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CaptnDave CaptnDave is offline
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Default Long-range interplanetary spacecraft
by CaptnDave 06-30-2010, 04:00 AM

I'm building a spacecraft intended for long-duration missions to outer planets with the capability to explore and study the moons of the destination planets.
I'm aiming for a fairly large ship with a crew of thirty, with an Improbable Ion Engine Drive with moderate (1-2G) impulse and high Isp. The ship would be powered by a nuclear fission or fusion reactor (likely fission for realism, unless fusion would be acceptable, given the improbable nature of the engine).
Anyways, less talk, more pictures (albeit untextured ones):
Click image for larger version

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The command module and acceleration decks are in the central tube while the living compartments are located in the lower, curved deck. Fairly spacious accommodations are given due to the length of the mission(s). In the space above the accommodations deck is the consumables storage and ?hydroponics section?. An exterior elevator brings crew and supplies between the command module and the accommodations deck.
Directly behind the command module is a docking port for a DG or XR-sized vessel. "Above" the command module is the reactor. The truss extends a ways to the IEE drive.
The ship is approx 500m long.
Let me know what you think!

Hail
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Old 06-30-2010, 06:08 AM   #2
Eccentrus
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looks nice, but I think it would be cooler if it's more bulky, that contraption surely appears fragile to me
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Old 06-30-2010, 06:46 AM   #3
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How is it able to even sustain a few gs of acceleration being that fragile looking?
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Old 06-30-2010, 03:26 PM   #4
zerofay32
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Also, you probably want the reactor as far away from the crewed sections as posible to reduce shielding (thus reducing weight).
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Old 06-30-2010, 03:56 PM   #5
CaptnDave
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Thanks for the suggestions.

Quote:
Originally Posted by Eccentrus View Post
 looks nice, but I think it would be cooler if it's more bulky, that contraption surely appears fragile to me
It's been my thought that in the middle ages of space exploration, spacecraft would be made mostly out of trusses and cables. The trusses here, although appearing small, are actually made of beams thirty cm thick. However, the coolness factor is quite important, and I agree more trusses and stuff will add to that (bye bye low poly count). Are there any other external components I should stick on (backup solar panels, more antennas)?

Quote:
Originally Posted by jinglesassy View Post
 How is it able to even sustain a few gs of acceleration being that fragile looking?
That's a good point. If I were to put in some diagonal trusses between, say, the living module and the rear and between the reactor and the rear, those trusses should take the acceleration loads instead of transferring the force at 90 degrees to the other trusses. I don't know the math required to figure out what size of supports it would need. How non-fragile looking does it have to be?

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Originally Posted by zerofay32 View Post
 Also, you probably want the reactor as far away from the crewed sections as posible to reduce shielding (thus reducing weight).
I've thought about that a bit. Unless I want to go with a "tumbling pigeon" approach the ship needs a counterbalance to the living module (which right now is the reactor). If I move the reactor to the back of the ship (away from the crew), I will have to add dead mass just to counterbalance. This way, whatever shielding is necessary around the lower half of the reactor just helps counterbalance more and less truss is needed to increase its moment.

Thanks, guys, for the suggestions! Now it's back to the modelling board to make it cooler and less fragile-looking!
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Old 06-30-2010, 05:18 PM   #6
CaptnDave
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Aand, replying to myself...
Here's the newest mesh, with more trusses and cables to handle the loads of acceleration.
Click image for larger version

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Let me know what you think!
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Old 06-30-2010, 05:47 PM   #7
francisdrake
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This design definitely looks cool! It is a kind of ultralight design, very suitable for a realistic spaceship.

Just a few thoughts: I'd rather go 0.1 to 0.2 g's, that's by far punch enough to travel the solar system within weeks (provided the engine has enough ISP and there is enough fuel on board).

If the flight direction is from left to right, I would not make the 2 diagonal stays to the ships' end. They are under compressive stress and would buckle. I would rather extend a 'jib boom' up front and have tensile stays to the outer payload and tank locations. (maybe look up 'truss' in Wikipedia )

And I would rather have the whole ship rotating along its longitudinal axis (instead of having a rotary joint at the intersection).

Looking forward to see the progress on your ship!
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Old 06-30-2010, 05:56 PM   #8
CaptnDave
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Quote:
Originally Posted by francisdrake View Post
 Just a few thoughts: I'd rather go 0.1 to 0.2 g's, that's by far punch enough to travel the solar system within weeks (provided the engine has enough ISP and there is enough fuel on board).
That is definitely true, however, Orbiter doesn't really have any good low-thrust navigation tools. Higher thrust, although being less realistic, does make navigation easier. I might build in the option to have either .1 to .2 G or ten time that.

Quote:
Originally Posted by francisdrake View Post
  If the flight direction is from left to right, I would not make the 2 diagonal stays to the ships' end. They are under compressive stress and would buckle. I would rather extend a 'jib boom' up front and have tensile stays to the outer payload and tank locations. (maybe look up 'truss' in Wikipedia )
The front of the ship is on the left in those images, so flight direction is right to left. The trusses should be under perfectly linear compression, and so not buckle, right?
Like I said, I'm no physics expert yet.

Quote:
Originally Posted by francisdrake View Post
 And I would rather have the whole ship rotating along its longitudinal axis (instead of having a rotary joint at the intersection).
That's how it is. I thought about having a rotary joint and then all the issues with those and decided to have the entire ship rotate. That's why there's an elevator that can travel up the strut to the command module.
Thanks!
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Old 06-30-2010, 05:56 PM   #9
Moach
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that thing looks really cool!

mind if i ask... which way it forward?
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Old 06-30-2010, 06:11 PM   #10
docabn
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IMO your habitat might do better if it spun horizontal rather than vertical as you have it. The reason being that with one plus acceleration, presumably for the entire trip with a small break at midway to turn the vessel around and decelerate, the crew will be standing on the walls. The need for centrifugal gravity should only be during the waiting periods between flights while in orbit.
If the habitat was horizontal then it could be locked toward the rear of the craft during acceleration / deceleration in order to keep the relative floor in the same place at all times and avoid confusion amongst the crew.

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Originally Posted by Moach View Post
  which way it forward?
perhaps I should have asked this before possibly inserting my foot. I am, or was, assuming the centrifuge was aft.

Last edited by docabn; 06-30-2010 at 06:14 PM.
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Old 07-01-2010, 07:10 AM   #11
CaptnDave
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Quote:
Originally Posted by docabn View Post
 IMO your habitat might do better if it spun horizontal rather than vertical as you have it. The reason being that with one plus acceleration, presumably for the entire trip with a small break at midway to turn the vessel around and decelerate, the crew will be standing on the walls.
Aw, I wanted to see some sleeping crewmember slide into the wall while wrapped in his bunk.
In all seriousness, my current level of piloting skill necessitates that I use Hohmann transfer-style voyages, so the majority of the trip is under no acceleration. But it is true that for if I do make a version of this for those very skillful pilots who could do that, to them, and I'll bend my mesh to suit that style of voyage. (That won't be near as hard as UV-mapping the thing)
Thanks!
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Old 07-03-2010, 01:17 PM   #12
T.Neo
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The trusses seem to be far too spindly to hold up under compression, though perhaps they could fair better at an acceleration of 0.1-0.2 G.

If you want a more realistic propulsion system, you could perhaps look into things like gas core thermal rockets or Mini-magnetic fission pulse propulsion.

Quote:
But it is true that for if I do make a version of this for those very skillful pilots who could do that
It isn't so much a lack of skill, as it is a lack of proper tools to perform such a flight.
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Old 07-03-2010, 03:15 PM   #13
CaptnDave
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Quote:
Originally Posted by T.Neo View Post
 The trusses seem to be far too spindly to hold up under compression, though perhaps they could fair better at an acceleration of 0.1-0.2 G.
The thing is, tower cranes use much the same type of truss, and that holds the under 1 G with often a fair amount of load. Should I make them thicker, or more numerous? Would having a truss stick out the front and then cables backward be better than the diagonal trusses?
Thanks as always! It's nice to have support seeing as this is my first add-on.
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Old 07-03-2010, 03:27 PM   #14
RisingFury
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I can't make any sense out of this ship. Is the bulky thing at the bottom is a hab module and serves as a counterweight to the fuel tanks at the top... and the thing between the hab module and the fuel tanks is the engine... you're gonna run into some serious problems...
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Old 07-03-2010, 03:33 PM   #15
T.Neo
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The analogy to a tower crane makes sense, but even they have more "meat";


I'd go for thicker and adding more triangulations, though configuring the ship so that most of the structure is in tension would make a big difference in terms of how strong everything would have to be.
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