Author Topic: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion Thread 1  (Read 580989 times)

Offline intrepidpursuit

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #160 on: 11/03/2017 02:28 PM »
We have a thread devoted to the topic of booster separation on Falcon Heavy that perhaps needs a bump now. This post more or less summarized what we know thanks to old_sellsward.

https://forum.nasaspaceflight.com/index.php?topic=43255.msg1698889#msg1698889

Offline georgegassaway

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #161 on: 11/03/2017 02:39 PM »

Both the nosecones and the octawebs have pneumatic pusher mechanisms, and the octawebs also have a beefy connection point at the hold-down lugs. Whether or not that pivots before full separation is to be seen though.

OK, thanks.  Given similar pneumatic pushers on the Octawebs, it may be that those would not provide as much of a push as the ones on the nose.  Therefore causing an outwards  yaw as well, not just a parallel outwards separation. Would not require RCS to begin the yaw  alone.

Will be VERY interesting to see onboard video(s) from the boosters as the separation time nears. Perhaps splitscreen with a camera on the center core, showing both outer boosters as they begin to separate, and a camera on one of the  boosters which would not only show separation, but as it yaws outwards, the other booster being in view for awhile.

Could also be interesting if they added a new camera location on the boosters, looking towards the core, to show a view like this from shuttle SRB's.  Not for PR purposes, they'd need to justify it for engineering study purposes (this is a very high-risk phase so they'd want to document this very well to see how well it goes, or worst-case try to figure what went wrong)


Offline woods170

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #162 on: 11/16/2017 09:06 AM »
Quote
Shotwell: a few more launches for SpaceX this year including “hopefully, knock on wood” first Falcon Heavy.

https://twitter.com/jeff_foust/status/931082821002846208


Note: less than two months ago no less than 3 SpaceX leaders were certain FH would launch in December this year. Now one of them is knocking on wood and hopes it will launch in December this year.


Slippery little bastards them heavies...
« Last Edit: 11/16/2017 10:22 AM by woods170 »

Offline 2megs

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #163 on: 11/16/2017 11:30 AM »
Slippery little bastards them heavies...

I don't necessarily read it as a slip. Once they have it vertical on the pad, the timeline to launch may be driven as much by analyzing and resolving unknowns as by the work they already anticipate. Shotwell knows that; she's not Musk and tends to not over-promise.

So coming from her, I interpret a statement like that to mean the rocket will be vertical on the pad early enough that a launch in December can happen if no significant issues are identified in the WDR and static fire. It's in the realm of possibility, but not certainty, and with a new configuration that's all anyone can credibly promise.

Offline whatever11235

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #164 on: 11/16/2017 11:41 AM »
I agree with 2megs. Shotwell is much more conservative on schedule, maybee even too much. Anti-Musk.

Offline cscott

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #165 on: 11/16/2017 11:53 AM »
I think they make a good leadership pair.

Online Lar

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #166 on: 11/16/2017 11:58 AM »
I think they make a good leadership pair.
When the history of how we finally became an interstellar civilization is written, I hope she gets all the credit she so richly deserves, because they make a GREAT team.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline woods170

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #167 on: 11/16/2017 01:20 PM »
I agree with 2megs. Shotwell is much more conservative on schedule, maybee even too much. Anti-Musk.

Not by a long shot. Take some time and compare Gwynne-provided estimates from the past 5 years with Elon-provided estimates from the past 5 years. Both are generally over-optimistic. The only difference is that Gwynne is slightly less over-optimistic compared to Elon. Both are anything but conservative on schedule.

Gwynne may be the SpaceX President and COO, but it is Elon (as CEO and CTO) who is setting the pace. Gwynne's only option is to follow.
« Last Edit: 11/16/2017 01:23 PM by woods170 »

Online Lar

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #168 on: 11/16/2017 01:47 PM »
... follow .... Or quit.

And let's hope she doesn't do that. We're a bit off topic, but it would be a serious blow to lose her. She's the adult in the room :)
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline AncientU

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #169 on: 11/16/2017 02:54 PM »
... follow .... Or quit.

And let's hope she doesn't do that. We're a bit off topic, but it would be a serious blow to lose her. She's the adult in the room :)

Frequently true. 
Making payroll for 7,000 employees is not to be taken lightly -- not that either of them do -- but his pragmatic approach to rapidly design/test/iterate is likely countered by her equally pragmatic financial approach, 'how-we-gonna-pay-for-that'?
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Online Comga

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #170 on: 11/16/2017 09:41 PM »
I agree with 2megs. Shotwell is much more conservative on schedule, maybee even too much. Anti-Musk.
I think they make a good leadership pair.

I agree with cscott but think its more Counter-Musk than Anti-Musk

At the risk of being an irrelevant discussion, I really hope this launch doesn't slip more than a week into the new year, because that would give me the chance to go see it.  A double triple sonic boom!

According to Google Maps, it's 9.63 km from the end of the pier at Jetty Park to where LZ-1, the first landing pad is, and ~9.69 km to the second pad as seen in the photo in this post.  <100 meters is <0.30 seconds delay, which is is close to my impression of the delay between the first sonic boom and the latter pair of booms from the returning first stage.  It would be like fireworks as they overlap, if they land simultaneously. 
Does that mean SpaceX has to delay one so it doesn't interact with the shock wave from the other?
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline rpapo

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #171 on: 11/16/2017 09:59 PM »
Does that mean SpaceX has to delay one so it doesn't interact with the shock wave from the other?
Actually, from the point of view of sonic booms, I would expect that having both rockets come down side by side, separated by a few hundred meters, would probably be best.  The interaction between the sonic booms would happen well above and away from the descending rockets.  The only dicey point would be the transonic regime, when the shock wave front is nearly planar.

EDIT: Thinking about this, I hope the tracking cameras can catch that area in their view.  It may be interesting.  How often do we see two large objects generating shock waves only a few hundred meters apart? 
« Last Edit: 11/16/2017 11:40 PM by rpapo »
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Offline georgegassaway

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #172 on: 11/17/2017 03:32 AM »
There is some likelihood that the two side boosters will not do a perfect mirror / synchronized separation pitch-around (& yaw-around) such that one might end up a little bit farther downrange than the other, and not “catch up” with the other one.  But let’s assume perfect synchronization so they’d be side by side downrange-wise, eventually landing at the same moment….. but far apart laterally for the sake of the comments below.

They would not necessarily be coming in a few hundred feet apart during the re-entry burn or going transsonic.  No need to come in at the same distance apart as the individual landing pads are. They could be programmed to intentionally be say a mile or two apart. Let’s say 2 miles apart, one a ballistic course a mile north of LZ-1 and one a mile south of LZ-1, if not more.  Somewhere between the re-entry burn and going transsonic, when the grid fins are aerodynamically steering each booster to “glide” to extend the ballistic path (which would otherwise impact offshore), they would use the same steering capability to begin to do a minor dog-leg for each to converge towards LZ-1 (South one landing at the original pad and the North one at the new pad).  So in that case, if shock waves were a concern, they could do it that way to keep them pretty far apart for a lot of the way down.

Will be interesting, after the flight, if there actually is a ground plot of the incoming booster paths, to show if they do something like that.  Last thing I would expect is they’d be  as close as 1200 feet apart horizontally (whatever the distance between the two landing pads are) during the re-entry burn or when they go subsonic (though by the time they go subsonic, they’d not be nearly as far apart as likely during re-entry, they'd be converging).
« Last Edit: 11/17/2017 03:38 AM by georgegassaway »

Offline envy887

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #173 on: 11/17/2017 01:26 PM »
How often do we see two large objects generating shock waves only a few hundred meters apart?

The military flies large supersonic jets fairly close to each other quite often.

Offline rpapo

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #174 on: 11/17/2017 01:41 PM »
How often do we see two large objects generating shock waves only a few hundred meters apart?

The military flies large supersonic jets fairly close to each other quite often.
I know that.  The Falcon is much larger.
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Offline FinalFrontier

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #175 on: 11/17/2017 02:02 PM »
Fair question here, due to Zuma slip what will be the effect if any on FH still flying before the year ends?

And/or if there are further slips due to this fairing issue.
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Offline Mike_1179

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #176 on: 11/17/2017 02:08 PM »
How often do we see two large objects generating shock waves only a few hundred meters apart?

The military flies large supersonic jets fairly close to each other quite often.
I know that.  The Falcon is much larger.

The B1-B flies supersonic and is about 45m long. It's a bit larger than a Falcon 9 first stage. While I'm not going to say that flying a rocket backwards is no different from flying a plane, it's not such a rare thing.

Offline douglas100

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #177 on: 11/17/2017 08:41 PM »
Fair question here, due to Zuma slip what will be the effect if any on FH still flying before the year ends?

And/or if there are further slips due to this fairing issue.

Stands to reason that the longer Zuma stays on the pad the less time there will be to get the TEL converted and get FH off before the end of the year. It's quite possible that FH will slip into the New Year.
« Last Edit: 11/17/2017 08:58 PM by douglas100 »
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How often do we see two large objects generating shock waves only a few hundred meters apart?

The military flies large supersonic jets fairly close to each other quite often.
I know that.  The Falcon is much larger.

The B1-B flies supersonic and is about 45m long. It's a bit larger than a Falcon 9 first stage. While I'm not going to say that flying a rocket backwards is no different from flying a plane, it's not such a rare thing.

The B-1A was designed to fly supersonically as a matter of course. The B-1B lost the variable geometry intakes that allowed for optimal supersonic cruise, which lowered its maximum speed at altitude quite a bit. Further, B model gained the dorsal ridge of ECM equipment and additional software/sensors for low level, high-subsonic penetration into hostile airspace. Supersonic flight is no longer the airframe's forte, and I daresay B-1Bs rarely break the sound barrier operationally at all, to the extent they ever did. More importantly for this discussion, B-1's of neither model were ever intended to fly supersonically within a few hundred yards of one another.

That said, B-1 generally is a typical supersonic aircraft design of the era - long, sleek and properly pointed at the end that creates the main shockwave, with swept wings and tail that also optimize their secondary shocks. By stark contrast, a falling F9 is a blunt body with vastly different aerodynamics. Presumable SpaceX has done plenty of CFD modeling of potential shock interactions and have no concerns. But we (as outside observers) should not handwave away the discussion by reference to conventional supersonic airframe design.
« Last Edit: 11/17/2017 09:25 PM by Herb Schaltegger »
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Offline Jakusb

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #179 on: 11/19/2017 10:55 AM »
Fair question here, due to Zuma slip what will be the effect if any on FH still flying before the year ends?

And/or if there are further slips due to this fairing issue.

Stands to reason that the longer Zuma stays on the pad the less time there will be to get the TEL converted and get FH off before the end of the year. It's quite possible that FH will slip into the New Year.

I would expect the other option being them to do last modification ASAP, if the fairing would have to be build again...
Then a serious delay due to the fairing-rebuild could expedite the FH Demo pre-launch activities.
And maybe move Zuma to SLC-40..? After CSR-13 of course.
They should have a general idea of impact by now. All depends on it being a fix/modification or total rebuild of fairings.

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