Questions tagged [falcon-9]

Questions regarding the Falcon launch vehicle developed by SpaceX for medium payloads (15,000 lbs) to LEO and GEO (via GTO, second stage cannot inject into GEO direct)

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12
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2answers
3k views

Why does the Falcon 9 launch 60 instead of 100 Starlink satellites at a time?

The Falcon 9 has a capacity of 22,800 kg to LEO. A Starlink satellite has a mass of 227 kg. That means that one Falcon 9 can launch 100 satellites. So why does SpaceX launch 60 instead of 100 ...
5
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1answer
238 views

How do Falcon 9 grid fins deploy?

Is it aerodynamic drag that flaps the grid fins open? Or is there a controlled mechanism for it? Pictures show the grid fins connect through a small link to something inside the rotating trunnion arm--...
8
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1answer
148 views

Falcon 9: Why does F9 first stage always lose Video Link during Entry Burn?

Typically the F9 first stage and the drone ship each lose the video connection once during landing: F9 first stage during entry burn Drone ship during F9 first stage touch down (see here and here) ...
11
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1answer
126 views

What factors do (or are expected to) limit reuse of a Falcon 9 block 5 first stage?

SpaceX have claimed (reported here) that the Falcon 9 Block 5 first stage should be reusable up to 10 times without significant refurbishment, and up to 100 times in total. What factors are expected ...
3
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1answer
134 views

What are the needle pins that go through the pneumatic pushers of the Falcon 9 fairing?

The Falcon 9 fairing uses four pneumatic pushers to impart a positive separation force between the fairing halves. The pushers all mount on half of the fairing and push against the other half. But ...
4
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1answer
262 views

What are these cartridges with holes on the Dragon trunk?

You can see them on the rim in a hexagonal pattern in the picture below. Also present in the latest version of the Dragon trunk, but less clearly than here. They alternate in color from nickel to ...
5
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3answers
419 views

How does SpaceX Falcon 9 keep balance while it is near to the landing site?

As we know, flight vehicles can't keep balance easily if they cannot propel enough air through their blades or wings. We can also see the Falcon 9 at a steeper angle a while before touching down on ...
4
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1answer
416 views

From what material and how are the Merlin engines and nozzles of it (sea level) manufactured?

I am specifically interested in the alloy used to build the engine, also about the nozzle: Is it just in one piece or welded using different sections. If they are welded then which welding techniques ...
4
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1answer
112 views

Crew dragon falcon 9 first stage shut down

Crew dragon falcon 9 first stage shut down around 6700 km/hr and starlink shut down around 7900 km/hr, but around the same time. Is this because the crew dragon weighs more?
6
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1answer
154 views

Is the Falcon 9 second stage engine throttled down to limit maximum acceleration

Is the Falcon 9 second stage Merlin vacuum engine throttled down during its burn to limit the maximum acceleration experienced by the Dragon or Crew Dragon capsule? As the second stage consumes ...
3
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0answers
88 views

What became of slowing down and recovering the falcon 9 upper stage using large balloons

On 16 April 2018, Elon Musk posted on twitter This is gonna sound crazy, but … SpaceX will try to bring rocket upper stage back from orbital velocity using a giant party balloon And then land on a ...
6
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2answers
407 views

What are the challenges in recovering Falcon 9's second stage this way?

The Falcon 9's second stage is currently disposed of each flight. I know there have been some concepts by SpaceX on making it reusable, but evidently they have not yet done so. From my understanding, ...
2
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1answer
295 views

Why are the Falcon 9 Stage-1 engines placed with offsets in the octaweb compartments?

Pictures of the octaweb show that the engines are not placed at the center of each octaweb compartment---they are closer to one side than to the other. See the picture below for an example. Focus on ...
3
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0answers
138 views

Is the outside surface temperature of a Falcon 9 below freezing? How is the LOX insulated?

This answer explains how the liquid oxygen in a Falcon 9 is evaporation cooled to maintain a temperature well below boiling, by bubbling helium through it. The temperature difference to the ...
8
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0answers
197 views

Will SpaceX paint over the NASA Worm on booster 1058 for its next flight?

For the Dragon Crew mission SpaceX flew a brand new booster (how declasse) B1058 and painted it with the old style NASA Worm logo. SpaceX owns the booster and is most likely to fly it many more times ...
11
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1answer
927 views

Falcon-9's subcooled LOX is continuously refrigerated in-situ, what about its subcooled RP-1?

@Uwe's answer to Why would sub-cooled LOX tanks need to “topped-off” until the last minute or so? explains how subcooled LOX is kept cold and dense by "in situ refrigeration"; helium is bubbled ...
26
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3answers
4k views

Falcon 9 launch process - perception of launch speed

One of the things that drew attention from my local group of rocket-watchers with the Falcon 9/Crew Dragon launch is the perceived speed of the actual launch process. We have been conditioned for ...
7
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3answers
256 views

Can Falcon 9 be fueled slowed to delay the instantaneous launch window?

DM-2's first launch attempt was scrubbed at about T−17 minutes due to bad weather at the instantaneous launch window, even though the weather was predicted to clear up as early as T+10. It was ...
0
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1answer
208 views

How does re-usable boosters by SpaceX return back and land on the deck 'Of Course I still Love You'? [duplicate]

The idea was to bring back the rockets/boosters safely and re-use them for next time. How SpaceX was able to achieve this? Intuitively there have to be multiple sensors recording and computer ...
18
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2answers
2k views

Why is the flame of the Falcon 9's 2nd stage (nearly) invisible?

During the first crewed flight of a Falcon 9 today, I watched the nozzle go from dark grey to glowing red hot, confirming that it was burning. Yet there were no visible flames. I understand this stage ...
10
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2answers
2k views

How was Demo-2's Falcon 9 booster different from any other F9?

According to The Sum Of All Knowledge, the Falcon 9 has only twice (including the 2016 ground fire destroying the payload) failed to put the primary payload in orbit. Thus, the May 30 2020 Demo-2 ...
2
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0answers
77 views

How does Falcon 9 differ from Shuttle or Apollo inertial guidance?

I read a very detailed analysis of the Saturn V. From it I learned there is a computer and guidance "room" which is an extra slice of rocket stacked between the 2nd or 3rd launch stages and the the ...
2
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2answers
153 views

What specific threshold requirements or conditions is satisfied by the SpaceX Demo-2 Crew Dragon to warrant a manned flight? [closed]

I am wondering if there has been enough tests before the maiden manned flight of Demo-2 Crew Dragon. There were an autonomous flight test a year ago and a flight abort test late last year. There seem ...
4
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1answer
152 views

What are the safety differences in launch conditions with Crew Dragon vs a normal launch?

During the scrubbed launch yesterday, one of the commentators mentioned there were more restrictions on crewed launches vs a launch of a satellite or Cargo Dragon. Is there a list of differences?
7
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1answer
243 views

Why isn't the Falcon 9 first stage severely damaged by the blast of the second stage following separation?

When the Falcon 9 experiences stage separation, why isn't the first stage severely damaged by the blast of the second stage? When separation occurs, there seems to be some mechanical force to push ...
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3answers
1k views

Why did SpaceX choose vertical integration for Starship?

Rockets are basically horizontally or vertically assembled and integrated. SpaceX selected horizontal integration for its current Falcon rockets, essentially for reasons of lower cost. This ...
2
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1answer
114 views

How is fuel distributed in multi engine rocket stages?

How is fuel distributed evenly to multi-engine rockets like the Falcon 9, Electron, or multi-engined Centaurs? I would presume that there is only one main propellant line that goes down the raceway ...
2
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1answer
140 views

How is Cryogenic fuel kept… Cryogenic in rockets [duplicate]

How is cryogenic fuel & oxidizer kept at cryogenic temperatures in rockets? I am mostly interested in the first stage of launch vehicles rather than something like a Centaur that keeps hydrolox ...
7
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1answer
93 views

Are new Falcon cores still being built at Hawthorne?

Musk has been saying for a while that at some point, they they will devote all their energy to the Starship. Falcon development has stopped at block 5, with no major iterations. It was never clear to ...
4
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1answer
491 views

How long does it take to refuel a rocket?

I've been wondering how long the refueling of a rocket, say the falcon 9 takes. That's it.
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2answers
321 views

Landing legs problem with Falcon 9 Block 5 / Starlink 3 mission

Is this a late landing burn problem? it seems that the engine touch the OCISLY ground as the landing legs flex. Landing occurs at about T+0:08:20
2
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2answers
170 views

How fast could a fully fueled Falcon 9 go to propellant depletion if started in a vacuum

I guess my question is related to somehow assembling and fueling a falcon 9 in LEO then launching it. I would say if all stages were fully fulled and the Merlins were all vacuum optimized. Situation ...
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1answer
2k views

After Crew Dragon launch abort, was Falcon 9's detonation intentional?

On 2020 January 19 SpaceX launched the Crew Dragon capsule and tested an in-flight abort, where the capsule separated from the Falcon 9 shortly after launch. Many headlines claim that the Falcon 9 ...
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4answers
8k views

Why was the SpaceX abort test not initiated by real booster failure?

Today (2020-01-19) SpaceX had a successful flight abort test. As far as I can understand, at a specific altitude, Crew Dragon fired its engines and escaped from the rocket. This test looks like a ...
13
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1answer
4k views

Why do SpaceX expect the Falcon 9 rocket to explode during the in flight abort test?

This article - https://futurism.com/spacex-blow-falcon-9-rocket-launch/amp - states that after 88 seconds, the first stage engines will shut down, and an automated abort command will be sent to the ...
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1answer
132 views

Comparing Long March 5's CZ-5-300 RP-1/LOX booster to Falcon 9 first stage; similar Isp's but very different relative volumes

Wikipedia's CZ-5-300 and Falcon 9 Full Thrust provide the following rough figures. ...
4
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0answers
42 views

What happens between Payload deployment and the ISS docking

When SpaceX is livestreaming their CRS missions they usually end up by separating the payload from the second stage with an altitude at about 200 km. But I am wondering how the payload gets up to the ...
3
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1answer
185 views

Falcon 9 Type Rocket with Raptors

I've seen the question "Why don't SpaceX just use Raptors in the F9 now since their better" asked here and there, and I understand why it isn't possible to do that- they're not a drop-in replacement ...
21
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1answer
2k views

What does 'Rocket is in self align' mean?

I've noticed during SpaceX streams (this could happen with other LSPs but I've only noticed it with SpaceX) that shortly after the vehicle goes to internal power the controller says "Vehicle is in ...
1
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1answer
113 views

When will the first Falcon-9 send something to the Moon? Will it be iSpace's HAKUTO-R?

The Teslarati article SpaceX customer iSpace updates Falcon 9-launched Moon lander, rover plans says Japanese commercial space company iSpace has provided an updated schedule for its first private ...
54
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4answers
13k views

Why doesn't the Falcon-9 first stage use three legs to land?

The immediate thought that would probably come into your mind would be "Because 4 legs is more stable than 3." However that is not always true. 3 legs offer the same or in some cases more stability as ...
6
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1answer
211 views

Does central Merlin have a different specific impulse?

On a Falcon 9 booster, does the central engine experience unique variations of its ISP due to its plume bordering the eight other plumes? If there is any influence, how does the ambient relative ...
4
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1answer
225 views

Is vertical assembly worth the cost (Ariane 6)

Very recently, ESA released a new video showing the proposed Ariane 6 rocket being assembled. This mostly takes place in a large 'moveable gantry' building where the payload is placed on top of the ...
6
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0answers
204 views

What (the heck) is this purple donut in the video of the Falcon 9 fairing's atmospheric reentry?

This SpaceX tweet (found in CNET's SpaceX camera captures incredible view of rocket part returning to Earth) shows a video taken by a camera in one half of the fairing on the recent STP-2 mission and ...
25
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5answers
10k views

Why doesn't SpaceX land boosters in Africa?

Apart from the obvious answer that it'd take too long to get the booster back across the Atlantic, why doesn't SpaceX leave the main or centre booster in space a little bit longer and guide it to land ...
8
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1answer
281 views

How much of the recovery system does Spacex remove from a Falcon 9 when using it in an expended manner?

Falcon 9s have a limit to how many times they can be reused, and, for the last flight of a booster they don't make it land (in one piece), and instead use all the fuel to help the payload. That way ...
3
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1answer
86 views

F9 - Lift Off from “Landing Legs” [duplicate]

Could it ever be possible for Falcon 9 to lift off from its own "landing legs"? i.e. no strongback, no complex launch pad support, just land somewhere, get a new second stage and a tank of gas and off ...
3
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0answers
108 views

How much do SpaceX's titanium grid fin geometrical parameters measure?

Does anyone know approximately what is the width, length, thickness and depth of the titanium grid fins used in the Falcon9 v1.1? I'm trying to make a 3D model on solidworks but can't find the ...
3
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0answers
246 views

What is the function of this Merlin engine's tube, and why is it getting red hot?

In the video of the recent SpaceX Starlink launch, one view of the Falcon-9 2nd stage engine shows a cane-shaped tube that glows red hot at the "handle" end and seems to get hotter over time....
2
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0answers
182 views

What is producing these strange lights around the Falcon 9 grid fins (Starlink launch)?

Early in the video of the launch of the first sixty SpaceX Starlink satellites we can see that after stage separation the first stage grid fins open. Around that time there are some phenomena I don't ...

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