[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.

[djellison]

. Even Phoenix would be able to to do ten times more science with just limited mobility.

Really? With only 90 sols, 8 TEGA ovens and 4 MECA suites? At a site where all the obital data says the science we are after is essentially homgenous across the ellipse. Ten times more science? Please do explain how, exactly.

I would argue the EXACT opposite of what you say. There would be ZERO scientific benefit for Phoenix to be mobile. Would a rover in the polar plains be interesting and exciting? Yes. For most science investigations on Mars is mobility a benefit? Yes, clearly, MERA and MERB have shown this to be the case. Would a rover offer benefits for the science that Phoenix is attempting? No. Phoenix has a full schedule to conduct as thorough a characterization as it can manage within the time of it's expected life span. Phoenix is niche, it's arguably one of the few scientific missions to Mars that doesn't need mobility ( a second being the long overdue net-lander type mission).

But to claim that Phoenix would be able to do 'ten times more science with just limited mobility' is wrong - very very very wrong.

Doug

[Guest_Oersted_*]

Really? With only 90 sols, 8 TEGA ovens and 4 MECA suites? At a site where all the obital data says the science we are after is essentially homgenous across the ellipse. Ten times more science? Please do explain how, exactly.

I would argue the EXACT opposite of what you say. There would be ZERO scientific benefit for Phoenix to be mobile. Would a rover in the polar plains be interesting and exciting? Yes. For most science investigations on Mars is mobility a benefit? Yes, clearly, MERA and MERB have shown this to be the case. Would a rover offer benefits for the science that Phoenix is attempting? No. Phoenix has a full schedule to conduct as thorough a characterization as it can manage within the time of it's expected life span. Phoenix is niche, it's arguably one of the few scientific missions to Mars that doesn't need mobility ( a second being the long overdue net-lander type mission).

But to claim that Phoenix would be able to do 'ten times more science with just limited mobility' is wrong - very very very wrong.

Doug

When you stress the 90 sols argument, I think that is mainly to underscore your thesis that mobility would be of no use whatsoever to Phoenix. I agree , if the plug was pulled on Phoenix after those 90 days. With a 90 day mission, definitely one trenching operation is more than enough.

But the whole idea of this thread is to see what could be useful beyond the 90 days, if we ever get that far. And in that "extended mission" it would have been great to be able to nudge a bit of movement out of the lander. Well, it is not going to happen, obviously.

That the science would be "essentially homogenous across the ellipse"... well... I just don't believe that. Maybe on some very high scale, but - surely - on the scale that Phoenix operates, there are local differences. From one square/cubic meter patch to another! If we had two trenching operations within meters of each other and they turned out to be different, that would tell us so much more than one single trenching operation, the validity of which we can't say a lot about, because there is just this one operation.

Phoenix is legacy hardware, and it is certainly much better to have the present Phoenix than none at all. But how much does that argument advance things?

[djellison]

Phoenix is legacy hardware, and it is certainly much better to have the present Phoenix than none at all. But how much does that argument advance things?

It advanced them from not having any mission, to having a mission that will do a LOT of science. It wouldn't do '10x' the science, as you claim, if it could move, because within 5 months or so, it's going to be dead. It's going to take most of it's life to fully understand and investigate what we land on. If it could move, it wouldn't have time to do the same to a second site and the data tells us that a second site would be the same as the first. Maybe we'll get a polygon edge within the work volume - that would be a nice bonus. But for what Phoenix is being sent to do, it's purpose, it's prime goal... mobility is not in any way justified, required or 'missing'. By Sol 90 after the full characterization of the landing site, the sun will begin to set. From that point on, it's going to be camping out on ever decreasing power, on an atmospheric and surface monitoring program. Phoenix isn't going to last 1500 Sols. This is a short lived tightly focused mission for which mobility is not required.

Would it be nice to have a rover. YES. Would there be a benefit to Phoenix to be mobile? No - because it wouldn't even be on Mars - it would be on PPT's getting turned down at the scout selection phase. A lack of mobility made Phoenix possible. Lamenting that fact is moot.


Indeed, refering back to your quote ' how much does that argument advance things?' - debating mobility for Phoenix advances nothing whatsoever. There isn't a debate to be had. It's not mobile. Argument finished. I struggle to see what your point is beyond that.

Doug