This is the larger project I was talking about...

[tvdoug]

RFC, please...

http://64.226.117.158/dougimages/newshiportho.jpg

http://64.226.117.158/dougimages/newship1.jpg

http://64.226.117.158/dougimages/newship2.jpg

http://64.226.117.158/dougimages/newship3.jpg

http://64.226.117.158/dougimages/newship4.jpg

Looking to add some sort of cargo/workbug bay, and a ton of textures... more to do, as always.

-Doug.

[p.s. Cargile]

Certainly interesting.

[Elowan]

Big and utilitarian. I like it! :)

[tvdoug]

Thanks, Elowan. I tried to stay within the realm of Science Fiction (the true definition of which is, in brief, fiction based on actual science possibility, as opposed to Science Fantasy) when designing this beastie. To that end: Standard combustion engines; rotating section to simulate gravity, and simple working tools (see the 'workbug' thread, this forum) that are possible designs, based on current science fact.

I'll be happy to say that, compared to some other designers/artists on this board, I'm verymuch a n00b when it comes to LW. The basics of design? Got that. Now, I've got to learn more about textureing, as well as the different techniques involved there. Not to mention particle systems, and all those fun toys.

With your patience, I'm gonna keep on keepin' on...

thanks,

-Doug.

[p.s. Cargile]

We have simular ideas. I posted work last year on an Interplanetary Transport, of which I recently revised. Seperate rotating sections seem like a good idea, but they too have their inherit problems. If one section rotates while another does not, how is data, power, and environment shared between sections? Or, if one section rotates while others do not, how are the counter rotational forces (such as experienced by rotor craft) balanced? And the main problem, if a ship is to spend most of its travel time accelerating and deaccelerating, how does these forces affect the centrifugal forces of the rotating sections?
If these problems make you shrug, then its best if your designs are rooted in a future far enough where we can invoke fantastic technologies that utilize inertia and gravity control. I myself have opted for a microgravity enviroment with a module with a controlable "hamster wheel" for artificial gravity. But even such a chamber needs a mechanism for canceling out counter rotations, which I believe is an engineering possibilty. A ship that rotates all the time is physically desirable, but has the problem of continuos communication lock.
Although it's good to create a ship that is cool, it's a challenge to create a ship that's true to science and economy.

This is a cool ship, but I challenge its verasity in our near future.

[tvdoug]

Hrm. Good comments. My responsed:

Re/ rotational sections:

First off: the rotational section would be used for leisure and rest, principally. Power and communications needed in this section would include only the basics (intership, basic electric, and the like). Plumbing for water could even be done using a system of connectors designed for that purpose). As this would be a closed system, the 'plumbing' or water systems (including waste processing, hydroponics, filtration and storage) might be entirely self-contained within the rotational section of the ship.

Second: Counteracting the rotational force of this larger section could be done through the use of smaller, heaver sections in the 'core' of the ship, spinning at greater speeds, and in opposite directions. Essentially, a smaller flywheel system that would counteract the rotation of the larger section. (Of course, this would add to the overall mass of the ship, and have to be taken into account with the propulsion needs, etc.)

Finally, I imagine that, during either acceleration or deceleration stages (and, as you correctly point out, that might be the entire trip), the ship would be using engines almost constantly. However, I choose to analyze those forces this way:

Take the design that I put together - and put it on it's feet - stand it on the engine bells, on Earth. Where's the force? Downward, of course, gravity takes care of that. Now, looking at the structure needed to keep this ship together, it's easy to see that the rotational section of the ship simply 'hangs' on the 'trunk' of the ship, like a treehouse, wrapped around the trunk of the tree.

Looking at it that way, then the only reinforcement of structure would be toward the back of the spinning section, akin to the kind of structure that is used with a merry-go-round...

I hope I'm making sense. Tonight (when I get home), I'll look again at the model, and perhaps post something to explain this better.

In regard to the feasability of this design, I quite agree that it'd be a LONG time before any one or any organization on Earth might have the resources to do something anywhere near ambitious. However, to dream is the first step. To imagine that the possible is practical allows us to find a direction, and set goals. That's the intention of what I'm doing here -- Dreaming of such a fantastic possibility, not producing construction documents.

Finally, thank you for your comments! Frankly, you've made me look a little closer at the basic physics of such a design, and that can only improve the design down the road. It's always nice to know that folks are looking at one's work and thinking about it.

Cheers,
-Doug.

[Sean Kennedy]

tvdoug,

I like this concept alot, although I would add more nunies and plating detail.

:)

[tvdoug]

Sean:

Thanks for your comments; I've yet to even begin to texture this beastie; Hoping to do some work on it this weekend (check back for updates!). I've also got a HUGE gap in the design - that big blank spot just behind the rotating section in the front - that's yet to be worked on; specifically, I'm planning some sort of work-bay, akin to the 'pod-bay' of 2001 fame; I'm also planning on some sort of command-capsule at the head of this whole thing, but I've not yet decided on a design that I like.

In terms of physical details ("nurnies"), I'm pretty happy with what's there so far (on the finished sections of the ship, that is). Can you offer ideas that I can incorporate?

This really is a flexible project, one that is growing and changing as it proceeds. I'm terrifically pleased with the input being provided by the group - thanks to all for it!

-Doug.

[p.s. Cargile]

I think the structural intergrity is fine.
A rotating habitat will have a downward force towards its floor, or in reference to the ship as a whole, outward from the sides. If the ship accelerates at .5 g, it excerts an added downward force towards the engines. With these two forces at work in the rotational section, how will it effect a person trying to walk? I understand that acceleration forces would be much less that .5g, and even at such a rate, rotational artificial gravity, wouldn't be needed. At considerable less acceleration, a person might feel a little bit of a tug toward the aft wall of the rotational section, but still be able to walk. A game of catch would be interesting.
A ship that has acceleration and centrifugal forces also determines the internal layout. If there is enough acceleration to hold a person to surface of the room perpendicular to the direction of thrust, then that surface should be the floor. Which means floor plans would be arranged like a building. Especially if the ship can accelerate up to an eighth of a g and give Moonlike gravity.
I admit that currently I'm not familar with feasible acceleration rates for various types of propulsion, but these are points I've considered in my own design.

[tvdoug]

You hit on one of the concepts that I was mulling over last night:

If this ship is designed for point-to-point transport, and I'm relying on Newtonian physics as a reference, *and* the ship will be either accellerating or decelerating the entire journey, then the 'gravity' force would come from the force of acceleration; as you said, the floor plans would be arranged like a building (perpendicular to the axis of the ship).

I'm not sure that I'm going to go with that model: I'm going to assume a few things:

The ship has hard acceleration at the beginning of the journey, then hard deceleration at the end, using the main thruster for both.

The ship, once 'up to speed', will coast to it's destination, and there will be no force of acceleration upon the ship or it's contents.

Finally, using current space exploration as a model, and using those same relative speeds and transit times, I'm going to assume that this ship might make a quick journey to the moon (transit time measured in hours) or a longer trip to Mars (transit time several months). Therefore, on the longer trips at least, to prevent atrophy of muscles, a gravity simulator will be beneficial, if not necessary.

I'm also going to assume that there is some sort of 'inertial battery' that can store the rotational momentum of the habitat in a smaller, more compact package that would affect the ship's operation and navigation far less.

I'll have to do more research on this part. :) Time to take the old synapsies out for a walk.

(High school physics formulae are coming back to me ... mv2/r... f=m*v... :)

-Doug.

[Elowan]

Originally posted by p.s. Cargile
I admit that currently I'm not familar with feasible acceleration rates for various types of propulsion, but these are points I've considered in my own design.

I'm given to understand that a sustained acceleration of 1 G would eventually kill everybody aboard. The operative word here is 'sustained' meaning over a prolonged period of time.

[Proximo]

Wouldn't a sustained acceleration of 1G be just like living on earth?

[tvdoug]

Hrm... that's my impression, Proximo; unless what Elowan is referring to is a a sustained acceleration of 1G in a non-vertical direction -- say if your in a chair, and the force came at you, and pressed you backward -- or 1 G in addition to standard gravity...

Not sure... :/

[Elowan]

Originally posted by Proximo
Wouldn't a sustained acceleration of 1G be just like living on earth?

No - I'm taking about constant acceleration:

The gain in velocity of a body undergoing constant (non-varying) acceleration over its velocity at zero time increases in proportion to the time elapsed:

v(t)-v(0)= at,

where v(t) is the velocity at time t, v(0) the velocity at time zero and a the accleration.

It should be noted that v and a are vector quantities.
The displacement, s(t) - also a vector, of the same body increases in proportion to the square of the time elapsed (in addition to a contribution due to its initial velocity):

its initial velocity):

s(t)-s(0)=v(0)t+1/2 at2

There is a third "rule of motion" that can be found be eliminating time from these two equations:

v(t)2=v(0)2+2a.s

Unlike many aspects of physics, these rules can be derived without resorting to calculus:

(the following is conducted in one dimension, but can easily be extended to as many dimensions as desired)

If an object is undergoing constant acceleration a, then its average acceleration must also be a.

a=(v(t)-v(0))/t

Rearranging slightly:

v(t)-v(0)=at

Now, we can also define the average velocity, vave:

s(t)-s(0)=vavet or, vave=(s(t)-s(0))/t

but, as the acceleration is constant, the velocity increases linearly. In this case, there is another simple formula for the average velocity:

vave=(v(0)+v(t))/2

Combining these two equations:

(s(t)-s(0))/t=(v(0)+v(t))/2

Now, substituting in the equation for v(t) we just found: (s(t)-s(0))/t=(v(0)+v(0)+at)/2

or

s(t)-s(0)=v(0)t+1/2at2.

Rearranging the velocity equation allows us to arrive at an expression for t:

t=(v(t)-v(0))/a.

Substituting this into the displacement equation yeilds:

s(t)-s(0)=v(0)(v(t)-v(0))/a+1/2a(v(t)-v(0))2/a2

s(t)-s(0)=v(0)v(t)/a v(0)2/a+1/2(v(t)2+v(0)2-2v(t)v(0))2/a

Carrying the algebra further reveals that the v(0)v(t) terms cancel. Tidying up yields:

v(t)2=v(0)2+2as

The SI unit for acceleration is m/s2 - an object that is accelerating at 1 m/s2 will increase its instantaneous velocity by 1m/s every second.

Gravity and acceleration are not the same thing. Gravity produces uniform acceleration:

Since we are dealing with uniform acceleration, we can use the simplified constant acceleration formulas. By combining and rearranging these equations, we will be able to extract the velocities we need to calcltae a value.

v2=v1-g(t2-t1)
x2=x1+vave(t2-t1)

taken from the Encyclopedia of Physics

:nuts:

[tvdoug]

Hrm. You've COMPLETELY lost me there; formulae in too large of groupings are like notes of music -- I can follow a simple one line melody, but too much thrown at me at one sitting leaves me babbling like an idiot. :)

However, I can state this:

A human body will experience some force ("Gs") if it is being carried along with a vessel that is accelerating. Now, assuming that the vessel's relative speed is increasing a fixed rate (let's say 9 meters per second per second - after one second it's going 9 m/s, after two seconds, it's going 18 m/s), then I would surmise that the force experienced on the human in that vessel must be equal over the course of that acceleration.

Taking a look at your last post, you actually presented this equation in reverse:

"Gravity produces uniform acceleration"

or:

"Uniform Acceleration feels like gravity."

SO:

If my increases it's speed so that it's instantaneous speed, when analyzed, follows the same curve as that of Earth Gravity, then the acceleration force experienced by individuals within that ship will FEEL like gravity to them.

Yes?

[p.s. Cargile]

I've never heard of Elowan's presumption in any reputable source about space exploration, and propulsion. Now if Elowan could turn that math into an English example, I might could follow it. The only way I can image acceleration to become fatal, is if the rate increases so that 1g becomes 2g become 4g, ect. until the body is unable to cope with the stress.

[Elowan]

Originally posted by p.s. Cargile
I've never heard of Elowan's presumption in any reputable source about space exploration, and propulsion. Now if Elowan could turn that math into an English example, I might could follow it. The only way I can image acceleration to become fatal, is if the rate increases so that 1g becomes 2g become 4g, ect. until the body is unable to cope with the stress.

I realized that I put my foot in it when I made my original statement. I put forth something that I had read in a physics or aeronautical journal some years past in reference to acceleration. In a constant acceleration environment the thrust against the human body would continue to increase as the acceleration ... well ... accelerated until it was incompatible with life.

Whereas a uniform acceleration is non-varying (as I understand it).

My point is that this condition - if correct - would require a re-thinking of the environment within a spacecraft so as to minimize acceleration effects given the conditions described.

As for 'reputable source' - we haven't defined what that term means in the first place. In my 45 years as an eye surgeon involved in medical research - I've heard that phrase bandied about in an attempt to discredit an author's thesis - but I digress.

I will leave it at that and will make a concerted effort to unearth the source of the concept I originally stated and give a reference - since the gauntlet has been thrown down.

In the meantime - I guess you can paint me as a 'crackpot'. :nuts:

[tvdoug]

Don't worry -- I think that there's at least a few posting here who may have received a title similar to that of 'crack-pot' (myself, for one, at least); and there are volumes of historical accounts of those who also received titles akin to 'crack-pot' over time: Wright Brothers, DaVinci, Goddard, Sagan, Einstein... just to name a few...

You're in good company... Enjoy it! :)

[p.s. Cargile]

Well, I'm not making any challenges that you're wrong Elowan. I've never heard of this before and I like to find the facts.

I have found an interesting website: The Architecture of Artificial-Gravity Environments for Long-Duration Space Habitation (http://www0.arch.cuhk.edu.hk/~hall/ag/Dissertation/FrontMatter.htm)

[Enlightenment]

Visually, this mesh is pretty good, but since you guys are getting into hard physics design issues...

There is a problem with the size of the fuel tanks and the type of propulsion used. Getting to Mars or the Moon from low Earth orbit with a chemical drive requires that 4/5ths of the ship (by mass) be fuel. Switching to a solid-core fission drive reduces the fuel requirements to 1/2 by mass but the result is still very much a ship that's made of fuel tanks with a extras attached here and there. A nuclear salt water rocket can have the necessary performance to work with a ship that's less than 50% fuel, but NSWR is extremely expensive and very dangerous.

Boost-coast-boost is the right flight model to be looking at. 1G constant acceleration is a very hard problem. While it won't kill the crew (1G is just the same as standing on Earth), the only propulsion technology capable of sustained 1G is antimatter and even then the fuel requirements are awful.

In terms of structure, spacecraft are mass limited; every KG of mass in structure is one KG less payload and requires many KG of fuel to move around. For a commercial cargo ship, less cargo and more fuel means less revenue. Along these lines, it would make more sense for the rotating module to be much smaller (the crew is the only thing that needs to be spun, after all) and made of one continous ring rather than a set of segments.

A biggy here is the lack of radiators. Heat rejection is a big issue for high-performance spacecraft. A few radiators, or booms for liquid radiators, would not be out of place.

[Elowan]

Originally posted by p.s. Cargile
Well, I'm not making any challenges that you're wrong Elowan. I've never heard of this before and I like to find the facts.

I have found an interesting website: The Architecture of Artificial-Gravity Environments for Long-Duration Space Habitation (http://www0.arch.cuhk.edu.hk/~hall/ag/Dissertation/FrontMatter.htm)

Not to worry and no offense taken. Sometimes I get my back up but not good for me. :blush:

Thanks for that URL BTW.:)

[p.s. Cargile]

Very good points Enlightenment. And it reminded me to introduce the most likely propulsion system used to get to Mars and beyond in the later decades, and that jem is the VASIMR or Variable Specific Impulse Magnetoplasma Rocket.

http://www.nasa.gov/vision/space/travelinginspace/future_propulsion.html

That website gives a general overview. Use the search engine to get to the more detailed .pdf files.

This engine is, in my opinion, the best economic propulsion system that any hard s-f designer could hope to employ. And it does need nuclear electric reactors to power the engines. Once this engine is tested and proven, it will replace spaceborne propulsion systems.

[Enlightenment]

Originally posted by p.s. Cargile
This engine is, in my opinion, the best economic propulsion system that any hard s-f designer could hope to employ.

That's probably overstating the case a little. :) VASIMR is a neat gizmo that has a lot of near future uses but it's fundamentally a low power, low thrust drive. While this is fine for probes, moving people or cargo requires more of a push than VASIMR can give.

At present there is no one drive that's ideal for all mission profiles. Some drives are much better suited to some missions than others. VASIMR's niche is low mass, long-duration flights. Heavier real-life loads, such as for instance a 6 person Mars mission, require nuclear thermal drives (e.g. NERVA or DUMBO) for acceptable trip times. Extremely heavy loads are in the domain of Orion, Zubrin's NSWR, and the various gas core nuclear systems. For sublight interstellar, the only games in town are ICF, antimatter, and beamed power.


In addition to the site you mentioned, another good websites to read for information on real-life space propulsion in general is
http://www.projectrho.com/rocket/index.html

There are a few other resources on my webpage at http://www3.telus.net/csbh

[Elowan]

Just when I decided to utilize a form of Ion Propulsion!

Oh well! :what:

[p.s. Cargile]

The usefulness with the VASIMR is that the exhaust can be modulated for optimal use at all mission profiles and varying gravity fields. It can operate at hight thrust for rapid acceleration, or at lower rates. It's considered for human Mars missions because it is a system that can get there the quickest. All of propulsions systems have fixed specific impulses, operating at either full throttle, or no throttle.

[Elowan]

You know what I'd like to see in this thread?

More pictures and less palaver. :drevil:

[tvdoug]

OK, Elowan, let me see if I can oblige:

I've taken a listen to some of the concepts discussed in this thread, and did a major rebuild of this design. It's basically still the same concept; however:

The rotating section has a much lighter look to it (in response to the comments about mass vs. propulsion); that section is also only a single floor around the edge (in response to something I read about the incredible difference between centripetal force vs. distance from the axis);

The overall body of the ship is much smaller, and the design of the hub is also much leaner, relying on a 'suspension' type of getup.

Finally, the engines remain as they were, but a rebuild there is also planned.

The only concepts I could not find (and therefore could not incorporate)
had to do with heat dissipation, or heat radiators. What would one look like? A heat-sink? large fins? I can't image it's that simple...

Anyway, here's a few images:

http://64.226.117.158/dougimages/031102-1.jpg
A Shot of the whole beastie from aft; as you can see, some preliminary texturing has been done -- the entire ship is much darker than it was before...

http://64.226.117.158/dougimages/031102-2.jpg
A shot of the centrifuge, looking across the span; The four columns connecting the hub with the ring are about 1.5 m in diameter, and are meant to provide access to the ring from the hub...

http://64.226.117.158/dougimages/031102-3.jpg
Finally, a shot looking aft through the spokes.

Nebula and starfield are mine, as well, FWIW.

RFC, of course. Thanks,

-Doug.

[Enlightenment]

Originally posted by p.s. Cargile
It can operate at hight thrust for rapid acceleration, or at lower rates.

High thrust being a relative term. VASIMR thrust tops out at about 1500 newtons, which works out to being able to accelerate 1000kg at 1.5m/s^2. While this is much better than an ion drive, it's not in the same league as NSWR or Orion.

[Enlightenment]

Originally posted by tvdoug
I've taken a listen to some of the concepts discussed in this thread, and did a major rebuild of this design.

Really nice. I like where you're going with this.

Maybe boost the brightness a bit, particularly in the second shot. It's hard to see the ship's structure. Lighter colors are also desirable for thermal management--white paint reflects heat.

Have you settled on a scale for this ship yet? The smallest radius one can barely get away with for a rotating section is 20 meters. Any smaller will require rotation rates higher than most people can tolerate and/or very, very low levels of fake gravity. In contrast, the smallest radius that's workable for full Earth gravity is 100 meters.

As for radiators, here is a render of a semi-engineered hypothetical exploration craft. The radiators are the large panels on each side of the structure. They basically look like solar arrays, except they're thicker.

Note: this render is not mine.
http://ffden-2.phys.uaf.edu/213.web.stuff/Scott%20Kircher/AIMStar1.jpg


As a final nitpick, the stars and nebula wouldn't be visible in real life as they're much too dim to be captured in the same frame as a bright object like a ship, planet or star. A flat black background would be dead boring but physically accurate.

[mboeller]

tvdoug;

You should just try to use the MiniMag Orion drive system for your spaceship cause IMHO this is the engine of the future ;). This form of propulsion is already in preliminary development, has an high specific impulse ( up to 25.000 sec ) and an very high thrust like the original Orion concept from the 60th's. You can find good pdf about the MiniMag Orion engine at http://www.andrews-space.com/. Here is the direct link for the PDF : http://www.andrews-space.com/en/news/Pub-MiniMagOrion(200307).pdf

[Elowan]

Looking good.

[tvdoug]

Thanks for the resources, mboeller, and the image, Enlightenment. I appreciate the input, folks!

I didnt' think about the concept of paint-color as a means to reduce heat input; Good point.

I'll incorporate some of these ideas this evening, and try to get a few new pics up for your perusal... however, don't exepect me to model an entirely new engine tonight... that might take more time... :)

Thanks!

[p.s. Cargile]

The MMO looks like a good concept as well. It seems that plasma is its thrust component as well. Here are the reasons I don't like it:
--its very complicated as a means to create plasma. The more complex a system, the more expensive it to build and operate, and as it will have more parts, its potential for susbsystem failures increases, and it will need more overall preventative maintainence. That may mean more crew are required, which more mass to the mission.
--its also a very massive. The MMO .pdf file mentions that the engine, or an engine/powerplant subsystem weighs in at 200 metric tonnes. The information on the VASIMR gives the total mass of a manned Mars mission concept spacecraft of 188 metric tonnes. reference AIAA-2000-3756 (http://spaceflight.nasa.gov/shuttle/support/researching/aspl/reference/2000_3756.pdf) see page 6 . The MMO's obvious drawback is that it has to move its own bulk.

More info on the VASIMR (http://spaceflight.nasa.gov/shuttle/support/researching/aspl/index.html) which will argue its own merits.