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Six Minutes of Terror - Landing Humans on Mars
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.'"
The current landing setup (the one used on the rovers) involves inflating airbags around the lander, then bouncing the lander into the surface at high speeds, then eventually coming to a stop after a few bounces. This is fine when your lander is filled with robotics, but would obviously be bad when the lander is filled with people.
The landing setup they're proposing is actually more like an air-braking system. It inflates around the lander while it's still at a high enough altitude, giving the lander a considerably larger volume. This would hopefully slow the lander as it continues its descent.
"In case of emergency, break glass. Scream. Bleed to death."
Even if the atmosphere isn't as thick, it's still an atmosphere. Mach 4 is 1361.1 m/s. The escape velocity of Mars is 5.027 km/s. If you enter at Mach 4, you have nowhere to go but down. Deploy a large enough glider, and you will glide. Since the atmosphere isn't a vacuum, there will be drag. Fly around long enough, and you will slow down enough to glide safely in. I'd rather spend a few hours circling the runway than six seconds ramming into it.
UTF-8: There and Back Again