How would a Plane/Robot/Ship realistically move in space?

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How would a Plane/Robot/Ship realistically move in space?

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Postby fukuda » Fri May 04, 2018 7:45 pm

I heard Planes in space, if given the technology, wouldn't be able to bank. However, I am having trouble visualizing how a plane, or any sort of big machine, would move out in space. Does anyone know? Thanks.
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Re: How would a Plane/Robot/Ship realistically move in space?

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Postby pwhodges » Sat May 05, 2018 2:55 am

Moving isn't a problem of course; controlling that movement by altering speed and direction is the issue. On earth we do this by transferring momentum between ourselves (or our transport device) and the earth itself or some substantial adjunct of it (water, air even) - these are so much more massive than us that there is no perceptible effect on them from the transfer (except locally in water or air, but the effects there are quickly dispersed through turbulence).

In space there is nothing sufficiently substantial (massive) to exchange momentum with, so we have to take it with us. Ejecting fuel at a very high speed in an appropriate direction enables us to change our momentum, and hence speed and direction (think recoil from a rifle); the speed of ejection compensates for the tiny mass that we can spare for the purpose - but because we are only able to use what we carry, our possibilities are strictly limited, and must be planned before the journey starts to ensure we still have options at the end.
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Re: How would a Plane/Robot/Ship realistically move in space?

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Postby silvermoonlight » Sat May 05, 2018 7:42 am

View Original Postfukuda wrote:I heard Planes in space, if given the technology, wouldn't be able to bank. However, I am having trouble visualizing how a plane, or any sort of big machine, would move out in space. Does anyone know? Thanks.


Watch a series called Babylon 5 as it shows how fight in space could happen and unlike ST its based more on realism, like ship can move up side down and weave.

https://www.youtube.com/watch?v=tWl1ZteUS8U&ab_channel=MartinW
https://www.youtube.com/watch?v=UAsk3ay3e98&ab_channel=StarTrekMarco
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Re: How would a Plane/Robot/Ship realistically move in space?

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Postby Blockio » Sat May 05, 2018 7:47 am

A bit simplified, but yes. However, as soon as gravitational forces are in play, things become a lot more difficult - if, for example, you would try to land something static (aka without substantial material flexibility) the size of a star destroyer on planet earth, not only would aerodynamics suddenly become a major issue, but chances are the vessel would break apart from G-forces and sudden air resistance
EDIT: The "a bit simplified" was directed ad Pwhodges' explanation of propulsion in space vacuum
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Re: How would a Plane/Robot/Ship realistically move in space?

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Postby fukuda » Sat May 05, 2018 12:40 pm

View Original Postsilvermoonlight wrote:Watch a series called Babylon 5 as it shows how fight in space could happen and unlike ST its based more on realism, like ship can move up side down and weave.

https://www.youtube.com/watch?v=tWl1ZteUS8U&ab_channel=MartinW
https://www.youtube.com/watch?v=UAsk3ay3e98&ab_channel=StarTrekMarco


So basically, a plane in space [such as those shown in the videos] would be able to move with "relative ease" and would only experience dramatic shifts in movement when entering different atmospheres?
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Re: How would a Plane/Robot/Ship realistically move in space?

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Postby fukuda » Sat May 05, 2018 12:43 pm

View Original Postpwhodges wrote:Moving isn't a problem of course; controlling that movement by altering speed and direction is the issue. On earth we do this by transferring momentum between ourselves (or our transport device) and the earth itself or some substantial adjunct of it (water, air even) - these are so much more massive than us that there is no perceptible effect on them from the transfer (except locally in water or air, but the effects there are quickly dispersed through turbulence).

In space there is nothing sufficiently substantial (massive) to exchange momentum with, so we have to take it with us. Ejecting fuel at a very high speed in an appropriate direction enables us to change our momentum, and hence speed and direction (think recoil from a rifle); the speed of ejection compensates for the tiny mass that we can spare for the purpose - but because we are only able to use what we carry, our possibilities are strictly limited, and must be planned before the journey starts to ensure we still have options at the end.


Notes taken; Speed of ejection compensates for the tiny mass that we can spare for the purpose. Possibilities are strictly limited.
So the only hoop we'd have to go through is how much fuel we can produce for such a tool?
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Re: How would a Plane/Robot/Ship realistically move in space?

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Postby Blockio » Sat May 05, 2018 3:05 pm

View Original Postfukuda wrote:Notes taken; Speed of ejection compensates for the tiny mass that we can spare for the purpose. Possibilities are strictly limited.
So the only hoop we'd have to go through is how much fuel we can produce for such a tool?

Well, there is a way of using solar or even background radiation for propulsion, something about reflecting the energy off a surface... with this kind of technology, a regular nuclear reactor would also work fairly well for propulsion, and it wouldnt use up nearly as much "fuel" (and since radaiation is off the chart in space anyway, that wouldnt be as big of a problem as well... and, now that I think of it, neither would cooling, given the temperature in vacuum)
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Re: How would a Plane/Robot/Ship realistically move in space?

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Postby silvermoonlight » Sat May 05, 2018 3:08 pm

View Original Postfukuda wrote:So basically, a plane in space [such as those shown in the videos] would be able to move with "relative ease" and would only experience dramatic shifts in movement when entering different atmospheres?


Yes I belive so and that class are called White Stars but they are not godly you can destroy them or they can get huge damage and limb around. http://www.stardestroyer.net/wiki/index.php?title=White_Star
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Re: How would a Plane/Robot/Ship realistically move in space?

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Postby pwhodges » Sat May 05, 2018 5:02 pm

View Original PostBlockio wrote:Well, there is a way of using solar or even background radiation for propulsion, something about reflecting the energy off a surface...

But the effects will be slight and slow, even in the solar system - in deep space I wouldn't bet on it.

with this kind of technology, a regular nuclear reactor would also work fairly well for propulsion, and it wouldnt use up nearly as much "fuel" (and since radiation is off the chart in space anyway, that wouldnt be as big of a problem as well... and,

Although a reactor gives a long term means of providing power to accelerate the rocket stream that is required to change the momentum of the craft, you are still using up the matter which is being ejected - which is a finite resource in a spacecraft.

now that I think of it, neither would cooling, given the temperature in vacuum)

Cooling is a big deal in space. Most of our experience of cooling on Earth is with conduction and convection; but in the emptiness of space neither of these is possible. Cooling by radiation alone is not so easy to arrange.
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Re: How would a Plane/Robot/Ship realistically move in space?

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Postby fukuda » Sat May 05, 2018 5:10 pm

View Original Postpwhodges wrote:Cooling by radiation alone is not so easy to arrange.


So it is possible, but simply hard to develop? How would one do such a thing?

What is the most realistic way a craft would propel itself through space?
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Re: How would a Plane/Robot/Ship realistically move in space?

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Postby Blockio » Sat May 05, 2018 5:28 pm

View Original Postpwhodges wrote:But the effects will be slight and slow, even in the solar system - in deep space I wouldn't bet on it.
I wouldnt necessarily say so, given that NASA (I think) is planning to use this very method to accelerate probes up to 10% light speed to get them to other solar systems, and then be slowed down by the solar radiation there.

Although a reactor gives a long term means of providing power to accelerate the rocket stream that is required to change the momentum of the craft, you are still using up the matter which is being ejected - which is a finite resource in a spacecraft.

Im by no means a physicist, but as far as I know (and the way my former physics teacher explained it in one of his many completely unrelated but mesmerizing stories, is that the only matter that is being ejected are individual protons and electrons. And seeing what the half-lives of some isotopes used in nuclear reactors are, I can see it being a fairly long-term solution

Cooling is a big deal in space. Most of our experience of cooling on Earth is with conduction and convection; but in the emptiness of space neither of these is possible. Cooling by radiation alone is not so easy to arrange.

Bit of a brain fart on my part there... I kinda forgot some basic laws of thermodynamics when saying that cooling is no problem considering how cold space is. Yeah, it would be... if there was any surrounding the part thats to be cooled
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Re: How would a Plane/Robot/Ship realistically move in space?

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Postby pwhodges » Sat May 05, 2018 5:43 pm

View Original Postfukuda wrote:So it is possible, but simply hard to develop? How would one do such a thing?

Assuming a "black body" (it's a technical term, thinking of a deep matt black will do), then the amount of radiation is determined by the (unobstructed) area and the temperature of the surface. The area could be increased by extending some kind of wings through which liquid is pumped to carry heat from the spacecraft to the surface (but note the danger of tubes being pierced by small meteorites). Alternatively, the outside could be well insulated so that the surface could be made hotter (by pumping out the heat), even up to red hot, without affecting those in the interior of the craft. Either way, you are using up energy to pump heat around, so a very long-term energy source (such as a nuclear reactor) would be absolutely required. Note that as craft get bigger, their volume and so presumably the amount of heat-generating life and machinery will go up as the cube of the length, whereas the outside area will go up at only the square - so the larger the spacecraft, the greater the cooling problem becomes.

What is the most realistic way a craft would propel itself through space?

Same as has already been explained - the common word is "rockets"; the limitation is that you run out of "fuel" (whether combustible in the case of conventional rockets or inert in the case of using a nuclear reactor for power). Since nearly all the energy of a space shot is used simply for getting away from the planet's gravity, even remotely viable spacecraft will have to start and end their journeys in remote orbit, relying on local rockets (or space elevators if you want to stick with science fiction) to ferry people and goods up and down.

Wormholes in space and a Warp Drive start to look like a good option, don't you think?

Blockio wrote:I wouldn't necessarily say so, given that NASA (I think) is planning to use this very method to accelerate probes up to 10% light speed to get them to other solar systems, and then be slowed down by the solar radiation there.

Probes are tiny in comparison with anything you might call an actual spacecraft - orders of magnitude smaller; and yes, those means are possible - but they are very, very slow. I think the OP has in mind craft for gadding around the galaxy in - not a decades or centuries long research project.

I'm by no means a physicist, but as far as I know (and the way my former physics teacher explained it in one of his many completely unrelated but mesmerizing stories, is that the only matter that is being ejected are individual protons and electrons. And seeing what the half-lives of some isotopes used in nuclear reactors are, I can see it being a fairly long-term solution

You may be right - I've not looked into it; obviously you need to be able to ensure that the radiation leaving the reactor is doing so as close to the speed of light as possible, and only in one direction! But how practical that would be for a science-fiction spaceliner I can't judge. Warp drive still seems the way to go...
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Re: How would a Plane/Robot/Ship realistically move in space?

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Postby fukuda » Sat May 05, 2018 5:48 pm

View Original Postpwhodges wrote:Assuming a "black body" (it's a technical term, thinking of a deep matt black will do), then the amount of radiation is determined by the (unobstructed) area and the temperature of the surface. The area could be increased by extending some kind of wings through which liquid is pumped to carry heat from the spacecraft to the surface (but note the danger of tubes being pierced by small meteorites). Alternatively, the outside could be well insulated so that the surface could be made hotter (by pumping out the heat), even up to red hot, without affecting those in the interior of the craft. Either way, you are using up energy to pump heat around, so a very long-term energy source (such as a nuclear reactor) would be absolutely required. Note that as craft get bigger, their volume and so presumably the amount of heat-generating life and machinery will go up as the cube of the length, whereas the outside area will go up at only the square - so the larger the spacecraft, the greater the cooling problem becomes.



Thank you for the post, I require it in a side-project. I'm trying to find the most realistic way a mech/ship/plane would move in space and what limitations they would each have.
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