[X] My Assistant

[Guest_Oersted_*]

OK, premature, premature, but still... After a succesful landing and thouroughly having dug holes and trenches in the original working volume of the arm: how about moving about a tiny bit? - I was wondering if the rocket engines could possibly be used to shift position just a few decimeters at a time. Small blips, which should be so weak that they wouldn´t overturn the lander.

It could also come in handy when the snows come in later in the year and threaten to bury the lander.

A few things would be necessary: no post-landing venting of possible excess fuel (who knows about that?). No permanent disabling of the rockets after EDL. A possibility to stow and unstow the solar panels (ok, that is probably a show-stopper, but just humour me here...). The last would only be an issue if it was thought that small blips of the rockets would raise sufficient dust to degrade the solar panels´efficiency.

Just thinking out of the box here... - And I know it very probably won´t ever happen. But if!

- Well, let us just get this baby down in one piece for now.

[kwan3217]

As noted before, once the helium vents, Phoenix is where it will be when the next expedition will find it. Besides the helium, once the panels are deployed (one-way) the balance is thrown off.

But, does it make any sense to have a capability like this? I can see some lander landing, then using its cameras to see a spot 20m away where there is ice on the surface or a tree growing, then hopping over there. Phoenix is predicted to only use 40-45kg of the 67kg of propellant loaded. It should be possible to fly 20m or so with the fuel left. Once it's on the ground, if it were to fly again its landing ellipse would be meters or centimeters across instead of kilometers.

And why is the helium vented so soon after landing? It must be really high priority to be that early.

[djellison]

And why is the helium vented so soon after landing? It must be really high priority to be that early.

It makes sense, I guess, to get rid of any pressure as soon as possible, so that fuel line heaters etc can be turned off and not bothered with again. While the system is still pressurized, you can't let the fuel freeze, which it would do quite quickly, I would have thought, with -60degC outside or whatever it will be. Just guessing, but that's my take.

I would rate the chance of seing a tree growing as somewhat slim (particularly given that such a thing would be easily visible from HiRISE)

The point with Phoenix is that you really don't need mobility. The science is right under your feet wherever you end up. If you need mobility - rockets are a dangerous, heavy complex and unpredictable means of doing it. For missions that need mobility ( MER, MSL ) then they've got it.

Doug

[Guest_Oersted_*]

The point with Phoenix is that you really don't need mobility. The science is right under your feet wherever you end up. If you need mobility - rockets are a dangerous, heavy complex and unpredictable means of doing it. For missions that need mobility ( MER, MSL ) then they've got it.

Doug

I think that is just plain wrong, the argument about not needing mobility. We can be in the very fortunate situation that everything is right where we want it, but it also might possibly not be the case.

The rovers have shown us that mobility is the only way to go. Those little wheels have enhanced the science return immeasurably. Even Phoenix would be able to to do ten times more science with just limited mobility. It is a left-over from another, more limited, era of space exploration.

[Alex Chapman]

I think that is just plain wrong, the argument about not needing mobility. We can be in the very fortunate situation that everything is right where we want it, but it also might possibly not be the case.

The rovers have shown us that mobility is the only way to go. Those little wheels have enhanced the science return immeasurably. Even Phoenix would be able to to do ten times more science with just limited mobility. It is a left-over from another, more limited, era of space exploration.

You really can’t underestimate the ‘vertical mobility’ that Phoenix has. Most of the scientific discoveries made by the MERs have been due to looking under the dust covered surface of Mars. Opportunity’s evidence for a past damp Mars is through rock stratigraphy exposed by craters and Spirit has used the meagre trenching ability of its wheels to expose sulphates.

Phoenix is the first lander that will be able to see virgin material that has not been directly exposed to the Martian atmosphere. It’s going to be able to dig down to up to 0.5m! If Opportunity had been able to do that and look at samples as it dug down it would have made most if not all of its discoveries without the need to drive.

[simonbp]

Phoenix is the first lander that will be able to see virgin material that has not been directly exposed to the Martian atmosphere. It’s going to be able to dig down to up to 0.5m!

Really? It may be "summer", but they are landing on permafrost. When asked Chris McKay earlier this year, he said maybe the first few centimeters...

WRT mobility, I have to disagree, Doug. The area the arm can reach is probably going to be pretty homogeneous, and a Surveyor-style hop may be enough to get to a different-looking place. Five TEGA runs of the same sample don't produce much more science than a single run.

Also, remember that Mars is a low-gravity environment (0.38g), so the fuel requirements are not as egregious as a terrestrial rocket...

Simon

[djellison]

Also, remember that Mars is a low-gravity environment (0.38g), so the fuel requirements are not as egregious as a terrestrial rocket...

It's not going to happen with Phoenix, remember that. 5 seconds after landing, the prop is depressurized. And if you want mobility on Mars, rockets are a very inaccurate, dangerous, complex and heavy way to do it.

And I'm still going to maintain - Phoenix has a full 90 sols planned investigating where it lands. There is no evidence to suggest there is science to be gained by moving horizontally. I am somewhat concerned that a few people here don't know what Phoenix is about at all.

Doug