Author Topic: SpaceX Falcon Heavy Discussion (Thread 6)  (Read 79164 times)

Offline Chris Bergin

Thread 6 for Falcon Heavy.

Thread 1:
https://forum.nasaspaceflight.com/index.php?topic=32528.0

Thread 2:
https://forum.nasaspaceflight.com/index.php?topic=35365.0

Thread 3:
https://forum.nasaspaceflight.com/index.php?topic=36806.0

Thread 4:
https://forum.nasaspaceflight.com/index.php?topic=39181.0

Thread 5:
https://forum.nasaspaceflight.com/index.php?topic=41019.0



Main FH Articles:

https://www.nasaspaceflight.com/tag/falcon-heavy/

L2 SpaceX - Dedicated all-vehicle section - including a mass of new amazing renderings we've created.
https://forum.nasaspaceflight.com/index.php?board=60.0


NOTE: Posts that are uncivil (which is very rare for this forum), off topic (not so rare) or just pointless will be deleted without notice.

Offline Ronsmytheiii

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #1 on: 05/28/2017 05:39 PM »
Imagery update for 26 May at LZ-1, either dirt spreading or concrete pouring has begun (hard to tell with the lighting)

Edit:probably dirt spreading, based on the mound that appeared to the right of the clearing

Taken from Planet Beta imagery program:

https://www.planet.com/explorer/

« Last Edit: 05/28/2017 05:44 PM by Ronsmytheiii »
"Every vision is a joke until the first man accomplishes it; once realized, it becomes commonplace." - Robert Goddard

Offline TomH

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #2 on: 05/30/2017 08:02 AM »
Imagery update for 26 May at LZ-1, either dirt spreading or concrete pouring has begun (hard to tell with the lighting)

Edit:probably dirt spreading, based on the mound that appeared to the right of the clearing

Taken from Planet Beta imagery program:

https://www.planet.com/explorer/

Are construction permits a matter of public record for a case like this. IOW, could any person walk into the building permit dept. and be able to see that they had received the permit to begin construction of a new landing pad?

Offline Semmel

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #3 on: 05/30/2017 09:24 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?

Offline Paul_G

Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #4 on: 05/30/2017 10:49 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

Offline Nomadd

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #5 on: 05/30/2017 05:21 PM »
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?
In Texas the beaches are patrolled and the public calls in nesting turtles, with the eggs being recovered as soon as they're laid, and the young ones released in a safe spot. They did that before the spaceport.

Offline ZachF

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #6 on: 05/31/2017 06:15 PM »
I was thinking the other day, perhaps it makes sense now to remove some engines (3-4) from the center core?

Falcon Heavy already has a crazy T/W and with a rumored 10% thrust increase with B5 upgrades, it will be even more crazy. It already has a >1 T/W with just the outer cores firing...

Removing 3-4 engines would allow:

-Deeper throttling of the center core after liftoff, transferring more of the lower altitude impulse outer stages, allowing them to stage earlier, also reducing the RTLS fuel requirement
-Leaving more fuel for the center core after separation, both for more impulse, and more fuel for a boostback burn
-Reduce center core landing fuel requirement because of a non-trivial decrease (>3000kg?) in stage empty weight giving it a higher theoretical maximum staging velocity
-Reduce cost of center core

I think a Falcon Heavy with 5-6 engine center core might lose a little theoretical expendable performance, but could perhaps gain a good amount of re-usable performance...

Offline rakaydos

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #7 on: 05/31/2017 06:46 PM »
I was thinking the other day, perhaps it makes sense now to remove some engines (3-4) from the center core?

Falcon Heavy already has a crazy T/W and with a rumored 10% thrust increase with B5 upgrades, it will be even more crazy. It already has a >1 T/W with just the outer cores firing...

Removing 3-4 engines would allow:

-Deeper throttling of the center core after liftoff, transferring more of the lower altitude impulse outer stages, allowing them to stage earlier, also reducing the RTLS fuel requirement
-Leaving more fuel for the center core after separation, both for more impulse, and more fuel for a boostback burn
-Reduce center core landing fuel requirement because of a non-trivial decrease (>3000kg?) in stage empty weight giving it a higher theoretical maximum staging velocity
-Reduce cost of center core

I think a Falcon Heavy with 5-6 engine center core might lose a little theoretical expendable performance, but could perhaps gain a good amount of re-usable performance...

Hypothetically, a "Hexiweb" varient of the center core, with 2 vac bells offset outward and between the normal octoweb engine placement, replacing a total of 4 sea level nozzles. (leaving 5 sealevel nozzles each)

It would of course be a pain to develop, and the bell extending beyond the tank cross section will probably tear it apart.

I'm not sure simply removing engines has enough benifits over leaving engines off to be worthwhile either.

Offline hkultala

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #8 on: 05/31/2017 07:54 PM »
I was thinking the other day, perhaps it makes sense now to remove some engines (3-4) from the center core?

Falcon Heavy already has a crazy T/W and with a rumored 10% thrust increase with B5 upgrades, it will be even more crazy. It already has a >1 T/W with just the outer cores firing...

Removing 3-4 engines would allow:

-Deeper throttling of the center core after liftoff, transferring more of the lower altitude impulse outer stages, allowing them to stage earlier, also reducing the RTLS fuel requirement
-Leaving more fuel for the center core after separation, both for more impulse, and more fuel for a boostback burn
-Reduce center core landing fuel requirement because of a non-trivial decrease (>3000kg?) in stage empty weight giving it a higher theoretical maximum staging velocity
-Reduce cost of center core

I think a Falcon Heavy with 5-6 engine center core might lose a little theoretical expendable performance, but could perhaps gain a good amount of re-usable performance...

Hypothetically, a "Hexiweb" varient of the center core, with 2 vac bells offset outward and between the normal octoweb engine placement, replacing a total of 4 sea level nozzles. (leaving 5 sealevel nozzles each)

It would of course be a pain to develop, and the bell extending beyond the tank cross section will probably tear it apart.

I'm not sure simply removing engines has enough benifits over leaving engines off to be worthwhile either.

canting those two engines outwards would lower their effective isp.

And, way too complicated/too different from ordinary F9, would be more expensive to manufacture, makes absolutely no sense.
« Last Edit: 05/31/2017 07:55 PM by hkultala »

Offline RobW

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #9 on: 05/31/2017 09:54 PM »
Falcon Heavy already has a crazy T/W and with a rumored 10% thrust increase with B5 upgrades, it will be even more crazy. It already has a >1 T/W with just the outer cores firing...

Does FH really have thrust/weight >1 without the center core firing? If so, given that SpaceX must be getting pretty comfortable with in-flight engine restarts after all those landings, is it possible we could see FH launch with some/all of the center core engines unstarted, and air-light them? What could that do to performance?
Science fiction writer, spaceflight blogger, and unrepentant technological optimist.

Online docmordrid

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #10 on: 05/31/2017 10:03 PM »
I believe only 3 of the 9 engines can be restarted; 2 in the outer ring and the center engine. Wouldn't those also be the only ones air-startable for the initial firing?
« Last Edit: 05/31/2017 10:06 PM by docmordrid »
DM

Offline RobW

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #11 on: 05/31/2017 10:22 PM »
Given that the entire center core is a different design to the standard F9, presumably they could fit all 9 engines with re/air start kits if it was useful. Part of the rationale for beefing up the center core so much structurally might actually be so that they can launch with some of the center core engines not running. Think of it as an extreme form of throttling down the center core so that there is more propellant left in it at booster sep. Of course, it probably makes the center core recovery harder.

Would the real rocket scientists (engineers) please now step in with facts :)  (EDIT: This is said in reference to my wild speculations, not docmordrid's perfectly reasonable comments about the current air-start-ability of the F9 engine set. I  re-read it and wanted to make sure it was clear that it's not aimed at anyone but myself)
« Last Edit: 05/31/2017 10:26 PM by RobW »
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Offline old_sellsword

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #12 on: 05/31/2017 10:37 PM »
Falcon Heavy already has a crazy T/W and with a rumored 10% thrust increase with B5 upgrades, it will be even more crazy. It already has a >1 T/W with just the outer cores firing...

Does FH really have thrust/weight >1 without the center core firing? If so, given that SpaceX must be getting pretty comfortable with in-flight engine restarts after all those landings, is it possible we could see FH launch with some/all of the center core engines unstarted, and air-light them? What could that do to performance?
Given that the entire center core is a different design to the standard F9, presumably they could fit all 9 engines with re/air start kits if it was useful. Part of the rationale for beefing up the center core so much structurally might actually be so that they can launch with some of the center core engines not running. Think of it as an extreme form of throttling down the center core so that there is more propellant left in it at booster sep. Of course, it probably makes the center core recovery harder.

Would the real rocket scientists (engineers) please now step in with facts :)  (EDIT: This is said in reference to my wild speculations, not docmordrid's perfectly reasonable comments about the current air-start-ability of the F9 engine set. I  re-read it and wanted to make sure it was clear that it's not aimed at anyone but myself)

There's already an entire thread to discuss this idea, no need to bring it up in here again.

http://forum.nasaspaceflight.com/index.php?topic=42185

Offline RobW

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #13 on: 05/31/2017 10:46 PM »

There's already an entire thread to discuss this idea, no need to bring it up in here again.

http://forum.nasaspaceflight.com/index.php?topic=42185
Thanks, hadn't seen it. Off to have a read....
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Offline FutureSpaceTourist

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #14 on: 06/07/2017 08:05 PM »
Quote
.@elonmusk says "Building on the Model X on the [Tesla] Model S platform was a mistake" - Does the same error carry on to Falcon 9 and Falcon Heavy?
https://twitter.com/sahershodhan/status/872347614280372224

Quote
Almost. Falcon Heavy was way harder to develop than it seemed at first.
https://twitter.com/elonmusk/status/872349052016394243

Offline cambrianera

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #15 on: 06/07/2017 08:45 PM »
I was thinking the other day, perhaps it makes sense now to remove some engines (3-4) from the center core?

Falcon Heavy already has a crazy T/W and with a rumored 10% thrust increase with B5 upgrades, it will be even more crazy. It already has a >1 T/W with just the outer cores firing...

Removing 3-4 engines would allow:

-Deeper throttling of the center core after liftoff, transferring more of the lower altitude impulse outer stages, allowing them to stage earlier, also reducing the RTLS fuel requirement
-Leaving more fuel for the center core after separation, both for more impulse, and more fuel for a boostback burn
-Reduce center core landing fuel requirement because of a non-trivial decrease (>3000kg?) in stage empty weight giving it a higher theoretical maximum staging velocity
-Reduce cost of center core

I think a Falcon Heavy with 5-6 engine center core might lose a little theoretical expendable performance, but could perhaps gain a good amount of re-usable performance...

http://forum.nasaspaceflight.com/index.php?topic=39181.msg1573180#msg1573180
Low hanging fruit.
Oh to be young again. . .

Offline ThePonjaX

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #16 on: 06/09/2017 04:41 AM »
4 months  ;)

https://twitter.com/elonmusk/status/872888863504474112


Quote

All Falcon Heavy cores should be at the Cape in two to three months, so launch should happen a month after that




Offline hkultala

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #17 on: 06/09/2017 05:12 AM »
I was thinking the other day, perhaps it makes sense now to remove some engines (3-4) from the center core?

Falcon Heavy already has a crazy T/W and with a rumored 10% thrust increase with B5 upgrades, it will be even more crazy. It already has a >1 T/W with just the outer cores firing...


It's not crazy.

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.

Quote
Removing 3-4 engines would allow:

-Deeper throttling of the center core after liftoff, transferring more of the lower altitude impulse outer stages, allowing them to stage earlier, also reducing the RTLS fuel requirement

for outer stages, but increasing it for core.

Quote
-Leaving more fuel for the center core after separation, both for more impulse, and more fuel for a boostback burn
Making center core fly further away until it has expendedn it's fuel and reacher the staging altitude, INCREASING fuel needed for boostback burn.

Quote
-Reduce center core landing fuel requirement because of a non-trivial decrease (>3000kg?) in stage empty weight giving it a higher theoretical maximum staging velocity

Should not be that much, only by something like 2 tonnes. Merlin 1D is less than 500 kg's. (and no, making the octaweb much different is not an option because that would make manufacturing much more expensive)

Quote
-Reduce cost of center core

I think a Falcon Heavy with 5-6 engine center core might lose a little theoretical expendable performance, but could perhaps gain a good amount of re-usable performance...

RTLS performance would probably suffer, as the center core would fly much further away on distance before reaching staging velocity, so it would have to fly back much longer distance.

The savings for the boosters, they are not flying very far anyway, so their RTLS is cheap anyway.

Also gravity losses would be worse.

Online envy887

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #18 on: 06/09/2017 01:24 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.

Offline hkultala

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #19 on: 06/09/2017 06:18 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.
« Last Edit: 06/09/2017 06:30 PM by hkultala »

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