Mars atmospheric entry

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Mars atmospheric entry is the entry into the atmosphere of Mars. High velocity entry into Martian air creates a CO2-N2 plasma, as opposed to O2-N2 for Earth air.[1] Mars entry is effected by the radiative effects of hot CO2 gas and Martian dust suspended in the air.[2] Flight regimes for entry, descent, and landing systems include aerocapture, hypersonic, supersonic, and subsonic.[3]

For example Mars Pathfinder entered in 1997.[4] About 30 minutes prior to entry, the cruise stage and entry capsule separated.[4] When the capsule hit the atmosphere it de-accelerated from about 7.3 km/s to 0.4 km/s (16330 mph to 900 mph) over three minutes.[4] As it descended the parachute opened to slow it down further, and soon after the heat shield was released.[4] During entry a signal was relayed back to Earth, including semaphore signals for important events.[4]

Comparison of altitude (y-axis) and velocity (x-axis) of various Mars landers
Parachute of Phoenix lander open as it descends in the Martian atmosphere. This picture was taken by the Mars Reconnaissance Orbiter with HiRISE
MSL heat shield

Examples[edit]

MER-B's discarded heat shield on the surface of Mars.

Technologies[edit]

A deployable decelerator like a parachute can slow down a spacecraft after a heat shield.[5] Typically a Disk-Gap-Band parachute has been used, but another possibility are trailing or attached inflatable entry devices.[5] Inflatable types include sphere w/ fence, teardrop w/ fence, isotensoid, torus, or tension cone and attached types include isotensoid, tension cone, and stacked toroid blunted cone.[5] Viking Program era researchers were the true pioneers of this technology, and development had to be restarted after decades of neglect.[5] Those latest studies have show that tension cone, isotensoid, and stacked torus may be the best types to pursue.[5]

Finland's MetNet probe may use an expandable entry shield if it is sent.[6] Martian air can also be used for aerobraking to orbital velocity (aerocapture), rather than descent and landing.[1] Supersonic retro-propulsion is another concept to shed velocity.[7]

Example[edit]

The following data were compiled by Mars Science Laboratory's Entry, Descent and Landing team at NASA's Jet Propulsion Laboratory. It provides a timeline of critical mission events that occurred on the evening of August 5 PDT (early on August 6 EDT).[8]

Event Time of Event Occurrence at Mars (PDT) Time Event Occurrence Received on Earth (PDT)
Atmospheric entry 10:10:45.7 PM 10:24:33.8 PM
Parachute deployment 10:15:04.9 PM 10:28:53.0 PM
Heat shield separation 10:15:24.6 PM 10:29:12.7 PM
Rover lowered by the sky crane 10:17:38.6 PM 10:31:26.7 PM
Touchdown 10:17:57.3 PM 10:31:45.4 PM

675608main edl20120809-full.jpg

Curiosity's EDL team releases a timeline for mission milestones (depicted in this artist's concept) surrounding the landing of the Mars rover.

See also[edit]

References[edit]

Further reading[edit]