# Tag Info

## Hot answers tagged launch-trajectories

37

I understand the reasons behind each of this manouveurs, however I'm wondering if this is how real rockets get into orbit. Cutting off the engine and letting the rocket loose vertical speed looks counter-intuitive to me (you basically spend a lot of fuel to accelerate and then you let the rocket slow down). In most real launches to low Earth orbit, the burn ...

33

Physics In regards to the physics, KSP is fairly realistic, other than it not modeling n-body physics (which isn't really relevant in scope of orbiting Earth/Kerbin). In regards to the engineering, KSP makes its parts much stronger than the real life components. The tradeoff here is that when something finally breaks in KSP, it explodes and disappears. ...

18

It's real, although many rockets heading to low orbit are engineered such that when the apoapsis reaches the desired altitude it's time to begin the final burn. Remember that orbit is not truly zero gravity no matter how many times Hollywood calls it that. Rather, it's free fall--craft in low orbit fall towards Earth just about as fast as they would here ...

12

As ISRO launches from SHAR towards Bay of Bengal, they don't have much of launch azimuth, which is limited (can't recall the exact value). Whereas NASA and Rocketlab have pretty good launch azimuth range. So to launch PSLVs from SHAR, they use lower launch azimuth and then they do a dogleg maneuver to use the required launch azimuth.

11

What was the duration of the launch window this day? According to Spacelaunchnow, the daily launch window was instantaneous, but there were daily opportunities from July 15 to August 12. Did it first enter a short period of LEO for phasing and/or staging, or did it launch directly into its interplanetary trajectory? From the timeline, it appears that it ...

11

If the optimal speed is terminal velocity, this is the formula you need: $V_t= \sqrt{\frac{2mg}{\rho A C_d }}$ where - $V_t$ is terminal velocity, - $m$ is the mass of the falling object, - $g$ is the Earth's gravity|acceleration due to gravity, - $C_d$ is the drag coefficient, - $\rho$ is the density of the fluid through which the object is falling, ...

10

Due to range safety requirements, which preclude launch trajectories that fly over populated areas, the maximum inclination by a standard launch from CCAFS/KSC is approximately 57 degrees. There was one mission, however, that exceeded that. STS-36, a classified shuttle mission, was launched to an inclination of 62 degrees, through the use of a "dog-leg" ...

7

To revisit this question, it does appear that the during the 1950s & 1960s, a number of extreme inclination and polar launches did indeed take place from Cape Canaveral in Florida. The range safety limitations placed on launches from Florida was only enacted after a number of polar launches had already taken a place (possibly for good reason at the time ...

7

Yes, in very broad terms this is how real spacecraft enter orbit. The maneouver is called a gravity turn, albeit KSP encourages (very) inefficient versions of it, just because it's faster (in terms of ground-to-orbit-time) and more fun (in terms of waiting-for-something-to-happen-time) to add more boosters and raise your apoapsis faster. An efficient gravity ...

7

The short answer to your question is GNC (Guidance, Navigation & Control). Mission planning is done based on nominal (normal) performance of all systems launched through a mean atmosphere for the time of year when launch will take place. Depending on how many prior flights have taken place and how much data is available to model a specific vehicle launch ...

6

“Sailing a rhumb line” means holding a constant compass bearing. For short distances, this stays close to a great circle path.But at longer distances and/or higher inclinations, the rhumb-line path “tends north” of a great circle as shown in the Questions globular image. For a fast, short launch, a rhumb-line trajectory has the advantage of simplicity. As ...

6

Currently, NORAD and others use large radar arrays to keep track of objects. Simplified trajectories are what appear in the common TLE databases. Conjunction analysis is done by propagating the trajectories of these objects. There are many types of model used here, but broadly speaking they model the conjunction of large error boxes (ellipsoidal or ...

6

Given some simplifying assumptions (constant thrust, constant gravitational field, flying in vacuum, over flat horizontal surface), which aren't too badly undermined by the lunar ascent case, the linear tangent steering law is known to give optimal orbital insertion: $$\tan \theta = A \cdot t + B$$ i.e. the tangent of the thrust pitch angle changes ...

6

That section of the Wikipedia article is very poorly written, conflating interplanetary gravity assist in one case with gravity turns (prior to my ruthless edit), and should be in no way considered comprehensive, nor as a serious indication that gravity turns weren't used prior to Apollo. The early crewed missions (Vostok and Mercury) were flown on ...

5

You can think about it (approximately) by dividing the rocket trajectory into "up" and "downrange" parts. The "downrange" part is the largest one: To get to orbit, the rocket has to generate a lot of speed in that direction. The "up" part is quite different. To end up in a low, circular orbit, the rocket has to go "up" few hundred kilometers and stop. ...

5

The 'coast' is a very natural part of getting to orbit. Burning close to the planet's surface saves the total amount you have to change your velocity by. The mechanics are a tad complex but the short version is you get more energy by changing your velocity when you are going faster. As you lose speed while you ascend, its best to do all of the burning you ...

5

The Antares will have a long coast phase due to engineering related trade offs rather than orbital-mechanical advantages. However from an an orbital-mechanical view alone, there would always be a long coast phase. Ignoring the atmosphere and engineering limitations, you would apply all your "first stage" impulse as close to instantaneously as possible to ...

4

This plot shows the pitch profile for a Saturn V from launch to Earth Parking Orbit and it's described like this: The vehicle rises nearly vertically from the pad, for approximately 450 feet, to clear the tower. During this period, a yaw maneuver is executed to provide tower clearance in the event of adverse wind conditions, deviation from nominal flight ...

3

welcome to Space Stack Exchange. I'm going to take a guess that you mean "how can I determine the direction prior to the event?". Go to the launch providers website and see what advance information they give as a press kit. It may well not give anything obvious, but have a look at the inclination of the target orbit. The rest of this answer ...

3

Looking at Zarya, which lists all attempted launches and the orbits of all successful launches, there was never a successful launch from Canaveral to polar orbit. The highest inclination I saw was the Transit 2A, which had a 67 degree inclination. It seems likely the cow killing incident was the Transit 3A, presumably which would have been launched in to a ...

3

However, it is not so based on the above preliminaries, what might be the cause for this? The linked paper does give a reason: "These specialized options are required to simulate certain physical constraints that are not modeled in the equations of motion." The physical constraint in the case of a vertical launch is very simple: The launch vehicle ...

2

The pre-1.0 version of Kerbal Space Program had a very bad aerodynamic model, that the correct rule of thumb was to keep things near the terminal velocity, otherwise you ran the risk of being significantly decreased. The later versions increased the fidelity to something more akin to what is seen. Keeping your speed under control while in the atmosphere is ...

2

Based on this document the maximum inclination possible is 37 degrees (from north) and the minimum is 114 degrees (from north). I don't know if how close any mission got to the limits, but most polar launches occur from Vandenberg

2

That is how real rockets go into orbit, and for orbit you need to lose vertical speed or it would be a spiral. Orbit is about horizontal speed though not vertical.

2

In fact it could be arbitrarily low. But wait before you rejoice. The Moon has an elliptic trajectory. This elliptic motion perturbs any orbit of a satellite in LEO. If you first assume your satellite is in the same plane as the Moon and describe the system as a time dependent Hamiltonian system with two degrees of freedom, a process called Arnold diffusion ...

2

While the length of a launch window varies, launches within the window typically occur at discrete times - typically "launch on minute" or "launch on second". Often a common earth-relative trajectory is used for the entire window (or subsections thereof), and rotated to the correct inertial trajectory for each expected discrete launch time. Once you have ...

2

In theory, a rocket could "follow a rhumb line" starting with any kind of directional information. But there seem to be two use cases: The very-early Pegasus rockets used a directional gyro derived from an aircraft gyrocompass, perhaps due to their aircraft parentage. This was later updated to a full IMU, eventually augmented to GPS. Another approach is ...

2

Bob's answer seems correct and covers the legal aspect, but it might be useful to note from an engineering point of view the conclusion is also correct. In particular that even when things go well: booster stages fall out of the sky, is only part of the issue. If it was all of it, we could have solved the problem already anyway. For example, its not super ...

2

The FAA, by rule, requires an exclusion for any air space over which a rocket is flying with its Flight Termination System armed. I guess they consider that the FTS might actually be used, in which case rocket pieces may be traveling in an uncontrolled way. Since Falcon 9’s 2nd stage FTS isn’t safed until well after stage separation, I think that’s enough to ...

2

Earth Satellites: get TLEs from Celestrak or Space-Track and propagate them with SGP4. One way to do that and to also calculate their ground tracks (latitude and longitude) is the Python package Skyfield but there may be others. However I'm not aware of proper databases that you can download constantly updated positions already calculated each second. Things ...

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