# Questions tagged [trajectory]

Questions regarding the path that a spacecraft will take due to forces acting on the spacecraft, such as gravitational or radiation from the sun.

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### Obtaining orbital parameters of a closed orbit given the characteristics of the arrival hyperbolic orbit

According to this paper (page 8) by ESA, given the $v_{inf}$, the right-ascension and the declination of the arrival hyperbolic asymptote, it is possbile to find a loci of pericenters of different ...
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### Apogee estimate starting from simplified one-dimensional numerical simulations

I asked a question on pen and paper apogee estimation and got an answer from @tom-spilker that called my attention: He said that he quickly estimated an inclined launch apogee from the results of a 1-...
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### Pen and paper apogee estimation

I have calculated the apogee of a 2.5kN avg. thrust sounding rocket once ignoring drag and then assuming maximum constant (magnitude and direction) drag after burnout. Here are the figures I used in ...
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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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### What is the purpose of eccentric, parabolic and hyperbolic anomaly?

I am currently reading David Vallado's 'Fundamental of Astrodynamics and Applications' and I have this doubt on the 2nd chapter named 'Kepler's Equation and Kepler's Problems'. Although I understand ...
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### How to retrieve MSL EDL trajectory using Javascript and webgeocalc API?

I found a "javascript gateway" to NASA SPICE data, the "webgeocalc" web api: https://wgc2.jpl.nasa.gov:8443/webgeocalc/example/perform-calculation.html It works both online and ...
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### Does the displacement angle change after burnout?

I came across the above image on Nakka's page about fins and what I understood is that rockets will turn into the wind during the thrust phase, and will drift slightly with the wind after burnout. But ...
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### Falcon 9 plot of pitch angle vs time during launch?

I found this super helpful plot of the Saturn V pitch angle vs time during launch: Is there an equivalent plot for a typical (or atypical if must be) Falcon 9 launch?
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### Apsis suffix for object orbiting an exoplanet

Is there already an agreed upon apsis suffix for an object orbiting an exoplanet? I don't think it's super likely that there is, as I don't think any moons have been discovered (or at least not at a ...
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### How do you balance speed and exposure time when trying to reduce heating? [duplicate]

I'm trying to understand how you choose your acceleration/deceleration and trajectory during launch and reentry to minimize aerodynamic heating.* Ignoring efficiency in terms of delta-v (best leave ...
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### Tutorial for orbits from TLE data

I've been looking for a new hobby, and have been reading some about satellite tracking. I was wondering if there was a good tutorial that walks through how to use TLE data. So far I have found ...
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### Would major changes since “Equations of powered rocket ascent and orbit trajectory” was written reduce its applicability?

I was wondering where I can learn how to calculate the trajectory of present day launch vehicles. I've stumbled upon this book, called Equations of powered rocket ascent and orbit trajectory. ...
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### Could the uncertain mass of the OSIRIS-REx sample affect the trajectory of the return capsule?

It appears that so much material was collected by OSIRIS-REx from the asteroid Bennu, that the cover of the collection head won't close, and some of the sample is floating away. In reviewing these ...
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### Is this plot of deep space trajectories correct? Did most launch retrograde from Earth? Why do some change direction between planets?

This answer contains some nice plots of deep space spacecraft trajectories. Noticing that Voyage 2's heliocentric velocity dropped substantially just before 1990 I wanted to see why. Wikipedia's ...
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### Tools for high-thrust trajectory optimization

I've tried using some of the freely available tools for making pork chop plots to explore the potential of transfers between planets. But as far as I can tell, these really are not designed for and do ...
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### How do launch vehicles measure speed during lift off and ascent?

What kind of instruments does a rocket use to track its trajectory and velocity during ascent? Do they use pitot tubes or barometric sensors? What exactly are the instruments used?
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### Has any space probe changed course (in a large way) over time?

I encountered the following text from here: Generally, a spacecraft is launched with huge rockets into a certain trajectory, or path, and it continues on that that path. Often the smaller rockets ...
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### Which deorbit trajectory minimizes reentry heating?

Atmospheric reentry, as I understand it, is a balancing act between minimizing delta-v needed and not burning up or breaking up in the atmosphere. The higher the velocity on reentry, the greater the ...
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### How to choose the best direction to leave Earth's sphere of influence?

What direction is optimal for spacecraft to leave Earth's sphere of influence (SOI) when it's going to an outer or inner planet? Let's presume that we have a spacecraft in a circular LEO (ecc=0.0). ...
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### Dynamics of a vertical launch vehicle trajectory

I have been using NASA's Program to Optimize Simulated Trajectories (POST) for developing a 3 DoF trajectory optimization code for ascent launch vehicle flight to orbit. The dynamics are integrated in ...
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### Find the jump condition of the mass costate of a Launch Vehicle ascent problem solved via an indirect method (Pontryagin Minimum Principle)

I'm trying to solve a trajectory optimization problem for a class of problems like the old Altas-Centaur SLV3 Centaur launch vehicles. Those are a stage and a half design where the 2 LR-87 engines ...
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### Will the Emirate Mars Mission, Tianwen-1 and Mars 2020 Mission get closer to each other or spread out on their way to Mars?

Background & Introduction: On August 2, 2020 the brand new Where Is Roadster page Spacecraft launched to Mars in 2020 (announced here) said that it had been: 13 days, 3 hours, 47 minutes and 13 ...
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### What is the preferred orbital trajectory for a rover/lander to land on a body?

With the new perseverance rover about to launch to mars, I have a question about landers and rover orbital trajectories. Do the landers/rovers circularize their orbit before landing on the body or do ...
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### How long was Sputnik 1's second stage rocket body in orbit? Are there TLEs for it?

Early artificial satellites were tracked by radio and visually by amateurs, scientists and military personnel for various reasons including fun and improving the understanding of orbital dynamics ...
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### Possible idea for a simulation in orbital mechanics using data from the JPL [closed]

I have to write a research essay and have decided to write it on orbital mechanics where I would use data from the JPL to perform an experiment (simulation). I was thinking of using the location data ...
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### How is it possible to connect trajectories at a Poincare section using the “bisection” method?

When constructing a heteroclinic connection (a connection between two different periodic orbits at two different libration points), the stable and unstable manifolds of two different libration points ...
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### Why spacecraft 's trajectory is shown undulating curve on 2D image of earth? [duplicate]

As i am watching live-stream of Demo-2 mission,the trajectory of a capsule is shown curved(like sin wave). In other words, why their trajectory isn't along longitude so that in 2D, the path followed ...
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### How Much Time Did We Have to “Duck and Cover” From an ICBM Launch Only 666 Miles Away? [closed]

During the Cuban Missile crisis I was stationed at Fort Wainwright, Alaska. As it had on many other occasions during the "cold war," our battle group began those infamous, "13 Days" by going on alert. ...
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### Why aren't satellites launched into a Polar LEO to get into Polar Heliocentric Orbit?

The Ulysses Spacecraft was sent to Jupiter to change it's orbital inclination via a gravity assist, and enter a nearly polar heliocentric orbit with an inclination of 79° in respect to the solar plane....
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### Would the trajectory of a comet be altered by attaching a parachute to it?

I am curious to know if the trajectory of a comet that is on a collision course for Earth could be altered by simply attaching a parachute to it. The parachute interacting with the comet's tail should ...
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### How does a space vehicle which carries Curiosity or Spirit rover reach a planet? [closed]

I don't know much science but was curious about it. So, what I've seen in movies is that there are lot of objects in the space and many other space items (made of rocks, moving stars etc.). So when ...
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### Without the accident, would Apollo 13 still have been the farthest crewed mission from the Earth?

This answer notes that the Apollo 13 crew holds the record for the distance that humans have traveled beyond Earth. Had the mission exactly followed the flight plan, would they still have been the ...
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### Did any spacecraft ever use the Sun's gravity for acceleration?

Space probes often use planets to accelerate onto a trajectory towards their goal(s) without having to consume too much fuel. But the fastest acceleration would be made through the Sun's gravity if ...
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### What is the analytical closed-form solution of the two-body problem to verify its numerical integration results?

The purpose is to study the motion of two celestial bodies analytically. What is the closed-form of the two-body problem if I was to solve it analytically without using a numerical approximation ...
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### What ways can a University Student get involved in Trajectory Design?

As a physics student (not an engineer) in India, I can't seem to find a lot of opportunities to involve myself in what I find most appealing about what I'm studying in University i.e. astrodynamics. ...
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I have a need to train a model on various trajectory data of flying objects (for clustering purpose). I found trajectory data of air planes online. But since trajectory data for missiles, satellites ...
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### Why is the bend angle of a hyperbolic trajectory giving different results?

The bend angle ($\delta$) is the reflex angle between the two asymptotes of a hyperbolic trajectory. From this Stack Exchange answer, the formula to calculate the bend angle is:  \delta = 2 \sin^{-...
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### What did I see just before the ISS but on a different trajectory?

I live at 49.99N, 8.57E. Today we had exceptionally clear skies. I was looking out a window towards the South between 7:48pm and 7:52pm local time (central european) when I noticed a strange light ...
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### Why do we prefer using the rotating reference frame rather than the Inertial frame in the three-body problem?

As the title says, I wanted to ask why do we prefer using the rotating reference frame rather than the Inertial frame in the three-body problem to place the primaries? And how is it better for ...
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### Where can I find data on satellite orbits?

I'm an enthusiast who'd like access to satellite orbital data to simulate / plot trajectories of manmade satellites (of any kind) on my home computer. Where's the best place for me to find this kind ...
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### Issue with the Gauss problem for solving interplanetary trajectories

Blue is Earth, Red is Mars, Orange is Jupiter and all the whites are Earth to Mars trajectories. The odd trajectory lines in the middle are the problem I'm trying to solve. As you can see in the ...
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### How is flyby distance estimated?

The New Horizons spacecraft performed flybys of 134340 Pluto and 486958 Arrokoth in 2015 and 2019, respectively. The orbits of these satellites was not known to the kilometer (or maybe even thousand-...
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### Looking for dataset of trajectory data consisting of latitude, longitude, altitude and time

I am working on a project in which I need to cluster trajectories of different type of flying objects like rocket, plane, missile, etc. For that I am looking for a database or data-set which contains ...
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### Two-body problem VS Three-body problem Applications

The two-body problem deals with two bodies under certain assumptions while the restricted three-body problem deals with three bodies where one has a negligible mass (i.e. spacecraft or comet) I was ...
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### Question about orbital mechanics and trajectories for a space infrastructure project/climate adaption idea

I’m working on an alternate approach to the concept of using a solar shield to shade the earth from the Sun (to help with climate change adaptation). It would use streams of lunar soil from multiple ...
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### How should I fix this ill-conditioned trajectory optimization problem (launch vehicle ascent, direct pseudospectral transcription)?

I have a written some trajectory optimization code which can solve the "classic" Delta3 launch to GTO optimization problem in Betts, 2010. It uses direct pseudospectral transcription and so is ...
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### What (the heck) are “space-fixed coordinates” as described in Apollo mission trajectory analyses?

@Ludo's answer to If I wanted to reconstruct an entire Apollo mission's crewed spacecraft trajectories, what are the key sources of historical data I'd look for? shows the table and its source shown ...
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### What do these Apollo era terms mean?

@Ludo's answer to If I wanted to reconstruct an entire Apollo mission's crewed spacecraft trajectories, what are the key sources of historical data I'd look for? links to Apollo Mission 11, ...