The last shuttle, Atlantis, sits on Pad 39A, ready for its valedictory flight.

It is the nature of a shuttle to look kind of lonely out there on the pad, kept at a safe remove from the control room, the hangars, the observation platforms. The pad is not far from the beach, one of the last stretches of Florida coastline unblemished by hotels and condos. Beach houses were torn down years ago when the federal government showed up with rockets. Old-timers talk of 11 graveyards and an old schoolhouse lurking somewhere out there, the remnants of the era before the coming of the spaceport.

Now the U.S. space program itself is middle-aged, facing a painful transition. Atlantis will blast off, if all goes as planned, at 11:26 a.m. Friday for a 12-day mission to the international space station. And then . . . what?

Then a lot of uncertainty. The only sure bet is that thousands of people here will be out of a job.

NASA’s critics say the human spaceflight program is in a shambles. They see arm-waving and paperwork rather than a carefully defined mission going forward. NASA has lots of plans, but it has no new rocket ready to launch, no specific destination selected, and no means in the near term to get American astronauts into space other than by buying a seat on one of Russia’s aging Soyuz spacecraft.

The space agency’s leaders say everything’s on track, that the private sector will soon launch astronauts into orbit and let NASA focus on the hard work of deep-space exploration. There is a new heavy-lift rocket in the works, one capable of going far beyond the stamping grounds of the shuttle. President Obama has picked a destination, a near-Earth asteroid, though he did not say which one.

“We have a program. We have a budget. We have bipartisan support. We have a destination,” NASA Deputy Administrator Lori Garver said. “We are just putting finer points on the rocket design.”

But Garver and other administration officials are getting heat from some of the most famous astronauts on the planet, not to mention members of Congress and aerospace industry executives. Neil Armstrong, the first man on the moon, and someone never known to be a rabble-rouser, recently co-wrote with fellow Apollo astronauts Jim Lovell and Gene Cernan an op-ed in USA Today declaring that the space policy of the Obama administration is in “substantial disarray.” The astronauts protested the decision to kill the Constellation program, the George W. Bush-era plan for a new lunar mission with new rockets and spacecraft.

Here’s Bob Crippen, who was the pilot of the first shuttle mission, STS-1, back in 1981: “I’ve never seen NASA so screwed up as it is right now. . . . They don’t know where they’re going.”

Even one of NASA’s senior people here at the Kennedy Space Center, Mike Leinbach, the launch director who will supervise the final countdown and launch of Atlantis, has blasted his agency for the lack of direction.

“We’re all victims of poor policy out of Washington, D.C. — both at the NASA level and the executive branch of the government,” Leinbach said recently at a news conference here. He said he was “embarrassed” about the lack of guidance.

NASA Administrator Charles F. Bolden Jr. said he respects Crippen and Leinbach but “could not disagree more” with their comments. “Our future is bright, and the U.S. will continue to be a world leader in space exploration for many years to come,” he said.

Garver suggested that the agency’s critics fail to recognize the dire condition of the human spaceflight program when Obama took office.

“We have brought the program back from the brink,” Garver said. “We inherited a program that was in disarray.”

And so the shuttle era comes to an end amid acrimony. To some extent, the pain and hurt and recrimination go with the territory — because, as Garver said repeatedly, “change is hard.”

But if the critics are right, the final flight of Atlantis will be a flare for a space program in trouble.

‘More left in them’

On a recent morning, NASA let reporters take a peek into the retired space shuttle Discovery, which is headed to the Smithsonian. Right now it’s in a customized hangar, or processing bay, here at the space center. Technicians are “safing” it, stripping it of explosive charges designed to blow hatches in an emergency. A shuttle won’t need those when it’s on display in a museum.

Surprise: It’s cramped inside. Seven astronauts had to pack into a modest crew compartment and, just above it, the flight deck. All the spaciousness is in the rear, in the payload bay, where the shuttle hauled jumbo telescopes and satellites and chunks of the international space station. So when people called it a “space truck,” they were not joking. It’s a pickup. A space pickup.

Discovery first flew in 1984 and has logged 148 million miles in space, which is equivalent to flying to the sun and most of the way back.

“It’s sad. There’s a lot more left in them. The airframes are certified for 100 flights. This one had 39 flights,” said senior mechanical technician Bill Powers, 58, who works for United Space Alliance, the primary contractor for the shuttle. USA already has laid off thousands of shuttle workers across the country. On July 22, the contractor will lay off about 1,900 more people here in Florida.

“It’s not wore-out. It’s just broke-in,” said Tim Keyser, lead mechanic for the orbiters. “It could fly another 20 years. We get into the guts of this thing, it’s pristine.”

The fleet was small, just five spaceships, plus a prototype, named Enterprise, that was used in low-altitude tests but never made it to orbit. Collectively they have flown 537 million miles (but, because it’s NASA, there’s an exact number: 537,114,016). Discovery, Endeavour (also parked in a processing bay here) and Atlantis are the three surviving orbiters. Two of the shuttles met disaster. Challenger blew up in 1986 as it soared into the Florida sky, and Columbia disintegrated over Texas as it returned to Earth in 2003.

The tragedies are recorded in various NASA documents with an identical, to-the-point phrase: “Loss of vehicle and crew.”

A versatile performer

The space shuttle goes into the history books with a mixed record. It was never truly loved. It was confined to low-Earth orbit — LEO — and never flew higher than 384 miles above the surface.

But in twilight, it has flowered into something attractive. It can do things that the next generation of spacecraft won’t be able to do. Bolden, the NASA administrator and former shuttle commander, speaks for many, “We are going to miss this incredible flying machine,” he said.

Versatile is the word that the engineers use. The space shuttle could not only carry 50,000 pounds of cargo into orbit; it could house seven astronauts, dock with orbiting space stations, grab satellites and telescopes and pull them into the payload bay for repairs, and haul enormous amounts of cargo back to Earth for a soft landing.

In retrospect, that was arguably too much spaceship for most of what was needed for missions in low-Earth orbit. NASA wants to get away from using a single vehicle to carry humans and cargo. It’s safer and cheaper to send cargo separately.

Cost will always tarnish the shuttle’s reputation. Once sold to Congress with promises of weekly flights for just $7 million a pop, the shuttle program never managed to make spaceflight routine or inexpensive. The shuttle program, in its totality, has cost more than a billion dollars per flight.

The historians will also note that the shuttle had a fundamental design flaw. The shuttle’s components at launch were arrayed side by side rather than stacked, as in Apollo-era rockets. The orbiter (the spaceship itself) was adjacent to a huge external fuel tank and two solid rocket boosters. That configuration meant the failure of one component could cause the failure of an adjacent one.

Which happened twice. In the Challenger accident, a jet of flame destabilized a solid rocket booster, which slammed into the fuel tank and caused a catastrophic eruption that blew apart the orbiter. In the second, foam falling during lift-off from the external tank damaged a protective tile on the leading edge of one wing of Columbia. That damage proved fatal when the orbiter disintegrated upon reentry.

After Columbia, NASA needed to make a fundamental change. President George W. Bush signed his name to the Vision for Space Exploration in 2004. The new strategy called for retiring the shuttle and using the freed-up money to go to deep space again. The new program, Constellation, featured plans for two rockets, a new crew capsule and a lunar lander. The agency vowed to put astronauts on the moon by 2020 and develop the tools and techniques for an eventual mission to Mars.

But the administration and Congress never funded the Constellation program at the level that NASA managers had envisioned. A new rocket, Ares I, ran into technical issues and fell behind schedule. By the time President Obama took office, it was clear that the United States faced a major gap, five years minimum, between the shuttle’s retirement and the availability of Ares I.

A presidential review panel led by retired aerospace executive Norman Augustine concluded that, without an extra $3 billion a year, Constellation would not be able to get astronauts to the moon until 2028 at the earliest, and there’d be no money left in the program for the lunar lander. In essence, NASA could afford only to crash astronauts into the moon. The Augustine report said NASA was “perpetuating the perilous practice of pursuing goals that do not match allocated resources.”

Big eyes, little funding.

Obama zeroed out Constellation in the president’s 2011 budget request. Under the NASA authorization act passed by Congress, Constellation is officially dead, though some major elements are still lurking, rebranded. Constellation’s crew capsule, Orion, has been retained and was given a different, clunkier name. It’s the multi-purpose crew vehicle (MPCV).

Constellation envisioned a heavy-lift vehicle known as Ares V, capable of taking astronauts to the moon. NASA is replacing that with the “Space Launch System,” a heavy-lift rocket that is supposed to be ready to fly in an initial configuration by 2016 and evolve into something larger. The agency has pondered myriad designs and is seeking final approval for its preferred architecture from the frowning officials of the Office of Management and Budget.

The shortest path to orbit for NASA is likely to come via “commercial crew,” a program advanced by the Obama administration in which private contractors, with upfront government assistance, are developing spaceships that could take astronauts to the space station by the middle of this decade. The dream is for spaceflight, at least in low-Earth orbit, to become akin to commercial aviation. Buy a ticket, blast off. For example, SpaceX’s Falcon 9 rocket, currently in a hangar on the cape just a few miles from Atlantis, could carry astronauts to orbit inside a reusable capsule named Dragon.

Here at the Kennedy Space Center, NASA managers say they plan to build a “21st-century spaceport,” but the effort has a cart-before-horse problem. NASA is trying to get infrastructure in place for rockets that haven’t been approved and destinations that haven’t been selected.

The space center has a new half-billion-dollar mobile launcher, soaring 355 feet into the air and designed for Constellation’s Ares I rocket. But with Ares I defunct, the launcher is an expensive piece of hardware searching for a purpose.

Among those most displeased with the state of NASA is former administrator Mike Griffin, who masterminded the Constellation program.

“What they did was abandon a plan for no plan,” Griffin said. “We are retiring the shuttle in favor of nothing.”

Bolden, Griffin’s successor, is pushing back against the critics. In a message to NASA employees delivered Friday morning, he wrote: “Some of my best friends died flying on the shuttle. I’m not about to let human spaceflight go away on my watch. And I’m not going to let it flounder because we pursued a path that we couldn’t sustain.”

Relics of a bygone time

One of the powerful impressions of the Kennedy Space Center is how antiquated the place has become in certain respects. It’s not digital, it’s analog. The Kennedy Space Center wants to be a 21st-century spaceport, but there are places where it looks like the Rust Belt of the Space Age.

On a recent day, an 87-year-old former NASA employee, Charlie Parker, volunteered to give a reporter a tour of the abandoned pad where the three Apollo 1 astronauts died in a fire in 1967. Pad 34, on the Air Force side of the cape, is a forlorn place surrounded by weeds and scrub. Two plaques and three stone benches honor the martyred astronauts.

Just to the north, one pad away, stood the Delta IV rocket, privately owned and operated, and primarily used for lifting military cargo into space. The massive structure housing the Delta IV is a reminder that the space program is hardly dead. The U.S. military spends more on space than NASA does. The future promises many rockets, big and small, civilian and military, public and private.

Pad 34 is the past, draped in silence, its only obvious inhabitant a lumbering gopher tortoise that dives into his burrow at the approach of visitors. Two rusting structures, flame deflectors that look like skateboard ramps, have been parked at the edge of the vacant concrete pad. In the center is a monolithic platform that once held rockets. A pillar has three words stenciled on it: Abandon In Place.

“We call this Stonehenge West,” Parker said. “It just costs too much to tear down.”