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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2 votes
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Is it possible for fuselages to have a negative lift coefficient at positive angle of attacks?

Recently I was interested in the descent phase of the first stage of the falcon 9 launch vehicle. I assumed a long cylinder to represent the first stage. using DATCOM to predict aerodynamics ...
2 votes
2 answers
262 views

Why doesn’t SpaceX use Falcon Heavy to launch Starlink satellites?

In this chart that I found here (https://i.stack.imgur.com/f8wOR.jpg) It shows that the price of 1 kg to LEO is cheaper on the Falcon Heavy than the Falcon 9. Also the Falcon Heavy can carry more ...
20 votes
1 answer
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Why was there only a single Falcon 9 landing on ground-pad in 2021?

According to Wikipedia, there was only one Falcon 9 booster landing on ground-pad in 2021, all other 30 launches at least attempted to land on a drone-ship. Comparatively, 2020 and (so far) 2022 both ...
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2 votes
1 answer
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Is the first stage LOX tank on the Falcon 9 monocoque or semi-monocoque?

In the Falcon 9 user guide manual it is noted that the first and second stage LOX tanks are monocoque. That means the tank is made of a single cylindrical shell. Is that possible? How can the first ...
1 vote
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Is it possible to estimate the angle of attack or flight path angle of a launch vehicle from mission web casts?

The altitude and speed is shown in the web casts of Falcon 9 missions. Is it possible to estimate the angle of attack or flight path angle?
1 vote
1 answer
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Why does the Falcon 9 come back to the launch pad despite having considerable speed after boost back burn after separation?

After separation, the first stage of a Falcon 9 makes a boost back burn. When watching the webcast of the NROL 108 mission, after boost back it has a speed of 830 km/h at an altitutde of 148 km, then ...
5 votes
0 answers
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How large is the AoA during the ascent and descent of a Falcon 9?

If we divide the mission into ascent, descent before reentry burn, and descent after that, how large is the AoA (Angle of Attack) in each of these three phases? Is there any difference between the ...
7 votes
2 answers
3k views

Why does the Falcon 9 first stage continue to decelerate after its reentry engine burnout?

As you know, Space X streams its missions and the speed and altitude data of the vehicle is shown. After stage separation, stage one gains speed and accelerates in its decent trajectory till reentry ...
7 votes
1 answer
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How long can the SpaceX Starlink satellites survive before they deorbit?

Like most Low Earth Orbits (LEOs), the satellites will probably eventually have their orbits decay and burn up in the Earth's atmosphere. How long, on average, would this take. I am assuming that ...
3 votes
1 answer
209 views

What would happen during an inflight abort in a Falcon 9 if the booster engines did not shut down?

During the SpaceX'S Crew Dragon In Flight Abort Test on a Falcon 9 Launch System, as soon as the abort system was triggered Falcon 9 booster engines was shut down and crew dragon's super dracos ...
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1 answer
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How many times has SpaceX reused Falcon 9 first stage until 20th May 2022? [closed]

How many times has SpaceX reused Falcon 9 first stage until now? Not about the possibility. I want to know the current progress with the Falcon 9 first stage.
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1 answer
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Does the Merlin vacuum engine on SpaceX's Falcon 9 gimbal?

SpaceX uses the Merlin Vacuum engine on the second stage of the Falcon 9 launch vehicle. Does the merlin vacuum engine gimbal or does the second stage uses only nitrogen cold gas thrusters for ...
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What is the purpose of having a planned hold during a countdown for a rocket launch? [duplicate]

NASA had many with the space shuttle, ULA always had a planned hold at T-4 minutes, and yet other launch providers like SpaceX don't. What is the purpose of a planned hold, and why do some launchers ...
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Why can't the Falcon 9 first stage touch the water? [duplicate]

SpaceX is spending considerable effort to catch the Falcon 9 first stage onto a giant drone ship. I am aware that salt water ruins almost everything in the long run, but the first stage is a composite ...
1 vote
1 answer
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Could Falcon 9 be Caught by the Orbital Launch Tower?

Would it be possible to catch Falcon 9 with the orbital launch tower by its current grid fins or load points that could be added? If they can do this and then remove the landing legs, would mass ...
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1 answer
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What is the reliability of the Merlin engine?

I know that Merlin is extremely reliable, at least over 99%. I do know of one time when one failed, on Falcon 9's fourth launch. SpaceX had used hundreds, if not thousands, of them. I assume there is ...
0 votes
0 answers
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What would happen if a rocket was shot? [duplicate]

After the pre-launch explosion in 2016 of their Falcon 9 rocket, SpaceX seriously considered sabotage, going as far as to see how easy it would be to shoot the Falcon 9 rocket from the ULA building. ...
5 votes
1 answer
101 views

What is the current turnaround time for Vandenberg SLC-4E?

Is there public knowledge for the turnaround time for this Falcon 9 B5 pad?
2 votes
1 answer
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How did this upper stage end up on a collision course with the moon?

The upper stage of the Falcon 9 rocket that launched the DSCOVR spacecraft is expected to accidentally crash into the moon soon. How did it get into this position? I found answers here that say it was,...
5 votes
1 answer
149 views

Has Falcon 9 block 5's design stopped evolving?

Spacex famously iteratively improves the design when developing rockets, with each unit being slightly (or not-so-slightly) better than the previous. These days Spacex seems to be focusing most of ...
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3 votes
2 answers
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Why not first stage rocket recovery at launching site after one orbit?

Rockets first stage recovery at launch site needs a significant amount of fuel for going back. This is why SpaceX most often uses sea platform and booster back burn for re-entry. As we see on Falcon9 ...
3 votes
0 answers
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Is SpaceX on the way to a reliability record? [duplicate]

One of the most striking phenomena of Falcon 9 launches is how smoothly they go, at least for the outside spectator. SpaceX launches a lot. Apparently, they have now had 109 successful missions in a ...
4 votes
1 answer
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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 ...
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1 answer
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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 ...
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1 answer
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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 ...
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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?
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1 answer
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How does 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?
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7 votes
1 answer
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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 ...
4 votes
0 answers
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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 ...
8 votes
1 answer
425 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 ...
4 votes
1 answer
628 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 ...
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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 ...
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22 votes
2 answers
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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 ...
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1 vote
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Why does the signal get lost every single time a Falcon 9 booster or Falcon Heavy booster lands on a droneship? [duplicate]

SpaceX reuses the Falcon 9 boosters and they sometimes fly back from space and land on land or sometimes at sea. In the sea landings, they land the booster on a floating drone ship(mainly, Of Course, ...
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3 votes
1 answer
256 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 ...
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6 votes
0 answers
221 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?
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7 votes
0 answers
126 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
95 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 ...
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5 votes
1 answer
222 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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1 vote
1 answer
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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 ...
2 votes
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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 ...
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2 votes
1 answer
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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 ...
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2 votes
1 answer
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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 ...
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5 votes
1 answer
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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 ...
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2 votes
2 answers
240 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 ...
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3 votes
0 answers
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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 ...
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3 votes
0 answers
124 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 ...
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3 votes
0 answers
117 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,...
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2 votes
1 answer
254 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 ...
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1 vote
1 answer
105 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 ...
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