Inside Building 32 at NASA's Johnson Space Center in Houston, Texas sits Chamber A, a marvel of engineering, cleanliness, and design. It's also the closest you can come to being in space without strapping into a rocket.
Originally built in the early 1960s for the Apollo program, the chamber is one of the world's largest thermal vacuums, used to simulate the temperatures and pressure of space. It looks like a gigantic porthole to another dimension; we got to stand on the threshold, and then step inside.
Let's start with some basics, like, what's a thermal vacuum? It means that virtually all of the air can be pumped out of Chamber A, and from there the room can be heated or cooled depending on what kind of simulation is required. Occasionally NASA does "bake outs," bringing the temperature up past 94 degrees Celsius, but more often than not they're simulating the frigid cold of the universe.
To achieve that, the engineers use the chamber's "cold walls." These black walls have nitrogen and helium flowing within them, which can make things very cold indeed. 90 degrees Kelvin—a.k.a. negative 183 Celsius—is a typical testing temperature, but coldest the chamber can go is 11 degrees K (-262 C), all of which is hard to wrap your mind around. To put that in perspective, liquid nitrogen—one of the coldest substances most of us are familiar with—freezes and becomes a solid at 63 degrees K (-210 degrees C). So Chamber A can go almost 50 degrees Celsius colder than that. Yes, it's still really hard to imagine.
At the time of our visit, NASA was testing the James Webb Space Telescope, for which they took the temperature down to a balmy 20 degrees Kelvin (-253 C). For those of you not familiar, the JWST is a large telescope that will be launched into space, where it can view the universe unobstructed by the Earth's atmosphere. It's like the Hubble, except its light-gathering mirror is a full three times larger than Hubble's, and instead of being limited to viewing visible light, the JWST can gander at the infrared spectrum. This will not only give us insight into the possible origins of the universe, but give us a better chance to discovering nearby exoplanets. It's going to be amazing.
The physical structure of Chamber A is no less impressive. It's 120 feet from the very bottom to the top, much of it stuffed with the various components that make the chamber work. In terms of usable space for testing, from floor to ceiling the interior working height is 60 feet, and the interior working diameter is 55 feet. Basically six stories high and five and a half stories wide. That is one bigass chamber.
The door that seals it sounds like something out of an ancient Greek legend; it's 40 feet in diameter and it weighs a staggering 40 tonnes, yet it's hydraulically operated and perfectly balanced. Working together two people can move it by hand.
While the chamber itself is 50 years old, the cleanroom that attaches to it is brand-spanking new, and it's impressive in its own right. It was built just this year for the specific requirements of the James Webb Telescope and is meant to provide "continuity of cleanliness" in the environment from the moment the telescope arrives at the Johnson Space Center through its entry into Chamber A.
In fact materials have to be brought to a certain cleanliness level before they can even be brought into the cleanroom. This is to ensure that the cleanroom stays, well, clean. Then, once inside, the items being tested undergo a final, precision cleaning before moving into the chamber. The standard of cleanliness for both the cleanroom and the chamber is known as ISO (International Standards Organisation) Class 7, and that particle cleanliness level has to be maintained throughout operations. ISO classifications are rated according to how much particulate of specific sizes exist per cubic metre. For example, a Class 7 cleanroom can only have 2,930 five-micron particles per cubic metre.
An elaborate air filtration system helps ensure this absurd level of cleanliness by eliminating virtually all contaminants. Air is initially pumped in from the outside, and it passes through a series of very fine filters before it's pumped up to the top of the room. Once up there it passes through final, ultra-fine HEPA filters located in the ceiling just above the cleanroom, and then the clean air is allowed to drift downward. After it passes through, the air is pumped out through ducts toward the bottom of the room, at which point it goes through the whole filtering process again.
Some of the equipment that gets tested inside Chamber A is too large to fit through the main building's doors or down its long hallways. The solution? The roof in the equipment room across the hall is removable. Large items (like the Webb Telescope) are lowered into the building by crane. Once it's been cleaned to spec, it's placed onto two large rails inside the cleanroom so it can be glided directly into Chamber A. After it's inside the chamber, the rails in the cleanroom are moved off to the side so that the door can close. It's quite a process.
The reason the James Webb Telescope requires these elaborate measures is that it uses a series of incredibly sensitive optical mirrors for imaging. Those mirrors will be collecting the faintest light from various distant galaxies. "If the mirrors are contaminated with particles or other materials, then the efficiency of light collection decreases," Rajiv Kohli, NASA's Contamination Control Lead for Chamber A told us. "So you have to maintain as clean an environment as possible on the surface of the mirrors." If you don't have a cleanroom and a clean chamber then those mirrors will get covered with particles and debris during testing, and that could mean the difference between discovering a nearby habitable planet and missing it entirely.
Belly of the Beast
Before I was allowed to enter the cleanroom, I had to buff my shoes as best as I could with a machine and then walk across some large sticky pads. My camera, tripod, and microphones had to be thoroughly wiped down and blasted with air, and then placed into a small airlock. I had to put on a "bunny suit" and a hospital mask so that essentially only my eyes were exposed. Last but not least, I stepped into a small, cupboard-sized room, where more than sixty separate jets blasted me with air from all directions. I've probably never been so particle-free in my entire life.
Once I was inside and approached the entrance to the chamber, I felt very much like we weren't in Kansas anymore. The sheer size of the door is so far beyond human-scale that invokes equal feelings of awe and dread. It feels like you're standing at the threshold to a world of giants, and at any moment they might come home.
NASA allowed me to enter the chamber itself. I can't describe how incredibly puny I felt. It didn't help that the perfectly round doorway is generously polished, which, combined with the soft covers enveloping my shoes nearly caused me to face-plant as I was climbing in. Once inside I felt like I was in a high-budget sci-fi movie. I remembered hearing stories
about Jim LeBlanc, a NASA JSC technician during the Apollo years, whose suit became depressurised while vacuum testing. He blacked out within roughly 14 seconds, but before he did, he remembered that he could feel the saliva in his mouth boiling on his tongue. Can you imagine? I tried not to.
The James Webb Space Telescope will soon be undergoing its deep-space simulation in Chamber A. When we put so many of our hopes and dreams (and money) into a single piece of equipment, it's comforting to know that it's been tested, and that it can withstand the rigours of space. We'll never be able to fully relax until it's up there and operating smoothly, but it will help us breathe a little easier as we prepare to make it fly. [NASA JSC: Chamber A]
Video shot by Brent Rose, edited by Nick Stango.
Special thanks to everybody at NASA JSC for making this happen. The list of thank yous would take up pages, but for giving us access, and for being so generous with their time, we are extremely grateful to everyone there.
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