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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What is the optimal acceleration for a direct ascent to the moon? [duplicate]

If a rocket flies to any object using a direct ascent it is best for it to reach the needed speed as soon as possible because of the Hohmann effect. When it launches from the ground there is air ...
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Interstellar travel by lightsail – what are the main factors of the trajectory uncertainties?

Lightsail (solar sail or sail accelerated by lasers) is a theorized as realistic way for interstellar travel. Breakthrough Starshot is the most prominent example. Let’s assume we have a thin enough ...
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How does one design a trajectory involving a lunar and Earth flyby and Lagrange points? What tools are used to calculate the initial guesses?

I'm trying to design a trajectory that takes a spacecraft from Sun-Earth L2 to a lunar flyby, to an Earth flyby and then to Mars (two flybys might be too complex, I might just do one). I've optimized ...
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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?
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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 ...
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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 ...
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Manual techniques for trajectory design

I am trying to locate methods of trajectory design that can be performed by hand calculations, specifically for low thrust methods of propulsion like ion thrusters. Can anyone recommend me any ...
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Satellite’s Position and Path on 2D Map

When the ISS orbit the Earth, its path traced on a 2D Mercator Earth Map is similar to a sinusoidal wave. I am wondering is there any way to determine the trig function of the wave, knowing the ...
2 votes
1 answer
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Plot ellipse using elements from TLE

I am trying to draw an ellipse as satellite orbit in three.js, It has an EllipseCurve class which takes these inputs and draws an ellipse around center. EllipseCurve( aX : Float, aY : Float, xRadius : ...
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Earth to Mars Transfer using GMAT

I saw a couple of people mention here that in order to change the epoch date from the given Mars transfer example on GMAT I would need to change and re-optimize initial conditions. How would I do that?...
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I'm trying to create a trajectory to Mars for a low thrust ion thruster engine using astrogator

I'm trying to create an optimize a trajectory to Mars for a number of low thrust high specific impulse engines. I am having trouble with the initial set up. I created a LEO exit spiral using a ...
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Why is my C++ code for an orbit propagator wrong?

I tried making an orbit propagator C++ code. Its values seem to be propagating evenly but still I get a straight line orbit instead of an elliptical one. Why? ...
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Porkchop plots/launch windows for Sun-Earth L2 to Mars transfers?

I've been using Earth-Mars launch windows, found with NASA's Trajectory Browser and EasyPorkchop, as launch windows from the Sun-Earth L2 Lagrange point to Mars, with the logic that since the L2 point ...
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Is there any software or other resources that can find optimal launch windows and gravity assist trajectories involving Lagrange points?

I've been using GMAT to make various trajectories involving the Sun-Earth L2 point. Earth-L2-Mars, Earth-L2-Earth flyby-Mars, etc. However, the main source of optimal launch windows I've been using is ...
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Is there a parameter that describes the angle between the spacecraft's position and the sun angle or direction of the Earth's motion?

I am trying to design an Earth flyby for gravity assist in GMAT, and I know from theory that the spacecraft should pass in front of a planet with regard to its heliocentric direction of motion in ...
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How can Artemis 1 take so much longer for Earth-Lunar transit than the Apollo missions did?

The Artemis I mission will take 8-14 days to get from Earth to the Moon. Apollo 11 only took 3 days. Similarly the return will be 9-19 days for Artemis I and just over 2 days for Apollo 11. Why is the ...
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For launch vehicles, during atmospheric stages, are there constraints on the yaw angle?

Most of the literature discusses the pitch angle and constraints on it, namely, trying to keep it zero for load relief. This leads to the gravity turn. I understand that ideal trajectories are within ...
2 votes
1 answer
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Code to generate Sun-Earth L2 halo orbits for given epoch?

I am working on a GMAT script out of personal interest (not part of a job) that involves a spacecraft orbiting the Sun-Earth L2 point. I have found some orbital state vectors for the spacecraft that ...
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Where is the Wind going? Where has it been? (Global Geospace Science spacecraft 1994-071A)

This excellent answer to Why put DSCOVR in a Lissajous orbit? Wouldn't a halo orbit completely avoid the Sun exclusion zone? explains that the Global Geospace Science or Wind spacecraft ...
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Mission maneuver to Enceladus, I have some results from JPL trajectory browser, what comes next?

I am working on a project titled 'Astrodynamic mission maneuver to Enceladus'. I have found the launch date using NASA trajectory Browser. Can you let me know how to proceed further?
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How can I find the x, y position of apogee and perigee, if I only have the value of distance vector (position) and velocity vector?

I am currently working on a 2D space simulator where I have two bodies; one is still and other is an orbiting object, which I can also control like a rocket. I'm using the Newton's gravity: $F = \...
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Are Interplanetary mission trajectory computations based entirely on Newtonian mechanics?

I am wondering if the application of General Relativity is ever needed(?) I assume that Newtonian mechanics is sufficient with some trajectory corrections applied as needed on route. I also assume ...
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How can I find the old reference orbit for JWST (from 2014) and get AltAz positions from Earth without learning Spice? Can Horizons do it? Can Python?

In this ancient 2017 answer to What happens to JWST after it runs out of propellant? I've plotted an eleven year long reference orbit for JWST that was available form Horizons at the time. Now that ...
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Why are all trajectories in space a conic sections?

All trajectories available in space: circle, ellipse, parabola, hyperbola, straight line are parts of cone. Why? Does the spacetime have a conic shape?
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How to calculate an initial impulse for escape from planet's sphere of influence and lay on a specific orbit around the Sun?

I have a spacecraft parked on orbit around the planet. I want to make interplanetary transfer to another planet. I can find the orbit around the Sun that I can use to move from the end of departure ...
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How to propagate the trajectory in GMAT with a custom thrust profile

So basically I was trying to design a low thrust maneuver to increase the apogee of the spacecraft. I solved it separately and got some thrust profile (thrust and it's direction as a function of time)....
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When was Lucy's mission first scripted in Excel and why is that what Lockheed Martin chose to do it with?

CNBC's NASA spacecraft launches toward Jupiter asteroids on an intricate path charted by Excel Years before Lucy took off, Lockheed Martin mission architect Brian Sutter used Excel to chart the ...
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Dragon re-entry flight profile?

I was looking online for a profile depicting the Dragon re-entry similar to those showing the launch and first stage re-entry (e.g. https://www.elonx.net/wp-content/uploads/...
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What is the numerical procedure to find the next closest approach between two bodies on keplerian orbits?

Given two bodies on Keplerian orbits, what is the procedure to find the next closest approach of the two bodies? The bodies would be effectively massless objects like two spaceships orbiting around a ...
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What happened to the launch debris that the US dropped on Cuba? Was it noticed or reported?

This answer to How does one dogleg from Florida to a sun-synchronous orbit? this answer to History of multiple-payload launches? both describe a launch of GRAB1 that secretly contained a second ...
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Calculating the time of flight between two anomalies gives a negative result?

I want to calculate the time of flight (TOF) between two true anomalies on an orbit with known orbital elements. Based on this wikipedia article and the post Time of flight between two anomalies in a ...
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What would be the trajectory and initial speed of a chunk launched from Phobos to get as close as possible to any pole of Mars?

Credit: NASA / JPL-Caltech / University of Arizona Phobos has a nearly circular orbit almost parallel with the equator of Mars. It orbits the planet in only 7h.39 min. at a height of 6000 km above the ...
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Journey to the center of the Sun (best trajectory)

Let's assume there is unlimitedly rich eccentric person living nowadays, who has been just diagnosed with a kind of terminal cancer (estimates are 3 years left) and their last wish is to jump into a ...
3 votes
1 answer
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How were winds measured for ascent trajectory calculations and checks for the Space Shuttle?

The Space Shuttle's ascent trajectory was calculated on the day of launch based on measured winds to avoid structural load exceedances. The winds continued to be measured until shortly before launch ...
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Why does the landing trajectory of a blunt body take an S shape in the lower atmosphere?

I coded some Matlab plots of altitude vs time for the re-entry of a point mass (so no aerothermo analysis included). In all the trajectories, there is an S shape closer to the ground. Why? Please ...
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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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3 votes
1 answer
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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 ...
4 votes
1 answer
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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. ...
6 votes
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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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