Painter and The Greek then began the task of writing their “NASA Technical Notes.” The first volume would physically describe the complete operation of the Apollo Unified S-Band Telecommunications and Tracking System, what it should do and how it should work. The second and much more ambitious document would be a complete mathematical model of the system, which could be used to compute numerical predictions of how well the system would work; it would give what are called numerical margins, above or below that needed to provide the desired performance of all the various system channels. A third volume would include a numerical tabulation of system performance, channel by channel, for all three spacecraft.
But Painter and Hondros’s plan to get everyone on the same page ran into some snags.
“The technical problems were thorny enough, but there were political problems also,” Painter said. One issue was that North American Aviation was not communicative—or forthcoming, Painter thought—about what they were doing.
“Another problem was,” Painter said, “MSC had responsibility and authority only for the Apollo spacecraft. But this system [the USB] contained ground stations. And people in Houston did not have any authority over design of the ground stations. Legally, only Goddard Space Flight Center in Maryland had that responsibility.”
But the system had to be designed as one entity. That is, both the spacecraft and ground elements of the system had to be developed together to make sure that they would be compatible with each other. And nobody in NASA had the responsibility to ensure that compatibility.
So The Greek and Painter took on the responsibility—with Graves’s backing, since he would bear the ultimate responsibility—of ensuring compatible design of all the parts of the Apollo Unified S-Band System.
Even though everyone at MSC was still scattered among the various buildings along the Gulf Freeway, Painter and Hondros became aware of how the many branches and divisions of MSC would have to work together, especially since so many different systems and components for Apollo needed to work together.
An aerial view of the Manned Spacecraft Center, in 1963 during early construction. Credit: NASA.
THE MSC ITSELF WAS COMING TOGETHER, with construction continuing on many unique facilities, some designed with the help of Henry Pohl. He had been recruited to help design the test facilities for MSC since he had been heavily involved in all the testing in Huntsville and knew there were several things he would have set up differently, given the chance. In his mind, an engineer who couldn’t properly test their theories wasn’t worth a damn; so, when he came to Houston, he was ready to assist with some of the MSC designs. The idea was to incorporate all the test facilities in Houston so they could do on-site assessments of every system and subsystem needed for human spaceflight. In the early 1960s, scientists and engineers had a limited understanding of the effects of space on hardware and humans, so, being able to replicate the environment of space as much as possible was vital.
Pohl had actually seen some of the initial plans for facilities at MSC when he visited Langley in 1961 to discuss his possible move to Houston. When he first saw the plans for how the entire MSC would be laid out, Pohl got the impression from some people at Langley that the main facilities for offices and other buildings were going to be set up like a university: If this whole going to the Moon thing didn’t pan out, Rice University could have a second campus. He also overheard conversations that some people weren’t very keen on the idea of moving to Houston because it might be career suicide. Pohl didn’t quite know what to make of it.
Once in Houston, he met with Dick Ferguson to review some of the plans for the test facilities. Pohl looked intently at the schematics for a vacuum chamber, and he recalled a time he had tested a small rocket engine at the chamber in Huntsville. He had placed the rocket too close to the floor of the chamber, and when he fired it, all the exhaust hit the floor, bounced right back up and killed all the vacuum around the engine—which meant he didn’t get the data he wanted. Plus, it burned the test stand and everything around the engine. After contemplating the issue, he fixed it by putting in a smooth deflector to channel the exhaust away from the engine.
Construction of the large Chamber A in the Space Environment Simulation Laboratory in 1964. Credit: NASA.
He saw the MSC chamber design was configured for a test stand that would allow an engine to fire right up against a wall.
“Dick, you can’t do that,” Pohl told Ferguson. “That exhaust is going to come back and hit that engine in five milliseconds, and you’re not going to get any data.”
Ferguson said, “Henry, don’t make those accusations unless you can verify them.”
“Well, that’s easy to do,” Pohl said. “It’s the square root of KGRT, with K as such and such; G and R are these values; T is such and such; and it’s the square root of that.”
Ferguson was good with figures. He took out his pencil and quickly did the math on the side of the design paper. Contemplating the numbers, he said, “Hmm, you’re right.”
“So, we went and redesigned the vacuum chamber,” Pohl said. “He just thought I was brilliant because I knew that. I never did tell him that I had been down that road, had tried and made that mistake and learned the hard way.”
Pohl continued to help with designs with the Space Environment Simulation Laboratory (SESL), which would include two vacuum chambers—one big enough to put spacecraft inside. The interior of Chamber A would be a 90-foot (27-m)-high, 55-foot (17-m)-diameter stainless-steel vessel that could simulate pressures and temperatures equivalent to 130 miles (209 km) above the Earth. The interior walls could be cooled to –280°F (–173°C) to re-create the icy conditions of space, and two banks of carbon arc lights would simulate the unfiltered light and heat from the sun. In addition, the chamber would feature a rotating floor so the objects placed inside could experience orbital and flight variants. So, except for weightlessness, NASA would be able to reproduce most of the conditions the spacecraft would encounter in Earth orbit or on flights to the Moon, with the added advantage of being able to return spacecraft and crew to Earth’s atmospheric conditions in a matter of seconds.
Chamber B was designed to be smaller—26 feet (8 m) in height and 25 feet (7.5 m) in diameter—and would be used for testing smaller systems like the spacecraft environmental control systems and spacesuits, as well as allowing astronauts to train in vacuum conditions.
While vacuum chambers—sometimes called altitude chambers—had been used for decades, previously, nothing had been designed on such a large scale to accommodate the larger Apollo spacecraft. And hardly any chambers had been built to be human-rated, meaning they had to be designed with airlocks and holding areas for rescue personnel, emergency repressurization systems, and biomonitoring and surveillance systems as safeguards for the people who would enter. The SESL would require cutting-edge technology.
James McLane Jr. was instrumental in helping design many of the test facilities for MSC. In the 1940s, he worked at Langley for the National Advisory Committee for Aeronautics (NACA), and in 1951 he moved to Tullahoma, Tennessee, to design wind tunnels and other facilities for the Army Corps of Engineers and the Air Force. He joined NASA in Houston in 1962.
Dr. Wernher von Braun stands by the five F-1 engines of the Saturn V launch vehicle, mounted on the Saturn V S-IC (first) stage. The engines measured 19 feet (5.7 m) tall by 12.5 feet (3.8 m) at the nozzle exit and burned 15 tons of liquid oxygen and kerosene each second to produce 7,500,000 pounds of thrust. Credit: NASA/Marshall Space Flight Center.
Inside the Vibration and Acoustic Facility, the Apollo Instrumentation Unit, Spacecraft/LM Adapter and Service Module-105 installed for testing. Credit: NASA.
“We started the Manned Spacecraft Center from scratch, and a cadre of people envisioned what we should have for the space program’s ground facilities,” said McLane. “A whole range of facilities were recommended. For a year or so I went from one design review to another to add my two bits as to how things might be d
one. The new facilities included a big manned centrifuge, electronics labs and the thermal vacuum lab with a couple of very big space simulation chambers to test the Apollo spacecraft and its onboard crew under conditions similar to those to be found during the lunar missions. There was just about everything you could think of that was needed to support the Apollo program.”
McLane said it was an interesting time because the public and media were intently focused on how the spacecraft and rockets were being built—and that meant he and all the engineers involved in the design of the facilities could work a little “under the radar” of the public spotlight. And that was okay in McLane’s mind. But he did feel pressure because so much of the success of Gemini and Apollo was dependent on designing and building unique, world-class test facilities.
The architectural firm of Brown and Root was brought in to draft the initial designs, and then specialty companies around the country were contracted to build the various facilities, such as Chicago Bridge and Iron to construct the large vacuum chamber vessel and a specially designed giant door.
Other facilities would put all the space-going hardware through simulated rigors of launch. Bob Wren was recruited by Max Faget and his assistant Aleck Bond to design a vibration and acoustic test facility. Wren was working for General Dynamics in Fort Worth, doing all sorts of tests—static, dynamic, vibration, acoustic—on aircraft parts and hardware.
“Most of us who worked on aircraft, we had to deal with long-range flight issues, such as cyclic flight fatigue and things like that,” said Wren, “because you want aircraft to last so many years and so many cycles of usage and life. But when we started working on rockets, we threw all that out. Rockets and spacecraft have just one shot. So now you have to look at what happens when you launch a rocket, and you have to make sure all your systems and structures can stand up to all that shaking, vibration and noise.”
Vibrations can have a powerful effect on a rocket’s avionics and hardware and any humans on board, as well as on the rocket itself. The vibrations come from the thrust of liftoff, the burning of rocket propellent during flight and the incredible speeds the rocket travels during launch—reaching more than four times the speed of sound. The vibration produced by the first-stage booster is called thrust oscillation, and these oscillations come in the form of sound waves, which can travel up and down the length of the rocket like a musical note through an organ pipe. In particular, this occurs as the fuel in the first stage depletes, leaving a long, empty “pipe.” With a certain resonance, the rocket can start vibrating during flight in such a way that it starts shaking up and down, almost like the rocket is bouncing up and down on a pogo stick (a vibration called the pogo effect). These pulses could essentially jackhammer the rocket and the astronauts—at the very least, the pogo effect can make it difficult for astronauts to read console displays or respond to any emergency. But it also has the potential to affect systems on board or catastrophically damage the rocket.
For NASA, the concern with the Saturn family of rockets was that the bigger and louder the rocket, the more destructive it could be acoustically.
“The frequency of the sound wave that the spacecraft and the crew would see is a function of the diameter of the exhaust nozzle, the bell,” Wren explained. “The bigger the nozzle, the lower the frequency, and the more destructive it can be. The bell on the F-1 engine for Saturn V is humongous, about 12 feet (3.6 m) across. What that meant was that the sound coming out of the exhaust that would radiate and come back up to the spacecraft was very, very high-level at a very low frequency.”
Even before the first Saturn rocket was built, engineers knew the acoustic environment created by such a big rocket could be an issue. Data from early Atlas launches were scaled up to get an estimate, and engineers knew the problem could be significant. Engineers also witnessed the pogo issue firsthand in March 1962, when the US Air Force tested its Titan II missile (which NASA intended to modify to launch the Gemini missions). The missile vibrated in flight for thirty seconds at an amplitude that created about 2.5 additional g-forces to the “stack”—the entire assemblage of all the rocket stages and spacecraft—and to the astronauts.
“We didn’t want anyone to experience more than 3 g’s,” Wren said. “We had to figure out what we could do with these boosters to ensure the health and safety of the crew.”
Clearly, the pogo problem would have to be solved before a Gemini and then a Saturn mission could fly.
A second source of powerful sound came when the spacecraft accelerated and went “supersonic,” going through what is called maximum dynamic pressure, in the neighborhood of 80,000 feet altitude.
“There could be a series of shockwaves that pass by the payload,” Wren explained, “and in the case of Apollo, the payload is the CSM and LM. And we also get a lot of the turbulence very similar to what might be experienced in a fighter plane cockpit, at very high amplitude in the middle frequencies.”
While it was the responsibility of von Braun, his team at the MSFC and the contractors to fix any problems with the rockets, it was Wren’s team’s challenge to simulate the experiences of lift-off and flight in order to root out any problems. They also needed to ensure that any vibrations, acoustics and g-forces in the spacecraft were kept in an acceptable range so that all the hardware could withstand the vibrational and acoustical stresses.
Simulating the rocket’s vibration was pretty straightforward and they could use off-the-shelf equipment, with shakers or hydraulic pistons to impart the forces.
“Ling Electronics, Ltd., was a big manufacturer of shaker equipment,” Wren said, “so we could use what they had already designed. Of course, we had to have instrumentation to measure the responses of the specimen we were testing. So, we had big banks of control equipment and instrumentation equipment, and if we were testing a spacecraft, we’d put an instrumented dummy on board. Then we’d hook the whole mess up and see if it would behave like it was supposed to.”
But what stymied the MSC team was the acoustics. Neither McLane nor Wren had any prior experience with designing an acoustic testing facility of the magnitude required to test a vehicle the size of the Apollo CSM, as well as the spacecraft LM adapter, a pairing that would connect the CSM to the Saturn booster and also function as the payload bay to carry the LM to space. Wren decided to approach Joe Kotanchik, an MSC structures expert. He was equally stymied. Wren then went to Faget for advice.
“Go figure it out,” is all Faget said.
“Nobody had created speaker drivers of the size and immensity of what we needed to get the kind of sound pressure levels and the frequency ranges that we needed,” Wren said. “So, we had to figure out a way to simulate all that and be sure that our spacecraft would withstand it; the structure of it, all the components and, of course, the crew.”
Wren knew he needed to “figure it out” in a hurry. He found that the top acoustics people in the country were at MIT, professors who also had set up a consulting company on the side called BBN: Bolt, Beranek and Newman.
Leo Beranek and Dick Bolt were known as the leading acoustics-engineering experts and were in the process of designing the acoustics for large concert halls in the US (and later Beranek would build the direct precursor to the Internet, the Advanced Research Projects Agency Network). Beranek’s daughter had married another acoustics expert, Ken Eldred, who was the director of research with Wyle Laboratories, also located in Boston (as well as in Huntsville, Alabama, and El Segundo, California). Beranek brought Wren and Eldred together.
Exterior view of the Vibration and Acoustic Facility, Building 49, in 1965. Credit: NASA.
“Ken saved the day,” said Wren. “He’s one of the smartest people I’ve ever had the pleasure of knowing and working with. He could do this very deep, detailed technical work, but he also had the ability to convey that to idiots like me, the laypeople, so we could understand all the equations!”
Creating the right sound for the acoustics wasn’t the only problem; they had to desi
gn a building that could withstand the sound waves and vibrations too.
“You cannot put the test article in a huge space chamber or a ‘reverberation room,’“ Wren said. “First, the walls of such a room would have to be very strong and resistive to a dynamic forcing function, as it might couple with the natural resonant response frequency of the wall and vibrate it to failure. Also, standing waves would be created inside a hard-walled chamber, and this would not apply a dynamic forcing function to the test vehicle in the appropriate manner to simulate launch and boost.”
For aesthetics, the architects of MSC wanted the exterior of any facility to be uniform in design, so the building needed to include the same exterior panels as on all the other buildings (which would also lower the costs by mass-producing the exterior panels). The panels were called pre-cast exposed aggregate facing concrete panels. So, the design for this new test facility would have to make the concrete panels work.
Eldred came up with a clever approach to solve this dilemma, helping Wren and his team design and create what is called Building 49 at MSC: the Vibration and Acoustic Test Facility, also known as the Twin Towers.
“His approach was to cloak the test article in a series of massive shrouds that completely enveloped the vehicle,” said Wren. “Massive high-intensity acoustic drivers would be positioned on top of each of these shrouds, and carefully controlled acoustic sound waves would be sent down over the vehicle from these drivers to excite the natural structural responses of the vehicle.”
The acoustic forcing functions were carefully chosen relative to frequency and amplitude to duplicate the Saturn V–generated noise at lift-off from the launchpad and the noise impingement experienced when the vehicle went through maximum dynamic pressure.
“We put it in the back of the MSC site,” Wren said, “and the design looks kind of funny when you see it because it has some low buildings and then a couple of towers.” The facility they designed had about 13,700 square feet (1,273 sq. m) in total, with space for offices and control rooms, and the two test towers were 42 feet (13 m) and 115 feet (35 m) tall.
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