Slashdot Mirror
NASA Will Land InSight on Mars With Cunning -- and Lots of Cork (wired.com)
On Monday, November 26th, NASA will attempt to land the InSight spacecraft on Elysium Planitia, a vast plain just north of the Martian equator. If NASA is successful, InSight (short for Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport) will be the first mission to investigate Mars' deep interior with thermal probes and seismometry, an approach scientists think will address questions about the red planet's formation and composition. But first, the spacecraft must land. From a report: Getting to Mars is hard, but NASA engineers consider entry, descent, and landing -- the seven-minute period in which mission planners are helpless to intervene, due to the tremendous distance between Mars and Earth -- the riskiest sequence in the entire mission. Here's how NASA plans to pull it off.
For InSight, the action will begin Monday, November 26th at around 11:47 am PT (2:47 pm ET). That's when the lander is slated to hit the top of Mars' atmosphere, at an altitude roughly 43 miles above the planet's surface. On contact, the spacecraft will be blazing along at a not-so-cool 5500 meters per second. That's 12,300 miles per hour. At those speeds, the primary concern for NASA's engineers is friction. Mars' atmosphere, which is roughly 100 times thinner than Earth's, plays a vitally important role in InSight's arrival: Bleeding the spacecraft of its kinetic energy. Yet the atmosphere poses a significant threat, as well. The resistance it exerts on InSight's heat shield, a 419-pound enclosure composed primarily of crushed cork, will drive the temperature of the protective barrier to temperatures greater than 2,700 degrees Fahrenheit -- hot enough to melt steel.
For InSight, the action will begin Monday, November 26th at around 11:47 am PT (2:47 pm ET). That's when the lander is slated to hit the top of Mars' atmosphere, at an altitude roughly 43 miles above the planet's surface. On contact, the spacecraft will be blazing along at a not-so-cool 5500 meters per second. That's 12,300 miles per hour. At those speeds, the primary concern for NASA's engineers is friction. Mars' atmosphere, which is roughly 100 times thinner than Earth's, plays a vitally important role in InSight's arrival: Bleeding the spacecraft of its kinetic energy. Yet the atmosphere poses a significant threat, as well. The resistance it exerts on InSight's heat shield, a 419-pound enclosure composed primarily of crushed cork, will drive the temperature of the protective barrier to temperatures greater than 2,700 degrees Fahrenheit -- hot enough to melt steel.
Thus far, NASA is the only organization to have much luck with Mars EDL.
There were a series of Soviet probes in the 1960's and 70's, but the only one to live on the surface was Mars 3, and then only for 20 seconds before it stopped. They also had two probes in the late 1980's, Phobos 1 and 2, but both quit before successfully landing on Phobos. Also their Phobos-Grunt mission in 2011 failed. They did have some luck with flyby missions however.
Likewise Europe's Beagle 2 lander was never heard from again after it touched down on Mars. However the orbiter portion of the mission worked. Europe's 2016 Schiaparelli lander attempt also failed before touchdown and was never heard from again.
NASA had the first full lander success (beyond a few seconds of operation) with Viking 1 and 2 in 1975. Since then they've had a few failures such as the Mars Climate Observer and Mars Polar Lander, but many successes too, even including rovers. NASA seems to be the only space exploration organization adept at landing probes on Mars and making them work. That's no guarantee however, and there are many, many things that can go wrong, some of them unpredictable.
Mars EDL is hard.
Lockheed Martin has produced an animation of the entry descent and landing. Go ahead and watch it, once, then forget about it. It unfortunately is not nearly as informative as, say, the 7 Minutes of Terror video from Curiosity, or the whimsical bounce landing from Spirit and Opportunity.
Reentry heating is primarily caused by rapid compression of the air caused by the speeding vehicle. A bottle of aerosol gets cold when its contents are released and decompressed. Well, the reverse process of compression causes heat to be emitted. And that's what causes most of the heating during reentry, not friction.
https://en.wikipedia.org/wiki/Atmospheric_entry
It appears they're not using a sky crane for this landing.
https://www.youtube.com/watch?v=C0lwFLPiZEE