Interstellar spacecraft design.

[Nova Andromeda]

--Since Stormbringer can't figure out how determining what systems an interstellar ship might have relates to the viability of bio. ships I've created a new thread. BTW, if other posters would have made this statement earlier "... in a thread about technical viability ... If you cannot produce at least some sort of theoretical explanation of how it might be done, then you've got nothing." (my emphasis) a lot of wasted time would have been avoided. The old thread is here:
http://pup.phpwebhosting.com/~mrwong/vi ... ca6c5a828f

--The first thing to do is design an interstellar spacecraft. Once that is done it will have to be optimized. We can then calculate the flight time. This will allow for the design of the life support/repair system. There are two things I believe will need to be done: replace as much metal as possible with lighter elements and make the systems as mass efficient as possible.


Here is a copy of my initial design suggestion:
-At any rate, I would now like to discuss building an interstellar ship using forseeable tech. advances with the goal of colonizing another system. I will then think about what components that might be replaced with biological stuff and see if it is worth the trouble. My "expertise" is not in material sciences, engineering, or manufacturing (and I'm sure you will argue it is not in anything useful) so I will need to draw heavily on some resource to make up for it. Hopefully, someone will provide me with or point me to that resource.
-My initial thoughts on the ship are thus. It will need 6 general systems which are a drive, a power source, a life support and repair system, a structural "system," navigation system, and communications system. For the power source I was thinking of a fission reactor (grossly inadiquate to attain a sig. fraction of c I think so it will be slow going). For the drive I was thinking of an initial booster rocket and a particle accelerator (i.e., ion drive) for the long haul which could throw spent uranium and/or other heavy metals. I was thinking one could make the structure out of carbon composites, but perhaps metal is required. I have no idea what the optimal navigation or communication systems are. Perhaps a laser for communication and radar for navigation?





Darth Wong's response was this:
Nova: "At any rate, I would now like to discuss building an interstellar ship using forseeable tech. advances with the goal of colonizing another system. I will then think about what components that might be replaced with biological stuff and see if it is worth the trouble. My "expertise" is not in material sciences, engineering, or manufacturing (and I'm sure you will argue it is not in anything useful) so I will need to draw heavily on some resource to make up for it. Hopefully, someone will provide me with or point me to that resource."
Darth Wong: "Biological stuff would be useful for growing food and helping the colonists on their long journey. It would not be useful for the structure of the ship, its control systems, or its key technologies such as propulsion.

Nova: "-My initial thoughts on the ship are thus. It will need 6 general systems which are a drive, a power source, a life support and repair system, a structural "system," navigation system, and communications system. For the power source I was thinking of a fission reactor (grossly inadiquate to attain a sig. fraction of c I think so it will be slow going)."

Darth Wong: "Nuclear fusion is generally considered a "foreseeable" technology."

Nova: "For the drive I was thinking of an initial booster rocket and a particle accelerator (i.e., ion drive) for the long haul which could throw spent uranium and/or other heavy metals. I was thinking one could make the structure out of carbon composites, but perhaps metal is required. I have no idea what the optimal navigation or communication systems are. Perhaps a laser for communication and radar for navigation?"

Darth Wong: "All well and good, but so far, nothing organic is required or even remotely useful. This would not be a bio-ship. This thread asks a simple question: is a bio-ship viable? Why do you expend so much effort trying to drag the thread away from that question, rather than simply admitting that the answer is "no", which both you and I know to be the only correct answer? A totally inorganic ship with a hydroponics lab onboard is obviously not a "bio-ship", and any attempt to shoe-horn some kind of minor bio-tech into an inorganic starship would not affect the basic question: are bio-ships viable?"



--I will need to lookup the energy output from hydrogen fusion, hydrogen density in interstellar space, and would like input on how one could collect interstellar hydrogen and how effecient a power plant could be. Basically, there are two choices for this type of drive: ride a controlled nuclear explosion or use it as a standard power plant in combination with another drive type.

[The Dark]

<snip>
--I will need to lookup the energy output from hydrogen fusion, hydrogen density in interstellar space, and would like input on how one could collect interstellar hydrogen and how effecient a power plant could be.

You're talking about using a Bussard ramjet (or ramscoop). Most likely not feasible, since it requires a vessel traveling 6% of c to reach break-even on fuel capture/expenditure, and a field strength of over 10 million tesla for an unmanned vessel (said field strength is also highly lethal). Also, it would have a huge field size, at least 30,000 kilometers long, making it impossible to use while in orbit (it would nearly reach from geosynchronous orbit to Earth's surface).

Basically, there are two choices for this type of drive: ride a controlled nuclear explosion or use it as a standard power plant in combination with another drive type.

Look up Project Orion and Project Daedalus. Both used nuclear power in rather unique ways.

[XPViking]

Project Daedalus. Wasn't that the one that Clint Eastwood, Tommy Lee Jones, James Garner, and Donald Sutherland were working on?

XPViking

[Stormbringer]

As Mike said, inorganic technologies have far outstripped any biotech. We can build a colony ship with out them.

The Project Orion idea remains one of the best ideas for a long ranged colony ship. It's effective and powerful enough to do the job. Any trip would definetly a slow boat.

In my opinion a space ark is probably what we'll see. A massive ship on a multi generational voyage. The need woulld be house a large enough population large enough to be genetically viable for those generations and for a new planet.

And again, no bio tech is required or desireable.

(And I closed the previous thread because you refused to debate the issues and kept evading. Bitching about it won't do you any good)

[The Dark]

As Mike said, inorganic technologies have far outstripped any biotech. We can build a colony ship with out them.

The Project Orion idea remains one of the best ideas for a long ranged colony ship. It's effective and powerful enough to do the job. Any trip would definetly a slow boat.

I agree. Without some suprising innovation in technology, Orion holds the best probability of success for a moderately quick slow boat. The main problem will be getting people to overcome their knee-jerk fear of the word "nuclear". As much as I like solar sails, they're useful only in-system, and only out to about Jupiter before becoming slower than chemical drives.

[Nova Andromeda]

--Well I've done a few calculations based on what I've found. Here they are:

24.89 MeV Deuterium fusion / He atom
1 yr = 3.1557x10^7 s
5 ly = 4.7335x10^16 m
flight time = 100yrs
1,000,000 kg starship

Fussion energy = 3.987x10^-12 j / He = 2.400x10^12 j / mol. He = 6.00x10^11 j / g H
100 yrs --> 1.500x10^7 m/s avg. vel. --> const. acc. to 3.000x10^7 m/s --> acc = 1 m/(s^2)
eng. for acc. = 4.500x10^20 = 7.5x10^5 kg H

--You will note that if these calculations are correct the mass of feul hydrogen is nearly as large as the mass of the ship. In addition it assumes fusion, energy transfer, and the starship drive are nearly 100% effecient plus it neglects the mass of the feul. Therefore, we are going to need to reduce the mass of the starship by at least 3/4, use a very efficient power plant and engine (tokamak attached to particle accelorator where only He can escape the magnetic containment feilds?), and find and inventive way to stop (perhaps collect interstellar H somehow since max speed will be 10% of c).
-Since the mass of iron is 56 while carbon is 12 and the acceloration is only 1 m/s it would be wise to replace all the sturctural stuff with carbon composits / plastics. We can replace wiring with either fiber optics for communication and perhaps conjugated carbon polymers for electronics.
-Well that is all I've thought of for today...

[Knife]

M2P2. Using plasma to expand a magnetic field, wich will act as a solar sail. No moving parts for wear and tear, but will have to bring along a power source and fuel. If fussion is alowed in this senario, then it would be powerful enough to make plasma and maintain a magnetic field to make a "sail" with. Also, a plasma engine could be used to intitialy accelerate the craft, then kick into idle for the M2P2.

If people are going to be traveling for a few years in these things, then some type of artificial gravity will be needed or when they get to the new planet, no one will have any strength left in their legs to stand on the planet.

Tanks of Oxygen and Hydrogen to use as fuel and breathable air, and to make water with, as well as possibly use as fuel for a power cell for secondary power that would be needed.

Navagation could/would be handled with the use of passive sensors keeping track of "local" stars and comparing that to a computor model of the same to determin the location. Communication would/could be handled by laser communication with perhaps a couple of M2P2 capable drones that could be sent back to Earth with recorded info.

Just a few thoughts(IMHO)

[Enlightenment]

Nova Andromeda:
I'm not sure what method you're using to come up with those numbers but they don't look right. With fusion drives a 1m/s^2 sustained acceleration AFIAK should be damn near impossible unless the mass ratio (ratio of fuel mass to payload) is >1e6 or so....

The right math for this kind of thing is the relativistic rocket equation.

Code: Select all

v = u ln rho/[1 + (u^2/c^2) ln^2 rho]^(1/2)

Where
v = velocity
u = exaust velocity
rho = mass ratio

Plug in a desired velocity, take the known exaust velocity for fusion drives, then solve for rho. This is left as an exercise for the reader.

[Nova Andromeda]

--I'll take a look at your equation, but the assumption was that you could pump all your fusion energy (from the tokamak) into a particle accelortor and send the exhaust out at high fractions of the speed of light. I may have botched the calculation though since I didn't spend much time on it.

[Enlightenment]

--I'll take a look at your equation, but the assumption was that you could pump all your fusion energy (from the tokamak) into a particle accelortor and send the exhaust out at high fractions of the speed of light. I may have botched the calculation though since I didn't spend much time on it.

That would only be a valid approximation for a reactionless drive ('gravetic' or what have you) in situations where the fuel mass is trivial compared to the payload mass. In more complex (read: real world) situations the rocket equation has to be used because it models realistic reaction drives and takes into account the fact that the mass of the spacecraft will decrease--by orders of magnitude--as fuel and reaction mass are expended.

For non-realtivistic situations there's a simpler rocket equation in the form v = u ln (rho). While this is obviously much easier to work with it isn't as useful for interstellar rockets as it doesn't take relativity into account and as such breaks down at around 0.1c or so.

[SWPIGWANG]

Oh well, here are my two cents.

Bringing energy sources with you is stupid.

*builds laser sail with magnetic sail build in to slow down using solar wind of the destination system*

I've read about an interesting idea on using a laser at home system to super heat fuel on the starship into exhaust, thus doing away with the reactor and fuel, leaving only remass on the ship while being much faster than a laser sail in terms of acceleration. Does anyone have any more information on this?


Anyway, biological system probably wouldn't be necessary, and when the technology is at that level, desired.

[aerius]

-Since the mass of iron is 56 while carbon is 12 and the acceloration is only 1 m/s it would be wise to replace all the sturctural stuff with carbon composits / plastics. We can replace wiring with either fiber optics for communication and perhaps conjugated carbon polymers for electronics.

Atomic mass numbers do not translate into the actual mass of the material. For example iron is 56 and aluminum is 28, but if you were to take equal size cubes of both materials the iron block would be 3 times heavier. Carbon fiber laminates depending on the epoxy used and fiber percentage are roughly 1/4 to 1/5 the density of iron.

The problem with carbon fiber is that to make them strong in all directions you have to do a funky layup pattern on the layers of fibers, and this really drops down the overall strength of the part. They're really good for parts that don't undergo complex stress patterns, if a CF part only needs to bear loads in one or 2 directions it can be half the weight of a steel part of the same strength.

Other downsides of CF are that the epoxies used to hold the fibers together tend to get degraded by radiation. In the early days UV rays would cause premature part failures, they've got that fixed now but I don't know how well they'll stand up to the x-rays or gamma rays found in space. The main problem I see is notch sensitivity and fracture propagation. Put a nick in a carbon fiber part and it'll soon grow into a nice crack and snap when you stress it. Which leads to repair, if a CF beam for instance snaps in half, it's gonna be a bitch to put back together, while with a steel one you could easily weld it back together. Patching holes in a CF hull ain't gonna be fun either, cause whatever made that hole will also leave fractures all around it, kinda like the way safety glass "spiderwebs" when it gets a hole shot through it.

The way I see it the hull and all exterior parts will be a high strength metal of some kind, probably steel or titanium with carbon fiber support beams and spars on the inside. Computers and communications could indeed be switched to fiberoptic connections, it'll cut down on interference for one thing, but power systems will likely need good old metal wires. Perhaps they might be superconducting wires if the technology gets to the point where we can make them practical.

[Nova Andromeda]

--Sounds like carbon fiber stuff has some serious problems, but that wasn't unexpected. First I'm not sure the hull needs to be high strength metal since this won't be a combat ship and anything of large size we run into once the ship is at high speeds is going to punch right through the ship anyhow. The front of the ship will need to have a strong coating of some sort of radiation absorbing material like lead covered in turn by something to absorb hits from space dust without emitting undo amounts of radiation. Second, the power systems could be switched to conjugated carbon polymer. These polymers are considered a forseeable tech. and due to the delocalized pi orbitals it should conduct very effeciently. So long as the part doesn't need to withstand high temp. or radiation it should work just fine.

[Darth Wong]

--Sounds like carbon fiber stuff has some serious problems, but that wasn't unexpected. First I'm not sure the hull needs to be high strength metal since this won't be a combat ship and anything of large size we run into once the ship is at high speeds is going to punch right through the ship anyhow.

Then you need a rigid space-frame of some sort. Unless you picture this as some sort of balloon floating through space with objects loosely secured inside, you need some way of maintaining rigidity, and carbon fibres/nanotubes aren't the best way to do that.

Second, the power systems could be switched to conjugated carbon polymer. These polymers are considered a forseeable tech. and due to the delocalized pi orbitals it should conduct very effeciently.

What difference does that make? Are you projecting copper wiring to make up a significant fraction of the mass of the vessel?

So long as the part doesn't need to withstand high temp. or radiation it should work just fine.

How do you plan to include a nuclear reactor if you avoid all materials which can handle high temps or radiation?

[SWPIGWANG]

[insane]

Unless you picture this as some sort of balloon floating through space with objects loosely secured inside, you need some way of maintaining rigidity, and carbon fibres/nanotubes aren't the best way to do that.

Maybe you can make into a tension structure by rotating the spacecraft of something.
[/insane]

[Knife]

--Sounds like carbon fiber stuff has some serious problems, but that wasn't unexpected. First I'm not sure the hull needs to be high strength metal since this won't be a combat ship and anything of large size we run into once the ship is at high speeds is going to punch right through the ship anyhow. The front of the ship will need to have a strong coating of some sort of radiation absorbing material like lead covered in turn by something to absorb hits from space dust without emitting undo amounts of radiation. Second, the power systems could be switched to conjugated carbon polymer. These polymers are considered a forseeable tech. and due to the delocalized pi orbitals it should conduct very effeciently. So long as the part doesn't need to withstand high temp. or radiation it should work just fine.

Using flexible materials for a framework might work well, but the outer hull should be somewhat durable to handle the strain of acceleration and such.

Using good old moon dirt, packed between a double hull would work well for radiation shielding(you just need a dense material to absorb the radiation right?). Also a magnectic field around the ship would also help with the radiation, hence another good point of the M2P2 system.

[SWPIGWANG]

M2P2????

[Nova Andromeda]

Darth Wong: "Then you need a rigid space-frame of some sort. Unless you picture this as some sort of balloon floating through space with objects loosely secured inside, you need some way of maintaining rigidity, and carbon fibres/nanotubes aren't the best way to do that."
-What are the lightest materials you think we can get away with? Perhaps the main frame should be titanium with other structural stuff being carbon fiber or plastic?

Nova: "Second, the power systems could be switched to conjugated carbon polymer. These polymers are considered a forseeable tech. and due to the delocalized pi orbitals it should conduct very effeciently."
Darth Wong: "What difference does that make? Are you projecting copper wiring to make up a significant fraction of the mass of the vessel?
-I was thinking that the wiring needed for ships systems would be quite heavy. Aren't electromagnets on the particle accelorator and the tokamak reactor made out of copper wiring? I'm sure there is also a lot of other wiring in those things too. What do you project to take up the most mass in the starship (component wise) besides the light element stuff (which is probably as good as it is going to get)?

Darth Wong: How do you plan to include a nuclear reactor if you avoid all materials which can handle high temps or radiation?
-I was planning to have the reaction chamber heavily sheilded (I see no way around that). However, outside that sheilding things should not be so destructive. Then again I'm not an engineer so you tell me what we can replace with lighter materials if we use heavy sheilding and good cooling systems. I would also like to know how a tokamak is going to handle the imense amount of electromagnetic radiation produced from fusion and how that energy can be harnessed efficiently.

[Nova Andromeda]

M2P2 is a solar sail system:
http://www.geophys.washington.edu/Space ... odel/M2P2/

--From an initial glance I don't think it will be useful once we leave the solar system.

[Knife]

M2P2????

Micro Magnetoshpere Plasma Propulsion. Basicly plasma is used to "inflate" a magnetic field out, and the field acts like a solar sail.

[Knife]

M2P2 is a solar sail system:
http://www.geophys.washington.edu/Space ... odel/M2P2/

--From an initial glance I don't think it will be useful once we leave the solar system.

Damn, just looked up the site, but yeah thats the one. AFAIK, the solar winds extend out of the "solar system" and besides, as long as the ship accelerates to the proper(what ever that is decided to be) speed before the solar wind becomes to weak to be useful then it would be very practicle.

[Nova Andromeda]

--The solar wind is going to be totaly inadaquate to accelerate the spaceship to .1c=30,000,000m/s. The reason is that it only travels at 800,000m/s. However, perhaps it would be useful to capture it as fuel.

[SirNitram]

The problems I can immediately see are the great wars between 'Take it with you', IE, a fusion reactor powering either a fusion or ion engine system, and 'On the go', the Solar-Sail and Ramscoop side.

The problem I see is the scale the scoop or sail will get rapidly out of hand once the main vessel's true size becomes apparant. These are, by necessity, generation vessels. You need an internal rotating section to provide gravity, which must hold food production, living quarters, etc. Worse still, you must realize that this isn't simply a scaled up Space Shuttle. You have to include all the vestiges of a city. For flights to other stars, there will be people who grow up knowing only the inside of this tin can.

The psychological effects of such are pretty strong(Something I try to explore in my writings), especially when those 'spaceborn' get to their rebellious years.

And while I think about how I can do the numbers for all this, I remember an article on preparing for an AM/M engine.. Just need alot more time to gather the fuel.