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Since the advent of space rocket technology, the exploration of Mars has figured prominently in the space programs of the United States, Russia (formerly the Union of Soviet Socialist Republics \u2013 USSR), and Europe.<\/p>\n
And in 1960, on October 10, the Earth\u2019s first space probe to Mars was launched by the USSR. Named the Mars 1M No.1, the mission ended shortly after liftoff due to a launch failure.<\/p>\n
And thus the reality of up-close exploration of Mars was realized.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/08\/Z33.jpg\" "\\"Z3\\"")
Since 10 October 1960, 43 dedicated missions (some with more than one mission element) to Mars \u2013 be they fly-bys, orbiters, landers, rovers, or sample return missions \u2013 have been launched by NASA, Russia\/USSR, Japan, ESA (European Space Agency) UK, and China (hitching a ride with a Russian probe).<\/p>\nSpaceX launch tickets
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Of those 43 attempts, 42 of the missions\u2019 fates are known: 15 successes, 4 partial successes, and 23 failures.<\/p>\n
One mission\u2019s fate, the Curiosity mission, will be known in large part Monday morning \u2013 with final analysis in one Martian year (two Earth years).<\/p>\n
Despite a straight-up, world-wide Mars mission success rate of only 34.8 percent, a percentage which increases to 44 percent if partial successes are included, there is great optimism that Curiosity will make it safely to the Martian surface.<\/p>\n
First, portions of its landing systems are derived in part from previous NASA missions to Mars and from the Apollo Program. Second, NASA itself has an impressive achievement rate of 13 successes out of 19 attempts when it comes to Mars endeavors.<\/p>\n
Overall, NASA\u2019s Martian success rate is an impressive 68 percent, with accomplishments including Earth\u2019s first successful mission to Mars with Mariner 4, the first successful Martian orbiter with Mariner 9, and first completely successful Martian landing with Viking 1, the first successful Martian rover with the Mars Pathfinder mission, and the longest surviving Human technology on another world with the Mars Exploration Rover Opportunity (which has been actively roving across the surface of Mars since 25 January 2004).<\/p>\n
Moreover, humankind has attempted to land, to date, five rovers on Mars \u2013 two from Russia, and three from the United States.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/08\/Z43.jpg\" "\\"Z4\\"")
Of those five rovers, only three have successfully made it to the Martian surface in a manner that allowed them to perform their missions: Mars Pathfinder\u2019s Sojourner, the Mars Exploration Rover Spirit, and the Mars Exploration Rover Opportunity.<\/p>\nAll of the successful rovers have been from NASA.<\/p>\n
The two Russian\/USSR rovers (Mars 2 and Mars 3) in May 1971 encountered a crash landing on Mars and a lander failure \u2013 the lander failed 15 seconds after reaching the surface of Mars \u2013 respectively.<\/p>\n
The United Kingdom\u2019s Beagle 2 mission \u2013 which arrived at Mars on 25 December 2003 with ESA\u2019s Mars Express orbiter \u2013 was not a rover, but encountered a landing failure on 6 February 2004. Its ultimate fate, aside from the fact that something went wrong, is unknown.<\/p>\n
Thus, the Mars Science Laboratory\u2019s rover Curiosity will be the sixth rover to attempt to land on Mars \u2013 and NASA\u2019s fourth overall rover sent to the Red Planet.<\/p>\n
Curiosity\u2019s arrival at Mars \u2013 Entry, Descent, and Landing \u2013 Preview:<\/p>\n
Curiosity\u2019s arrival at Mars will be one for the record books, not only in terms of the information the rover will be capable of sending back, but also for the simple fact that the rover\u2019s landing at Gale Crater will be one of pin-point accuracy.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/08\/Z52.jpg\" "\\"Z5\\"")
For landing, Curiosity will target a landing ellipse area at Gale Crater that is 20km by 7km (roughly 12miles by 4.3miles). This is in striking contrast to the much larger 150 by 20km (93 by 12mile) landing ellipses used for the Mars Exploration Rovers Spirit and Opportunity back in 2004.<\/p>\nTo accomplish such a feat, Mars Science Laboratory engineers designed a new high-precision Entry, Descent, and Landing (EDL) system \u2013 one that requires six different spacecraft configurations, 76 pyrotechnic devices, the largest supersonic parachute ever designed and manufactured, and more than 500,000 lines of code to execute the required maneuvers to safely ease Curiosity to the surface.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/08\/Z71.jpg\" "\\"Z7\\"")
Since Mars\u2019s atmosphere is much thinner than Earth\u2019s, it presents several unique challenges for landing a spacecraft on the surface of the planet. Mars\u2019s atmosphere is too thin for parachutes and aerobraking alone to slow landing spacecraft to a safe speed.<\/p>\nNonetheless, Mars\u2019s atmosphere is still thick enough to induce instability to a landing spacecraft when deceleration rockets are used (like they will be for Curiosity) to slow a spacecraft\u2019s approach to Mars\u2019s surface.<\/p>\n
Thus, Curiosity\u2019s EDL sequence will be challenging. For simplicity\u2019s sake, Curiosity\u2019s EDL sequence can be broken down into four phases: Guided Entry, Parachute Descent, Powered Descent, and Sky Crane landing.<\/p>\n
1. GUIDED ENTRY:<\/p>\n
Tucked safely inside its aeroshell, Curiosity will begin its descent to the Martian surface folded up inside the protective casing it has been in during its entire cruise to the Red Planet.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/08\/Z81.jpg\" "\\"Z8\\"")
To accomplish a stable entry into Mars\u2019s atmosphere, the aeroshell (with Curiosity inside) will separate from the main cruise stage that has been with the rover\/aeroshell duo since their launch on an Atlas V rocket on 26 November 2011 10 minutes before atmospheric entry over Mars.<\/p>\nThe cruise stage was used during the interplanetary cruise to provide power, communications with Earth, and propulsion for course correction burns.<\/p>\n
One minute after cruise stage\/aeroshell separation (9mins before atmospheric entry), thrusters on the aeroshell will fire to nullify the aeroshell\u2019s 2-rpm (rotations per minute) rotation that helped stabilize the vehicle during its interplanetary cruise stage.<\/p>\n
This thruster firing will also properly orient the aeroshell to place its heat shield into the direction of travel.<\/p>\n
Just minutes prior to atmospheric entry, two 165 lb tungsten ballast weights will jettison from the aeroshell, offsetting the aeroshell\u2019s center of mass from the axial centerline and allowing the aeroshell to have lift as it enters the Martian atmosphere.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/08\/Z91.jpg\" "\\"Z9\\"")
With the aeroshell properly positioned, its heat shield will take the brunt of the atmospheric entry forces.<\/p>\nMade from a phenolic impregnated carbon ablator, the 4.5m (15 ft) diameter heat shield is the largest single-piece heat shield ever flown in space.<\/p>\n
For the first four minutes of atmospheric entry, the heat shield will reduce the aeroshell\u2019s velocity through an ablation process.<\/p>\n
Ablative heat shields work on the principle of lifting the hot shock layer gas (created by friction from a hypersonic spacecraft\u2019s interaction with the relatively stationary atmosphere) away from the heat shield\u2019s outer wall. <\/p>\n
In turn, this creates a cooler boundary layer that provides solid protection against high heat flux through a process called blowing.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/08\/Z12.jpg\" "\\"Z12\\"")
The ablation process consequently causes the TPS (Thermal Protection System) layer to char, melt, and sublime through the process of pyrolysis: the thermochemical decomposition of organic material at elevated temperatures without the participation of oxygen.<\/p>\nThe gas produced by pyrolysis is what drives blowing and causes blockage of convective and catalytic heat flux \u2013 thus protecting the spacecraft\u2019s payload from atmospheric entry heating.<\/p>\n
For Curiosity, the aeroshell\u2019s ablative heat shield will provide protection for the rover from the moment of Martian atmospheric entry at a velocity of 5.8 km\/s (3.6 miles\/s) through an approximate speed of 470 m\/s (1,500 ft\/s).<\/p>\n
The aeroshell\u2019s heat shield will experience peak heating of 3,800 degrees F approximately 1minute 15seconds after entering Mars\u2019s atmosphere.<\/p>\n
A maximum deceleration force of 15 times the force of Earth sea-level gravity is expected approximately 10 seconds after peak heating.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/08\/Z11.jpg\" "\\"Z11\\"")
It is during this time of Martian atmospheric entry that Curiosity will debut a new method of reducing the landing zone envelope.<\/p>\nDerived from an algorithm from the Apollo Command Modules of the Apollo Program, the reduction in landing precision error for Curiosity is made possible by the use of real-time data of the lifting forces experienced by the aeroshell.<\/p>\n
This real-time data will allow the aeroshell\u2019s guidance system to detect dispersions and discrepancies in the entry profile and correct, or \u201cfly out,\u201d those errors to keep Curiosity pointed toward its pin-point landing zone at Gale Crater.<\/p>\n
The ability to \u201cfly out\u201d these discrepancies relates to the just-prior-to-atmospheric-entry jettison of the two 165 lb tungsten weights and the resultant off-center trim angle of the aeroshell during atmospheric flight.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/08\/Z10.jpg\" "\\"Z10\\"")
The total lift vector of the craft \u2013 its ability to correct flight path dispersions \u2013 will be controlled by four sets of two Reaction Control System (RCS) thrusters.<\/p>\nEach pair of RCS thrusters will be capable of generating 110 lbf of thrust. Pulsing\/Firing of the thrusters will allow the aeroshell to change the direction of its lift and thus steer toward its landing zone.<\/p>\n
Toward the very end of the entry sequence plunge through the atmosphere, six 55 lb tungsten weights will be jettisoned from the aeroshell to eliminate the center of mass offset in preparation for supersonic parachute deployment.<\/p>\n
The entire atmospheric entry portion of the EDL sequence will span approximately 4 minutes, after which phase 2 of the EDL process will begin.<\/p>\n
2. PARACHUTE DESCENT:<\/p>\n
Once the aeroshell capsule has slowed to 470 m\/s, or 1500 ft\/s (roughly Mach 2), Curiosity will be approximately 10 km (6.2 miles) above the surface of Mars.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/08\/Z13.jpg\" "\\"Z13\\"")
At this point, the aeroshell\u2019s supersonic parachute will deploy.<\/p>\nThe use of a supersonic parachute during Martian landings is not new. The Viking landers, Mars Pathfinder\u2019s Sojourner rover, and the Mars Exploration Rovers Spirit and Opportunity all used supersonic parachutes during their respective EDL sequences.<\/p>\n
The supersonic parachute that will be used by Curiosity\u2019s aeroshell contains 80 suspension lines and is 160ft long and 52ft in diameter.<\/p>\n
It will generate approximately 65,000 lbf of drag on the aeroshell as it descends through the lower portion of the Martian atmosphere.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/08\/Z141.jpg\" "\\"Z14\\"")
Following parachute deployment, the ablative heat shield will separate and crash onto the Martian surface.<\/p>\nWith the heat shield gone, a camera on the underside of the Curiosity rover will begin acquiring images of the Martian surface at an altitude of 3.7km (2.3 miles) and at a rate of 5 frames per second. The camera\u2019s resolution is 1600\u00d71200 pixels.<\/p>\n
This acquisition will continue until Curiosity is safely on the ground.<\/p>\n
After 5.1 miles altitude of parachute descent, Curiosity will be just 1.8km (1.1 miles) off the ground of Mars. <\/p>\n
At this point, the rover will be descending at a velocity of 100 m\/s (220 mph). It is at this point that the third phase of the EDL sequence will begin.<\/p>\n
3. POWERED DESCENT:<\/p>\n
At an altitude of 1.1 miles and a velocity of 220 mph, the Curiosity rover and its descent stage will literally drop out of the bottom of the aeroshell.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/08\/Z151.jpg\" "\\"Z15\\"")
The descent stage, a platform located above the rover (when viewed from the side with the rover\u2019s wheels oriented toward the ground), will provide the final breaking thrust to gently lower Curiosity to the ground of Gale Crater.<\/p>\nThis will be accomplished via the use of eight of Aerojet\u2019s variable thrust mono propellant hydrazine rocket thrusters located on the descent stage.<\/p>\n
These rocket thrusters, called Mars Lander Engines (MLEs), will produce 700 lbf of thrust each. They were derived from the thrusters used on the Viking landers in the 1970s, again developed by Aerojet, with the Californian company having a long history with NASA\u2019s Mars missions.<\/p>\n
The MLEs\u2019 firing sequence will initially veer Curiosity away from the still-descending parachute\/aeroshell duo before reorienting Curiosity and quickly slowing its downward, vertical velocity to 4 m\/s and nullifying all horizontal movement relative to the ground.<\/p>\n
Attitude rates will also be leveled out to properly level Curiosity for landing.<\/p>\n
Once the slowing and leveling process is complete, the fourth and final stage of the EDL sequence begins.<\/p>\n
4. SKY CRANE:<\/p>\n
Once leveling with the ground and achieving a continually decreasing descent rate, Curiosity itself will undergo an operation that no other space vehicle has: A sky crane will lower it from the descent stage to the Martian surface.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/08\/Z161.jpg\" "\\"Z16\\"")
At a way-point altitude of 27.3 meters (81.9 ft) from the surface, commands will be sent to pyrotechnic devices to release the rover and begin the lowering process.<\/p>\nThree bridles will control Curiosity\u2019s lowering from the descent stage while an umbilical line will ensure complete communication between the rover and the descent stage.<\/p>\n
Once the sky crane lowering process begins, Curiosity will begin transforming from its stowed, interplanetary cruise configuration into its landing configuration<\/p>\n
As the bridles come to full extension (25ft below the descent stage), all loads relating to Curiosity will be transferred to the bridles as the descent stage slows itself and Curiosity to a relative velocity to the ground of just 0.75 m\/s.<\/p>\n
At an altitude of 15m (45ft), Curiosity\u2019s Touchdown Logic software will be initiated and the touchdown velocity of just 0.75 m\/s will be reached.<\/p>\n
This will begin the constant velocity descent sequence.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2012\/08\/Z17.jpg\" "\\"Z17\\"")
And then, Curiosity will make contact with the ground.<\/p>\nThe Touchdown Logic will wait two (2) seconds to confirm full weight on wheels for Curiosity while instructing the descent stage to throttle the MLEs to maintain a 0.75 m\/s descent rate (even though Curiosity will already be on the ground. This will be done to ensure that all proper backups and safeties are in place and that erroneous touchdown indicators do not result in a loss of the mission).<\/p>\n
Once touchdown is confirmed across multiple platforms, control of the landing sequence will be handed from Curiosity to the descent stage, the umbilical lines \u201cdead-faced and cut,\u201d and the bridles pyrotechnically detached from Curiosity.<\/p>\n
The descent stage will then assume command of itself, quickly ascend to an altitude of 15m (45ft), pitch over 45-degrees, perform a \u201cfly away\u201d maneuver to clear Curiosity\u2019s vicinity, and then crash land at least 500ft away.<\/p>\n
Curiosity is expected to land at Gale Crater at 05:31 UTC (01:31 EDT) \u2013 15:19 LMST (Local Mean Solar Time) at Gale Crater.<\/p>\n
EDIT: Amazingly, all the events proved to be successful. Refer to the live threads.<\/p>\n
(Images: L2 Content, NASA, JPL)<\/p>\n
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History was made at 1:31am EDT (05:31 UTC) Monday on the fourth planet in this solar system as NASA\u2019s Mars Science Laboratory rover Curiosity descended to a picture-perfect rocket-guided and -slowed descent to a gentle, wheels-first, sky crane touchdown on the surface of the Red Planet. NASA is 14 for 20 in their attempted missions […]<\/p>\n","protected":false},"author":1,"featured_media":30328,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[2927,367,4217],"class_list":["post-40053","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","tag-curiosity","tag-mars","tag-msl"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/40053"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=40053"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/40053\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media\/30328"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=40053"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=40053"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=40053"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}