells. The Gemini spacecraft did have a fuel cell, but it was not fully integrated, had a very short life, and experienced problems in operation. Prior to the Apollo fuel cell, fuel cells were only laboratory curiosities and had not been engineered into a real product. 

Engineering for spaceflight

Apollo not only required a fuel cell product, but one which met the demands of the space environment (launch acceleration, zero gravity and vacuum), and was reliable and safe enough for manned space flight. "So we had to take the fuel cell from laboratory scale to a fully-qualified unit," DeRonck says. We were the world's leading manufacturer of jet engines, and applied the same processes and rigour to the fuel cell that they had developed in the jet engine business. This was not a science project, but an engineering effort to reduce science to practice."

The project faced many challenges, chief among them ensuring that the fuel cell could withstand the acceleration, vibration, and zero-gravity, with no leakage. "Developing things that seem simple now, like heat exchangers and pumps that work in launch acceleration and zero-gravity, was a challenge," DeRonck continues. "Back then, there were no such catalogue items, so we had to develop their own space-rated components. And of course the schedule was challenging."

There were numerous internal milestones in the development of the fuel cell itself. But the more visible milestones were the flight tests. The first flight of the fuel cells was in Apollo 4 (unmanned, November 1967), which validated the design of the fuel cell. This was followed by Apollo 6 in April 1968. These qualified the fuel cell for the first manned flight, Apollo 7.

DeRonck recalls no special difficulties regarding working conditions on the project. "There was a relatively large engineering and manufacturing staff, and engineers worked all three shifts," he says. "There was more a sense of urgency and importance, than any unusually difficult conditions." 

Slide rules ruled

"The Apollo project was before personal computers and electronic calculators," DeRonck says. "One recollection is the noise of the mechanical calculators clunking away in the office - it was loud. And we actually did use slide rules. I still have mine, but I'm not sure if I remember how to use it."

While there was a sense of pride and accomplishment when he watched the lunar landing, more immediate concerns were rather more mundane. "The landing meant the end of the programme was near," he recalls. "And that meant there would be staff reductions, because there was no immediate successor to the Apollo programme, so most people were concerned for their job security."

DeRonck has stayed in fuel cells for his entire career. After Apollo, he spent many years on the Space Shuttle programme.  "I developed the cell for the Shuttle fuel cell, and then led the effort to qualify the Shuttle fuel cell for service," he explains. "I participated in the initial flights of the Shuttle, and was fortunate enough to be recognised by Nasa with a Public Service Award. For several years now, I have led the Space and Defence business segment at UTC's fuel cell unit."

Most people I've talked to who worked on Apollo have been disappointed that space exploration has not progressed as quickly as was expected back then. Most assumed people would be living on Mars by now.

The reality is that the International Space Station - a remarkable achievement - is only now fully operational, 40 years after the Moon landing. I guess the 'we can do anything' spirit that typified the Apollo programme has been tempered by financial reality; no country can afford that kind of 'cost is no object' programme any more.

Maybe living on Mars is not a realistic objective, but the plans of the United States to return to the Moon will warm the hearts of the two Apollo veterans.

Recent articles

Info Message

Our sites use cookies to support some functionality, and to collect anonymous user data.

Learn more about IET cookies and how to control them