# Tag Info

104

There are no known orbits of this kind, but they aren't proven to be impossible. You need to have 3 objects in order to have a 3d orbit, and it's known that the general 3-body problem is chaotic and difficult to work with. However, researchers do explore restricted 3-body problems. In these problems, we assume that one object is negligable in mass to the ...

101

Projectile Atmospheric Entry Simulations I put together a bit of code to compute the trajectory of projectiles as they fall through the Earth's atmosphere. I made the following simplifying assumptions: All projectiles were fired from a circular orbit equal in altitude to the ISS (about $400~\text{km}$). The atmosphere is non-rotating with no winds, and is ...

84

You could put both planets in the habitable zone on horseshoe orbits. Janus and Epimetheus orbit Saturn on this type of orbit. From the point of view of one moon, the other follows a horseshoe shape around Saturn (or the star in your case). Most of the time they are relatively far away, but once every cycle the two planets come pretty close to each other ...

77

About 30km/s; that it to say, the velocity cannot change at all if you wish to maintain the same orbit. Every circular orbit is associated with exactly one orbital velocity. Every general elliptical orbit is associated with exactly one velocity profile--one specific apoapsis velocity, one specific periapsis velocity, and one specific curve in between. If ...

72

It really bugs them What you've probably misunderstood is what the term "Java developer" actually denotes. Java developers are a small mammal similar to civet cats in Indonesia both in physical characteristics and how they are used by humans. They remove bugs from and consume carefully managed Java beans, passing out the undigested remainder into the soil ...

66

Is it possible for such a system to exist? I'm sorry, but no. At least not according to orbital mechanics as currently understood. Kepler's third law of planetary motion is one of the old workhorses of orbital mechanics, and applies in this case. As translated and summarized by Wikipedia, it states that: The square of the orbital period of a planet is ...

58

Building on Hariz Rizki's answer, your actual space pirate isn't going to be a swarthy, one legged man in a spacesuit with a parrot on his shoulder, but rather a well dressed functionary at the Deimos space dock waiting for you with a clipboard in hand. No one will suspect Quick, find the space pirate Building spacecraft is difficult and expensive, ...

57

It would lose speed due to drag and fall in. If you're thrusting to maintain speed, just fly like a plane and don't try to orbit. The hypersonic speed of orbital velocity would be conspicuous anyway, not a good way to hide. Do you have any idea how fast orbital velocity is? Low Earth orbit is about 17500 miles per hour. Imagine doing that while still ...

57

C. Must not create any phenomena that would have devastating consequences on life on the planets (i.e.: no radiation, excessive heat, energy surges) except for the diminishing of the Sun's current Solar contributions. The Sun just reduces in size, energy, and mass, but otherwise functions normally. That is not possible, for three reasons. About a third of ...

53

Ok, so you say 'Harmonic Orbits', but actual Space-Talking-Dudes call that 'orbital resonance', and it's the solution to your problem. We've got an example of something ALMOST exactly like what you're talking about right here in our own solar system with Pluto and Neptune. As puppetsock rightly points out, their orbits don't actually intersect because of ...

52

Binary star. If you have two sources of light, you will have 4 options for night and day: double star day, two single star days, and night. These will be predictable but for a complex orbit the ABday, Aday, B day, night pattern might take a very long time to repeat, and seem chaotic in the short to intermediate term. Additionally days will turn into ...

51

Yes and no. This NASA page has a good summary of why we have seasons (emphasis mine): It is true that Earth’s orbit is not a perfect circle. It is a bit lop-sided. During part of the year, Earth is closer to the Sun than at other times. However, in the Northern Hemisphere, we are having winter when Earth is closest to the Sun and summer when it is farthest ...

50

I assumed, based on the limited knowledge I have on the subject, that all star systems have ellipsoidal orbits (the star being in one of the two focal points) just like our own You are right, this is one of Kepler's law, the first. Another one, the second, states that the line connecting the star and the planet swipes equal areas in equal times, or, to put ...

47

Just because you can see pirates coming, doesn't mean you can stop them I'm going to make some assumptions about how your spaceships work. The average distance from Earth to Mars is 225 million km, and travel time is 3 months. Average speed is 29 km/s. Geostationary orbit has orbital velocity of 3 km/s, so you need a 1g burn for about 45 minutes to gain 26 ...

43

In theory, yes, this is possible. In practice, it would be a rare thing to encounter, just because the laws of nature can be fickle and somewhat unpredictable. I'm going to call the planet your animation shows as Earth as PB1 (Planetary Body 1). I'm also going to call the Mars one PB2, and the Moon one PB3. There are some important bits, though: The Roche ...

41

I asked this same question, on the physics stack. The answer is that a body can have only one axis of rotation. Below pasted is the link to the question and the answer I picked. https://physics.stackexchange.com/questions/322200/how-many-different-axes-of-rotation-can-coexist Q: I have questions about rotation. There is a sphere in space. I can ...

39

Two moons are in orbital resonance You can have your two moons be in a m:n orbital resonance, the way that Io and Jupiter are. That way, at some time period $nT$ where $T$ is the orbital period of the outer moon, the two moons will line up in the sky. The orbital period of the inner moon is $nT/m$ in this case. A further twist, which is something that ...

39

Wormhole [A,C,D,E,F,G] A traversalable wormhole would be an excellent mechanism to remove mass from the sun. A wormhole is consistent with general relativity while avoiding all of the pitfalls of violently moving mass from the center of the solar system (which could cause all kinds of orbital perturbations that would be chaotic or even fatal). [B] Would ...

38

Like JDługosz wrote, what will cause problems in the scenario you describe isn't so much your orbit as the fact that you are within the gas giant's atmosphere. I'm going to use Jupiter here to have some specific gas giant to use for examples. Feel free to look up the relevant data for any other gas giant, or come up with your own. For the case we are ...

38

The only way such an arrangement could exist is having external planet being the heaviest and the others each in L1 point of next outer one. Unfortunately such an arrangement is not stable, so it would need corrections to keep alignment and avoid planets to drift out. This kind of correction would be quite small, if you do it before planet/spaceship drifts ...

36

The Roche Limit alluded to in other answers may not be a barrier to this. Rigid Approximation For two rigid planets of the same mass M and radius R, both held together by the force of gravity, the Roche Limit would be the distance between their centres D where any reduction in that distance would mean that tidal force on each planet was greater than the ...

36

It couldn't be done, no matter how improbably skilled the sniper, because he would lack information required to do the aiming. Regular snipers have to consider more than the direction their firing, they need to consider the weather. Snipers will use... well effectively flags to determine wind speed and direction so they can adjust for it; because otherwise ...

36

The orbits of larger moons should be stable and mostly clear of hazards. I'd recommend placing your ship at one of their Trojan points. Just pick the one most convenient. Closer to planet, not already occupied by something, already occupied something that is useful... The actual mechanics can get more complex, but I see nothing in your question suggesting ...

36

Please remember that time is an arbitrary concept Without any outside influence, the very first basis of time is the "day" consisting of a period of "light" and a period of "no light" that we Earthers more commonly know as "night." Day = one Light + one No Light According to Space.com, the moons of Mars are so close to Mars that they cannot be seen from ...

35

I'm surprised no one mentioned Sitnikov planets yet. Image found on Wikipedia. There is a very unlikely constellation in which a planet moves along the axis through the centre of gravity of a binary star system. In such a system, the planet can oscillate chaotically which, given a tilted rotation axis of the planet, would lead to seasons of varying length. ...

35

No. You can't jump from a moon in stable orbit to the planet. This is because the orbital velocity of the satellite is sufficient to keep the satellite in orbit, the jumper starts with that same orbital velocity, and given how large orbital velocities generally are jumping is not going to make a difference. If the orbital velocity was that close to unstable, ...

35

Lots of people here, including the OP, are worrying over the capabilities and tactics of space pirates, but the question fundamentally deals not with those particulars, but rather the economical and political situations which lead to endemic piracy. Piracy in space is harder than piracy on the seas because orbital trajectories are, I'm guessing, much ...

35

You should have a look at Janus and Epimetheus. They are two moons of Saturn that exchange orbits approximately every four Earth years. This setup is probably not stable for more than a few billion years but it might do for what you want. Epimetheus orbits closer to Saturn, so has a shorter orbital period and eventually approached Janus from behind. ...

34

Circular orbits are not practically possible From Astronomy.SE, there are a variety of reasons why orbits are not circular. There is relativity, there is planetary flexing with gravity, there is unequal radiation from the planet's surface (the sunny side reflects and radiates more energy into space, generating net thrust). Then there are the effects of any ...

34

It doesn't seem to be possible using "normal" geology. You'd need a supervolcano to attain the required energies, and "piloting" one with the required precision doesn't look doable. You need to score a direct hit; getting in orbit isn't enough, since any station would have ACS thrusters and be able to both detect a coorbiting incoming missile, and avoid it. ...

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