ULA to set rocket endurance record on next launch – Spaceflight Now


An Atlas 5 rocket stands on launch pad 41 before the STP-3 mission. Credit: United Launch Alliance

The United Launch Alliance’s Atlas 5 rocket will set an endurance record after liftoff from Cape Canaveral on Tuesday, targeting the delivery of two US military technology demonstration satellites directly into a geosynchronous orbit more than 22,000 miles above the sea. ‘equator.

The Atlas 5’s Centaur upper stage, powered by an Aerojet Rocketdyne RL10 engine, will maneuver the two Space Force satellites into a geosynchronous orbit with a sequence of three rockets burned in six and a half hours.

The two satellites host a set of prototypes and technological experiments. Military engineers will test their suitability for use on future operational space missions.

The launch is sponsored by the Army Space Testing Program, which oversees many of the Department of Defense’s experimental space missions. The larger of the Atlas 5 rocket’s two satellites, named STPSat 6 and built by Northrop Grumman, houses a NASA laser communications experiment and a payload for the National Nuclear Security Administration designed to detect nuclear detonations to verify the respect for international treaties.

The military did not disclose details of other experiences on the mission, but officials said they would typically test technologies related to space domain knowledge, space weather monitoring and communications.

A carpool satellite named Long Duration Propulsive ESPA, or LDPE 1, is also in orbit on the Atlas 5 rocket. It is mounted on the rocket under STPSat 6 inside the 17.7-foot payload shroud (5. 4 meters) in diameter.

LDPE 1 is hosting its own technological experiments, and will have its own propulsion system to maneuver in space. The spacecraft is capable of launching small satellites into orbit. When asked, military officials did not confirm whether the LDPE 1 spacecraft’s experiments included small deployable satellites.

The mission is scheduled to begin with a liftoff from Launch Pad 41 of the Cape Canaveral Space Station at 4:04 a.m. EST (0904 GMT) on Tuesday, opening a two-hour launch window.

The destination? An almost circular geosynchronous orbit along the equator.

Most satellites heading for such an orbit are deposited in an egg-shaped transfer orbit. This requires the spacecraft to use its own propulsion resources to circularize to an operational altitude above the equator.

Some launches deploy their satellites directly into geosynchronous orbit. ULA’s Atlas 5 and Delta 4 rockets have already accomplished this feat, but launch on Tuesday will set a new record with the Centaur top stage.

“This is a very complex orbital insertion that requires three Centaur burns and precise navigation, an ability unique to the Atlas t. This is our longest mission to date at seven hours and 10 minutes until the final separation of the spacecraft, ”said Gary Wentz, ULA vice president of government and business programs.

The STP-3 mission launch schedule. Credit: United Launch Alliance

ULA’s 196-foot-tall (59.7-meter) Atlas 5 rocket will fly in its most powerful configuration with five strap-on solid rocket thrusters clustered around the bottom of the first stage.

The solid fuel thrusters will provide the majority of the 2.6 million pounds of thrust to lift the Atlas 5 launcher off the platform onto a path east of Cape Canaveral. A kerosene RD-180 engine will power the first stage core.

The mission will mark the 90th flight of an Atlas 5 rocket since 2002, and the 12th in the “551” configuration with five solid rocket thrusters and a 5.4 meter (17.7 feet in diameter) payload fairing.

All five boosters will consume their prepackaged solid fuel in under two minutes, then slack off to drop into the Atlantic Ocean. The Atlas 5 payload fairing will release three and a half minutes after take-off, and then the RD-180’s main engine will shut down four and a half minutes after the start of flight.

The Centaur top stage RL10 engine will ignite for six minutes to reach a parking orbit, then re-ignite for another six minute burn at T + plus 1 hour, 7 minutes, to begin the process of increasing fuel. STP-3 payloads for higher altitude.

A third and final Centaur maneuver is expected to begin at about T + plus 6 hours 25 minutes, to steer the STP-3 payloads into their targeted circular orbit above the equator at an altitude of about 22,400 miles (36,100 kilometers).

This distance is just above geostationary altitude, where satellites orbit the Earth at the same rate of rotation of the planet. STPSat 6 will set up in a parking spot within visibility of the Americas and the Pacific Ocean, while the destination and final orbital position of LDPE 1 have not been disclosed by Space Force.

ULA says the Atlas 5 mission has several firsts.

One of them is the first flight of a 5 meter payload composite fairing produced using a new manufacturing process called “out of autoclave”, a simpler method of hardening carbon fiber. which saves money, time and weight. The payload fairing resembles the previous Atlas 5 nose cones and was produced by the Swiss company RUAG Space, the same company that built the fairings for the previous Atlas 5 missions.

But the non-autoclave shroud was manufactured by RUAG at a new manufacturing facility located at ULA’s rocket factory in Decatur, Alabama. RUAG’s previous Atlas 5 fairings were built at the company’s production site in Switzerland, alongside similar composite shrouds for the European Ariane 5 rocket.

ULA’s next-generation Vulcan rocket will use the same payload fairing design. The company, a 50-50 joint venture between Boeing and Lockheed Martin, is keen to gain flight experience with the fairing ahead of the Vulcan’s first test launch next year.

The STP-3 mission is also launching an in-flight power system, according to ULA, which will provide electricity to the batteries of the STPSat 6 and LDPE 1 satellites during the long climb to their deployed altitude. The system will ensure that the spacecraft will have fully charged batteries when it separates from the Centaur upper stage, according to the ULA.

There’s also a GPS-enhanced navigation capability that makes its maiden flight on mission STP-3, allowing the Centaur to more accurately inject its passenger satellites into their targeted orbits.

ULA is also piloting a new gyroscope unit, a cheaper and lighter alternative to a previous system that uses commercial inertial measurement units in the rocket guidance system.

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