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#920
by
Ben the Space Brit
on 05 Dec, 2011 12:13
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@ Kaputnik,
Communications have been attempted under the only circumstances under which the probe responded before but without response or effect. Repeated attempts to command the probe under those same circumstances have had almost no visible effect except (possibly) bits falling off.
Regarding the initial long silence, it's looking that the Russians didn't have an X-band tranceiver with the track speed needed to lock onto FG whilst in LEO, so communications were not initially possible. ESA did have the needed equipment and it wasn't until they got involved the communications were even possible. However, apart from the initial 'bleep' heard from Perth, there has been no response from the probe. Indeed, Roscosmos have never specified what data they received from the probe and I am suspicious that the 'encrypted telemetry' was, in fact, random gibberish squirted out of the dying communications subsystem in response to the 'poke' from Perth.
Overall, I'd say that it's beginning to look that the previous respose ws a fluke, maybe random data left in the communications buffer when the main processor died.
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#921
by
MP
on 05 Dec, 2011 13:15
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I think the confusion come from the earliest launches - the 1960 window. The Soviet lost a load of early probes to reluctant upper stages that never restarted for TMI.
According to what I see, both Mars-1960A and Mars-1960B contained modules that were supposed to reach Mars.
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#922
by
kevin-rf
on 05 Dec, 2011 13:25
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Not adding anything we don't already know on this thread, but brings the news site up to date.
http://www.nasaspaceflight.com/2011/12/hope-lost-fobos-grunt-re-entry-early-new-year/
Notably, no major items of hardware on Fobos-Grunt have been listed as potentially surviving entry,
Umm... even the sample return capsule?
Of course I am sure JimO will argue against the point on the grounds he fears the survival of Al tanks full of frozen nastyness
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#923
by
dchill
on 05 Dec, 2011 13:36
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Umm... even the sample return capsule?
I'm just worried about those cute little water bears that are still up there in the capsule. Maybe we should take bets on if they're going to survive.
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#924
by
JimO
on 05 Dec, 2011 14:11
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Maybe we also should look back at the perigee-creep period
with an attempt to better characterize it, and exploit the tantalizing clue
that whatever it was, it ended abruptly. That's trying to tell us something.
Seeing the altitude drop that did occur versus what we would have expected
to occur naturally [and did so, after the end-date], can we estimate the
total posigrade delta-V imparted to the vehicle? We can then estimate
the minimum propellant that would be expended, if the thrust was all
posigrade.
Then we can look at available propellant, such as MDU attitude control
[60 kg or so, I think I read somewhere? -- need to confirm], and determine
if the burn was efficient [i.e., deliberate] or very wasteful [i.e., accidental].
The waste could be a result of attitude control cross-coupling [most likely],
which from shuttle experience is >90% for even the least-inefficient thrusters,
further degraded by off-posigrade net thrusting [that is, most was wasted on planar or radial thrusting, which cancel out over a full rev].
Might those numbers provide any insight?
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#925
by
Chris Bergin
on 05 Dec, 2011 14:26
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Not adding anything we don't already know on this thread, but brings the news site up to date.
http://www.nasaspaceflight.com/2011/12/hope-lost-fobos-grunt-re-entry-early-new-year/
Again, why "all of its 17 missions to the Red Planet since the 1960s"? It's 19 launches, don't you agree? Which 2 you decided not to count?
I've gone with William's count since the pre-launch article and it's never been corrected since - until your note. I'll inquire.
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#926
by
douglas100
on 05 Dec, 2011 14:27
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I think the confusion come from the earliest launches - the 1960 window. The Soviet lost a load of early probes to reluctant upper stages that never restarted for TMI.
Small nit, but the final stage of the 8K78 was not capable of restart. It was placed in orbit by the R7 lower stages and then made a single burn to place the payload on the final trajectory. Some Mars probes were indeed lost when this stage (Blok L) failed to start in parking orbit.
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#927
by
Prober
on 05 Dec, 2011 15:33
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@JimO
If the drop tank broke off it would be a good thing, right?
Fuel would heat up in sunlight.
Bad part is no control of location.
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#928
by
kevin-rf
on 05 Dec, 2011 16:08
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@JimO
If the drop tank broke off it would be a good thing, right?
Fuel would heat up in sunlight.
Bad part is no control of location.
There has been no indication of that, Ted's estimates based on the brightness and rate of decay indicates something small and not very dense. Like for instance, an insulation blanket.
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#929
by
Stan Black
on 05 Dec, 2011 16:09
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#930
by
William Graham
on 05 Dec, 2011 17:55
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Not adding anything we don't already know on this thread, but brings the news site up to date.
http://www.nasaspaceflight.com/2011/12/hope-lost-fobos-grunt-re-entry-early-new-year/
Again, why "all of its 17 missions to the Red Planet since the 1960s"? It's 19 launches, don't you agree? Which 2 you decided not to count?
I've gone with William's count since the pre-launch article and it's never been corrected since - until your note. I'll inquire.
I don't remember there being a count in the original article.
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#931
by
ckiki lwai
on 05 Dec, 2011 20:13
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I was in Munich this evening and at about 18h05 I saw a very bright light flying over the sky in the South. It was very bright and seemed to consist out of several bright lights in a straight line perpendicular to the flying direction. I checked Heavens above and it turns out Phobos-Grunt flew over Munich at that exact time but its brightness was only predicted to be 3.1 while it was I think it was certainly brighter than -2, it also flew the exact same path as predicted by heavens above.
Have any Europeans seen something similar? Could some stuff have already broken of and burned up?
Or I am just seeing flying saucers
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#932
by
Michael J
on 05 Dec, 2011 20:19
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#933
by
iamlucky13
on 05 Dec, 2011 23:48
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Maybe we also should look back at the perigee-creep period
with an attempt to better characterize it, and exploit the tantalizing clue
that whatever it was, it ended abruptly. That's trying to tell us something.
Seeing the altitude drop that did occur versus what we would have expected
to occur naturally [and did so, after the end-date], can we estimate the
total posigrade delta-V imparted to the vehicle? We can then estimate
the minimum propellant that would be expended, if the thrust was all
posigrade.
That sounds potentially useful, but not being able to work that out myself, my thoughts are led in a different direction.
According to Chile Verde's graph (
link), the last day of perigee increase was 325 or 326 (looks like some spurious data in there - a pair of similar high values followed by a pair of similar low values). I assume these are GMT dates.
That's November 21 or 22.
Telemetry was first received late on November 23 (GMT), if I read back correctly.
I have to wonder if those are related.
For example, could F-G have been stable in an orientation where the LGA was blocked by the fuel tank, run out of attitude control fuel around that time, and drifted briefly into an orientation where communication was possible?
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#934
by
ChileVerde
on 06 Dec, 2011 00:06
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According to Chile Verde's graph (link), the last day of perigee increase was 325 or 326 (looks like some spurious data in there - a pair of similar high values followed by a pair of similar low values). I assume these are GMT dates.
Yes, they're GMT, actually UTC. Pretty much the same thing for present purposes.
I agree that the data spikes then are probably somewhat spurious. Hazarding a guess, I suspect that the algorithms that generate the orbital elements incorporate a propagator that doesn't model the actual behavior of PG at that time and got a bit flummoxed.
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#935
by
kevin-rf
on 06 Dec, 2011 00:14
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Have any Europeans seen something similar? Could some stuff have already broken of and burned up?
Well, there is a similar report on SeeSat:
http://www.satobs.org/seesat/Dec-2011/0062.htmlFor what it is worth, poster's email domain address ends in .it (Italy)
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#936
by
mdo
on 06 Dec, 2011 01:36
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Seeing the altitude drop that did occur versus what we would have expected
to occur naturally [and did so, after the end-date], can we estimate the
total posigrade delta-V imparted to the vehicle? We can then estimate
the minimum propellant that would be expended, if the thrust was all
posigrade.
The perigee was raised by some 6.7 km between Nov. 9 and 21. As per rocket equation and assuming 300 s specific impulse that takes 9 kg of fuel.
Now, sometime after Nov. 21 the perigee started to decline. From Nov. 22 to Dec. 4 (same duration as Nov. 9 to 21) dh equalled ~6.25 km. The sum of the two deltas is about 13 km and it would take 17.5 kg of fuel mass to achieve this with a properly executed maneuver (dv = 3.8 m/s).
Assuming an isp of 200 s gives 26.3 kg (instead of 17.5).
An average off axis thrust vector of 45 deg would add another factor of 1.41 (37.1 kg).
Since I do not have data on the effect of venting let's turn it around and assume that 3000 kg vented from the extra tank that is not designed for long duration flight. If vented along the velocity vector it would require an isp of 1.55 s. At an angle of 45 deg it would be 2,3 s. It is not clear to me whether the latter numbers are realistic, but decide yourself...
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#937
by
Chris Bergin
on 06 Dec, 2011 01:58
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Not adding anything we don't already know on this thread, but brings the news site up to date.
http://www.nasaspaceflight.com/2011/12/hope-lost-fobos-grunt-re-entry-early-new-year/
Again, why "all of its 17 missions to the Red Planet since the 1960s"? It's 19 launches, don't you agree? Which 2 you decided not to count?
I've gone with William's count since the pre-launch article and it's never been corrected since - until your note. I'll inquire.
I don't remember there being a count in the original article.
HA! My bad, that WAS me! I took it from the second article, which I used a lot of William's background, but that was my addition after finding it interesting in Jonathan Amos' report.
I'll correct the number.
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#938
by
mdo
on 06 Dec, 2011 02:18
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Since I do not have data on the effect of venting let's turn it around and assume that 3000 kg vented from the extra tank that is not designed for long duration flight. If vented along the velocity vector it would require an isp of 1.55 s. At an angle of 45 deg it would be 2,3 s. It is not clear to me whether the latter numbers are realistic, but decide yourself...
One more consideration. The perigee (AOP) was moving across the Northern hemisphere since launch. So, due to the seasonal effect of the ecliptic the probe spent more time in the sunlit part of the orbit (Southern hemisphere) while close to the apogee. So, if the venting occurred in pulses during the sunlit part of the orbit then it could have had a net effect on the perigee whereas the apogee was less perturbed.
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#939
by
jcm
on 06 Dec, 2011 16:29
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Not adding anything we don't already know on this thread, but brings the news site up to date.
http://www.nasaspaceflight.com/2011/12/hope-lost-fobos-grunt-re-entry-early-new-year/
Again, why "all of its 17 missions to the Red Planet since the 1960s"? It's 19 launches, don't you agree? Which 2 you decided not to count?
I've gone with William's count since the pre-launch article and it's never been corrected since - until your note. I'll inquire.
I don't remember there being a count in the original article.
HA! My bad, that WAS me! I took it from the second article, which I used a lot of William's background, but that was my addition after finding it interesting in Jonathan Amos' report.
I'll correct the number.
I think I missed some earlier discussion here.. why do you consider them all failures?. I consider Mars-5 to be a success, and the Mars-2 and Mars-3 missions to be partial successes (the orbiters kind of worked, and the Mars-3 lander at least made it to the surface) - even Mars-6 returned atmospheric data on the way down.
I think if these had been NASA probes the US would have claimed at least some of these as successes. Sure, not all mission objectives were achieved, but I think to say the Russians had ZERO success at Mars is a (mild) overstatement.
I agree that the total count is 19 - and I also make it 19 for the US (counting the Dawn gravity assist but not MSL since we can't rate it's succ/fail yet, and not counting DS2 as a separate mission) and 3 for 'other' (Nozomi, Rosetta, Mars Ex)
