NASA’s Curiosity rover’s safe arrival in Gale Crater,Mars,thanks to some innovative technology, is still being applauded throughout the world.It is easy to forget that the one-tonne robot is not the first Mars rover.The most incredible new-era technology had already been deployed on Mars by NASA, is executing crucial missions at present, and is paving the way for future Martian missions.
Question:What do you need to protect an expensive state-of-the-art robotic vehicle that is far from human reach and about to crash at high speed on a rocky alien surface?Answer:Retrograde rockets, parachutes, airbags, and an aeroshell.These are found in the makeup of a lander module that was used to bring rovers Spirit and Opportunity described by the mission’s director as “robotic field geologists” safely to the Martian surface in 2004.
After abandoning the Mars-bound spacecraft or ‘cruise stage’ 15 minutes before entering the outer Martian atmosphere, these landers then hurtled towards the Red planet’s surface with increasing speed in response to its gravitational pull.The lander’s exterior layer or ‘aeroshell’ protected the lander and its contents from searing atmospheric frictional temperatures of approximately 1400 degrees C for four minutes.Not long after this a lander parachute was deployed, the bottom half of the aeroshell was jettisoned and the lander was lowered on a tether.Retro rockets were then fired against the projectile’s direction to further decrease the descent velocity.With the worst of the impact speed diminished, the tether was cut fifteen metres above the Martian surface and rovers Spirit and Opportunity relied upon the final cushioning effect that the landers’ cocoon of airbags could produce after filling with gas.
After the initial 30metre high rebound bounce the rover cargo bay rolled and bounced approximately 0.6km until all kinetic energy was expended, and the lander came to a halt within two minutes of the parachutes being deployed.Reminiscent of the 4-petal-structured Mars 2 and 3 landers perhaps cleverest of all was the lander’s folded-up shape.In a final awesome display of robotic dominance over a challenging alien terrain, the protective petals of its 3-sided pyramid form opened out, pushing it into an upright position.This deployment procedure was executed in the Gusev crater for Spirit and on the Meridiani Planum for Opportunity on 4 and 25January 2004 respectively.
The rovers then departed the now platform-like lander structures bearing their missions’ exploratory batons.The MER (Mars Exploration Rover) landers’ structural dimensions and protective technologies had to house rovers that each weighed almost 180kg, (approximately seventeen times the weight of the1997 Mars Pathfinder Mission’s Sojourner rover), and were as big as a golf buggy. In part thanks to the complete success of the lander module technology applied during the 2004 Martian mission rovers Spirit and Opportunity subsequently succeeded in their exploratory objectives and exceeded their 90 day warranties on our neighbouring planet. Incredibly, Opportunity is still active on Mars to this day.
When successful, MER landers do more than conquer the enormous challenge of bringing automated Martian roving vehicles, still intact to a standstill on the surface of Mars after travelling a minimum of 56 000 000 km. They fulfill other useful mission operations from their stationary position on the Red Planet.For example, during its lifetime fourteen years ago, the Mars Pathfinder lander sent a grand total of 2.3 billion pieces of information back to Earth.This included wind and other weather data, more than 15 chemical analyses of Martian ground material, and over 17 000 images.
Since 1997 the Mars landers have remained the same in terms of essential landing technology, albeit altering slightly in appearance and design. Although aeroshells, retro rockets, and parachutes were all key components in the Phoenix and Viking landers as well, these Mars-bound variants dropped lander legs shortly before touchdown on the Red Planet was achieved. The Lander craft of the rover Curiosity, whose successful arrival on Mars was celebrated on 5 August employed the same effective landing techniques as seen in the Spirit and Opportunity mission, but with a few significant alterations. As Curiosity itself weighs almost one tonne, ‘airbag bouncing’ is ruled out.
Instead, reverse rockets helped lower a lander platform with the rover cradled underneath it close to the Red Planet’s surface.The heaviest and largest rover ever to be built for Mars closed the remaining gap to the Martian ground alone, carefully lowered from beneath the hover-rocket lander by a ‘sky-crane’ tether.Curiosity’slanding procedure brought the world’s most sophisticated automated geologist safely in contact with our neighbouring planet.
(Article by Nick Parke, Education Support Officer)