Ah, is that because it depends on the maximum velocity of the particles out of the arse of the engine? I wasn't sure if speed in space was theoretically uncapped provided you could continue to provide thrust due to a lack of friction?
Doesn't work that way either, using this sort of engine and the speed it is capable of producing the acceleration would have to be gradual. Human body has certain tolerances that have to accounted for.
If the spaceship could negate all G force that would be exerted onto the passengers of said vessel, then yes, more engines would create faster acceleration meaning you would reach your destination faster. But, till we figure out how to counter the effects of G force acceleration is our biggest obstacle. I don't know how G force is in space, never been, but if there are minimal to no effects, then once the vessel broke out of earth's gravity then, theoretically, you could accelerate using both engines to the top speed faster, but not enough to shave a whole 19 days off the trip.
Liquid immersion provides a way to reduce the physical stress of G forces. Forces applied to fluids are distributed as omnidirectional pressures. Because liquids cannot be practically compressed, they do not change density under high acceleration such as performed in aerial maneuvers or space travel. A person immersed in liquid of the same density as tissue has acceleration forces distributed around the body, rather than applied at a single point such as a seat or harness straps. This principle is used in a new type of G-suit called the Libelle G-suit, which allows aircraft pilots to remain conscious and functioning at more than 10 G acceleration by surrounding them with water in a rigid suit. Acceleration protection by liquid immersion is limited by the differential density of body tissues and immersion fluid, limiting the utility of this method to about 15 to 20 G[36] Extending acceleration protection beyond 20 G requires filling the lungs with fluid of density similar to water. An astronaut totally immersed in liquid, with liquid inside all body cavities, will feel little effect from extreme G forces because the forces on a liquid are distributed equally, and in all directions simultaneously. However effects will be felt because of density differences between different body tissues, so an upper acceleration limit still exists. Liquid breathing for acceleration protection may never be practical because of the difficulty of finding a suitable breathing medium of similar density to water that is compatible with lung tissue. Perfluorocarbon fluids are twice as dense as water, hence unsuitable for this application[37]. On the other hand, although perfluorochemicals are denser than water, lung tissue floats within the PFC filled lungs, and if the lungs are not over-filled, there is no compromise in pulmonary or systemic blood flow[38]. Therefore, if the astronaut is immersed in liquid and their lungs are filled with liquid PFC, they should not experience adverse effects, in spite of the almost twofold density difference. Based on interviews with adult patients that experienced partial liquid ventilation, when they became conscious they were unaware that 20-30 ml/kg of PFC was in their lungs during recovery.
The G force produced by an ion engine would be barely noticeable, the astronauts would probably just slowly float to the back of their ship. In space if you have double the thrust, you have double the acceleration and there is no speed limit (except the speed of light which is large enough not to consider). I don't feel like calculating it right now, but i think double the acceleration would not cut the travel time in half, it would decrease it by around 2/3 because if the ship moved faster, it wouldn't fly for so long, so it would have less time to accelerate.
uh... guys, there IS no top speed in space. unless you count the speed of light. as long as you throw something out the back, you will continue to go faster, no matter how slow or fast you throw it. there is nothing to slow you down in space. c'mon guys, logic.
No one said there was a top speed in space, but there is a top speed for an engine (maximum output) and a top speed for a vessel (maximum structural integrity at said speed).
Yes twice the thrust would equate to around half the time. Using the previously mentioned .013 m/s^2, the max velocity at 20 days would be 22.5 km/s around 50000mph. That equates to around .007% speed of light. Hardly worth worrying about relativistic effects.
@7egend: no, you are wrong, why would the structural integrity of something in space be compromised by speed? In an atmosphere fast things hit a lot of air molecules, causing friction which is a really bad thing. But in outer space there are (almost) no molecules to hit so no matter what speed you are travelling at, it's the same. Engines also don't have a top speed, as long as they throw out mass at the back, they continue to accelerate, no matter what their current speed is. In fact with no good frame of reference you can't say at which speed you are actually travelling. In the vacuum of space it's the same if you travel at 100 km/s or if some very very far away planets and stars happen to be moving 100 km/s in the opposite direction while you are standing still.
The first time I heard of the liquid immersion was in the movie Abyss. They explained it very well in there, I remember I did not believe it at first :)
No matter what you do you body has mass and thus momentum, and organs and bones, and when you suddenly stop or increase speed those organs and bones will be delayed meaning they will be flattened and mushed and moved into each other, so yeah your remains will be identifiable to the coroner, once he re-assembles the skull inside. Try to sit in a vat of water and be pushed off the empire state building, see how happy you are afterward, plus the shock-wave will travel unhindered to your body (the same trick safecrackers use) and that wont be fun, but even the simple sudden deceleration will kill your ass.
And in the movie the abyss they use what's used in real life, namely liquid helium to fill the lungs that is still breathable but make it possible to withstand the pressure, which is NOT the same as withstanding acceleration.
Oh and in fighterjets the problem is that the blood gets forced from the head towards the legs, so the pilots learn to use muscles and have a special pressure pants that reacts to force the blood to not completely gather in the legs/extremities and forces some back to supply the brain.
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If we used 2, could we get there in 20 days?
It doesn't work that way. Multiple engines is for faster acceleration, top speed is top speed no matter what.
Ah, is that because it depends on the maximum velocity of the particles out of the arse of the engine? I wasn't sure if speed in space was theoretically uncapped provided you could continue to provide thrust due to a lack of friction?
Excuse my confusion, I'm a biochemist.
@7egend: If you accelerate to top speed faster you will arrive at your destination faster, no?
@tosk04
Doesn't work that way either, using this sort of engine and the speed it is capable of producing the acceleration would have to be gradual. Human body has certain tolerances that have to accounted for.
If the spaceship could negate all G force that would be exerted onto the passengers of said vessel, then yes, more engines would create faster acceleration meaning you would reach your destination faster. But, till we figure out how to counter the effects of G force acceleration is our biggest obstacle. I don't know how G force is in space, never been, but if there are minimal to no effects, then once the vessel broke out of earth's gravity then, theoretically, you could accelerate using both engines to the top speed faster, but not enough to shave a whole 19 days off the trip.
More isn't always better though.
Are you suggesting twin ion engines? Twin Ion Engines? TIE?
Liquid immersion provides a way to reduce the physical stress of G forces. Forces applied to fluids are distributed as omnidirectional pressures. Because liquids cannot be practically compressed, they do not change density under high acceleration such as performed in aerial maneuvers or space travel. A person immersed in liquid of the same density as tissue has acceleration forces distributed around the body, rather than applied at a single point such as a seat or harness straps. This principle is used in a new type of G-suit called the Libelle G-suit, which allows aircraft pilots to remain conscious and functioning at more than 10 G acceleration by surrounding them with water in a rigid suit.
Acceleration protection by liquid immersion is limited by the differential density of body tissues and immersion fluid, limiting the utility of this method to about 15 to 20 G[36] Extending acceleration protection beyond 20 G requires filling the lungs with fluid of density similar to water. An astronaut totally immersed in liquid, with liquid inside all body cavities, will feel little effect from extreme G forces because the forces on a liquid are distributed equally, and in all directions simultaneously. However effects will be felt because of density differences between different body tissues, so an upper acceleration limit still exists.
Liquid breathing for acceleration protection may never be practical because of the difficulty of finding a suitable breathing medium of similar density to water that is compatible with lung tissue. Perfluorocarbon fluids are twice as dense as water, hence unsuitable for this application[37]. On the other hand, although perfluorochemicals are denser than water, lung tissue floats within the PFC filled lungs, and if the lungs are not over-filled, there is no compromise in pulmonary or systemic blood flow[38]. Therefore, if the astronaut is immersed in liquid and their lungs are filled with liquid PFC, they should not experience adverse effects, in spite of the almost twofold density difference. Based on interviews with adult patients that experienced partial liquid ventilation, when they became conscious they were unaware that 20-30 ml/kg of PFC was in their lungs during recovery.
@ryan
You know, I never thought about that. It's used in some rare cases in high pressure diving suits, so why not for space applications.
Thanks for the Enlightenment.
Brilliant, thanks for the enlightening discussion.
The G force produced by an ion engine would be barely noticeable, the astronauts would probably just slowly float to the back of their ship. In space if you have double the thrust, you have double the acceleration and there is no speed limit (except the speed of light which is large enough not to consider). I don't feel like calculating it right now, but i think double the acceleration would not cut the travel time in half, it would decrease it by around 2/3 because if the ship moved faster, it wouldn't fly for so long, so it would have less time to accelerate.
@Ryan
The information you posted sure makes you look smart... until someone notices that it's a direct copy from wikipedia :-P
uh... guys, there IS no top speed in space. unless you count the speed of light. as long as you throw something out the back, you will continue to go faster, no matter how slow or fast you throw it. there is nothing to slow you down in space. c'mon guys, logic.
@maveric101
No one said there was a top speed in space, but there is a top speed for an engine (maximum output) and a top speed for a vessel (maximum structural integrity at said speed).
Yes twice the thrust would equate to around half the time. Using the previously mentioned .013 m/s^2, the max velocity at 20 days would be 22.5 km/s around 50000mph. That equates to around .007% speed of light. Hardly worth worrying about relativistic effects.
@7egend: no, you are wrong, why would the structural integrity of something in space be compromised by speed? In an atmosphere fast things hit a lot of air molecules, causing friction which is a really bad thing. But in outer space there are (almost) no molecules to hit so no matter what speed you are travelling at, it's the same. Engines also don't have a top speed, as long as they throw out mass at the back, they continue to accelerate, no matter what their current speed is. In fact with no good frame of reference you can't say at which speed you are actually travelling. In the vacuum of space it's the same if you travel at 100 km/s or if some very very far away planets and stars happen to be moving 100 km/s in the opposite direction while you are standing still.
@ryan
The first time I heard of the liquid immersion was in the movie Abyss. They explained it very well in there, I remember I did not believe it at first :)
No matter what you do you body has mass and thus momentum, and organs and bones, and when you suddenly stop or increase speed those organs and bones will be delayed meaning they will be flattened and mushed and moved into each other, so yeah your remains will be identifiable to the coroner, once he re-assembles the skull inside.
Try to sit in a vat of water and be pushed off the empire state building, see how happy you are afterward, plus the shock-wave will travel unhindered to your body (the same trick safecrackers use) and that wont be fun, but even the simple sudden deceleration will kill your ass.
And in the movie the abyss they use what's used in real life, namely liquid helium to fill the lungs that is still breathable but make it possible to withstand the pressure, which is NOT the same as withstanding acceleration.
Oh and in fighterjets the problem is that the blood gets forced from the head towards the legs, so the pilots learn to use muscles and have a special pressure pants that reacts to force the blood to not completely gather in the legs/extremities and forces some back to supply the brain.