No, any change in the speed of satellite is going to change the orbital altitude. However, one can change the velocity of a satellite with thrust and not change the altitude. The key is that velocity is a vector quantity (speed and direction). The inclination of the orbit can be changed by thrusting at the proper angles to keep orbit at the same altitude (and same speed)
If you increase spacecraft velocity above circular orbital velocity the orbit changes to eliptical one and the spacraft would start climbing towards apogee. This could be countered by applying thrust radialy towards body it is orbiting. However to do this would require constant fuel expenditure.
Quote from: imfan on 08/05/2017 01:12 pmIf you increase spacecraft velocity above circular orbital velocity the orbit changes to eliptical one and the spacraft would start climbing towards apogee. This could be countered by applying thrust radialy towards body it is orbiting. However to do this would require constant fuel expenditure.Would you have a reference in the litterature that explicitely states this ?Thanks
Quote from: Jim on 08/05/2017 12:57 pmNo, any change in the speed of satellite is going to change the orbital altitude. However, one can change the velocity of a satellite with thrust and not change the altitude. The key is that velocity is a vector quantity (speed and direction). The inclination of the orbit can be changed by thrusting at the proper angles to keep orbit at the same altitude (and same speed)Actually only the same orbital plane interest me.Do you mean that if I stay in the same orbital plane, any speed change will change the orbit for an ellipse (or parabola or hyperbola), but if I want to change the orbital plane I can make it with an appropriate thrust ?Would you have a reference in the litterature that explicitely states this (for the same plane) ?Thanks
With continuous thrust, it would be possible to increase speed while remaining on the same circular trajectory. An initial impulse along the direction of motion would accelerate the satellite, and sustained thrust toward the center of the planet would keep it on the original trajectory.
Quote from: Proponent on 08/06/2017 05:25 amWith continuous thrust, it would be possible to increase speed while remaining on the same circular trajectory. An initial impulse along the direction of motion would accelerate the satellite, and sustained thrust toward the center of the planet would keep it on the original trajectory.You use a conditional sentence, so is it an opinion or would you have a reference in the litterature that explains this possibility ?
You keep asking for literature references for things that are simply basic facts about orbital mechanics that people familiar with orbital mechanics clearly understand. If you continuously fire a thruster directly towards the Earth, this adds to the force of gravity, meaning you need a faster velocity to stay in the same circular orbit. Combined with an initial impulse to increase your velocity, you could travel faster while maintaining the same orbit at least until you run out of fuel.This kind of idea is the only way to travel from one side of the Earth to the exact opposite in less than about 45 minutes.
Sorry to ask for references but the answers above are contradictory, and the link that I give above says that you can not stay on the circular orbit by thrusting in any direction. So who should I believe ?
Quote from: meberbs on 08/07/2017 03:02 pmYou keep asking for literature references for things that are simply basic facts about orbital mechanics that people familiar with orbital mechanics clearly understand. If you continuously fire a thruster directly towards the Earth, this adds to the force of gravity, meaning you need a faster velocity to stay in the same circular orbit. Combined with an initial impulse to increase your velocity, you could travel faster while maintaining the same orbit at least until you run out of fuel.This kind of idea is the only way to travel from one side of the Earth to the exact opposite in less than about 45 minutes.Sorry to ask for references but the answers above are contradictory, and the link that I give above says that you can not stay on the circular orbit by thrusting in any direction. So who should I believe ? As far as I know in science any statement has to be proven, with either a demonstration or a reference of the literature. Do you think that I could refere to your post in a scientific paper that only says "meberbs, at forum.nasaspaceflight.com, stated so" ? I would be very happy if I could but I figure out that it won't do it.This is why I am looking for references. Sorry for that.
hclatomic,You wouldn't be trying to get us to do your homework for you, would you?
I need solid references to include into a paper. I am ready to believe anything you tell me here, but my belief won't be enough. I am searching everywhere on the internet but I can not find nowhere a scientific description of a thrusted satellite that remains on its circular orbit.At the contrary all the books and paper are describing thrusts that change the orbit, wether the thrust is impulsional or low and continuous.
This is why I ask you here if you can drive me to formal scientific evidences and demonstrations of how to perform a satellite acceleration by staying on the same circular orbit.
I need solid references to include into a paper. I am ready to believe anything you tell me here, but my belief won't be enough. I am searching everywhere on the internet but I can not find nowhere a scientific description of a thrusted satellite that remains on its circular orbit.
I need solid references to include into a paper. I am ready to believe anything you tell me here, but my belief won't be enough. I am searching everywhere on the internet but I can not find nowhere a scientific description of a thrusted satellite that remains on its circular orbit.At the contrary all the books and paper are describing thrusts that change the orbit, wether the thrust is impulsional or low and continuous. Here is an other example : Fundamentals of Astrodynamics, Karel F. Wakker, paragraph 19.3 and 19.4https://www.researchgate.net/publication/272507882_Fundamentals_of_AstrodynamicsThis is why I ask you here if you can drive me to formal scientific evidences and demonstrations of how to perform a satellite acceleration by staying on the same circular orbit. My aim is not to offence any one, but just to get some solid scientific evidences.
Quote from: hclatomic on 08/07/2017 03:36 pmQuote from: meberbs on 08/07/2017 03:02 pmYou keep asking for literature references for things that are simply basic facts about orbital mechanics that people familiar with orbital mechanics clearly understand. If you continuously fire a thruster directly towards the Earth, this adds to the force of gravity, meaning you need a faster velocity to stay in the same circular orbit. Combined with an initial impulse to increase your velocity, you could travel faster while maintaining the same orbit at least until you run out of fuel.This kind of idea is the only way to travel from one side of the Earth to the exact opposite in less than about 45 minutes.Sorry to ask for references but the answers above are contradictory, and the link that I give above says that you can not stay on the circular orbit by thrusting in any direction. So who should I believe ? As far as I know in science any statement has to be proven, with either a demonstration or a reference of the literature. Do you think that I could refere to your post in a scientific paper that only says "meberbs, at forum.nasaspaceflight.com, stated so" ? I would be very happy if I could but I figure out that it won't do it.This is why I am looking for references. Sorry for that.You're in a circular orbit right now, maintained by the earth thrusting (wrong term, I know) on your feet. No difference 200 miles up if you use an engine instead of the ground. With constant thrust, you can do anything you want.
May be I should precise that I am not looking for help with a homework but that I have some skills about orbital mechanics. See here for instance : http://vixra.org/pdf/1504.0128v2.pdf, and this work led to the building of an impulsional space transfer simulator, here : http://www.hclatom.net/transferSimulator/From the theorem of the keplerian kinematics (theorem, not theory), it is very simple to prove that thrusting on a circular orbit can not leave the satellite into its circular orbit, in no way at all. What I am interesting in is to have this demonstration done from the newtonian mechanics, instead of the kinematics, if it is possible.
This kind of idea is the only way to travel from one side of the Earth to the exact opposite in less than about 45 minutes.
It is all newtonian physics. Keplers laws of orbital dynamics describe the motion of an object when no forces other than gravity and the centrifugal force are operating on the object. In a circular orbit the force of gravity and the centrifugal force are perfectly balanced. You can increase the velocity by thrusting forward. Of course this will increase the centrifugal force since the centrifugal force is directly related to gravity. Normally this would cause orbit to expand as the centrifugal force grows stronger than gravity, but if you were to simultaneously thrust into the gravity well you could essentially reinforce the force of gravity. With thrusters you can make up the difference between the two forces, and keep the spacecraft on the same trajectory. Like I said before thrusting this way would be considered a stupid waste of fuel, but technically it can be done.
Quote from: meberbs on 08/07/2017 03:02 pmThis kind of idea is the only way to travel from one side of the Earth to the exact opposite in less than about 45 minutes.Well, a gravity train could theoretically make the trip in about 42.2 minutes: https://en.m.wikipedia.org/wiki/Gravity_trainhttp://www.uh.edu/engines/epi2703.htmYou probably would want to stock up on a good supply of unobtanium before starting in on this bit of extreme engineering!Edit: added second reference.
If so, I would like to have the reference of the scientific work that demonstrates this difference of cost in fuel.
If so, I would like to have the reference of the scientific work that demonstrates this difference of cost in fuel. Such a work would certainly contain the orbital mechanics equations that I am looking for.Thanks for help.
Quote from: hclatomic on 08/07/2017 06:04 pmIf so, I would like to have the reference of the scientific work that demonstrates this difference of cost in fuel. Such a work would certainly contain the orbital mechanics equations that I am looking for.Thanks for help.The difference in fuel is so huge that people with experience in this field usually would have no reason to calculate it, it is just obvious to them. As a result, there may not be any references, but it is any easy problem to solve. If someone else doesn't beat me to it, I could work an example later, but I don't have time now.