[General Battuta]

If you really want to build a spaceship from SF for realsies, I would suggest a more practical design, like, say, the one from 2001: A Space Odyssey, or Babylon 5's Omega.

I was wondering about that.  Although, I get the saucer section.

You shouldn't 'get' the saucer section, as it's one of the biggest design flaws - 10 points if you can spot why!

[Dragon]

There's also a ship from "The Mission to Mars" (that was the Polish title, anyway), fairly realistic (IIRC, I watched this movie a long time ago) and not bad looking either. Or the interstellar ship (I forgot the name) from Avatar, which was based on an actual concept. BSG may also have some realistic designs, which I would have seen if I've managed to watch more than four episodes. Star Trek is one of the worst franchises to base ships on, since it prefers aesthetics over realism.

[General Battuta]

BSG didn't have particularly realistic designs.

[The E]

The problem with that gravity wheel is that it is oriented so that its axis is perpendicular to the thrust axis. This causes some weird behaviour (Which s why all the gravity wheel designs you've seen so far have the wheel's axis in parallel to the thrust axis).

While on the subject of thrust, balancing this design so that the thrusters are "behind" the center of gravity is also going to be non-trivial.

This whole talk about triple redundancy is basically bull****. There is no practical reason for the design to be as it is (because the basic design is based on technologies noone knows how to build). This is just an extreme example of cargo cult engineering, just without the misunderstood real technology the cargo cultists want to emulate.

[jr2]

Well, you *DO* want the nuclear reactors away from people...

A reason to keep the three reactors in three separate hulls – and separated from the saucer hull – is to protect the people who reside inside the saucer hull in the case of an emergency. For example, if a meteor strikes one of the reactors, the reactor can be jettisoned away. This is a case where the Enterprise ship basic configuration that has been lifted from science fiction fits nicely with the functional needs of the actual Gen1 ship design.

Another reason to have the three reactors in three hulls set away from the saucer hull is to reduce the exposure to any low level radiation from the reactors on the people and electronic equipment in the saucer hull. While the reactors will be heavily shielded to block the release of radiation, some gamma radiation and neutron radiation will still escape at a low level.  So “distance attenuation” is a strategy used to further reduce this radiation. Distance attenuation takes advantage of the fact that radiation from the reactors falls off by the inverse-square law. While short term exposure will cause no ill effects on a person’s health, such as when workers or visitors are in the main engine hull or aux engines hulls, long term exposure might pose a health risk. Thus the reactors are located at least 250 feet away from the saucer hull at all points.

I kind of felt the same way the E did looking over the site (and I wasn't too happy about it, I want the design to be viable); however, the author does make some points for his design that aren't discernible with just a casual glance at the website.  However, I wish he'd spent some time, you know, actually covering a few bases like

1) How he plans to get all of his stuff up there (this may be possible but not right exactly now, we need some sort of heavy lifter, and it needs to be efficient or the cost is going to be nutso) and
2) how he plans to get these fuel depots in place and fueled -- ok, good, now how about re-fuelling them?? Yes, the Enterprise will use that fuel and need more.. you'd need another fleet of fueling ships (that doesn't make this impossible, it just means you need some infrastructure in place is all) and
3) How is this thing going to break orbit with .002 of constant acceleration.. is the plan just to increase speed slowly and go into increasingly wide orbits of the Earth until escape velocity is reached?

EDIT: The only thing I don't like about having the gravity wheel in front like a big shield is that it makes a nice big meteor target... maybe if you put it up on its side, and had four small reactor / engine pods spread out at equal distances from it, then it wouldn't have any problems spinning the hull around (ok, actually it might spin, I see that now but this could be countered by having ion compensation thrusters maybe... IDK - I just don't like the idea of plowing through space with a nice, big flat surface that happens to be the habitat ring in front)

Like this:

     ^  direction of travel ^

                                           ll
  engine / reactor pod >  |--ll--| < engine / reactor pod
                                           ll
                                           ^ gravity wheel

            view from top ^
        __    <engine / reactor pod
       _|__
    /         \                                       
   |           |     <gravity wheel                                   >  Direction of travel
    \         /
       -----
         |
       ----     <engine / reactor pod
view from side ^

This would make for a smaller profile to avoid meteorites / space dust (assuming high relativistic speeds were ever reached)

Right?

[General Battuta]

3) How is this thing going to break orbit with .002 of constant acceleration.. is the plan just to increase speed slowly and go into increasingly wide orbits of the Earth until escape velocity is reached?

Slow but steady acceleration is probably the best way to get around in space, and the reason ion thrusters are so promising. Steady thrust will raise apoapsis into an escape trajectory.

[The E]

The whole multiple redundancy, ejecting reactors that are hit stuff is all doable in a much more conventional, easier to build and operate design.

Also, we (well, the US Navy) has been able to safely operate nuclear reactors on ships that are much smaller than this proposed design. Why would the techniques used on carriers and subs not also work for a spaceship?

[Dragon]

The problem with that gravity wheel is that it is oriented so that its axis is perpendicular to the thrust axis. This causes some weird behaviour (Which s why all the gravity wheel designs you've seen so far have the wheel's axis in parallel to the thrust axis).

Indeed. Any attempts to accelerate this configuration would pull some people "down", some would get "lifted" off the floor, some would be pulled down the corridor and the rest would experience a combination of those effects. Not to mention I'm not sure if it won't tear itself apart when trying to turn. With an "Earth Force One" style configuration, everybody would get pulled to the side, which is comparatively easy to account for. Not to mention structural stress should be somewhat more manageable, and the center of mass would be in line with the thrust. Not to mention maneuvering thrusters placement would be easier in that layout. Same goes for plasma shield projectors (a serious technology), and eventual weapons.
As for the reactor, just put it near the engine, at the far end of the ship's "trunk". That's also make it easy to put radiators on it. You can decouple the entire assembly and fire it into space at any time, should the need arise.

[jr2]

Dragon, the problem with the last bit (firing your entire reactor/engine assembly away) is that, at this point, no one can come rescue you... you have to be self-sufficient until a fleet is operational, and, even when one is, they will take some time to get to you at 0.002g acceleration if you are out near Mars, say.  Which brings up my other point, how is 0.002g acceleration going to throw anyone anywhere when it's up against 1.0G of artificial gravity???

[General Battuta]

Dragon, the problem with the last bit (firing your entire reactor/engine assembly away) is that, at this point, no one can come rescue you... you have to be self-sufficient until a fleet is operational, and, even when one is, they will take some time to get to you at 0.002g acceleration if you are out near Mars, say.  Which brings up my other point, how is 0.002g acceleration going to throw anyone anywhere when it's up against 1.0G of artificial gravity???

I'm really trying not to tear my hair out here. I really am.

[The E]

jr2. You do not know what you are talking about. A low constant acceleration over a long period of time will take you wherever you want. The "artificial gravity" is not actual gravity, but centrifugal force (which carries _other_* problems with it).

*Other problems being the need to counterbalance the rotational forces imparted by the rotating thing.

[General Battuta]

A steady .002g acceleration will get you anywhere. If we had a rocket that could do a steady .002g once in orbit for an arbitrary burn time we'd have the keys to the inner solar system.

[jr2]

Which part?  OK, let's see, 1.0G artificial gravity = everyone is pinned to the outside of the gravity wheel.  Let's say I weigh 100 kilos.  Now, I get .002g acceleration, let's say it's pushing me towards, I don't know, the door on the other side of my room.  0.002x100=0.2kg, yes?

Unless I'm missing something here, which I probably am, but Batts is too busy sitting on his hands to explain so I'll wait until he's decided that he can explain without trying to damage his hairdo.  Really, Battuta, you should try gesturing whilst explaining, gives you something to do.  Just keep your hands away from the person who ist giving you the problem while you explain. 

EDIT:

Nonoononononononnononono


You misunderstand, I'm talking about this:

Indeed. Any attempts to accelerate this configuration would pull some people "down", some would get "lifted" off the floor, some would be pulled down the corridor and the rest would experience a combination of those effects. Not to mention I'm not sure if it won't tear itself apart when trying to turn.

0.002g acceleration.  I don't see any problems like the above occuring.

I do however see the point with the counter-rotating deal, however, I don't see how putting the saucer in front is going to fix it (the engine stack and outside of the gravity ring will just rotate counter - I suppose that's ok, but won't that detract from the spin speed of the inner ring, messing with the artificial gravity?  Wouldn't it be better to counter the force entirely, making it unnecessary to put the ring in front?

Wait a minute.  Once the inner ring is up to speed, it's actually supposed to be magnetically suspended.  So, once it's up to speed, the only force you will need to counter the counter-rotation will be whatever it takes to keep the inner wheel spinning, which I don't think will be that much if it's a) magnetically/electro-magnetically suspended and b) in a vacuum (which it will be; only the sub-compartments within will be pressurized)

EDIT2:

A steady .002g acceleration will get you anywhere. If we had a rocket that could do a steady .002g once in orbit for an arbitrary burn time we'd have the keys to the inner solar system.

I'm aware... where did you get the idea that I didn't know that? 

[Dragon]

Note, I'd prefer not to be stuck with 0.002G as the maximum delta-V. This would merely be a "cruise acceleration", used 90% of the time. It should have some kind of backup engine capable of higher Gs, for use whenever they're needed (for getting clear of space stations, or avoiding unexpected collisions). Also, a consistent force would be less annoying than a constantly changing one, and rest assured, you'll notice those 0.002G.
As for reactor ejections, being stuck with a backup chemical engine (which could be enough for a deorbit and a landing, or at least for putting the ship on a trajectory it could be intercepted on) would be preferable than being cooked by a malfunctioning reactor. Of course, given the current track record of nuke reactors, I'd say it's unlikely it ever happens.

[jr2]

http://www.buildtheenterprise.org/impulse-engines

The impulse engines are small engines seen on a portion of the outer perimeter of the aft end of the saucer hull as shown below. They are generally used only in emergency situations. When used, they apply stabilizing forces to the saucer hull, with high thrust if needed, to protect the humans inside this hull and to make sure the saucer hull does not break up or become damaged. For example, if a main engine hull or one of the aux engine hulls must suddenly be jettisoned away from the ship because a meteor strike caused a radiation leak, the impulse engines kick on to keep the Enterprise from going into a dangerous spin or roll. In fact, the main engine hull and aux engine hulls could suddenly all be jettisoned away, and the impulse engines will make sure that the saucer hull remains stable and intact.

The impulse engines also provide thrust for short periods to alter the flight path of the Enterprise in the case where there are problems with the ion propulsion engines. Even though the engines have very limited sustainable power, they can still maneuver the ship out of harm’s way if its direction is changed well before it’s near some object that it might impact. For example, if a disabled Enterprise was on a collision course with Mars, but Mars was still hours away, a slight change in direction of the Enterprise would be more than enough to prevent the Enterprise from crashing into Mars.

The impulse engines, unlike the ion propulsion engines in the three engine hulls, have a need for short term high thrust. This is required to provide the sudden bursts of thrust needed in emergency situations to stabilize the saucer hull. What technology is used to achieve this will be up to the design team to figure out. Chemical rockets, using liquid propellant systems to enable throttling, are the leading candidates, but other safer options should be investigated too.

[Dragon]

That's what I meant. Those engines should give you at least 1G, maybe more. Which invalidates this:

0.002g acceleration.  I don't see any problems like the above occuring.

In Politifact terms, full flop.

[The E]

I apologize for the misunderstanding, I misread your post.

However, you still haven't addressed the issue that conventional designs can fill many, if not all, of the same requirements and design goals put forward for this idiotic project. When designing an interplanetary starship, I should think that building it as sturdy and simple as possible would be a good goal, given that you really wouldn't want to take any unnecessary chances on this stuff.

In Politifact terms, full flop.

Oh do shut up. Show us a design that can give 1g of accel for prolonged periods of time first, please. The best constant accel engines we have, Ion engines, are limited to low thrust ratios, not to mention the need to keep engines fueled.

[jr2]

This is true.  I for one think that a single engine/reactor array would do just fine.  Actually, how about the B5 ship.. IDK what it is, but it's like a rotating cylinder... you could have one of those, rotating around the engine/reactor array, with enough distance to be safe in radiation terms (ofc you can always make a reactor safe with shielding but let's not forget that adds mass and you ofc have to get it into orbit in the first place, so the less shielding necessary, the better).

EDIT: of course you would have to counter the rotational force of the inner module.

Oh, and dragon:

http://www.buildtheenterprise.org/100-year-roadmap

[Dragon]

I was talking about those high thrust "impulse" engines. The ship is going to spend about 90% of the time under ion power (maybe even more, closer to 98%), and use high thrust engines for special situations. Still, in those situations, people on the "Enterprise" style ship would get thrown around. On the "EF1" style they also would, but in a more predictable fashion. If we had engines capable of making consistent 1G thrust, then why bother with a centrifuge?

[jr2]

Because we don't have engines capable of doing 1G thrust for more than... I don't know, a few hours at best I think (if you throttled down a liquid fueled rocket to do 1G).  They aren't fuel efficient like ion engines.

http://www.buildtheenterprise.org/engines

These three engines will all be ion propulsion type engines, sometimes also known as ion thrusters.  The thrust created by an ion propulsion engine is very small compared to conventional chemical rockets, but these engines have a very high specific impulse, meaning they use propellant very efficiency. This high propellant efficiency is achieved by accelerating the propellant to very high speeds.

*High specific impulse allows much less propellant to be carried onboard the ship, thus lowering its overall wet mass.
*Safer than chemical rockets since there are no ignited materials in the engines.
*The propellant gas used in the ion propulsion engines will be non-flammable and thus safer when stored in tanks and routed through pipes to the engines.
*Very long engine life. Ideal for the Enterprise whose engines must last for decades.
*Lends itself to being powered by a nuclear reactor that is used to generate electricity. Nuclear reactors have a very long life as a power source, which is a great fit for the Enterprise.
*A low .002g constant acceleration is so small that it does not interfere with the operation of the gravity wheel. The change in the gravity acting upon persons inside the wheel as the wheel spins is so slight that it will not be noticed.