Author Topic: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011  (Read 426715 times)

Offline kevin-rf

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #760 on: 11/11/2011 03:30 PM »

Well, they're built by humans, launched, and then you have no way to fix them after they leave the ground.  It's the whole "this system has to work flawlessly the first time with no hope of mechanical repair and only slight hope of programming repair, oh and it was made by humans" thing that hurts.

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Are you suggesting humans should also ride to Mars and make sure everything works ;)
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Offline simonbp

I know someone doing radar studies of Europa with the Goldstone 70-m. So yes, lots of power.
Slightly off-thread, but do you have a reference/URL for that?  I like to keep up with long-range radar capabilites.

Google (Scholar) is your friend: http://scholar.google.com/scholar?hl=en&q=radar+europa+goldstone

Offline Art LeBrun

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #762 on: 11/11/2011 03:39 PM »
Did I read the following:

s/c deployed solar panels prior to separation?
solar panels ie the whole assembly now aligned to the sun?

If so - can a burn on the escape stage now be programmed back to the proper trajectory? s/c controls all escape stage functions?
1958 launch vehicle highlights: Vanguard TV-4 and Atlas 12B

Offline simonbp

If so - can a burn on the escape stage now be programmed back to the proper trajectory? s/c controls all escape stage functions?

The modified Fregat controls such things, and its uplink antenna is blocked by the drop tank...

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Not sure if this is true, but...  ::)

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During ground tests the onboard computer worked for no more than 6 hours before hanging. Last patch was applied at Baikonur. My question is, why had we to launch an inoperable spacecraft?

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Offline agman25

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #765 on: 11/11/2011 03:53 PM »
Why is the antenna positioned at that location?

Offline SiberianTiger

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #766 on: 11/11/2011 03:54 PM »
If so - can a burn on the escape stage now be programmed back to the proper trajectory? s/c controls all escape stage functions?

The modified Fregat controls such things, and its uplink antenna is blocked by the drop tank...

No, actually the cruise module controls such things and its X-band low-gain antenna wasn't supposed to be deployed in the parking orbit (and it wasn't).

Offline SiberianTiger

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #767 on: 11/11/2011 03:55 PM »
But after 60 years of advanced rocket science, how does one get stuck in low earth orbit?

Because rockets are still built by humans.

Problems begin when rockets are built by humans earning $7800 a year.

Offline Art LeBrun

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #768 on: 11/11/2011 04:05 PM »
So after solar panel deployment did the s/c command alignment on the sun? Wouldn't modified Fregat try to counteract a cruise mode command?
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Online Ben the Space Brit

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #769 on: 11/11/2011 04:18 PM »
So after solar panel deployment did the s/c command alignment on the sun? Wouldn't modified Fregat try to counteract a cruise mode command?

I have to say that I'm still puzzled about this.  It was my understanding that spacecraft like this are in passive mode until s/c sep and it is the IAU on the upper stage/EDS in the driving seat.  So, why should PG be doing anything? It should be in a stand-by mode until it detaches from the EDS.

If I'm right, then this is the cause of the problem.  After 'waking up' early, PG tried to go over to cruise mode and align itself appropriately.  Now, IIRC, there is no hardware connection between S/C and EDS guidence computers, so you basically have the S/C and EDS fighting over alignment without any dialogue between them.  One was pushing in one direction and the other pushing back until either the RCS prop is exhausted or (as appears to be the case) the un-programmed contingency caused an unrecoverable crash of both vehicles' guidence systems.
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Offline SiberianTiger

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #770 on: 11/11/2011 04:22 PM »
So after solar panel deployment did the s/c command alignment on the sun? Wouldn't modified Fregat try to counteract a cruise mode command?

From forum discussion, I've got an impression that there's only one command node in this spacecraft to be used until the return module takes off from Phobos, and it is located withing the cruise module. The "modified Fregat" is left brainless, so to speak. But it needs better confirmation than my opinion.

Offline Jim

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #771 on: 11/11/2011 04:24 PM »
I understand there's really no way this would ever happen in today's environment (fiscal, safety, technology, etc), but out of curiosity, what is the delta-v between this probe and ISS? They are, after all, in pretty close to the same inclination and both in LEO (though different altitudes).

It has nothing to do with the "environment".  Orbital mechanics and lack of control prevent it.

Offline Jim

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #772 on: 11/11/2011 04:27 PM »
Now, IIRC, there is no hardware connection between S/C and EDS guidence computers, so you basically have the S/C and EDS fighting over alignment without any dialogue between them.  One was pushing in one direction and the other pushing back until either the RCS prop is exhausted or (as appears to be the case) the un-programmed contingency caused an unrecoverable crash of both vehicles' guidence systems.

There is no separate"EDS".  The spacecraft has its own large propulsion system derived from the Fregat.  The spacecraft guidance system controls the whole stack.

Offline HIPAR

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #773 on: 11/11/2011 04:34 PM »
Not sure if this is true, but...  ::)

Quote
During ground tests the onboard computer worked for no more than 6 hours before hanging. Last patch was applied at Baikonur. My question is, why had we to launch an inoperable spacecraft?



Had to get it off during the launch window or wait until the planets return to proper alignment?

---  CHAS

Offline Blackstar

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #774 on: 11/11/2011 04:40 PM »
But after 60 years of advanced rocket science, how does one get stuck in low earth orbit?

I imagine you do it in a similar manner to the CONTOUR spacecraft, which managed to blow itself apart while trying to leave Earth orbit.

I'd have to go back and look again (although Bob Farquhar's new book does have info on CONTOUR), but I think they suffered from the extremes of "faster, better, cheaper," meaning insufficient ground testing.

When something like this happens--and here I'm specifically referring to Phobos-Grunt--the obvious explanation is poor quality control. Obviously something went wrong that should have gone right, and the answer is why nobody caught that thing. Beyond that was probably also a design flaw that prevented a workaround when something went wrong.

In all accidents there is a chain of mistakes, etc. It's not simply one.

Offline Blackstar

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #775 on: 11/11/2011 04:46 PM »
Reflecting on things, this is going to look even worse if the Mars Curiosity launch gets off to a good start. It's damaging to the image of the Russian scientific community.

I sure hope that the Russians don't think that way. Maybe some of them might hope that an American failure would take attention away from them. But fundamentally, this is not a zero-sum game where one group loses and the other gains. Success helps everybody, and failure hurts everybody.

It is in the Russians' best interest if Curiosity is wildly successful, because they will reap the benefits. They will get access to data. And they will learn about Mars, which will hopefully help them when they design their own next Mars mission.

That's something that I tried to emphasize in my article:

http://www.thespacereview.com/article/1965/1

It was important for NASA that Phobos-Grunt succeed, because we could use the data, and we could benefit from having another potential partner in space science (especially one that could provide hardware for future missions). It's no secret that people within NASA were referring to Phobos-Grunt as "Phobos Sample Return" to emphasize this point.

Maybe some heads do need to roll, so to speak, to get things moving in the right direction again. But, all programs suffer losses. If this is a loss, let's hope that it's a blip on the road to a successful unmanned program.   

I sure hope that heads do not roll. That's not the way to improve the organization. The next time the Russians build a planetary mission, it would help if they actually have some people who learned from their mistakes and are paranoid about not repeating them. This is a learning experience, but only if the students don't get expelled.
« Last Edit: 11/11/2011 04:47 PM by Blackstar »

Offline Robotbeat

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #776 on: 11/11/2011 04:50 PM »
I understand there's really no way this would ever happen in today's environment (fiscal, safety, technology, etc), but out of curiosity, what is the delta-v between this probe and ISS? They are, after all, in pretty close to the same inclination and both in LEO (though different altitudes).

It has nothing to do with the "environment".  Orbital mechanics and lack of control prevent it.
I guess no level of prefacing will stop snide remarks. I understand that going from ISS to Phobos-Grunt is simply not an option at all and wouldn't be attempted (because of lack of control, lack of safety) even if it were somehow possible. But I am interested in how far ISS and Phobos-Grunt are in delta-v terms (i.e. orbital mechanics).
« Last Edit: 11/11/2011 04:53 PM by Robotbeat »
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Offline notsorandom

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #777 on: 11/11/2011 04:52 PM »
I understand there's really no way this would ever happen in today's environment (fiscal, safety, technology, etc), but out of curiosity, what is the delta-v between this probe and ISS? They are, after all, in pretty close to the same inclination and both in LEO (though different altitudes).
The inclinations are very close but there ISS and FG are not in the same orbital plane. The longitude of the ascending node for each is different. Changing that would take quite a bit of delta V. If I remeber right a Soyuz has a bit less then 400m/s total. The ones docked to the ISS have already used some of that during their missions thus far and will need some of it for the reentry burn.

Offline ugordan

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #778 on: 11/11/2011 04:52 PM »
But after 60 years of advanced rocket science, how does one get stuck in low earth orbit?

I imagine you do it in a similar manner to the CONTOUR spacecraft, which managed to blow itself apart while trying to leave Earth orbit.

I'd have to go back and look again (although Bob Farquhar's new book does have info on CONTOUR), but I think they suffered from the extremes of "faster, better, cheaper," meaning insufficient ground testing.

I was under the impression (although I didn't do much serious reading on the topic) that it could have been due to a unique way of building a spacecraft around a solid kick stage, in a sense modifying a propulsion system that used to work at other times but in a different configuration. If true, then the similarity between CONTOUR and Phobos-Grunt and its modified Fregat stage is obvious. FBC indeed, lack of better testing and analysis.

Offline ugordan

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Re: LIVE: Zenit-2SB launch with Phobos-Grunt - November 8, 2011
« Reply #779 on: 11/11/2011 04:54 PM »
I understand there's really no way this would ever happen in today's environment (fiscal, safety, technology, etc), but out of curiosity, what is the delta-v between this probe and ISS? They are, after all, in pretty close to the same inclination and both in LEO (though different altitudes).

It has nothing to do with the "environment".  Orbital mechanics and lack of control prevent it.
I understand that it is simply not an option at all. But I am interested in how far ISS and Phobos-Grunt are in delta-v terms (i.e. orbital mechanics).

Calculate it yourself, since the inclination and orbital velocity can be assumed to be the same in a rough approximation, with a little trigonometry the velocity vector difference should be available from the ascending node angle difference alone.

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