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OriginalArlen writes "Universe Today has a fascinating article discussing the difficulty of executing EDL (entry, descent, landing) on Mars for vehicles bigger than MER, Viking and Pathfinder, and the challenges for manned craft in particular. Airbags can't be used for obvious reasons, but the atmosphere is too thin to be used for parachutes or aerobraking by large heavy vehicles. The stronger gravity (compared to the moon) makes an Apollo-style powered descent impossible. The best current idea is a huge inflatable torus called a hypercone: 'Imagine a huge donut with a skin across its surface that girdles the vehicle and inflates very quickly with gas rockets (like air bags) to create a conical shape. This would inflate about 10 kilometers above the ground while the vehicle is traveling at Mach 4 or 5, after peak heating. The Hypercone would act as an aerodynamic anchor to slow the vehicle to Mach 1.'"Read more of this story at Slashdot.