The California heat is stifling as we climb the 14-foot ladder into the passenger compartment of the C-5 Galaxy, the largest plane flown by the US Air Force. I had been told to expect a cold flight, and wore four layers of clothing. Now, sweat drips down my face. Everyone wears ear protection to drown out the engulfing noise of the four van-size jet engines hanging from the wings. A passing airman’s backpack bears a patch with the slogan “Embrace the Suck.” Good advice.

This flight is not built to suit passengers. Below, in the belly of the aircraft, sits 35 tons (32 metric tons) of equipment—an ultra-secure military communications satellite, and all the gear to transport such a spacecraft on earth. The satellite is encased in a white container custom-built to fit this aircraft. The entire cargo is valued at $1.3 billion.

“I think that may have been the most expensive cargo I’ve ever flown,” the pilot, captain Mike Zeleski, told me later.

In October, this satellite is to be placed on top of a rocket at Cape Canaveral, Florida, and launched into space, designed to become a vital cog in US national security. First, it has to get there. And that’s where the big plane comes in.

We boarded on a ladder from the tarmac at Moffett Field, California, and scampered to the rear of the aircraft along a narrow gantry between the interior wall and the satellite container, before stepping down onto the metal deck of the aircraft. There, we can appreciate the scale of the cargo bay, which stretches 19 feet (6 meters) wide and extends 121 feet (57 meters)—longer than the distance covered by Orville Wright’s first flight. You can fit six Apache helicopters in there, or, I’m told, more than 25 million ping pong balls. (Only the former has been attempted.)

A second ladder just in front of the enormous rear doors of the cargo bay takes us to elevated passenger compartment. The 12 rows of airline seats with rough blue upholstery looked 15 years old—which is excellent, since they are far roomier than the modern United Airlines seat I’ll endure on my return flight.

The other travelers are the team of Lockheed Martin employees responsible for building the satellite and transporting it to its destination, from the engineer in charge of the satellite, Kevin Au, to specially trained truck drivers, and the Air Force officers responsible for the government contract to build the satellite, led by lieutenant colonel Paul Muller. There is just one woman, Rachel Morford, an engineer who works for the nonprofit Aerospace Corporation, an independent technical adviser to the government on the contract.

Thick, knotted ropes hang in front of the hatches, helpfully labeled “Emergency Escape Rope.” In a brief safety presentation, the loadmaster says that rather than drop-down oxygen masks, the plane carries an EPOS—Emergency Passenger Oxygen System. By all appearances, these are hoods you put over your head. Per the airman, the air they supply will last about five to six minutes and, ruminatively, he observes: “Make sure, if you need to use it, to regulate your breathing.” I imagine situations where the plane depressurizes and I must don the hood. I practice regulating my breathing.

As we take off, the engine noise grows—they did not spend much time worrying about sound-proofing. The rows of seats are rear facing, and there is a sense of sliding out of your seat as the plane arcs upward. In flight, the tiny cabin, once over-heated, became chill, and I soon re-donned the layers I had stripped off. The real care is lavished on the cargo.

The size and power of the C-5 makes it finicky. The night before, as the satellite was brought aboard, airmen discovered a malfunction in the aircraft’s pressure system. With a normal payload, the plane would have flown anyway, with the cargo bay much hotter than usual. That wouldn’t do for the delicate satellite. Mechanics from Travis Air Force Base in California, where the plane is stationed, drove several hours in the middle of the night with spare parts to fix the problem.

Au turns and bumps fists with a colleague once we are clear of the runway. They have good reason to celebrate: Their satellite, after years of work, is inching closer to the finish line. It had been scheduled to launch in 2017, but a faulty component required a re-design and more delays. Now, it was good to be in the air, if not yet in orbit.

Throughout the five-hour flight to Florida, technicians periodically descend into the cargo hold to check on the satellite. I head down for an inspection tour of my own, uneasily eyeing the large bay door as I climb back down the vibrating ladder.

Behind the satellite crate, there is a long flatbed truck, covered in metal rollers, to provide ground transportation. On the truck, there are pallets loaded with crates of equipment, a fork-lift to unload them, as well as a large trailer that provides environmental control—the satellite’s own portable air conditioner. A computer displays information from sensors inside the satellite container that track temperature, humidity and vibration. The interior is filled with nitrogen pumped from dozens of tanks to create a neutral atmosphere. The cargo bay is even louder than the passenger compartment, and I scream questions directly into Au’s ear.

Space travel, it turns out, needs more than rockets: It must mobilize the biggest planes and specially designed trucks, certified pilots and drivers to operate them, meteorologists to watch out for rainstorms, technicians to watch out for turbulence, and field-grade military officers to oversee the whole operation. The next time you watch an rocket launch, remember that few minutes of fiery acceleration is just the last leg in a very long journey.

Muller entered the service as a military physicist—a real job, he assures me—and spent the beginning of his career working on nuclear detection and deterrence. For the last several years, he has worked at the Space and Missile Systems Center developing this satellite system and procuring this satellite.

It’s a good reminder that we are all gathered in this plane because of nuclear war.

Nuclear weapons catalyzed the new global economy in many ways, perhaps nowhere more so than in aerospace. Bigger, faster planes were needed to deliver nuclear weapons. Rockets, in fact, might be a better delivery method, and early ballistic missile research quickly became the foundation of the space program. The technology of Earth-imaging developed to spy on nuclear programs from above, with spy satellites eventually used to verify treaties limiting atomic weapons. Although Jimmy Carter was not interested in space, the shuttle program survived his presidency because it could put weapons-spotting satellites into orbit.

Presidents and their nuclear weapons must always be connected, according to US military doctrine. Effective deterrence requires everyone to know that the president will always be able to tell submarines in remote oceans or missile silos along the coast or bombers in the mid-air that it’s time to end the world. One way the Air Force makes this possible is with a satellite program known as AEHF—Advanced Extremely High Frequency.

It’s a not-so-catchy name for what will eventually be six satellites orbiting the world, a ultra-secure network for US forces, as well as the militaries of key American allies the UK, the Netherlands and Canada. It’s hard to understate how important this network will be to the ability of the US military to project force throughout the world, from counter-insurgency in the Middle East and hunting pirates in the Indian Ocean to surveilling North Korea’s weapons programs. The entire program costs more than $15 billion, making it one of the pricier defense acquisitions, though nowhere near as expensive as major ships and aircraft. Three satellites are already in orbit, 22,000 miles above the Earth.

The latest addition to the constellation

Space Vehicle Four, in the container below us, weighs about 9,000 lbs without fuel, and the common comparison for its size is a jumbo-size transit van. Effectively, it’s a rectangular box, with two solar arrays on opposite faces that fold out in orbit, and two panels of antennae that fold down to face Earth. The guts of the satellite were designed and built by Lockheed Martin, the enormous US defense contractor, while its communications instruments were built by Northrop Grumman, the only slightly less enormous US defense contractor. Lockheed also built the C-5 the satellite flew on.

The satellite was assembled at the company’s campus in Sunnyvale, California, nestled in Silicon Vally next to Moffett Airfield, once a key home of America’s dirigible force, now operated by Google. The Sunnyvale team operates clean rooms and runs the super-size flying robot through a battery of tests that shake it, roast it, and toast it with radio energy, all to ensure that in space, it will work without fail. It could work nowhere else: Its structures are designed for microgravity—if the solar wings extended to their full 76-foot span on Earth, they would collapse under their own weight.

AEHF spacecraft have many unique features. When special forces in the field rely on them to stay in touch, the satellites automatically hop from frequency to frequency to dodge enemy attempts to jam it. Each spacecraft is directly linked to the other satellites in the constellation, so information doesn’t need be sent down to ground systems where it can be intercepted. It promises to deliver data to users at a speed of 8 mbps, faster than the connection to my home wifi network right now.

Most importantly, and expensively, it can survive a nuclear strike. Atomic explosions release bursts of electrical energy that can fry computers, even in orbit. This satellite is hardened to pass through such energy blasts unscathed. More than that, if the satellite loses touch with its control system on the ground, it can operate autonomously, continuing to provide service to its users. It’s the kind of communications network that sends a message of deterrence just by existing, since it would (presumably) survive a nuclear first strike. Au, proud of his work, scoffed a bit at the attention received by autonomous drone and car companies. His vehicle is operating at the real technological frontier.

It is likely the satellite can do even more impressive things. I became familiar with a certain type of reaction whenever I asked officers or engineers questions about its classified capabilities—a brief burst of meaningful eye contact among the participants, a studious resetting of their facial expressions, and a promise “to get back to you on that one.”

I wasn’t able to see the satellite outside of its container. The images of the spacecraft shared in this article are tightly controlled by the US Air Force and Lockheed Martin, down to the color of the background lighting. The public-affairs officer for the AEHF satellite program at Space and Missile Command didn’t respond to multiple e-mails about the project. These images showing a satellite going into and out of its container are actually of a different Lockheed satellite (one that spots enemy missiles with infrared surveillance) because it will take a month for various bureaucrats to approve publication of similar pictures of Space Vehicle Four.

The grand unboxing

Dodging thunder storms, the plane makes its way across the country at nearly 600 miles per hour. Zeleski’s Air Mobility Command unit flies these satellite transport missions seven or eight times a year. More often, his team is moving troops or military equipment from the US to the Pacific, Europe or the Middle East. If necessary, the C-5 can make such trips without stopping or re-fueling. After Hurricane Maria devastated Puerto Rico in 2017, Zeleski was tasked to fly in a colossal generator that allowed the island to turn on its air-traffic control system again, bringing in a flood of aid by plane. He’s an instructor pilot, with some 1,800 hours in the C-5 alone. Ahead of this mission, he practiced landing extra-heavy planes to make sure he had the right feel for it.

Today, he coming down a nearly three mile-long runway at Kennedy Space Center, originally designed for shuttles winging their way back from orbit. For a passenger facing backwards, the landing too, a weird sensation, is smooth as silk. We coast gently down the runway to avoid any jarring from the brakes. As soon as we’ve taxied to the tarmac, the unloading team is already bounding down the ladder to check the satellite and begin preparing for its exit from the vehicle.

We touch down at about 8:15pm eastern time, with twilight fast approaching. Large floodlights are set up in a circle around the aircraft to prepare for the overnight unloading process. Bugs swarm them and us. Now I get to see the Lockheed team and their Air Force counterparts at work.

Perhaps 40 people are in action around the plane, many flown here in advance to meet us at landing. In contrast to the trim and youthful airmen in flight suits or fatigues, the Lockheed team tends toward the middle-aged and thick in the waist, wearing jeans, T-shirts, baseball caps and nylon-surfaced modern work boots with metal toes. They are the kind of people who carry multi-tools, who measure twice, and who operate from thick binders detailing the procedures for the work they are about to do. Many are military veterans. Before each stage of the unloading process, they huddle to talk through every step.

The concept is simple: First the back of the plane opens, and the specially designed flatbed truck drives out. The forklift takes all the crates and the mobile air-conditioner off the truck, which drives around to the front of the plane.

The back of the plane closes, and the front opens. The plane knees down so that the cargo bay floor lines up with the flatbed. The satellite then slides out like an gigantic Pez candy from a dispenser.

All of this will take hours. The overnight operation ensures that Florida’s typical summer afternoon thunderstorms won’t drench the satellite and its crew. Distant crackles of heat lightning worry the team, which is in radio contact with the weather squadron at Patrick Air Force Base. Nasty weather is at least 12 miles away and remaining there, they are told. The 45th Space Wing also provides two trucks bristling with antennae that detect nearby radio energy that might harm the satellite.

While the workers and airmen confer under the watchful eyes of a Lockheed safety official, the head of security and a pair of quality-assurance engineers who stand over a small cart loaded with binders of documentation.

The team is scheduled to depart in a convoy at 2am, which will wind out of the Kennedy Space Center to a processing facility in nearby Titusville. It will crawl at 20 mph, with cars running ahead to block intersections. At 5:30am, it will arrive, and a few hours later, they will finally take the satellite out of the box. Next up, it will undergo weeks of tests to ensure it is ready to head to space. After, the satellite will be fueled and encased in an aerodynamic nose cone built by United Launch Alliance, which builds and operates the Atlas V rocket that will carry Space Vehicle Four into orbit. (ULA is a Lockheed joint venture with Boeing.) In October, the enclosed satellite will take another overnight convoy back to Cape Canaveral, where it will be loaded on top of a rocket and launched into space.

The end is in sight

The scale of this project—just moving this thing across country required five private organizations, two different wings of the Air Force, and probably 60 people—gives context for its stratospheric cost.

It may also be a vanishing model. The paradox of these delicate military satellites is that they are mainly protected by their ultimate isolation, circling tens of thousands of miles above at nearly 7,000 mph. It’s just hard to get up there and hit them. Yet as space technology grows easier to access, their safety is increasingly in question. Anti-satellite missile systems developed by China and Russia keep military strategists up at night. They are now beginning to predict the end of mega-satellites and a move towards swarms of smaller, redundant satellites that will be harder to attack.

That may make trips like this one obsolete, but not for a decade or more—the space-industrial complex moves at the same glacial pace as the satellite container inching out of the C-5 in front of me. A handful of technicians are in the plane, pushing the container from behind (elbow grease can be as reliable as a mechanical means in a delicate situation). Outside, others check and re-check the alignment of the flatbed with flashlights and measuring tape. It’s nearly midnight by the time the satellite is fully on the truck.

Once it’s out, team leaders begin to turn in. Like giddy children on Christmas Eve, they need some rest before opening their present.