What factors make landing on Mars easier than on the Earth? Harder?

nukeman

Iv been watching the NASA guys work on the mars lander on Ustream, and starting to really get into it. But I have a question:

What factors make landing on Mars easier than on the Earth? Harder?

And im having a debate with a friend, maybe one of you can help. Which variables are important for a successful landing, eg. mass, size, shape.?

tkjtkj

easier:
no competing air traffic and its associated flight control rules

harder:
no flight control rules, and no other traffic that can contribute to weather reports , etc.
also: thin atmosphere makes things happen faster ...

but colder atmosphere makes for easier maneuverability of a landing craft ... easier than were that atmosphere at a temp usually found on earth. Low temperatures increase density, and airfoils and associated control surfaces depend on density to be effective: more dense = more responsive control of the vehicle. Its usually easier to fly in the winter time here ...

nukeman

As for the lander it self, Which variables are important for a successful landing, eg. mass, size, shape.?

Driftwood1

Risks and probability of catastrophic landing depends on many things.

Think of how you would build a MArs LAnder that would ensure its total destruction as it slammed into the Martian surface

Trick is to avoid these things

squeakywaffle

The air is thick enough that using a rocket to decelerate (like the NASA moon lander) is impractical because a rocket plume is unstable at the airspeeds involved.

However, the air is also too thin to rely on aerodynamic drag effects to slow down a heavy spacecraft (as in the space shuttle, Apollo CM, etc).

What's a method that works in the middle? We don't know, and we have no experience in that regime. We've gotten away with it so far because our mars landers have been very light.

edit for more:

The new rover (Curiosity) is too large to use airbags like the previous rovers have, so it's been designed to use a fairly interesting arrangement of aerodynamic drag from an aeroshell and later parachutes, and rockets at the final stage. Look it up for more info.

Also, I recommend you download Orbiter:

http://orbit.medphys.ucl.ac.uk/home.php

and try landing on mars yourself...

Radrook

Wouldn't gradual decceleration before achieving Mars orbit decrease risk?


Excerpt:
Entry, Descent and Landing on Mars

With an historic failure rate of 66 per cent, the entry, descent and landing phase of the Mars mission is the most dangerous six minutes of the nearly two-year journey. Because the Mars surface pressure is less than one per cent of Earth’s—not enough to slow a spacecraft down—the engineering challenge is to find a way to slow the Mars lander from its entry velocity that might be in excel of of 19,000 kilometres an hour to zero impact in just six minutes. Steadily improving deceleration and landing techniques for every mission, engineers have been developing new technologies to help reduce the risks.
http://www.racetomars.ca/mars/article_descent.jsp

LURCH

I must be oversimplifying this in my head, because it seems to me that a shallower approach angle would suffice.

Radrook

Maybe that would increase atmospheric friction heating time beyond present shield endurance.