Spaceflight Insider

Fantastic Four: Most powerful version of Atlas V sends MUOS-4 aloft

United Launch Alliance ULA Atlas V 551 rocket lifts off from Cape Canaveral Air Force Station's Space Launch Complex 41 (SLC-41) in Florida with Mobile User Objective System MUOS-4 satellite photo credit Mike Deep SpaceFlight Insider

Photo Credit: Mike Deep / SpaceFlight Insider

CAPE CANAVERAL, Fla — Residents along Florida’s Space Coast were provided with an extra special ‘wake up call’ this morning, when at 6:18 a.m. EDT (10:18 GMT) at about a quarter of the way through a launch window that extended some 44 minutes. The early morning flight created an array of colors that were painted across the sky as the rocket’s plume greeted the dawn of a new day.

This morning’s launch saw the fourth Mobile User Objective System (MUOS) satellite be sent to orbit. The launch site was Cape Canaveral Air Force Station’s Space Launch Complex 41 (SLC-41) in Florida. The launch team at the Cape had to stare down Tropical Storm Erika earlier in the week to get the booster and its precious cargo ready to be flown off of the launch pad.

Conditions for this morning’s launch were very close to perfect with mostly clear skies and a light breeze. Weather predictions provided a 70 percent chance of favorable conditions to support the launch. The threat posed by Erika never materialized (which caused the launch to slip two days from the planned August 31 liftoff), with the storm dissipating on August 29-30. While the storm was responsible for the deaths of 20 people in the Caribbean nation of Dominica, Florida only saw some rain from the fifth named storm of the 2015 hurricane season.

“The Atlas V system was designed to safely withstand conditions of up to 60 knots or about 69 miles per hour winds, which are just under those presented by a Category 1 hurricane,” said United Launch Alliance’s Vice President of Atlas and Delta Programs Jim Sponnick.

United Launch Alliance Atlas V 551 Mobile User Objective System MUOS-4 mission at Cape Canaveral Air Force Station Space Launch Complex 41 in Florida. Photo Credit: Michael Howard / SpaceFlight Insider

The Atlas V 551 with MUOS-4 was rolled out to the launch pad at 8:35 a.m. EDT (12:35 GMT) on Monday, August 31, 2015. Photo Credit: Michael Howard / SpaceFlight Insider

While this morning’s flight might have seemed routine, it was, in fact, no small feat in that, according to ULA, the MUOS spacecraft are the heaviest satellites that the firm’s Atlas V boosters have sent to orbit. Weighing in at 7.5 tons (6,740 kg) the MUOS satellites required the 551 version of the rocket, which is capable of unleashing an estimated 2.5 million pounds-force (11.12 MN) of thrust.

While impressive, this morning’s launch is something that is a somewhat regular occurrence along Florida’s Space Coast. However, the fact that the flight was pushed back some 11 minutes, it underscored that mission managers wanted to ensure that everything was “nominal” prior to liftoff.

“The first three MUOS spacecraft all launched from here at the Cape, safely and reliably, being a part of this fourth launch is something that we at the 45th Space Wing takes great pride in,” said Lt. Col. Tom Ste. Marie, Air Force 45th Operations Group Deputy Commander. “This is already shaping up to be one of the busiest years here at the Eastern Range; MUOS-4 is the thirteenth of 25 launches currently on our 2015 launch manifest here on the Cape.”

On August 10, the MUOS-4 spacecraft was buttoned up inside the payload fairing or “PLF” in preparation for flight. This critical piece of hardware is produced in Zurich, Switzerland, by RUAG Space; the fairing shielded the MUOS spacecraft as it thundered through Earth’s atmosphere on its way to orbit.

The full stack of launch vehicle and spacecraft were rolled out to the launch pad at SLC-41 at 8:35 a.m. EDT on Monday, Aug. 31.

As noted, ULA utilized the most powerful version of the aerospace firm’s Atlas booster, the 551, to get the mission underway. The nomenclature details the key distinguishing features of the launch vehicle. The first number five is for the five-meter payload fairing that shielded the MUOS spacecraft through Earth’s turbulent atmosphere; the next number five denotes the five Aerojet Rocketdyne AJ-60A solid rocket boosters mounted onto Atlas’ first stage. The final number represents the single engine in the Centaur upper stage of the rocket.

The Atlas V employs the Russian-made RD-180 rocket engine in its first stage. A common mistake is that the Atlas V actually has two engines in its first stage, but there is only the single RD-180 – and two thrust nozzles. Designed and built by NPO Energomash, the RD-180 uses liquid oxygen and RP-1 (a highly-refined version of kerosene).

At T–0, the RD-180 roared into life, and within 1.1 seconds had, along with the five solid boosters, begun pushing that rocket and its payload into the skies.

At about 3.8 seconds into flight, a Pitch/Yaw maneuver began, placing the rocket on the correct heading. With less than a minute of elapsed time, the Atlas booster had crossed into the region known as maximum dynamic pressure or “max-Q” – where the rocket is placed on the greatest amount of stress during the flight.

United Launch Alliance ULA Atlas V 551 rocket lifts off from Cape Canaveral Air Force Station's Space Launch Complex 41 (SLC-41) in Florida with Mobile User Objective System MUOS-4 satellite photo credit Mike Deep SpaceFlight Insider

After painting a streak across the sky, the Atlas V’s plume opened like a flower. Photo Credit: Mike Deep / SpaceFlight Insider

Their fuel mostly spent, SRB’s 1 and 2 were jettisoned one minute and 46 seconds after liftoff. With boosters 3, 4, and 5 falling away about two seconds later.

Three minutes and 22 seconds into the mission, the five-meter PLF split, revealing MUOS-4 to space. The two halves of the fairing, like the five SRBs earlier, then fell back to Earth. The Centaur forward load ejector was jettisoned five seconds later.

Atlas booster engine cutoff (BECO) took place approximately four minutes and 23 seconds after the Atlas had left the pad. Staging between Atlas’ core stage and the Centaur upper stage took place six seconds later.

At four minutes and 39 seconds, the Centaur upper stage was activated in the first of three planned burns scheduled for Centaur. It lasted some seven minutes and 45 seconds.

The second time Centaur fired to life, a little more than twenty minutes after launch, it remained active for about five minutes and 39 seconds.

The final burn took place two hours and 29 minutes after MUOS-4 had left the pad and last for just 58 seconds. Three minutes and 39 seconds later, spacecraft separation occurred. The satellite’s perigee is some 2,062 nautical miles (3,819 km) with its apogee at 19,322.92 nautical miles (35,784 km); it now resides at an orbital inclination of 19.11 degrees and a flight azimuth of 94.58 degrees.

With the completion of this mission, United Launch Alliance now has four more missions on its 2015 launch manifest. They do not work alone, however. Any launch is a complex symphony of individuals and organizations working together to carry out these flights.

“The team is comprised of operators, engineers, maintainers, analysts, weather forecasters, and scientists [and] are all work[ing] through a series of rigorous rehearsals, readiness reviews, and pre-operational checkouts before one of these boosters is launched,” Lt. Col. Marie said.

The MUOS fleet still has one more launch before the system can be deemed complete. The flight of the MUOS-5 spacecraft is an on-orbit spare that is currently planned for an early 2016 launch. If everything continues to go as advertised, the full MUOS network should be operational by 2017.

Produced by Lockheed Martin, MUOS is being fielded so as to provide soldiers, airmen, and sailors at points across the globe with clear communications services comparable to those of the smartphones used by civilians.

MUOS is a tactical communications system, flown to provide secure, seamless voice, video, and mission data transmission from points across the globe, including the Arctic and Antarctic regions. MUOS will continue to support legacy Ultra-High Frequency systems that are already on orbit – but with significant improvements.

MUOS should provide 10 times increased communications capacity over these older systems in that this new system will grant coverage beyond the footprint of any one satellite, linking users across the globe with beyond line-of-sight communications.

The MUOS-4 satellite has a 46-foot (14-meter) diameter reflecting mesh antenna which will be used to relay talk, text, and other forms of data to any other MUOS user. More than 55,000 radio terminals presently in use can now be switched over to the MUOS – with most just needing a software upgrade.

“This marks the sixth flight of the 551 configuration of the Atlas booster… ULA is very proud to be able to send this payload aloft to aid the men and women serving to protect our freedoms,” Sponnick said.

This launch will probably be less-remembered for the payload it carried and more for the amazing art that it painted across the early morning skies. The plume itself caught the light of the early-morning Sun, producing eerie, yet beautiful noctilucent clouds. As the booster arced over the horizon the plume closest to the booster formed the appearance of a jellyfish with the fading flames of the tumbling SRBs twinkling from inside.

The sixth Atlas V 551 lifts of from Cape Canaveral's Space Launch Complex 41 in Florida with MUOS-4. Photo Credit: Jared Haworth / SpaceFlight Insider

This morning’s launch marked the sixth flight of the 551 version of the Atlas V booster. Photo Credit: Jared Haworth / SpaceFlight Insider


Jason Rhian spent several years honing his skills with internships at NASA, the National Space Society and other organizations. He has provided content for outlets such as: Aviation Week & Space Technology,, The Mars Society and Universe Today.

⚠ Commenting Rules

Post Comment

Your email address will not be published. Required fields are marked *