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An Xtra leg for Xtra power for Xtra imaging !, Tilting Phoenix for Xtra weeks of activity before winter...
vikingmars
post Jun 4 2008, 07:47 PM
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smile.gif My dream would be the SSI seeing the built-up of heavy patches of frost around Phoenix during the autumn before her winter shut-off...
... with some gathering of meteorological data as well !
I was impressed to see how quick the energy available will drop before the autumn equinox
(see link : http://www.unmannedspaceflight.com/index.p...t&p=116809)

Knowing that the Robotic Arm (RA) is strong enough to lift the lander, why not using it as an Xtra leg to tilt her to gain Xtra sunlight on its solar panels and, thus, some Xtra weeks of imaging and meteo activities ? wink.gif
Rationale :
- Anyway Phoenix will die from cold : no survability is expected after winter ;
- After an extensive use for trenching, the RA will thus no longer be useful, except from being parked ;
- could the RA be parked in any position ?
- Luckily the RA is almost facing north...
Then, why not using it to push firmly on the Martian surface to tilt the Lander towards the south, to help her solar panels receive Xtra weeks of sunlight ?

==> Tilting Phoenix with the RA for Xtra weeks of activities : a feasible dream ? rolleyes.gif
What are the opinions of our s/c hardware specialists ? Was it discussed before ?
(...and, please help, help MarsEngineer ! ohmy.gif )
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Guest_Oersted_*
post Jun 4 2008, 08:06 PM
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good job thinking outside the box!
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kungpostyle
post Jun 4 2008, 08:12 PM
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It would be cool but I doubt the arm has the strength.

How about firing the remaining propellant through the southside thrusters to melt the ice on that side of the lander thus tipping it in a southerly direction?


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vikingmars
post Jun 4 2008, 08:28 PM
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QUOTE (kungpostyle @ Jun 4 2008, 10:12 PM) *
It would be cool but I doubt the arm has the strength.


==> Here is the answer from Peter Smith himself (Phoenix Mission PI) :
"Peter Smith said...
The robotic arm is 2.35 m long and powerful enough to scrape into hard materials. It is true that if the spacecraft footpad perches on a rock or is otherwise unstable, then the RA has the strength to move the lander. We often joke that landing on ice in low gravity will allow us to pull ourselves along the surface using the RA from rock to rock..."
(source : http://spaceurope.blogspot.com/2008/04/pho...with-peter.html ) smile.gif
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pioneer
post Jun 4 2008, 08:39 PM
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QUOTE (kungpostyle @ Jun 4 2008, 09:12 PM) *
It would be cool but I doubt the arm has the strength.

How about firing the remaining propellant through the southside thrusters to melt the ice on that side of the lander thus tipping it in a southerly direction?

Wasn't the remaining propellant purged after landing?
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Guest_Oersted_*
post Jun 4 2008, 08:45 PM
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The question of using the rockets was discussed in this thread a couple of weeks ago:

http://www.unmannedspaceflight.com/index.php?showtopic=5134

The retro rocket tank pressurization helium was vented immediately upon landing.
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climber
post Jun 4 2008, 08:55 PM
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This is a great idea. They'll have to chose between using the energy needed to lift versus what can be done with this energy otherwise.


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djellison
post Jun 4 2008, 09:00 PM
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I can pull myself along easily with one arm.

I can't do pull-ups with one arm though.

Doug
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vikingmars
post Jun 4 2008, 09:21 PM
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QUOTE (djellison @ Jun 4 2008, 11:00 PM) *
I can pull myself along easily with one arm. I can't do pull-ups with one arm though. Doug

Yes, Doug you are damn right : you are 4 "legged" and, indeed for this excercize, you need both arms to do pull-ups ...
It's should be more easy for Phoenix which have only 3 legs. This solution means an RA lift in front of the northern leg, the 2 others resting firmly in place towards the south...
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Ant103
post Jun 4 2008, 09:31 PM
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Or they could try to dig under one foot of the lander, about 30-40 cm or more to have a signifiant tilt. huh.gif


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climber
post Jun 4 2008, 09:35 PM
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QUOTE (Ant103 @ Jun 4 2008, 11:31 PM) *
Or they could try to dig under one foot of the lander, about 30-40 cm or more to have a signifiant tilt. huh.gif

I guess you'll have to get there to put the arm on the other side of the deck first wink.gif


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helvick
post Jun 4 2008, 10:26 PM
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It's an interesting out of the box idea but I don't think it would make a major difference.

Here's a comparison of the amount of power available as she is actually oriented (0.5deg) and with a fairly extreme 15 degree southerly tilt. That tilt would gain Phoenix somewhere from 5-10% increase in power during the Sol 100-200 period but that gain only lasts until around Sol 260 and both charts effectively hit zero at the same time ~ Sol 300. If Tau rises (as I think it probably will in the Sol 200-Sol 300 timeframe) then the benefits from tilting would be significantly reduced.

Attached Image

Attached Image


The fundamentals are based on assumptions detailed over the in the Sun Angle thread so my estimate of absolute power levels might be quite a bit off but the comparison between the two tilts should be more or less valid regardless of the other assumptions.
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Guest_Oersted_*
post Jun 4 2008, 10:54 PM
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What we should rather do is having the arm grab the solar panels and twist them into position... huh.gif laugh.gif
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MarsEngineer
post Jun 4 2008, 11:32 PM
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Hi Vikingmars!

Your suggestion about using the arm to move the lander is a good one ... we have talked about doing that over the years but mostly in jest. It is not that the idea is bad or goofy in any way, it is just that in order to even have a serious conversation about something like that, we first had to get the vehicle to do the primary things it needs to do (cruise to Mars, land, dig, analyze, etc). Since we have been struggling getting those other things done in time, any "bonus" ideas team members offered were typically only coffee pot conversations said with a smile.

To be honest I have no idea what the hardware risks are associated with using the RA to move the lander, but I would not be surprised if there were risks that would have to be assessed and overcome (e.g. lateral loads exceedances). As the months go on, after the primary mission objectives are met, it is not inconceivable that the team would consider testing and using the hardware in unplanned ways. Just before Pathfinder died we were looking into raising a lander petal to see if the dust on the solar array would fall off. Also, as you recall we had no idea that we could safely drive a rover straight down into a crater (Endurance) with 25-30 deg slopes! We found out that it was possible and safe via testing at Earth using a Mars-weight rover. While these sorts of capability extentions or enhancements are not at all uncommon for our missions, they are usually associated with activities that bring higher mission science return (where the benefits outweigh the risks). You suggestion may be one of those ...

But hold the thought, let's scrape some (purported) ice first!

-Rob
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AndyG
post Jun 5 2008, 08:33 AM
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QUOTE (djellison @ Jun 4 2008, 10:00 PM) *
I can't do pull-ups with one arm though.


...Betcha could under 1/3g! rolleyes.gif

Andy
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