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Picture credit score: Jeff Seibert/AmericaSpace
Regardless of the latest ravages of Hurricane Ian, United Launch Alliance (ULA) has efficiently flown a second mission inside ten days, delivering the dual-stacked SES-20 and SES-21 geostationary communications satellites aloft from storied House Launch Complicated (SLC)-41 at Cape Canaveral House Pressure Station, Fla., on behalf of Luxembourg-headquartered SES.
Simply over per week in the past, the ultimate Delta IV Heavy—carrying the categorized NROL-91 payload for the Nationwide Reconnaissance Workplace—took flight from House Launch Complicated (SLC)-6 at Vandenberg House Pressure Base, Calif.
This marks the primary time in additional than 4 years since ULA final attained such a fast back-to-back cadence between missions.
The climate for Tuesday night’s 5:36 p.m. EDT launch was virtually superb. In its L-1 briefing, the forty fifth Climate Squadron at Patrick House Pressure Base predicted an 80-percent likelihood of acceptable circumstances.
“A couple of low-topped showers shifting onshore and low clouds are forecast by way of Tuesday afternoon,” it famous, “with winds remaining breezy from the north. The first concern is the Cumulus Cloud Rule.”
Launch was initially baselined inside a month-long “window” extending from 7 September by way of 7 October. However the precedence of NROL-91 from Vandenberg discovered SES-20/21’s No Earlier Than (NET) date shifted to no earlier than 30 September.
This was pushed again a number of extra days to 4 October because the House Coast braced in opposition to Hurricane Ian. Additionally impacted had been SpaceX Falcon 9 operations in Florida, notably the launch of Dragon Endurance on the Crew-5 mission, which slipped a few days to the correct, selecting a brand new NET of midday EDT Wednesday, 5 October.
Flying solely ten days after NROL-91—albeit from the other coast of the USA—tonight’s mission marks the primary time in additional than 4 years that ULA has performed twin launches inside such a brief span of time.
Again in January 2018, a Delta IV Medium booster rose from Vandenberg on the twelfth of that month, laden with the categorized NROL-47 payload for the Nationwide Reconnaissance Workplace, to be adopted eight days in a while the twentieth by an Atlas V, carrying the fourth geostationary factor of the U.S. House Pressure’s House-Primarily based Infrared System (SBIRS GEO-4).
And the payload for tonight’s mission is being flown on behalf of Luxembourg-based satellite tv for pc communications supplier SES. In the summertime of 2020, ULA received the launch companies contract to move SES-20 and SES-21 to orbit.
It was famous that the Atlas V has the power “to ship each satellites to an advantageous orbit that can dramatically scale back the period of time main as much as the satellites coming into service”. Each SES-20 and SES-21 are anticipated to be declared operational in November.
The 2 satellites every carry ten C-band transponders and are a part of an ongoing effort to speed up SES’ C-band clearing plan to fulfill a Federal Communications Fee (FCC) goal to roll out 5G companies. The arrival of SES-20 and SES-21 facilitates the printed supply of digital tv to over 120 million properties, plus information companies.
To satisfy the FCC deadline of clearing C-band spectrum throughout the USA, SES ordered 4 new satellites—SES-18, SES-19, SES-20 and SES-21—to be delivered into orbit. In June 2020, Northrop Grumman Corp. was chosen to construct SES-18 and SES-19, leveraging its flight-proven GeoStar-3 “bus”, with Boeing chosen to manufacture SES-20 and SES-21 on its all-electric 702SP satellite tv for pc platform.
In August, the 2 satellites arrived on the Cape to be fueled and built-in into the 17.7-foot-diameter (5.4-meter) Brief Payload Fairing (SPF). The SES-20/21 launch marketing campaign formally started in late August, with the Launch Automobile On Stand (LVOS) milestone, when the 107-foot-long (32.6-meter) Atlas V Widespread Core Booster (CCB) was rotated upright within the 30-story Vertical Integration Facility (VIF) at SLC-41.
Three Graphite Epoxy Motors (GEM)-63 solid-fueled boosters had been put in on the base of the Atlas and on 21 September the SPF containing the SES-20/21 “stack” was put in atop the automobile. Totally assembled, the “Mighty Atlas” stood a formidable 196 ft (59.7 meters) tall.
The arrival of Hurricane Ian noticed the automobile safely tucked away contained in the VIF, though a launch on the finish of September proved now not possible and T-0 was correspondingly rescheduled for 4 October. The Launch Readiness Evaluate (LRR) concluded with out incident on Saturday and at 9:59 a.m. EDT Monday the stack started its snail-like creep a quarter-mile (400 meters) from the VIF to the SLC-41 pad floor.
“Mighty Atlas is rolling to the pad with SES-20 and SES-21 at blistering strolling velocity,” tweeted ULA CEO Tory Bruno. “Nearly there.”
Inside two hours, the Atlas V was declared “hard-down” on the pad pedestals. Late Monday, a extremely refined type of rocket-grade kerosene (generally known as “RP-1”) was loaded into the Atlas tanks. Early Tuesday, countdown operations commenced about seven hours previous to T-0, because the climate forecast started trending upward to 90-percent “Go”.
Liftoff at 5:36 p.m. EDT was good, the Atlas V’s single RD-180 engine and the three GEM-63 boosters offering an preliminary thrust off the pad in extra of 1.6 million kilos (725,000 kilograms). The automobile surpassed the velocity of sound about 40 seconds into ascent and at simply shy of a minute after launch entered a interval of most aerodynamic turbulence—recognized colloquially as “Max Q”—on the airframe.
Their propellant exhausted, the three GEM-63s burned out and had been discarded a bit of beneath two minutes into the mission, adopted about 90 seconds later by the jettison of the SPF fairing halves to show the SES-20/21 stack to the area surroundings for the primary time. Shutdown of the RD-180 engine and separation of the CCB happened 4.5 minutes after departing the Cape.
With the widespread core booster thus gone, the flip now fell to the RL10C-1-1 engine of the Centaur higher stage, which was tasked with three discrete “burns” to exactly inject the 2 communications satellites very near their eventual geostationary orbits. The primary burn was timed to final about seven minutes, after which the stack would coasted, previous to a second burn of round 5 minutes.
As this AmericaSpace story was being ready, the third and ultimate Centaur burn was due about 5.5 hours into the mission, with deployment of the SES-20/21 payload stack shortly thereafter. The 2 satellites—with SES-20 on the “high” of the stack and its near-twin beneath—had been attributable to be deployed about 40 minutes aside.
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