Slashdot Mirror
NASA Phoenix Mission Ready For Mars Landing
Several readers relayed the press release from JPL about the upcoming landing of NASA's Phoenix Mars Lander on May 25. It's going to set down in the north polar regions and look for indications of whether conditions have ever been favorable for microbial life. "Phoenix will enter the top of the Martian atmosphere at almost 21,000 kilometers per hour... In seven minutes, the spacecraft must complete a challenging sequence of events to slow to about 8 kilometers per hour... before its three legs reach the ground. Confirmation of the landing could come as early as 7:53 p.m. EDT. 'This is not a trip to grandma's house. Putting a spacecraft safely on Mars is hard and risky,' said Ed Weiler, associate administrator for NASA's Science Mission Directorate. 'Internationally, fewer than half the attempts have succeeded.'"
Because even at 8km/h you can do serious damage. Any lander has to be extremely light for takeoff from Earth and the transit to Mars, contain extremely fragile equipment, and end up there in one piece. "Bouncing" off Mars is not an option. That requires heavy, expensive materials, or some sort of complicated landed shield arrangement (e.g. giant inflatable bubble) that all add years of work and millions to the cost of the project. You could literally double or treble the cost of the entire project by "beefing up" the lander.
Plus, it has to land under autonomous control, so you really have no idea how fast it actually landed or exactly where until several minutes after it has landed - so coming in a little too fast isn't a good option, neither is a stray patch of rock (there are few "soft spots" on Mars, by the way - it's mostly rock). Much better to land as gently as you can manage and do your braking manoevures in the "air" as you come down. You've got plenty of time, the physics are easier to calculate, and there's less to go wrong.
The first few hours of a new lander's life on another planet are basically checking that everything still works, even with all the gentle landings in the world, things get broken that cost MILLIONS to put them up there. 50% of the things still never make it to the planet operational, even with all the good will in the world behind it. You want to spend MULTIPLES of the cost of the entire project on making the landings more difficult, more violent and less reliable when we can't even get half of what we send onto the planet successfully?