SpaceX Falcon 9 FT - ORBCOMM-2 - Dec. 21, 2015 (Return To Flight) DISCUSSION

[Herb Schaltegger]

Not sure I understand the question....the stages are on handling fixtures prior to S1/2 mate, then the vehicle goes onto the TE. I'm saying that the SLC-40 TE is being used for the F9-21 S1. I don't know where F9-22 is in its processing flow, but I'm guessing the SLC-40 TE was empty prior to the delivery of F9-21 S1.

Okay that's the part I was missing. I read the post about the stage being raised via crane and didn't realize the T/E was out at the pad at all.

[Kim Keller]

Not sure I understand the question....the stages are on handling fixtures prior to S1/2 mate, then the vehicle goes onto the TE. I'm saying that the SLC-40 TE is being used for the F9-21 S1. I don't know where F9-22 is in its processing flow, but I'm guessing the SLC-40 TE was empty prior to the delivery of F9-21 S1.

Okay that's the part I was missing. I read the post about the stage being raised via crane and didn't realize the T/E was out at the pad at all.

There's no TE support for the S1 at its upper end, and so there's no way to raise the stage using the TE. Therefore, they'd need a crane to set the stage down on the holddown structure.

[abaddon]

I've got it - they will use the SES-9 S2 for the static fire attempt of the Orbcomm2 returned booster.  S2 doesn't really do much other than get fueled up and sit there so this would be a minor risk.

Yeah, probably not, but it's more plausible than SES-9 launching on the Orbcomm2 booster .

If they were going to use F9-22's S2 it would already be mated. Using this S1 for SES-9 is not going to happen - there's too much risk at this point in SX's reusability project.

Right, I am in agreement that SES-9 using this core was not going to happen, was making a joke/acknowledgement that my suggestion was only slightly more plausible.  Didn't think it through that the S2 would already be on (and it would probably use the TEL fully instead of the crane and lowered TEL as it seems to be doing) so yeah...

Man, always fun when SpaceX throws us a curveball, although as usual the wilder speculations will end up being just that.

[Herb Schaltegger]

Not sure I understand the question....the stages are on handling fixtures prior to S1/2 mate, then the vehicle goes onto the TE. I'm saying that the SLC-40 TE is being used for the F9-21 S1. I don't know where F9-22 is in its processing flow, but I'm guessing the SLC-40 TE was empty prior to the delivery of F9-21 S1.

Okay that's the part I was missing. I read the post about the stage being raised via crane and didn't realize the T/E was out at the pad at all.

There's no TE support for the S1 at its upper end, and so there's no way to raise the stage using the TE. Therefore, they'd need a crane to set the stage down on the holddown structure.

Ah, of course. Thanks for explaining that in more detail. Thanks, Kim.

[Lars-J]

S1 from F9-21 is now vertical on SLC-40. It was placed there by a large crane, which is still attached as I write this. Rumor is there will be a static fire attempt Thursday.

Was S1 from F9-21 back inside the HIF or was it taken directly to the pad. 

The use of a crane would seem to indicate the SLC-40 transporter erector is gainfully employed with the SES-9 booster.

The holddowns are part of the TE.

I thought they could be separated? They've certainly done that at VFB (see image below), and I seem to recall an image of that at SLC-40 too - although I think that was pre-v1.1.

[BrianNH]

Another possible speculation is that they might take one of the engines off of the returned stage and put it on the SES-9 rocket.  That would allow them to get more test data on the reusability of the engines without endangering the SES-9 launch due to Falcon 9's ability to lose an engine and still complete it's mission. 

Seems a bit unlikely, but not as unlikely as reusing the whole stage.

[abaddon]

Another possible speculation is that they might take one of the engines off of the returned stage and put it on the SES-9 rocket.  That would allow them to get more test data on the reusability of the engines without endangering the SES-9 launch due to Falcon 9's ability to lose an engine and still complete it's mission. 

Seems a bit unlikely, but not as unlikely as reusing the whole stage.

SES-9 would be a poor choice of mission, as it is a GTO flight and quite heavy.  An engine lost early in the mission could result in the payload being delivered to a significantly lower orbit than planned, with the satellite forced to burn station-keeping fuel to make up the shortfall.

[BrianNH]

It would also be difficult to see them put a used engine on CRS-8, given what happened on unlucky CRS-7.

[sdsds]

Another possible speculation is that they might take one of the engines off of the returned stage and put it on the SES-9 rocket.

SES-9 would be a poor choice of mission

I'm hoping each of the FH side boosters gets one engine off the returned stage.

[robert_d]

Quote:

given what happened on unlucky CRS-7.

close quote.
Since the CRS-7 issue was not engine related, and the orbcomm engines are demonstrably "lucky" I don't think your comment necessarily follows.

[Flying Beaver]

Another possible speculation is that they might take one of the engines off of the returned stage and put it on the SES-9 rocket.  That would allow them to get more test data on the reusability of the engines without endangering the SES-9 launch due to Falcon 9's ability to lose an engine and still complete it's mission. 

Seems a bit unlikely, but not as unlikely as reusing the whole stage.

SES-9 would be a poor choice of mission, as it is a GTO flight and quite heavy.  An engine lost early in the mission could result in the payload being delivered to a significantly lower orbit than planned, with the satellite forced to burn station-keeping fuel to make up the shortfall.

But whose saying that a engine from OG2 would fail anyways?
SX has proven that a Merlin can fire 20, 30 times over without any problems at McGregor.

[guckyfan]

SES-9 would be a poor choice of mission, as it is a GTO flight and quite heavy.  An engine lost early in the mission could result in the payload being delivered to a significantly lower orbit than planned, with the satellite forced to burn station-keeping fuel to make up the shortfall.

There is a huge amount of extra fuel available. That's the fuel reserved for landing.

[JBF]

S1 from F9-21 is now vertical on SLC-40. It was placed there by a large crane, which is still attached as I write this. Rumor is there will be a static fire attempt Thursday.

Was S1 from F9-21 back inside the HIF or was it taken directly to the pad. 

The use of a crane would seem to indicate the SLC-40 transporter erector is gainfully employed with the SES-9 booster.

The holddowns are part of the TE.

I thought they could be separated? They've certainly done that at VFB (see image below), and I seem to recall an image of that at SLC-40 too - although I think that was pre-v1.1.

The TEL at SLC-40 is of the older design were they don't separate.

[abaddon]

SES-9 would be a poor choice of mission, as it is a GTO flight and quite heavy.  An engine lost early in the mission could result in the payload being delivered to a significantly lower orbit than planned, with the satellite forced to burn station-keeping fuel to make up the shortfall.

There is a huge amount of extra fuel available. That's the fuel reserved for landing.

Why not do engine reuse on a lighter mission where you could still land after losing an engine?

Also, it's very unclear to me the trades involved here.  If you lost the engine early, would the (already presumed to be very thin) ASDS landing margin be enough to cover the originally contracted orbit?

I think any characterization of a "huge" landing margin on a >5300kg GTO flight is also a bit of hyperbole.

[MechE31]

S1 from F9-21 is now vertical on SLC-40. It was placed there by a large crane, which is still attached as I write this. Rumor is there will be a static fire attempt Thursday.

Was S1 from F9-21 back inside the HIF or was it taken directly to the pad. 

The use of a crane would seem to indicate the SLC-40 transporter erector is gainfully employed with the SES-9 booster.

The holddowns are part of the TE.

I thought they could be separated? They've certainly done that at VFB (see image below), and I seem to recall an image of that at SLC-40 too - although I think that was pre-v1.1.

The TEL at SLC-40 is of the older design were they don't separate.

The SLC-40 TEL is newer than the VAFB one. It was redone completely for V1.1 and was completed after the launch from VAFB. I don't think either are designed to be routinely separated, even if they could be for maintenance.

Note that just because they don't separate, doesn't mean you couldn't leave the strongback horizontal while the launch mount holds a rocket vertically.

[rcoppola]

I, like many, thought perhaps LC-39A wasn't ready, or they found something wrong with the stage and needed the SLC-40 HIF, among other theories...but...

IIRC...there were some last minute tweaks to the Ignition Timing Sequences or the tank pressure relief valve closures or something like that because of the new densification process during the ORB-2 launch at SLC-40.

[mme]

I, like many, thought perhaps LC-39A wasn't ready, or they found something wrong with the stage and needed the SLC-40 HIF, among other theories...but...

IIRC...there were some last minute tweaks to the Ignition Timing Sequences or the tank pressure relief valve closures or something like that because of the new densification process during the ORB-2 launch at SLC-40.

On the flip side, this gives them a booster to run through multiple wet rehearsals at SLC-40.  Maybe they decided to fine tune tanking and "launch" procedures at SLC-40 to improve the odds of meeting an aggressive launch cadence.

[mr. mark]

James Dean Florida Today.. https://twitter.com/flatoday_jdean/status/687284449151709184

[rcoppola]

I, like many, thought perhaps LC-39A wasn't ready, or they found something wrong with the stage and needed the SLC-40 HIF, among other theories...but...

IIRC...there were some last minute tweaks to the Ignition Timing Sequences or the tank pressure relief valve closures or something like that because of the new densification process during the ORB-2 launch at SLC-40.

On the flip side, this gives them a booster to run through multiple wet rehearsals at SLC-40.  Maybe they decided to fine tune tanking and "launch" procedures at SLC-40 to improve the odds of meeting an aggressive launch cadence.

Exactly.

[MrHollifield]

In addition to giving a chance to prove out changes to countdown procedures at LC40, it also proves the vehicle works so when they get it back to LC39A they'll know they have a good vehicle and won't be chasing vehicle problems while trying to make sure the pad is ready.