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
4
votes
1answer
73 views

Do Lagrange points still exist if there is significant radiation pressure on the third body from the first?

From this answer: To obtain the distance to L1, find the smallest value of $r$ such that $$\frac{M_2}{r_1^2} + \frac{M_1}{R^2} - \frac{r_1(M_1+M_2)}{R^3} - \frac{M_1}{(R-r_1)^2} = 0.$$ To ...
1
vote
0answers
43 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 ...
1
vote
0answers
53 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 ...
2
votes
1answer
122 views

How can you determine the nature of an object from its flight path angle, velocity, and radius alone?

Assuming that a defense system is capable of determining an object's flight path angle ($\gamma$), velocity (v), and radius (r), how could one differentiate between an ICBM, a satellite, or a solar ...
7
votes
0answers
67 views

How long does the SYLDA fairing stay in orbit after deploying?

For dual-manifest missions, Ariane 5 often uses the Système de Lancement Double or SYLDA system to encapsulate the lower of two stacked satellites. It can be seen in the following image encapsulating ...
-1
votes
1answer
89 views

Help with Vector format N-body state transition matrix

[Update] This is for an on-board autonomous navigation system (3-dimensions, interplanetary) using a Kalman Filter. There is no target trajectory. I have the position and velocity measurement models ...
1
vote
1answer
49 views

How to find instantaneous mass of a central body that results in a given osculating orbit?

This question was underspecified, so I'm going to try again. Osculating orbital elements are Keplerian elements of a hypothetical orbit around a specified center which would be tangent to a specified ...
6
votes
2answers
77 views

How do two-line element sets handle rev numbers > 99,999?

In a two-line element set (TLE), five characters in line 2 -- columns 64-68 -- are for the rev number. (https://en.wikipedia.org/wiki/Two-line_element_set) But some satellites have been around the ...
5
votes
1answer
107 views

Can L3 have halo orbits?

I've recently said you see one co-linear libration point, you seen 'em all. That's what I always say and while halo and other orbits associated with Sun-Earth L1 and L2 work similarly, L3 is 2 AU ...
9
votes
5answers
3k views

Why does launching east result in an orbital inclination equal to the latitude of the launch site?

As mentioned briefly in this answer and this Everyday Astronaut video: And just as a reference, if you launched straight east out of Kennedy Space Center, you'd be on a 28.6° inclination which you ...
2
votes
0answers
31 views

How do you calculate shift in argument of periapsis for a not instantaneous burn assuming you're starting in circular orbit?

Most times we assume that burns are instantaneous, in this case if you burn (without a radial component) at the periapsis or apoapsis there is no shift in argument. Let's say the engine is weak and ...
1
vote
0answers
61 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 ...
4
votes
1answer
75 views

Analytical treatment of relative positions between satellites?

I have been searching the internet for estimation of relative position between two satellites. However, all sources seem to be pointing to methods used for proximity operations, where the math ...
1
vote
0answers
53 views

How can I plot a satellite TLE from its orbital parameters using python and skyfield?

I have a function that uses TLEs (Two-line elements) from Celestrak to plot the visibility of a satellite in Python. Is there a method with skyfield or poliastro to plot a TLE from given orbital ...
26
votes
7answers
12k views

Could we wait for Mars to come to us?

This may be a stupid question but I didn't find much information online about it. The concept is simple, could we launch a vehicle into space from Earth, stop right on Mars trajectory and wait for the ...
0
votes
2answers
181 views

What force would it take to launch a 100kg projectile into orbit from a big cannon?

What force would it take to launch a 100kg projectile into orbit from a big cannon? And what would be the optimum angle of the barrel of the cannon? I'm working on an animation and it's going to ...
1
vote
1answer
221 views

Would it be possible to grab on to a satellite, and use it to keep yourself in orbit in an emergency situation?

You are orbiting Earth when your spacecraft falls apart and you are left flying through space. Will your spacesuit keep you alive long enough to be rescued? Or will your orbit lower to quickly and you ...
3
votes
1answer
234 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 ...
0
votes
0answers
40 views

How to calculate the amount of lunar regolith needed to reduce solar radiation in an area on earth by 0.2% or 0.5%

I am working on a climate change that doubles as a lunar infrastructure project. I am wondering if anyone could direct me to resources or help me answer the question of how much regolith scattered ...
8
votes
2answers
207 views

How do stable equilibrium points work in GEO? If all geosynchronous spacecraft suddenly lost stationkeeping, would most “fall into” one or the other?

The (currently unanswered) question Quantitatively, how deep are the stable equilibrium points in GEO? How much delta-v to move from one to the other? (also see comments at Delta-v to move from GEO to ...
10
votes
1answer
329 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 ...
4
votes
1answer
478 views

Mars and back, staying only a few days

This article states that once you arrive at Mars you'll only have a couple of weeks before you'd have to begin a fresh Hohmann transfer back to Earth, otherwise you'll have to hang out on Mars for ...
4
votes
2answers
408 views

What is the reason for secondary oscillations in apogee and perigee plots for objects 41332 and 41333?

This answer provides quite interesting plots of apogee and perigee for objects 41332 and 41333. The primary (sine wave -like) oscillations are probably due to perturbations caused by potential ...
6
votes
1answer
550 views

Can dust be in orbit around a spacecraft which orbits the Earth or Moon?

In the title above, Can dust be in orbit around a spacecraft which orbits the Earth or Moon? let's define "in orbit" to mean gravitationally bound to the spacecraft long enough to go around it a few ...
3
votes
2answers
147 views

Satellite of a satellite of a satellite

How long can the chain of satellites of satellites be? The Lunar Reconnaissance Orbiter is a satellite of the moon, which is a satellite of Earth, which is a satellite of the sun, which orbits ...
1
vote
1answer
86 views

Confusion with direction (vector) of minimum velocity required to reach an orbit and escape velocity

In order to achieve a stable orbit around Earth, a spacecraft has to travel at velocity not smaller than approximately 7.8 km/s. If my understanding is correct, this figure refers to component of ...
2
votes
2answers
136 views

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 ...
1
vote
1answer
91 views

Trajectory Optimization To The Moon (Case Study: Chandrayaan-2)

People always ask this million dollar question of " What is the best path/trajectory to take to reach a certain orbit or point in space". Chandrayaan-2 had a pretty neat transfer to the moon, it took ...
0
votes
1answer
38 views

How many flavors do dawn-dusk Sun-synchronous orbits come in?

In a series of comments below For a given 48 hour observing period, what fraction of the celestial sphere is available to CHEOPS? there's been a discussion of that spacecraft's dawn-dusk Sun-...
1
vote
0answers
37 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 ...
2
votes
1answer
76 views

How satellite orbital vacancies are determined?

Before a new satellite is launched, its desired orbital altitude, inclination is determined. Now with thousands of satellites already in orbit at different altitudes, how do we know if our desired ...
3
votes
0answers
67 views

Solar system galactic velocity vector relative to ecliptic plane

The Solar system moves through the Milky Way galaxy with velocity of 230 km/s. The ecliptic plane is located ~60 degrees with relation to the galaxy plane, according to this source. The page also ...
1
vote
3answers
126 views

How many hours long is Earth's longest possible sub-orbital flight?

This comment below How long will last the Blue Origin New Shepard space flight? says (in part): The words "suborbital spaceflight" as the first words on Blue Origin's webpage for the New Shepard ...
6
votes
1answer
141 views

How exactly did Jupiter change Ulysses orbital plane from nearly ecliptic to polar?

Ulysses spacecraft trajectory is truly amazing. Utilizing gravity assist from Jupiter it was sent into polar orbit around the Sun. I can understand gravity assist concept, I can also (intuitively) ...
0
votes
0answers
36 views

Preliminary Orbit Determination Packages

I have been looking for free orbit determination packages that take in 3 sets of RA,DEC and time, along with observation position and spits out a preliminary orbit estimate. Even if it is a Matlab/...
59
votes
6answers
10k views

When was Newton “not good enough” for spaceflight; first use and first absolute requirement for relativistic corrections?

Concepts in Special Relativity (1905) and of General relativity (first developed between 1907 and 1915) substantially predated spaceflight; they were well known and had been tested well before objects ...
2
votes
1answer
126 views

Space and Newton laws

I've read some articles which explain that we can't totally rely on Newtonian gravity concepts for understanding the motion of objects in space. My question is how the use of relativity helps us to ...
1
vote
2answers
79 views

Given r/a, what are the limits on the direction that an orbiting body could be moving (e.g. solid angle vs r/a)?

An orbiting object at distance $r$ and semimajor axis $a$ will move at $\sqrt{2 - \displaystyle \frac{r}{a}}$ times the speed of a circular orbit at $r$, no matter what the eccentricity or which ...
0
votes
0answers
45 views

What would be the best course of orbital maneuvers for soft landing an asteroid near the lunar south pole? [duplicate]

Wouldn't it be nice for a colony near the south pole of our Moon to have a nickel-iron asteroid on the surface nearby ! Thousands near-Earth asteroids (NEAs) have been discovered with a diameter up to ...
4
votes
1answer
86 views

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 ...
1
vote
1answer
91 views

When is it okay or at least helpful to use energy arguments in orbital mechanics?

When faced with energy-based questions about spaceflight we often comment something like orbits are about momentum, not energy and use delta-v math in answers. But in this answer to How big a nuke ...
1
vote
1answer
69 views

Are the estimated chances of Bennu hitting Earth in the next 200 years still about “1 in 1410” now that OSIRIS REx has scanned it?

This 2016 answer to Does Bennu pose a risk to Earth? And how can OSIRIS-REx's mission save us? says: Does Bennu pose a risk to Earth?: recent calculations produced a cumulative probability of 1 in ...
2
votes
1answer
57 views

Geocentric latitude and longitude of sub-satellite point

I was trying to derive the expressions for the geocentric latitude and longitude of the sub-satellite point using Keplerian elements. The final equations connecting the combination of the Keplerian ...
2
votes
0answers
48 views

Will it be possible for the crewed Orion spacecraft to fly over the lunar south pole to land the VIPER rover there?

Artemis 2, the planned crewed mission of the Orion spacecraft, will be launched in the fourth quarter of 2022 and will then be the first crewed spacecraft to the Moon in 50 years ! VIPER is a lunar ...
4
votes
1answer
237 views

Why don't spacecraft get left behind once in deep space?

On earth, I know that if I throw a tennis ball straight up while in a car, it comes straight back down thanks to Newton's first law. The ball, the air in the car, and myself are all moving at a speed, ...
47
votes
5answers
14k views

Is it possible for a moon to have a higher surface gravity than the planet it is attached to?

Is it possible that a moon has a higher surface gravity than its planet? I guess it would mean that the moon has a higher mass, but then it would be the planet gravitating around the moon and the ...
3
votes
1answer
83 views

How can Earth-Centered Inertial (ECI) coordinates be properly called “inertial” if the Earth's orbit is always accelerating towards the Sun?

I've just realized (again) that I don't understand anything, something that often happens to me after reading a @DavidHammen answer. How can Earth-Centered Inertial (ECI) coordinates be inertial if ...
6
votes
1answer
151 views

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 ...
5
votes
1answer
491 views

How did the Corona (Key Hole) satellites film canisters deorbit?

The Corona Photographic Surveillance satellites transferred photos back to Earth by releasing a canister with the film, which would deorbit, re-enter, release a parachute and then a plane would ...
1
vote
1answer
57 views

Definition of a trans-Earth injection

Should every "propulsion maneuver used to set a spacecraft on a trajectory which will intersect the Earth's Sphere of influence" be called a trans-Earth injection? Regardless where the spacecraft ...