Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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)

58
votes
8answers
30k 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 ...
18
votes
3answers
12k 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 ...
11
votes
3answers
1k 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 ...
9
votes
2answers
584 views

Final conclusion/description of the cause of the SpaceX Sept. 1, 2016 anomaly?

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 ...
26
votes
3answers
10k 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 ...
7
votes
1answer
820 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?
5
votes
1answer
692 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 ...
25
votes
1answer
17k 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: ...
20
votes
7answers
14k 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 ...
22
votes
4answers
2k views

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? ...
15
votes
2answers
1k 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 ...
4
votes
2answers
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 ...
14
votes
5answers
6k 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 ...
52
votes
2answers
17k 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 ...
37
votes
3answers
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? ...
21
votes
1answer
5k 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-...
19
votes
2answers
4k 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 ...
24
votes
2answers
11k 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 ...
12
votes
1answer
4k 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 ...
6
votes
1answer
593 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 ...
3
votes
1answer
846 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 ...
27
votes
2answers
31k 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 ...
51
votes
3answers
43k 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 ...
48
votes
2answers
10k 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 and would ...
23
votes
2answers
21k 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.
32
votes
6answers
18k 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 ...
11
votes
2answers
3k views

What limits the number of times that a liquid fueled rocket can restart?

I know the upper stage of the Falcon 9 can be restarted once, thus allowing an additional thrust for some circumstances that might require it. However, I don't really understand the mechanism that ...
18
votes
3answers
3k 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, ...
18
votes
4answers
4k 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 ...
16
votes
1answer
1k views

Has SpaceX re-used a first stage twice yet?

SpaceX has re-used a first stage once, several times now. Has it re-used the same first stage twice yet? If not, has a particular mission been named that will be the first second re-use?
9
votes
3answers
1k 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 ...
9
votes
1answer
1k views

Why the strange bands of soot of the landed F9 first stage?

If you look at the daylight photos of the landed first stage of the Orbcomm G2 Falcon 9 mission, there is all sorts of soot covering stuff in interesting patterns. What elements of the soot pattern ...
7
votes
1answer
504 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 ...
10
votes
2answers
768 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 ...
7
votes
2answers
2k views

Where are the COPVs on Falcon 9's second stage?

Following the most recent Falcon 9 Rapid Unscheduled Disassembly, Elon Musk tweeted that "There was an overpressure event in the upper stage liquid oxygen tank. Data suggests counterintuitive cause." ...
5
votes
1answer
1k 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?
4
votes
2answers
2k views

Problems compressing the helium tanks inside the F9 2nd stage LOX tank at the last minute?

A recent "Anomaly Update" dated September 23, 1:00pm EDT by SpaceX, includes the sentence: "At this stage of the investigation, preliminary review of the data ...
2
votes
3answers
505 views

Could a Falcon 9 booster “abort” a landing, then land shortly thereafter, or somewhere nearby?

This comment below this question has me somewhat convinced that it would be hard for a Falcon 9 booster to abort a landing at the last minute (say within the last 100 meters or something like that) ...
2
votes
1answer
627 views

What flame is SpaceX's Hans Koenigsmann describing in his presentation?

At 35:46 in part 1 of this recording of SpaceX's Hans Koenigsmann's talk at IAC 2018, he says something like: The green stuff that you see is TEA-TEB, that’s the ...
51
votes
3answers
16k views

Why would NOAA restrict the ability of SpaceX to live stream the second stage?

I was watching the live stream of the Iridium-5 launch and they mentioned that NOAA had restricted their ability to live stream the second stage and that SpaceX was working to remove this restriction. ...
28
votes
4answers
7k views

Why does the Falcon 9 have 9 engines?

What are the reasons for using 9 engines in the first stage of the Falcon 9? Why not 8 or 10? Looking at the Raptor engine, they seem to be looking at 9 engines again. Is there some specific advantage ...
15
votes
3answers
3k 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 catched by an elevated cable net. The previous ...
14
votes
3answers
4k views

Is the supercooled LOX used in Falcon 9 Full Thrust a first?

One of the changes made to the Falcon 9 v1.1 Full Thrust was using supercooled liquid oxygen at 66 K (-340 F) as well as chilled RP-1. I've seen various claims that this is a first in the industry. ...
13
votes
2answers
3k 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 ...
9
votes
5answers
3k views

Mathematics used for SpaceX first stage re-entry burn guidance?

I thought it would be fun to make a basic simulation of a first-stage fly-back of SpaceX's Falcon 9, but was wondering what mathematics is used to perform something like this. Looking at this page: ...
31
votes
2answers
4k 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'...
21
votes
1answer
3k 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%...
21
votes
2answers
2k views

What are the two bright objects separating from the Falcon 9?

On the recent Iridium 1 launch the separation of the first and second stages can be seen at T+3:50. In the following screenshot we see the second stage burning at the lower left of the frame and the ...
19
votes
2answers
6k views

How did the Falcon 9's 1st stage return back to Cape Canaveral?

SpaceX's original plan was landing the 1st stage to a landing ship, that waits far away from the launch site, and it was like this: But tonight, the rocket's first stage landed at Cape Canaveral. ...
17
votes
3answers
7k views

Why is there so little price difference between the Falcon 9 and the Falcon Heavy?

A Falcon 9 costs 61.2M dollars. A Falcon Heavy (1 Falcon 9 + 2 boosters) costs 85M dollars. That means 1 booster of the Falcon Heavy costs only 11.9M dollars. So, why does a Falcon 9 (9 Merlin 1D + ...