Questions tagged [astrodynamics]

The study of satellite orbits and space flight dynamics.

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26 views

Lagrange Coefficients for Hyperbolic Orbits

Here is the expressions for f,g and f dot for elliptic orbits. I would like to find similar expressions for hyperbolic orbit case.
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91 views

Does Kepler's Method for Determining Time of flight between two True Anomalies break down with eccentricities approaching 1?

Pretty simple question here. I'm calculating time of flight between two true anomalies by converting those true anomalies to mean anomalies and using the following equation: $\Delta t = t_2-t_1 = \...
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Speed at aphelion is decreasing for Parker Solar Probe with each new orbit despite being closer to the Sun

Sorry for the really bad picture I am looking at some data from the Parker Solar Probe mission and I was looking at the speeds of PSP at perihelion and aphelion at each new, different, orbit (the ...
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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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Increase in period and semi-major axis following near head-on collision between Cerise and Ariane debris (1996)

This report describes the collision of the French satellite Cerise with a piece of Ariane rocket debris (object no. 18208) in 1996: http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?...
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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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108 views

Kepler prediction problem, fundamentals of astrodynamics

I needed help with problem 4.3 of Fundamentals of Astrodynamics by Roger R. Bate, Donald D. Mueller, Jerry E. White (dover, archive.org) Given that $r_0 = (I+j)$ and $v_0 = 2k$ find $r$ and $v$ for ...
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42 views

Determining orbital elements from r and v vectors - Fundamentals of Astrodynamics Example Problem

I am fighting my way through Fundamentals of Astrodynamics 1st edition for the fun of it. I have made it up to section 2.4 and have successfully completed all the example problems and chapter ...
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197 views

Why is there a singularity in Lambert solutions for transfers of pi-multiple degrees?

Lambert provides a solution as long as the transfer angle is not 0, 180 or 180-multiple degrees. Why is that?
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34 views

How can I generate Chebyshev cofficients from SPICE for J2000 Inertial to Moon ME Frame?

I want to extract the Chebyshev coefficients in order to be able to calculate the time-varying transformation from the ICRF / J2000 Inertial frame to the Moon ME (moon mean earth) frame. I know I can ...
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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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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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Does the speed of ISS slow down at the time of a spacewalk or does it become stationary?

The International Space Station (ISS) is orbiting at nearly 7.66 km/s. At such high speeds, how do astronauts perform tasks outside the ISS? Or is it all relative like astronauts are having same speed ...
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358 views

Can we go anywhere in space with only THREE reaction wheels and ONE chemical thruster?

I had a discussion the other day with some of my peers and they were very keen on the fact the it is possible to change your orbit as desired using a single thruster and a three reaction wheels. The ...
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397 views

Why is FORTRAN recommended for astrodynamics rather than MATLAB?

I understand that FORTRAN might be faster in terms of computation time, but I don't understand why it is always recommended by people in the field. Everyone tends to avoid MATLAB for astrodynamics; is ...
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187 views

How big a nuke would be needed to break Phobos out of orbit?

Phobos Radius: 11.267 km Orbital period: 8 hours Equatorial rotation velocity: 11.0 km/h (6.8 mph) (at longest axis) With an 8 hour orbit around Mars it must be going at a fair clip already which ...
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Why haven't there been more space missions that use low-energy trajectories?

The Wikipedia article on low-energy transfers lists only 4 spacecraft over the past decades that at some point of the mission navigated low-energy trajectories, yet there has been extensive research ...
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148 views

What forces a spacecraft, returning from Earth orbit, to synchronize with Earth spin?

This seems like a banal question, but the more I think about it, the less I understand the mechanics of it. Does the progressively denser atmosphere pick up the spacecraft and carries it along the ...
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Launch vehicle trajectory tool for ascent phase to orbit using PYTHON

Currently, I am developing a trajectory optimization tool for launch vehicle from lift-off to orbit using python for my project. Since I'm new to optimization problem, I am finding it hard to ...
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1answer
161 views

Is the amount of accurate information in a TLE equal to that of a single state vector?

My question is basically regarding whether there is orbital information "lost" when converting from a Two Line Element set (TLE) to a state vector. Given that the following are true: I have a TLE, ...
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333 views

Converting UT1/UTC to Julian Date

I am reading about the algorithms to convert from date and time format to Julian Date from the Fundamentals of Astrodynamics and Applications by Vallado (4th Edition) p183. My question is ...
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85 views

Can we calculate elliptical properties in a spherical coordinate system?

Can we calculate the elliptical properties like the semi-major axis and eccentricity using the state vectors (position and velocity) in the spherical coordinate system? http://www.braeunig.us/space/...
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Trouble deriving rectangular components of acceleration of satellite in orbit around Earth with J2 consideration

I am trying to derive the rectangular components of acceleration for a satellite in orbit, with Earth oblateness in consideration, in order to use the RK4 method to find the updated position and ...
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101 views

Properly calculating G-factor

This may sound rather simple, but I was told that technically, G-force readout should actually indicate zero-G on the earth's surface, as well as in a stable orbit. This is due to the fact that G-...
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193 views

Is a solar free-return trajectory possible?

I'm coining a new phrase: "Dyson circuit". Is it possible, with current solar orbital capabilities (see Parker Solar Probe), to drive artificial satellites in a free-return trajectory around the Sun? ...
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131 views

Calculation of V1 (orbital speed) during ascent

I am studying instrumentation of NASA's Orion spacecraft, and there is a readout for V1 (I am assuming this is the "first orbital velocity", for circular orbit), and it seems to be in small decimals. ...
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249 views

Orbit, circularizing, apogee/perigee

First - my question: After the orbit insertion, in the coast stage, and assuming perigee is out of the atmosphere, and neglecting any external forces and influences - is the orbit now "fixed"? As in, ...
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84 views

How to implement a relative motion STM without any numerical integration

I am trying to program the Gim-Alfriend state transition matrix. You can read all about it here. The GA STM is a complex analytical model that maps relative motion of a deputy satellite in a ...
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230 views

Use of thrusters for Collision Avoidance Maneuver

I'm building an orbit propagator that gives the position of two satellites at time T. The position are expressed in ECI and after that are being transformed in LVLH frame (as mentioned ECI to LVLH ...
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Help needed with obtaining position vector of Spacecraft in Heliocentric-Ecliptic frame

I have been now using the ephemeris table attached as an image. It gives the orbital elements of all planets on Jan 1 2000 calculated from Heliocentric-Ecliptic frame. The current planetary orbital ...
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124 views

Could you track small particles in space and could you control their position with lasers or reflected light?

If you released a large amount of small but precise particles (the size of glitter or confetti) is space, between a group of cube sats. Could you track the particles with cameras and/or lasers? And ...
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559 views

What are the practical uses of a state transition matrix?

I am studying different dynamical models of relative motion of satellites. In my work, I've always just used a numerical integrator like RK78 to integrate the cartesian system of equations: $\dot{r}=...
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159 views

What liquids last the longest in space?

I am trying to find something that is somewhat stable as a liquid in space. What happens to various liquid elements and compounds in a vacuum? Is there a list or table of the effects of local space ...
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126 views

How does a Mars lander reach a chosen landing site?

I see lots of questions how landing sites are chosen, but none so far how these landing sites are reached. It already looks like magic how the target planet can be reached at all, but when are ...
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183 views

Angular momentum in non inertial frame [closed]

How to express the angular momentum in non inertial Earth frame like Earth Fixed frame so that angular momentum is conserved ? Is H = R x mV still valid when R and V are taken in the rotating frame ?
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500 views

Transformation between ICRF and Fixed in STK

I am building a satellite orbit propagator in MATLAB and I am using STK as a reference. Comparing TwoBody propagator using RKN78 (MATLAB) with HPOP (degree 1, order 1), I am getting quite good ...
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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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860 views

What is the amount of Delta-V required to enter lunar orbit following Trans-Lunar Injection?

How much do you need to decelerate in order to be captured into a stable lunar orbit from a Trans-Lunar Ejection or TLI-type trajectory?
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106 views

If a spacecraft is orbiting around the Moon, what direction would the nadir axis be?

Nadir for a craft orbiting the Earth would be radially in, is nadir always pointed towards the Earth or is it pointed towards the celestial body that the craft is orbiting?
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Russian Soyuz MS-09 Launch - back and forth rotation of the second stage (along the length axis). Precession?

In the ISS Expedition 56-57 Launch of Russian Soyuz MS-09, in the first view from the external camera at around 3:30, an obvious back and forth rotation (along the length axis) of the rocket can be ...
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Spacecraft Horizon Sensors for Lunar orbit

Recall that "traditional" horizon sensors for Earth missions utilize the IR wavelength regime since this can reveal a good contrast between the cold space and the warm Earth-limb edge. If we were to ...
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Attitude and orbit thrusters catalog

Typically, when trying to adjust simulation parameters (of orbit control, attitude control...) to real world values in order to validate algorithms with comparisons with past and current mission ...
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Reference frames - why do I need to convert to Geocentric Equatorial State Vector to solve equation of motion?

I am asking this question in relation to an example shown in the 'Orbital Mechanics for Engineering Students' book by Howard Curtis (third edition) pp659 example 12.1. The example is demonstrating how ...
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374 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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Small-bodies landing strategies

Looking at past landing missions on small bodies such as Eros, Itokawa and 67P I found different landing strategies Eros: NEAR Shoemaker probe performed 4 impulsive pre-planned open-loop maneuvers to ...
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715 views

How important is plume impingement in rendezvous operations?

When performing space rendezvous operations close to the target vehicle (0-5 m relative distance), pursuer thruster escape nozzle gases can hit the target if firings are done in the direction of ...
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465 views

How to numerically solve an optimal thrust-vectoring problem?

This question is a follow-up to this question and is linked to this question, where if needed more details can be found on the parameters used in the following. For an in-plane non-impulsive orbital ...
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2k views

How to derive the polar form of the equations of motion?

As part of an optimal control problem (see linked problem), I need the polar form of the equations of motion (EOM) defining the orbit of a spacecraft. In e.g. Bryson and Ho (1969) and Vallado (2007) ...
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512 views

Calculating hyperbolic orbit elements for interplanetary intercepts

As part of a final year project at university I'm currently trying to simulate an interplanetary transfer between Earth and Mars for a manned mission. The ultimate aim is to use NASA's GMAT to ...
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How is the trajectory of spacecraft transferring between planets monitored?

The doppler effect can give a pretty measure of radial speed relative to Earth, and radio transmissions can narrow down the radial position, but what about everything else? I can imagine several ways, ...