Curiosity

Alan Erskine wrote:
AM, Fred J. McCall wrote:

Curiosity is a lot bigger than the previous landers. Without rockets
to slow it down down low, you get a smoking hole because you simply
can't put a big enough parachute on it to slow it down enough.

Then you put the 'skycrane' _under_ the rover; not above it. Cut out
the 'middle-man' of those cables and make the whole thing a lot simpler.
Reduce the complexity and increase the reliability.

When every gram counts you pull tricks to increase the payload. You'll
notice that Curiosity is a lot bigger than any of the provious probes.
The reason is more than newer rockets at leaunch time.

Compare with the lunar orbit rendezvous that Apollo used to get to the
Moon and back. A stunt to save payload weight then paint it green with
enough extra money you're pretty sure it will work correctly the first
time.

On Aug 7, 3:10*pm, Alan Erskine wrote:

* Reduce the complexity and increase the reliability.

No, that increases mass and complexity and decreases the reliability.

The rover would be on top of a lander, which means the cg is higher,
which means the lander legs would have to have a wider span, which
means more complicated mechanism to stow them in the same size heat
shield. That doesn't include all the mechanisms for stowing the ramps
that would also be complicated, since they would have be designed to
allow the rover to roll off either direction and account for rocks
being under or in front of the ramp.

No, the reasons for the skycrane landing method are that is decreases
mass and complexity and increases the reliability.

Sylvia Else wrote:
On 6/08/2012 2:50 PM, Alan Erskine wrote:
Why didn't they just use bigger parachutes? Use the supersonic
'chute to slow the vehicle down and then two or more large 'chutes
for final descent.

The ground-level density of the Martian atmosphere is about 1/50
that of air on Earth. So a parachute (if it could be made no more
massive itself) would have to be 50 times greater in area than an
Earth parachute to achieve the same descent velocity. It's hardly
practical.

Does the difference in gravitational pull between Earth and Mars come
into play as well?

rick jones
--
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these opinions are mine, all mine; HP might not want them anyway...
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In article ,
Rick Jones wrote:

Sylvia Else wrote:
On 6/08/2012 2:50 PM, Alan Erskine wrote:
Why didn't they just use bigger parachutes? Use the supersonic
'chute to slow the vehicle down and then two or more large 'chutes
for final descent.

The ground-level density of the Martian atmosphere is about 1/50
that of air on Earth. So a parachute (if it could be made no more
massive itself) would have to be 50 times greater in area than an
Earth parachute to achieve the same descent velocity. It's hardly
practical.

Does the difference in gravitational pull between Earth and Mars come
into play as well?

rick jones

Of course.