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].

Filter by
Sorted by
Tagged with
1
vote
1answer
36 views

Will the Emirate Mars Mission, Tianwen-1 and Mars 2020 Mission get closer to each other or spread out on their way to Mars?

The brand new Where Is Roadster page Spacecraft launched to Mars in 2020 (announced here) currently says that it has been: 13 days, 3 hours, 47 minutes and 13 seconds since the Emirates Mars Mission ...
1
vote
1answer
46 views

Orbit Determination of ISS just with a telescope and a watch?

The question Is it possible to represent an orbit with just a periapsis position and 2 angular velocities? got me thinking, suppose I take a telescope and took 3 measurements of ISS angular position ...
3
votes
2answers
87 views

Simply explain for the 2nd “cosmic speed”

Many sources can explain about first, second and third cosmic velocities, but the explanations contain difficult formulas and are not easy to understand. For me, I can check it with powerful magnet ...
3
votes
1answer
51 views

Is it possible to represent an orbit with just a periapsis position and 2 angular velocities?

I was thinking of how complex the orbital elements are and got to wondering whether you can represent orbits in a more simple way. If you start with an ECI coordinate frame and you know the spherical ...
2
votes
1answer
33 views

Accuracy of converting from TLE/Orbital Elements to Cartesian if used for other propagator?

Say that I wanted to propagate a real-life satellite based on an initial position in space. However, the only source of data I can get is from a tracking website like CelesTrak or Space-Track, where ...
32
votes
5answers
7k views

Why is it easier to escape the solar system than get to Mercury or the Sun?

It has been mentioned several times on this site that it is "easier" (less delta-v, and hence less fuel) to reach the escape velocity of the solar system, than to reach the planet Mercury or ...
0
votes
0answers
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.
1
vote
0answers
156 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 ...
1
vote
0answers
47 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-...
4
votes
1answer
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 = \...
15
votes
4answers
4k views

Why is it most efficient to change orbit inclination while crossing the equator?

At T+26:31 into the SpaceX ANASIS-II Mission Livestream, the host mentions that the mission trajectory calls for an orbital inclination change which is performed when the orbit of the second stage and ...
1
vote
0answers
34 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 (...
2
votes
0answers
70 views

Can the location of an unknown planet that is absent from a planetary system be calculated from the orbits of the remaining planets?

In the book ‘Seeker’ by Richard McDevitt, two characters search for a lost planet. They know the star system currently has a number of celestial bodies in orbit around it and their orbits are ...
2
votes
0answers
62 views

Resonant stable tidal Rocking moon

Reading about stackexchange Q&A about tidal locking and libration, I wondered about libration and tidal locking emergence. It seems to me that tidal locking process starts when orbiting body's ...
0
votes
0answers
50 views

Roughly express how much of our Moon's apparent libration amplitude seen from the Geocenter is due to different effects?

My understanding is that when tidal locking of a body first happens it transitions from a state where the average rotation period is faster than the orbital period to a state where they are the same ...
8
votes
3answers
201 views

How “locked” are Pluto and Charon? How much does each librate as seen from the other?

Discussion below Are all or some geostationary satellites tidally locked to the Earth? got me thinking about Pluto and Charon. According to Wikipedia: Charon and Pluto orbit each other every 6.387 ...
8
votes
3answers
476 views

Why are lunar orbits unstable?

I've seen a few times now that objects in orbit around the moon tend to crash into it in relatively short time frames. The orbits tend to become more elliptical until they intersect the surface, is ...
4
votes
3answers
101 views

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 ...
3
votes
1answer
129 views

Optimal point in LEO to perform interplanetary injection burn

I wrote a simulation program in Python to calculate Earth <-> Mars trajectories. Now I would like to test it agains well known trajectories. I used NASA Ames Research Center Trajectory Browser ...
6
votes
3answers
2k views

How does a satellite know it is in apogee or perigee?

How does a rocket know when to do apogee kick motor. Do they orbit once to find highest point?
1
vote
1answer
80 views

Effect of incoming velocity on change in velocity in a gravity assist

In a gravity assist does the incoming velocity of a space craft effect how much speed it gains. For example say a rocket was approaching Jupiter for a gravity assist with speed v and another rocket ...
2
votes
1answer
49 views

Will the new “TLE format” be orbitally-mechanically better than traditional TLEs?

Celetrak's A New Way to Obtain GP Data (aka TLEs) by Dr. T.S. Kelso 2020 May 27 explains the arrival a new infoblob format that in several ways is "better" than the ancient TLE, and contains ...
2
votes
2answers
110 views

Is there a basic 2 or 3 body space simulator

I would like an educational tool to allow a child to 'drag and drop' or 'add' a planet to a workspace, adjust the x, y and z velocities as well as the size and mass. OF the numerous simulators I have ...
1
vote
1answer
75 views

How could one determine the acceleration of a satellite given its ephemeris data, taking into account the earth's oblateness?

I am looking to determine the acceleration vector of a satellite orbiting the earth at a certain point in time given its ephemeris data for that same point in time. I am taking into account the ...
-3
votes
7answers
3k views

Why are all space initiatives designed to get to space overnight when in Nature all extreme feats are achieved in a gradual process

Is the current design paradigm of space engineers still too anti-naturalistic? Why not design Space Cruisers first large & slow but steady into outer orbit, over months rather than in a day? I ...
1
vote
0answers
60 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 ...
0
votes
0answers
25 views

Why can't custom-made TLEs for the DSCOVR launch booster in orbit around Earth work with SDP4?

This fascinating answer to Why has no TLE been published for the DSCOVR satellite and the Falcon 9 R/B? presents links to custom-made TLEs for the Falcon 9 rocket body that put DSCOVR into orbit, and ...
1
vote
2answers
173 views

Delta-v penalty for stopping in a distant Earth orbit versus using atmospheric reentry for braking and returning to Earth from Mars?

Comments below this answer to What precautions are planned to prevent an accident or anomaly from releasing Martians into Earth's environment? say: Seems to me like a high earth orbit lab might be a ...
0
votes
1answer
75 views

Delta-v difference between Mars and Moon

Considering a simple Hohmann transfer, does it take less Delta-v and propellant to go to Mars than to the Moon
1
vote
0answers
135 views

What is the cheapest possible way to land a crew of 2 on the moon?

During the Apollo moon missions, a single very large rocket sent both the Apollo CSM and the LM to the moon in a single shot and it took only around 3 days to get there. However, after the Apollo ...
1
vote
0answers
61 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 ...
1
vote
0answers
40 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 ...
4
votes
1answer
150 views

Could someone explain this formula for da/dt?

The paper Ballistic Coefficient Estimation for Reentry Prediction of Rocket Bodies in Eccentric Orbits Based on TLE Data gives the formula (3) to calculate the time derivative of the semi-major axis ...
1
vote
0answers
48 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 ...
1
vote
1answer
66 views

What are the units for the orbital period equation?

I'm trying to find the time taken for a Hohmann transfer orbit. I've tried using all three of these equations, but when compared against known periods they all evaluate to the same wrong answer, 100 ...
0
votes
2answers
104 views

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 ...
4
votes
1answer
92 views

Get dates when a satellite has performed maneuver from historical TLE data (python)?

I have been recently acquainted with orbital mechanics and am trying to do some analysis on the subject. Since I don't have subject matter expertise, I am at a crossroads with trying to decide that ...
1
vote
2answers
69 views

Stable and Unstable point for GEO satellite

For GEO satellite, 24h period, it has four equilibrium points (two stable point and two unstable point). At the equilibrium point, the transverse acceleration is zero, so semimajor axis changes slowly....
1
vote
0answers
46 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 ...
7
votes
1answer
646 views

Effects On ISS Orbital Mechanics Resulting From Added Mass Of Dragon Capsule Visit

Does the ISS require any type of orbital mechanics management once the Dragon capsule was confirmed with a positive airlock seal, and the mass of the spacecraft, 2 additional astronauts, and supplies ...
20
votes
2answers
2k views

Escaping moons conflict with what I understand of gravity

I have known that the Earth's Moon, let's call it Luna (tip of the hat to The Expanse), has been slowly but surely increasing it's distance from the Earth by a small measure each year. This week I ...
2
votes
0answers
69 views

Hohmann transfer Earth-Mars: 1060 m/s or 2944 m/s?

This diagram has been discussed quite a lot, but my issues is with the Delta v requirement for a Hohmann transfer to Mars. The diagram states that the Delta v for change from Earth intercept to Mars ...
1
vote
0answers
35 views

Would the Yarkovsky effect ever be faster than a solar sail from a 1 AU orbit to the Sun?

Previously I'd mistakenly asked Would the Poynting–Robertson effect ever be faster than a solar sail from a 1 AU orbit to the Sun? when I'd meant to ask about the Yarkovsky effect which can be much ...
6
votes
2answers
795 views

Orbital Rendezvous vs Hohmann Transfer

Let's assume that a spaceship (capsule) is about to dock to the ISS the distance between spaceship (capsule) and ISS is 20 meters the relative velocity between the spaceship (capsule) and ISS is ...
0
votes
0answers
48 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 ...
4
votes
1answer
387 views

What happens to orbit after a radial burn?

We know from Hohmann-Transfer or bi elliptic transfer maneuvers that a burn in the tangential direction of an orbit changes the radius of the orbit. But what happens to an object in orbit, when there ...
1
vote
1answer
54 views

How are orbit insertion changes in altitude and RAAN designed?

Assuming that desired inclination is achieved during the launch, how are the target altitude and RAAN usually achieved in satellite missions, if the launch could only place the satellite on a ...
0
votes
0answers
44 views

How model 3-stage rocket to LEO in STK

I'm trying to design a three-stage rocket ascent flight trajectory to LEO using AGI's Software SKT but I'm in trouble. Could anyone help me with designing it?
1
vote
0answers
51 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 ...
5
votes
0answers
168 views

What exactly is a solar gravity well manouver and in what cases would it be helpful?

In this answer to the gedankenexperiment question With current state of technology if we wanted how long would it take for newly launched probe to overtake Voyagers? I've seen the term "solar gravity ...

1
2 3 4 5
26