United Launch Alliance (ULA) has successfully sent NASA’s long-awaited Perseverance rover and Ingenuity helicopter on a 203-day trek across the inner Solar System to begin America’s next chapter of Mars exploration. Liftoff of the mighty Atlas V 541 booster—a near-identical version of which totally creamed one of AmericaSpace’s remote cameras when it launched a previous mission in March 2018—took place at 7:50 a.m. EDT Thursday, right on the opening of a two-hour “window”.
“With the launch of Perseverance, we begin another historic mission of exploration,” said NASA Administrator Jim Bridenstine. “This amazing explorer’s journey has already required the very best from all of us to get it to launch through these challenging times. Now we can look forward to its incredible science and to bringing samples of Mars home even as we advance human missions to the Red Planet. As a mission, as an agency, and as a country, we will persevere.”
A little less than an hour after launch, following an initial kick off the planet by the Atlas’ Common Core Booster (CCB) and a pair of eight-minute “burns” by its Centaur upper stage—the first of which achieved Earth-parking orbit, the second of which inserted the payload onto an Earth-escape hyperbolic trajectory—Perseverance is now en-route to Mars. It is due to arrive at the Red Planet on 18 February 2021, landing at the geologically-rich Jezero Crater size via a complicated mechanism of supersonic parachute, rocket-powered SkyCrane and some pretty high-tech guidance wizardy.
“Thank you to the ULA team and our NASA mission partners for diligently working through an ever-changing environment to successfully launch this historic mission,” said Gary Wentz, ULA vice president of Government and Commercial Programs. “The complexity of the Mars 2020 mission proves ULA’s acceptance of the most challenging launch requirements and we work together with NASA to achieve them. Our guidance accuracy for interplanetary missions is unmatched, and the Atlas V is the only vehicle certified to launch payloads with nuclear power sources.”
Flying with a 17-foot-diameter (5-meter) Short Payload Fairing (SPF), together with four solid-fueled boosters and a single-engine Centaur upper stage, the 541 pummeled historic Space Launch Complex (SLC)-41 at Cape Canaveral Air Force Station, Fla., with over 2.3 million pounds (1.1 million kg) of thrust at T-0. The 541, which was flying for its seventh time, is nicknamed “The Dominator” by ULA CEO Tory Bruno, on account of “its beefy power”.
Encased snugly in its cruise stage for the outbound voyage, Perseverance is due to land at the geologically-rich Jezero Crater, just north of Mars’ equator, on 18 February 2021. Its basic mission on the surface is expected to run for at least one Martian “year”, equivalent to 687 Earth-days.
As detailed in AmericaSpace’s recent Perseverance preview article, with Part 1 available here and Part 2 available here, this latest U.S. mission to the Red Planet can trace its heritage back almost eight years and in appearance the 2,300-pound (1,025 kg), six-wheeled rover is not unlike its predecessor, Curiosity, which has been exploring the environs of Gale Crater and Mount Sharp since August 2012. And like Curiosity, Perseverance will be delivered to the surface of Mars by means of a supersonic parachute and rocket-powered SkyCrane.
Equipped with a battery of seven scientific instruments, provided by investigators from the United States, Norway, France, Spain and Denmark, it aims to sniff out the “biosignatures” of past life, collect and “cache” soil and rock specimens for a future sample-return mission, investigate the local geology of Jezero Crater—thought to be the site of an ancient lake—and derive a more comprehensive understanding of Mars’ dust-driven weather. It will also deploy Ingenuity, the first helicopter ever used on another world.
The rover and its associated hardware were airlifted from March Air Reserve Base, near Riverside, Calif., to Cape Canaveral Air Force Station, Fla., back in February, aboard an Air Force C-17 Globemaster. Once on the Space Coasts, its flight wheels were installed and it underwent balance and center-of-gravity tests, ahead of stacking, encapsulation in its payload shroud and integration into the Atlas V fairing.
Meanwhile, the Centaur upper stage arrived in Florida by truck from ULA’s Decatur, Ala., facility in April, followed in short order by the Common Core Booster (CCB) aboard an Antonov An-124-100 airlifter in May. The four solid-fueled boosters were then attached around its base.
As is customary for missions with narrow “launch windows”, the Atlas V was put through a Wet Dress Rehearsal (WDR) last month, in which the ULA, NASA and contractor teams practiced the entire countdown, including fueling the booster with 25,000 gallons (113,650 liters) of rocket-grade kerosene (known as “RP-1”) and 66,000 gallons (300,000 liters) of liquid oxygen and hydrogen. At the completion of the WDR, the cryogens were drained, but the RP-1 remained in the Atlas V tanks through launch day.
The original launch window for Perseverance extended from 17 July through 11 August, although a crane controller fault and contamination issues forced a couple of slippages, firstly to 20 July, then the 22nd and finally the 30th. Encapsulated in her Short Payload Fairing (SPF), Perseverance was hoisted atop the Atlas V on 7 July, topping-out the stack at 197 feet (60 meters) tall.
Sailing through her Flight Readiness Review (FRR) last week and a Launch Readiness Review (LRR) on Monday, all was set for Thursday’s liftoff. With the bulbous SPF in place, the “Mighty Atlas” looked comically top-heavy as she rolled the quarter-mile (400 meters) from the Vertical Integration Facility (VIF) to the SLC-41 pad surface on Wednesday.
Upon reaching the pad, she was carefully centered and propellant umbilicals and electrical and data connections were established. The track mobiles from the Mobile Launch Platform (MLP) were removed and countdown operations commenced late Wednesday evening.
“Seems like a good day to go to another planet,” tweeted Mr. Bruno in the small hours of Thursday morning, as launch crews came on-station to their consoles in the Atlas Spaceflight Operations Center. Gaseous nitrogen flow was initiated to the Atlas V, ahead of fueling. With weather conditions still holding at 80-percent-favorable—and southerly winds of six to eight knots—the first of two built-in holds began at T-2 hours.
Finally, at 5:18 a.m., ULA Launch Conductor Scott Barney and ULA Launch Director Bill Cullen issued a definitive “Go” to proceed with cryogenic loading. Liquid oxygen began being pumped into the Centaur at 5:30 a.m. and into the CCB shortly before 6 a.m. And liquid hydrogen tanking into the Centaur commenced a few minutes later.
Fueling was complete by 7 a.m. as cryogens entered “topping” mode through the remainder of the count. Hitting T-4 minutes at 7:16 a.m. EDT, the countdown halted, as planned, for the second built-in hold, critically timed to last 30 minutes and provide additional time to handle unexpected obstacles. Throughout this final hold, weather balloon data returned a clear “Green” indication for upper-level winds and conditions were reassuringly calm, quiet and unruffled in the ASOC. Shortly before emergence from the hold at 7:46 a.m., the final polls were completed and Mr. Cullen gave permission for the launch to proceed.
The Atlas V CCB’s Russian-built RD-180 engine roared to life at T-2.7 seconds and quickly ramped up full power. At zero, the four solids ignited, punching the Dominator off the pad with more than 2.3 million pounds (1.1 million kg) of thrust. Passing Mach 1 at 35 seconds into flight, the Atlas V experienced maximum aerodynamic turbulence—“Max Q”—on its airframe. The four solids expended their propellant and were jettisoned at 109 seconds into the climb, leaving the RD-180 burning hot and hard and nearly tripling the vehicle’s velocity by the time it too shut down at 4.5 minutes after launch.
By this time, high above the “sensible” atmosphere, the SPF was discarded, exposing Perseverance (snugly tucked away inside its protective cruise stage and backshell) to the space environment for the first time. Following the jettison of the CCB, the stack now weighed less than five percent of what it did at T-0. It coasted for ten seconds, before the Centaur’s RL-10C restartable engine ignites with a thrust of 21,300 pounds (9,600 kg).
It burned for a little under seven minutes to achieve orbital velocity, then entered a half-hour “coasting phase”, ahead a second Centaur burn. This lasted for eight minutes and pushed the Perseverance stack out of Earth orbit at a velocity in excess of 26,000 mph (42,000 km/h) and onto a hyperbolic trajectory to Mars.
Five minutes after the Centaur fell silent for the second time, and some 57 minutes after leaving the Space Coast, Perseverance was separated from the stack and its long, lonely voyage through the inner Solar System commenced in earnest.
On 18 February of next year, the rover will reach its destination and begin a hazardous “Seven Minutes of Terror” as it is guided towards the Jezero Crater landing site by means of a supersonic parachute, a rocket-propelled SkyCrane and an old-fashioned pinch of good fortune. But the experience of landing Curiosity in Gale Crater has also led to refinements and the development of new technologies. Perseverance’s Entry, Descent and Landing (EDL) design architecture should enable mission planners to reduce the size of the “landing ellipse” by over 50 percent, thus zeroing-in on the targeted landing point with greater accuracy than ever before.
Firstly, the Range Trigger will deploy Perseverance’s supersonic parachute with split-second timing, dependent upon where it is in relation to the targeted landing site. If it looks as though the incoming spacecraft will overshoot the target, the Range Trigger will deploy the parachute earlier. Conversely, if it appears that Perseverance will fall short of the landing spot, the trigger will activate parachute deployment slightly later.
It is hoped that the Range Trigger technology will enable trajectory specialists to “slam-dunk” the rover within a couple miles of where it needs to be. And this carries the potential to shave off a significant chunk of time that would otherwise be necessary to drive to key work sites.
Perseverance is also getting help from the skies above Mars, thanks to the data-relay and imaging capabilities of its “buddies” already circling the Red Planet. These will allow detailed Terrain-Relative Navigation maps of the landing site to be derived. As the rover descends beneath its parachute it will acquire photographs of the fast-approaching surface, comparing landmarks with images in its on-board map and even changing direction to avoid hazards.
And we humans will get a front-seat view of the action, thanks to a battery of cameras, microphones and other sensors as Perseverance descends in perhaps the riskiest part of its mission to actually land on Mars.