The second time was the charm for the finale of the Delta family of rockets. Following an issue with a gaseous nitrogen pipeline beyond the control of United Launch Alliance (ULA) that caused the March 28 scrub the second launch attempt on April 9 proved successful.

Liftoff of the Delta 4 Heavy rocket from Space Launch Complex 37 (SLC-37) at Cape Canaveral Space Force Station occurred at 12:53 p.m. EDT (1653 UTC). The “most metal of all rockets” as described by ULA President and CEO Tory Bruno rocketed away from the pad at the start of the launch window, carrying a payload for the National Reconnaissance Office (NRO).

In the final four minutes prior to liftoff last go around, there were two issues that cropped up, according to Bruno. The first was a violation of ground wind limits, which forced the initial hold. That was coupled with an issue that came up with a gaseous nitrogen pump.

The pipeline system that services active launchpads both at the Kennedy Space Center as well as at CCSFS is owned by NASA and is managed by prime contractor, Air Liquide. 

In response to questions from Spaceflight Now regarding the extent of the issue and the measures taken to resolve it, Air Liquide provided the following statement:

“Air Liquide is committed to providing a safe and reliable supply of industrial gases to the U.S. space industry, as it has successfully been doing for more than 60 years.  Air Liquide confirms that a pump failure occurred on March 28 at its nitrogen plant supplying NASA’s Space Launch System (SLS).  Air Liquide worked diligently with NASA to understand the circumstances and resolve the situation and is prepared onsite to support the rescheduled launch of the Delta IV Heavy rocket.”

In a follow-up with NASA regarding the steps taken, the agency said that it “is aware that Air Liquide has taken action to resolve the pump issues at their nitrogen plant,” adding that “We appreciate their efforts in this matter.”

“As always, NASA Kennedy continues to monitor the pipeline and other infrastructure of key launch commodities on Kennedy property and will take any other steps that may be needed to ensure successful delivery of these important resources,” NASA said in a statement.

The 45th Weather Squadron also forecast much better conditions for launch with this second go-around. Its launch day forecast showed 90 percent odds of favorable weather during the launch window with the potential for cumulus clouds as the only watch item.

The NRO’s rocket

The NROL-70 mission will carry a spacecraft for the National Reconnaissance Office (NRO) up to orbit. Because it is a classified payload, little is publicly known about the satellite and its capabilities.

During a prelaunch press briefing in late March, Dr. Chris Scolese, the director of the NRO, noted that the NROL-70 payload will help boost needed capabilities on the ground without going into detail.

“It will provide exquisite capability that is needed by a lot of people and organizations, clearly, the policymakers, the warfighter and others, so that they can know what’s going on on the Earth,” Scolese said.

Out of the 16 missions that the Delta 4 Heavy rocket flew, 12 of them were in support of NRO missions. Bruno quipped during the briefing that it was “your rocket,” gesturing to Scalese.

“This will be the 16th flight. All but four of those have been for the NRO because of its unique capabilities,” Bruno said. “And so, we are looking forward to a successful mission and a great retirement of an amazing vehicle.”

The three-core vehicle will be replaced in its capabilities by ULA’s Vulcan rocket. It flew its first certification mission with the launch of Astrobotic’s Peregrine lunar lander in January and is preparing to fly for a second certification mission with Sierra Space’s Dream Chaser spaceplane onboard.

In response to reports that they may pursue a different path to certification, with either a different payload or just one mission, Bruno rebuked that, stating that ULA has “not asked for our cert plan to be amended from two flights to one” and that they have “no intention of doing so.”

Over the course of five order years for National Security Space Launch (NSSL) as part of Phase 2 of awards, 26 out of a total of 48 missions were awarded to ULA with 25 of those bound for flights using Vulcan. The first mission up to bat for the new launch vehicle will be USSF-106. Out of the nine NRO missions awarded, seven will launch using Vulcan.

The finale of the Delta family of rockets also comes as ULA is preparing to launch its first astronaut crew to low Earth orbit with the forthcoming Boeing Starliner Crew Flight Test. That spacecraft is preparing to roll out to ULA’s other launch pad at Space Launch Complex 41 (SLC-41) next week.

At the request of our customer, this will conclude our live coverage of today's countdown and liftoff of the #DeltaIVHeavy rocket on #NROL70 and #TheDeltaFinale from Cape Canaveral, Florida. For the final time, this is Delta Launch Control, signing off. https://t.co/0ZAppUgxBy pic.twitter.com/8AvX9TMAdo

— ULA (@ulalaunch) April 9, 2024

Update 3:10 p.m. ET: ULA flight teams called a scrub of the mission at about T-00:03:58.

United Launch Alliance will have to wait a bit longer before it bids a fond farewell to what its CEO calls “the most metal of all rockets.” Just seconds after the launch teams were coming out the final planned hold and into the final four minutes of the countdown, a hold was called and teams prepared to unload the propellant from the vehicle.

In a statement on social media, ULA President and CEO Tory Bruno explained the situation was a bit of a one, two punch.

“We exceeded the limit for winds and had to call a hold with a four-minute recycle,” Bruno said on X, formerly known as Twitter. “During the hold a Cape GN2 (gaseous nitrogen) pipeline ground pump failed causing a scrub. See you tomorrow.”

Liftoff from Space Launch Complex 37 (SLC-37) is now set for 1:37 p.m. EDT (1737 UTC). This mission, NROL-70, will be the last Delta rocket, flying in its three-core heavy configuration, on behalf of the National Reconnaissance Office (NRO). The rocket is carrying a classified payload and signals the end of the Delta chapter for ULA as its new Vulcan rocket prepares to really take over.

The 45th Weather Squadron forecasts only 30 percent odds of favorable weather for launch on Thursday, March 28, with ground winds and cumulus clouds being the primary concerns. Weather improves to 60 percent favorable on Friday with ground winds being the primary concern in this 24-hour backup scenario.

“Winds at ground level at the pad, especially on a Delta 4, which is a three-core rocket, lots of surface area, the concern is being blown back towards the launch tower,” said ULA President and CEO Tory Bruno during a prelaunch press conference. “We have a very well-understood criteria. It depends on the angle of the wind and we know what to do. We can launch through a pretty narrow moment in time. So, if the winds calm down, even for just a few minutes, so that we’re confident that that’s where they’re going to be, then we’ll launch through that opportunity.”

On Wednesday, ULA Launch Director Tom Heter III led the Launch Readiness Review (LRR), which resulted in leaders of ULA, the NRO and the U.S. Space Force signing off on the Launch Readiness Certificate.

Bruno marked the moment on Wednesday by remarking that the finale of Delta is “bittersweet” for him and the company.

“This is such and amazing piece of technology. 23 stories tall and half a million gallons of propellant, two-and-a-quarter million pounds of thrust and the most metal of all rockets, setting itself on fire before going to space,” Bruno said. “So, retiring it is obviously the future, moving to Vulcan, a less-expensive, higher-performance rocket, but still sad.”

The NROL-70 mission will mark the 12th time that the NRO has called upon the launch services of the Delta 4 Heavy rocket. The payload launching on this vehicle was awarded to ULA as part of a Launch Vehicle Production Services (LVPS) agreement on Oct. 24, 2018.

In September 2019, the Space and Missile Systems Center (now Space Systems Command) packaged it as part of a sole source, five-year, $1.18 billion Firm-Fixed-Price contract modification, which included Launch Operations Support (LOPS) for NROL-70 along with four other NRO missions. Officials said in a statement in 2019 that the bundle created a cost savings of $455 million.

“Mission success is our top priority. These satellites are critical to our Intelligence Community and national security,” said Col. Robert Bongiovi, Director of Launch Enterprise at the time. “Finalizing the launch operations support for these Delta IV Heavy launch services is a fundamental step to deliver these critical national assets to their intended orbits.”

“These are the last remnants of our sole source contracts. We look forward to embracing the competitive landscape that we have worked hard with industry to create,” he added. “The competitive launch services market is strong, and we look forward to the Phase 2 acquisition that leverages this market and builds upon our legacy of mission success.”

The Delta 4 rocket flew in the heavy configuration a total of 15 times leading up to its swan song:

• Dec. 21, 2004 – DemoSat
• Nov. 11, 2007 – DSP-23
• Jan. 18, 2009 – USA-202/NROL-26
• Nov. 21, 2010 – USA-223/NROL-32
• Jan. 20, 2011 – USA-224/NROL-49
• June 29, 2012 – USA-237/NROL-15
• Aug. 26, 2013 – USA-245/NROL-65
• Dec. 5, 2014 – NASA’s Orion Exploration Flight Test-1 (EFT-1)
• June 11, 2016 – USA-268/NROL-37
• Aug. 12, 2018 – NASA’s Parker Solar Probe
• Jan. 19, 2019 – NROL-71
• Dec. 11, 2020 – USA-268/NROL-44
• April 26, 2021 – NROL-82
• Sept. 24, 2022 – NROL-91 (final Vandenberg mission)
• June 22, 2023 – NROL-68

https://twitter.com/NatReconOfc/status/1664706195607769092

The Delta 4 Heavy flying the NROL-70 mission was delivered to the Cape in May 2023 after departing from the ULA’s factory in Decatur, Alabama, 22 years after the first Delta 4 (dubbed the ‘static fire test unit’) arrived for pathfinder testing.

The rocket is powered by a trio of common booster cores (CBSs), which are outfitted with RS-68A engines. The Delta Cryogenic Second Stage (DCSS) features an RL10C-2-1 engine and is topped with a metallic trisector payload fairing that harkens back to the aluminum isogrid fairings used on the Titan 4 from Martin Marietta (later Lockheed Martin).

Both stages use a combination of liquid oxygen and liquid hydrogen. In tandem, the three boosters produce 2.1 million pounds of thrust at liftoff. The upper stage generates 24,750 pounds of thrust following stage separation.

During a prelaunch media briefing, Brig. Gen. Kristin Panzenhagen, Space Launch Delta 45 Commander, noted that she has been part of the U.S. Air Force and subsequentially the U.S. Space Force since the Delta 4 Heavy began launching. She said she’s fortunate to have been in proximity to the rocket throughout its lifetime.

“Very exciting for me to be here. I was a young captain when we launched the first couple of Delta 4 Heavy’s out of here. So, to see that kind of come full circle is a special moment in my career,” Panzenhagen said.

She said it’s also illustrative of the partnerships needed to protect American interests in space and on the ground.

“The inter-agency partnership between the NRO and the Space Force, but then also, we wouldn’t be able to do this without our industry partners as well,” Panzenhagen said.

Dr. Chris Scalese, the director of the NRO, declined to go into detail about this national security spacecraft onboard the NROL-70 mission, but stated that it will bolster needed capabilities.

“It will provide exquisite capability that is needed by a lot of people and organizations, clearly, the policymakers, the warfighter and others, so that they can know what’s going on on the Earth,” Scalese said.

ULA’s Delta(-v)

Since its launch debut on May 13, 1960, as the Thor-Delta (aka Delta DM-19 or Delta), the Delta family of rockets showcased a storied history for civil and governmental spaceflight. Prior to the NROL-70 mission, Delta rockets have launched 388 times: 293 times from Cape Canaveral and 95 times from Vandenberg Space Force Base in California.

The lion’s share of the Delta legacy came from the teal-colored Delta 2 rocket. In the wake of the Challenger disaster, then President Ronald Regan issued a National Space Launch Strategy to develop a rocket designed for the military to have its launch capabilities. Delta 2 first flew on Feb. 14, 1989.

There were two variants of that vehicle, the lite 6000-series, which added the Extra Extended Long Tank first stage, and the 7000-series, which debuted GEM-40 solid boosters and the RS27A main engine.

The Delta 2 would go on to fly 155 mission in total, with eight of those being missions to Mars. NASA’s Spirit and Opportunity rovers got their ride to the Red Planet on a Delta 2 rocket.

Amid the myriad of Thor-Delta missions, versions of the rocket’s first stage were spunoff and built under license in Japan for that nation’s N-1, N-2 and H-1 vehicles, which launched from the Tanegashima Space Center a total of 24 times between 1975 and 1987.

In turn, that spun out the Delta 3 (8000-series), which was developed through a partnership between McDonnell Douglas and Boeing. However, it only flew three missions in total, two of which ended in failure and the third with just a dummy payload.

The sunsetting of that rocket made way for the Delta 4 rocket, which began launching in 2002. The vehicle boasted five different launch configurations:

• Delta 4 Medium
• Delta 4+(4,2)
• Delta 4+ (5,2)
• Delta 4+ (5,4)
• Delta 4 Heavy

The difference between the Delta 4+ rockets was if they flew a 4-meter or a 5-meter fairing and if they they had two or four strap-on solid rocket motors (SRMs). To date, there have been 45 launches of a Delta 4 rocket across all variations. The last Delta 4 Medium launched in August 2019.

Bruno said that while he previously was reluctant to answer questions about his favorite of the Delta 4 Heavy missions, he does have a clear preference: the 2018 launch of the Parker Solar Probe.

“And not just because it was a cool mission, where we were going to send a probe literally flying through the atmosphere of the Sun, currently the fastest human(-made) object in the universe, but also because we could have Dr. Parker there with us,” Bruno said. “90-years-old, a rebel scientist who first said space is not empty. It’s full of solar wind and things like that. And they told him he was crazy and he stuck to his guns. And eventually, we had the honor of flying the culmination of his life’s work.”

“So, up until this launch, that one was my favorite.”

Sunrise, sunset

This sunsetting of the Delta program comes as the sun rises on ULA’s next heavy-lift launch vehicle: Vulcan. The rocket performed its first certification mission (Cert-1) in January when it launched Astrobotic’s Peregrine lunar lander. It is now on its way towards launching Sierra Space’s Dream Chaser spacecraft to the International Space Station later this year.

Bruno said the NROL-70 mission that will culminate the Delta 4 Heavy line is a prime example of what Vulcan will be capable of launching using a single core, instead of three.

“The National Security Space mission is our core and the unique set of missions there require this high-energy rocket capability, very special orbits. And we designed Vulcan specifically for that. That’s its optimum,” Bruno said. “Every rocket can do a range of missions, but there’s one mission that it’s best at. [Vulcan] is literally designed to be best at the mission we’re going to fly here with this last Delta 4. So, that’s part of why it’s so important to us.”

“It collapses the price of that particular mission. Delta 4 is three rockets bolted together. That’s basically what it is. And with a single-core Vulcan, we’re able to collapse that cost by like 70 percent and make that mission a lot more practical and also able to fly at a much higher tempo, which is going to be pretty important as the country faces into the threat from Russia and especially China,” Bruno added.

Scolese said that even though this type of mission could be flown on a Vulcan in the future, logistics around timing made the final Delta 4 Heavy launch a more reasonable choice.

“It takes a lot of planning to put a payload on a rocket. So, we needed time to do it. And we had the spacecraft ready to go and we had a rocket that we trust. So, it made sense to continue on with this,” Scolese said. “Something has to be last and we’re proud to be that vehicle. We have a lot of confidence in the system: that’s the rocket, ULA, the Space Force, the Cape, everyone that’s involved in it.”

The higher tempo Bruno mentioned will be reflected in a launch cadence with Vulcan of between 25 and 30 times per year by the end of 2025. He said the pacing item in their supply chain are the Blue Origin-built BE-4 engines, the performance of which he lauded in the aftermath of Cert-1.

“The reason the BE-4 is a little bit behind everybody else is because it took a little longer to get it developed and finished and it is now,” Bruno said. “We have wonderful facilities in the BE-4 factory in Huntsville that Blue Origin has built and expanded, literally doubled their factory size to do this. So, they have to catch up now to everybody else building ahead.”

And while as they head of ULA Bruno said he’s looking forward to what comes next with Vulcan, he said it’s certainly the end of an era.

“It just has a storied legacy in our community and it has done great things for our nation,” Bruno said. “We’re very proud to have been a part of that. And even though Vulcan is the future, I’m personally sad to see it go.”

The second-to-last flight of United Launch Alliance’s Delta rocket lifted off from Cape Canaveral early Thursday and delivered a top secret spy satellite into orbit for the U.S. government, snapping the longest lull in launches in ULA’s history.

Liftoff of ULA’s 15th Delta 4-Heavy rocket, and 44th Delta 4 rocket overall, occurred at 5:18 a.m. EDT (0918 UTC) Thursday from Pad 37B at Cape Canaveral Space Force Station. ULA’s launch team pushed back the launch time by more than 90 minutes Thursday after preparations fell behind schedule due to stormy weather.

The mission’s first launch attempt Wednesday morning was scrubbed due to an issue with a valve in a ground pneumatics system.

The 235-foot-tall (71.6-meter) Delta 4-Heavy rocket hauled into orbit a classified payload for the National Reconnaissance Office, the U.S. government’s spy satellite agency. The NRO does not officially disclose details about its satellites, but expert observers of military space missions believe the Delta 4 rocket sent a large spacecraft into orbit designed to intercept telephone calls, data transmissions, and other types of communication by U.S. adversaries.

The circumstances of Thursday’s launch, including its due east trajectory and the use of the Delta 4-Heavy, suggest it carried a type of satellite known publicly as an “Advanced Orion” or “Mentor” spy spacecraft. The Advanced Orion satellites fly in geosynchronous orbit, circling more than 22,000 miles (nearly 36,000 kilometers) and closely hugging the equator. In that orbit, the satellites fly in lock-step with Earth’s rotation, giving them fixed coverage areas over the same parts of the world 24 hours per day.

The Advanced Orion satellites require the combination of the Delta 4-Heavy rocket’s lift capability, long-duration upper stage, and huge 65-foot-long (19.8-meter) trisector payload fairing.

ULA’s launch team at the Delta Operations Center at Cape Canaveral supervised the eight-and-a-half hour countdown beginning Wednesday night. Technicians wheeled the Delta 4’s 330-foot-tall service gantry away shortly after sunset, clearing the way for loading of super-cold liquid hydrogen and liquid oxygen into the rocket.

After ticking down the final minutes until liftoff, the Delta 4-Heavy rocket fired its three RS-68A engines supplied by Aerojet Rocketdyne and flew east from Cape Canaveral powered by 2.1 million pounds of thrust. The hydrogen-fueled engines on the two side boosters of the Delta 4 burned nearly four minutes, then the side boosters dropped away from the Delta 4’s core booster. The engine on the core stage throttled down for the first few minutes of the flight to conserve propellant, then powered up to continue accelerating into space after jettison of the two side boosters.

The core stage shut down its engine about five-and-a-half minutes into the mission, followed moments later by separation of the center booster and ignition of the Aerojet Rocketdyne RL10 engine on the Delta 4’s upper stage. The rocket’s metallic payload fairing, which covered the NRO spacecraft during the climb through the atmosphere jettisoned more than six-and-a-half minutes after liftoff to reveal the NRO’s newest spy satellite to space for the first time.

At that time, the mission entered a government-imposed news blackout. ULA’s live launch broadcast ended, and the rest of the Delta 4’s climb to geosynchronous orbit occurred in secret. It was expected to take about six hours for the Delta 4 to deploy the NRO spy satellite into a nearly circular geosynchronous orbit positioned more than 20,000 miles over the planet, likely requiring three burns by the upper stage RL10 engine.

ULA and the NRO confirmed the launch was successful in a statement just before 12 p.m. EDT (1600 UTC) Thursday. The spy satellite agency, which designated the mission NROL-68, did not disclose any details about the payload.

“The NROL-68 mission is the latest national security payload to deliver critical intelligence information from space that our warfighters and decision makers need,” the NRO said in a statement. “NRO continues to develop the largest, most capable overhead constellation in NRO history that provides the foundation for America’s advantage and strength in space.”

“Today’s mission is another example of how the NRO continues to go above and beyond,” said Chris Scolese, director of the NRO. “Our architecture is evolving to ensure the United States remains the undisputed leader in space. The capabilities we are putting into orbit expand our intelligence advantage and enable us to deliver on our mission of keeping America safe.”

The NRO’s Advanced Orion satellites are among the largest spacecraft ever sent into space. When viewed from Earth, they shine with the brightness of an 8th magnitude star, making them easily visible with small binoculars despite their distant orbits, according to Ted Molczan, an authoritative skywatcher who tracks satellite activity.

Four previous Delta 4-Heavy launches in 2009, 2010, 2012, 2016, and 2020 followed similar trajectories after taking off from Cape Canaveral, each carrying a classified cargo for the National Reconnaissance Office. Independent analysts believe all delivered top secret NRO eavesdropping satellites to space.

Before the launch in 2010 of a suspected Advanced Orion satellite, then-director of the NRO Bruce Carlson called the payload the “the largest satellite in the world.” The satellites are believed to carry giant antennas that unfurl to a diameter of up to 100 meters, or 328 feet, once in space.

The antenna can likely be tuned to listen in on communications among U.S. adversaries. It’s not known what part of the world the newest Advanced Orion satellite will cover, or whether the new spacecraft will replace an old satellite or expand the NRO’s eavesdropping web.

The Advanced Orion-series satellites began launching on Titan 4 rockets in 1995, following a pair of earlier NRO Orion payloads that launched in the 1980s on space shuttle missions. The NRO began using Delta 4-Heavy rockets for the Advanced Orion missions in 2009, following the retirement of the Titan 4 booster.

The NRO also has a fleet of sharp-eyed optical and radar spy satellites flying in orbits closer to Earth. Many of those were also launched on Delta 4 rockets.

The spy agency’s satellites collect imagery and intelligence data to help inform decisions by military commanders, senior policy makers, and the president.

ULA, a 50-50 joint venture between Boeing and Lockheed Martin, is retiring the Delta family of rockets in favor of the new-generation Vulcan launch vehicle, which is scheduled to make its first test flight later this year from Cape Canaveral. The Vulcan rocket will also replace ULA’s Atlas 5 launcher, which will fly 19 more times before retirement later in the 2020s.

The Atlas 5 and Delta 4 rockets currently flown by ULA show little resemblance to their forebears, but the names are steeped in history. The launch of the NROL-68 mission was the 388th flight of a rocket bearing the Delta name since 1960.

The launch of the NRO’s NROL-68 mission on the second-to-last Delta rocket was delayed from April to allow time for ULA engineers to swap out a leaky hydrogen valve on the Delta 4’s upper stage. The troubleshooting required the NRO’s spy satellite to be removed from the rocket, resulting in about a two-month delay.

Wentz said engineers found a “really small, hard to see” piece of particulate on the sealing surface of the valve, which is used to pressurize the upper stage fuel tank. The debris caused the valve to leak.

ULA has procured spare parts to be able to respond to replace faulty components on the final two Delta 4 rockets, even though the launch vehicle is no longer in production. Parts obsolescence is a common concern for aerospace vehicles nearing retirement.

“We were able to secure, in our final order of parts, some additional critical spares, and we’ve kept those on hand,” Wentz said. “In a case like this with the valves, we were able to take the valves back and were able to rework those and put them back in stock as a spare part. So that’s been our strategy all along is identifying the critical components, particularly the ones that aren’t used in either Atlas or Vulcan.”

The last flight of ULA’s Delta 4-Heavy rocket is scheduled for early 2024 on another NRO mission, designated NROL-70. That launch will mark the retirement of the Delta rocket family.

The Delta 4 rocket was developed by Boeing in the late 1990s and early 2000s, at the same time Lockheed Martin was bringing its Atlas 5 rocket into service. Boeing and Lockheed Martin merged their rocket programs in 2006 to form ULA, which was the sole provider of launch services for the military’s most expensive national security satellites until SpaceX broke into the market.

The military certified SpaceX’s Falcon 9 rocket for national security missions in 2015, and SpaceX and ULA split multibillion-dollar contracts in 2020 for a series of military satellite launches. While SpaceX will employ its Falcon 9 and Falcon Heavy rockets already in service, ULA will use its new Vulcan Centaur rocket to carry out its military launch commitments.

ULA says the Vulcan rocket is less expensive than the Atlas and Delta rockets, and it uses engines built in the United States, replacing the Russian engines that power the Atlas 5 rocket. The Delta 4-Heavy rocket also uses all U.S.-made engines, but it is more expensive than the Atlas 5, coming in at around $300 million per flight. In its most powerful configuration, the Vulcan Centaur will outlift the Delta 4-Heavy, without needing to use three first stage boosters to do the job.

The schedule for the first flight of ULA’s new Vulcan rocket is uncertain as engineers wrap up their investigation into an explosive incident on the rocket’s Centaur upper stage during a structural test earlier this year in Alabama. Earlier this year, ULA hoped to launch the first Vulcan rocket in May, with an eye toward certifying the new vehicle for military satellite launches by the end of 2023.

It now appears doubtful the Vulcan rocket will be certified for national security space missions by the end of the year. The Space Force’s certification requires two successful Vulcan test launches.

But ULA has more than 70 Vulcan rocket missions in its backlog, primarily for the Pentagon and for Amazon’s Kuiper broadband network, a potential future rival to SpaceX’s Starlink internet constellation. In response to the deep backlog, ULA is expanding the footprint of its 1.6 million-square-foot factory in Alabama, which was originally built by Boeing for the Delta 4 program, before ULA shifted Atlas rocket production there from Colorado. The factory is now transitioning to focus fully on Vulcan.

“For a while, obviously, we had Delta 4 and Atlas flowing through that factory,” Wentz said. “The most significant and obvious parts are in the final assembly area for Delta 4, which coincidentally, we’ve been processing Vulcans through. So Vulcan final assembly will flow right in there, and we’ll be able to increase our rate in that area.”

The last remnant of the Delta 4 program at the Alabama factory is the third and final upper stage ULA is building for NASA’s Space Launch System rocket to carry astronauts back to the moon. That upper stage is derived from the Delta 4-Heavy design, and will power the Artemis 3 mission into space in a few years. Then NASA will switch to a more powerful upper stage for future SLS moon rockets.

Despite a strong backlog of missions, delays kept ULA’s launch pads silent for the first half of 2023. The Delta 4-Heavy launch Thursday morning from Cape Canaveral was the company’s first mission since November, while rival SpaceX has launched 42 flights in 2023 with its Falcon rocket family.

The two-month delay in the Delta 4 launch was one reason for the slow start to the year. The first flight of astronauts on Boeing’s Starliner crew capsule, which will launch on ULA’s Atlas 5 rocket, has also been delayed from April until late this year, at the earliest, to allow Boeing to resolve several technical issues with the spacecraft.

And the Vulcan rocket’s first launch is also in a state of schedule uncertainty as ULA determines what it needs to do to overcome the fiery Centaur anomaly in March, which destroyed the upper stage’s structural test article after an unexpected leak of flammable hydrogen fuel.

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Follow Stephen Clark on Twitter: @StephenClark1.

United Launch Alliance has closed its Delta rocket assembly line in Alabama after the 389th and last Delta rocket rolled out of the factory for the journey to its launch base in Florida, clearing real estate in ULA’s sprawling manufacturing center for the next-generation Vulcan launch vehicle.

The major pieces of the final Delta 4-Heavy rocket arrived at Cape Canaveral in May after a journey from ULA’s factory in Decatur, Alabama, on the company’s rocket transport vessel, dubbed the R/S RocketShip. They will begin final launch preparations in Florida for the last flight of the Delta rocket program, an historic milestone mission scheduled for early 2024.

The three first stage boosters and upper stage for the final Delta 4-Heavy rocket were trucked from Port Canaveral through the gate to the military-run spaceport in mid-May, while ULA engineers were preparing the second-to-last Delta 4-Heavy rocket for liftoff with a classified satellite for the National Reconnaissance Office, the U.S. government’s spy satellite agency.

That mission is slated to lift off early Wednesday from Pad 37B at Cape Canaveral on a mission codenamed NROL-68. The final Delta 4 launch in 2024 goes by the designation NROL-70.

ULA, a 50-50 joint venture between Boeing and Lockheed Martin, is retiring the Delta family of rockets in favor of the new-generation Vulcan launch vehicle, which is scheduled to make its first test flight later this year from Cape Canaveral. The Vulcan rocket will also replace ULA’s Atlas 5 launcher, which will fly 19 more times before retirement later in the 2020s.

Gary Wentz, ULA’s vice president for government and commercial programs, said factory workers in Alabama wrapped up assembly and testing of the final Delta 4-Heavy rocket earlier this year, soon before the company shipped the rocket hardware down the Tennessee, Ohio, and Mississippi Rivers into the Gulf of Mexico for the trip to Florida’s Space Coast.

“We’ve completed all the Delta hardware there in Decatur,” Wentz said in an interview Tuesday with Spaceflight Now. “We’re in the process of transitioning the factory to support higher rate production of the Vulcan hardware.

“That was a huge accomplishment for the Decatur team to be able to complete the last Delta 4, get it shipped down to the Cape, and now it’s in the hands of our launch ops team,” Wentz said. “As soon as we launch L-68, we’ve already started doing some of the horizontal processing of L-70, and our plan is to prep it to support the customer’s launch next year.”

The last two Delta rocket missions will use the most capable version of the Delta, the Delta 4-Heavy, made by combining three large booster cores together to create a triple-body rocket. The three Aerojet Rocketdyne RS-68A engines, burning super-cold hydrogen fuel, will generate 2.1 million pounds of thrust at full power.

The launch set for Wednesday will be the 15th flight of a Delta 4-Heavy rocket, which debuted in 2004, and the 44th flight of the Delta 4 family since 2002. The primary customer for ULA’s Delta 4 rocket has been the U.S. military and the NRO.

The Delta 4 rocket program followed the Delta 2 rocket, a workhorse for NASA, the U.S. military, and commercial satellite operators in the 1990s and 2000s.

The launch of the NRO’s NROL-68 mission on the second-to-last Delta rocket was delayed from April to allow time for ULA engineers to swap out a leaky hydrogen valve on the Delta 4’s upper stage. The troubleshooting required the NRO’s spy satellite to be removed from the rocket, resulting in about a two-month delay.

Wentz said engineers found a “really small, hard to see” piece of particulate on the sealing surface of the valve, which is used to pressurize the upper stage fuel tank. The debris caused the valve to leak.

ULA has procured spare parts to be able to respond to replace faulty components on the final two Delta 4 rockets, even though the launch vehicle is no longer in production. Parts obsolescence is a common concern for aerospace vehicles nearing retirement.

“We were able to secure, in our final order of parts, some additional critical spares, and we’ve kept those on hand,” Wentz said. “In a case like this with the valves, we were able to take the valves back and were able to rework those and put them back in stock as a spare part. So that’s been our strategy all along is identifying the critical components, particularly the ones that aren’t used in either Atlas or Vulcan.”

The Atlas 5 and Delta 4 rockets currently flown by ULA show little resemblance to their forebears, but the names are steeped in history. Rockets bearing the Delta name began launching in 1960, and 387 Delta rockets have flown to date, most recently a Delta 4-Heavy launch from Vandenberg Space Force Base in California in September. That was the final Delta launch from the West Coast spaceport.

The Delta 4 rocket was developed by Boeing in the late 1990s and early 2000s, at the same time Lockheed Martin was bringing its Atlas 5 rocket into service. Boeing and Lockheed Martin merged their rocket programs in 2006 to form ULA, which was the sole provider of launch services for the military’s most expensive national security satellites until SpaceX broke into the market.

The military certified SpaceX’s Falcon 9 rocket for national security missions in 2015, and SpaceX and ULA split multibillion-dollar contracts in 2020 for a series of military satellite launches. While SpaceX will employ its Falcon 9 and Falcon Heavy rockets already in service, ULA will use its new Vulcan Centaur rocket to carry out its military launch commitments.

ULA says the Vulcan rocket is less expensive than the Atlas and Delta rockets, and it uses engines built in the United States, replacing the Russian engines that power the Atlas 5 rocket. The Delta 4 rocket also uses all U.S.-made engines, but it is more expensive than the Atlas 5. In its most powerful configuration, the Vulcan Centaur will outlift the Delta 4-Heavy, without needing to use three first stage boosters to do the job.

The schedule for the first flight of ULA’s new Vulcan rocket is uncertain as engineers wrap up their investigation into an explosive incident on the rocket’s Centaur upper stage during a structural test earlier this year in Alabama. Earlier this year, ULA hoped to launch the first Vulcan rocket in May, with an eye toward certifying the new vehicle for military satellite launches by the end of 2023.

It now appears doubtful the Vulcan rocket will be certified for national security space missions by the end of the year. The Space Force’s certification requires two successful Vulcan test launches.

But ULA has more than 70 Vulcan rocket missions in its backlog, primarily for the Pentagon and for Amazon’s Kuiper broadband network, a potential future rival to SpaceX’s Starlink internet constellation. In response to the deep backlog, ULA is expanding the footprint of its 1.6 million-square-foot factory in Alabama, which was originally built by Boeing for the Delta 4 program, before ULA shifted Atlas rocket production there from Colorado. The factory is now transitioning to focus fully on Vulcan.

“For a while, obviously, we had Delta 4 and Atlas flowing through that factory,” Wentz said. “The most significant and obvious parts are in the final assembly area for Delta 4, which coincidentally, we’ve been processing Vulcans through. So Vulcan final assembly will flow right in there, and we’ll be able to increase our rate in that area.”

The last remnant of the Delta 4 program at the Alabama factory is the third and final upper stage ULA is building for NASA’s Space Launch System rocket to carry astronauts back to the moon. That upper stage is derived from the Delta 4-Heavy design, and will power the Artemis 3 mission into space in a few years. Then NASA will switch to a more powerful upper stage for future SLS moon rockets.

Despite a strong backlog of missions, delays have kept ULA’s launch pads silent for the first half of 2023. The Delta 4-Heavy launch Wednesday morning from Cape Canaveral will be the company’s first mission of the year, while rival SpaceX has launched 41 flights in 2023 with its Falcon rocket family.

The two-month delay in the Delta 4 launch was one reason for the slow start to the year. The first flight of astronauts on Boeing’s Starliner crew capsule, which will launch on ULA’s Atlas 5 rocket, has also been delayed from April until late this year, at the earliest, to allow Boeing to resolve several technical issues with the spacecraft.

And the Vulcan rocket’s first launch is also in a state of schedule uncertainty as ULA determines what it needs to do to overcome the fiery Centaur anomaly in March, which destroyed the upper stage’s structural test article after an unexpected leak of flammable hydrogen fuel.

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United Launch Alliance’s second-to-last Delta 4-Heavy rocket is scheduled to blast off from Cape Canaveral April 20 with a classified cargo for the U.S. government’s spy satellite agency, a mission that will mark ULA’s first flight of the year, officials announced this week.

ULA and the National Reconnaissance Office, the customer for the national security mission, announced the target launch date Tuesday.

The mission is known as NROL-68, and is expected to loft a large surveillance satellite into geosynchronous orbit, joining a fleet of government-owned spacecraft designed to eavesdrop on the communications of adversaries and foreign powers. But the NRO does not disclose details about its missions, and independent analysts use information about the rocket’s lift capability, trajectory, and similar past launches to predict the purpose of spy satellite missions.

“Everything’s looking great and we’re on track to launch another vitally important national security capability into space,” said Maj. Gen. Stephen Purdy, the U.S. Space Force’s program executive officer for assured access to space. “This will be our third national security launch this year.”

“These launches place critical capabilities into orbit for our nation and our allies in what are dynamic times for the space community,” Purdy said in a statement. “Every member of our launch team understands what’s at stake and works with care and efficiency to prepare for what’s going to be a tremendous launch.”

ULA, a 50-50 joint venture between Boeing and Lockheed Martin, is retiring the Delta family of rockets in favor of the new-generation Vulcan launch vehicle, which is scheduled to make its first test flight as soon as early May from Cape Canaveral. The Vulcan rocket will also replace ULA’s Atlas 5 launcher, which will fly 19 more times before retirement later in the 2020s.

There are just two more Delta rockets remaining in ULA’s backlog. Both missions will use the most capable version of the Delta rocket, the Delta 4-Heavy, made by combining three large booster cores together to create a triple-body rocket. The three Aerojet Rocketdyne RS-68A engines, burning super-cold hydrogen fuel, will generate 2.1 million pounds of thrust at full power.

The launch set for April 20 will be the 15th flight of a Delta 4-Heavy rocket, which debuted in 2004, and the 44th flight of the Delta 4 family since 2002. The primary customer for ULA’s Delta 4 rocket has been the U.S. military and the NRO.

The Delta 4 rocket program, originally developed by Boeing, followed the Delta 2 rocket, a workhorse for NASA, the U.S. military, and commercial satellite operators in the 1990s and 2000s.

The Atlas 5 and Delta 4 rockets currently flown by ULA show little resemblance to their forebears, but the names are steeped in history. Rockets bearing the Delta name began launching in 1960, and 387 Delta rockets have flown to date, most recently a Delta 4-Heavy launch from Vandenberg Space Force Base in California in September. That was the final Delta launch from the West Coast spaceport.

Both Delta 4-Heavy rockets left to fly will blast off from pad 37B at Cape Canaveral on missions for the NRO. The final Delta 4-Heavy will launch the NROL-70 mission in 2024.

ULA ground teams at Cape Canaveral integrated the Delta 4-Heavy’s three hydrogen-fueled boosters after the hardware arrived from the company’s factory in Decatur, Alabama. Then technicians attached the rocket’s upper stage, powered by an Aerojet Rocketdyne RL10 engine, before rolling the rocket to the pad and lifting it vertical earlier this year.

The launch team completed a practice countdown, or wet dress rehearsal, on the Delta 4-Heavy rocket Monday. The dress rehearsal involved loading thousands of gallons of super-cold liquid hydrogen and liquid oxygen into the Delta 4-Heavy on pad 37B.

The mission set for launch April 20 will be the first launch from pad 37B since December 2020.

With the practice countdown complete, ground crews will next hoist the top secret payload for the NROL-68 mission on top of the Delta 4-Heavy inside the launch pad’s mobile gantry structure. A separate team is readying the spacecraft at a separate payload processing facility clean room at Cape Canaveral.

The Delta 4-Heavy rocket will stand 235 feet (71.6 meters) tall when fully stacked on the launch pad.

After a few weeks of final checkouts and preparations, ULA will wheel the mobile gantry into position to reveal the Delta 4-Heavy for liftoff. Six hours after launch, the rocket will deploy its classified payload into geosynchronous orbit more than 22,000 miles (nearly 36,000 kilometers) above Earth and closely hugging the equator.

Reaching such an orbit required the rocket to follow one of the most challenging flight profiles in the launch business, with three burns expected by the Delta’s upper stage to deploy its satellite payload at the targeted altitude.

While ULA preps the Delta 4-Heavy for liftoff from pad 37B, the company is working on the first flight-qualified Vulcan rocket a few miles to the north at pad 41. The Vulcan launch team completed a pair of tanking tests on the first stage of the Vulcan rocket and its Centaur upper stage, an upgraded, larger version the upper stage flown on the Atlas 5 rocket.

The Vulcan rocket will be powered by two Blue Origin-built BE-4 engines on the first stage.

Later this spring, ULA plans to ignite the Vulcan rocket’s BE-4 engines for a brief hold-down test-firing at pad 41, then roll the Vulcan rocket back to its vertical hangar, where technicians will install two strap-on solid rocket boosters and the payload fairing.

The inaugural test flight of the Vulcan rocket will carry into space an Astrobotic commercial moon lander and two prototype satellites for Amazon’s Kuiper broadband network.

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The U.S. Space Force is preparing for as many as 87 launches from Florida’s Space Coast in 2023, including dozens more SpaceX missions and the expected debuts of United Launch Alliance’s Vulcan and Relativity’s Terran 1 rockets.

“We expect to have about 87 launches from the Cape in calendar year 2023,” said Lt. Col. Colin Mims, commander of the 1st Range Operations Squadron, which provides range safety support for launches from the Eastern Range at Cape Canaveral Space Force Station.

The busy 2023 follows a record-setting 2022 at Cape Canaveral. There were 57 orbital-class rockets that departed launch pads at Cape Canaveral Space Force Station and NASA’s Kennedy Space Center last year, a sharp increase over the previous record of 31 orbital launch attempts in 1966 and 2021.

SpaceX launched 48 of the 57 missions out of the Florida spaceport last year. United Launch Alliance added six flights with its Atlas 5 rocket, and NASA’s huge Space Launch System moon rocket aced its first test flight Nov. 16. Astra launched two flights of its light-class small satellite launcher in February and June, but both missions failed in their bids to reach orbit.

The U.S. Space Force runs the Eastern Range, which oversees public safety for launches out of Florida’s Space Coast. Space Launch Delta 45, formerly the 45th Space Wing, has upgraded infrastructure, streamlined operations, and encouraged rocket companies to switch to autonomous flight safety systems to help shorten the time needed between launches.

There were 16 space launches from the Eastern Range in 2019. The launch rate in 2022 more than tripled that number.

“I think it just shows the pace at which the commercial (demand) is growing,” Mims said. “I think it’s our geography here, being off of the coast, that we can launch into a polar orbit or an equatorial orbit, that’s very advantageous. And our ability to rapidly turn the pads and schedule launches quickly, that shows our ability or that has highlighted our ability to provide services to these launch service providers.”

Launches into polar orbit used to be the near-exclusive domain of Vandenberg Space Force Base in California, but the Eastern Range approved a SpaceX request to begin launching on a southern corridor from Cape Canaveral in 2020, the first polar orbit mission from Florida since 1969.

“Three years ago … we would surge for every launch. It was a major ordeal,” said Col. Jason King, commander of the 45th Weather Squadron at Patrick Space Force Base and Cape Canaveral Space Force Station. “We’ve since then changed the mindset to where we’re operating more like an airport now. We call it a spaceport. So we don’t want to full-on surge for every launch attempt, and we want to change the mindset into where it’s pretty much normal operations.”

On Aug. 4, the Eastern Range supported two launches by ULA’s Atlas 5 rocket and SpaceX’s Falcon 9 just 12 hours and 39 minutes apart, the shortest duration between two space launches from the Space Coast since 1967.

On Dec. 16, the military team that runs the range was ready to accommodate two launches by SpaceX Falcon 9 rockets from different pads just 33 minutes apart. But SpaceX ended up delaying one of the missions to give priority to the other.

The demand for launch services is increasing in the United States. SpaceX alone aims to launch as many as 100 times this year, including flights out of Florida, California, and test flights of the Starship mega-rocket from South Texas. SpaceX hasn’t disclosed how many of those launches it will base out of Cape Canaveral, but the majority of the missions on the company’s 2023 manifest are expected to fly from Florida’s Space Coast.

“We’ve just begun to see the increase,” King said in a recent interview. “We estimate in the next probably two to three years we’ll have 100 launches here on the Eastern Range. But commercial launch service providers and commercial satellites are being launched at the quickest rate we’ve ever seen. So we just anticipate the launch rate to continue to increase.

“We’ve really trimmed the fat,” King said. “We’ve questioned our procedures. We’ve actually stopped doing some things that were not necessary, while at the same time keeping the Eastern Range as safe as possible.”

“One of the biggest things that have gotten us to this point where we can have multiple launches in the same day, or within minutes of each other, is (reducing) the amount of equipment needed for some of these launches,” Mims said. “Contractors or launch service providers are now using a thing called automatic flight termination system. So that means that the the vehicle itself has an on-board suite of sensors that can ensure that the rocket is staying on its course, and if not, it will self-destruct … The mission is all about public safety and ensuring those rockets are going where they’re supposed to be going.”

“In addition to that, there’s a lot of other infrastructure that we’ve invested in,” said Lt. Col. David Schill, commander of 5th Space Launch Squadron, which supports national security launches from Cape Canaveral.

“Some of that infrastructure is as simple as roads and water deluge systems, but it’s also in a lot of the the partnerships with industry,” Schill said. “So they’re building additional hangar space and processing space, and allowing themselves multiple ways to process rockets simultaneously, so it’s not just limited to one hangar where they can process one rocket at a time. But they can do multiple hangars, multiple processing facilities, multiple launch pads, and that sort of construct is only going to continue to increase.”

The 45th Weather Squadron monitors weather conditions across the Cape Canaveral spaceport to ensure all parameters are acceptable for a rocket to launch safely. Lightning is a major constraint for launches from Florida. Meteorologists track cloud-to-ground and in-cloud lightning, and monitor the potential electrical charge within clouds that could cause lightning to strike a launch vehicle as it climbs through the atmosphere, a phenomenon known as rocket-triggered lightning.

King, the weather squadron’s commander, said the Space Force is working with universities to better understand the science of what causes a lightning strike. That could allow the weather team to relax the lightning rules for a rocket launch. King said the weather squadron at Cape Canaveral is set to receive a new weather radar.

“This is the cutting edge, just the new and best radar, specifically designed for launch operations,” King said.

SpaceX will start the 2023 schedule at Cape Canaveral with a Falcon 9 rocket launch set for 9:56 a.m. EST (1456 GMT) Tuesday, carrying 114 small satellites and micro-payloads into a polar orbit for customers around the world. The mission, called Transporter 6, is SpaceX’s sixth dedicated small satellite rideshare launch.

The Falcon 9’s first stage booster will return to Landing Zone 1 at Cape Canaveral Space Force Station, targeting a propulsive vertical touchdown about eight-and-a-half minutes after liftoff. The booster will be making its 15th flight to space, tying a record for SpaceX’s fleet of reusable rockets.

SpaceX plans to launch six to seven missions from Florida in January alone, including the launch of a Falcon Heavy rocket Jan. 12 from pad 39A at Kennedy Space Center. The Falcon Heavy, made by combining three Falcon 9 rocket cores together, will loft a pair of satellites into a high-altitude geosynchronous orbit for the Space Force.

Other Falcon 9 launches on tap for January from Florida include the next launch of 40 internet satellites for OneWeb, set for Jan. 8, and the launch of a GPS navigation satellite for the Space Force on Jan. 18. SpaceX also plans to launch more batches of Starlink internet satellites and the Spanish-owned Amazonas Nexus communications satellite before the end of the month.

The busy January will help SpaceX get out of the starting gate on its quest for up to 100 launches in 2023

SpaceX’s Falcon rocket flights from Florida this year include several crew launches for NASA, Axiom Space, and the all-private Polaris Dawn mission that aims to accomplish the first commercial spacewalk in Earth orbit. SpaceX has five Falcon Heavy missions on the books for 2023, all from Kennedy Space Center.

At least two new commercial launchers are slated to debut at Cape Canaveral this year.

United Launch Alliance’s new medium-to-heavy lift Vulcan rocket, which replaces its Atlas 5 and Delta 4 rocket families, could launch for the first time in the coming months. The rocket’s inaugural launch was delayed from last year as ULA awaited delivery of flight-ready BE-4 main engines from Blue Origin, Jeff Bezos’s space company.

In October, Blue Origin delivered the two BE-4 engines needed for the first Vulcan launch to ULA’s factory in Decatur, Alabama, where they were installed on the Vulcan’s main stage. The Vulcan core stage and Centaur upper stage will soon be delivered to Cape Canaveral for final integration and testing at the launch site.

The first Vulcan launch will haul into space a commercial moon lander built and owned by Astrobotic, plus two test platforms for Amazon’s planned Kuiper satellite internet network. A second Vulcan launch could occur later this year with Sierra Space’s first Dream Chaser cargo freighter for the International Space Station.

Relativity Space, a California-based startup founded in 2015, is also nearing its first orbital launch attempt. The company’s fully assembled Terran 1 rocket was rolled out to Launch Complex 16 at Cape Canaveral for the first time last month in preparation for final fueling tests and engine test-firings.

The Terran 1 rocket is designed to deliver small to medium-size payloads to space, with a lift capability of nearly a ton to a polar sun-synchronous orbit.

Blue Origin said in early 2022 that the first test launch of its New Glenn rocket, which stands as tall as NASA’s SLS moon rocket at 322 feet (98 meters) in height, would be delayed from late 2022 until the fourth quarter of 2023. The company has not updated its schedule since last March, but industry officials now widely believe the New Glenn’s debut flight from Cape Canaveral Space Force Station won’t happen before 2024.

Aside from SpaceX’s rapid-fire launch cadence, and the inaugural flights of the Vulcan and Terran 1 launch vehicles, ULA plans around five flights with its Atlas 5 rocket this year from Cape Canaveral, plus one launch of a Delta 4-Heavy rocket for the National Reconnaissance Office.

ULA’s Atlas 5 missions will include the company’s launch of astronauts on Boeing Starliner crew capsule. The Atlas 5 rocket will share the same launch pad with the Vulcan rocket.

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EDITOR’S NOTE: Watch a replay of our live coverage of the Falcon 9 launch with the Starlink 4-37 mission.

SpaceX launched 54 more Starlink internet satellites Saturday from Kennedy Space Center in Florida, using a Falcon 9 booster on its 15th flight to space, a record for the company’s reusable rocket fleet.

Liftoff of the 229-foot-tall (70-meter) Falcon 9 occurred at 4:32:30 p.m. EST (2132:30 GMT) Saturday from Launch Complex 39A. It was the third Falcon 9 launch in less than 34 hours, following missions Friday from Cape Canaveral Space Force Station — just a few miles from pad 39A — and Vandenberg Space Force Base in California.

Those flights deployed the U.S.-French SWOT satellite, designed to survey Earth’s surface water resources, and two commercial broadband satellites for SES’s O3b mPOWER constellation.

SpaceX delayed the Starlink launch, designated Starlink 4-37, from Friday to focus on the O3b mPOWER mission for SES, one of SpaceX’s oldest customers.

The Falcon 9 arced northeast from Florida’s Space Coast, aiming for a low Earth orbit inclined 53.2 degrees to the equator. The rocket’s upper stage released the 54 flat-packed Starlink satellites about 15 minutes into the mission.

The satellites on-board the Falcon 9 will add to SpaceX’s consumer-grade, high-speed, low-latency internet network. Subscribers can currently connect to the Starlink network in more than 40 countries and territories.

The first stage booster on the Starlink 4-37 mission set a record for SpaceX’s reusable rockets. The booster stage, tail number B1058, debuted May 30, 2020, with the historic launch of NASA astronauts Doug Hurley and Bob Behnken on SpaceX’s first human spaceflight mission.

It’s now flown 15 times so far, helping deliver 777 satellites into orbit, including the 54 Starlink internet satellites launched Saturday. The missions flown by B1058 have included the launch of a South Korean military communications satellite, a space station cargo mission, two Transporter small satellite rideshare missions, and 10 flights with Starlink satellites.

The launch Saturday was SpaceX’s first Starlink mission since Oct. 27. Since then, SpaceX had launched nine consecutive missions for commercial and U.S. government customers.

After Saturday’s mission, SpaceX has launched 3,612 Starlink satellites into orbit, including prototypes and failed spacecraft. The company currently has more than 3,200 functioning Starlink satellites in space, with about 3,000 operational and nearly 200 moving into their operational orbits, according to a tabulation by Jonathan McDowell, an expert tracker of spaceflight activity and an astronomer at the Harvard-Smithsonian Center for Astrophysics.

The 54 new Starlink satellites launched into one of five orbital “shells” in SpaceX’s internet constellation.

SpaceX targeted Shell 4 with Saturday’s mission. The network architecture includes satellites flying a few hundred miles up, orbiting at inclinations of 97.6 degrees, 70 degrees, 53.2 degrees, and 53.0 degrees to the equator. The spacecraft beam broadband internet signals to consumers around the world, connectivity that is now available on all seven continents with testing underway at a research station in Antarctica.

SpaceX is more than halfway complete with deploying the initial fleet of 4,400 Starlink internet satellites. The company has approval from the Federal Communications Commission to eventually launch and operate up to 12,000 Starlink spacecraft, and SpaceX has signaled it could aim to fly as many as 42,000 Starlink satellites in orbit.

SpaceX is developing an upgraded, much larger Starlink satellite design sized to launch on the company’s huge next-generation Starship rocket. But the Starship has not yet attempted a launch into low Earth orbit, and delays in developing and testing the new rocket will likely force SpaceX to start launching a smaller version of the new Starlink satellite design on Falcon 9 rockets.

The Starlink network was conceived as a venture to help draw in revenue to fund SpaceX’s ambition to build a base on Mars. The Starship rocket itself, designed to be fully reusable with relatively low operating costs, is central to Elon Musk’s Mars dream.

The launch Saturday was SpaceX’s 59th launch so far in 2022. Two more Falcon 9 rockets are scheduled to fly before the end of the year, one from Florida and one from California.

The higher launch rate has been aided by shorter turnarounds between missions at launch pads in Florida and California, and SpaceX’s reuse of Falcon 9 boosters and payload fairings. Launches carrying satellites for SpaceX’s own Starlink internet network, like the mission Saturday, have accounted for more than half of the company’s Falcon 9 flights so far this year.

Stationed inside a launch control center just south of Cape Canaveral Space Force Station for Saturday’s countdown, SpaceX’s launch team began loading super-chilled, densified kerosene and liquid oxygen propellants into the Falcon 9 vehicle at T-minus 35 minutes.

Helium pressurant also flowed into the rocket in the last half-hour of the countdown. In the final seven minutes before liftoff, the Falcon 9’s Merlin main engines were thermally conditioned for flight through a procedure known as “chilldown.” The Falcon 9’s guidance and range safety systems were also configured for launch.

After liftoff, the Falcon 9 rocket vectored its 1.7 million pounds of thrust — produced by nine Merlin engines — to steer northeast over the Atlantic Ocean.

The rocket exceeded the speed of sound in about one minute, then shut down its nine main engines two-and-a-half minutes after liftoff. The booster stage released from the Falcon 9’s upper stage, then fired pulses from cold gas control thrusters and extended titanium grid fins to help steer the vehicle back into the atmosphere.

Two braking burns slowed the rocket for landing on the drone ship “Just Read the Instructions” around 400 miles (650 kilometers) downrange approximately nine minutes after liftoff.

The Falcon 9’s reusable payload fairing jettisoned during the second stage burn. A recovery ship was also on station in the Atlantic to retrieve the two halves of the nose cone after they splash down under parachutes.

Landing of the first stage on Saturday’s mission occurred moments after the Falcon 9’s second stage engine cut off to deliver the Starlink satellites into orbit. Separation of the 54 Starlink spacecraft, built by SpaceX in Redmond, Washington, from the Falcon 9 rocket was confirmed at T+plus 15 minutes, 22 seconds.

Retention rods released from the Starlink payload stack, allowing the flat-packed satellites to fly free from the Falcon 9’s upper stage in orbit. The 54 spacecraft will unfurl solar arrays and run through automated activation steps, then use krypton-fueled ion engines to maneuver into their operational orbit.

The Falcon 9’s guidance computer aimed to deploy the satellites into an elliptical orbit at an inclination of 53.2 degrees to the equator. The satellites will use on-board propulsion to do the rest of the work to reach a circular orbit 335 miles (540 kilometers) above Earth.

After reaching their operational orbit, the satellites will enter commercial service and begin beaming broadband signals to consumers, who can purchase Starlink service and connect to the network with a SpaceX-supplied ground terminal.

ROCKET: Falcon 9 (B1058.15)

PAYLOAD: 54 Starlink satellites (Starlink 4-37)

LAUNCH SITE: LC-39A, Kennedy Space Center, Florida

LAUNCH DATE: Dec. 17, 2022

LAUNCH TIME: 4:32:30 p.m. EST (2132:30 GMT)

WEATHER FORECAST: 60% chance of acceptable weather; Low risk of upper level winds; Low-moderate risk of unfavorable conditions for booster recovery

BOOSTER RECOVERY: “Just Read the Instructions” drone ship east of Charleston, South Carolina

LAUNCH AZIMUTH: Northeast

TARGET ORBIT: 144 miles by 208 miles (232 kilometers by 335 kilometers), 53.2 degrees inclination

LAUNCH TIMELINE:

• T+00:00: Liftoff
• T+01:12: Maximum aerodynamic pressure (Max-Q)
• T+02:27: First stage main engine cutoff (MECO)
• T+02:31: Stage separation
• T+02:38: Second stage engine ignition
• T+02:42: Fairing jettison
• T+06:47: First stage entry burn ignition (three engines)
• T+07:06: First stage entry burn cutoff
• T+08:28: First stage landing burn ignition (one engine)
• T+08:41: Second stage engine cutoff (SECO 1)
• T+08:49: First stage landing
• T+15:22: Starlink satellite separation

MISSION STATS:

• 192nd launch of a Falcon 9 rocket since 2010
• 201st launch of Falcon rocket family since 2006
• 15th launch of Falcon 9 booster B1058
• 164th Falcon 9 launch from Florida’s Space Coast
• 59th SpaceX launch from pad 39A
• 153rd launch overall from pad 39A
• 131st flight of a reused Falcon 9 booster
• 66th Falcon 9 launch primarily dedicated to Starlink network
• 58th Falcon 9 launch of 2022
• 59th launch by SpaceX in 2022
• 56th orbital launch attempt based out of Cape Canaveral in 2022

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United Launch Alliance sent a triple-core Delta 4-Heavy with a top secret U.S. government spy satellite into orbit Saturday from California’s Central Coast, closing out a chapter in the tangled history of a launch pad originally built to support military astronaut missions on Titan rockets and space shuttles.

The spy satellite on-board the Delta 4-Heavy is owned by the National Reconnaissance Office, which discloses few details about its spacecraft. The circumstances of the launch Saturday — its launch site, rocket configuration, and flight track after liftoff — led independent analysts to conclude the Delta 4 likely carried a high-resolution electro-optical surveillance satellite into orbit.

Two more Delta 4-Heavy rockets are left in ULA’s inventory for launches in 2023 and 2024 from Cape Canaveral as the company transitions to the next-generation Vulcan Centaur rocket, the replacement for the Atlas and Delta launcher families that date back to the dawn of the Space Age.

The Atlas 5 and Delta 4 rockets currently flown by ULA show little resemblance to their forebears, but the names are steeped in history. Saturday’s launch from Vandenberg Space Force Base was the 95th and final flight of a Delta rocket from the military spaceport about 140 miles (225 kilometers) northwest of Los Angeles, and the 387th launch overall of a rocket bearing the Delta name.

It was the 10th launch of a Delta 4 rocket — and the fifth in the Delta 4-Heavy configuration — from Space Launch Complex 6, a picturesque launch site nestled on a hillside bluff overlooking the Pacific Ocean. The sprawling launch pad, known as SLC-6 or “Slick Six,” faces an uncertain future after the last Delta 4 flight from the site Saturday. The Space Force, which owns the pad and leased it to ULA, doesn’t yet have another tenant lined up to take over the facility.

“For us, seeing the last Delta launch from Vandenberg is bittersweet, for sure. We’re sorry to see it go,” said Col. Bryan Titus, vice commander of Space Launch Delta 30, the unit in charge of Vandenberg Space Force Base and the Western Range.

Three Aerojet Rocketdyne RS-68A main engines roared to life in the final seconds of Saturday’s countdown at SLC-6, sending a plume of red-hot exhaust out each side of the flame trench under the pad. After a staggered start sequence, the hydrogen-fueled engines powered the 233-foot-tall (71-meter) Delta 4-Heavy off the pad at 3:25:30 p.m. PDT (6:25:30 p.m. EDT; 2225:30 GMT).

Ten seconds later, the rocket vectored thrust from its main engines to steer south-southeast from Vandenberg, taking an arcing trajectory over the Pacific Ocean riding 2.1 million pounds of thrust. The rocket broke the sound barrier in about 80 seconds as the RS-68A engines on the Delta 4-Heavy’s side boosters operated at full throttle, while the center engine throttled back to conserve fuel for the first few minutes of the flight.

The engines burned 5,000 pounds of liquid hydrogen and liquid oxygen propellants each second, quickly burning through the 450,000 gallons of cryogenic fluids loaded into the Delta 4-Heavy’s three orange common booster cores during the countdown.

The side boosters shut down their engines and separated from the core stage about 4 minutes into the flight, heading for uncontrolled splashdowns in the Pacific a few hundred miles downrange from Vandenberg. The core stage then throttled up its RS-68A engine to burn for another minute-and-a-half before separation from the Delta 4’s cryogenic upper stage, which did the rest of the work to place the top secret spy payload into orbit.

The upper stage ignited its RL10 engine and released its clamshell-like payload fairing a few seconds later, and ULA ended its live coverage of the mission. The remainder of the flight occurred in a government-ordered news blackout.

The NRO and ULA issued press releases a little more than two hours after liftoff, confirming a successful conclusion to the launch, officially designated NROL-91.

“The Delta 4-Heavy has proven to be an integral part of the NRO’s history, helping us build the architecture for the world’s best space-based intelligence, surveillance and reconnaissance,” said Chris Scolese, director of the NRO. “As our agency and the aerospace industry continue to innovate and evolve, we will explore new vehicles for launching payloads even more efficiently and effectively, with even greater capacity, agility, speed, and resilience. We are excited about the new technologies and partnerships that will define our next chapter.”

The NRO has flown payloads on 15 Delta 4 missions to date. The final two Delta 4-Heavy rockets set for launch from Cape Canaveral in 2023 and 2024 will also loft classified NRO satellites.

NRO satellites collect optical and radar imagery, intercept radio transmissions, and gather other intelligence data for U.S. government leaders, deployed military forces, and intelligence agencies.

“We like to say we’re the nation’s eyes and ears in space,” said Space Force Col. Chad Davis, director of the NRO’s Office of Space Launch. “So we provide that capability for our warfighters, allied and U.S., for our national decision makers to put them in the best spot they possibly can to either make decisions or execute what they need to on the battlefield.”

Satellite trackers using publicly-available information on the Delta 4 rocket’s flight track after liftoff predicted the mission would place its payload into an orbit less than 250 miles (400 kilometers) above Earth, and at an orbital inclination of 73.6 degrees to the equator. It turned out the prediction was close to the mark.

Sky watchers spotted the satellite from the NROL-91 mission in the skies over the Netherlands early Sunday. Scott Tilley and Cees Bassa, both radio astronomers, also detected encrypted radio transmissions from the satellite, suggesting the spacecraft was healthy and in the expected orbit after launch.

The NROL-91 mission likely deployed a sister satellite to a payload launched on a Delta 4-Heavy rocket on the NRO’s NROL-71 mission in January 2019, according to Marco Langbroek, a Dutch archaeologist and an expert in the orbits of military spacecraft.

Both satellites launched into similar orbits. Seasoned trackers of spy satellites believe the NROL-71 and NROL-91 missions launched the first members of a new generation of Keyhole, or KH-11, optical reconnaissance satellites.

But previous KH-11 satellites launched into sun-synchronous polar orbits, at a different inclination than the 73.6-degree orbits achieved on the NROL-71 and NROL-91 missions. A Delta 4-Heavy launch from Vandenberg last year — between NROL-71 and NROL-91 — deployed its NRO payload into a more conventional sun-synchronous orbit, which is tailored for regular, repeatable observations of strategic sites, military installations and other targets of interest to U.S. intelligence agencies.

The KH-11 satellites are essentially bus-sized telescopes peering down on Earth, with primary mirrors measuring 7.9 feet (2.4 meters) across, the same size as the mirror on the Hubble Space Telescope. The ultra-sharp, very-high-resolution imagery produced by such satellites is believed to be unparalleled, and the spy craft relay their observations to the ground via the NRO’s dedicated network of communications satellites.

Delta 4-Heavy missions from California in 2011 and 2013 deployed gap-filler KH-11-type satellites to continue supplying the government with reconnaissance imagery after the NRO canceled a contract with Boeing for a replacement line of optical imaging craft as part of the Future Imagery Architecture program. Keyhole satellites before 2011 launched on Titan rockets from Vandenberg.

The NRO eventually selected Lockheed Martin — the same company that built the past generation of KH-11 satellites — to construct at least two new-generation spacecraft, introducing new technology and other upgrades into the spy satellite constellation.

The new electro-optical surveillance satellites, sometimes called KH-11 Block 5, have the same 2.4-meter mirror diameter as the earlier Keyhole-type Earth-imaging platforms, according to past public statements by government officials.

The launches of NROL-71 and NROL-91 into an orbit at a different inclination than the KH-11 satellites customarily fly caused some spy satellite observers to consider whether those missions carried a different kind of NRO payload, such as a radar imager. But without clear evidence otherwise, the consensus remains that NROL-71 and NROL-91 most likely delivered KH-11-type optical telescopes to orbit.

There are no other known hefty satellites in the NRO’s pipeline that require the Delta 4-Heavy’s lift capability. The Delta 4-Heavy can deliver payloads up to 62,540 pounds (28.3 metric tons) to low Earth orbit, making the Delta 4-Heavy the most powerful rocket in ULA’s fleet, and one of the most powerful operational launchers in the world.

Saturday’s launch was the the 43rd Delta 4 flight overall, and the 14th in the Delta 4-Heavy configuration, created by combining three expendable hydrogen-fueled booster cores together to haul the military and NRO’s most massive payloads into orbit.

“The National Reconnaissance Office puts absolutely exquisite capabilities on orbit,” Davis said. “And the natural extension to that is the Delta 4-Heavy is used for some of those even most exquisite and most sensitive kinds of capabilities that I wish we could share with the broader community. But that’s part of the idea, is that people don’t know that we can do the kinds of things that we can do in space, and that vehicle is just part and parcel to those absolutely exquisite capabilities on orbit delivering for this nation.”

After retirement of the Delta 4-Heavy, the NRO’s heaviest payloads will launch on SpaceX’s Falcon Heavy rocket or ULA’s Vulcan. Both are less expensive than the Delta 4-Heavy, which is priced at more than $400 million per mission.

SPACE FORCE LOOKING FOR NEW TENANTS AT SLC-6

Built among hills that hide the pad from public view, the SLC-6 launch site was originally constructed to support flights of military astronauts and NASA space shuttles.

The Air Force developed the SLC-6 launch site in the 1960s for the Manned Orbiting Laboratory program. Pentagon officials envisioned launching military astronauts on top of Titan rockets for orbital spy missions, but the program was canceled in 1969 before any launches from the SLC-6 pad.

NASA and the Air Force agreed in the 1970s to launch space shuttles from SLC-6, allowing astronauts to conduct military missions and deploy spy satellites in polar orbit. The space shuttle Enterprise, used for ground demonstrations and atmospheric test flights, was stacked on the SLC-6 launch with external tank and solid rocket booster test articles for fit checks in early 1985.

But the Air Force abandoned plans to launch military space shuttle flights from Vandenberg in the wake of the Challenger accident in 1986, and the shuttle-era buildings at the SLC-6 site sat mothballed for years. Lockheed Martin used the SLC-6 pad for four launches of its light-class Athena rockets in the 1990s, but those missions didn’t utilize much of the shuttle-era infrastructure at the site.

Boeing took over the SLC-6 pad and modified the shuttle infrastructure for the Delta 4 rocket, which first launched there in June 2006. ULA was formed later in 2006 by the merger of Boeing’s Delta and Lockheed Martin’s Atlas rocket programs. SLC-6 hosted its first launch of the triple-core Delta 4-Heavy rocket configuration in January 2011.

Read our 2011 story detailing the history of the SLC-6 launch pad, written just before the first Delta 4-Heavy flight from Vandenberg.

“SLC-6 is iconic here,” Titus said. “It’s legendary. It’s kind of what people think about when they think about Vandenberg. It’s had many lives. It started in the mid 1960s. They were going to support something called the Manned Orbiting Laboratory. In the ’70s and ’80s, it was built up for a shuttle program, and they ended up not going down that path. And then in the ’90s and 2000s, we started going down this path of launching Deltas from there, and we’ve had mission success after mission success out of that place for the last almost 20 years.

Northrop Grumman planned to use the SLC-6 launch pad for its now-canceled OmegA rocket, which the company proposed to the Pentagon in a competition for military launch contracts. But the Defense Department selected ULA’s Vulcan rocket and SpaceX’s Falcon 9 and Falcon Heavy launchers in 2020 for eligibility to compete for military launches scheduled through 2027.

Northrop Grumman shut down development of the OmegA rocket after losing the military launch procurement.

And now ULA will leave SLC-6 after the final Delta 4-Heavy launch from the West Coast spaceport.

“SLC-6 has done us well,” Titus said. “I think that everyone here at Vandenberg has a warm spot in their heart for that place, and we’re going to make sure that it’s continued to be utilized. What we don’t know is exactly what that’s going to look like. But I can say that, first of all, we’re working closely with ULA to make sure that we have a smooth transition. And secondly, there are many other launch service providers out there that could find utility in that location. There’s a lot of infrastructure there. So I’m fairly confident that it will be utilized. We just don’t know exactly how yet.”

ULA’s other launch pad at Vandenberg, Space Launch Complex 3-East, will be converted to support flights of the new Vulcan Centaur rocket in the next few days. SLC-3E is currently used to launch Atlas 5 rockets, and the final Atlas 5 flight from Vandenberg is scheduled for Nov. 1.

Like the Delta rocket family, the Atlas 5 will be retired in the coming years for replacement by the Vulcan. The final Atlas 5 missions will be based out of Cape Canaveral.

Gary Wentz, ULA’s vice president of commercial and government programs, said the company chose the SLC-3E launch pad for the Vulcan rocket over SLC-6 for a few reasons. One was the similarity between the Atlas 5 rocket and the Vulcan, which both use Centaur upper stages, the same payload shroud design, and the same type of solid rocket boosters.

Another reason was that SLC-6 is more expensive to maintain, and ULA is seeking to reduce costs to compete with SpaceX for military launch contracts. SLC-6 has the largest footprint of any launch site at Vandenberg, and is on a similar scale to NASA’s two Apollo-era launch pads at Kennedy Space Center — pads 39A and 39B.

SLC-6 has a 325-foot-tall Mobile Service Tower used to help stack and protect rockets on the pad, a structure originally built for the Manned Orbiting Laboratory program. There’s also a 270-foot-tall Mobile Assembly Shelter that dates back to the 1980s for space shuttle missions. Both buildings move on rail tracks.

Wentz said ULA will “safe and secure” the launch pad after the final Delta 4-Heavy launch Saturday, ensuring that all hazardous systems to sit in an “idle condition” until officials decide what to do next with SLC-6.

There are no immediate plans to demolish any of the structures at SLC-6, and ULA will turn over responsibility for the pad back to the Space Force, which will try to find a new tenant for the pad. Until then, officials don’t expect any significant changes to the site.

ULA will not lay off any of its workforce at Vandenberg, Wentz said. Instead, the workers will transition to ready for the final Atlas 5 launch at the West Coast spaceport, then prep for Vulcan missions.

“From a workforce perspective, the team is upbeat,” Wentz said. “There’s no concern about their future. We’re not in a position where we’re stepping down and going to have to lay off folks. So there are folks that are sticking around to launch these vehicles.”

Startup launch companies like Firefly Aerospace and Relativity Space have signed agreements with the Space Force to fly their small satellite boosters from Vandenberg. SpaceX currently leases a launch pad at Vandenberg for Falcon 9 rocket missions, and ULA will continue using SLC-3 for the Atlas 5 and Vulcan rockets. Another small launch pad, SLC-8, has at least one more space launch on its schedule — a Northrop Grumman Minotaur 4 rocket set to take off in 2023.

“The way that I think we envision this working is that once we identify who’s interested in taking over SLC-6, then we’ll work with them to understand what they want to do in order to facilitate launching whatever type of booster they have,” Titus said.

“Once we identify who it’s going to be, we’ll probably look at the current state of the infrastructure, identify some things that I think would be value-added, maybe some things that don’t need to be there anymore, and then that company will probably go through the same process that ULA went through 15 or 20 years ago when they took a pad that was designed for the space shuttle, and converted it to a pad that supports a Delta launch vehicle,” Titus said.

“So it’s really going to be up to the commercial provider to decide what changes they want to make, but we’ll be there to support and enable that in any way possible.”

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Follow Stephen Clark on Twitter: @StephenClark1.