Screenshot from ULA/NASA Webcast of the launch of Mars 2020. Boiling of LOX vapors just now
Mission Rundown: ULA - Atlas V 541 - Mars 2020
Written: September 7, 2021 - Edit: November 28, 2022
All that just to fly by Mars
Liftoff of the third mission to Mars during the current interplanetary transfer window at the start of a Earthly two hour launch window that opens at 07:50 EDT.
ULA’s Atlas V 541 launched from SLC-41, CCAFS at 07:50 EDT with the Perseverance rover in its 5 meter fairing. Climbing to an initial orbit of 270 km (167 miles), the Centaur upper stage then boosted the rover towards Mars.
The accuracy of the launch was to ULA standards only using 3.3% of the requirement for a successful launch towards Mars, that’s a bullseye. Actually the 2nd stage Centaur is deliberately missing Mars, the cruise stage spacecraft will correct its course toward Mars after the Centaur 2nd stage has secured itself for a life as a piece of deep space debris going in a Heliocentric orbit between Earth and Mars.
For the Mars 2020 mission, the configuration of the Atlas V is a 541 configuration. The last three numbers or letters in the Atlas V’s name denote the configuration of the rocket. The first number/letter shows the fairing diameter size (in meters, of course). The number 5 in this case stands for a 5 meter fairing. Following, the second number determines the number of strap-on solid rocket boosters (SRBs) which can range from 0 to 5, and in this case, there are 4 strapped on to the side of the center common core. Finally, the number refers to the number of engine bells on the Centaur Upper Stage.
The Atlas V 541 rocket is being loaded with 25000 gallon RP-1 and 48800 gallon LOX in the first stage. The Centaur stage is being loaded with 4500 gallon LOX and 12300 gallon LH2. About 500 gallon is reserved for Helium backfill and RCS thruster propellants.
The Atlas V 541 rocket AV-088 stands 60 meters - 197 feet tall and weighs in at 530770 kg - 1170150 pounds at liftoff.
The Mars 2020 Payload
The only part of the spacecraft left after launch was Perseverance which is enclosed in its aeroshell. This shell acts as protection, but also hosts the power and course correction propulsion systems. Throughout this time, mandatory health and communications checks were performed by NASA’s specially trained team of engineers and mission specialists. Towards the end preparations began for the Entry, Descent and Landing (EDL).
Also known as the “7 minutes of terror”, this phase of Perseverance’s flight is dubbed as the most terrifying by engineers and space fans. Due to the fact that Mars is so far away from Earth and communications are limited to the speed of light, the transmission signals can take about 12 minutes to reach Earth. That’s a 24 minute round-trip. All the data that the teams saw happened 12 minutes prior. By the time engineers received the signal that Perseverance had entered the atmosphere, it was already on the ground.
After six months of cold space travel, the Perseverance rover, as part of the Mars 2020 mission, has safely touched down on Mars at 20:43 UTC with the signal being received at 20:55 UTC. The sequence from cruise stage separation to the sky crane deployment and lowering of the rover, everything was nominal and Mars now has another human-made marvel on its surface.
Graphic of Perseverance descent in the Aeroshell and landing on Mars. Credit: NASA/JPL
List of events happening during EDL
Cruise stage separated to be burned up in the Martian atmosphere
Entry of the landing craft into the Martian atmosphere began
At roughly 2,100 degrees Celsius, the heat shield experienced maximum heating
The landing craft experienced the maximum deceleration. Slowing from 21 200 km/h (13 200 mph) to just 1 600 km/h (1 000 mph) in only two and a half minutes
The parachute deployed from the back shell at an altitude of 9 to 13 km (6 to 8 miles)
Heat shield separation from the back shell and the ground radar systems on the Skycrane activated to define a suitable landing area
Back shell separation from the Skycrane as the rover began a moment of freefall before the landing motors on the Skycrane ignited
At around 21 meters (70 feet), the rover separated from the Skycrane landing stage tethered to it by three nylon ropes and was gently set down at 2.7 km/h (1.7 mph). The Skycrane then flew away and crashed into the surface at a safe distance.
Perseverance takes a number of pictures, selfies and establish contact with Earth
NASA sought to capitalize on the success of Curiosity and the overall science platform of that rover’s design with the Mars 2020 vehicle, incorporating lessons learned and expanding the new rover’s overall capabilities to include detection of the biosignatures of past microbial life as well as collection and bottling of Martian samples.
Screenshot of the size difference between rovers on Mars. Perseverance is slightly bigger than Curiosity. The rovers Spirit and Opportunity were dropped encapsulated with lots of airbags
These changes with the finalized suite of scientific instruments, brought Perseverance’s overall mass to 1,025 kg, heavier than Curiosity (at 899 kg). Unpacked from its aeroshell of heat shield, back shield, skycrane and parachutes, that’s all that's left.
Given the overall demand of the mission and its baseline from that of Curiosity’s, Perseverance carries a Multi-Mission Radioisotope Thermoelectric Generator, or MMRTG, that is in fact a backup to the one used for Curiosity.
The MMRTG — via the natural decay of plutonium-238 — will provide a consistent 110 watts of power as well as heat throughout the mission and offers a potential operational lifetime of 14 years for the rover. MMRTG is the last loading item on the VIF building, it weighs 44.9 kilos - 99 pounds and is placed on Perseverance through access doors in both the fairing and the back shell of the aeroshell.
The Ground Support Equipment - GSE - needed to install the Radioisotope Thermoelectric Generator - RTG - is bulky at best. It takes two technicians with supervising support personnel to shift the RTG through the fairing access door, place it on a hydraulic slide, open the access panel in the back shell, press it in place, hook up all electric and fluid connectors and bolt the RTG fast to Perseverance.
All this happens while the rocket is vertical in the VIF building 400 meters from the launch pad SLC-41, and the spacecraft with Perseverance is placed upside down in the fairing. Another problem is the production of heat and electricity by the RTG. That must be dealt with and be removed by cooling the spacecraft with chilled nitrogen gas and using the electricity to charge batteries or power the rocket during launch.
Use of a nuclear power source allows science operations to occur at any time and during most seasonal conditions on Mars, including during the planet’s notorious dust storms — the last major one of which claimed the operational life of the Opportunity rover and the InSight mission which both relied on their solar panels for power.
Future solar powered missions to other planets must have a tool to clean solar cells.
Perseverance is also equipped with two rechargeable lithium-ion batteries to aid operations during peak scientific demands, a few of which are predicted to exceed the maximum continuous output of 110 watts from the MMRTG.
Surface Operations after arrival
Landing is timed for approximately 3:45 p.m. local mean solar time at Jezero Crater, Mars, on 18 February 2021.
After landing, the rover’s computers will automatically switch from Entry, Descent, and Landing mode to Surface mode and begin a series of autonomous activities and checkouts for its first day on Mars, officially known as Sol 0.
A “Sol” is a single Martian day, lasting 24 hours 39 minutes 35 seconds, and will be the official time keeping designation used for the mission.
Surface Operations will commence in a few days and weeks after arrival. Some of the initial operations included deployment of the communications antennae and taking images of its surroundings.
The mission is scheduled to last about one Martian year, or 687 Earth days. However, the team will often refer to mission days as “Sols” or Martian days. In this case, the mission will last 669 sols. The first 90 sols will consist of initial checkouts of all of Perseverance’s systems to ensure that they are all functioning properly.
Shortly after touchdown, Perseverance began taking images of the surface and its surroundings so scientists and engineers had a better idea of the landing site.
During this initial period, the team will be on Martian time, which means starting their shifts 40 minutes earlier each day because one Sol is approximately 40 minutes longer than one Earth day.
The Perseverance rover with labeled instruments. (Credit: NASA/JPL)
The payload consists of the Perseverance rover and the attached drone, Ingenuity.
The Perseverance rover is slightly bigger and the most complex and most technologically advanced piece of hardware to travel to another planet. Similar in shape/size to the former, and still operating, Curiosity rover, launched on November 26, 2011.
But it’s not just the instruments mounted to or used by the rover that are a highlight of the mission. Perseverance also carries the Ingenuity Mars helicopter, the first-ever helicopter to be sent to another planet. Source. At just 1.8 kg (4 lb), two pairs of carbon-fiber, counter-rotating blades moving at 2,400 rpm will allow this small, solar-powered helicopter to perform 90 second flights every Martian day.
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