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 does a spacecraft know that it is in orbit?

After a 5 year long journey in space, Juno finally reached and started orbiting Jupiter. How does the probe actually know that it is in orbit, so that it can send confirmation message like 'Welcome to ...
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The Martian: Does it really take a supercomputer to calculate spaceflight maneuvers?

My preemptive apologies for asking a question about a movie, and the spoilers within said question, but considering the widespread support for its scientific plausibility, I'm hoping you'll let it ...
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What are these orientations called in orbit?

Let's say a spacecraft is in an orbit like this one: If the red arrows point to prograde and retrograde, and the blue arrows point to normal and antinormal, what do the green arrows point to? In ...
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Why will JUICE take 8 years to reach Jupiter, longer than any earlier spacecraft?

Galileo took six years from Earth to Jupiter. Cassini-Huygens took three years to reach Jupiter and six years to reach Saturn. New Horizons took one year to reach Jupiter. Juno was launched in 2011 ...
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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 ...
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Does it take more energy to get to Venus or to Mars?

Let's assume we use the ideal positions of those planets relative to Earth for launch. And let's assume the spacecraft is launched from the same place on Earth. Also let's assume the goal is to get ...
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Going from LEO to lunar using only low-thrust ion propulsion - can it be done?

@SF.'s question What are the parameters of the new Iodine electrical rocket engine developed by RSC Energia? links to the short RT article 'Ten times cheaper': Russian space company testing iodine ...
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How did NASA determine the distance and velocity of voyager 1?

According to Wikipedia At a distance of about 125.97 AU (1.884 × 10$^{10}$ km) from the Sun as of September 9, 2012, it is the farthest manmade object from Earth As of 2013, the probe was moving ...
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How did NASA Conclude that the General Theory of Relativity was not Needed for Earth-Moon Flight Path Computation?

This question is wholly seeking historical evidence and not about physics. It is a follow on from the Physics Stack Exchange question: Could we send a rocket to the Moon without knowledge of general ...
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Do you need 0 km/s velocity to crash into the sun?

I was reading a popular thread about the delta-v required to escape the solar system compared to the delta-v required to crash into the sun. I get it: the earth itself already has a high speed (29.7km/...
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What is the escape-velocity for our galaxy?

What should be the escape velocity for our galaxy and can we calculate it? For instance, if we assume that we don't know the mass of our galaxy, you may consider it as small 'm'.
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How deep is the force well of L4 and L5 Lagrangian Points of Earth-Sun set?

The Lagrangian Points are points in space, where the combination of gravitational pull of a set of two bodies and the centripetal force of orbiting one of them add up to zero. The special property of $...
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How does a Spacecraft change its orbit?

I am a high school student. I saw the latest Indian spacecraft "CHANDRYAANN 2", which was in orbit around the Earth for 14 days..... I am so curious to know how a spacecraft changes its orbit. I ...
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Are there any (Lagrange) points in the Solar System in perpetual shade?

This answer mentioned thermal cycling made me think of this question: Are there any points in the solar system, such as Lagrange points, where a spacecraft could reside in perpetual shade, protected ...
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How often does the ISS orbit align with the day/night terminator?

In the following image (coming from SAT-Flare) you can see the orbit of the ISS (in red) and the day/night terminator (in blue). The terminator separates night from day along the surface of the Earth. ...
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What is the probability of impact?

Space Track is a website dedicated to passing along information about satellites to consumers, primarily satellite operators. The information comes from the US military. In addition to providing the ...
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Is the ideal transfer between two arbitrary planar orbits always a bi-tangential ellipse?

I was reading Hollister David's short paper on bi-tangential transfers. The example he uses is a transfer between a planar circular and an elliptical orbit. I am wondering: Is an ideal, that is, the ...
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Space train concept picking up/releasing cargo

The space train concept involves a ship moving between 2 bodies such as earth/mars with a constant speed and without slowing down. As it flies by each body it orbits around it and continues to the ...
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How fast does Roche limit disintegration proceed?

The answers to this question about encounters with Jupiter keep mentioning the Roche limit, inside which solid objects break up due to tidal gravity gradients. Over what time scale does this effect ...
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Is the difference in orbital velocity of different parts measurable on board the ISS?

When two objects are in different orbits of the same body, no matter how close they are, the inner object will always be faster - it will move farther away from the outer one (until it gets closer ...
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What caused the ISS's sudden loss of altitude in January 2015?

This image from Heavens Above that @PearsonArtPhoto links to in this answer shows the orbital altitude of the International Space Station: In general, the ISS altitude decreases gradually with time ...
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How accurately (maximum possible accuracy) can future satellite positions be predicted?

Agencies/organizations who own/operate satellites want to know their future positions after a certain amount of time. We know that models of satellite dynamics are imperfect and also perturbations ...
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What branches of mathematics are widely used in astrodynamics?

We knew that Voyager 1 and 2 exploited the gravitational slingshot from Saturn and Jupiter back in 70s, and the trajectories were predicted by Newton's laws of motion, and this law we used a lot in ...
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Did the ISS have to adjust its course when the SpaceX Dragon capsule was detached?

We had this question which discussed if space craft had to be corrected in their orbits from the movements from the people inside. (No as their net movement cancels each force out) Following on from ...
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What are “Ohms burns” in the context of Scott Kelly, KSP, and the Space Shuttle?

The Ars Technica video Astronaut Scott Kelly teaches orbital mechanics with Kerbal Space Program (also in YouTube) is a little bit humorous. When Scott Kelley is talking about orbit circularization ...
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If the Earth spun clockwise, how would that affect Space Exploration?

If viewed from the North Pole, the Earth spins counter-clockwise. Because of this, many satellites also orbit in the same direction as you can take advantage of the Earth's rotation and essentially ...
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Why were the Sputniks launched to such high apogee?

Sputnik I was launched to reach as high as 939 km above the sea level and made 1440 orbits. Vostok I with Gagarin aboard was launched to 327 km for one orbit. Wouldn't 200 km or even less be enough to ...
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How to calculate delta-v required for a planet-to-planet Hohmann transfer?

How do you calculate the delta-v required to do a Hohmann transfer from a circular orbit around one body to a circular orbit around another? I'm assuming you'd need to know the masses of the two ...
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Can communication satellites be used in lunar orbit?

Because the moon always has the same orientation to earth, if we want to have communications with manned or robotic explorers on the far side some type of relay would be needed for communication. ...
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Does a mission to Venus orbit require less propellant than a similar mission to Mars?

Gravitational attraction is determined using G (m1m2)/r^2 Which indicates the force is inversely proportional to the square of separation of the bodies Of the terrestrial planets Mercury, Venus, ...
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Preventing orbital decay and micro adjustments to orbits by “leaning” on Earth's magnetic field

Would it be possible, using current technology and renewable energy sources only (e.g. photovoltaics), to magnetically polarize external shields of orbiting satellites in such a way, to effectively ...
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When are there launch windows to Neptune via Jupiter?

I suppose there's a launch window to Neptune by using Jupiter as often as there are Jupiter/Neptune conjunctions, every 13½ years. But which years are Jupiter and Neptune best aligned for gravity ...
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Why was TESS' launch window open for only 40 seconds per day?

The BBC news podcast Science in Action episode New Planet Hunting Mission covers the upcoming TESS mission between 01:00 and 07:15 with Sara Seager, TESS deputy ...
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How does orbital eccentricity affect positions of Lagrange points $L_4$ and $L_5$?

It is often said that the $L_4$ and $L_5$ points are "60 degrees ahead and behind" a planet like Jupiter. Clearly this is true only in the case of circular orbits. In more elliptical orbits, I assume ...
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What is the optimal inclination change strategy?

Consider a transfer between two circular orbits of similar radius, the only difference being the inclination difference, $\alpha$. What's the minimal $\Delta v$ required to perform this transfer? ...
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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 ...
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What are the conditions for re-entry of an object in a (highly) elliptical orbit?

There's something I don't understand: When it comes to de-commissioned satellites, rocket bodies etc. I thought one way of re-entry was via a highly elliptical orbit: The perigee gets low enough (app....
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Minimum Orbit Altitude

What is the minimum altitude required for a Cubesat*-like object to orbit around the Earth? Could you initiate an orbit inside the Earth's atmosphere? *A CubeSat is a 10 cm (1 liter) cube with a mass ...
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Why did rendezvous on Gemini 4 fail so badly?

I can't for the life of me understand why commander Jim McDivitt thought he could eyeball a rendezvous - point the nose and thrust . The futility of that technique is one of the first things even ...
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What is the most fuel efficient way out of the Solar System?

I understand with current technology we can't just fly a straight line out of the solar system but which way out would need the least fuel? Currently to navigate the solar system it is a dance ...
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What artificial satellite has the farthest orbit around the Earth?

What is the furthest Earth orbiting satellite? What is its speed and purpose?
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Gravity assist for manned travel

Since we already use gravity assist to launch satellites through the solar system, is there any way we can use gravity assist to speed up a manned trip to a planet such as Titan or Europa, while also ...
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Under what circumstances would an object falling out of spacecraft start orbiting that spacecraft?

In one of the short stories of Stanislaw Lem the main character, Ijon Tichy, accidentally drops off a piece of pork out of his spaceship, and this pork becomes a satellite of the spaceship, causing ...
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Has a solar sail been used on an orbital mission?

The Wikipedia article on solar sails mentions that they could have a use in modyfing a spacecraft's orbit: Robert L. Forward pointed out that a solar sail could be used to modify the orbit of a ...
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Energy consumption for travelling to the Moon vs. to Mars

I just finished reading Clarke's "Prelude to Space". In chapter XXVII the character Taine gives a talk where he states It sounds paradoxical, but it's easier to make the forty-million-mile journey ...
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What pushes a spacecraft during a flyby?

xkcd today posted the following graphic: Of these, the only one that I really don't understand is "What pushes a spacecraft during a flyby?" I don't understand why this is an issue. How energy is ...
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Space travel using constant acceleration drive: Earth to Europa

Long story short: I'm writing sci-fi and taking my protagonist to Europa. He's got 2 weeks to one month to get there from Earth, give or take a few days. That sounds, of course, preposterous in this ...
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How precisely do we know mass of the ISS?

Everyone knows that in space, every gram counts. Knowing how much mass an orbital object has is necessary for precise motion calculations. So how precisely do we know the mass of ISS? I'm sure we can ...
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What is the frame of reference for orbital speed?

Don't treat this question lightly. It's a thing that's been biting me for a pretty long time, and while it's "intuitively obvious", if you get into finer details, it gets quite convoluted. So, a ...
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What is a “Sailboat Island of Stability”?

The New Horizon's team, in response to an announcement of a press conference from the Hubble team, posted some speculations as to what the press conference might be about. On the list includes "Small ...

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