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/
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 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 coreI 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...
Quote from: ZachF on 05/31/2017 06:15 pmI 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 coreI 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.
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...
Quote from: ZachF on 05/31/2017 06:15 pmFalcon 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
.@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?
Almost. Falcon Heavy was way harder to develop than it seemed at first.
All Falcon Heavy cores should be at the Cape in two to three months, so launch should happen a month after that
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 coreI 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...
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 from: hkultala on 06/09/2017 05:12 amAt 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.
