SpaceX Falcon 9 historic landing thread (1st landing attempt & most recent missions)

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techrat said:
The Chinese launched something just yesterday that had 4 boosters. I want to find some good photos and make a scale or semi-scale model of that. I might actually cluster that sucker just to see how it works out.
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Strapping a few SRB's or other small boosters to the side is a completely different ball game than strapping on more liquid core stages.
 
Antares JS said:
The problem with multi-core rockets like Delta IV Heavy and Falcon Heavy is that the inert mass fraction ends up higher than just building a bigger core. The theoretical advantage is that you save on the expense of actually developing a bigger core. However, the more cores you add, the worse your mass fraction becomes. I can't imagine more than three cores would be worth it.
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Do you think there is still room for a core to be bigger? (than Saturn or Starship?).
 
Funkworks said:
Do you think there is still room for a core to be bigger? (than Saturn or Starship?).
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There is probably an upper limit to how big a rocket can be when considering required inert mass and structural strength, but I don't see why a core stage bigger than the S-1C would be impossible. It just might not be practical.
 
techrat said:
They haven't built the Sea Dragon yet, so I say Yes!
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Maybe in principle, but I wouldn't bet against SpaceX's plan to have a production line for Starships. At this point, 2 launches each carrying 100 tons of bricks to build a 200 ton structure sounds more practical. I was just kind of wondering.
 
Antares JS said:
Not until the damn thing goes and I don't have to worry about it anymore.
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How far from Wallops are you? In the summer of 2018 I took five Native American students from the Tribal College I worked at to Wallops for the Colorado Space Grant RockOn workshop where we built from scratch instruments that NASA kindly flew into space for us when they were all done and certified to be working & safe. It was an amazing experience for all of us. :clapping:

https://www.nasa.gov/sounding-rockets/rocksat-programs/rockon
 
I remember reading years ago, before Falcon Heavy actually launched, that they'd considered running all engines with just the fuel from the booster rockets, and once they were empty they'd release and have a completely full core stage. They don't actually do this but I don't know why its better.

Is there an easy explanation for running all tanks down at nearly the same time instead of booster tanks first?

The core did fire a little longer than the boosters so they must have run them slightly different.
 
Mushtang said:
I remember reading years ago, before Falcon Heavy actually launched, that they'd considered running all engines with just the fuel from the booster rockets, and once they were empty they'd release and have a completely full core stage. They don't actually do this but I don't know why its better.

Is there an easy explanation for running all tanks down at nearly the same time instead of booster tanks first?

The core did fire a little longer than the boosters so they must have run them slightly different.
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What SpaceX originally wanted to do was cross-feed the propellant between the three cores, so at the same time the three cores would be providing propellant to their engines, unburnt propellant from the boosters would also be draining into the center core, keeping the center core full until the boosters separated. The advantage of this is that when you separate the boosters, you have a full or mostly full center core at a better mass fraction than the rocket with the boosters, that has already been boosted to a high speed.

They ultimately didn't do this because that cross feed system would have added even more difficulty to a project that was already way behind schedule. Musk decided to keep Falcon Heavy basic and put his innovation eggs in the Starship basket.

Both the Delta IV heavy and the Falcon Heavy run with the center core throttled down a bit compared to the boosters. I'm not sure when they throttle up the center.
 
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Antares JS said:
They ultimately didn't do this because that cross feed system would have added even more difficulty to a project that was already way behind schedule. Musk decided to keep Falcon Heavy basic and put his innovation eggs in the Starship basket.
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Thanks, I never heard that this was the reason. It makes sense.

I now wonder, if the cross feed system were designed and launched the way you and I both described, would it be an improvement in how much payload could weigh or how high it could go?
 
Mushtang said:
Thanks, I never heard that this was the reason. It makes sense.

I now wonder, if the cross feed system were designed and launched the way you and I both described, would it be an improvement in how much payload could weigh or how high it could go?
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Without crunching any actual numbers, I would say probably yes, because of the aforementioned full core that's been boosted to high speed before it starts losing any propellant. It's like a single-stick Falcon 9 launch but it's already going however many thousands of mph when the countdown hits 0.
 
Mushtang said:
I remember reading years ago, before Falcon Heavy actually launched, that they'd considered running all engines with just the fuel from the booster rockets, and once they were empty they'd release and have a completely full core stage. They don't actually do this but I don't know why its better.

Is there an easy explanation for running all tanks down at nearly the same time instead of booster tanks first?

The core did fire a little longer than the boosters so they must have run them slightly different.
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To follow on to what Antares JS said, the center core fired for a full 1:30 after the boosters dropped off, so it's almost like an air start (a bit of a stretch, I know) in that the center core throttles up late in the flight after it's basically out of the atmosphere. The cross-feed system was dropped because of cost and complexity, but also (speculation) because the updated Falcon engines had a wider throttle range than anticipated so they could accomplish basically the same goal of the cross-feed by simply throttling back the core until the boosters dropped off.


Tony

from wikipedia: "Merlin 1D was originally designed to throttle between 100% and 70% of maximal thrust; however, further refinements since 2013 now allow the engine to throttle to 40%"
 
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Mushtang said:
I remember reading years ago, before Falcon Heavy actually launched, that they'd considered running all engines with just the fuel from the booster rockets, and once they were empty they'd release and have a completely full core stage. They don't actually do this but I don't know why its better.
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It works GREAT in Kerbal Space Program! They call it "aspargus staging, because you can have a rocket with say a core and six side boosters just like the core, have the whole combo of 7 using just the fuel from two outer boosters, they run empty quickly sep, then use fuel from the next two, and so on.
eHPln.png


I did many rockets in KSP using that method.

SpaceX did indeed plan to do that, but it is hard to do in real life for various reasons. From: https://en.wikipedia.org/wiki/Falcon_Heavy#Propellant_crossfeed
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"Falcon Heavy was originally designed with a unique "propellant crossfeed" capability, whereby the center core engines would be supplied with fuel and oxidizer from the two side cores until their separation.[84] Operating all engines at full thrust from launch, with fuel supplied mainly from the side boosters, would deplete the side boosters sooner, allowing their earlier separation to reduce the mass being accelerated. This would leave most of the center core propellant available after booster separation.[85]

Musk stated in 2016 that crossfeed would not be implemented.[86] Instead, the center booster throttles down shortly after liftoff to conserve fuel, and resumes full thrust after the side boosters have separated.[3]"
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Note that Delta-IV Heavy did a sort of similar thing, throttle back the core, saving fuel in it, then dropping the outer boosters when they ran out, and thrusting onward with the center core till it ran out of the fuel that had bene saved during the low throttle phase.

Note that for on FH, all 27 engines are ignited at liftoff, core is not "air started" like Titan-III/IV. If the Merlin engines did not have as low of a throttle capability, in theory some engines could have been shut down early, then re-ignited shortly before staging, since those engines have re-ignition capability (only times any have failed to ignite, have been when they ran out of the re-ignition fluids - TEA and TEB, and future boosters were modified to have larger storage tanks for that). But they do have enough throttle to not need to do that.
 
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Just to add a somewhat forgotten part of SpaceX's achievement, they just completed their 200th upper stage/Merlin Vacuum engine pairing last week. The success of the second stage as a flight vehicle has been phenomenal, with the only in-flight failure due to a failed structural component. The only other failure was on the ground when a pressure vessel ruptured. While the booster gets all the glory, without a reliable upper stage it would all be for naught.


Tony
 

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Launch of the Galaxy 31 & 32 sats went very well! Record14th launch for that hardy booster! :bravo:

The booster needed all fuel for the launch so it had no landing legs... So it was tossed into the ocean, We did not get video of that boosters "Landing" (Watering?) tho - too bad - that would've been glorious to see!! No numbers on the booster either. :(
 
MClark said:
Falcon launch tonight. 8:39 Pacific
In So Cal and AZ it’s usually a good show

https://www.spacearchive.info/vafbsked.htm
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For one, Friday.

More importantly, Cancelled for Friday with no new date.

"UPDATE (6:14 p.m.) - Friday's scheduled launch of a Falcon 9 rocket at Vandenberg Space Force Base has been canceled.

SpaceX said it needed to take a closer look at data from the rocket's static fire test.

A new launch date has not yet been announced."

https://www.ksby.com/news/local-news/spacex-falcon-9-launch-scheduled-for-friday-evening-november-18
BTW -pretty much ANY launch to orbit, shortly after sunset, or awhile before sunrise, can be incredibly spectacular. Against the dark sky, the rocket's exhaust plume(s) are visible once they get high enough out of the Earth's shadow for the sun to shine on them, and can be seen for many hundreds of miles away. And in the case of Falcon-9's, the RCS thruster firings of the booster after staging are also visible.

 
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Huxter said:
OneWeb launch in 2 minutes! Funny how they're launching OneWeb sats - direct compitition for Starlink?
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We had a great view of the launch from our front yard about 30 miles from the launch.

Most SpaceX launches have arced to the north. This one went south. It was clear and just at sundown so I was able to see the rocket all the way to stage separation and beyond. What was also different for this launch was that I could clearly see the booster coming back all the way until it went below the trees on the horizon.

For a minute or two, it looked like the booster was heading straight for me. But then it appeared to start falling straight down.

I clearly saw the rocket motor restart to slow the booster down. A few seconds before the motor fired, it looked like an airplane flew directly above the descending booster. Even though it certainly just looked that way from my perspective, I bet some people in that jet saw a pretty neat show.

I couldn't see the landing burn, but I clearly heard it a bit later.

SpaceX really knows how to put on a show!
 
BEC said:
...and today, in the third launch in less than 36 hours, SpaceX flew and recovered booster B1058 for the 15th time. My how far things have come since the beginning of this thread.
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Truly remarkable how we have gone from no reusable rockets to boosters on their 15th flight all in a relatively short period of time.
 
Tyeeking said:
Truly remarkable how we have gone from no reusable rockets to boosters on their 15th flight all in a relatively short period of time.
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Way to go SpaceX. ... Great to see advancement like this.

[ All while NASA thinks it's a good idea to take reusable Space Shuttle Main Engines, and revert back to dropping them in the ocean as one time use. Should have sold them off to a private company. ]
 

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