Author Topic: SpaceX Falcon Heavy Discussion (Thread 6)  (Read 74460 times)

Offline edkyle99

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #20 on: 06/09/2017 08:09 PM »
At liftoff T/W of 1.5 means that only 66% of all thrust is lost  to gravity losses and 33% is doing reasonable work at liftoff moment, not 80% wasted and 20% work like traditional liquid-fueled rockets. Still huge gravity losses, better T/W still helps considerably.

It's the other way around, previously rockets have had really lousy T/W's because the engines have been the most expensive part of the rocket.

For a given amount of thrust on a long-burning stage, payload to orbit is maximized by having nearly the maximum amount of fuel which gives a low TWR. Fuel only becomes a liability when the tankage to hold it slows the rocket more at the end of flight than the fuel accelerates it at the beginning. For a weight-optimized liquid rocket like Saturn V that happens around TWR of 1.1 or so.

Yes, but here we were NOT talking about GIVEN AMOUNT OF THRUST.

For for given fixed amount of fuel, the payload to orbit is maximized by having maximum thrust that the structure can stand, to minimize gravity losses.

Not necessarily in this case.  The propellant is best burned in vacuum or near-vacuum, where ISP is highest.  Carrying as much of that propellant as possible up to booster staging maximizes payload.

I'm suspecting that SpaceX is planning to do this.  It would be easier to do if the core had less than nine engines.  Maybe only five or six.  The rocket really only needs three on the core at liftoff, but it needs five or so at staging for T/W>1.

 - Ed Kyle
« Last Edit: 06/09/2017 09:35 PM by edkyle99 »

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #21 on: 06/10/2017 01:35 AM »
Not necessarily in this case.  The propellant is best burned in vacuum or near-vacuum, where ISP is highest.  Carrying as much of that propellant as possible up to booster staging maximizes payload.

I'm suspecting that SpaceX is planning to do this.  It would be easier to do if the core had less than nine engines.  Maybe only five or six.  The rocket really only needs three on the core at liftoff, but it needs five or so at staging for T/W>1.

 - Ed Kyle
How does the desire for engine-out capability factor into this? Would the center core ever need to make up for the loss of an engine in a side booster?

Offline cambrianera

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #22 on: 06/10/2017 10:38 AM »
SpaceX is producing truckloads of engines, testing them internally, recovering them, refurbishing them.
Doing things correctly, reliability will be superhigh.
Engine out capability has very little meaning now.

And never had for second stage, as Jim always said.
Oh to be young again. . .

Offline Ike17055

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #23 on: 06/10/2017 10:51 AM »
Also, what happened to the sea turtles nesting period? This forum was convinced a few month ago that at the current time, no construction would be possible because of the nesting turtles. What happened?

I think turtles are in Texas. In Florida the restriction was around bird nesting season in the surrounding scrub. Either the work started before nesting season, or the season ended I guess.

Paul

Th east coast of Florida is a major nesting area for the Loggerhead, and also significant nesting of Greens take place here. Maybe some Ridleys.  A lot of activity in Florida revolves around their cycle and the legal testrictions now in place for their protection.

Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #24 on: 06/18/2017 03:13 PM »
So according to reddit user /u/aftersteveo all cores are now at the Cape, with B1025 still waiting to be transported to MgGregor for testing.

https://www.reddit.com/r/spacex/comments/6ewgm7/rspacex_discusses_june_2017_33/dj2fcc6/
« Last Edit: 06/18/2017 03:16 PM by tvg98 »

Offline intrepidpursuit

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #25 on: 06/18/2017 03:42 PM »
So according to reddit user /u/aftersteveo all cores are now at the Cape, with B1025 still waiting to be transported to MgGregor for testing.

https://www.reddit.com/r/spacex/comments/6ewgm7/rspacex_discusses_june_2017_33/dj2fcc6/

It seems extremely unlikely that they would convert the two boosters in too different places. Why build that capability twice? Also, in the recent factory fly through posted by Elon, there is a reused booster in the factory. That reused booster is most likely the second FH booster.

Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #26 on: 06/18/2017 03:46 PM »
So according to reddit user /u/aftersteveo all cores are now at the Cape, with B1025 still waiting to be transported to MgGregor for testing.

https://www.reddit.com/r/spacex/comments/6ewgm7/rspacex_discusses_june_2017_33/dj2fcc6/

It seems extremely unlikely that they would convert the two boosters in too different places. Why build that capability twice? Also, in the recent factory fly through posted by Elon, there is a reused booster in the factory. That reused booster is most likely the second FH booster.

I was under the impression that the one at the factory was B1023 (used for the Thaicom 8 mission), and the other side booster was B1025 (CRS-9), which has not left the Cape yet. Is that assessment wrong? 

Offline intrepidpursuit

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #27 on: 06/18/2017 03:52 PM »
The Thaicom booster is the side booster we have already seen test fired at McGregor. I was not aware of any flown boosters in Hawthorne, but unless that video is months old one is there. I'd guess that is CRS-9 and we just missed it moving.

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #28 on: 06/18/2017 03:54 PM »
The Thaicom booster is the side booster we have already seen test fired at McGregor. I was not aware of any flown boosters in Hawthorne, but unless that video is months old one is there. I'd guess that is CRS-9 and we just missed it moving.

Footage is old - several months at least. Flown core is 1023 back when it was being refurbed for a Falcon Heavy side core. That's why the octaweb is missing.

Offline old_sellsword

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #29 on: 06/18/2017 04:49 PM »
but unless that video is months old one is there.

It is. Notice 1033 was sitting right next to it, octaweb-less.

Offline AncientU

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #30 on: 06/18/2017 07:29 PM »
So according to reddit user /u/aftersteveo all cores are now at the Cape, with B1025 still waiting to be transported to MgGregor for testing.

https://www.reddit.com/r/spacex/comments/6ewgm7/rspacex_discusses_june_2017_33/dj2fcc6/

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Offline bdub217

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #31 on: 06/26/2017 02:07 PM »
FH 101 question. We got good closeup video of the Vandenberg strongback during the Iridium launch on Sunday. This strongback looks like its structurally built to support FH.  I hadn't seen anything about launching FHs from Vandenberg. Have I missed something?

A related question - Is the plan to still build an onshore west coast LZ?

A sort-of related question. F9 and FH capacities to LEO and GTO are readily available. Anybody have an estimates on the capacity for polar orbit for the two?

Offline rpapo

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #32 on: 06/26/2017 02:29 PM »
FH 101 question. We got good closeup video of the Vandenberg strongback during the Iridium launch on Sunday. This strongback looks like its structurally built to support FH.  I hadn't seen anything about launching FHs from Vandenberg. Have I missed something?
The original intent (2012) was to launch the first Falcon Heavy from Vandenburg.  That was back when they thought it would be easy to fasten three Falcon first stages side by side.  Since then much has changed.
An Apollo fanboy . . . fifty years ago.

Online gongora

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #33 on: 06/26/2017 02:38 PM »
FH 101 question. We got good closeup video of the Vandenberg strongback during the Iridium launch on Sunday. This strongback looks like its structurally built to support FH.  I hadn't seen anything about launching FHs from Vandenberg. Have I missed something?

A related question - Is the plan to still build an onshore west coast LZ?

There aren't currently any FH scheduled from Vandenberg.  If they do get a FH contract for Vandenberg it will probably be a DoD/NRO flight with a 5 year lead time, in which case they'd finish upgrading the pad to support FH.  It might also be possible for those upgrades to be part of the upcoming EELV development rounds over the next few of years.  Getting FH flying from one pad is the first step, and that's LC-39A for now.

They have mostly built a single pad west coast LZ, we're not sure when they'll start using it.

Offline rpapo

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #34 on: 06/26/2017 02:40 PM »
Is the plan to still build an onshore west coast LZ?
It has been built for a while now.  It's just a little way downhill from the launching pad.  It would seem somebody has been throwing up regulatory hurdles against SpaceX actually using that landing pad.

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Offline mme

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #35 on: 06/26/2017 02:56 PM »
Is the plan to still build an onshore west coast LZ?
It has been built for a while now.  It's just a little way downhill from the launching pad.  It would seem somebody has been throwing up regulatory hurdles against SpaceX actually using that landing pad.

--Ninja'd, partially.
Why does it "seem like" regulatory hurdles? Any evidence or just the go-to explanation? This is how rumors start.

Iridium is a heavy payload, it's reasonable for it to be an ASDS mission.
Space is not Highlander.  There can, and will, be more than one.

Offline rpapo

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #36 on: 06/26/2017 03:51 PM »
Why does it "seem like" regulatory hurdles? Any evidence or just the go-to explanation? This is how rumors start.
It's just me watching what is said and what is not, and drawing perhaps incorrect conclusions.  I don't recall there was any ruling about whether the sonic booms related to RTLS would adversely affect the shore life (seals in particular).  SpaceX made some noise about possibly bringing the Jason-3 first stage back RTLS, but that was not approved for whatever reason (possibly because to that point, only one landing had been successful).  As it turned out, it was a good thing it landed on the ASDS.  If it had tipped over on the Vandenberg landing pad there would probably have been bad press.  Never mind that it would very likely have landed right on target, just as every landing has since they added grid fins.

Of course neither of the Iridium launches were really candidates anyway, as they were supposedly too heavy for block 3 Falcons to RTLS.
An Apollo fanboy . . . fifty years ago.

Offline CyndyC

Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #37 on: 06/27/2017 03:46 AM »
..... back when they thought it would be easy to fasten three Falcon first stages side by side.  Since then much has changed.

Exactly why I came over here, after the grid fin discussion in the Iridium thread, and wondering how tightly the cores could be secured with those [and the legs] inbetween. So a look at http://www.spacex.com/falcon-heavy says and shows bars are connecting the cores only at the top of each first stage and at the bottom near the legs. The Falcon 9 has been flown without that extra stabilization at the top and bottom of the first stage, so the vibration loads have been much more evenly distributed. Now it appears the vibration loads will be much more concentrated somewhere near the middle. Would that be a routine engineering calculation, or something they may be risking?
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Offline raketa

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #38 on: 06/27/2017 04:16 AM »
Spacex never failed land on the land. ASDS is more challenging because size and ocean move. I will be not worried about landing on land for SpaceX any more.

Offline rockets4life97

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #39 on: 06/27/2017 11:21 PM »
It is looking like SpaceX will have about a month of downtown between the upcoming Intelsat launch and CRS-12. Is it possible that some of the FH upgrades could be completed during that time?

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