Following last week’s triumphant debut of the Space Launch System (SLS) from Pad 39B at Florida’s Kennedy Space Center (KSC), the Artemis I Orion spacecraft—now deep inside the lunar sphere of influence—smoothly executed its 150-second Outbound Powered Flyby (OPF) “burn” of the Orbital Maneuvering System (OMS) main engine on its European Service Module (ESM) early Monday morning. This is the first of two planned burns intended to ready the spacecraft for insertion into a highly stable Distant Retrograde Orbit (DRO) around the Moon, where it will remain until the end of November, ahead of its return journey to Earth early next month.
After two scrubbed launch attempts in late August and early September, the 322-foot-tall (98-meter) SLS—the “business end” of which is powered by four shuttle-heritage RS-25 engines on its 212-foot-tall (64.6-meter) Boeing-made Core Stage, together with a pair of five-segment Solid Rocket Boosters (SRBs), fabricated by Northrop Grumman Corp.—took flight at 1:47:44 a.m. EST Wednesday, 16 November. Artemis I lit up the Florida night sky, pounding spectators’ chests and pummeling the soles of many feet with 8.8 million pounds (3.9 million kilograms) of thrust, greater even than Project Apollo’s mighty Saturn V.
As the SLS powered airborne, it instantly catapulted itself into the record-books as the most powerful rocket ever successfully launched. “You got to feel it in your bones,” Artemis Mission Manager Mike Sarafin wryly told a media teleconference on 18 November, adding that “all indications are the system performed spot-on”.
He added that some damage to Pad 39B facilities was incurred, including the “removal” of the elevator blast doors, which required personnel to use the stairs to access the higher levels for their initial post-launch inspections. The rocket’s performance was admirable, the 177-foot-tall (53.9-meter) SRBs delivering 75 percent of the total liftoff thrust to boost the stack to an altitude of 29.9 miles (48 kilometers) and a velocity of 3,170 mph (5,100 km/h) at the point of their separation, two minutes after liftoff.
All told, the Core Stage burned for more than eight minutes, before separating from the stack and impacting in the Pacific Ocean, to the east of Hawaii. This left Orion and its attached 45-foot-tall (13.7-meter) Interim Cryogenic Propulsion Stage (ICPS) alone to execute a pair of critical “burns” to firstly raise the low point (or “perigee”) of its orbital path to enter a circular path around Earth and secondly depart the Home Planet’s gravitational “well” for a multi-day transit to the Moon.
Those burns—a short, 20-second Perigee Raise Maneuver (PRM), then the 18-minute-long Translunar Injection (TLI)—were successfully performed by the ICPS’ RL-10C engine. After this was complete, Orion separated and entered free flight almost two hours after launch.
By this time, the spacecraft’s four solar arrays had been successfully deployed. Orion Vehicle Integration Manager Jim Geffre later noting that they generated more electrical power than anticipated and better-than-expected heat rejection.
Less than eight hours after leaving Florida, Orion’s shuttle-heritage OMS main engine was fired for the first outbound trajectory correction burn, with a second performed by the ESM auxiliary thrusters early on 17 November. Engineers worked to maneuver the spacecraft’s solar arrays to establish optimum positions for the most efficient WiFi imagery transfer rates and activated Lockheed Martin’s Callisto voice-activated and video technology demonstrator inside the Crew Module (CM).
Some 13 “performance funnies” were experienced during launch, notably an issue with Orion’s star trackers, which appear to have been inadvertently dazzled by thruster-plume behavior. Mr. Sarafin explained that the issue did not infringe Artemis I flight rules and the trackers continue to meet all their functionality requirements.
On Sunday, two active anomaly resolution teams were focusing on the star-tracker “funny” and a few instances in which one of eight ESM units responsible for providing solar array power to the CM opened without being commanded. The unit (known as a Power Conditioning and Distribution Unit (PCDU) umbilical latching current indicator) was successfully commanded closed and Orion exhibited no loss of avionics power, with no mission impacts.
On Saturday, three days into the planned 25.5-day mission, NASA managers polled “Go” for Orion to perform its Outbound Powered Flyby (OPF), the first of four major burns to be conducted by the OMS. Around the time that the spacecraft entered the lunar sphere of influence at 2:09 p.m. EST Sunday—the point at which the Moon surpassed Earth in exerting the principal gravitational tug on Orion—another pair of outbound trajectory correction burns fine-tuned the inbound flight profile.
Early Monday, Flight Director Rick LaBrode polled his Mission Control team for their readiness status to execute the 150-second OPF burn. As Orion disappeared behind the Moon and Loss of Signal (LOS) occurred at 7:26 a.m. EST, the spacecraft was 232,000 miles (374,000 kilometers) from Earth and 900 miles (1,500 kilometers) from the Moon.
The OPF burn got underway at 7:44 a.m. EST, deep into LOS and unseen from Earth. Interestingly, the OMS engine—which generated 6,000 pounds (2,700 kilograms) of thrust—is a modified OMS engine from the shuttle era, having supported 19 missions between October 1984 and October 2002.
Thirteen minutes into LOS, at 7:57 a.m. EST, Orion reached its closest point to the Moon, skimming just 81 miles (130 kilometers) above the surface. After 34 nail-biting minutes of communications silence, the spacecraft emerged from behind the lunar limb just before 8 a.m. EST to return an astonishing view of Earth—a tiny blue-and-white marble, 229,000 miles (368,500 kilometers) away—surrounded by a sea of darkness.
It evoked memories of Carl Sagan’s description of the famous “Family Portrait”, taken by the Voyager 1 spacecraft in February 1990. Today’s “blue dot”, admittedly, was a little closer in range, but NASA Public Affairs Officer (PAO) Sandra Jones provided a sobering reminder that eight billion living souls (plus all those who have gone before) live or lived out their lives on this pretty blue speck.
Half an hour after Acquisition of Signal (AOS), Orion passed directly over Apollo 11’s landing site on the Sea of Tranquility, where Neil Armstrong and Buzz Aldrin landed Lunar Module (LM) “Eagle” and first walked on the Moon in July 1969.
With the OPF burn complete, the stage is now set for Orion to enter a highly stable Distant Retrograde Orbit (DRO) later this week. A second OMS burn, known as Distant Retrograde Insertion (DRI), is scheduled for Friday, after which Orion will remain in the DRO for about six days, until the end of November.
This elliptical retrograde path will carry the spacecraft up to 40,000 miles (64,000 kilometers) beyond the Moon and almost 268,500 miles (432,100 kilometers) from Earth at 4:05 p.m. EST on 28 November. This will establish a new record for the furthest any spacecraft capable of carrying humans has ever traveled.
In fact, during its time in the DRO, Orion will travel further beyond the Moon than did Apollo 13, which holds the current record. During their ill-fated mission, way back in April 1970, Apollo 13 astronauts Jim Lovell, Jack Swigert and Fred Haise reached a maximum distance of 248,654 miles (400,170 kilometers) from Earth.