Questions tagged [launch]

Questions regarding the takeoff or the liftoff phase of the flight of a rocket and the set of activities required for preparation of the launch vehicle leading to it.

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1answer
65 views

Terminal velocity on reentry?

I've seen many references to "terminal velocity" on reentry, e.g., prior to a Falcon 9 landing burn. And I'm confused by this. Because terminal velocity comes from drag which depends closely ...
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Falcon 9 flipover duration

This launch video shows a very gradual stage-1 flipover. The flipover starts right after MECO, before the 3:00 mark, and it continues slowly until just after the 6:00 mark. Or that's the impression I ...
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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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2answers
431 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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29 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?
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3g Throttling: Does Falcon 9 kill engines if acceleration over 3G?

I'm simulating a launch and I often hit minimum throttle before I hit MECO (triggered at 15% fuel mass---my reserve for stage-1 reentry). Acceleration then begins to rise to maybe 3.3 g by the time ...
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Why the repeated downvotes on fine questions? [migrated]

I fully expect this to be deleted in 10 seconds flat. That's OK. I've noticed various people are downvoting perfectly fine questions for no apparent reason whatsoever. Worse, they don't bother to say ...
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SN11 was launched in fog. Why not wait for better conditions?

The fog certainly frustrated the external observers, but it doesn't seem ideal from SpaceX perspective either. All the external observers were very distant from the launch/landing site and would be ...
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0answers
34 views

How much of NASA's annual budget goes to launch

I've been trying to figure out how much of NASA's budget goes to launch costs. I would also be interested in the same question for the global space market. What I've tried I started with a simple ...
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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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48 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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1answer
29 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 ...
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1answer
95 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 ...
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2answers
103 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 ...
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3answers
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How do cubesat owners first find out their cubesat's initial trajectory? How do they point antennas at it before official TLEs start to appear?

When cubesats are first deployed it can sometimes take several days before they start appearing in official TLE distributions, and even then if many were deployed it may take a lot more work to decide ...
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1answer
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Space shuttle PEG ascent burns

I'm reading a public document on the powered explicit guidance algorithm used in the space shuttle. The document suggests that PEG ascent maneuvers always involved at least three phases: Constant ...
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1answer
149 views

Is it possible to launch a rocket with steam by using a fission reactor?

The idea is to use a fission reactor to turn water into steam pumping it outside the reaction chamber through heat pipes.
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1answer
1k views

Rocket launch: closed vs. open loop?

I've seen many comments that pitchover and gravity turn are "open loop" and that powered explicit guidance (PEG) leading up to orbital insertion are "closed loop." And this has me ...
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1answer
91 views

SpaceX launch simulation software?

Say you're a SpaceX launch engineer. You have a mission design meeting where you'll talk about different mission scenarios. The meeting is in a few hours. Would you run a quick simulation in KSP to ...
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31 views

How to calculate launch window?

Say I want to launch a rocket in the next 5 days for rendezvous with the ISS. I need to figure out when the orbital plane of the ISS will intersect my launch site---e.g., Kennedy. The orbital plane is ...
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1answer
41 views

Attitude control with cold gas thrusters

Consider the cold gas thrusters on a Falcon 9. There are two thruster pods on stage 1 and two on stage 2. Each pod has four orifices to fire along the x, y, and z axes of the scacecraft. By varying ...
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32 views

Reasonable argument of periapsis?

My intuition for orbital parameters is still poor, so I'm wondering if someone can tell if my argument of periapsis seems reasonable. I'm simulating a launch from Kennedy (28.1 deg latitude, -80.6 deg ...
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37 views

Orbit design guidelines for rendezvous with ISS?

Are there guidelines for orbit design if you're launching a payload for delivery to the ISS? Altitude, maybe phase angle constraints? Orbital approach maneuvers, maybe? I've figured out how to control ...
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30 views

Mount Lightband with Screws into Helicoils?

Quick question; provided sufficient rigidity and accommodation for tear out in the underlying structure, can you fasten a Planetary Systems Motorized (or Advanced) Mark 2 lightband ESPA interface with ...
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37 views

Entering elliptical orbit at periapse

Consider a rocket entering an elliptical orbit from launch. Say you want the rocket to enter exactly at periapse---not a few degrees ahead of it, not a few degrees behind it. Can this be done? I have ...
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22 views

Setting argument of perigee at orbital insertion?

I've managed to control for altitude, velocity, eccentricity (via flight path angle), orbital inclination, and longitude of ascending node at orbital insertion. Between them, these parameters uniquely ...
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1answer
223 views

Perigee location?

Suppose I throw a ball eastward from Kennedy and reduce the earth to a point so that the ball can trace an ellipse around it. Because I threw the ball eastward (no vertical or northern velocity ...
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2answers
78 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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1answer
125 views

Powered Explicit Guidance: Should rocket be pitching down at orbital insertion?

I simulated an orbital insertion using Powered Explicit Guidance as used in the space shuttle. The PEG algorithm works great. I hit all my targets: altitude, velocity, orbital inclination, longitude ...
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40 views

Will i be able to see the SpaceX tonight launch from Ocala, Fl?

Im currently in Ocala, FL and SpaceX launches a rocket tonight (March 9th) from Cape Canaveral. Will I be able to see it given the proper conditions?
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2answers
489 views

How much does smallsat launch to LEO cost?

In early 2021, SpaceX, Rocket Lab, and Virgin Orbit list prices as follows: ...
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1answer
102 views

Why might particulate matter be shaken loose during Crew Dragon Demo-1 launch?

Here is the picture of Expedition 58 crew members enter the Dragon 2 of Crew Dragon Demo-1 for the first time. They are wearing protective gear to avoid breathing particulate matter that may have ...
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5answers
976 views

Earth Launch System with Water Propellant

Water based thrusters have been proposed (and possibly tested by now) for use in satellites and other in-space vehicles - see this NASA article. The idea is to perform electrolysis on the water to ...
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120 views

If I were to launch an rocket from the top of the troposphere, how much fuel would it save compared to launching it from sea level?

Let's say we have some kind of rockoon design where our rocket gets carried 20 kilometers up before it finally launches from its balloon/blimp platform. Would that maneuver save a significant amount ...
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1answer
144 views

Why don't silo-launched Minuteman missiles incinerate themselves at launch?

Whilst cobbling together an answer for this question, I found myself thinking about the effects of hot rocket exhaust on a rocket launching from a confined space. I assumed it would be generally ...
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2answers
124 views

launch rocket like bullet from steam/air rifle?

I've included an image depicting how exhaust energy from a rocket launch can be recouped by turning it into a large scale pressure cooker by the use of some kind of platform=sabot (thanks @...
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2answers
2k views

Do astronauts wear G-Suits during the launch?

Nowadays, rocket launches (to the ISS) accelerate astronauts at a maximum of around 3 to 4g (source). I have seen quite a few ...
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39 views

Detailed description of space shuttle major and minor GNC loops

Warning: repetitive question ahead. Please skip if you're tired of splitting hairs on these things. Is there a detailed description of the major and minor GNC loops of the space shuttle? I've learned ...
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1answer
69 views

Noninertial effects a problem in strapdown IMUs?

Unlike stable-platform IMUs, which are fixed in space and therefore inertial, strapdown IMUs are fixed to the vehicle's body and therefore noninertial. Would noninertial effects distort the strapdown ...
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2answers
96 views

Space shuttle state propagation---constant acceleration during cycle?

The space shuttle used a state propagation algorithm to estimate the current state vector when new data weren't yet available from the navigation system (which would come at a rate of only 0.25 or 0.5 ...
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1answer
93 views

Was space shuttle position corrected for before orbital insertion?

The space shuttle derived its attitude and state vector primarily from its integrating accelerometers and rate gyros. Data from the accelerometers and rate gyros came in at a low rate (0.25-0.5 Hz, or ...
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1answer
58 views

Space shuttle state propagation

Space shuttle training manuals say the GNC system obtains state information from the IMU platform at a low rate (0.25-0.5Hz) and that state propagation algorithms estimate the vehicle's state vector ...
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3answers
6k views

Why do Space X starship launches need permission from the FAA?

For Flight #7 slated for 02-Feb-2021, Wikipedia's SpaceX Starship; Testing Program says: SpaceX attempted to fly SN9 on 28 and 29 of January 2021, but failed to receive permission from the FAA. (164, ...
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1answer
78 views

Launch azimuth from orbital inclination WRT rotating earth?

The formula for launch azimuth given latitude and target orbital inclination goes like this: $$azm = \sin^{-1} \left(\frac{\cos(inc)}{\cos(lat)}\right)$$ I assume the orbital inclination $inc$ and ...
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50 views

How long to reach final orbital inclination?

Consider a rocket launch from Kennedy, latitude 28.5 deg, to a target orbital inclination of 50.6 degrees for rendezvous with the ISS. The launch azimuth for this orbital inclination is roughly 45 deg ...
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1answer
54 views

Space shuttle Initial ADI frame Before Switch to LVLH?

The space shuttle crew switched the ADI frame to LVLH as soon as the roll maneuver was completed. They waited for that time because the LVLH frame is in mathematical gimbal lock (singularity) when ...
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53 views

Why would a launch request for a gravitational assist at Mars specify a DLA (Declination of Launch Asymptote) of 30 to 32 degrees?

The recent intriguing question Why is NASA proposing an EMEJ (MEGA) trajectory for Europa Clipper instead of EEJ? quotes "A launch service request... recently put out for Europa Clipper to do a ...
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2answers
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Why is NASA proposing an EMEJ (MEGA) trajectory for Europa Clipper instead of EEJ?

A launch service request was recently put out for Europa Clipper to do a flyby of Mars on its way to Jupiter. How is that a better trajectory than an EEJ, similar to Juno? Launch Vehicle Performance: ...
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1answer
50 views

Which reference frame for space shuttle PEG orbital insertion?

Which frame were the space shuttle's orbital insertion attitude targets specified in? The shuttle had three frame choices: LVLH, INRTL, and REF (an inertial frame whose attitude the crew could lock in ...
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Why no yaw in ADI when LVLH is selected?

The space shuttle would display the spacecraft's attitude in one of three frames: LVLH, REF, or INRTL. Launch procedures called for LVLH to be selected very early in launch. The attitude indicator ...

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