Questions tagged [orbital-mechanics]

Orbital mechanics or astrodynamics is the application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft. For the movements of celestial bodies, see [celestial-mechanics].

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How presise could 2 satellites "thread the needle" in orbit?

I have a question about using a magnetic field to propel 2 satellites off each other while traveling in opposite directions on the same orbital plain to intersect either 2:1 or 1:1 on each orbit ...
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103 views

Why might NASA need to "practice moving a spaceship in different orbits in deep space"?

The NASA.gov feature Q&A: NASA’s New Spaceship says Q: NASA’s really building a spaceship?! A: That’s right! NASA is working with its partners to design and develop a small spaceship that will ...
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232 views

Spacecraft-fixed coordinate system

I am working with data from a polar-orbiting satellite (inclination 97 degrees) with limited attitude information. I am trying to define a coordinate system which is fixed with respect to the ...
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94 views

Difference between approach maneuvers to the insertion points of halo and Lissajous orbit?

I have read that spacecraft use two mid-course corrections to approach the Lagrange point, then do a final orbital insertion maneuver to enter into a halo orbit. Are there any specifics about this ...
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What is the importance of thrust control history in low-thrust optimization?

As I have mentioned before, I am trying to optimize an Earth - Mars low-thrust transfer using a particular method. It has been mentioned to me, and I have seen it in many papers, that thrust history ...
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138 views

Is there a calculator or set of formulas for estimating aerobraking on Mars?

I am looking for a calculator or formulas that can be used to calculate the aerobraking on Mars mission. I have found some data on previous Mars flights where aerobraking was used and all my current ...
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427 views

How to find Near Rectilinear Halo Orbits (NHROs)?

Looking all the good questions and answers in this site referent to CR3BP dynamics, periodic orbits, state transition matrices, etc. I wonder: what algorithm or steps do I have to follow to find the ...
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168 views

thrusters, force torque, distribution matrix , orbit maneuver

I have a few questions about computing torques and forces. I use the same configuration as in the thesis titled An Attitude Control Sysytem Design Based on the Turksat-1b Geostationary Satellite. ...
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71 views

Detecting propulsive maneuvers in a table of state vectors

The question Unravelling Cassini's “ball of yarn” orbit around Saturn, tabulation of propulsive maneuvers? asks for a source for documentation of orbital maneuvers of the Cassini spacecraft. Suppose ...
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149 views

Roughly how many kinds of closed or periodic orbits are there in the circular restricted three-body problem?

Question: Roughly how many kinds of closed or periodic orbits are there in the circular restricted three-body problem? Has anyone made an attempt to enumerate and classify/categorize them? Notes: If ...
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188 views

Is it possible to dock with a ship that is on a Galileo-like trajectory?

Reading about missions that have made or will make heavy use of gravity assist (Galileo, Cassini, MESSENGER, BepiColombo...) made me wonder about what if a heavy unmanned ship (BFS?), with all the ...
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422 views

How to derive the differential equations of motion for a dumbbell system ,eg. dumbbell satellites around earth?

From Eq. 2.13 from Orbital Mechanics for Engineering Students (Curtis, 2005) the equation of relative motion between two bodies orbiting around a center of mass can be written as: $$\ddot{\mathbf{r}}...
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293 views

Did DSCOVR travel "along the stable manifold of it's future SE L1 Halo orbit" to get there?

I just wrote (and have since removed) the following paragraph in this answer: As can be heard in this video SpaceX's launch of the DSCOVR spacecraft to Sun-Earth L1 went there almost directly. The ...
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112 views

How can I control the departure and arrival aiming radii in an ideal interplanetary trajectory?

Suppose I am executing an interplanetary rendevous (Hohmann transfer) between two coplanar, perfectly spherical planets, each with circular orbits. The goal is to execute a hyperbolic escape from a ...
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347 views

How to calculate the time of closest approach between two orbiting objects

I have two objects each one moves in elliptic orbit I calculated the distance of closest approach using (the minimum intersection disatnce).Knowing the true anomalies for both objects corresponding to ...
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967 views

What is a "synodic frame"? Can one be defined for an elliptical orbit?

A description of a "synodic frame" was one of the main ingredients in this excellent answer to a question about an animation of a funky-looking orbit that several different and distinctly interesting ...
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How to calculate a Satellite position at a given time

I am trying to write a program to be able to "model" a Low Earth Orbit satellite's position at for a given time in the future. However I do not have a TLE for the desired satellite, I simply have a ...
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Limitations of Clohessy-Wiltshire equations

The Clohessy-Wiltshire equations are a simplified (linearized) model that is applicable under few assumptions: close range circular target orbit no disturbances My question: Up to which boundaries ...
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Why will the SunRISE mission "fly slightly above geosynchronous orbit"?

The blots.nasa.gov article NASA’s SunRISE Mission Studying Solar Particle Storms Moves Toward Launch says that the upcoming SunRISE mission — short for the Sun Radio Interferometer Space Experiment — ...
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85 views

GMAT Orbit Designer

I start to work with GMAT. I am looking into the API capabilites and I found several functions e.g. for the calculation of SSO Orbit Parameters, or Repeating Ground Tracks. So apart from this, is ...
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85 views

Impact Venus with Comet Leonard?

do we have the means to slightly alter Comet Leonard's trajectory so it impacts Venus instead of 'grazing' it in December 2021??
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83 views

What are the energy requirements to reach Earth orbit and Mars orbit assuming no efficiency losses?

Suppose some magic propulsion method exists which directly converts electricity into kinetic energy. And its efficiency is 100%. And its weight is 0. What is a way to calculate the energy requirements ...
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55 views

Is the formula for nodal period of a near-Earth satellite given by Wikipedia correct?

Wikipedia has a formula for the nodal period of a near-Earth satellite, taking into account the oblateness of the Earth (J2), and neglecting other effects (https://en.wikipedia.org/wiki/Nodal_period)....
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28 views

Source of Satellite and Debris Ephemerides for Analysis

I'm working on some code that will fuse ephemeris data, the raw telescope and radar data used for locating and tracking active satellites and space debris. Most of this data is owned by the Air Force ...
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32 views

Calculating body frame X vector's look direction in GEO (NED) frame from roll, pitch and yaw data, is this correct?

I have roll, pitch and yaw angle values for a LEO satellite. Satellite orbit frame and spacecraft body frame are defined as LVLH. The satellite position and velocity are given in ECI/GEI frame. I have ...
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26 views

Difference between distance from Mars (Rmag) and B-plane R coordinate

I am running some GMAT simulations on Mars 2020 trajectory to Mars, following the ephemerides published by JPL. I create a target sequence and target the planet using the b-plane coordinates B and T. ...
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41 views

Calculating Orbital Velocity without Semi-Major-Axis

When playing Kerbal Space Program, I realized that there is a difference between surface speed and orbital speed; this difference is quite variable, although the Kerbin's surface speed is only 175 m/s....
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38 views

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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60 views

J2000 to current ECI transformation matrix

I want to find the transformation matrix that converts an ECI frame at some time 't' (lets say t = 1st January 2020) to J2000 ECI frame (that is ECI frame at noon of 1st January 2000). From what I ...
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158 views

An orbit in the corner of isosceles right-angled triangle

Is it possible to have a non-escape orbit that is equidistant to two celestial bodies (for example, Earth and Mars) at all times? If possible, how much does it cost to keep an object (which is much ...
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81 views

What makes Earth-Mars transfers more non-Hohmann; inclination or eccentricity?

Answers to Why do many Mars missions launch now, if the Hohmann transfer orbit is the most propellant-saving one? and discussions below them made me wonder what makes Earth-Mars transfers more non-...
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118 views

Most efficient (computationally) orbit propagation for simplified J2 effects

I am looking into modeling large scale constellation (hundreds of satellites) and there coverage over earth given a defined conical FOV. The simplified process is a user defines: Constellation (...
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130 views

Where will the DSCOVR mission Falcon 9 2nd stage rocket body end up?

This answer to Why would a mission to Sun-Earth L1 have an instantaneous launch window? suggests that this was quite a delta-v-intensive launch. It left the F9 2nd stage in a very high 17 day orbit ...
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102 views

Keplerian to cartesian elements issue

I am trying to convert between keplerian orbital elements to cartesian position and velocity but something is going wrong. The issue is that I (as a check) compute some keplerian orbital elements with ...
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93 views

Fundamentals of Rendezvous and Proximity Operations

I am trying to work out how to calculate / model a rendezvous and proximity operation between two spacecraft. I have read several research papers, but none of them walk me through step by step how to ...
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51 views

Compute eccentricity and angular momentum vectors of a binary

I having some trouble finding the direction vectors (in 3D) of the eccentricity and angular momentum of a binary. The issue is that the binary has only been described in Keplerian orbital elements and ...
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58 views

What is the relationship between the periapsis altitude and the change in velocity in a gravity assist?

In a gravity assist maneuver if I were to decrease the distance from the rocket to the periapsis of the planet it is orbiting (I believe this is called the periapsis altitude but I may be wrong) it ...
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59 views

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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243 views

Calculate Satellite ground track

I'm trying to find equations to calculate satellite position based on orbit parameters and given time. What I currently have is a mess that is basically giving me bunch of garbage. What is latitude ...
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55 views

Interplanetary space mission debris orbits

I was wondering if anyone knew about a database of orbits for debris from previous interplanetary space missions. I am referring to debris or expired missions by NASA, ESA, JAXA, etc. I know there are ...
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37 views

When will DSCOVR appear too close to the Sun for reliable downlinking?

DSCOVR is in a Lissajous orbit about the Sun-Earth L2 point. That the orbit is called Lissajous rather than halo means that it's periods of horizontal libration and vertical libration are not equal. ...
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67 views

Angles only Orbit Determination for LEO satellites

I have a script that uses the Gauss method for Prilimanry Orbit determination of satellites using 3 sets of ra-dec and the corresponding LST (adapted from the MatLab example given in the appendix of ...
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61 views

Differences between Semi Major Axes and ECF Magnitudes for Circular Orbits with J2 Perturbation

I have simulated (in STK) a satellite at near circular orbit, near-equator, with Brouwer Lyddane Mean Long SMA of 6935.31km, inclination 10 degrees, and eccentricity of 0.0001875 (these are solved-for ...
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238 views

How to estimate which astronaut ends up furthest from the ISS after one orbit?

Three astronauts; Goofus, Gallant and Zippy the Pinhead play a game. All three take their cold gas thruster-powered jet packs and quickly move 100 meters away from the ISS. For some reason after ...
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60 views

How to calculate delta v for orbit change around body; not necessarily Earth?

Let me express my joy at having found this great place of Stack Exchange. My question concerns the calculation of delta v requirements when already in orbit around a body and lowering or raising ...
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119 views

moon's true anomaly at date of new moon

I've seen on this site: https://eclipse.gsfc.nasa.gov/SEhelp/moonorbit.html a table that gives the true anomaly of the moon at the time of new moon. The difference between the true anomaly at one new ...
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110 views

Defining overshoot and undershoot boundary of entry corridor

I have been reading up on the mathematic of atmospheric entry. I have found different methods to theoretically calculate the corridor width but I don't understand how to define the overshoot and ...
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390 views

Getting the Velocity Vector in an Elliptical Orbit

I have a 2-D two body set up. I am using the vis-viva equation to get the velocity scalar of my elliptical orbit. I have the Semi-Major Axis, the radius, the eccentricity vector. I am sure I can ...
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65 views

How are rocket launches scheduled?

With all the satellites and other objects already in space; how exactly are launches scheduled and coordinated? Is there some kind of clearinghouse? How do the mega constellations affect the ...
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40 views

Major topic headings for lunar CubeSat mission design planning?

I am working on a project to design a complete mission for a lunar CubeSat. Assuming that the launch segment is already covered and I need to focus on the spacecraft design. I wanted to know what ...