Back to the mission itself. I've been mulling it over and just cannot imagine any energetic event at payload insertion that would result in an accidental asymmetric force on the Progress sufficient to induce such a fast tumble rate -- except a LONG thruster burn. That would itself take up lots of propellant, even more if other thrusters were commanded on to attempt to counteract it. What are the alternative sources of sufficient rotational force on the Progress?
Quote from: JimO on 04/29/2015 10:05 pmBack to the mission itself. I've been mulling it over and just cannot imagine any energetic event at payload insertion that would result in an accidental asymmetric force on the Progress sufficient to induce such a fast tumble rate -- except a LONG thruster burn. That would itself take up lots of propellant, even more if other thrusters were commanded on to attempt to counteract it. What are the alternative sources of sufficient rotational force on the Progress?One possibility is a rupture of a prop tank on Progress, either because of something internal or because of strain from a hit from the upper stage after separation.Another possibility is that Progress separated, moved some distance away, then was hit by the upper stage after it had moved off the axis of the stage but before it was entirely clear of its path.
The ISS ground track graphic shows the Progress about to lap the ISS. I didn't hear any mention on the feed of the crew trying to catch a glimpse but their sleep period is about to begin. http://www.ustream.tv/channel/live-iss-stream
What about the possibility that perhaps Progress didn't separate from the third stage at all initially, and the third stage then did it's standard post-launch prop purge/spin maneuver with the Progress still attached, following which Progress separated due to G forces and subsequently exhausted all it's propellant trying to null out the spin rate.In other words, the whole issue is a stage sep failure. Plausible?
Quote from: ChrisWilson68 on 04/29/2015 10:09 pmQuote from: JimO on 04/29/2015 10:05 pmBack to the mission itself. I've been mulling it over and just cannot imagine any energetic event at payload insertion that would result in an accidental asymmetric force on the Progress sufficient to induce such a fast tumble rate -- except a LONG thruster burn. That would itself take up lots of propellant, even more if other thrusters were commanded on to attempt to counteract it. What are the alternative sources of sufficient rotational force on the Progress?One possibility is a rupture of a prop tank on Progress, either because of something internal or because of strain from a hit from the upper stage after separation.Another possibility is that Progress separated, moved some distance away, then was hit by the upper stage after it had moved off the axis of the stage but before it was entirely clear of its path.I've run some numbers on both these scenarios and fail to come within orders of magnitude of the energy transfer required to put the Progress into a 20 rpm tumble. Spewing propellant doesn't have the thrust, and physical impact -- especially at the back end less than 2 meters off centerline -- requires impactor velocity and mass so large that there's no energy short of booster engine firing from a range of 10s of meters to impart the needed impulse [and if it were still firing the Progress would never have gotten that far away]. I can't create a scenario that an impact results in the observable final conditions.Except by thruster.
I've run some numbers on both these scenarios and fail to come within orders of magnitude of the energy transfer required to put the Progress into a 20 rpm tumble. Spewing propellant doesn't have the thrust
Quote from: JimO on 04/29/2015 10:05 pmBack to the mission itself. I've been mulling it over and just cannot imagine any energetic event at payload insertion that would result in an accidental asymmetric force on the Progress sufficient to induce such a fast tumble rate -- except a LONG thruster burn. That would itself take up lots of propellant, even more if other thrusters were commanded on to attempt to counteract it. What are the alternative sources of sufficient rotational force on the Progress?The Russians said that the Soyuz third stage 'depressurised'.
Quote from: Space Pete on 04/29/2015 10:13 pmWhat about the possibility that perhaps Progress didn't separate from the third stage at all initially, and the third stage then did it's standard post-launch prop purge/spin maneuver with the Progress still attached, following which Progress separated due to G forces and subsequently exhausted all it's propellant trying to null out the spin rate.In other words, the whole issue is a stage sep failure. Plausible?or let's try this wild idea..... the solar panels spread out making contact with the 3rd stage creating a spin.
A stuck thruster cannot be a root cause for Progress failure, or even a symptom of a collision, unless the control system is likewise damaged. Progress is double fault tolerant against a stuck thruster - command the thruster to stop firing, if that fails, blow a pyro valve for the thruster, if that fails, shut down the manifold.The rumor that the third stage lost telemetry just before separation, if true, tells us that there was probably an off-nominal separation, either the third stage kept firing after separation, if only for a second, or the explosive bolts all failed to operate, or the stage itself had a bad day and somehow damaged the Progress.
Obviously the distance from the ISS to the Progress would be smaller than the distance from Progress to the ground, but wouldn't it be better to try to take pictures from the ground? I mean with telescopes, etc. Surely there is better imaging equipment available on the ground.