Questions tagged [launch-sequence]

Questions regarding the steps and procedures taken prior and during the launch of a space vehicle.

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46 votes
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Why did the JWST solar array deploy early?

According to NASA's Deployment Explorer tool, the solar array was expected to deploy at T+33 minutes. In the NASA livestream, the solar array deploys at T+29:08 (the clock isn't on stream at that ...
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5 votes
1 answer
216 views

Space shuttle MECO condition: velocity threshold or fuel level?

I've read in a place I can no longer remember that MECO would happen when fuel is depleted or, if the separating stage is returning, when fuel reaches some preset threshold---15%, say. But now... ...
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2 votes
2 answers
140 views

Which orbital elements are normally targeted at launch?

Say you launch a rocket for rendezvous with the ISS. You'll want to set the target orbital inclination and longitude of ascending node. These will ensure the rocket is in the plane of the ISS. You'll ...
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1 vote
0 answers
83 views

What happens at T-0 for the SpaceX Starship?

Every launch system defines a different event for T-0. The SpaceX Starship prototypes seem to ignite the engines at T-1.0 and accent seems to begin between T+1.0 and T+1.5. An overthrust abort for SN-...
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2 votes
0 answers
66 views

What do the double- or triple-checkers do when a launch is not scheduled?

Leading up to every manned launch, there is personnel dedicated to making sure their colleagues do everything correctly in accordance to checklists they usually have on hand. See for example the ...
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4 votes
2 answers
456 views

Who uses a countdown, and who doesn't?

I just learned that the Russians don't use a countdown when launching a rocket. I saw that in a YouTube video and found a Reddit discussion that confirms it. That makes me wonder who does and who ...
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2 votes
1 answer
206 views

Would the space shuttle do a yaw maneuver to avoid the tower?

I read some rockets do a small yaw maneuver of about a degree immediately after T0 to avoid the tower in case of wind gusts. Would the space shuttle ever do such a maneuver? Did it? I read also that ...
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3 votes
1 answer
166 views

Are westward launches more expensive than eastward launches?

Basic question for those who breathe rockets: The earth's rotation imparts to the rocket a free delta V of roughly 450 m/s if you launch straight eastward. If you launch westward instead, for a ...
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0 votes
1 answer
374 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 ...
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1 vote
0 answers
64 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 ...
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0 votes
1 answer
72 views

Estimating time to engine cutoff?

I'd like to calculate the approximate time left to my stage-1 velocity target. A simple way to do this would be to divide my Delta V by my acceleration. Trouble is... my acceleration changes ...
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2 votes
0 answers
29 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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4 votes
1 answer
367 views

Simple alternative to Powered Explicit Guidance for orbital insertion?

Say you're playing space ops engineer and want to simulate an orbital insertion---but you're petrified by the calculations needed to get the coefficients of the linear tangent law behind Powered ...
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4 votes
1 answer
202 views

Are Powered Explicit Guidance calculations done before or during launch?

Space shuttle orbital insertion was done using a powered explicit guidance algorithm. At the surface, the algorithm is simple, as it gives the instantaneous pitch as a linear function of time: $\phi = ...
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10 votes
3 answers
2k views

How much throttleback to keep acceleration under 3g?

Most rockets generally throttle back when they reach max-q to prevent structural failure. This could be the only throttleback event of the launch. But crewed rockets normally do a second throttleback ...
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2 votes
0 answers
33 views

Antares yaw maneuver: how many degrees?

The Antares rocket begins launch with a very noticeable yaw maneuver that seems to rotate it more than the 1.25 degrees documented for the Saturn V. Am I being misled by perspective? Does anyone know ...
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3 votes
1 answer
217 views

Why does SpaceX Crew Dragon not have planned holds?

I watched the launches of SpaceX Crew Demo 2 and Crew 1. I observed that there were no planned holds during the last hour of the countdown. The Space Shuttle had planned holds at T-20 minutes and T-9 ...
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5 votes
2 answers
147 views

Apollo prelaunch timeline?

I'm looking for a resource that will tell me all the important pre-launch events of an Apollo mission from when the rocket rolls out of the VAB to liftoff. Specifically, I'm interested in the Apollo 8 ...
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0 votes
1 answer
154 views

At what time is the Falcon 9 loaded with fuel?

How long before launch are the fuel and oxidizer loaded into a Falcon 9 rocket? And how much time does it take to load it?
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8 votes
1 answer
928 views

What does "all systems are internal" mean?

When watching (once again) a large History Channel documentary series about Gemini and Apollo, in some launch scenes with the original audio, the person doing the countdown usually says "all ...
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7 votes
0 answers
932 views

Why were the SpaceX ninjas (pad crew) using a stepladder to move something?

On the second launch attempt of the Dragon Crew Demo 2 (human spaceflight), sometime lower than 1:50:00 to launch, the ninjas spend about 5 minutes on a stepladder, dealing with a tube and box, which ...
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  • 844
8 votes
1 answer
2k views

Why the long (19 hour) mission profile for SpaceX's trip to ISS?

As mentioned briefly in this question, The Russian Soyuz has been using a sub-4 hour path to ISS. Why the long ride from Canaveral? Or is the 19-hour timeframe typical of all launches prior to the "...
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4 votes
1 answer
239 views

Are rocket tanks being filled up until the last seconds before liftoff?

In rocket launch videos, we often observe liquid propellant rocket engines running at full thrust for several seconds before actual liftoff. We understand that liquid propellant rockets consume a ...
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11 votes
1 answer
2k views

How (and when) was the RTG in the lunar modules installed?

In this answer, it is explained that the space probes RTG's are not installed until a couple days before launch because of the heat those things generate. Now I'm curious about the Apollo RTGs. From ...
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1 vote
2 answers
210 views

What are these Soyuz Astronauts/Cosmonauts holding in their hands before launch? [duplicate]

What are these Soyuz Astronauts/Cosmonauts holding in their left hands before launch? I suspect it must be the pump for the active cooling system by pumping water similar to those in EVA suits, but it ...
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42 votes
1 answer
6k views

Was the payload bay of the Space Shuttle depressurized before launch?

We know that the payload bay of the Space Shuttle Orbiter carried satellites, pieces of equipment for repairing satellites and components of the International Space Station. Was the payload bay of ...
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4 votes
1 answer
771 views

Why doesn't Ariane-5 lift off at T=0 seconds?

I have seen Ariane-5 lift off at T+07 seconds and not at (or close to) T=00 seconds. The following statement is from the Ariane-5 User's Manual (Page 35, Section 2.3 - Typical Mission Profile): The ...
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21 votes
1 answer
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 ...
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15 votes
1 answer
791 views

How were the pins for Saturn V controlled release tested?

I came across the following section of the Saturn V Flight Manual (pdf): The intriguing part is that they used 12 pins to actually bolt down the Saturn V to the launch pad and the combined engine ...
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2 votes
2 answers
579 views

What event determined the transfer of control from Kennedy Space Center to Houston?

Launches at Kennedy Space Center in Florida were managed by the on-site launch control center. At some point in the mission, authority was transferred to the mission control center in Houston, Texas. ...
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14 votes
1 answer
2k views

What exactly is the purpose of connection links strapped between the rocket and the launch pad

I am curious on what are those multiple connection cables latched between the rocket and launch pad. What exactly is the purpose of it, I am aware that one should be for filling up the fuel. But ...
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4 votes
1 answer
710 views

Why should the roll program position the shuttle's nose to the east?

The roll program occurred during a shuttle launch for the following reasons: (...) Orienting the shuttle more parallel toward the ground with the nose to the east. ...
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1 vote
0 answers
172 views

Launch corridors

I was wondering where I could find a list of the launch azimuth ranges - i.e. the corridors - for the main launchpads worldwide (Baikonur, Kourou, KSC, ... as many as possible). Thank you in advance!
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5 votes
1 answer
367 views

What caused launch abort on SpaceX's Bangabandhu-1 launch

On Thursday, May 10th, 2018, SpaceX attempted a launch of the first Falcon 9 block V rocket carrying Bangabandhu-1 however the countdown was stopped at t-58 seconds and the launch was scrubbed for 24 ...
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5 votes
3 answers
2k views

How was the Centaur stage fueled in the Space Shuttle?

The Space Shuttle had the ability to launch Centaur booster stages stored inside of the Shuttle during launch. How was this stage fueled, being fueled with cryogenic fuels?
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  • 118k
3 votes
1 answer
188 views

Fuel-optimal thrust profile for an orbital ascent on a planet with an atmosphere

This is a continuation of a previous question posted a few months ago. If we consider a SSTO vehicle launching from a planet with an atmosphere, would it be fuel optimal to have a period of lowered ...
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2 votes
0 answers
216 views

Databases of "scrubbed" launch attempts?

I'm curious if there is a statistically demonstrable tendency not to schedule launches on certain days, such as those that contain leap seconds (see answers below this question), year changes, or ...
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  • 148k
2 votes
0 answers
83 views

Is there an authoritative catalog for rocket launch identifiers?

For satellites there's NSSDCA/COSPAR, but I'm unable to find something similar for the launches of those objects. I'm hoping I'm not looking for something that doesn't exist as I'm assuming launch ...
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6 votes
1 answer
806 views

Preflighting TVC actuators on Falcon 9

It is my understanding that the Falcon 9 thrust vector control (TVC) actuators use RP-1 as hydraulic fluid and use the fuel turbopump energy to drive the hydraulic pump for the TVC. How do you do a ...
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  • 89
16 votes
3 answers
6k views

Were the Space Shuttle's Main Engines ever off while the Solid Rocket Boosters were firing?

I always though the Space Shuttle needed a combination of its solid rocket boosters and its main engines to remain stable while launching. The following diagram found on Wikipedia seems to agree: ...
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  • 261
3 votes
1 answer
147 views

Why will the RP-1 loading for SpaceX's Iridium-1 mission begin at T-00:70:00 as opposed to T-01:10:00?

Why will the RP-1 loading for SpaceX's Iridium-1 mission begin at T -00:70:00 - wouldn't it usually be written as T -01:10:00? $...
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  • 148k
39 votes
4 answers
10k views

What "actually" happens at T-minus-0

In most American rocket launches, the "counter" will say: 3,2,1 [awkward pause], and liftoff.... So what truly happens at T-0? Is there any standardized event that this time indicates? Is the ...
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  • 1,685
1 vote
0 answers
120 views

What is the sequence of the main spacecraft and CubeSats separation during Falcon 9 launch?

I'm curious about timeline and the procedures related to the spacecraft separation during Falcon 9 (and perhaps other rockets if such information is available) launch. Let's assume a mission with one ...
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4 votes
1 answer
230 views

What does CLG INIT mean?

During India's PSLV-C35 launch on 26 September 2016, mission control's launch sequence events (stage separations, stage ignitions, etc.) included 'CLG INIT'. What does it mean?
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6 votes
2 answers
711 views

How can the elements involved in loading a LOX tank be involved in an explosion?

Since SpaceX has isolated the AMOS-6 Falcon 9 pad explosion to the upper stage LOX tank during fueling, it seems useful to consider in general terms what was happening at the time and what materials ...
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  • 20.8k
4 votes
1 answer
2k views

What is the advantage of doing a static test fire before launch?

Continuing the series of questions (part 1, part 2) inspired by the recent loss of the AMOS-6 satellite during a static test fire, here's one thing that puzzles me a bit: What kinds of problems is a ...
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16 votes
2 answers
3k views

In the Saturn V launch sequence, what defined COMMIT, and what happened between COMMIT and LIFTOFF?

With the Saturn V, there were two critical moments during launch that I am curious about: The vehicle COMMITs to liftoff The vehicle LIFTS OFF LIFTOFF is fairly obvious: the booster has risen some ...
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  • 7,186
2 votes
2 answers
885 views

What is behind Dragon's Guidance, Navigation and Control bay door?

The timeline in the press kit for the upcoming CRS-9 SpaceX launch says at about 11 minutes after launch, "Dragon's solar arrays deploy", and at 2 hours 19 minutes, "Dragon's Guidance, Navigation and ...
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  • 148k
10 votes
3 answers
1k views

What's the first recorded use of a countdown associated with a rocket launch?

Counting down the seconds leading up to a rocket launch is iconic - certainly it seems that every child knows that after "5, 4, 3, 2, 1" comes "Blast off!" However, the countdown can't always have ...
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  • 1,334
3 votes
1 answer
251 views

LV Telemetry links on the launch pad

Are electronic telemetry and control links (of TT&C - telemetry, tracking and control) to the launch vehicle incorporated into the launch pad umbilical lines and handed off at launch, or is it all ...
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