SpaceX Falcon 9 : Koreasat 5A : Oct. 30, 2017 : DISCUSSION THREAD

[woods170]

I'm wondering if they're deliberately trying higher and higher energy descents and landings in an attempt to find out just how far they can push these cores before they can't be recovered. Given that they're getting quite a stockpile of used cores now, they can afford to waste them on empirical data-gathering exercises like this by deliberately exposing them to stresses that may make them unreusable.

My thought as well, see above

was this a planned "push the envelope" reentry? If so, that the stage is worse for wear and tear isn't necessarily bad.

It is in fact exactly what SpaceX has been doing on recent launches. There are multiple reasons for this but gaining flight-knowledge on "sideways" reentry of a rocket body is the main driver. The keywords here are BFR and BFS.
SpaceX can actually afford to lose a booster stage during those reentry experiments. The current booster stages are Block 4 and will be phased-out in favor of Block 5 in the near future. And there is the fact that SpaceX now has so many recovered booster stages in storage that they have even begun scrapping some of them for lack of available re-flight opportunities.

[ugordan]

There are multiple reasons for this but gaining flight-knowledge on "sideways" reentry of a rocket body is the main driver.

If that's the case, wouldn't it make more sense to utilize titanium grid fins instead since they have greater control authority and would allow for even higher angles of attack?

[JamesH65]

There are multiple reasons for this but gaining flight-knowledge on "sideways" reentry of a rocket body is the main driver.

If that's the case, wouldn't it make more sense to utilize titanium grid fins instead since they have greater control authority and would allow for even higher angles of attack?

I reckon those Ti fins are VERY expensive, so they might not want to risk losing them if they don't need to.

[ugordan]

There are multiple reasons for this but gaining flight-knowledge on "sideways" reentry of a rocket body is the main driver.

If that's the case, wouldn't it make more sense to utilize titanium grid fins instead since they have greater control authority and would allow for even higher angles of attack?

I reckon those Ti fins are VERY expensive, so they might not want to risk losing them if they don't need to.

Perhaps, but so are the stages themselves and they are apparently willing to risk losing them.

[FutureSpaceTourist]

Payload is about 3700kg.

What is the source of this number?  Thales own press release presented earlier in this thread says 3,500 kg.

SpaceX launch webcast today. At about the T-6:00 mark.

Just to prove the announcer didn’t misspeak, Thales’ post launch press release also says 3,700 kg:
https://www.thalesgroup.com/en/worldwide/space/press-release/another-thales-alenia-space-built-satellite-now-orbit#

[saliva_sweet]

Payload is about 3700kg.

What is the source of this number?  Thales own press release presented earlier in this thread says 3,500 kg.

SpaceX launch webcast today. At about the T-6:00 mark.

Just to prove the announcer didn’t misspeak, Thales’ post launch press release also says 3,700 kg:
https://www.thalesgroup.com/en/worldwide/space/press-release/another-thales-alenia-space-built-satellite-now-orbit#

This is great. I was so annoyed at having two conflicting official numbers.

[aameise9]

Does anyone know what happens to second stage?  Can it be deorbited?

(Apologies if I missed previous discussion of this issue.)

[Steven Pietrobon]

The second stage is in a super geosynchronous transfer orbit (SGTO). Perturbations by the Moon will soon decrease the stage's perigee and send it back into Earth's atmosphere where it will burn up.

[OneSpeed]

There are multiple reasons for this but gaining flight-knowledge on "sideways" reentry of a rocket body is the main driver.

If that's the case, wouldn't it make more sense to utilize titanium grid fins instead since they have greater control authority and would allow for even higher angles of attack?

The Ti fins do have greater control authority, but the 'bear trap' leading edge actually reduces drag. Perhaps SpaceX have been re-thinking that aspect of the design?

[Rocket Science]

Interesting to read the comments from observations of Falcon post landing aboard OCISLY. I see a successful primary mission, a recovered stage with an easily accessible set of new engineering data points...

[Brian45]

Any word on the fairing recovery? There was mention early in this discussion about the Mr. Stephen (?) possibly attempting recovery of the fairing, but that seems to have dropped off the radar.

[LaunchedIn68]

Sure... But the whole trend of "do I get a cookie if I'm the first one who spots a problem"-posts is just a tad obsessive. Do they think that SpaceX is unaware or blind to the issue unless you point it out?

And then people start rushing in to post about problems they imagine, just so they can be "first" to spot a problem, just in case. Is the core bent? Is there a buckle? Is a leg damaged? Is the an engine bell damaged? These are all examples from the last year, BTW... When the specific concerns turned out to be false.

The kerosene fire is obviously not normal, but people do take that to the N'th degree as well.

Gentlemen,

You can't discuss things like this here, this is a DISCUSSION thread! 

Edit/Lar; fixed quotes. But seriously, this IS a discussion thread, not the party thread so let's not get to carried away with Dr Strangelove pastiches OK???

[LouScheffer]

Tweet from Jonathan McDowell:
Mugunghwa-5A (Koreasat-5A) and Falcon 9-45 Stage 2 tracked in 285 x 50185 km x 22.0 deg supersync transfer orbit, confirming launch success

Don’t know what the target was, but this is what was achieved.

That's about 1617 m/s to GEO, by my estimation.

My original estimate is a little too high.   It's better to do some of the inclination reduction with each burn.  A better sequence is:
Burn at apogee into orbit = 35786  by  50185  by  1.0   degrees.   Costs 1386.7 m/s
Burn at perigee into a GEO orbit, 35786  by  35786  by  0  degrees.  Costs 223.6 m/s
For a total of 1610.3 m/s, saving an additional 7 m/s.

[Rocket Science]

Some folks just need to lighten up when it comes to any critique of SpaceX even if positive...

[cscott]

Any word on the fairing recovery? There was mention early in this discussion about the Mr. Stephen (?) possibly attempting recovery of the fairing, but that seems to have dropped off the radar.

We generally hear very little directly about fairing recovery.  Your best bet is to watch the ASDS threads here; we sometimes get photos of the support ships when they return to port, and occasionally they will have suggestively-tarped bits on deck.

[cscott]

There are multiple reasons for this but gaining flight-knowledge on "sideways" reentry of a rocket body is the main driver.

If that's the case, wouldn't it make more sense to utilize titanium grid fins instead since they have greater control authority and would allow for even higher angles of attack?

The Ti fins do have greater control authority, but the 'bear trap' leading edge actually reduces drag. Perhaps SpaceX have been re-thinking that aspect of the design?

Perhaps they've figured out how to get higher angles of attack with the Alu fins, and/or found a better thermal protection mechanism for them.  Or they want apples-to-apples comparisons of various reflight profiles so they are having Alu fins for all of a given test set.

Lots of possible reasons (other than the obvious one, cost).  OneSpeed suggested that the Alu fins might be higher-drag, which could be advantageous for whatever data they are trying to collect.  I'm sure other posters here could probably come up with more possibilities.

[JamesH65]

There are multiple reasons for this but gaining flight-knowledge on "sideways" reentry of a rocket body is the main driver.

If that's the case, wouldn't it make more sense to utilize titanium grid fins instead since they have greater control authority and would allow for even higher angles of attack?

I reckon those Ti fins are VERY expensive, so they might not want to risk losing them if they don't need to.

Perhaps, but so are the stages themselves and they are apparently willing to risk losing them.

But if  they KNOW that they might lose the stage, why use the expensive grid fins? Keep those for landings they are confident about.

[Robotbeat]

It's possible the titanium fins allow much greater body lift (this has been hinted at), but that that requires modifications to the structure of the booster we won't see until Block 5.

[cscott]

It's possible the titanium fins allow much greater body lift (this has been hinted at), but that that requires modifications to the structure of the booster we won't see until Block 5.

Elon mentioned FH required strengthening the booster, so given SpaceX's preference for commonality it would make sense for the stronger components to be part of block 5.

[cuddihy]

That appears he was talking about the core FH booster. They're using refurbished F9 boosters for the demo side boosters I thought, those would be block IV at best.