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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How does the Falcon 9 know where the landing barge/pad is?

The descending Falcon 9 has got to hit (preferably gently) the tiny target of the Autonomous Spaceport Drone Ship (ASDS) in the middle of the ocean. How does the Falcon 9 know where the ASDS is? ...
ForgeMonkey's user avatar
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67 votes
8 answers
39k views

Why would SpaceX not use parachutes for the final descent of the first stage?

According to what I've read, SpaceX tried to use parachutes to recover the first stage of the Falcon 9, but it did not survive reentry. Now they plan to use 2 separate rocket burns to land: Reentry ...
neelsg's user avatar
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11 votes
3 answers
2k views

Is it normal for thrusters to "ice up"?

Towards the end of the JSSAT-14 webcast (around T+32:58), we see a thruster firing. Over the space of around 20 seconds, you can see it "icing up": What is this that's forming? Is this a normal ...
James Thorpe's user avatar
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10 votes
1 answer
2k views

Merlin engine stoichiometry

As evidenced by the bright exhaust plume at launch, the billowing black smoke rolling out of the flame trench during static tests, the wispy grey effluent from the Merlin Vacuum engine, and the layer ...
Joel Neatrour's user avatar
10 votes
3 answers
1k views

Final conclusion/description of the cause of the SpaceX Sept. 1, 2016 anomaly? What's a "buckle"?

I've just read the phys.org new item which summarizes the conclusions by SpaceX about the cause of the September 1st 2016 anomaly. I'm citing quotes in the news item which come from a SpaceX ...
uhoh's user avatar
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16 votes
1 answer
1k views

Cause of apparent plume deflection on SES-10?

While watching the SES-10 flight, starting a little after T+1:30, I noticed that the direction of the first-stage exhaust plume started to diverge from the alignment of the rocket body. The ...
Russell Borogove's user avatar
16 votes
3 answers
2k views

Why would a mission to Sun-Earth L1 have an instantaneous launch window?

I was watching the webcast for Falcon 9 Flight 15 (launching DSCOVR) when they scrubbed their first launch attempt due to some issues during the terminal countdown. Before the scrub, the narrator ...
Nate Barbettini's user avatar
2 votes
1 answer
2k views

Is it possible to calculate Max-Q without having to input an altitude

Is it possible to calculate max-q based on just upwards velocity instead of specially inputting a given altitude/air density? Based on this graph of Falcon 9 launches till MECO below "Air Pressure vs. ...
UndefinedUsername's user avatar
57 votes
2 answers
28k views

How does the Falcon 9 first stage avoid burning up on re-entry?

Now that a Falcon 9 first stage has successfully landed after a launch mission, I want to know how the first stage can avoid burning up when coming back down to earth. There doesn't appear to be any ...
Rickest Rick's user avatar
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33 votes
1 answer
29k views

What are the droplets/particles falling off rockets at launch?

In this picture from the AsiaSat 6 launch by Falcon 9 on 8th September 2014, the part of the rocket between the fairing and the engine appears to be surrounded by dust, water droplets or debris: And ...
user avatar
21 votes
3 answers
25k views

What are the differences between a standard Merlin engine and the Merlin Vacuum engine?

I know that there's a difference between SpaceX's Falcon 9 1st stage engines and the 2nd stage engine, since that stage is specifically tuned for vacuum. Wikipedia also says that the Merlin Vacuum ...
Thane Brimhall's user avatar
9 votes
1 answer
2k views

What is this debris on the CRS-10 reentry at T6:30?

There are two pieces visible in the video. Are these some sort of fairing or abalator?
Biff MaGriff's user avatar
5 votes
2 answers
1k views

Does anyone know how the Flight Club website simulates Falcon 9 launches?

Does anyone know how the Flight Club website is able to provide falcon 9 launch simulations? Given the estimated weight, fuel mass, thrust, ect, how are they able to provide a graph of how it could ...
UndefinedUsername's user avatar
5 votes
2 answers
1k views

Falcon 9 Merlin 1d thrust calculated through every moment of flight

I am currently trying to recreate the launch of falcon 9 in unity. For the calculations I need the thrust of the first stage (only doing it for one stage for now). How to calculate it depending on the ...
mad.redhead's user avatar
98 votes
3 answers
141k views

What happens to the Falcon 9 second stage after payload separation?

In a Falcon 9 launch, the second stage looks like it achieves orbit along with the payload. But is that impression accurate? Does SpaceX need to do anything to deorbit the stage? I can see a few ...
Hobbes's user avatar
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33 votes
2 answers
10k views

What holds SpaceX’s rocket in place in this launch?

On a recent launch video, the gantry is at an angle and only loose tethers are attached as the rocket is prepared for launch. What is keeping it upright and in place at this point? The engines haven'...
MarsJarsGuitars-n-Chars's user avatar
21 votes
4 answers
6k views

How does a simple construction keep a firing rocket on the ground?

Today I have seen this report of a SpaceX Falcon 9 rocket test firing. The force of a burning rocket is tremendous, and in the video we see an apparently simple construction keeping the rocket (or ...
James C's user avatar
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20 votes
3 answers
4k views

Why is Falcon 9's shape so tall and skinny?

Compared to most rockets I know of, Space X's Falcon 9 seems unusually tall and skinny. The v1.1 version is nearly 70m tall, yet only 3.6m thick. For comparison, Atlas V is 58m tall and 3.8m thick, ...
radex's user avatar
  • 1,642
20 votes
7 answers
19k views

How stable would a Falcon 9 first stage be after it has landed on a drone ship?

Presumably, the booster would be a very light, very tall tube (Most of the fuel spent) standing on 4 fairly small legs on a ship in the middle of the ocean. It would also still contain some LOX and ...
neelsg's user avatar
  • 5,223
6 votes
1 answer
817 views

Is this explanation for the SpaceX 1-Sept-2016 anomaly plausible?

Question: Is this explanation for the SpaceX 1-Sept-2016 anomaly plausible? Or most of it at least (sans LHe)? In the recent New Atlas article SpaceX fingers helium as cause of Falcon 9 rocket ...
uhoh's user avatar
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167 votes
2 answers
269k views

What computer and software is used by the Falcon 9?

I don't know if this would be public, but what CPU / Microcontrollers are used and what software do they run on the Falcon 9? Do they use an OS or is it just bare metal programming? I found some ...
neelsg's user avatar
  • 5,223
28 votes
3 answers
11k views

What makes 21st century fairings so valuable that they'd potentially be recovered and re-used?

I've read in @geoff's answer that SpaceX is doing some experimentation that may lead to fairing recovery capability. In fact I remember hearing Elon Musk mentioning a few years ago that it was being ...
uhoh's user avatar
  • 149k
13 votes
3 answers
1k views

Do 'size of a bus' sized F9 fairings ever float after impact? Are they navigation hazards?

This and this answer describe the Falcon 9 fairings as being quite large, with the payload volume being roughly "the size of a bus" or simply REALLY REALLY big. 13 meters by 4.6 meters and being ...
uhoh's user avatar
  • 149k
5 votes
1 answer
970 views

Falcon 9 2nd stage pusher; how far does it continue to extend as it accelerates separation?

I've just watched Scott Manley's video SpaceX's Water Landing Reveals Rocket "Secrets" (or, What We Learned from CRS-16) (again) and he mentions the second stage "pusher" in the center of the view (...
uhoh's user avatar
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28 votes
2 answers
31k views

What is the cost breakdown for a Falcon 9 launch?

I don't know if this was already asked, but I'm very curious about the cost breakdown of a Falcon 9 launch.
zbarni's user avatar
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24 votes
2 answers
16k views

How are the SpaceX Falcon 9 Mod 3 and Mod 4 grid fins different?

Elon Musk tweeted "Flying with larger & significantly upgraded hypersonic grid fins. Single piece cast & cut titanium. Can take reentry heat with no shielding." These have been commonly known ...
geoffc's user avatar
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20 votes
3 answers
8k views

Why does the video feed always fail during Falcon 9 landings?

I'm in love with SpaceX and Falcon 9, I watch every live stream and the most special, most amazing, most thrilling part of each launch is the 1st stage landing. Seeing the smoke (or vapor) clear and ...
Coomie's user avatar
  • 2,907
13 votes
5 answers
7k views

How is SpaceX going to land their Falcon first stage?

SpaceX's attempt at a reusable first stage rocket sounds amazing, but how they're going to get it to land back on the launchpad is beyond me. Assuming that the first stage will separate with a speed ...
InquisitiveInquirer's user avatar
4 votes
2 answers
2k views

Can Falcon 9 first stage landing final burn using one, two, and three engines? Tradeoffs?

This question is about the final burn in the landing sequence of the Falcon 9 first stage return to Earth tests. If I understand correctly, there is usually far more thrust than there is weight at ...
uhoh's user avatar
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35 votes
3 answers
4k views

Why was AMOS-6 mounted on the rocket for a test fire?

I understand that the static test is a general test of pre-launch procedures, but risking a multi-million dollar payload for a test seems remarkable. Couldn't they use a mass simulator or something? ...
Abacus Lever's user avatar
26 votes
1 answer
5k views

What makes the Merlin vacuum engine so deeply throttleable?

According to the October 2015 revision of the Falcon 9 User's Guide, the Falcon 9's first stage Merlin 1D engines have a 70%-100% throttle range, while the second stage Merlin 1D Vac engine has a 38.5%...
Russell Borogove's user avatar
20 votes
1 answer
7k views

How does SpaceX ignite their engines?

Based on the aborted launch on Thanksgiving 2013 of the first Falcon 9 v1.1 from Florida, we know that an issue occurred where oxygen got into the ground based TEA-TEB sources. I understand that TEA-...
geoffc's user avatar
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18 votes
2 answers
6k views

Falcon 9 fairings cost and reusability

I read that SpaceX is starting to work on fairings reusability. I couldn't find any information, so I would like to know more about them. In particular, I remember a quote from Musk saying that ...
pastullo's user avatar
  • 1,216
16 votes
1 answer
7k views

How effective are Falcon 9 1st stage grid fins in the last few seconds before landing?

This answer discusses the three methods that the Falcon 9 1st stage uses for attitude control during re-entry and landing. They are: cold nitrogen jets, "hypersonic" grid fins, and thrust vectoring of ...
uhoh's user avatar
  • 149k
14 votes
3 answers
2k views

Could Falcon 9 splash down IN water?

Why don't they let the Falcon 9 splash down IN water, and then recover it? Wouldn't this reduce both fuel use & potential damage?
sandra's user avatar
  • 149
11 votes
3 answers
3k views

GSLV MK2 vs Falcon 9 - Reasons for Huge performance difference

Yesterday ISRO operated the GSLV MK2 launch vehicle, which is a medium lift launch vehicle with a capability to lift 5 tonnes to LEO. I just compared Falcon 9 with GSLV MK2. Falcon 9 capability to ...
Jithin Jose's user avatar
10 votes
3 answers
2k views

Pressure inside a launch fairing - falcon 9

This article indicates that a faclon 9 launch is being delayed due to an issue with the "payload fairing pressurization system". Are launch fairings pressurized to 1 atmosphere for the benefit of the ...
OrangePeel52's user avatar
  • 2,561
9 votes
0 answers
971 views

Roughly how many self-viewing cameras are present in a Falcon 9 LEO mission?

Watch any of last year's SpaceX LEO satellite deployment missions's broadcasts in YouTube, and you can see views from at least several different cameras. At least two on the 2nd stage nozzle, at least ...
uhoh's user avatar
  • 149k
9 votes
1 answer
1k views

2nd stage speed - with respect to what? (SpaceX webcast of Orbcomm OG2 deployment)

As a follow-up question to this answer by @TildalWave, exactly what frame is used to calculate the "speed" in the inset display of speed and altitude in the SpaceX broadcast of the Falcon 9 launch and ...
uhoh's user avatar
  • 149k
8 votes
1 answer
822 views

How much time does it take to circularize a GTO orbit using ion propulsion?

SpaceX launched two GEO comsats, and is about to launch two more, that use all-electric ion propulsion. Now, I'm wondering, how much time would it take to actually make a satellite like that ...
radex's user avatar
  • 1,642
6 votes
1 answer
3k views

What is the burn time for the F9 boostback / reentry / landing burns?

I'm trying to figure out the timing of the 3 recovery burns and the total fuel reserve needed to perform them. [Answers Inlined] Boostback: [30] seconds of 3-engines at full-thrust. Reentry: [20] ...
Dave Dopson's user avatar
6 votes
1 answer
4k views

What causes the green flash during Falcon 9's ignition?

Right before Falcon 9's engines start, there's a green flash. I assume it's some kind of chemical ignition. What makes the flash the color green?
Thane Brimhall's user avatar
6 votes
1 answer
8k views

Falcon 9 Merlin engine thrust vectoring

One of the ways that the Falcon 9's attitude is controlled is through thrust vectoring of the main Merlin engine(s?). In images of older thrusters i've seen hydraulic or electric linear actuators to ...
Dragongeek's user avatar
  • 18.8k
2 votes
1 answer
952 views

How will Sherpa and Formosat-5 be configured as payload and launched?

I was reading the comments in this Reddit and I'm confused. How will Sherpa and Formosat-5 be configured inside the Fairing, and then deployed. One comment seems to suggest that Formosat-5 is one of ...
uhoh's user avatar
  • 149k
50 votes
2 answers
12k views

How does the SpaceX Falcon 9 first-stage straighten for landing?

I just saw this video of supposed "SpaceX Rocket Camera Landing Footage Fakery" with over a million views. The narrator repeatedly says it's complete garbage because he doesn't understand ...
Hugo's user avatar
  • 726
35 votes
1 answer
10k views

Why does the Falcon 9 consume hydraulic fluid?

According to many news articles, the crash of the Falcon 9 during landing on 1/10/2015 was due to running out of hydraulic fluid for the steerable hypersonic grid fins. This was seemingly confirmed ...
pbristow's user avatar
  • 453
34 votes
6 answers
21k views

Why did SpaceX attempt to land the booster on a barge instead of somewhere on land?

I understand the benefits of reusability for the rocket booster. But I don't understand why they're landing it on a barge. I've read tons of articles about this but not one has even hinted at an ...
user avatar
26 votes
1 answer
6k views

Why are Falcon 9 main engines throttled down and up shortly after launch?

On the official webcast of SpaceX's Iridium-4 mission a "throttle down and throttle back up of the Falcon 9 first stage engines" is mentioned. Why would one throttle down at a crucial time ...
Everyday Astronaut's user avatar
21 votes
4 answers
4k views

SpaceX first stage landing: Why not use an elevated net above the landing platform to catch the rocket?

The rocket would keep same descent system as now (no parachute). But instead of landing on feet, it would have long grid fins on its top that would be caught by an elevated cable net. The previous ...
Gaddy's user avatar
  • 335
18 votes
2 answers
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 ...
HumanJHawkins's user avatar

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