CAPE CANAVERAL, Fla. — The U.S. Space Force's mysterious X-37B space plane successfully launched on its sixth mystery mission from Florida today (May 17).

Riding atop a United Launch Alliance Atlas V rocket, the clandestine craft blasted off from Space Launch Complex 41 at Cape Canaveral Air Force Station here at 9:14 a.m. EDT (1314 GMT).

The on-time liftoff occurred just 24-hours after poor weather conditions at the Florida launch site forced ULA to scrub its original launch attempt, Saturday morning.

While the X-37B's exact purpose is a secret, Space Force officials have revealed that the craft is packing numerous experiments on this trip to test out different systems in space. Some of those experiments include a small satellite called FalconSat-8, two NASA payloads designed to study the effects of radiation on different materials as well as seeds to grow food, and a power-beaming experiment using microwave energy.

Related: The X-37B space plane: 6 surprising facts

The U.S.Space Force and Air Force Rapid Response Capabilities Office have two of the miniature shuttle-like X-37B space planes (also known as Orbital Test Vehicles, or OTVs) that it uses for classified military missions in low-Earth orbit. They have flown five missions since 2010, four of them on ULA Atlas V rockets and the fifth on a SpaceX Falcon 9.

X-37B returns to space

Today's launch occurred just six months after the most recent mission, OTV-5, landed at NASA’s Kennedy Space Center in Florida on Oct. 2, 2019, completing a record-setting 780 days (just over two years) sojourn in space.

Boeing built the X-37B space planes for the U.S. Air Force. The two vehicles have spent more than seven years in orbit across their missions. (Command of the mission and other space related activities transferred to the Space Force after its creation in 2019.)

Space Force officials have said that the experiments and technology the X-37B carries "enables the U.S. to more efficiently and effectively develop space capabilities necessary to maintain superiority in the space domain."

Related: How the secretive X-37B space plane works (infographic)

The X-37B space plane ahead is seen tucked inside the payload fairing of its Atlas V rocket ahead of a May 17, 2020 launch. (Image credit: Boeing/US Space Force)To that end, this mission will have even more experiments than previous flights. That's thanks to the addition of a new service module — a cylindrical extension attached to the bottom of the craft — a first for this mission. The addition of a service module will help to increase the vehicle's capabilities, enabling it to conduct more experiments and test new technologies throughout the mission, Space Force officials have said.

ULA launched the X-37B on an Atlas V rocket in the 501 configuration, which means the vehicle has a 17-foot (5 meters) wide payload fairing, a single engine Centaur upper stage, and no solid rocket boosters.

It marked the 84th flight of the Atlas V, which was recently dethroned as the most flown American launcher. That superlative was snagged by SpaceX's Falcon 9 rocket, which became the world's most flown booster in April and is also set to launch its next flight (a Starlink satellite fleet launch) early Tuesday, May 19.

Honoring coronavirus responders

The U.S. Space Force and United Launch Alliance dedicated the X-37B space plane's OTV_6 launch to the first-responders and victims of the COVID-19 pandemic. (Image credit: United Launch Alliance)Saturday's launch, dubbed USSF-7, is dedicated to the first responders and medical personnel across the country who work daily to combat the ongoing coronavirus pandemic.

The mission is part of the military's "America Strong" campaign, which also includes a series of flyovers by the Air Force Thunderbirds and Navy Blue Angels. ULA also stamped a tribute on the side of the Atlas V rocket that says: "In memory of COVID-19 victims and tribute to all first responders and front-line workers."

COVID-19, the disease caused by the new coronavirus, has infected approximately 4.5 million people globally, with 1.45 million of them in the United States. At least 87,991 have died from the disease in the U.S. as of May 16, according to Livescience.

"Thank you for your courage in caring for the sick and keeping us safe," ULA CEO Tory Bruno tweeted, addressing the many first responders working selflessly to support the nation in this difficult time.

"There are still heroes in this world," he added.

Officials at the 45th Space Wing said they have been doing their part to make sure the launch went smoothly while simultaneously protecting its workforce.

"We have an obligation to keep space capabilities up and running for our nation," Gen. John Raymond, chief of space operations in the U.S. Space Force and commander of the U.S. Space Command said during a prelaunch talk on May 6.

To that end, the 45th Space Wing has been rotating crews between launches, reduced on-site staff as much as possible and practiced social distancing. Both NASA's Kennedy Space Center and the nearby Cape Canaveral Air Force Station have kept public viewing areas closed for this launch as well as a SpaceX launch scheduled for Sunday morning.

This mission marks the second national security launch under the Space Force since its establishment in December. (The first was the AEHF-6 military communications satellite launch in March.)

The X-37B space plane is about 29 feet (8.8 meters) long and resembles a miniature space shuttle. For OTV_6, the robotic spacecraft carried a new service module that supports more experiments and longer stays in space. (Image credit: U.S. Air Force)Space Force officials have chosen to delay some of the planned missions, however, due to concerns about the pandemic. For instance, the next GPS navigation satellite mission GPS 3 SV03 has been delayed several months to no earlier than June 30 to ensure that ground control crews were able to stay safe.

It's a busy time on the space coast, and the GPS constellation is healthy which reduces the pressure to get newer, upgraded satellites into orbit, officials said.

Today's mission was originally part of a launch double header from Florida's Space Coast.

Following the Atlas V launch, a SpaceX Falcon 9 rocket was supposed to take to the skies less than 24 hours later, carrying another batch of SpaceX's Starlink satellites into orbit.

That launch was originally on the books for today, but weather delays at the launch site and the emergence of a tropical depression out in the Atlantic prompted SpaceX to move the launch date.

When the Falcon 9 does launch, it will bring the total number of Starlink internet satellites up to nearly 500. SpaceX CEO Elon Musk has said that between 400-800 satellites are needed to begin rolling out the first, albeit limited, iteration of its global internet service.

If all goes as planned, the Falcon 9 will lift off from Space Launch Complex 40 at 3:10 a.m. EDT (0710 GMT) on Tuesday.

Photos: X-37B Space Plane - The Orbital Test VehicleIn photos: SpaceX launches X-37B space plane, lands Falcon 9 rocketGallery: Declassified US spy satellite photos & designsFollow Amy Thompson on Twitter @astrogingersnap. Follow us on Twitter @Spacedotcom or Facebook.

<a href="https://www.space.com/your-favorite-magazines-space-science-deal-discount.html" data-link-merchant="space.com"" target="_blank">OFFER: Save 45% on 'All About Space' 'How it Works' and 'All About History'!

For a limited time, you can take out a digital subscription to any of <a href="https://www.space.com/your-favorite-magazines-space-science-deal-discount.html" data-link-merchant="space.com"" data-link-merchant="space.com"" target="_blank">our best-selling science magazines for just $2.38 per month, or 45% off the standard price for the first three months.

View Deal