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kevin-rf
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« Reply #570 on: 11/10/2011 11:33 AM » |
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I wonder, do we need two threads?
One for facts and news.
The other for speculation, discussion, ect.
The reason I am asking this is people like Jim O, Liss, ect are providing excellent updates on what is going on, but at the same time there are questions and thoughts that might be better handled in a different thread.
For instance. I keep wondering in the back of my mind the following.
There are really two types of propellant tanks on this mission. Those that are used at Mars and those that are used for Earth departure. One would assume that the Mars tanks are built to prevent freezing using heaters, insulation, ect. Since the tanks used for leaving earth are used and discarded in the first few hours of flight they have no need for that extra insulation, heaters, and thermal control. So how long in LEO until they start having problems with fuel freezing preventing earth departure?
Second, Jim keeps comparing this to USA 193. Is it really the same, the propellant tank was buried inside of USA 193 providing protect against reentry. Phobos-Grunt's tanks are not buried in such a manner. Will the exposed tanks really behave in a similar manner on reentry? I suspect with the exposed tanks they will breach early and burn? But that is pure speculation, and I am not trying to take a swipe at Jim O here.
And now with that rambling I will report myself to Chris...
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Galactic Penguin SST
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« Reply #571 on: 11/10/2011 11:45 AM » |
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The newest theory conveyed by a poster at NK is that the spacecraft rebooted on the second orbit and cannot communicate with the ground stations because the spacecraft was reset to the mode before launch (a bit similar to the sudden loss of contact with Spirit on Mars back in 2004). Right now P-G is within the view of ESA's ground station at Kourou, so fingers crossed...
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Blackstar
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« Reply #573 on: 11/10/2011 01:53 PM » |
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William Graham
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« Reply #574 on: 11/10/2011 01:58 PM » |
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By now someone on the NK forum already claimed that they will shoot the darned thing down next Monday if the mission ultimately cannot be saved.... 
Highly unlikely. Russia has no ASAT capacity. Nor do they have ABMs that can be modified to act as ASATs, like the SM-3 could.
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Vladi
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« Reply #575 on: 11/10/2011 02:03 PM » |
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Аппарат молчит, телеметрию за время ночных сеансов связи не получили. Причины проблем по прежнему не известны. Во время следующих сеансов связи будет произведена попытка послать команду и перезагрузить аппарат. That is from http://phobos.cosmos.ru/index.php?id=388&view=single_thread&cat_uid=1&conf_uid=1&thread_uid=21&page=14Written by a guy who obviously is involved in the program and was the first to announce something was wrong. Basically the message says that there has been no contact with the spacecraft yesterday at all, it is not sending any telemetry. The reason for that is completely unknown, they will try to send a message for rebooting the spacecraft. The same guy said before that in the very beginning that just after reaching orbit they had contact with the craft, it was having control of attitude and its solar arrays were open. Something happened when the craft started the first burn.
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Skylab
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« Reply #576 on: 11/10/2011 02:33 PM » |
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Jim
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« Reply #577 on: 11/10/2011 03:10 PM » |
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.... according to the Space Review (http://thespacereview.com/article/1966/1) Phobos-Grunt "is the heaviest solar system explorer ever (more than twice the second-heaviest, Cassini).", not just the heaviest built in the former USSR.
I don't accept that claim, since the probe's mass is presented in LEO parking orbit, prior to insertion on the trans-Mars route. More than half of that mass disappears by the time it's on interplanetary cruise.
I agree. If one were to compare inserted LEO mass, the Magellan deployment from the shuttle was heavier (18 metric-ton) . The 13.5-metric-ton Phobos-Grunt spacecraft includes the propellant used for TMI and a tank that is jettisoned between burns. It also propellant for MOI. This is no different than the IUS for TVI and STAR-48 motor for VOI on Magellan. So a true measure of the size/mass of spacecraft would be its mass after leaving LEO Sorry to rehash this
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JimO
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« Reply #578 on: 11/10/2011 03:18 PM » |
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... Something happened when the craft started the first burn.
excellent input, thank you. As to what "happened" at burn-1 ignition time, are we satisfied that Brazil observers saw NOTHING -- no flash, no indication of ANY plume -- so it's safe to conclude the failure was on the commanding side, not the engine side?
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JimO
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« Reply #579 on: 11/10/2011 03:20 PM » |
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...Sorry to rehash this No 'rehash', I'm still not satisfied with specific numbers on the propellant load -- since I'm anticipating it all coming down on our heads, now. Sadly.
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simonbp
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« Reply #580 on: 11/10/2011 03:21 PM » |
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Something happened when the craft started the first burn.
Ouch! Shades of Akatsuki, but possibly no second chance...
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Galactic Penguin SST
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« Reply #581 on: 11/10/2011 03:22 PM » |
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Hmm... what does this post mean? Something about the communication antennas got stuck in a position obstructing the line of sight with Earth by the external fuel tank? That doesn't sound like a benign chicken-and-egg problem...
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ugordan
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« Reply #582 on: 11/10/2011 03:24 PM » |
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The way things are developing, did anyone who managed to see it passing overhead notice any sudden flare-ups in brightness that would suggest tumbling, etc?
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Nicolas PILLET
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« Reply #583 on: 11/10/2011 03:26 PM » |
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Brazil observers saw NOTHING -- no flash, no indication of ANY plume -- so it's safe to conclude the failure was on the commanding side, not the engine side? I think we don't have enough information to draft such a conclusion. The fact that there was no plume doesn't mean that the engine is not the source of the problem. The absence of plume could mean, for example, that there is an issue with a propellant valve... (this is pure speculation)
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rcoppola
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« Reply #584 on: 11/10/2011 03:32 PM » |
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Personally, the mass of robotic explorer craft mean little to me until they attempt an actual surface landing in a gravity well environment. And even then I am mainly interested on the final mass that actually makes it onto the surface. That's the real scale of achievement with regards to a spacecraft's mass, IMO. (Pardon the off-topic here)
If the worst does happen and it can't be salvaged, which is heartbreaking for those who have spent so many years designing and building it, could we, if asked, shoot it down for them?
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