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ExoMars
djellison
post Dec 20 2007, 08:50 AM
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QUOTE (vjkane @ Dec 20 2007, 01:15 AM) *
In my opinion, I'd fly MSO in 2013 to support ExoMars,


I wouldn't. There is no certainty that ExoMars will fly. Offer relay with available assets, sure, but don't spend many hundreds of millions of dollars to support a mission that might not fly, and if it doesn't, may well not work. There's being an international partner...and there's going out on a limb.

MSR may be expensive, but MSO and two AFL's don't come cheap either. There will be the '11 orbiter, MRO, MODY and MEX ( with decreasing likelyhood of still being active from left to right ) for ExoMars relay.

Doug
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monitorlizard
post Dec 21 2007, 08:58 AM
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Flying MSO to do mostly relay and a little science wouldn't be worthwhile, IMO. But if you could do something like, say, fly an imaging SAR on MSO and have the SAR antenna do double duty as part of a high-capacity data relay system, then MSO becomes a much more attractive mission (for ExoMars, AFL, even a surface network). I believe Magellan was an example of being able to use a SAR antenna for multiple purposes.
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ustrax
post Jan 30 2008, 11:54 AM
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QUOTE (Mariner9 @ Dec 19 2007, 07:40 PM) *
I'm not sure that there is an orbiter in the latest ExoMars proposal.


It is not... smile.gif
It is expected that MRO and their sucessors do the data relay work.
Another thing, it appears that the possible Russian participation is far from happening since Jorge Vago, ExoMars Project Scientist told me that the baseline points to an Ariane 5 ECA launcher...
He also described the landing process...cool...and with some details I wasn't aware of...like this one:
"The Composite (Carrier + Descent Module) will arrive to Mars in late 2014.
It will go into a parking orbit and wait there approximately 1 year, until the atmospheric conditions are optimal for landing (sufficient atmospheric density and no danger of dust storms).
Then? The Composite will execute a manoeuvre at apogee to retarget the spacecraft for the entry trajectory. Two days later, the Carrier will separate the Descent Module, which will then enter the atmosphere."

One year in orbit?...doing what?...Man...forgot to ask about that... rolleyes.gif


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djellison
post Jan 30 2008, 12:10 PM
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Skycrane AND Airbags AND an orbiter that gets thrown away AND a year long wait on orbit.

AND making the assumption that MRO/MEX/MODY will be in a position to offer relay, 8 years from now without providing any alternative of our own.

huh.gif

I really am sorry to sound so negative about Exomars...it just seems like the wrong way to be going - lots of decisions that seem to be inappropriate compromises to problems that should be engineered out of the equation. I really really don't want to see ESA spend this much money and get it wrong, and I think they are. Big Kudos to Ustrax for getting us some lovely juicy details!

Doug
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ustrax
post Jan 30 2008, 12:16 PM
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AND...although I'm an optimistic one...did you see that there is something that I haven't read before?...A reference to 2016?... wink.gif

Kudos?...I'd rather have a beer paid in the nearest pub... tongue.gif


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Mariner9
post Jan 30 2008, 03:10 PM
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QUOTE (djellison @ Jan 30 2008, 04:10 AM) *
Skycrane AND Airbags AND an orbiter that gets thrown away AND a year long wait on orbit.


I don't think there is a Skycrane in the most recent ExoMars design. That word was used in the article, but I don't think it was an accurate term. The description given was of a rocket motor firing and stopping the lander 30 meters above the ground, then releasing the lander and having it drop the last 30 meters.

That is almost exactly how Pathfinder and MER landed. The Skycrane of MSL hovers over the ground and lowers the lander (gently, so they claim) to the surface.

But as for the rest of it.... I think you hit the proverbial nail on the head.

A long, long time ago a lot of us were saying that this mission was too big a jump for ESA to make from Mars Express, and that 600 million Euros was a fantasy budget. They've since wised up about the budget, but that still leaves me wondering about the wisdom of trying to jump from "orbiter derived from Rosseta" to "a mission far grander than MER".

So far the mission has slipped from 2011 - 2013. I've gotta wonder if it will slip furthur. If it does, I hope it also gets a bit more modest in scope, but I'm not holding my breath on that one.
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djellison
post Jan 30 2008, 03:23 PM
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" The last stage of the descent is performed with throttable liquid rocket engines which will compensate the horizontal wind component and stop the Descent Module in mid air, about 10 m from the ground. The Lander will then be dropped and the Descent Module backshell will fly away."

That's a liquid fueled, actively guided decent stage. Maybe it doesn't hover like the MSL decent stage (although 'stop in mid air' is a pretty accurate description of MSL) , but it's a lot more like MSL than the RAD's of the MER design.

Doug
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centsworth_II
post Jan 30 2008, 04:38 PM
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I'm confused. Are we for or against the notion that Skycrane is a name for the decent
stage as opposed to just being the name of a maneuver performed by the decent stage.
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edstrick
post Jan 30 2008, 05:06 PM
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Part of the "Skycrane" idea is lowering the lander to touchdown on a cable from the hovering crane.
The described system is more like a smart, capable, liquid fueled, horizontal velocity nulling MER backshell system than a true skycrane.
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djellison
post Jan 30 2008, 05:54 PM
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As described, it's the MSL decent stage, without a winch. It will have to tick almost all the same engineering boxes required for the skycrane manouver. It's much much closer to MSL than MER. One could argue that MSL is just a smart, capable, liquid fueled, horizontal velocity nulling MER backshell system....with a winch. The moment you decide to come to a standstill, and intelligently throttle out the cross-terrain speed, you're basically building Viking/MPL/Phoenix etc

(the hardware is decent stage, the maneuver is skycrane, although even I say skycrane in error half the time biggrin.gif )
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monitorlizard
post Jan 31 2008, 01:06 PM
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ExoMars is going through the same kind of teething pains that MSL did. Early in the planning stages, MSL was going to travel hundreds of kilometers across Mars, operating 24 hours a day, with a high degree of autonomy. It reminds me of that famous phrase "A man's reach should exceed his grasp, else, what's a Heaven for?"
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djellison
post Jan 31 2008, 01:12 PM
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QUOTE (monitorlizard @ Jan 31 2008, 01:06 PM) *
Early in the planning stages, MSL was going to travel hundreds of kilometers across Mars, operating 24 hours a day


Really? Where did you read that? I've never seen MSL described as driving at night, or driving hundreds of KM.
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monitorlizard
post Jan 31 2008, 01:26 PM
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I didn't say MSL would drive at night, I said it would operate 24 hours a day. With the RTG, the analytical instruments would have operated as well at night as during the day. However, that was in the early planning stages, I'm not sure what the current plans are.
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djellison
post Jan 31 2008, 02:35 PM
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Even at UMSF, we've had explanations as to the likely operating schedule for MSL, and it's surprising similarity to MER ( do stuff, then charge )

People may have presumed ( as I did at first ) that an RTG means it's a 24 hour science party - but it isn't - and I don't think MSL was ever actually expected to be.

Doug
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ustrax
post Jan 31 2008, 04:06 PM
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Oh Doug...You're gonna love this... rolleyes.gif


You guys are all invited, I expect heavy artillery from this side... laugh.gif
Prepare your ammunitions!

EDITED: btw, I have posted today a graphic showing the instruments to be part of the Rover, for now...


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