Quote from: CosmicDebris on 04/28/2015 09:49 pmIf enough is known about the orbital data, perhaps someone with more knowledge than myself could run the numbers through an orbital prediction program, to find out the times and locations that the spacecraft would be visible. I would love to see it fly over after sunset or before sunrise, before it takes a swan dive into oblivion. Cameras at the ready! CosmicDebris.It is visible from latitudes around 10 deg North in the evening and 30 deg South in the morning.
If enough is known about the orbital data, perhaps someone with more knowledge than myself could run the numbers through an orbital prediction program, to find out the times and locations that the spacecraft would be visible. I would love to see it fly over after sunset or before sunrise, before it takes a swan dive into oblivion. Cameras at the ready! CosmicDebris.
The folks over at www.satobs.org are already predicting initiation of orbital decay sometime tomorrow
Quote from: ChrisWilson68 on 04/28/2015 11:54 pmQuote from: DaveS on 04/28/2015 11:07 pmQuote from: StarGeezer on 04/28/2015 10:58 pmI haven't seen anything so far indicating how the craft is 'spinning'. From my geometry days we have x axis (front to back) y axis (left right) and z axis(up down). From edkyle's gif it appears rotating around z axis. How hard is it to correct rotation in one, two or all three axes?Well, you should not read too much into Ed's gif as it's a very simple 2D animation. Based on the video downlinked, it is in a multi-axis spin, so it would require a 3D visualization.Unless different forces are acting on different parts of an object, it always rotates around a single axis. The question is just where that axis is. It might not be close to the x, y, or z axes of the spacecraft.Not true; in torque-free rigid body motion, the angular velocity vector is not stationary in the body (vehicle) axes.
Quote from: DaveS on 04/28/2015 11:07 pmQuote from: StarGeezer on 04/28/2015 10:58 pmI haven't seen anything so far indicating how the craft is 'spinning'. From my geometry days we have x axis (front to back) y axis (left right) and z axis(up down). From edkyle's gif it appears rotating around z axis. How hard is it to correct rotation in one, two or all three axes?Well, you should not read too much into Ed's gif as it's a very simple 2D animation. Based on the video downlinked, it is in a multi-axis spin, so it would require a 3D visualization.Unless different forces are acting on different parts of an object, it always rotates around a single axis. The question is just where that axis is. It might not be close to the x, y, or z axes of the spacecraft.
Quote from: StarGeezer on 04/28/2015 10:58 pmI haven't seen anything so far indicating how the craft is 'spinning'. From my geometry days we have x axis (front to back) y axis (left right) and z axis(up down). From edkyle's gif it appears rotating around z axis. How hard is it to correct rotation in one, two or all three axes?Well, you should not read too much into Ed's gif as it's a very simple 2D animation. Based on the video downlinked, it is in a multi-axis spin, so it would require a 3D visualization.
I haven't seen anything so far indicating how the craft is 'spinning'. From my geometry days we have x axis (front to back) y axis (left right) and z axis(up down). From edkyle's gif it appears rotating around z axis. How hard is it to correct rotation in one, two or all three axes?
If Russian Ground Control isn't able to establish control of the spacecraft, when is Progress 59 projected to re-enter?
Does the "P" number indicate the amount of propellant remaining?
Can the propellant that is allocated for transfer to the ISS be used for Progress maneuvers?
I'm not familiar with the units for Soyuz/Progress tank capacity.
Quote from: Space Pete on 04/28/2015 03:46 pmQuote from: Chris Bergin on 04/28/2015 03:17 pmThat's clearly not the point that was made. If there's a problem with the next Dragon, then Dragon is stood down. That's the problem....not the vehicle failing to arrive, but the vehicle being stuck on the ground for a lengthy period of time before being able to launch again.Exactly - the crew is fine now, and would be for a good few months even in the event of a Dragon failure, but if Dragon/F9 failed and had to be stood down for a number of months, and Cygnus RTF got delayed (which I suspect it will - since when does anything go to schedule in this business), then that will leave only one HTV to resupply ISS for rest of year. Even with Progress flying, that would make things tight.Essentially, what I'm saying is that ISS is now zero fault tolerant to another resupply craft failure - with ATV gone, Cygnus' failure last year, today's Progress failure, and only one HTV this year, a Dragon failure would essentially cut ISS' regular supply line to Earth. If they couldn't get it back quickly, that would be the issue.A case perhaps for Dream Chaser Cargo...?
Quote from: Chris Bergin on 04/28/2015 03:17 pmThat's clearly not the point that was made. If there's a problem with the next Dragon, then Dragon is stood down. That's the problem....not the vehicle failing to arrive, but the vehicle being stuck on the ground for a lengthy period of time before being able to launch again.Exactly - the crew is fine now, and would be for a good few months even in the event of a Dragon failure, but if Dragon/F9 failed and had to be stood down for a number of months, and Cygnus RTF got delayed (which I suspect it will - since when does anything go to schedule in this business), then that will leave only one HTV to resupply ISS for rest of year. Even with Progress flying, that would make things tight.Essentially, what I'm saying is that ISS is now zero fault tolerant to another resupply craft failure - with ATV gone, Cygnus' failure last year, today's Progress failure, and only one HTV this year, a Dragon failure would essentially cut ISS' regular supply line to Earth. If they couldn't get it back quickly, that would be the issue.
That's clearly not the point that was made. If there's a problem with the next Dragon, then Dragon is stood down. That's the problem....not the vehicle failing to arrive, but the vehicle being stuck on the ground for a lengthy period of time before being able to launch again.
I think this worry is overblown. Lets say Dragon does fail. No big deal, just keep flying Dragon and/or Progress anyway, while the investigation is continuing. You wouldn't want to do that with crew, but they're carrying bulk supplies to ISS, so even before you've found and fixed the root cause of the failure, just keep flying. There will be a higher risk, but that's OK. Both Dragon and Progress have successfully completed a number of missions, so they don't have some fundamental design flaw that makes them very likely to fail. The failures might have been one-off things, or some design flaw that gives a low chance of failure on each flight. No problem. The less likely case is there was some recent change that makes all subsequent flights fail. Keep flying both Dragon and Progress and it's unlikely both will have a string of failures. And if they do, just figure out what changed recently and revert that change. That's much faster than having to be very certain of a root cause, as one would have to do before flying a crew again after a failure.
Let me suggest a bright spot here - in the event that contact is re-established with Progress, and it has not blown through all of its prop, the docking could be accomplished, even if it takes a week for recovery. The vehicle could be commanded to fly higher than the ISS orbit, and then dwell for several weeks in that higher orbit to "catch up" to ISS, This may require using all prop designated for transfer to ISS, but at least the docking with ISS could be accomplished.However, it now appears that the Progress motion control system has failed, so recovery may not be possible.
And if they do, just figure out what changed recently and revert that change.
Quote from: Danderman on 04/29/2015 02:48 amLet me suggest a bright spot here - in the event that contact is re-established with Progress, and it has not blown through all of its prop, the docking could be accomplished, even if it takes a week for recovery. The vehicle could be commanded to fly higher than the ISS orbit, and then dwell for several weeks in that higher orbit to "catch up" to ISS, This may require using all prop designated for transfer to ISS, but at least the docking with ISS could be accomplished.However, it now appears that the Progress motion control system has failed, so recovery may not be possible.If it is recovered, but concerns about the control system remain, it seems to me a rendezvous might be ruled out to ensure a repeat of the Progress M-34 collision with Mir doesn't recur.Quote from: ChrisWilson68 on 04/29/2015 04:21 amAnd if they do, just figure out what changed recently and revert that change. I agree with your conclusion that the likelihood of systematic problems with both Progress and Dragon is remote, but keep in mind that neither of them can support the station long term alone. It's an undesirable position to be in.Furthermore, reverting a change assumes there was an intentional documented change, not a loss of process control or other difficult to identify systematic issue.
TsUP may decide to de-orbit (today?) Progress if they fail to take control of the cargoship.http://www.interfax.ru/russia/439173
Quote from: chewi on 04/29/2015 05:56 amTsUP may decide to de-orbit (today?) Progress if they fail to take control of the cargoship.http://www.interfax.ru/russia/439173How can they de-orbit if they can't get its attitude under control?