Traveling at the speed of light and time dilation

[Drakkith]

Yes, the light in front of you is heavily blueshifted while behind you it is redshifted.

 

[DHF]

Ok good to know.
so because its being blueshifted the frequency increses. how would I calculate how much of an increase in radiation my intrepid crew would be facing? would the blueshifting in radiation make the impact such that the acceleration would be pointless? it seems your speed would be limited not only by the energy needed for propulsion but you would need to devote just as much energy to some form of electro-magnetic shield to divert the radiation.

 

[Enigman]

Ok good to know.
so because its being blueshifted the frequency increses. how would I calculate how much of an increase in radiation my intrepid crew would be facing? would the blueshifting in radiation make the impact such that the acceleration would be pointless? it seems your speed would be limited not only by the energy needed for propulsion but you would need to devote just as much energy to some form of electromagnetic shield to divert the radiation.

And dust too...BTW if you don't take into dust, light and gravitational effects into consideration, you will just need a limited amount of fuel to reach 0.99c after that, you won't need any...except to stop.
Just making sure you know that.
Also you could perhaps kill fire with fire and put some kind of cloaking on the ship which absorbs all incident light (a.k.a. perfect black body) and use energy absorbed to beam a high energy LASER or something in form of a spherical aura which would deviate most of the dust and slow all of them down. For fuel it probably should be cold fusion as antimatter can't be 'mined' and to create some you would need at least double the energy needed for the whole journey-not exactly feasible.
For light and dust you may also use some kind of space-time wrapping machine which can clear the spaceship's path. Again not very feasible, except of course a black hole.:tongue2:

And of course don't go to 0.99c near the Earth or any planet cause the huge mass of spaceship will destroy it(the planet) also stop before going too near to alpha centauri...
And is this just a one-way trip? You know, if you are going to get them to come back 'twin paradox' comes into play...making the ship just one glorified time-capsule.
cheers!

 

[cyberdiver]

Ok good to know.
so because its being blueshifted the frequency increses. how would I calculate how much of an increase in radiation my intrepid crew would be facing? would the blueshifting in radiation make the impact such that the acceleration would be pointless? it seems your speed would be limited not only by the energy needed for propulsion but you would need to devote just as much energy to some form of electro-magnetic shield to divert the radiation.

The blueshift/redshift/time dilation/relative mass increase/Lorentz contraction (or relativistic effects, in short) can be calculated with the following equation:
γ = 1/sqrt(1-v^2/c^2)
Where:
γ = Lorentz factor (the factor of relativistic effects)
v = Relative velocity
c = The speed of light

For example, let's say that you're traveling at 99% the speed of light:
γ = 1/sqrt(1-2.97e8/3e8)
An easier way is:
γ = 1/sqrt(1-0.99^2)
γ = 7.09 (3 significant figures)

Let's say that you were approaching an orange star. According to http://rohanhill.com/tools/WaveToRGB/ handy wavelength-to-RGB calculator site, that gives us a wavelength of about 620 nm.
620/7.09
= 87.4 nm (3 significant figures)

The star's orange light would be blueshifted into extreme ultraviolet (all the wavelengths can be looked up on Wikipedia). On the other hand, 4 mm microwaves would be blueshifted into the red part of the visible spectrum. BTW, a magnetic field wouldn't help much to stop UV and X-rays. It shields against particle radiation, like the stuff in a solar storm. Have the dust shield double as a UV shield and put ice between the crew and the front.

EDIT: http://www.projectrho.com/public_html/rocket/slowerlight.php
This site should help with designing your spacecraft .

 

[DHF]

Thanks that site is a good read and hopefully give me some ideas.
I had not considered the idea that cell damage would occur during the suspended animation trip. though I think I can get around that by putting the crew in a deep hypotherrmic state instead of cryostasis, the crew would not be frozen but their metabolisms would be slowed to 1% of normal. Adding in a nano-tech immune and repair system should keep the crew alive during the trip. still not sure which propulsion system, though I am leaning towards the laser assisted solar sail and antimatter combo drive.

 

[Varun Bhardwaj]

to cross the barrier means traveling a distance in zero time. if you do it than your 1 dimension will loss (you are three dimensional) . And you will not stop anywhere. To do it your mass can be zero or energy can be infinite.

 

[phinds]

to cross the barrier means traveling a distance in zero time. if you do it than your 1 dimension will loss (you are three dimensional) . And you will not stop anywhere.

Huh ?

 

[OCR]

I like the aspect of the crew waking up to find that their civilization had passed them by.

Yes, it might be a big surprise... lol


http://en.wikipedia.org/wiki/Planet_of_the_Apes_(1968_film)

http://en.wikipedia.org/wiki/Planet_of_the_Apes_(novel)





OCR

 

[DHF]

Yes OCR that had come to mind :) I actually quite like the idea of exploring what cizilization comes after our own but that won't be in the cards for this tale :)

I know giving them a 1G acceleration would be out of the question, the mass ration would be be almost 900:1 and that just won't fly. I was thinking about giving them an acceleration of 0.10%G or even 0.05% G.

I got around the whole keeping the crew alive thing by ditching a living crew. The current crew will be androids with AIs based on human astronauts back on Earth. In this way the life support can be ditched and the mass of the ship can be further reduced because they won't have to worry about a return flight. Once the ship arrives, the crew will be stationed in the Alpha Centuri Star system permanently, intending to explore and run experiments while transmitting the results back home. The drama will arrive when certain members of the crew start to realize that their programming has changed during the flight, they come to the conclusion that they are self aware and tensions arise when members of the crew question the idea of being abandoned light years from home.

 

[Ryan_m_b]

Yes OCR that had come to mind :) I actually quite like the idea of exploring what cizilization comes after our own but that won't be in the cards for this tale :)

I know giving them a 1G acceleration would be out of the question, the mass ration would be be almost 900:1 and that just won't fly. I was thinking about giving them an acceleration of 0.10%G or even 0.05% G.

To work out how much fuel you need you have to have a speed in mind, not just acceleration.

I got around the whole keeping the crew alive thing by ditching a living crew. The current crew will be androids with AIs based on human astronauts back on Earth. In this way the life support can be ditched and the mass of the ship can be further reduced because they won't have to worry about a return flight. Once the ship arrives, the crew will be stationed in the Alpha Centuri Star system permanently, intending to explore and run experiments while transmitting the results back home. The drama will arrive when certain members of the crew start to realize that their programming has changed during the flight, they come to the conclusion that they are self aware and tensions arise when members of the crew question the idea of being abandoned light years from home.

Seems like a cool idea. If you want some similar fiction to get inspiration from Saturns Children and Neptune's Brood (the better of the two IMO) by Charles Stross are great books. They feature a future time when humanity has gone extinct leaving behind robots, based on humans, to continue civilisation. The technology of their bodies makes them much more durable meaning they can do away with pesky portable ecosystems or having to travel at high speed. They just go as fast as they can with their energy budget (usually 0.01C) and crank their clock rate right down to make the journey seem subjectively quick.

 

[DHF]

Well theoretically using an acceleration of 0.05G they could reach up to 0.43c before having to decelerate. This would get them to their destination in under 20 years. 24 years would be an acceptable amount of time for the scientific community on Earth to wait before receiving data however I am afraid that going that fast would again blow the mass ratio out of the water. having them travel at 0.10c would keep the mass of the ship down but it woul make the trip take close to 100 years, its a pretty long term investment for Earth, even in a sci fi future I am sure politicians would balk at funding a project that neither they nor their constituents have any hope of seeing a return of investment on. I toyed with the idea of Anti matter propulsion but I don't think 200 years is enough time for Earth to have reached a point where we can cheaply mass produce Gobs an gobs of anti hydrogen. Even if they did, then I would have to increase the mass to account for a complex containment system and heavy shielding least a stray Toyota sized rock strikes the fuel tanks on the way there an goodbye ship.

P.S. Thanks for the references, I will certainly look them up this weekend, they sound very interesting.

 

[DHF]

Ok so having fully settled on a Fusion based engine. I am trying to cement how long it will take them. I am having a hard time pinning down their maximum speed. when researching fusion as a method of propulsion, most material I have read marks upper limits on how fast you could go with a particular type of fusion (between 8-11%c) If my characters were utilizing constant acceleration wouldn't speed just be a matter of fuel? or is there some other mechanism that would create a cap on speed? if there is a cap on the speed then how does that work for my characters? Since they are going to alpha Centuri, and using .10G acceleration. theoretically they could reach .57c and be there in a little over 13 years. but if they are limited to a maximum velocity of say 10%c then would they just accelerate for a year then coast for a few decades then decelerate for another year?

 

[Ryan_m_b]

Fuel determines maximum speed in the sense of how fast you can accelerate to before you don't have enough fuel to slow down. It also affects how fast you can accelerate because fuel obviously has mass. If your engine can put out 1MN of thrust and your payload masses 100 tonnes then your maximum acceleration is 1G. But you have to add your fuel on top. If that amounts to 900 tonnes (for example) then your maximum initial acceleration is 0.1G.

If you don't have fuel for constant acceleration (and it's unlikely you will) then yes your craft will have to coast for a large portion of it's journey.

 

[DHF]

OK that works for me. so the only cap on speed is the amount of fuel you can carry. So if they wanted to go .12c its simply a matter of: can you carry enough fuel to accelerate to that speed and still have enough fuel to decelerate? I was under the impression that there was a theoretical maximum exhaust speed depending on the type of fusion reaction you used.

If I was wrong about the Theoretical maximum then I will have the engine use a D + 3He reaction. they can accelerate for a year up to about 12%c, coast for about 35 years then decelerate. Total trip time: 37.7 years. I can deal with that.

would the ship be able to communicate with Earth while they are in transit or would communications be distorted from them moving away at relativistic speeds?Thanks for the help :)

 

[phinds]

Also, keep in mind that one thing science fiction generally ignores is that at even low relativistic speeds, when you hit dust particles, or worse yet something even a little larger than dust, YOU are likely to become dust. So while speed is theoretically limited only in the ways that Ryan pointed out, in the real world, you are going to need shielding of some kind and the faster you got the harder is is to have any effective shielding. I don't know of any current technology that would provide protection at even .1c, but this is not an area that I know much of anything about, I'm just pointing this out from my perspective as a practical engineer.

 

[phinds]

would the ship be able to communicate with Earth while they are in transit or would communications be distorted from them moving away at relativistic speeds?

Communication signals would experience a predictable and continuous down-shift in frequency during the acceleration and then become constantly downshifted while coasting but all that can be compensated for. The biggest issue, I think, would be signal power but you can hand-wave your way out of that pretty easily.

 

[DHF]

Thank you very much Phinds, I was keeping that in mind when designing the ship for the book. when the ship is traveling it employ a shielded dome on the front of the ship and shielded panels covering the sides. while in transit the ship looks like a mushroom with an octagon shaped stem. when the ship arrives it ejects the dome and shielded panels to reduce mass and make travel around the solar system more fuel efficient. each of the eight sides of the ship will extend solar panels to provide auxiliary energy for the ship and crew. power will also come from a second fusion reactor that will utilize the fuel that wasn't spent for propulsion.

Though the front of the ship is protected, the rest of the hull is more vulnerable. while in transit, cosmic rays penetrate the less shielded area of the hull. part of the crew's programming is effected by interaction with said cosmic rays and this leads to uncomfortable thoughts popping up during their mission, like home sickness.

 

[Ryan_m_b]

Phinds is right of course, you'll need to take into account shielding.

OK that works for me. so the only cap on speed is the amount of fuel you can carry. So if they wanted to go .12c its simply a matter of: can you carry enough fuel to accelerate to that speed and still have enough fuel to decelerate?

Not quite, you missed the point of maximum acceleration. If you want to go to speed X in a given time frame you have to have enough fuel to accelerate to it and slow down and a powerful enough engine.

Some back of the envelop calculations (feel free to check this by using the rocket equation yourself, it's not my field by a long way):

If we assume the craft masses 1000 tonnes (small but I'm handwaving here) and the exhaust velocity of a fusion rocket is 500kmps (taking a rough average from these estimates)) then to get to .12c would require ~8*10³⁷ kg of fuel (much more than the mass of the solar system). And that's just to reach the speed! Not even to slow down again.

(You have to bump exhaust velocity way up before the numbers become reasonable. At 10,000kps the fuel mass would be 40 thousand tonnes of fuel. At 100,000kps it's just 440 tonnes but that implies you have an exhaust velocity of 1/3rd the speed of light! At that speed you'd have to pump in ~5e15 joules per kilo of fuel, 300x global energy usage.)

How much thrust you produce is worked out by your mass flow x exhaust velocity. Essentially how much mass exits the back of the ship (assuming it does so perfectly collimated). For the 500kmps ship to accelerate at 1G would take a mass flow of 1.6e33 kgps, again more than the amount of mass in the solar system.

So you'll have to do some playing with the numbers to decide on a reasonable exhaust velocity, a reasonable payload mass and a reasonable mass flow. Once you have that you can begin to work out what acceleration and top speed is feasible.

would the ship be able to communicate with Earth while they are in transit or would communications be distorted from them moving away at relativistic speeds?

I imagine that should be relatively easy to compensate for, it's just Doppler shift.

Thanks for the help :)

No worries.

 

[DHF]

then to get to .12c would require ~8*1037 kg of fuel (much more than the mass of the solar system). And that's just to reach the speed! Not even to slow down again..

augh! damn you reality with all your numbers!

the heck with it, I am just going to put them in a trash can and give them a good shove. they should get there in a few million years, they are androids, they won't care.

there, mass and fuel and all that nonsense solved ;)

or I might just have a dragon take them there. that should help me avoid any further calculations :D

 

[Ryan_m_b]

augh! damn you reality with all your numbers!

Lol! IMO it's entirely possible to write hard SF to get round this, generally there just has to be one piece of super-technology proposed.

the heck with it, I am just going to put them in a trash can and give them a good shove. they should get there in a few million years, they are androids, they won't care.

To be fair that isn't a bad idea. I've read stories before where androids traveled interstellar at very slow speeds. It might have taken them millennia but that wasn't a problem because the crew just cranked their clock rate right down as a form of stasis (speeding back up regularly to conduct maintenance) and anyone not essential was kept backed up on a computer ready to download into a body constructed on arrival.

 

[Ryan_m_b]

I just remembered another way (from an SF story) you could tap dance past this problem and keep it within the realm of acceptabley hard science fiction. You could propose that the ship is a type of Starwisp, essentially a giant solar sail, and give it a small payload of around 1 tonne. The ship could be accelerated by laser arrays orbiting the sun, when it comes to slowing down it could release a large part of its sail which doubles up as a mirror bouncing the beam back to the small payload. The payload itself could be some hypothetically super-compact fab lab, a number of small robots, a computer and some source of energy. AI could be downloaded into the robots and sent out to set up the fab lab, gather resources and build infrastructure. It might take a very long time but assuming no catastrophe (a big assumption admittedly) those initial machines could build up factories for mass producing stored copies of their crew.

 

[DHF]

I know: The ship will be powered by unobtainium. there, done!

 

[Ryan_m_b]

You could switch from fusion to some sort of antimatter rocket. Getting back to the energy requirement of 5e15 joules per kilo for an exhaust velocity of 1e8mps: annihilating a kilo of matter gives 9e16 joules (18 times more than the energy requirement). If you suggest that antimatter can be made in bulk then you could up your fuel requirement by 5% and have half of that be antimatter. That extra 5% of matter and antimatter could be annihilated to produce the energy to accelerate the fuel but you'd need a hand wavy answer to suggest how.

 

[DHF]

I had initially shied away from antimatter because I felt that it might realistically be thousands of years before we can use it in a practical manner. however the more we crunch numbers, I just don't think Fusion will do the job if I want the crew to get there in a human lifetime. Ironically I move away from having a living crew to escape the confines of human life spans but then I realized the mission would still need to operate within human life spans because humans funded the mission and I don't think the government or a private company woul spend hundreds of billions of dollars on a venture that would take centuries to unfold.

so getting back to anti-matter. I suppose if it is the only way I can make it work I will go that route, but I feel that we would sooner perfect proton - proton fusion first. Speaking of which, it is not as powerful as matter/anti-matter but if the characters had access to such perfect fusion, what kind of speeds an acceleration could I expect?

 

[Deleted member 498135]

It's impossible for objects with mass to attain the speed of light. You're question is therefore unanswerable because it essentially asks "if we ignore the laws of physics what do the laws of physical say?"

Very true... Too bad :( if it was real, hypothetically speaking, would time stop?

 

[Travis_King]

This is why many SF writers who want to lean toward the hard side of SF tend to:
a) Stay within the Solar System
b) Stay within some distant star system which was seeded long ago by a sub-light speed ship
c) Go the colony sized ship route
d) Use space-time warping as their mode of travel rather than actual ship velocity. I've seen several instances of this type where you don't even have to explain how; the main characters don't know how it works, they just know that someone in their world knows and created the drive.

 

[DHF]

This is why many SF writers who want to lean toward the hard side of SF tend to:
d) Use space-time warping as their mode of travel rather than actual ship velocity. I've seen several instances of this type where you don't even have to explain how; the main characters don't know how it works, they just know that someone in their world knows and created the drive.

This is very true, an I can appreciate that as I have learned during my research just how ridiculously hard it is to travel between stars. Even granting the characters mastery over fusion we would still have them *Crawling* to the nearest star and doing so only at a ludicrous expenditure of fuel.

Truth is even if we set the tale 1000 years in the future and handwavinly gave the characters an unlimited power source the size an mass of a marble... they would still be limited just under the speed of light and thus travel from star to star would still take years, ruling out any sort of federation or swashbuckling through the galaxy.

As such my tale focuses on the next generation of explorers, a humanity that has made travel through their own star system practical. But for all their technology, for all the awesome power of Fusion and Anti-matter energy drives... getting to the nearest star is as hard for them as the moon was for the Apollo program.

 

[Enigman]

Well, if you are reaching for hand-wavium already and this is your general story line:

I got around the whole keeping the crew alive thing by ditching a living crew. The current crew will be androids with AIs based on human astronauts back on Earth. In this way the life support can be ditched and the mass of the ship can be further reduced because they won't have to worry about a return flight. Once the ship arrives, the crew will be stationed in the Alpha Centuri Star system permanently, intending to explore and run experiments while transmitting the results back home. The drama will arrive when certain members of the crew start to realize that their programming has changed during the flight, they come to the conclusion that they are self aware and tensions arise when members of the crew question the idea of being abandoned light years from home.

then-
http://mysite.verizon.net/res148h4j/javascript/script_starship.html
at 10000000 G for 4.22 light years distance time on board is about 1 min 47 sec

or you could use:

http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)
with best time as 133 years to alpha centauri.

or other versions of nuke-propulsions:

Unlike Daedalus' (see the next quote) closed-cycle fusion engine, Longshot would use a long-lived nuclear fission reactor for power. Initially generating 300 kilowatts, the reactor would power a number of lasers in the engine that would be used to ignite inertial confinement fusion similar to that in Daedalus. The main design difference is that Daedalus would rely on the fusion reaction being able to power the ship as well, whereas in Longshot the internal reactor would provide this power.

The reactor would also be used to power a laser for communications back to Earth, with a maximum power of 250 kilowatts. For most of the journey this would be used at a much lower power for sending data about the interstellar medium, but during the flyby the main engine section would be discarded and the entire power capacity dedicated to communications at about 1 kilobit per second.

Longshot would have a mass of 396 metric tons (873,000 lb) at the start of the mission, including 264 tonnes of Helium-3/Deuterium pellet fuel/propellant. The active mission payload, which includes the fission reactor but not the discarded main propulsion section, would have a mass of around 30 tonnes.

A difference in the mission architecture between Longshot and the Daedalus study is that Longshot would go into orbit about the target star while the higher speed Daedalus would do a one shot fly-by lasting a comparatively short time.

The journey to Alpha Centauri B orbit would take about 100 years, at an average velocity of approximately 13411 km/s, about 4.5% the speed of light, and another 4.39 years would be necessary for the data to reach Earth

http://en.wikipedia.org/wiki/Project_Longshot

Alan Bond led a team of scientists and engineers who proposed using a fusion rocket to reach Barnard's Star, only 5.9 light years away. The trip was estimated to take 50 years, but the design was required to be flexible enough that it could be sent to any of a number of other target stars.
[..]
Daedalus would be propelled by a fusion rocket using pellets of deuterium/helium-3 mix that would be ignited in the reaction chamber by inertial confinement using electron beams. The electron beam system would be powered by a set of induction coils tapping energy from the plasma exhaust stream. 250 pellets would be detonated per second, and the resulting plasma would be directed by a magnetic nozzle. The computed burn-up fraction for the fusion fuels was 0.175 and 0.133 for the First & Second stages, producing exhaust velocities of 10,600 km/s and 9,210 km/s, respectively. Due to the scarcity of helium-3 it was to be mined from the atmosphere of Jupiter via large hot-air balloon supported robotic factories over a 20 year period.

The second stage would have two 5-meter optical telescopes and two 20-meter radio telescopes. About 25 years after launch these telescopes would begin examining the area around Barnard's Star to learn more about any accompanying planets. This information would be sent back to Earth, using the 40-meter diameter second stage engine bell as a communications dish, and targets of interest would be selected. Since the spacecraft would not decelerate upon reaching Barnard's Star, Daedalus would carry 18 autonomous sub-probes that would be launched between 7.2 and 1.8 years before the main craft entered the target system. These sub-probes would be propelled by nuclear-powered ion drives and carry cameras, spectrometers, and other sensory equipment. They would fly past their targets, still traveling at 12% of the speed of light, and transmit their findings back to the Daedalus second stage mothership for relay back to Earth.

The ship's payload bay containing its sub-probes, telescopes, and other equipment would be protected from the interstellar medium during transit by a beryllium disk up to 7 mm thick and weighing up to 50 tonnes. This erosion shield would be made from beryllium due to its lightness and high latent heat of vaporisation. Larger obstacles that might be encountered while passing through the target system would be dispersed by an artificially generated cloud of particles, ejected by support vehicles called dust bugs, some 200 km ahead of the vehicle. The spacecraft would carry a number of robot "wardens" capable of autonomously repairing damage or malfunctions.

Overall length: 190 metres
Propellant mass first stage: 46,000 tonnes
Propellant mass second stage: 4,000 tonnes
First stage empty mass at staging: 1,690 tonnes
Second stage mass at cruise speed: 980 tonnes
Engine burn time first stage: 2.05 years
Engine burn time second stage: 1.76 years
Thrust first stage: 7,540,000 Newtons
Thrust second stage: 663,000 Newtons
Engine exhaust velocity: 10,600,000 m/s & 9,210,000 m/s
Payload mass: 450 tonnes

http://en.wikipedia.org/wiki/Project_Daedalus

 

[DHF]

Thanks Enigman, I appreciate the references. I tempting as it is, I am trying to wave my hands as little as possible, this is difficult because I am Italian but I will try none the less.

I am trying to strike a balance, I would like to keep the propulsion and fuel ratio withing believable limits but for the sake of the plot I would like to keep their trip within a 20-40 year window.

The current design I have on the drawing board is designed to go one way to the nearest star and has no considerations for food or life support because the crew will not need either, even still the ship is little more then a latticework cylinder covered in fuel tanks. not a very exciting look but exciting and realistic seem mutually exclusive.

 

[Enigman]

Er...only the first one was hand-waving and meant as a pun, the nuclear propulsion examples are real scientific models.
Project Longshot fits best with your needs:
Project Longshot was a conceptual design for an interstellar spacecraft , an unmanned probe intended to fly to and enter orbit around Alpha Centauri B, and that would be powered by nuclear pulse propulsion.

Developed by the US Naval Academy and NASA from 1987 to 1988, Longshot was designed to be built at Space Station Freedom, the precursor to the existing International Space Station.
http://en.wikipedia.org/wiki/Project_Longshot

 

[DHF]

No no I wasnt dismissing the Longshot and Deadalus designs, I have heard of them and I fully appreciated the material you provided. my reference to handwavium was strictly addressing your first suggestion with 10000000G propulsion. I mean sure if I was setting the tale 10,000 years in the future and portable pocket stars were as common as cellphones then what the heck why not :)

Actually the very earliest concept for the book was total hanwavium. it was set at a much more distant point and the ship was straight out of the thickest sci-fi mud, but the more I developed it the more I realized that I wanted something that felt like like the adventures of real astronauts with just enough Tech to make interstellar travel plausible. There will be no space dragons, no evil world conquers with cosmic cubes... The Drama comes from detailing how difficult their journey was and how much they had to sacrifice to make it happen, and then regret, wondering if they sacrificed too much.

 

[lendav_rott]

Mass effect relays from Mass effect franchise can propel a vessel faster than the speed of light :D :D :D

 

[Infinite/Zero]

A thing will be always greater than a thing(not infinity).
It is possible.

 

[DHF]

Everything I have read advocates putting the engine in front of the ship and pulling the bulk of the ship rather then pushing it in order to reduce the amount of mass the engines have to move. Personally I dislike all of the designs I have seen to that end and I am trying to find alternatives. Two possibilities:

My first Idea was to build the engines and fuel tanks as a self contained unit, The Cargo and crew quarters will be a separate ship that is pushed in front of the Engines by electro magnets. Does this design have any feasibility? will pushing the bulk by magnets relieve any of the burden of mass on the engines or will the mass be the same even though there is no physical connection between the engines and the cargo and crew vessel?

The other idea was to build it Tie Fighter style, with the Bulk of the ship being built flush with the Engines so that there is nothing being pushed in front of the engines or being pulled behind them. would this be more fuel efficient then pushing the bulk of the ship in front of the engines?

Do either of these ideas have any merit?

 

[Ryan_m_b]

Everything I have read advocates putting the engine in front of the ship and pulling the bulk of the ship rather then pushing it in order to reduce the amount of mass the engines have to move.

Could you give examples of what you mean by this? No matter where you put the engines the mass, and therefore the force needed, will be exactly the same

My first Idea was to build the engines and fuel tanks as a self contained unit, The Cargo and crew quarters will be a separate ship that is pushed in front of the Engines by electro magnets. Does this design have any feasibility? will pushing the bulk by magnets relieve any of the burden of mass on the engines or will the mass be the same even though there is no physical connection between the engines and the cargo and crew vessel?

Doesn't matter how the ship is held together; metal, magnets or magic the mass is the same and so the engines have to do the same amount of work.

The other idea was to build it Tie Fighter style, with the Bulk of the ship being built flush with the Engines so that there is nothing being pushed in front of the engines or being pulled behind them. would this be more fuel efficient then pushing the bulk of the ship in front of the engines?

Nope, see above. Long story short there aint no such thing as a free lunch. At the end of the day accelerating X mass to Y velocity is going to require the same amount of energy no matter how you assemble the parts (all else being equal).