June 23, 2021

SpaceX plans to cap busy week with launch of satellite for SiriusXM


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The SXM 7 radio broadcasting satellite. Credit: Maxar

A massive radio broadcasting satellite for SiriusXM is set for liftoff Friday on top of a Falcon 9 rocket, punctuating a busy week for SpaceX that included the debut of a new-generation cargo ship for the International Space Station and a spectacular atmospheric test flight of a prototype rocket over South Texas.

A Falcon 9 rocket is standing on pad 40 at Cape Canaveral Space Force Station for liftoff at 11:21 a.m. EST (1621 GMT) Friday with SiriusXM’s SXM 7 broadcasting satellite heading for geosynchronous orbit more than 22,000 miles (nearly 36,000 kilometers) over the equator.

The launch window Friday extends until 1:20 p.m. EST (1820 GMT).

There is a 90 percent chance of favorable weather during the nearly two-hour launch window Friday, according to the U.S. Space Force’s 45th Weather Squadron.

“For the primary launch window Friday morning, favorable conditions are expected for launch with light onshore winds bringing the stratocumulus and cumulus deck over the local Atlantic into the coast,” the weather team wrote in an outlook issued Thursday. “There will be only a small threat for this activity to potentially violate the cumulus cloud rule.”

The Falcon 9 rocket’s launch window opens 15 hours, 12 minutes, after a United Launch Alliance Delta 4-Heavy rocket blasted off from pad 37B Thursday night a few miles to the south pad 40.

That would mark the shortest turnaround between two orbital launches from Cape Canaveral since September 1967, when Delta-G and Atlas-Centaur rockets took off within a 10-hour span from separate launch pads, according to a launch log maintained by Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics who tracks global satellite and launch activity.

Last August, a Falcon 9 and an Atlas 5 rocket launched from Cape Canaveral in a period of less than 35 hours. That was the shortest span between two orbital missions at Cape Canaveral since May 1981.

Military officials at the 45th Space Wing have streamlined Eastern Range operations at Cape Canaveral to eliminate bottlenecks and reduce range staffing levels for some missions, such as SpaceX launches that use an automated flight safety system. The safety mechanism would terminate the launch if the rocket flew off course and threatened populated areas.

Rather than requiring as long as 48 hours between launches — as the Eastern Range did in recent decades — the 45th Space Wing says it can now accommodate a SpaceX launch and a ULA flight with less than 24 hours of separation.

A Falcon 9 rocket stands on pad 40 at Cape Canaveral Space Force Station before launch of the SXM 7 satellite. Credit: SpaceX

The launch of SiriusXM’s SXM 7 satellite also caps a busy week for SpaceX.

On Dec. 6, SpaceX launched its first upgraded Cargo Dragon spacecraft from pad 39A at NASA’s Kennedy Space Center. The automated supply ship — sporting upgrades and a new shape based on SpaceX’s human-rated Crew Dragon capsule — arrived at the International Space Station on Monday, Dec. 7, for a successful docking.

Meanwhile, SpaceX teams in South Texas launched a high-altitude test flight of the company’s next-generation Starship vehicle Wednesday. The 164-foot-tall (50-meter) prototype rocket flew to airliner altitudes powered by methane-fueled Raptor engines, then performed a guided descent back toward a landing pad at SpaceX’s test facility in Boca Chica, Texas, near the U.S.-Mexico border.

The Starship rocket performed a dramatic flip maneuver to set up for landing, but the vehicle erupted in a fireball as it made a hard landing. Elon Musk, SpaceX’s founder and CEO, hailed the test flight as a success.

The reusable Starship could eventually carry more than 100 tons of cargo into space, and transport people to the moon, Mars and other deep space destinations.

Amid the company’s other activities earlier this week, SpaceX test-fired the Falcon 9 booster for the SXM 7 mission Monday evening, then transferred the rocket back inside its hangar near pad 40 for attachment of the spacecraft.

The reusable Falcon 9 booster for this mission — designated B1051 — is a veteran of six prior flights to space and back, beginning with a Crew Dragon test launch to the space station last year. SpaceX says one half of the rocket’s clamshell-like payload fairing protecting the SXM 7 spacecraft is also being reused for this mission after recovery following the launch of South Korea’s Anasis 2 military communications satellite earlier this year.

With the fully-assembled rocket back on pad 40, SpaceX technicians were readying the two-stage launcher for propellant loading Friday morning. Kerosene and liquid oxygen propellants are scheduled to begin flowing into the Falcon 9 rocket at 10:46 a.m. EST (1546 GMT).

Assuming no technical issues and good weather, nine Merlin 1D engines will fire up to propel the Falcon 9 rocket off the ground with 1.7 million pounds of thrust at 11:21 a.m. EST.

The Falcon 9 will head downrange toward the east from Cape Canaveral, with the rocket’s first stage booster scheduled to shut down and separate around two-and-a-half minutes into the flight.

The first stage will aim for landing on SpaceX’s drone ship “Just Read the Instructions” parked a few hundred miles east of Cape Canaveral.

The Falcon 9’s second stage will fire two times to place the SXM 7 spacecraft into a parking, then deploy the radio broadcasting payload into an elliptical, or egg-shaped “sub-synchronous” transfer orbit at T+plus 31 minutes, 39 seconds.

The roughly 15,000-pound, or nearly 7-metric ton, spacecraft is loaded with maneuvering propellant to boost itself toward a final perch in geostationary orbit more than 22,000 miles (nearly 36,000 kilometers). In that orbit, the spacecraft will orbit Earth at the same rate the planet rotates, giving SXM 7 a fixed view of the Americas 24 hours a day, seven days per week.

“SiriusXM, the leading audio entertainment company in the United States, will use SXM 7 to ensure continuous and reliable delivery of SiriusXM’s entertainment and data services to tens of millions of subscribers across North America,” Maxar said in a statement. “SXM 7 will deliver the highest power density of any commercial satellite on-orbit, sending more than 8,000 watts of content to the continental U.S., Canada, Puerto Rico and the Caribbean, increasing the quality of signal for SiriusXM subscribers.”

Once in orbit, the SXM 7 satellite — based on Maxar’s 1300-series spacecraft design — will unfurl a large antenna reflector to broadcast radio signals to receivers on moving vehicles.

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Follow Stephen Clark on Twitter: @StephenClark1.


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