NASA Is Rolling Out its Massive Moon Rocket

Date:22 March 2022 Author: Juandre Tags:

NASA is finally rolling its hulking Space Launch System (SLS) rocket out to the launch pad.

The agency’s (equally-hulking) Crawler-Transporter 2 (CT-2) will ferry the 5.75-million-pound rocket and Orion crew capsule from the Vehicle Assembly Building (VAB) to Launch Complex 39B at 5 p.m. EDT. You can catch a livestream of the 11-hour journey in the video at the top of this story.

The rocket is traveling to the launchpad in preparation for a wet dress rehearsal—where NASA will fill it with fuel and propellant and let ’er rip—which is currently set for April 3. After the wet dress rehearsal is complete in two weeks, NASA will move the rocket back to VAB for subsequent testing and tweaking.

NASA built the SLS for the Artemis program, which will carry the next astronauts to the lunar surface in the coming years. (Each launch is expected to cost almost $2 billion.) The first leg of the Artemis mission—an uncrewed, 25-day jaunt around the moon—is scheduled to launch sometime this spring. The latest estimate, per a February press conference, suggests NASA could light this gargantuan candle as early as May 7.

Crawling Along

The rocket’s roll-out is a monumental (and long-awaited) feat, to be sure, but the real star of today’s show is the 6.5-million-pound beast that will carry it to the launchpad. For more than 50 years, NASA’s crawler-transporters have shuttled spacecraft to and from the pad.

In total, the four-mile journey will take approximately 11 hours. “We refer to that four-mile trip as the first four miles of NASA’s trip to the moon,” Mike Bolger, the Exploration Ground Systems program manager at NASA’s Kennedy Space Center, said in a February 22 media briefing.

artemis mission

Together, both crawlers, which were constructed in the 1960s, can lift more than 18 million pounds, or the weight of the St. Louis Gateway Arch. Its platform can fit an entire baseball diamond on top.

Each crawler runs on both locomotive motors and electrical power generators and has eight tread belts made up of 57 high-strength, steel-alloy “shoes,” which weigh 2,200 pounds each and help propel it forward.

The mammoth machine has a cruising speed of approximately .82 miles per hour (that speed drops to about .1 miles per hour as it leaves the VAB and approaches the launchpad). The top speed of an unloaded crawler is around two miles per hour. As you might imagine, engineers haven’t tested its top speed, fully loaded, due to the precious nature of its cargo.

I’m the Captain Now

It can be an arduous journey, Stan Shultz, a crawler driver at NASA’s Kennedy Space Center tells Popular Mechanics.

For starters, heading into a turn requires a lot of forethought—like navigating a ship through a tight channel. And, unsurprisingly, the crawler has incredibly tight tolerances. In the shuttle days, the operators had to come within 2 inches of their marks. In transporting the SLS, the distance has shrunk to an impossibly small 3/4 of an inch. “Think about that: a machine 131 feet long, and 114 feet wide, and you’ve got to position it within 3/4 of an inch,” Shultz explains. “It can’t just be close—it’s got to be exact.”

The crawler also has to maintain a level position throughout the entire duration of the journey, Shultz says. If the crawler tilts just 2 inches from its programmed position, the machine will shut down within six seconds. A dedicated engineer specifically monitors the crawler’s position to ensure it doesn’t tilt too far.

It takes a whole team to operate the crawler, in addition to the driver. “There’s a lot of work that goes on behind the scenes,” Shultz says. The crew works in shifts (drivers swap every hour), sometimes driving, sometimes acting as a leveler, sometimes monitoring the machine’s multiple systems to ensure things are operating smoothly, and sometimes walking around outside the crawler-tranporter to check the driver’s blindspots.

Track Star

The roughly four-mile crawlway is constructed with a specialized type of river rock, designed to hold up to 22 million pounds. “It’s not just anything you would get at Home Depot or Lowe’s,” Shultz says. The round cobbles are designed to crush beneath the load and disperse the weight of the vehicle as it rolls along.

To limit the amount of dust kicked up by the crawler—after all, dust is the enemy to any machine—a truck sprays water over the crawlway. And in the days following a rainstorm, Shultz says the crawlers create a sort of wake in the rocky substrate in front of them.

Shultz remembers one instance where a turtle passed in front of the crawler. Needless to say, the turtle—a speed demon by comparison—was able to move out of the way in time.

Time for an Update

CT-2 and CT-1 made their debut for the Apollo missions. In the 50 years since they were constructed, they’ve carried Apollo and Skylab launch vehicles, as well as numerous space shuttles to and from the pad. Both crawlers have undergone a broad range of updates.

In 2016, the agency modified CT-2 in preparation for its role transporting SLS, which weighs far more than anything it has transported before. To increase the carrying capacity, for instance, Shultz says the team updated the traction roller assemblies, strengthened the chassis, and outfitted the crawler’s 16 gearboxes with 592 newly manufactured ball bearings.

Over the course of its long life, CT-2 has travelled a total of 2,365 miles. Today’s journey will mark the first time the crawler has transported a launch vehicle to the pad since its 2016 update.

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