Wouldn't you want ground confirmation of deployment so as to prevent accidentally deorbiting undeployed but otherwise potentially recoverable sats?
Quote from: mme on 01/17/2017 10:22 pmThe boostback burn on this mission just decelerates the stage before reentry. They still call it "boostback." It's on the timeline at the bottom of the technical webcast and you can see it at about T+4:23 (24:02 into the webcast).More than decelerating the stage before reentry, it reduced the distance downrange for the landing. Without it, the rocket would have landed much further out. It was a partial boostback. A full boostback would have taken it all the way back to Vandenberg AFB, but they didn't grant permission for that to happen, and they may not have had enough fuel budget for that on this flight anyway.
The boostback burn on this mission just decelerates the stage before reentry. They still call it "boostback." It's on the timeline at the bottom of the technical webcast and you can see it at about T+4:23 (24:02 into the webcast).
...Hmm.. If you're not trying to shorten the downrange landing point, then the way to reduce the entry speed (right after stage separation) is to actually burn "engines up".... Did they do that?Ah, ok - a partial boostback makes more sense.
Quote from: rockets4life97 on 01/17/2017 09:11 pmQuote from: yokem55 on 01/17/2017 08:53 pmI wonder if the loss of tracking during the satellite deployment meant they lost their window for for the deorbit burn. Ie, the d/o burn was to happen x minutes after the last separation, but they didn't regain tracking until x+n minutes when they could confirm deployment, and a d/o burn would have them coming down outside the planned hazard area. So, at that point all they can do is passivate the stage and wait 20 years.I'm pretty sure the stage computer control the burns. There isn't a need to wait for commands from the ground, so loss of signal wouldn't matter.Wouldn't you want ground confirmation of deployment so as to prevent accidentally deorbiting undeployed but otherwise potentially recoverable sats?
Quote from: yokem55 on 01/17/2017 08:53 pmI wonder if the loss of tracking during the satellite deployment meant they lost their window for for the deorbit burn. Ie, the d/o burn was to happen x minutes after the last separation, but they didn't regain tracking until x+n minutes when they could confirm deployment, and a d/o burn would have them coming down outside the planned hazard area. So, at that point all they can do is passivate the stage and wait 20 years.I'm pretty sure the stage computer control the burns. There isn't a need to wait for commands from the ground, so loss of signal wouldn't matter.
I wonder if the loss of tracking during the satellite deployment meant they lost their window for for the deorbit burn. Ie, the d/o burn was to happen x minutes after the last separation, but they didn't regain tracking until x+n minutes when they could confirm deployment, and a d/o burn would have them coming down outside the planned hazard area. So, at that point all they can do is passivate the stage and wait 20 years.
Quote from: jcm on 01/17/2017 08:10 pmThe Jason-3 mission is an example where stage 2 was deorbited on a 3rd burn. Also F9-021/OrbcommGood find on Jason-3 -- that one looks like it would have to have 3 burns. F9-021/Orbcomm was launched into its orbit directly on the first burn of the second stage. There should have been no reason to fire that second stage up another two times. Do you have some data on the orbcomm launch that would indicate two more S2 burns?
The Jason-3 mission is an example where stage 2 was deorbited on a 3rd burn. Also F9-021/Orbcomm
Quote from: old_sellsword on 01/17/2017 07:36 pmQuote from: Danderman on 01/17/2017 07:29 pmand the 2nd stage is only good for one re-start,That's a big assumption, and doesn't fit with what Gwynne said pre-launch (three S2 burns).A single re-start is what has been demonstrated, AFAIK. I suppose there was never an announcement by SpaceX of the de-orbit of the 2nd stage.
Quote from: Danderman on 01/17/2017 07:29 pmand the 2nd stage is only good for one re-start,That's a big assumption, and doesn't fit with what Gwynne said pre-launch (three S2 burns).
and the 2nd stage is only good for one re-start,
Quote from: Danderman on 01/17/2017 07:38 pmQuote from: old_sellsword on 01/17/2017 07:36 pmQuote from: Danderman on 01/17/2017 07:29 pmand the 2nd stage is only good for one re-start,That's a big assumption, and doesn't fit with what Gwynne said pre-launch (three S2 burns).A single re-start is what has been demonstrated, AFAIK. I suppose there was never an announcement by SpaceX of the de-orbit of the 2nd stage.That appears to be the modus operandi of many posters here. If SpaceX didn't announce it, or - better yet - didn;t show live video of it, obviously it cannot have happened. C'mon.
Is there a chance that the reversion to likely "warmer" LOX in the wake of the AMOS 6 incident took away the margin needed for de-orbit?
Quote from: edkyle99 on 01/17/2017 09:17 pmIs there a chance that the reversion to likely "warmer" LOX in the wake of the AMOS 6 incident took away the margin needed for de-orbit?Wait, is that right? I understood the revision to be the addition of a fourth COPV, allowing for warmer helium.
That appears to be the modus operandi of many posters here. If SpaceX didn't announce it, or - better yet - didn;t show live video of it, obviously it cannot have happened. C'mon.
...or simply deorbit burn was done and that stage will be up for days/weeks, not years...
Unlikely given this: http://forum.nasaspaceflight.com/index.php?topic=41751.msg1628106#msg1628106, seems to me the plan is to bring it down in a few hours...
Quote from: dglow on 01/18/2017 03:21 amQuote from: edkyle99 on 01/17/2017 09:17 pmIs there a chance that the reversion to likely "warmer" LOX in the wake of the AMOS 6 incident took away the margin needed for de-orbit?Wait, is that right? I understood the revision to be the addition of a fourth COPV, allowing for warmer helium.The LOX was also loaded earlier and slower, ergo it had more time to warm up in the tanks than it would have in the fast loading sequence. i.e. At launch the LOX was warmer than before. I haven't seen anything about whether or not they have also somewhat raised the loading temp of the subcooled LOX so that they weren't as close to the freezing point.
This topic has been hashed before. I believe the following to be true...- return to the original (slower) loading protocols for subcooled props. Still subcooled, just not the rapid fill they were toying with.
- still has same amount of prop at launch time
- same performance because LOX lost from warming is added during this slower process.)
- real hit is not to performance but from loss of ability to recycle count and try again (if the launch window allows). This is because too much subcooled LOX is required for topping off and so not enough in the GSE for a second try.
Quote from: deruch on 01/18/2017 03:32 amQuote from: dglow on 01/18/2017 03:21 amQuote from: edkyle99 on 01/17/2017 09:17 pmIs there a chance that the reversion to likely "warmer" LOX in the wake of the AMOS 6 incident took away the margin needed for de-orbit?Wait, is that right? I understood the revision to be the addition of a fourth COPV, allowing for warmer helium.The LOX was also loaded earlier and slower, ergo it had more time to warm up in the tanks than it would have in the fast loading sequence. i.e. At launch the LOX was warmer than before. I haven't seen anything about whether or not they have also somewhat raised the loading temp of the subcooled LOX so that they weren't as close to the freezing point.This topic has been hashed before. I believe the following to be true...- still has same amount of prop at launch time, no performance hit there (with the small exception of the weight and displaced LOX caused by 4th COPV.
http://video.cnbc.com/gallery/?video=3000584939 Can't believe I still need to defend @SpaceX. When engines light, they are 96.6%. Expect that to climb further.
So we know the 2nd launch needs to be a minimum of 3 months after the first for insurance reasons. To verify that there are no issues with the SC before you launch more. At the same time waiting is lost revenue for Iridium.
Holy moly!!https://www.flickr.com/photos/spacexPhotos now they've got the reel of film back from the ASDS:
Hey Chris, do you reely think they're still using film...?