United Launch Alliance (ULA) stands ready to deliver NASA’s long-awaited Perseverance rover to Mars on Thursday morning from Cape Canaveral Air Force Station in Florida.
The 197-foot-tall (60-meter) rocket—flying in its “541” configuration with a 17-foot-diameter (5-meter) payload fairing, four solid-fueled boosters and a single-engine Centaur upper stage—was carried the 1,800-foot (550-meter) distance from the Vertical Integration Facility (VIF) to the pad on Tuesday morning, atop the Mobile Launch Platform (MLP). Nicknamed “The Dominator” by ULA CEO Tory Bruno, the powerful 541 will certainly dominate much activity and attention at liftoff, as it sets out on America’s next voyage to the Red Planet.
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Liftoff will occur during a two-hour “window” which opens at 7:50 a.m. EDT Thursday. And thanks to unexpected delays along the way, and what Mr. Bruno described as “clever trajectory design”, this mission promises to fly a pretty nifty 203-day transit to the Red Planet, before it lands the Perseverance rover in geologically-rich Jezero Crater on 18 February 2021.
“Mighty Atlas” has a long heritage of delivering missions to Mars. The workhorse Atlas V previously lofted the Mars Reconnaissance Orbiter in August 2005, the Curiosity rover in November 2011, the Mars Atmosphere and Volatile Evolution (MAVEN) mission in November 2013 and most recently the InSight lander—the first voyage to the Red Planet flown out of Vandenberg Air Force Base, Calif.—in May 2018.
This week’s launch is “arguably the most sophisticated and in some ways the most exciting” of all the missions ULA has launched to Mars, says Bruno.
As detailed in AmericaSpace’s Perseverance preview, the mission to land a rover at the site of a suspected ancient Martian lake promises to uncover tantalizing clues about the planet’s watery past, including potential “biosignatures” of past life.
It will also gather a “cache” of soil and rock specimens for a future sample-return mission, perform experimental In-Situ Resource Utilization (ISRU) work to assess the practicalities of generating pure oxygen from Mars’ carbon dioxide-rich atmosphere, examine the nature of the Red Planet’s dust-driven weather and (for the first time on another world) deploy a small helicopter, Ingenuity, to scout ahead of the rover.
Previously known as “Mars 2020”, the Perseverance mission has been in work for over eight years and draws heavily upon the heritage of its predecessor, the Curiosity rover, which has been exploring Gale Crater since August 2012. But the involvement of ULA in this remarkable voyage officially began in August 2016, when NASA awarded a $243 million contract to the Centennial, Colo.-headquartered launch provider.
In April 2020, the 41-foot-long (12.6-meter) Centaur upper stage arrived at the Cape by road. It will provide two lengthy “burns” of its powerful RL-10C engine to deliver Perseverance firstly into Earth orbit and then onto a trajectory for Mars. A few weeks later, the 107-foot-long (32.6-meter) Common Core Booster (CCB)—the first stage of the Atlas V—also arrived aboard an Antonov An-124-100 airlifter.
In late May, the milestone Launch Vehicle On Stand (LVOS) milestone took place, when the CCB and Centaur arrived in the VIF at SLC-41 and were raised to the vertical and mated together. The four solid-fueled rocket boosters were installed around the base of the CCB, creating a behemoth which will generate almost 2.4 million pounds (1.1 million kg) of thrust at T-0.
Last month, as is customary for missions with critically narrow “launch windows”, the entire stack—minus Perseverance in its Short Payload Fairing (SPF)—was put through a Wet Dress Rehearsal (WDR), in which the entire countdown was practiced in minute detail. This included loading 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 CCB tanks through launch day. Finally, the SPF containing Perseverance was hoisted into the VIF and mounted atop the Atlas V on 7 July.
Originally targeted to fly on the 17th, the mission slipped nearly two weeks due to several technical issues, including a crane malfunction and payload contamination concerns. It sailed through a Flight Readiness Review (FRR) last week and a Launch Readiness Review (LRR) on Monday, which gave the definitive go-ahead for rollout from the VIF to the SLC-41 pad surface on Tuesday morning.
An early-morning weather briefing from Launch Weather Officer Jessica Williams of the 45th Weather Squadron verified conditions were acceptable for the rollout. Shortly after 10 a.m. EDT, a readiness check of systems status was completed and ULA Launch Director Bill Cullen authorized the rollout to begin. “First-motion” of the stack got underway at 10:24 a.m., with undercarriage railcars and trackmobile machines pushing the 1.8-million-pound (800,000 kg) vehicle along the 1,800-foot (550-meter) distance from the VIF to the pad surface. Less than 30 minutes later, it passed the pad’s perimeter fence and was confirmed “hard-down” on the pad surface at 11:23 a.m. EDT.
Already two weeks into an almost-month-long “window” to reach Mars under the most optimum conditions of planetary alignment and energy expenditure, NASA’s Perseverance rover has the weather gods on its side for an on-time liftoff on Thursday morning. Current predictions, courtesy of the 45th Weather Squadron at Patrick Air Force Base, call for an 80-percent probability of acceptable conditions, with a slight improvement in the event of a 24-hour scrub to Friday.
Earlier this week, the mission wrapped up its Launch Readiness Review (LRR) with flying colors. “We are in extraordinary times right now with the coronavirus pandemic,” said NASA Administrator Jim Bridenstine, “and yet we have, in fact, persevered.”
Perseverance will spend 6.5 months in transit to Mars, before it executes a hairy Entry, Descent and Landing (EDL)—guided by a supersonic parachute, rocket-powered SkyCrane and a myriad of other technologies—to alight in the geologically rich Jezero Crater, just north of the Martian equator, on 18 February 2021. It will spend at least one Mars “year”, equivalent to 687 Earth-days, roving an area which might once have harbored a gigantic lake.
Assisted by Ingenuity, the first helicopter ever to be deployed on another world, Perseverance will investigate the possible “biosignatures” of past life, collect a “cache” of soil and rock samples to be brought back to Earth on a future sample return mission, evaluate In-Situ Resource Utilization (ISRU) technologies and derive a better understanding of Mars’ dust-driven weather. And according to NASA Associate Administrator Thomas Zurbuchen, speaking earlier today, it carries with it 11 million names of ordinary people, just like you and me. “Because we’re going together,” Dr. Zurbuchen explained, “as a world.”
Assuming on-time launch Thursday, Perseverance will rise from Earth less than an hour after local sunrise, promising onlookers a spectacular view of the Atlas V as it powers uphill, under a combined 2.4 million pounds (1.1 million kg) of thrust from the Russian-built RD-180 engine of its Common Core Booster (CCB) and four strap-on solid-fueled rockets. “For launch day Thursday, overall conditions are favorable,” added the 45th, pointing to an 80-percent probability of acceptable weather. “However, an isolated shower just offshore and some mid-level clouds along the coast are likely as a weak front off the coast of the southeast sags southward. Therefore, the primary concerns for launch day are the Cumulus Cloud and Thick Cloud Layer Rules.”
A delay to either Friday or Saturday will produce a slightly different T-0, with the window opening five minutes later at 7:55 a.m. EDT. “For Friday morning, the front weakens, but an isolated shower could still be just offshore,” it was cautioned. With a potential violation of the Cumulus Cloud Rule considered the limiting factor on Friday, conditions on Friday, 31 July, are predicted to be 90-percent-favorable. This is expected to drop back to 80 percent for an attempt on Saturday, 1 August. “For Saturday morning, upper-level winds increase from the east, bringing a slight chance for anvil clouds from any convection over the Gulfstream to move near the Cape,” the 45th concluded. “Therefore, the primary concerns for the 48-hour backup day are the Attached and Detached Anvil Cloud Rules.”