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#660
by
kevin-rf
on 28 Nov, 2011 13:41
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I am not an engineer, but the modified Fregat stage may not last that long in the extremes of outer space, especially the external propellant tank, which was supposed to be expended immediately and jettisoned. I am unsure of the engineering and physics involved, but the fuel within that tank could potentially explode sitting in orbit that long creating additional space debris.
At the expense of being a party-pooper, my personal opinion is that it coming back with a time frame calculated to be January 14 plus or minus 9 days. If they can regain some control, it could be used to try and maneuver the craft such that it does not impact land or any populated areas.
While I agree with you in principal on the long term viability of drop tank, to get the the orbit described, the propellant in the drop tank would have to be used and jettison'd. So that is not an issue.
Of course the big question is, at this point, can the propellant in the drop tank still be used? Unlike the rest of the stage, what are the chances that the tank had extra insulation and heaters? What are the chances that it has already started freezing, if the probe is sun oriented with solar panels deployed that tank will at least be partially in shadow. It is not getting any solar heat.
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#661
by
alk3997
on 28 Nov, 2011 13:43
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I just noticed two visual observations described the color of the vehicle as 'orange'.
Here:
http://satobs.org/seesat/Nov-2011/0308.html
http://satobs.org/seesat/Nov-2011/0342.html
Do we have closeout photos of exterior surfaces that are orange [or gold] in hue?
Or are the observations of 'orange' connected with the color of stains from venting hydrazine [or from thruster plumes]? We saw that effect on Mir.
Has the reported color changed over the past two weeks? Let's go back and check.
Jim, checking for color change is good. Also seeing if the observation was near sunrise/sunset would provide a clue since spacecraft color can turn golden during some of that time.
Andy
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#662
by
alk3997
on 28 Nov, 2011 13:48
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I am not an engineer, but the modified Fregat stage may not last that long in the extremes of outer space, especially the external propellant tank, which was supposed to be expended immediately and jettisoned. I am unsure of the engineering and physics involved, but the fuel within that tank could potentially explode sitting in orbit that long creating additional space debris.
At the expense of being a party-pooper, my personal opinion is that it coming back with a time frame calculated to be January 14 plus or minus 9 days. If they can regain some control, it could be used to try and maneuver the craft such that it does not impact land or any populated areas.
While I agree with you in principal on the long term viability of drop tank, to get the the orbit described, the propellant in the drop tank would have to be used and jettison'd. So that is not an issue.
Of course the big question is, at this point, can the propellant in the drop tank still be used? Unlike the rest of the stage, what are the chances that the tank had extra insulation and heaters? What are the chances that it has already started freezing, if the probe is sun oriented with solar panels deployed that tank will at least be partially in shadow. It is not getting any solar heat.
Don't forget the other extreme - overheating. Overheating hydrazine is not good either. It can expand to a point where the tank will rupture or at least blow the burst disc. In the best case, this can reduce the prop available. In worst case the hydrazine finds some leaking nitrogen tetroxide.
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#663
by
seshagirib
on 28 Nov, 2011 14:04
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getting back in topic, according to the French newspaper "Le Monde", if contacts are re-established with F-G, it could be put in a high parking orbit between the Earth and the Moon, where it would wait for the 2013 window to open while engineers complete debugging its software.
http://www.lemonde.fr/planete/article/2011/11/26/espoir-pour-la-sonde-russe-phobos-grunt_1609001_3244.html (in French, evidemment...)
this is the most sensitive proposal so far (and I discussed here first a few days ago 
I imagine F-G could be sent to fly by the moon like that old comm sat Asiasat 3 or Nozomi and be perturbed in a distant resonant orbit or even a solar orbit returning to fly by the moon and Earth in late 2013 and resume the original mission as planned. I guess this could be done with the available fuel. The only problem I see (beside the non-trivial need to re-establish full control over the probe) is that Russian hardware is not known for its reliability and 2 more years in space may be too much.
I hope that orbital mechanics gurus like Farquhar and Bellbruno will be working on this
does this mean that the current problem is found to be due to buggy software, or is the reference to a potential new s/w upload for a modified mission?
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#664
by
Svetoslav
on 28 Nov, 2011 14:12
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#665
by
plutogno
on 28 Nov, 2011 14:43
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does this mean that the current problem is found to be due to buggy software, or is the reference to a potential new s/w upload for a modified mission?
the article says:
This delay should enable a verification of all the software on board, that engineers already knew to be the weakness of the mission.
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#666
by
seshagirib
on 28 Nov, 2011 15:13
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does this mean that the current problem is found to be due to buggy software, or is the reference to a potential new s/w upload for a modified mission?
the article says:
This delay should enable a verification of all the software on board, that engineers already knew to be the weakness of the mission.
looks like they atleast suspect the s/w for the current problems....though it is very difficult to understand, why they would launch anything with a known "weakness"
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#667
by
JimO
on 28 Nov, 2011 15:35
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#668
by
gregzsidisin
on 28 Nov, 2011 15:36
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does this mean that the current problem is found to be due to buggy software, or is the reference to a potential new s/w upload for a modified mission?
the article says:
This delay should enable a verification of all the software on board, that engineers already knew to be the weakness of the mission.
looks like they atleast suspect the s/w for the current problems....though it is very difficult to understand, why they would launch anything with a known "weakness"
It wouldn't be the first time something was pushed to launch due to political and/or time pressures. And Fobos Grunt had already missed one previous Martian launch cycle.
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#669
by
SimonFD
on 28 Nov, 2011 15:48
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does this mean that the current problem is found to be due to buggy software, or is the reference to a potential new s/w upload for a modified mission?
the article says:
This delay should enable a verification of all the software on board, that engineers already knew to be the weakness of the mission.
looks like they atleast suspect the s/w for the current problems....though it is very difficult to understand, why they would launch anything with a known "weakness"
Maybe "weakness" should read "relative weakness" i.e. compared to anything else in the mission. Doesn't mean to say it's ready to fall over...
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#670
by
gregzsidisin
on 28 Nov, 2011 15:52
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Hi All,
I'm a new user.
On the subject of Soviet successes on Venus vs mixed
success at Mars, perhaps the answer may be found in persistence
and timing. Soviet Russia kept shooting probes to Venus
at almost every launch window until 1984 simply because they could
afford to (not a capitalist system back then). Lessons learned
propagated forwards to the next attempt and eventually
this led to a string of successes (Veneras 9-16+Vega 1-2).
For Mars, things were different. There, the string of missions
was cut short at 1973, presumably before the technology had a chance
to mature.
Then, in 1989, when Phobos 1&2 were launched, the USSR was
already cracking at the seams (although the rest of the world did
not know about it). Apart from that, the Mars "learning curve" was
essentially starting from scratch.
Since then, Russia has been trying to pick up where it left off
(Mars 96, P-G) but I suspect the solution is accept that past glories are
past and start again from scratch (or not far from it) with a modest but scientifically valuable mission.
Tolis.
Good analysis. I suspect a problem is that a simpler mission wouldn't enough of a "spectacular", and that is why this first mission in 15 years, coming after a previous 15-year-ish gap, was so ambitious. Logic would suggest restarting more simply, but life, people and politics have their own logics.
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#671
by
alk3997
on 28 Nov, 2011 16:00
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getting back in topic, according to the French newspaper "Le Monde", if contacts are re-established with F-G, it could be put in a high parking orbit between the Earth and the Moon, where it would wait for the 2013 window to open while engineers complete debugging its software.
http://www.lemonde.fr/planete/article/2011/11/26/espoir-pour-la-sonde-russe-phobos-grunt_1609001_3244.html (in French, evidemment...)
this is the most sensitive proposal so far (and I discussed here first a few days ago
I imagine F-G could be sent to fly by the moon like that old comm sat Asiasat 3 or Nozomi and be perturbed in a distant resonant orbit or even a solar orbit returning to fly by the moon and Earth in late 2013 and resume the original mission as planned. I guess this could be done with the available fuel. The only problem I see (beside the non-trivial need to re-establish full control over the probe) is that Russian hardware is not known for its reliability and 2 more years in space may be too much.
I hope that orbital mechanics gurus like Farquhar and Bellbruno will be working on this
does this mean that the current problem is found to be due to buggy software, or is the reference to a potential new s/w upload for a modified mission?
I'll be the first to say software is usually left for last and then everyone is suprised when there are software failures.
However...We have very little information to say this is *the* problem. Instead I'd translate this to mean the engineers before launch knew that they would still be testing software on the way to Mars (not unusual for unmanned spacecraft) and could then uplink the now-validated software on the way to Mars.
However, I don't take any of that article to mean that the cause of PG non-communicating in low Earth orbit was a software problem. It might have been, it might not be - the data isn't available at least to us and possibly the flight team.
This article falls under the "jumping the gun" category considering no one can reliably talk with the spacecraft yet, let alone have it do anything.
Andy
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#672
by
Chris Bergin
on 28 Nov, 2011 16:10
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A bunch of ESA tweets all sent at the same time:
esaoperations ESA Operations
ESA teams to get confirmation tomorrow from #phobosgrunt controllers if orbit-raising commands successful #perth #estrack
26 minutes ago Favorite Retweet Reply
esaoperations ESA Operations
Tonight, #perth station to forward Russian commands to boost #phobosgrunt higher - to provide better visibility for ground stations
26 minutes ago
esaoperations ESA Operations
Five possible communication slots tonight #perth-#phobosgrunt running from 18:21-03:47GMT. 4 will be used #estrack
26 minutes ago
esaoperations ESA Operations
In collab w/Russian mission control, #ESA teams at #esoc are planning #phobosgrunt contact tonight via #perth #estrack
27 minutes ago
esaoperations ESA Operations
No #phobosgrunt contact attempts made over the weekend due to #perth station preparations for upcoming launch support to another mission
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#673
by
Lars_J
on 28 Nov, 2011 16:20
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#674
by
alk3997
on 28 Nov, 2011 16:20
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A bunch of ESA tweets all sent at the same time:
esaoperations ESA Operations
ESA teams to get confirmation tomorrow from #phobosgrunt controllers if orbit-raising commands successful #perth #estrack
26 minutes ago Favorite Retweet Reply
esaoperations ESA Operations
Tonight, #perth station to forward Russian commands to boost #phobosgrunt higher - to provide better visibility for ground stations
26 minutes ago
esaoperations ESA Operations
Five possible communication slots tonight #perth-#phobosgrunt running from 18:21-03:47GMT. 4 will be used #estrack
26 minutes ago
esaoperations ESA Operations
In collab w/Russian mission control, #ESA teams at #esoc are planning #phobosgrunt contact tonight via #perth #estrack
27 minutes ago
esaoperations ESA Operations
No #phobosgrunt contact attempts made over the weekend due to #perth station preparations for upcoming launch support to another mission
Well, that's one very brute-force method of checking out the computer system, the propulsion system and the power system all in one shot. It will also indicate if the hydrazine / nitrogen tetroxide tanks are still in good shape. If not...
Should we assume that the ground controllers therefore now know the reason that the first burn to Mars did not take place on launch day?
Andy
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#675
by
scpc
on 28 Nov, 2011 16:23
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#676
by
notsorandom
on 28 Nov, 2011 17:08
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The communications opportunities in Perth today between 18:21-03:47GMT will be during the local night there, correct? Has the theory that FG can only communicate while in sunlight been confirmed or ruled out yet?
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#677
by
scpc
on 28 Nov, 2011 17:16
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Perth is GMT+8 so if the times stated as 18:21-03:47 GMT are correct, this would be 02:21 to 11:47 Perth local time, so it looks like some of these would be during the day.
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#678
by
hop
on 28 Nov, 2011 17:50
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Well, that's one very brute-force method of checking out the computer system, the propulsion system and the power system all in one shot. It will also indicate if the hydrazine / nitrogen tetroxide tanks are still in good shape. If not...
This does seem like a rather desperate attempt. There's also the question of guidance: one of the suspected causes of the initial failure was the star trackers not working, or a least not getting a fix at the required time. I wonder if they can do a burn on sun sensors and IMU only ?
Still, they don't have a heck of a lot to lose. If it works, they buy a bunch of time, more sunlight, and longer com windows. If the propulsion system is dead, they aren't going anywhere anyway.
One the subject of color, here's some pictures posted on the NK forum:
http://www.novosti-kosmonavtiki.ru/phpBB2/viewtopic.php?t=12418The propulsion module was also covered in foil
http://www.universetoday.com/wp-content/uploads/2011/11/phobos-grunt-preparations.jpgA poster on the seesat-l list suggested that flaring behavior could be used to determine orientation:
http://www.satobs.org/seesat/Nov-2011/0342.html
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#679
by
savuporo
on 28 Nov, 2011 17:55
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We don't really know if the telemetry received told them anything useful yet. Maybe it did.
