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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Has a single Falcon 9 ever launched twice in a day?

Musk says in this Tweet on Nov 9, 2019, "If we build as many Starships as Falcons, so ~100 vehicles & each does 100 tons to orbit, that’s a capacity of 10 million tons of payload to orbit ...
Evan Carroll's user avatar
4 votes
1 answer
529 views

How does the Falcon 9 upper stage settle its propellants?

I understand the upper stage separates with the use of pneumatic pushers, but what settles the propellants in the upper stage tanks so that the propellant is pushed back to the intake? The pushers ...
Jeremy's user avatar
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13 votes
1 answer
4k views

Cost per launch to ISS: Starliner vs Crew Dragon

What is the cost to NASA per launch to ISS of Starliner vs Crew Dragon? The Crew Dragon flights uses the SpaceX Falcon 9-FT with the first stage reusable, along with the partially reusable Crew ...
Sheldon's user avatar
  • 555
5 votes
1 answer
213 views

Will the International Space Station be able to see the Falcon 9 (Inspiration4 launch)

Will astronauts aboard the International Space Station be able to see any part of the Inspiration4 flight of the Falcon 9 during launch and/or during orbit?
RICK's user avatar
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10 votes
1 answer
2k views

How does Spacex Crew Dragon capsule deorbit?

Soon the Inspiration 4 mission will launch and the crew will orbit the Earth for three days. How will the crew capsule then deorbit? Will it use the super/regular Draco thrusters?
moshevi's user avatar
  • 479
8 votes
1 answer
272 views

Would it be possible for a Falcon 9 booster stage to land after an in-flight launch failure?

We all know that the Falcon 9 is designed for reusability, but there still have been some hull losses. Though this hasn't happened yet, say a Falcon 9 experiences an in-flight failure where four core ...
WarpPrime's user avatar
  • 3,125
4 votes
0 answers
201 views

How does a returning Falcon first stage decide when to end its re-entry burn?

When a Falcon 9 first stage is returning to Earth to land, it performs a brief re-entry burn in order to slow down. My question is, what criteria does the first stage control software use to decide ...
Jeremy Friesner's user avatar
8 votes
1 answer
537 views

Why do recent launch vehicles like that of Space X and Rocket Lab have far fewer umbilicals than before? What has changed?

Launch vehicles using mobile launch pads have many umbilical connections, whereas the ones using TEL launch structure with strongback, don't. Why is that? As seen in the picture, Electron has just one ...
suzi Venus's user avatar
4 votes
1 answer
632 views

Which Falcon-9 launches were of a Falcon-9R rocket?

I have heard about Falcon 9 1.1 and Falcon 9 FT, but what is a Falcon 9R? If I understand correctly R = "reusable" which seems to apply to a lot of them. Are the Falcon 9 FT rockets launched ...
uhoh's user avatar
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2 votes
1 answer
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Puzzler; what can we learn about the distance and direction of Earth from this cool SpaceX-tweeted image of Earth and a vacuum nozzle?

The 18-June-2021 Spacex-tweeted below says: View from Falcon 9's second stage Merlin Vacuum engine There is information out there about the approximate exit diameter and length of the nozzle and ...
uhoh's user avatar
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22 votes
2 answers
4k views

Do Falcon 9s get a thorough wash or a fresh coat of paint (they look clean pre-reflight)?

Before/during reflight, the boosters look white and clean, but after, they don't. I'm not sure if that's soot and/or burned paint. I looked but it doesn't seem to have been asked before. RE Is Falcon ...
ymb1's user avatar
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3 votes
1 answer
465 views

Moment of inertia data for rocket stage?

I'm modeling a rocket launch and would like to compare my calculated moments of inertia to actual real-world data from other rockets. Any rocket would do, though those similar in size to Falcon 9 ...
user avatar
6 votes
0 answers
237 views

Bumps/nodes on rocket skin: What are they?

I've wondered for a while now what the many bumps and nodes on a rocket's skin are. Picture below for example (red lines mark bumps). Can someone clarify?
user avatar
7 votes
0 answers
229 views

Crew Dragon: How thick is the skin?

Auto body panels are about 20-gauge, or just under 1 mm thick. This is fine for many reasons: thin panels are light for good fuel economy and crumple easily for shock absorption without unnecessary ...
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2 votes
1 answer
115 views

Dragon Launch Escape: Attitude Control?

I've read the superdracos have a deep throttle range suited for attitude control during powered landings---an old requirement that's long been dropped. This has me wondering: are the superdracos ...
user avatar
6 votes
1 answer
423 views

Crew Dragon: Could launch escape thrust determine payload capacity?

The superdracos in Dragon's launch escape system each produce $\color{black}{\texttt{71.2 kN}}$ (16,000 lbf) of thrust. There are eight superdracos, giving a combined thrust of $\color{black}{\texttt{...
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0 votes
1 answer
124 views

What is the semicircular puff coming from the Falcon 9 first stage in this picture?

When I was watching the Crew 2 launch this morning, I noticed that while the first stage was coasting up and back down, it kept giving off arc-shaped "puffs". I did not see any corresponding ...
Charles Staats's user avatar
2 votes
0 answers
38 views

Dragon launch escape: roll control?

Dragon’s four superdraco pods are positioned well for pitch and yaw control, but not for roll control. So I’m wondering how they’ll control for roll during launch escape—or if they’ll even control for ...
user avatar
2 votes
1 answer
110 views

Dragon launch escape: is nose cone ejected for parachute deployment?

Dragon’s landing parachute is stowed roughly in the nose cone hinge area, and this leads me to believe the nose cone has to open for the chute to deploy. In normal operations, I believe the nose cone ...
user avatar
2 votes
1 answer
241 views

Dragon Superdracos: how much MMH/NTO propellant?

How much Monomethylhydrazine + Dinitrogen tetroxide (MMH/NTO) hypergolic propellant does the Dragon crew module carry and how much burn time does that afford them during launch escape if one is ...
user avatar
5 votes
1 answer
189 views

Do Falcon 9 grid fins lock up during reentry?

Do Falcon 9 grid fins lock up when extended during reentry? Or do they rely on aerodynamic forces to keep them extended once they're deployed? Could the fins flail down during the reentry burn when ...
user avatar
2 votes
2 answers
286 views

Falcon 9 vs Apollo Landing: Key Differences?

So I'm struggling to model a Falcon 9 vertical landing. And because Falcon 9 info is scarce, I'm looking for more public info sources---like the apollo missions. The Apollos did basically vertical ...
user avatar
3 votes
0 answers
144 views

Falcon 9: transonic attitude control on reentry

Attitude control on the falcon 9 is done with engine thrust vectoring, cold gas thrusters, and grid fins. After the reentry burn, when the rocket stage is in the atmosphere, there is a short period ...
user avatar
4 votes
0 answers
289 views

Falcon 9 cold gas thrusters: why in line with grid fins?

The cold gas thrusters of the Falcon 9 are right in line with the grid fins. The grid fins deploy immediately after MECO and stay deployed while the cold gas thrusters fire. And it seems the expelled ...
user avatar
3 votes
0 answers
209 views

Why do Falcon 9 grid fins open in piecemeal fashion?

The grid fins on Falcon 9 seem to open in piecemeal fashion: extending a few degrees, pausing, extending a few degrees, pausing, etc. Any reason why this happens? The rocket stage is around 80 km high,...
user avatar
2 votes
1 answer
470 views

How do grid fins actually work? Which aerodynamic mechanism(s) produce the torque on the spacecraft?

I’m trying to model the steering force that grid fins exert on a falcon 9. I know these things are not just grid-shaped fins but actually grids of fins. And each of those fins will experience drag and ...
user avatar
1 vote
1 answer
130 views

State vector update on reentry

The integration errors from IMU state measurements would seem very problematic when you're coming in for a landing, where error tolerances would probably be as small as they could get. This must mean ...
user avatar
3 votes
2 answers
541 views

Ullage control with single engine stage?

How does a single-engine upper stage, like that of Falcon 9, do ullage control before starting the engine? Does it fire its cold gas thrusters? Does it fire the engine at minimum throttle for a second ...
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0 votes
1 answer
64 views

Ullage control on stage shutdown?

Is ullage control a thing only engine startup? Would a rocket like the Saturn V or Falcon 9 leave an engine running for a second or two longer just for ullage control?
user avatar
2 votes
0 answers
1k views

Vertical Landing: Calculating start altitude for hoverslam landing burn

So I've been thinking about hover slam landings. I want to simulate one. This is the best I've come up with so far. It's all high school physics. Am I far off? Scenario Say you're landing a rocket ...
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1 vote
0 answers
77 views

Falcon 9: Landing leg helium pressure?

So it seems the Falcon 9 landing legs are powered by a helium precharge. Does anyone know the pressure of that precharge? If no numbers for Falcon 9, is there at least a reasonable range of what the ...
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7 votes
1 answer
511 views

How did the SpaceX come up with such a disruptive design in the Falcon 9?

Because of the answers to Why has a rocket system like Starship never been proposed before? , now I need to ask something I'd always taken for granted. If Falcon 9 wasn't revolutionary for technical ...
kim holder's user avatar
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3 votes
0 answers
71 views

Falcon 9 Flipover Direction?

Consider a Falcon 9 at MECO. The rocket's close to 30 deg relative to the local horizon, down from the 90 deg it had at launch. Stage 1 separates and flips more or less 180 degrees for the return ...
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0 votes
1 answer
130 views

Falcon 9: How many engines on first burn in two-burn reentry?

Consider a Falcon 9 two-burn reentry maneuver. My understanding is that the second, final, burn is always single-engine. And I think the first burn can be either single-engine or three-engine. But I'm ...
user avatar
0 votes
0 answers
47 views

Falcon 9 legs: precharged helium?

I've read the Falcon 9 uses helium pneumatics to extend its legs. The separation pushers are also helium pneumatics and I believe those are precharged so no pumps required. Are the leg cylinders ...
user avatar
2 votes
1 answer
738 views

Hover Slam Landing: How is it Done?

I want to simulate a hover slam landing. Is there an overview of the maneuver anywhere? I'm especially interested in the control algorithm used to bring the rocket stage to a halt at just the right ...
user avatar
3 votes
2 answers
684 views

Falcon 9 Max Q on reentry?

Max Q for a Falcon 9 is on the order of 30-40 kPa during launch. What would the number be on descent? Do they allow for greater dynamic pressures in that portion of the flight? Or is the rocket still ...
user avatar
11 votes
2 answers
3k views

What is this line, what is it called, what is the reason behind it?

I started following SpaceX recently. I used to read the updates but now I am diving deeper to learn new things. SpaceX is fascinating and I really like everything about it. But I have question, I don'...
Maharshi's user avatar
  • 547
3 votes
1 answer
265 views

Can Falcon 9's engines be ignited more than 4 times if there is enough TEA-TEB?

SpaceX's Falcon 9 uses TEA-TEB as a ignitor for its Merlin engines. My question is if the rocket has more TEA-TEB, can the engine be shut down and restarted more than 4 times?
Ashvin's user avatar
  • 2,644
3 votes
1 answer
602 views

If a company/agency has already developed a kerolox/hydrolox rocket, is it wise for them to switch to an all-methalox rocket? (to lower costs)

Multiple rockets, such as the Atlas V or Saturn V, have used the combination of a kerosene/liquid oxygen (kerolox) lower stage for higher density and thrust within the atmosphere and a liquid hydrogen/...
mikusingularity's user avatar
2 votes
0 answers
338 views

Falcon 9: Stable platform or strapdown IMU?

What type of IMU does the Falcon 9 use? Is it a stable platform aligned with a global frame by gimbals? Or is it a strapdown system fixed to the body of the rocket and therefore aligned not with a ...
user avatar
1 vote
1 answer
464 views

How long is Falcon 9 suicide burn?

My question is How long is a Falcon 9 suicide burn? I assume the answer might vary between rides, depending on the payload lifted and its destination orbit so the time might not be the same for a ...
Tintin's user avatar
  • 113
3 votes
0 answers
272 views

What is the inlet and outlet pressure of Merlin LOX/RP-1 turbopump?

I got the inlet and outlet pressure of Saturn V engines turbopumps here, but I couldn't find the turbopump pressure of the Merlin engine of Falcon 9.
Hello Humans's user avatar
2 votes
1 answer
156 views

Does Falcon 9 perform static fires before every launch?

Before launching every Falcon 9 rocket, is SpaceX performing a Wet Dress Rehearshal (WDR) and a static fire? If not before every launch then is it doing it before every first launch of a new booster? ...
Joe Jobs's user avatar
  • 2,630
0 votes
0 answers
74 views

How long to flip over stage 1 of Falcon 9?

Curious how fast stage 1 flips over. 180 degrees is a lot of turning. At a rate of 5 deg/s, it would take 36 seconds to flip. This seems very long for the maneuver. A more modest duration of 10 s ...
user avatar
0 votes
1 answer
1k views

Falcon 9 altitude and speed during reentry burn?

After MECO, stage 1 of Falcon 9 does up to three engine burns: a boostback burn followed by a reentry burn followed by a final landing burn. I'm interested here in the reentry burn. How high and how ...
user avatar
2 votes
0 answers
171 views

How much lower is max q if launching from high altitude (i.e. mountain top)?

I looked at very simple max q formula: q=1/2 ρv^2 (https://en.wikipedia.org/wiki/Max_q). As air density is lower with altitude, the max q should be lower as well, and also should occur at higher ...
gvidas astromskas's user avatar
1 vote
0 answers
139 views

Falcon 9 Angle of attack on return flight?

Do they control for angle of attack on the return flight of stage 1 of Falcon 9? Once it reenters thick atmosphere, aerodynamic stresses would be a concern as during launch, maybe more so because you ...
user avatar
2 votes
0 answers
45 views

Falcon 9 Stage-1 Reentry Burn: Throttle Setting, Duration?

How long does stage 1 of Falcon 9 fire its engines during its reentry burn, and what throttle setting do they use? Also, is it known how much fuel is left at MECO? Thanks if you know and can share!
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2 votes
0 answers
56 views

Does the Falcon 9 stage 1 have cold gas thrusters near the bottom?

I've seen the cold gas thruster pods on the interstage of Falcon 9, and I know that stage 2 has them too, even if there seem to be zero pictures of them on the web (they're the only means of roll ...
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