-
#1040 by Chris Bergin on 20 Dec, 2011 13:55
-
I just want to clear things up. In The Independent of the UK over the weekend, it was claimed that there were over 10 kilogrammes of some radioactive cobalt isotope aboard PG. That doesn't sound right to me; have they got kilogrammes and grammes mixed up here?
Great to see the comment section attemting to correct him (as it should be, even here if I wrote nonsense). -
#1041 by Proponent on 20 Dec, 2011 14:00
-
I just want to clear things up. In The Independent of the UK over the weekend, it was claimed that there were over 10 kilogrammes of some radioactive cobalt isotope aboard PG. That doesn't sound right to me; have they got kilogrammes and grammes mixed up here?
I recall an article in the Independent several years ago about alternative energy which quoted power consumption in "terra watts." Apparently a reporter had heard the term "terawatt" but had little idea what it meant. -
#1042 by Lee Jay on 20 Dec, 2011 14:04
-
I just want to clear things up. In The Independent of the UK over the weekend, it was claimed that there were over 10 kilogrammes of some radioactive cobalt isotope aboard PG. That doesn't sound right to me; have they got kilogrammes and grammes mixed up here?
I recall an article in the Independent several years ago about alternative energy which quoted power consumption in "terra watts." Apparently a reporter had heard the term "terawatt" but had little idea what it meant.
I almost always quote national and global energy consumption rates in terawatts. Quads or exajoules per year or - banish the thought - million barrels per day equivalent seem so goofy. -
#1043 by ChileVerde on 20 Dec, 2011 15:06
-
There's an interesting bit of analysis of the variable Fobos-Grunt decay rate on SeeSat-L. If correct, it seems to imply FG is actively maintaining its solar orientation, presumably using the momentum wheel assembly.
http://www.satobs.org/seesat/Dec-2011/0154.html
http://www.satobs.org/seesat/Dec-2011/0175.html
http://www.satobs.org/seesat/Dec-2011/0180.html
https://twitpic.com/7vut8o/full -
#1044 by A_M_Swallow on 20 Dec, 2011 19:37
-
I recall an article in the Independent several years ago about alternative energy which quoted power consumption in "terra watts." Apparently a reporter had heard the term "terawatt" but had little idea what it meant.
Just be glad he did not spell it 'terror watts'.
We will leave that one for electrifying horror films.
-
#1045 by iamlucky13 on 21 Dec, 2011 00:40
-
I just want to clear things up. In The Independent of the UK over the weekend, it was claimed that there were over 10 kilogrammes of some radioactive cobalt isotope aboard PG. That doesn't sound right to me; have they got kilogrammes and grammes mixed up here?
See my post two up from yours. The actual amount is "less than 10 micrograms."
To reference this to some reasonable authority, it is corroborated by a communication from the Russian Space Research to Institute partners on the mission, which include the Planetary Society, as posted on the Planetary Society Website.
http://planetary.org/blog/article/00003298/
The Independent's writer is himself probably just copying what he read from the Associated Press, which is the original source of the mistake as far as I can tell.
Because of the way the modern media works, the same mistake has been repeated by hundreds of outlets syndicating the story to millions of readers.
Fortunately, none of them were clever enough to try figure out what the approximate hazard of 10 kg of Cobalt-57 were. If they'd called up a health physicist to ask, they'd be told 10 kg is a major hazard. -
#1046 by JimO on 21 Dec, 2011 13:33
-
Might be time to shift to another thread entitled 'Fobos-Grunt Reentry Watch'... nothing new re troubleshooting for a week.
-
#1047 by deaville on 21 Dec, 2011 13:46
-
The Daily Telegraph had a short piece about the re-entry dates - forecast between 2nd and 12th January, though the article added that this was not known for certain and might change. Also, it was at pains to point out that London was likely to be on the re-entry trajectory. Should I invest in a hard hat?
-
#1048 by Lee Jay on 21 Dec, 2011 13:59
-
Might be time to shift to another thread entitled 'Fobos-Grunt Reentry Watch'... nothing new re troubleshooting for a week.
The latest I can find is here:
http://satobs.org/seesat/Dec-2011/0182.htmlQuoteUsing those values with predicted space weather, STOAG propagates the orbit to decay on 2012 Jan 13. Estimated uncertainty is +/- 5 days, based on the rule of thumb of 20 percent of the time remaining to decay.
-
#1049 by Chris Bergin on 21 Dec, 2011 14:05
-
Might be time to shift to another thread entitled 'Fobos-Grunt Reentry Watch'... nothing new re troubleshooting for a week.
Concur. I'll set that up later today. -
#1050 by Prober on 21 Dec, 2011 15:53
-
Might be time to shift to another thread entitled 'Fobos-Grunt Reentry Watch'... nothing new re troubleshooting for a week.
maybe before we do with the information available you can tell us how you expect the breakup to look like?
dangers for anyone?
-
#1051 by mdo on 21 Dec, 2011 16:20
-
The worst case scenario is that it blows up before reentry littering LEO with debris. Here is an analysis of such a case. As much as I feel sorry for the project I would consider myself very, very lucky to witness the fiery reentry during a clear winter night.
-
#1052 by rdale on 21 Dec, 2011 16:26
-
mdo - I don't understand. If it "blows up" and results in debris falling back to Earth similar to USA193, wouldn't that be a good thing?
-
#1053 by Comga on 21 Dec, 2011 16:30
-
The worst case scenario is that it blows up before reentry littering LEO with debris. Here is an analysis of such a case. As much as I feel sorry for the project I would consider myself very, very lucky to witness the fiery reentry during a clear winter night.
AFAIK, there is no reason to anticipate an energetic destruction before reentry, which would be necessary to propel debris into higher orbits. Even then, assuming a worst case event with the current low apogee becoming the perigee for debris, their orbital lifetimes would be short. This is not the "worst case".
edit: Are you saying that a "shoot-down" like USA193 would be a bad idea, leading to your "worst case"? -
#1054 by mdo on 21 Dec, 2011 16:40
-
mdo - I don't understand. If it "blows up" and results in debris falling back to Earth similar to USA193, wouldn't that be a good thing?
Some fragments will loose energy and reenter quickly. Some, however, will gain enough energy to cross the paths of ISS and beyond. Making 15 revolutions a day that makes 30 potential crossings, times the numbers of fragments (1000s), times the (increased) lifetime. Compared to the decay of a single object whose relative position to other space assets is well known - no, that is definitely not what I consider a good alternative. -
#1055 by Comga on 21 Dec, 2011 17:00
-
mdo - I don't understand. If it "blows up" and results in debris falling back to Earth similar to USA193, wouldn't that be a good thing?
Some fragments will loose energy and reenter quickly. Some, however, will gain enough energy to cross the paths of ISS and beyond. Making 15 revolutions a day that makes 30 potential crossings, times the numbers of fragments (1000s), times the (increased) lifetime. Compared to the decay of a single object whose relative position to other space assets is well known - no, that is definitely not what I consider a good alternative.
But the USA193 analysis to which you pointed shows most of the debris decaying within 40 days. Even if an impact were to occur, which won't be intentional or statistically likely, the impact of this smalll, temporary pulse on the debris population wouldn't be significant. -
#1056 by mdo on 21 Dec, 2011 17:44
-
AFAIK, there is no reason to anticipate an energetic destruction before reentry, which would be necessary to propel debris into higher orbits. Even then, assuming a worst case event with the current low apogee becoming the perigee for debris, their orbital lifetimes would be short. This is not the "worst case".
Still, if at all, I prefer it to come down in one piece. Maybe the term "worst case" sounds too dramatic. So, I withdraw it and just say "worse".
The often cited argument about the perigee of debris has some truth to it, but the effect is obviously not enough to prevent the risk of cascading events. As of today the new perigee would be up to 270 km instead of currently 200 km. Together with an increased apogee of fragments with a net gain in energy their lifetime can increase significantly. The reference mentions objects reaching up to 2689 km in altitude. And irrespective of how many objects would reenter quickly, there is the additional risk imposed by those remaining.
And yet again, in general and before anybody misreads, I'm not implying that it will or should disintegrate - I just hope it doesn't and therefore will be left alone given the energy stored on board in terms of propellants. -
#1057 by JimO on 21 Dec, 2011 20:19
-
And yet again, in general and before anybody misreads, I'm not implying that it will or should disintegrate - I just hope it doesn't and therefore will be left alone given the energy stored on board in terms of propellants.
I concur with MDO's assessment of the awfulness of this outcome. And everything else he has posted. He sounds like "he's smelled the gunpowder".
But perhaps the energetic level of a chemical explosion scenario is significantly less tham that of a kinetic disintegration -- I'd have to compare max apogee boosts of fragments from past explosions to fragments from recent head-on collisions. Has anyone done that?
My concern for a fuel-mix cascading detonation -- small 'pop' breaks more lines, new leaks create higher-energy reactions -- is based on my concern that the vehicle's propulsion system, and valve settings, is in an unknown immediately-pre-ignition state, quite likely under the control of an insane autopilot. Add in the thermal cycling -- >600 day-night cycles so far for a system designed for 2 cycles -- and presumably non-functional thermal control system, and it significantly enhances the pucker setting on the way I think about what can go wrong with 12 tons of hypergolics.
We have a high-energy-concentration payload in an undetermined [and essentially non-deterministic] state, built by a spacecraft team with a demonstrably lamentable lack of 'graceful degradation' and 'safe fallback' engineering design judgment. If the vehicle was launched 'ready-to-fail', as the best informed Western observers have concluded [Anatoly Zak is THE MAN on this issue, IMHO], it's only a small glitch to convert that to 'ready-to-self-destruct'.
Perhaps the consolation is that however 'likely' such an event is [and 'low' is my intuitive guess], it is LESS likely than a single tank rupture and spill [eg, Salyut-7, 1985] which could be naked-eye visible to ground observers.
I think this underscores the GROWING importance of worldwide amateur observers to get their eyeballs on the vehicle at every opportunity and report back. -
#1058 by Chris Bergin on 21 Dec, 2011 20:37
-
New thread:
http://forum.nasaspaceflight.com/index.php?topic=27593.0
All future posts to go on the new thread. Leaving this unlocked to allow for important quotes to be moved to the new thread. -
#1059 by Galactic Penguin SST on 08 Nov, 2013 22:33
-
Bump for 2nd anniversary of the launch. To me it is still the most shocking Russian failure of 2011 - to have the spacecraft failing so early in the mission....
