Author Topic: SpaceX Falcon 9 - Iridium NEXT Flight 1 DISCUSSION (Jan. 14 2017)  (Read 285871 times)

Offline Danderman

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and 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.

Offline rsdavis9

There have been numerous launches where they performed a de-orbit burn. Even after a 2 burn gto launch. Which would make it 3 burns.
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Offline old_sellsword

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I suppose there was never an announcement by SpaceX of the de-orbit of the 2nd stage.

If Elon can speak for SpaceX, then there was.

Offline Robotbeat

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and 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.

...
Heck, even the first stage does 4 burns (3 restarts) nowadays.
« Last Edit: 01/17/2017 07:59 PM by Robotbeat »
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Offline stcks

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There have been numerous launches where they performed a de-orbit burn. Even after a 2 burn gto launch. Which would make it 3 burns.

Source on this? I don't doubt you but I don't remember another launch doing 3 second stage burns.

Offline gongora

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and 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).

Gwynne said that in an interview with CBS (it's in the podcast version, not sure if it was in the video version).  They will also need multiple burns to do the Formosat 5/SHERPA mission, which deploys to a circular orbit and then an elliptical orbit.  (STP-2 will have even more but that second stage will probably have whatever modifications/mission kit they're designing for the longer duration DoD missions.).

Offline rsdavis9

There have been numerous launches where they performed a de-orbit burn. Even after a 2 burn gto launch. Which would make it 3 burns.

Source on this? I don't doubt you but I don't remember another launch doing 3 second stage burns.

I found this out not because of any annoucement but by tracking the orbits of various launches from the orbit TLE sites. Some are not de-orbitted and some are. I am pretty sure SES was left in orbit. Thiacom maybe?
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Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

Offline jcm

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There have been numerous launches where they performed a de-orbit burn. Even after a 2 burn gto launch. Which would make it 3 burns.

Source on this? I don't doubt you but I don't remember another launch doing 3 second stage burns.

I found this out not because of any annoucement but by tracking the orbits of various launches from the orbit TLE sites. Some are not de-orbitted and some are. I am pretty sure SES was left in orbit. Thiacom maybe?


The Jason-3 mission is an example where stage 2 was deorbited on a 3rd burn. Also F9-021/Orbcomm
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Offline rsdavis9

There have been numerous launches where they performed a de-orbit burn. Even after a 2 burn gto launch. Which would make it 3 burns.

Source on this? I don't doubt you but I don't remember another launch doing 3 second stage burns.

I found this out not because of any annoucement but by tracking the orbits of various launches from the orbit TLE sites. Some are not de-orbitted and some are. I am pretty sure SES was left in orbit. Thiacom maybe?


The Jason-3 mission is an example where stage 2 was deorbited on a 3rd burn. Also F9-021/Orbcomm

Thanks. I was about to go to your monthly newsletter to try to find out which ones.
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

Offline stcks

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The Jason-3 mission is an example where stage 2 was deorbited on a 3rd burn. Also F9-021/Orbcomm

Good 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?

Offline yokem55

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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.
« Last Edit: 01/17/2017 08:53 PM by yokem55 »

Offline rockets4life97

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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.

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.

Offline yokem55

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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.

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?

Offline edkyle99

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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?  Assuming, of course, that it is the stage up there.

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Offline Robotbeat

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No because deorbit was planned as far as eel know. Also, if they had been low on margin, they could've done a more aggressive three engined landing burn instead of the safer but thirstier single-engined burn that they actually used.
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Offline manoweb

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Some awesome pics in that, Jarnis. Local media also getting involved, with some good pics (and a good write up):
http://www.dailynews.com/science/20170117/spacex-rocket-docks-at-san-pedro-home-port-after-successful-mission

Chris Bergin, that article mentions a boost-back burn and two more burns to land. I was under the impression this flight did not perform any boost-back.

Offline FutureSpaceTourist

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You can see the boost back burn pretty clearly in the webcast, starts about T+4:30.

Offline mme

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Some awesome pics in that, Jarnis. Local media also getting involved, with some good pics (and a good write up):
http://www.dailynews.com/science/20170117/spacex-rocket-docks-at-san-pedro-home-port-after-successful-mission

Chris Bergin, that article mentions a boost-back burn and two more burns to land. I was under the impression this flight did not perform any boost-back.
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).
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Offline rpapo

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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).
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.
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Online meekGee

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Some awesome pics in that, Jarnis. Local media also getting involved, with some good pics (and a good write up):
http://www.dailynews.com/science/20170117/spacex-rocket-docks-at-san-pedro-home-port-after-successful-mission

Chris Bergin, that article mentions a boost-back burn and two more burns to land. I was under the impression this flight did not perform any boost-back.
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. 
« Last Edit: 01/17/2017 10:27 PM by meekGee »
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