Layout of a large, high end interplanetary spacecraft

[SomeGuy123]

So I've been thinking about this for a while.  I think sci fi and even NASA have it all wrong.  

Ok, see how in NASA's design they put the crew quarters near the front, inside those dumbbell centrifugal modules?

Well, those won't work.  

Instead, you build a doughnut shaped torus.  This thing is welded to a section of tunnel that leads to the low-g pressurized sections.  No rotating pressurized joints.

Instead, inside the torrus are doughnut shaped cars - or a complete ring - that rotate around and around.  Yes, there's air friction, but if it's a complete ring there isn't much, and energy is far easier to come by once you have fusion drives than mass on a spacecraft.  (energy is plentiful, mass isn't, and losing even grams of air is unacceptable)

You have 2 toruses, one after another, so you don't pay fuel to spin them.  Their hubs and bearings are all inside a sleeve welded to the side of the torus that sticks out of the tunnel section.  No spinning vacuum portion.

Then, you install the propellant tanks around your crew quarters.  All the way around.   Hydrogen slush is a good radiation shield. You plumb it and drain the tanks such that you drain them in a sequence that gives the crew maximum protection from radiation as long as possible.  That's the part NASA has wrong - all that propellant tankage they show, and none of it is protecting the crew from radiation except from the engine.

Essentially, the tanks will only go dry at the last part of the journey.  You might skimp on the permanent shadow shield from the fusion engine and have a reserve hydrogen tank there instead.  In the event that you're desperate enough, you could burn it last and singe the crew from radiation but at least get them (and the ship...) home again.  

 

 

 

 

[SargeRho]

That's a lot of moving parts. It would be a lot more reliable to spin the entire ship, either in the tumbling pidgeon style, where the ship spins end over end, and has the engines located at the center, or building something like the HOPE spacecraft and spinning it along its axis, providing both ullage for the fuel, and artificial gravity for the crew.

[Temstar]

One of the big reason why the hab is at the front is that generally, the rear of the ship will contain A BAD THING, namely a shadow shielded nuclear reactor either for power generation or NTR. Since shadow shield is really heavy the engineers will want to design it as thin as possible and rely on both the rest of the structure of the ship as well as distance to protect the crew from radiation. Hence for their own good the crew needs to stay as far away from the business end of the ship as possible.

[Scotius]

This^. Plus, for the same reason fuel tanks are placed where they usually appear - they serve as an additional shadow shield for the crew module.

[sevenperforce]

For a large, extended-persistence interplanetary transport capable of making transfers to multiple worlds, I think you need to account for the possibility of landing...if not on a large world, then at least on smaller moons. So you would want to have your engines passing through your center of mass.

I like this layout:

The habitable portion of the ship is a central rounded cylinder, surrounded by a circumferential fuel tank to provide general radiation shielding. The ship has two wings, each containing very large tank reservoirs. They serve as shields for the reactors. It has two bimodal or trimodal reactors, one on each wingtip, along with the main NTR thrusters which can be rotated. To provide artificial gravity, the thrusters are pointed in opposite directions (one up, one down) and fired, causing the entire ship to rotate.

[Nuke]

i imagine a big double hulled toroid with an engine cluster at the hub. the inner hull would contain the habitation centrifuge, while the space between the inner and outer hull will be used for propellant, water and other consumables that can be used for rad shielding. if the hub contains a reactor, then ring of metallic shielding and perhaps the radiators, coolant reservoirs, or additional consumables surrounding the core could be use to protect the centrifuge. you dont need any shielding in front of or behind the reactor, and the space between the reactor and the habitable centrifuge also helps to reduce the radiation at the habitable section.

Edited February 23, 2016 by Nuke

[PB666]

7 hours ago, SargeRho said:

That's a lot of moving parts. It would be a lot more reliable to spin the entire ship, either in the tumbling pidgeon style, where the ship spins end over end, and has the engines located at the center, or building something like the HOPE spacecraft and spinning it along its axis, providing both ullage for the fuel, and artificial gravity for the crew.

Put the tanks at the center, the engine at the center bottom. and the crew on the outside were g-forces are the greatest. This way the cost of spin up and spin down are the smallest. The problem with putting the crew on the outside however is that this is where they are most exposed to damaging radiation.

 

Just now, PB666 said:

Put the tanks at the center, the engine at the center bottom. and the crew on the outside were g-forces are the greatest. This way the cost of spin up and spin down are the smallest. The problem with putting the crew on the outside however is that this is where they are most exposed to damaging radiation.

Basically any desing that OP decides is good, do the opposite, you'de be better off.

 

 

[Nuke]

i was thinking of having a lightweight unpressurized (my double hulled toroid design gives astronauts double protection against vacuum, so further protection build into the centrifuge is unnecessary) centrifuge on some kind of magnetic bearings or maglev track system (a magnetic system has the added bonus that you get a degree of shielding from charged particles) inside a pressure hull. spinning the whole ship would introduce g loads on a lot of parts and require more beefy structural members, increasing overall mass. instead of spinning a light weight composite room with a few astronauts inside. much of the life support equipment and consumables are actually mounted inside the static hull. there might be a service car that runs in a channel next to the centrifuge (shared with a counter-torque system) that can spin up and down to transfer consumables, empty septic and gray water and trash systems (to the recycler in the static hull), and allow crew transfer between the static hull and the centrifuge (for maintenance and other operations).

Edited February 23, 2016 by Nuke

[p1t1o]

Just to play devil's bas**rd, if we are imagining a world where we can build such craft (which though using "off the shelf" technologies, still represent a leap of capability), can we imagine a world where we have drug regimes and/or genetic engineering techniques to eliminate the undesired effects of zero-G?

In this way we can make our ship WAY less complex and far less massy, for a given crew/cargo mass.

Seems to me this is a very good solution mechanical complexity and mass are all to be minimised, and safety maximised - IF, within this thought experiment, we can invoke the technologies required of course.

[magnemoe]

Tumbling pigeon design, rotate around the long axis.
http://www.projectrho.com/public_html/rocket/artificialgrav.php#pigeon
Easy to get an large diameter with this. 

Now unless you use NTR where the engine and reactor is one unit its no reason to put engine at the end, put engine at center of rotation and you can trust while rotating, this is nice for low trust engines, yes you could even land this on an smaller asteroid if you have some landing legs. 
Note that I find Tumbling pigeon pretty idiotic on an orion as its a bit short but worse the direction of trust is opposite of the artificial gravity. 
Here an spinning the ship or having an spinning centrifuge would be smarter. Crew would be in storm cellar during burn anyway. 

Now for higher trust engines especially on long burns an gimballing centrifuge makes more sense. the dream pod 9 design is an bit more complex but is gives the same gravity in the entire living area.
Note that an 0.25 g trust ship does not have to be able to move the living area 90 degree but just enough to give 1 g towards floor. 

 

[Darnok]

So spinning and "artificial gravity" is impossible in spherical objects?

How this is working?

If we could use sphere and make it spin in more than one axis we could have very practical spaceship?

[Nuke]

i think its a moment of inertia problem. the more the mass of a ship is distributed outward, the harder it is to turn. so you end up needing a lot more rcs thrust (and fuel) to maneuver. a good example is if you have ever had to carry a long 2x4. the piece of wood is easier to rotate about its long axis than the other 2 axes, and the reason is a lot of mass further out from the center. the same mass spins fine along the long axis because it is very close to the axis. 

Edited February 23, 2016 by Nuke

[Bill Phil]

38 minutes ago, Darnok said:

So spinning and "artificial gravity" is impossible in spherical objects?

How this is working?

If we could use sphere and make it spin in more than one axis we could have very practical spaceship?

It can spin on multiple axes, but it's limited to a certain plane(s) of rotation. 

[fredinno]

4 hours ago, sevenperforce said:

For a large, extended-persistence interplanetary transport capable of making transfers to multiple worlds, I think you need to account for the possibility of landing...if not on a large world, then at least on smaller moons. So you would want to have your engines passing through your center of mass.

I like this layout:

The habitable portion of the ship is a central rounded cylinder, surrounded by a circumferential fuel tank to provide general radiation shielding. The ship has two wings, each containing very large tank reservoirs. They serve as shields for the reactors. It has two bimodal or trimodal reactors, one on each wingtip, along with the main NTR thrusters which can be rotated. To provide artificial gravity, the thrusters are pointed in opposite directions (one up, one down) and fired, causing the entire ship to rotate.

That looks like a nightmare to launch, and/or build in space.

[sevenperforce]

2 hours ago, fredinno said:

That looks like a nightmare to launch, and/or build in space.

Yeah, launch would be tricky. 

Come to think of it, simply wrapping the tank all the way around a central hab and making the whole thing hella large, with the tank following a triangular contour to serve as a radshield, would probably be a better idea. Make the whole thing a flying saucer with a hole in the center. Probably the best way to get a really insanely high tankage volume while still having a decent aerodynamic cross-section.

If you could get people past their insane fear of all things nuclear, then it could launch under its own power, though it would need to be refueled as soon as it reached orbit.

[radonek]

15 hours ago, SomeGuy123 said:

Instead, inside the torrus are doughnut shaped cars - or a complete ring - that rotate around and around.  Yes, there's air friction, but if it's a complete ring there isn't much, and energy is far easier to come by once you have fusion drives than mass on a spacecraft.  (energy is plentiful, mass isn't, and losing even grams of air is unacceptable)

Wont work that way. If you pump in energy to counterbalance additional friction, you will slowly gain torque and have to expend propelant to counter. Yes, you can have two counter-rotating habs, but that is a lot of additional weight, machinery, moving parts and complications.
 

[SomeGuy123]

2 hours ago, radonek said:

Wont work that way. If you pump in energy to counterbalance additional friction, you will slowly gain torque and have to expend propelant to counter. Yes, you can have two counter-rotating habs, but that is a lot of additional weight, machinery, moving parts and complications.
 

Not with 2 counter rotating habs, which is the only way to do this anyway.  Any torque transfer from friction from ring A to the non rotating section gets canceled by equal and opposite torque transfer from friction from ring B.  You can purposefully make your electromagnetic bearings let friction through to guarantee this.  Obviously each electromagnetic bearing has a digital controller, and dedicated data wiring linking it to the other bearing and to onboard accelerometers and starfield sensors so it can react to even tiny angular changes instantly to keep the whole system stable.

I don't see 2 identical rings as being insurmountably more complex, going from a world with no rings and no fusion drive spacecraft to a world that can afford one is a huge step, going to 2 rings is a tiny step.

Edited February 24, 2016 by SomeGuy123

[SinBad]

valkyrie rocket. Works like an orion nuclear pulse drive, but the explosion happens at the front of the starship (in the pic below, explosion behind the coil, but in front of the shadow shield) and acts against a magnetic sail. Everything else is towed behind on cables behind a small shadow shield. Much less mass required than pusher plate designs. It is an antimatter rocket though...

[SomeGuy123]

1 hour ago, SinBad said:

valkyrie rocket. Works like an orion nuclear pulse drive, but the explosion happens at the front of the starship (in the pic below, explosion behind the coil, but in front of the shadow shield) and acts against a magnetic sail. Everything else is towed behind on cables behind a small shadow shield. Much less mass required than pusher plate designs. It is an antimatter rocket though...

Might want to fix your image link.  I've read about this - probably don't need this kind of performance for mere interplanetary missions.  Furthermore, the problem with antimatter is that thrust and ISP are inversely related because every time you double ISP you quadruple the energy released, and so high performance antimatter designs must therefore have awful acceleration.  (because more energy release means more waste heat release which means weighing your rocket down with radiators which means you cannot accelerate as quickly)

For this reason, antimatter designs could easily be slower than fusion rockets over interplanetary distances.  It doesn't matter if the ISP is far higher if you need years to even get up to speed.

I think aneutronic fusion rockets might give much better acceleration because almost all the output products are charged particles which means you can prevent them from even touching your rocket and thus eliminate having to reject the waste heat at all.

Edited February 24, 2016 by SomeGuy123

[problemecium]

What I'm thinking after reading this, and has occurred to me now and then when reading about interplanetary/interstellar ships, is this:
- The preferred option for crew quarters is a rotating torus.
- The preferred option for a purported warp drive is also a torus.
- Docking with a rotating craft is much easier near the middle, so there should be one or more ports at the center.
- The artificial gravity gets stronger farther from the center, so it's reasonable to try and put heavy stuff like engines and reactors near the middle so as to minimize structural load.
So if we have a port at the center, surrounded by machinery and engines, in turn surrounded by a torus, in turn surrounded by another torus... it makes a saucer shape.
Hmmmmmmm......

[fredinno]

21 hours ago, sevenperforce said:

Yeah, launch would be tricky. 

Come to think of it, simply wrapping the tank all the way around a central hab and making the whole thing hella large, with the tank following a triangular contour to serve as a radshield, would probably be a better idea. Make the whole thing a flying saucer with a hole in the center. Probably the best way to get a really insanely high tankage volume while still having a decent aerodynamic cross-section.

If you could get people past their insane fear of all things nuclear, then it could launch under its own power, though it would need to be refueled as soon as it reached orbit.

Yeah, the heat from the HAB would accelerate boil-off. Also, if this has enough thrust to launch on its own power from Earth, that's a sign you have TOO MUCH thrust.

14 hours ago, parameciumkid said:

What I'm thinking after reading this, and has occurred to me now and then when reading about interplanetary/interstellar ships, is this:
- The preferred option for crew quarters is a rotating torus.
- The preferred option for a purported warp drive is also a torus.
- Docking with a rotating craft is much easier near the middle, so there should be one or more ports at the center.
- The artificial gravity gets stronger farther from the center, so it's reasonable to try and put heavy stuff like engines and reactors near the middle so as to minimize structural load.
So if we have a port at the center, surrounded by machinery and engines, in turn surrounded by a torus, in turn surrounded by another torus... it makes a saucer shape.
Hmmmmmmm......

 Not really- the only reason that was the design set out is since the OP thinks current future interplanetary designs are flawed- you know, the ones with the propulsion at the back and the HAB at the front- artificial gravity can be done by spinning the ship using the prop. module as a counterweight, or a nautilus-X esque centrifuge. A really big one would likely look more like an O'Neil Colony with a propulsion system. After all, space stations are just spacehips without propulsion.

[sevenperforce]

4 minutes ago, fredinno said:

Yeah, the heat from the HAB would accelerate boil-off. Also, if this has enough thrust to launch on its own power from Earth, that's a sign you have TOO MUCH thrust.

Well, the heat from the hab can be eliminated by depressurizing the tankage; no heat sink without a heat transfer medium. And you'd probably want to use something with better boil-off properties, like hydrazine or ammonia or liquid methane (if you can get the latter two to disassociate).

Trimodal engines inject LOX just after the chokepoint to augment thrust at the expense of specific impulse; you'd use these for takeoff and then refuel with something lower-density for orbital transfer.

[fredinno]

26 minutes ago, sevenperforce said:

Well, the heat from the hab can be eliminated by depressurizing the tankage; no heat sink without a heat transfer medium. And you'd probably want to use something with better boil-off properties, like hydrazine or ammonia or liquid methane (if you can get the latter two to disassociate).

Trimodal engines inject LOX just after the chokepoint to augment thrust at the expense of specific impulse; you'd use these for takeoff and then refuel with something lower-density for orbital transfer.

I had the impression the sheilding was also carrying fuel?

[sevenperforce]

1 minute ago, fredinno said:

I had the impression the sheilding was also carrying fuel?

Errr...yes.

The fuel tanks serve as the shielding; when the fuel tanks are depleted, shielding isn't as great, which is why you definitely want to refuel quickly. But it wouldn't be too bad; you could always enter a portion of the ship with additional shielding temporarily.

See below -- I linked a mockup.

15 hours ago, parameciumkid said:

What I'm thinking after reading this, and has occurred to me now and then when reading about interplanetary/interstellar ships, is this:
- The preferred option for crew quarters is a rotating torus.
- The preferred option for a purported warp drive is also a torus.
- Docking with a rotating craft is much easier near the middle, so there should be one or more ports at the center.
- The artificial gravity gets stronger farther from the center, so it's reasonable to try and put heavy stuff like engines and reactors near the middle so as to minimize structural load.
So if we have a port at the center, surrounded by machinery and engines, in turn surrounded by a torus, in turn surrounded by another torus... it makes a saucer shape.
Hmmmmmmm......

Well, speak of the devil....

[fredinno]

7 hours ago, sevenperforce said:

Errr...yes.

The fuel tanks serve as the shielding; when the fuel tanks are depleted, shielding isn't as great, which is why you definitely want to refuel quickly. But it wouldn't be too bad; you could always enter a portion of the ship with additional shielding temporarily.

See below -- I linked a mockup.

Well, speak of the devil....

Yeah, then the fuel will need to be as dense as possible- ie liquid form, so boil-off IS a problem.