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MRO MOI Events Timeline, Time Zone Friendly
Guest_BruceMoomaw_*
post Mar 11 2006, 11:07 AM
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I imagine the single biggest sigh of relief came from Dennis McCleese. He must feel like Charlie Brown after Lucy finally allowed him to kick the football.
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djellison
post Mar 11 2006, 11:35 AM
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QUOTE (RNeuhaus @ Mar 11 2006, 01:14 AM) *
Maybe there are 6 orbiters


But not 'operating' at mars.

Doug
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jmknapp
post Mar 11 2006, 01:22 PM
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One of the trajectory guys said on NASA TV yesterday that with the fuel they saved by not needing any course adjustments since last November they potentially extended the life of MRO by 9 months. They sure earned their pay (and maybe a bonus) for that accomplishment.


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deglr6328
post Mar 11 2006, 02:37 PM
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QUOTE (djellison @ Mar 10 2006, 10:55 PM) *
Burn time 1641 seconds vs 1606 expected. 1000.48 m/s compared to 1000.36m/s expected.

So burn performance 97.87% of nominal, but actual Delta V 100.012% of predicted.

i.e. yes - the burn was a little under the mark, but the onboard sequence saw this, worked off the Delta V, and terminated the burn according to the accumulated Delta V hitting the right mark.

Doug



This is really most fantastic. We are talking about a target change in velocity of over 2,200 mph and it was achieved to within a few inches per second!! that's some good engineering.
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RNeuhaus
post Mar 13 2006, 03:26 PM
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QUOTE (Bob Shaw @ Mar 11 2006, 06:05 AM) *
Rodolfo:

There may be some Soviet vehicles still there, too. I doubt if they've all decayed so soon!

Bob Shaw

All Soviet (not very sure, need more time to search about this to confirm), one Japan and all Mariner for Mars except one has flown by Mars and they are orbiting around the Sun. So now, there is 7 orbiting around Mars, three are inoperative (Vikings I, II and Mariner 9). In resume, up to know there is 65 % of MOI to Mars with success.

Rodolfo
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ljk4-1
post Mar 13 2006, 03:35 PM
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QUOTE (RNeuhaus @ Mar 13 2006, 10:26 AM) *
All Soviet (not very sure, need more time to search about this to confirm), one Japan and all Mariner for Mars except one has flown by Mars and they are orbiting around the Sun. So now, there is 7 orbiting around Mars, three are inoperative (Vikings I, II and Mariner 9). In resume, up to know there is 65 % of MOI to Mars with success.

Rodolfo


I know that Mariner 9 and the Vikings were placed in orbits around
Mars in part to stay up for at least 50 years to "remove" any micro-
organisms that might have survived on them.

The Soviet probes Mars 2, 3, and 5 were successful orbiters, but I
do not know if they are still in space or how well they were sterilized.

Phobos 2 did get into Mars orbit in 1989, but I read that it might
eventually crash into the moon it is named after. Anyone have an
orbital plot on this?

Mars 4 was supposed to orbit the Red Planet, but its braking rockets
failed. Mars 1, Zond 2, and Mars 6 and 7 were all flybys (the latter
two and possibly three with accompanying landers).


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"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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Guest_AlexBlackwell_*
post Mar 13 2006, 06:52 PM
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QUOTE (BruceMoomaw @ Mar 11 2006, 11:07 AM) *
I imagine the single biggest sigh of relief came from Dennis McCleese.

Who's that? Dan McCleese's son/nephew/uncle/grandfather?
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The Messenger
post Mar 13 2006, 07:46 PM
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QUOTE (AlexBlackwell @ Mar 13 2006, 11:52 AM) *
Who's that? Dan McCleese's son/nephew/uncle/grandfather?

John Cleese's Irish cousin smile.gif

The 2% lag in performance - Any clues as to why? TCM-2 was much more precise, or was there a performance correction during the burn as well?
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Circum
post Mar 13 2006, 08:05 PM
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The 2% lag in performance - Any clues as to why? TCM-2 was much more precise, or was there a performance correction during the burn as well?
[/quote]

During the NASA TV coverage, I believe I heard something about chamber pressures being slightly low, which was not a complete surprise since certain temperatures were also slightly low.

I didn't hear any explanation or further details about the low temperatures, but somehow I doubt it was 'new physics'. . . .

Also, could someone with more propulsion knowledge step in, I somehow have the impression that MOI was the first time they had pressurized the chamber, so did the TCMs use a different mode or different engines or something?
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djellison
post Mar 13 2006, 08:09 PM
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The engine's just didnt quite provide as much punch as they expected during MOI, so the onboard software commanded the shutdown slightly later than they expected it to happen.

If you're only doing a tiny nudge, a few m/sec - then it would be hard to notice a 2% shortfall in the expected performance ( I don't know if TCM 1 was done using a delta-V accumulation or a timer but either way, it'd be a tiny error on a small burn ) - whereas with a burn thats more than a thousand seconds then it's going to be a lot more obvious.

Doug
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ugordan
post Mar 13 2006, 08:21 PM
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QUOTE (Circum @ Mar 13 2006, 09:05 PM) *
Also, could someone with more propulsion knowledge step in, I somehow have the impression that MOI was the first time they had pressurized the chamber, so did the TCMs use a different mode or different engines or something?

I think this was the first and only time the propellant tanks were pressurized. The TCMs probably were run at default tank pressure, while before the MOI burn pyro-valves were opened to allow helium into the propellant tanks for pressurization. As Doug noted, the temperatures were slightly colder resulting in a somewhat lower prop tank pressure and, consequently, lower thrust.
The engines used on space probes are always pressure driven and the pressure of propellant tanks makes for quite a difference in thrust.
As a comparison, engines used on launch vehicles are turbopump driven and are vastly more complicated/expensive, but have the advantage of tanks not being required to handle great pressures (meaning they can be made light).


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mcaplinger
post Mar 13 2006, 08:32 PM
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QUOTE (Circum @ Mar 13 2006, 12:05 PM) *
did the TCMs use a different mode or different engines or something?

Yes. TCMs were done with the 22N thrusters alone, while MOI also used the 170N thrusters for the first time (press kit, page 36.)


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Disclaimer: This post is based on public information only. Any opinions are my own.
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Circum
post Mar 13 2006, 08:50 PM
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Thanks for all the info dje, ugor, and mcap. smile.gif
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Bob Shaw
post Mar 13 2006, 09:35 PM
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QUOTE (ljk4-1 @ Mar 13 2006, 03:35 PM) *
I know that Mariner 9 and the Vikings were placed in orbits around
Mars in part to stay up for at least 50 years to "remove" any micro-
organisms that might have survived on them.

The Soviet probes Mars 2, 3, and 5 were successful orbiters, but I
do not know if they are still in space or how well they were sterilized.

Phobos 2 did get into Mars orbit in 1989, but I read that it might
eventually crash into the moon it is named after. Anyone have an
orbital plot on this?

Mars 4 was supposed to orbit the Red Planet, but its braking rockets
failed. Mars 1, Zond 2, and Mars 6 and 7 were all flybys (the latter
two and possibly three with accompanying landers).


Yes; I think Rodolfo has missed the four Soviet vehicles placed in orbit around Mars, though whether they still are is another issue.

Bob Shaw


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Remember: Time Flies like the wind - but Fruit Flies like bananas!
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ToSeek
post Mar 14 2006, 06:51 PM
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QUOTE (mcaplinger @ Mar 13 2006, 08:32 PM) *
Yes. TCMs were done with the 22N thrusters alone, while MOI also used the 170N thrusters for the first time (press kit, page 36.)


That's not quite true. TCM 1 was used to check out the main engines. See this press release.
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