Strongest Atlas V to give Air Force rare direct ride to high orbit

Florida Today

Nicknamed the “bruiser,” United Launch Alliance’s most powerful Atlas V on Saturday evening will attempt a long, complex mission showcasing both force and finesse.

At 7:13 p.m., about a half-hour before sunset, five solid rocket boosters strapped to the first stage will ignite to help the 197-foot rocket vault from Cape Canaveral Air Force Station with more than 2.5 million pounds of thrust.

That will start a nearly seven-hour mission that, after three burns by the upper stage engine, aims to drop an Air Force communications satellite and experimental payloads directly into orbits 22,300 miles above the equator.

It’s a rare trick for a rocket to perform; satellites bound for similar orbits typically must use their own engines to reach their final destination after deploying from a rocket, a process that could take days or months.

“It’s very special to do a directly inserted geosynchronous orbit, and very, very rare," said ULA CEO Tory Bruno. “There’s a lot more unique technology involved. There are more things that have to go right. So the inherent risk is definitely higher than a less complex orbit.”

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The weather forecast is favorable for the first of what could be two launches in three days from the Space Coast, with a SpaceX Falcon 9 targeting a 6:32 p.m. Monday liftoff with a NASA science mission.

The Air Force predicts an 80 percent chance of conditions meeting launch rules during Saturday's nearly two-hour window.

Perched on top of the Atlas V rocket is a satellite whose identity the Air Force revealed just a week ago, called Continuous Broadcast Augmenting Satcom, or CBAS.

An adapter ring supporting the satellite also will be deployed as an experimental spacecraft called Eagle, carrying a group of technology demonstration missions run by the Air Force Research Laboratory.

The Air Force shared few details about the satellites, including how much they weigh, but the big rocket referred to as a “551” offers a hint.

“The spacecraft that would ask for an Atlas 551 is heavy,” said Bruno.

The Atlas booster and the first burn by the Centaur upper stage’s RL-10C engine will position the rocket in what is known as a parking orbit circling the planet roughly 1,200 miles up.

A second Centaur burn will boost the trajectory into an egg-shaped “transfer orbit” climbing as high as the final orbit needs to be.

That’s when a typical launch of a commercial communications satellite bound for geosynchronous orbit — where spacecraft appear to hover over fixed places on the ground — usually ends, after as little as 35 minutes.

Then it’s up to the satellites to use their own propulsion to circularize their orbits and steer themselves toward the equator, flattening the angle they started at from Cape Canaveral.

But during Saturday’s mission, the Atlas V rocket will do all the work to perform a “direct insertion” of the spacecraft into their final orbits.

“You just go right to your destination orbit, the rocket carries you there,” said Bruno. “But there’s very few rockets in the world that have that capability.”

To get there, the second Centaur burn will be followed by a roughly five-hour coast — a potentially treacherous phase in which certain propellants, like the kerosene fuel SpaceX Falcon rockets use, might freeze if not properly insulated or heated.

“If you want to still be alive on the other end of that coast five hours later, to do that final burn that is the thing that makes it a direct injection, now it gets tough,” said Bruno. “If there’s big chunks of Ice in the propellant tank, you’re in trouble."

The Centaur avoids that problem by using super-cold or “cryogenic” liquid hydrogen and liquid oxygen, which continue to boil off even in the frigid temperatures of space.

Larger-than-usual batteries also keep electronics and valves running throughout the long-duration flight. Precise navigation is another key piece of technology needed for the rocket to end up in the right place more than 20,000 miles above Earth, Bruno said, as compared to a much shorter flight.

Being off by a few degrees on any engine burn “can translate to many, many miles off of the bull’s eye,” he said.

Bruno estimated that about a dozen of ULA’s 126 missions to date have placed missions directly into such a high orbit.

"It takes more than a big rocket to pull off that kind of orbit," he said. “This orbit is more about the finesse.”

Contact Dean at 321-242-3668

or jdean@floridatoday.com.

Twitter: @flatoday_jdean

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Launch Saturday

Rocket: United Launch Alliance Atlas V (551 configuration)

Mission: Air Force Space Command-11 (AFSPC-11)

Launch Time: 7:13 p.m.

Launch Window: to 9:11 p.m.

Launch Complex: 41 at Cape Canaveral Air Force Station

Weather: 80 percent “go”

Join floridatoday.com at 6 p.m. for countdown chat and updates, including streaming of ULA’s launch webcast starting 20 minutes before liftoff, at 6:53 p.m.

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System requirements list:

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Android's AR capabilities are limited to specific models running 7.0 Nougat and later. See the full list at developers.google.com/ar/discover/.