Opportunity has landed

(Henry Spencer) wrote in message ...
In article ,
Christopher M. Jones wrote:
Actually, if you have a big, "fast", RTG powered rover you
can land in the safest spot (with airbags) and simply drive
to where you want.

Unfortunately, "safest" doesn't necessarily translate to "safe". The
airbag system doesn't *guarantee* a safe landing; a sharp rock could be
curtains for an airbag lander. You are better off doing a rocket landing
with a scanning lidar for finding a flat spot and flying to it.

I was under the impression that the airbag system could
cope to a decent degree with failures of one or more of
the bags. So a single sharp rock wouldn't do it.

Does anyone know the down mass "efficiencies" of
airbags vs. rocket powered active landing? It
seems to me that if you're doing a rover you
get more bang for the buck with airbags.

"Stuf4" wrote in message
m...

Neil, this statement strikes me as very confused. You seem to be
saying that airbags *can't* be used for landing on the Moon. And then
you seem to be saying that *powered descent* is the method of choice
for landing on Earth.

Well, I really meant 'parachutes + airbags'. And aircraft generally use
their engines to help them land.

"Peter Stickney" wrote

Pat Flannery writes:

wrote:

Neil Gerace wrote on Sun, 25 Jan 2004 13:11:06
+0800:
:NG Strong signal, still rolling around on the surface though

Rolling along like the Energizer rabbit, it seems.

The inflatable landing bags seemed pretty wild-man crazy when they first
tried them on Pathfinder...but they've worked 3 for 3 now, and we have
an apparently quite reliable means of putting payloads on the surface of
Mars- combined with the probe design and whole landing technique, we now
have a great "Basic Bus" ability to get payloads to the Martian surface
with reliability...now if _I_ were deciding how things go from here...we
freeze the design for the landers, add different payloads, and go with
the Delta IIs for a while, then start stacking them in multiples on
Delta IV's or Atlas V's...lets put down a _whole gridwork_ of probes on
Mars; either using RTGs or trainable solar panels, and have a look at
this place say ten or twenty degrees of latitude by longitude at a time!
And MAKE SURE that that what's-his-name in the American flag shirt and
broom takes good care of them, and brings both to all future landings.
I'm not superstitious ...but I do remember Apollo 13...

Airbags are 3 for 4, aren't thay, I seem to recall that Beagle 2 was
an airbagger. And we don't know just when/where it failed, yet.

Otherwise, it seems like an Idea.

From Bob Morrell:

well, we could be picky and say American airbag systems are 3 for 3 (in fact
i think someone at JPL said that this morning)

I would not be so quick to disassociate Beagle2 from America. The
Beagle2 airbag droptests had been conducted at the Johnson Space
Center (tested many moons ago in their huge vacuum chamber - the same
vacuum chamber that's made its way into several Hollywood movies).

JPL folks should be aware of that.


~ CT

Neil Gerace wrote:


I thought America hated the French, I mean Freedoms?


We LOVE freedom...in the physical sense...we are constantly screwing
with it. As for the French- who gave us a giant copper statue of a ugly
woman in a bathrobe as a gift because they "knew we didn't have one of
those"- the straight poop (or merde) on _them_ can be found he
http://www.nationallampoon.com/nl/02...oreigners8.asp

Pat

"Neil Gerace" wrote in message
u...
I thought America hated the French, I mean Freedoms?

French fries
French kissing
French Stewart
High school hottie French teacher

No, "hate" is a bit strong.

In article ,
Christopher M. Jones wrote:
I was under the impression that the airbag system could
cope to a decent degree with failures of one or more of
the bags. So a single sharp rock wouldn't do it.

If it's sharp enough, it will -- the multiple airbags have limits.
The odds are good but it's not a certainty.

Does anyone know the down mass "efficiencies" of
airbags vs. rocket powered active landing? It
seems to me that if you're doing a rover you
get more bang for the buck with airbags.

Nope, sorry, wrong. Intuition is *WRONG* here. It was originally hoped
that the airbags would be, indeed, light and simple. Then they turned out
to need redundant bags, and a deflation system, and winches to reel the
bags in, and braking rockets, and a radar altimeter to trigger the braking
rockets, and steerable rockets to cancel wind drift, and a descent camera
system to measure the drift rate, and and and... In the end, they eat
rather more of the total spacecraft mass than a rocket landing system.

The 2009 rover will use rocket landing.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

On Mon, 26 Jan 2004 05:12:25 GMT, (Henry Spencer)
wrote:

The 2009 rover will use rocket landing.

....Don't hold your breath on this one, Henry. From what I've heard
through the undercurrents, there's apparently some push within NASA &
JPL to consider converting this to airbags. The determining factor is
whether or not pinpoint landing's that important when you look at the
big picture.

OM

--

"No ******* ever won a war by dying for | http://www.io.com/~o_m
his country. He won it by making the other | Sergeant-At-Arms
poor dumb ******* die for his country." | Human O-Ring Society

- General George S. Patton, Jr

"OM"

(Henry Spencer) wrote:

The 2009 rover will use rocket landing.

...Don't hold your breath on this one, Henry. From what I've heard
through the undercurrents, there's apparently some push within
NASA & JPL to consider converting this to airbags. The
determining factor is whether or not pinpoint landing's that important
when you look at the big picture.

OM

Hmm. This is hard to believe. I can't recall for sure, but I think the 2009
rover is way bigger and heavier (some reports say it is more like a minivan
http://www.spacedaily.com/news/mars-general-04d.html). I think the airbag
system is great, being 3 for 4 in Mars landings for these smaller landers.
But where's the break point in weight where powered descent becomes a better
(or the _only_) option? Powered descent has been used on Viking and MPL,
and how many other probes that went to the moon (and others)? [The MPL
failure is a probably understood failure.] I suspect the 2009 rover will
easily cross the line, and that powered descent is really the only option.

In this case, too, I think pinpoint landing is perhaps desirable, but more
importantly, hazard avoidence would be paramount.

Jon

(Henry Spencer) wrote in message ...
The 2009 rover will use rocket landing.

Does a rocket chemically contaminate the soil near the point of landing?

Is soil heated to any significant degree?

The only other thing is that a rocket landing will disturb or blow away any dust.

If all future landers have mobile sensors (rovers) none of this seems important.

In article ,
James Van Artsdalen wrote:
The 2009 rover will use rocket landing.

Does a rocket chemically contaminate the soil near the point of landing?

Potentially somewhat. This was a concern for Viking, if memory serves,
which is why its engines had an odd array-of-small-nozzles configuration
and specially purified propellant.

Is soil heated to any significant degree?

Not much. It's exposed to the rocket plume at close range only very
briefly.

If all future landers have mobile sensors (rovers) none of this seems
important.

Quite so. Surface mobility is a big advantage for most any lander, and
being able to get away from landing-related surface disturbances is one
of the reasons.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |