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Founded January 1970
Julian Date: 2459264.18
2020-2021: XCIII
THE DAILY ASTRONOMER
Thursday, February 18, 2021
Exploratorium XXVI: Touchdown Terror
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See the Perseverance Mars Rover landing live this afternoon:
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Location
Mars
Time
This afternoon
Imagine the following scenario. You -yes, you- drive to the store to buy some milk. Not that tricky an issue, is it? Well, imagine that you had to program the car to navigate its way to the store. Assume that you had to ensure that it was able to maneuver safely through the parking lot. The car would then deploy a rover that would enter the store, locate the milk and then tender the proper amount to the cashier prior to departing. The rover would then return to the car which would then drive back to your home and present you with the desired item. During the time period between the car's deployment and return, you would be powerless to intervene, even to make any necessary last minute course corrections. You'd have to sit back, bite what remains of your nails and, even though you're a scientific type, pray that all goes according to plan. This fanciful scenario -which might become a common method of milk acquisition in the near future- gives us an appreciation of what NASA scientists will experience later today when the Mars Perseverance Rover sets down on the Martian surface.
Launched on July 30, 2020, the Mars2020 mission intends to deliver the Mars Perseverance Rover around Jezero crater, an ancient lakebed where water might have freely flowed about 3.5 billion years ago. One of the mission aims is to detect traces of primordial life within the dessicated Martian soil. Before it can begin its work, however, the rover has to land safely: no easy task.
Our only focus today is what will hopefully be a safe landing: the seven terrifying minutes when the craft has to go from a 12,500 mph flight to a gentle touchdown on the planet surface. The inability of engineers to intervene during this descent engenders that terror in them all: if anything goes awry, the vessel could be rendered inoperable and all the efforts and resources invested in its design, construction and deployment will be for naught.
But, bah humbug, it will all work out splendidly.
Here is what shall transpire this afternoon.
3:38 p.m. Eastern Time
The spacecraft will encounter the tenuous Martian atmosphere at speeds exceeding 12,500 miles per hour. The vessel will be employing its thrusters to help maneuver it towards its intended landing spot. Also it will jettison the shell containing its fuel and sensors.
The spacecraft will encounter the tenuous Martian atmosphere at speeds exceeding 12,500 miles per hour. The vessel will be employing its thrusters to help maneuver it towards its intended landing spot. Also it will jettison the shell containing its fuel and sensors.
3:40 p.m.
After the vessel again employs its thrusters to halt its rotation, it will deploy two 70-kg balancing weights to adjust its lift-to-drag ratio. The descent speed will approximately equal 10,500 miles per hour.
After the vessel again employs its thrusters to halt its rotation, it will deploy two 70-kg balancing weights to adjust its lift-to-drag ratio. The descent speed will approximately equal 10,500 miles per hour.
3:47 - 3:48 p.m.
The vessel penetrates the lower part of the atmosphere, which will generate tremendous amounts of heat energy, although less than that which a descending probe would experience in Earth's atmosphere. At this moment, the craft is approximately 400 miles from its target.
The vessel penetrates the lower part of the atmosphere, which will generate tremendous amounts of heat energy, although less than that which a descending probe would experience in Earth's atmosphere. At this moment, the craft is approximately 400 miles from its target.
3:52 p.m.
Speed reduced to approximately 1,068 miles per hour. Just prior to this time, the vessel will have used its thrusters to adjust its alignment. The spacecraft also contains an entry system designed to make final corrections to its alignment. It will also eject six more balance weights around this time.
3:52 - 3:53 p.m.
The parachute deployment phase. As the Martian atmosphere is much more tenuous than Earth's, the parachute will not impede the descent as much as it would here. The speed will still just slightly exceed 160 miles per hour.
The parachute deployment phase. As the Martian atmosphere is much more tenuous than Earth's, the parachute will not impede the descent as much as it would here. The speed will still just slightly exceed 160 miles per hour.
3:53 p.m.
The heat shield, which protected the craft, will now separate from the vessel and will expose the Perseverance probe that will record the remaining descent phase.
Terrain navigation will also commence. The craft has been programmed to seek out viable landing sites so as not to crash land on any boulders or other protruding objects.
3:54 p.m.
The engine will engage that will ignite the retro-thrusters to reduce its speed to 2 miles per hour.
3:54 p.m.
The rover's descent engines engage detach and start their flight over the Martian terrain
3:55 p.m.
The rover drops from the descent stage and is lowered using cables along a sky crane.
3:55 p.m.
The rover deploys its wheels and touches softly down on the terrain while the sky crane crash lands away from the rover's landing site.
Assuming that all goes well, the probe will then begin to study the Martian terrain and perhaps learn more about possible Martian life. First things first, though. Let's just get through this afternoon.
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