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MSL FAQ - The pool of questions
djellison
post Jun 1 2007, 03:11 PM
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Rob Manning and I swopped emails last night - and we think it might make sense to pool all the questions people have about MSL (and specifically MSL's EDL ) into one thread - and then answer as many as make sense either via a Q'n'A in the style of the previous ones I've done with Steve and Jim - or via Rob's typing fingers.

It'll be a few weeks till we sort this out - but submit-away until then smile.gif

Doug
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elakdawalla
post Jun 1 2007, 05:11 PM
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Doug and I had the same idea -- he got to Rob first! -- but hopefully you'll also see Rob's responses in the future as a guest blogger.

Anyway, I'll start with one: in this post, Rob, you said:
QUOTE
(I have heard many a puzzled observer wonder why we are headed toward even more RubeGoldbergian designs. Rather than blame ever-cannonball polishing engineers like me, I would rather blame that frustrating Red planet that beckons us. Someday I will share the genesis of the Skycrane design concept - you might not be surprised that we conjured this - and other new designs in early 2000 in the wake of the MPL loss in late 1999.)
Please share!

Emily


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Juramike
post Jun 1 2007, 06:03 PM
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My Big list 'o Questions:

1) How scalable is this? How big (mass) a package could it deliver?
(Could you put down a future habitation module on Mars, deep drilling rigs, other cool stuff?)

2) Could you use it to put down multiple instruments in different (but fairly close, locations?)
[OK, you’d need to upgrade to more propellant, brains in the platform, and deal with COG issues]

3) Could you use it to move an instrument already on the surface to a new location?
[lotsa propellant, more brains in the platform, getting the rendezvous and “hook up” – but heck, the stability, lowering problems will already have been solved] (Imagine if we could send a Skycrane pick up Oppy and move her to another location within a 200 km radius – this would really change the post-Victoria discussion!)

4) Could it be used to deliver other packages down on other (airless) planetary surfaces?
[no chute, but using much, much more retro]? (Europa, for example).


5) Will it be possible to (exhaustively) test the Marscrane system on Earth before the big test on Mars?

-Mike


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akuo
post Jun 1 2007, 07:43 PM
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Ok, here is my question:

MSL is not limited by electrical power as much as previous rovers. The RTG will provide a constant current, though AFAIU batteries are still needed when power needs are higher.

Taking this into account, for how long time could MSL rove during a sol? Is it possible to move even during the night?


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Jim from NSF.com
post Jun 1 2007, 09:16 PM
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QUOTE (akuo @ Jun 1 2007, 03:43 PM) *
Ok, here is my question:

MSL is not limited by electrical power as much as previous rovers. The RTG will provide a constant current, though AFAIU batteries are still needed when power needs are higher.

Taking this into account, for how long time could MSL rove during a sol? Is it possible to move even during the night?


MSL operates off the batteries and the MMRTG recharges them. It will operate about 7 hours per sol
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Stu
post Jun 1 2007, 09:17 PM
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Apart from the obvious question that springs to mind after watching that new animation... "What were you guys smoking when you came up with the idea of the Skycrane?!?!?!?"... tongue.gif ... here are a couple, and apologies in advance if these have been answered elsewhere, but I can't remember reading the answers, and anyway, new people join UMSF all the time so these questions will be new to someone out there...

Will we be getting "video clips" from MSL?

In the light of the success of the "purely scenic" images taken during the NH Jupiter flyby, will MSL be programmed to take any similar images ("pretty pictures" as someone calls them... wink.gif ) purely for Outreach value and media appeal? Maybe dedicated imagery of Earth-in-the-sky scenes? We (and by "we" I mean we frontline Outreach troops who spread the word) really need a classic, colour, "Earth in Mars'sky" image please, thank you... smile.gif

How much more advanced will MSL's imaging instruments be than MER's?

Ta.


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djellison
post Jun 1 2007, 09:45 PM
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QUOTE (djellison @ Jun 1 2007, 04:11 PM) *
(and specifically MSL's EDL )


unsure.gif

Although hopefully we could find someone to do those other questions.
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nprev
post Jun 1 2007, 11:35 PM
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Okay, I got two:

1. How exactly is the MSL/crane separation sequence initiated? Does MSL have something like aircraft "weight-on-wheel" switches that tell the computer it's down, and therefore safe to cut the cords?

2. Is the crane in fact commanded immediately at separation to do a tilt & escape maneuver as shown in the animation? (In other words, since I gather it has no brains of its own, how is it told to vamoose instead of possibly hovering right over MSL until it runs out of fuel...?)


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dvandorn
post Jun 2 2007, 12:45 AM
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And here's a few more to add to nprev's:

3) What happens if the rover touches down before the belaying lanyards have been fully extended? Especially what happens if one wheel of the rover hits a decent-sized rock before the lanyards have been fully extended?

4) Is the cable/lanyard separation accomplished via a signal in the lander (i.e., a contact sensor of some kind), or in the crane (a slack cable signal)? If it's a slack cable signal, can we be certain that any unexpected buffetting encountered by the rover won't accidentally set it off?

5) Are we certain there won't be enough engine blowback from the surface to set the rover into motion, perhaps so much motion it will tip over at wheels-down? Has the landing-on-a-slope case been considered in this regard, where a given slope (or even badly placed rock) could reflect engine exhaust in such a way as to destabilize the rover?

6) Has the general issue of slopes been addressed? What happens if the rover has a small but significant sideways motion at touchdown (due to substantial winds, I would guess) and that direction just happens to be downslope -- of a significant slope (like 20 degrees or more)?

7) Will MSL's obstacle avoidance capability be able to recognize slopes (hills and craters) as well as blocks?

OK -- I think that's enough for now -- smile.gif . Thanks for being willing to address some of these questions, Rob!

-the other Doug


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Stu
post Jun 2 2007, 05:14 AM
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QUOTE (djellison @ Jun 1 2007, 10:45 PM) *
unsure.gif

Although hopefully we could find someone to do those other questions.



Okay, okay, I didn't read the brief properly. Please file my questions until a more appropriate opportunity.


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Toma B
post Jun 2 2007, 06:43 AM
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Thanks Doug!
Here are my questions:

a ) Tests of Skycrane on Earth:
1 ) Is there a plan to do at least one full scale test of the descent stage using as close as possible to flight hardware?

2 ) When and where will these tests be undertaken?

3 ) Is there an almost finished Skycrane NOW somewhere in labs? (I don't intend to steel it :-))


b ) How long can it work once it is released from backshell?
1 ) How much fuel does it carry?

2 ) What is Skycranes thrust to weight ratio at full throttle?

3 ) At what height is Skycrane released from the backshell?


c ) How far away will Skycrane crash after releasing MSL-lander? (I know this cannot be answered precisely)
1 ) Is it possible that Skycrane will (almost) soft land?

2 ) Is there a plan to visit it after or is that for any reason dangerous?


Thanks again for the opportunity to do this? Sorry for my English.....

P.S.
I love this place....


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Eluchil
post Jun 2 2007, 06:46 AM
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Here are a few Rob might know the answers to:

1) When is the MARDI descent movie expected to be downlinked?

2) What on-orbit assests are expected to relay telemetry during EDL; can others be substituted if they are unavailible?

3) Are the testing facilities for the parachutes and whole EDL systems adequate or would full on upper atmospheric tests be useful?

Eluchil
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djellison
post Jun 2 2007, 07:53 AM
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There's a few questions that I think I can do a bit of an answer about for now:

Lots of the same question - full scale test of the whole thing. That's not even possible on Earth - that's what makes landing on Mars so hard - you can't practice. You can try and do a chute deployment on Earth using low wind speed at 1000 mbar - similar dynamic pressure to deploying on Mars - but it's not exactly the same. There was a RFP for a large rig to simulate the decent stage from which they would hang a mobility model to test software and the physical process ot touchdown - including slopes. You can test fire engines - you can simulate sloshing or other harmonic issues with pressurised water - but there's no way to simulate the whole thing...you just test systems as best you can - the simulate the system of systems virtually. VKG, MPF, MPL, MER, PHX - none had a full up system test of everything - because you just can't do it here.

MARDI movie will be downlinked.....after landing. Product downlink priorities for data to be taken in three years time - that's a bit premature isn't it smile.gif I'm sure it will be something of a priority from a EPO perspective - but it'll be a big data product so it may take some time.

EDL comms will be to MRO and - if it's still around - Odyssey as well I would have thought - the same as Phoenix.

And here's the great thing about UHF, MRO and MSL ( and I'm hoping a DESCANO report on this - and the Phoenix one - will happen )

MER2Ody is 128k - or 256k if it's a good pass - typically 10-15 minutes - 50 to 150 Mbits in a pass.

MSL2MRO can be up to 2048k - shorter on average than MER passes with Odyssey - but still potentially up to 1000 Mbits or more in a pass.

Doug
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helvick
post Jun 2 2007, 09:16 AM
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I presume you mean MSL2MRO there.
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djellison
post Jun 2 2007, 09:39 AM
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Yeah - that what I said.

laugh.gif

Cough ahem oops well spotted. smile.gif


Doug
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