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The ultimate flight of United Launch Alliance’s Delta IV Heavy rocket took off Tuesday from Cape Canaveral, Florida, with a labeled spy satellite tv for pc for the Nationwide Reconnaissance Workplace.

The Delta IV Heavy, one of many world’s strongest rockets, launched for the sixteenth and last time Tuesday. It was the forty fifth and final flight of a Delta IV launcher and the ultimate rocket named Delta to ever launch, ending a string of 389 missions courting again to 1960.

United Launch Alliance (ULA) tried to launch this rocket on March 28 however aborted the countdown about 4 minutes previous to liftoff resulting from hassle with nitrogen pumps at an off-site facility at Cape Canaveral. The nitrogen is important for purging elements contained in the Delta IV rocket earlier than launch, decreasing the chance of a hearth or explosion in the course of the countdown.

The pumps, operated by Air Liquide, are a part of a community that distributes nitrogen to totally different launch pads on the Florida spaceport. The nitrogen community has precipitated issues earlier than, most notably in the course of the first launch marketing campaign for NASA’s Area Launch System rocket in 2022. Air Liquide didn’t reply to questions from Ars.

A flawless liftoff

With an answer in place, ULA gave the go-ahead for an additional launch try Tuesday. After a easy countdown, the ultimate Delta IV Heavy lifted off from Cape Canaveral Area Power Station at 12:53 pm EDT (16:53 UTC).

Three hydrogen-fueled RS-68A engines made by Aerojet Rocketdyne flashed to life within the last seconds earlier than launch and throttled as much as produce greater than 2 million kilos of thrust. The ignition sequence was accompanied by a dramatic hydrogen fireball, an indicator of Delta IV Heavy launches, that singed the underside of the 235-foot-tall (71.6-meter) rocket, turning a patch of its orange insulation black. Then, 12 hold-down bolts fired and freed the Delta IV Heavy for its climb into area with a top-secret payload for the US authorities’s spy satellite tv for pc company.

Heading east from Florida’s Area Coast, the Delta IV Heavy appeared to carry out properly within the early phases of its mission. After fading from view from ground-based cameras, the rocket’s two liquid-fueled aspect boosters jettisoned round 4 minutes into the flight, a second captured by onboard video cameras. The core stage engine elevated energy to fireplace for a pair extra minutes. Practically six minutes after liftoff, the core stage was launched, and the Delta IV higher stage took over for a sequence of burns with its RL10 engine.

At that time, ULA minimize the general public video and audio feeds from the launch management middle, and the mission flew right into a information blackout. The ultimate parts of rocket launches carrying Nationwide Reconnaissance Workplace (NRO) satellites are normally carried out in secret.

In all probability, the Delta IV Heavy’s higher stage was anticipated to fireplace its engine not less than 3 times to put the labeled NRO satellite tv for pc right into a round geostationary orbit greater than 22,000 miles (almost 36,000 kilometers) over the equator. On this orbit, the spacecraft will transfer in lock-step with the planet’s rotation, giving the NRO’s latest spy satellite tv for pc fixed protection over a portion of the Earth.

It’s going to take about six hours for the rocket’s higher stage to deploy its payload into this high-altitude orbit and solely then will ULA and the NRO declare the launch a hit.

Eavesdropping from area

Whereas the payload is classed, specialists can glean just a few insights from the circumstances of its launch. Solely the biggest NRO spy satellites require a launch on a Delta IV Heavy, and the payload on this mission is “virtually actually” a kind of satellite tv for pc identified publicly as an “Superior Orion” or “Mentor” spacecraft, in accordance with Marco Langbroek, an knowledgeable Dutch satellite tv for pc tracker.

The Superior Orion satellites require the mix of the Delta IV Heavy rocket’s carry functionality, long-duration higher stage, and large, 65-foot-long (19.8-meter) trisector payload fairing, the biggest payload enclosure of any operational rocket. In 2010, Bruce Carlson, then-director of the NRO, referred to the Superior Orion platform because the “largest satellite tv for pc on the planet.”

When considered from Earth, these satellites shine with the brightness of an eighth-magnitude star, making them simply seen with small binoculars regardless of their distant orbits, in accordance with Ted Molczan, a skywatcher who tracks satellite tv for pc exercise.

“The satellites function a really massive parabolic unfoldable mesh antenna, with estimates of the dimensions of this antenna starting from 20 to 100 (!) meters,” Langbroek writes on his web site, citing data leaked by Edward Snowden.

The aim of those Superior Orion satellites, every with mesh antennas that unfurl to a diameter of as much as 330 toes (100 meters), is to pay attention to communications and radio transmissions from US adversaries, and maybe allies. Six earlier Delta IV Heavy missions additionally doubtless launched Superior Orion or Mentor satellites, giving the NRO a worldwide net of listening posts parked excessive above the planet.

With the final Delta IV Heavy off the launch pad, ULA has achieved a objective of its company technique despatched into movement a decade in the past, when the corporate determined to retire the Delta IV and Atlas V rockets in favor of a new-generation rocket named Vulcan. The primary Vulcan rocket efficiently launched in January, so the previous couple of months have been a time of transition for ULA, a 50-50 three way partnership owned by Boeing and Lockheed Martin.

“That is such an incredible piece of expertise: 23 tales tall, half 1,000,000 gallons of propellant, two and 1 / 4 million kilos of thrust, and probably the most metallic of all rockets, setting itself on fireplace earlier than it goes to area,” Bruno mentioned of the Delta IV Heavy earlier than its last launch. “Retiring it’s (key to) the long run, shifting to Vulcan, a cheaper, higher-performance rocket. However it’s nonetheless unhappy.”

“Every little thing that Delta has finished … is being finished higher on Vulcan, so this can be a nice evolutionary step,” mentioned Invoice Cullen, ULA’s launch techniques director. “It’s bittersweet to see the final one, however there are nice issues forward.”