Layout of a large, high end interplanetary spacecraft

[sevenperforce]

8 hours ago, fredinno said:

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

I'm afraid I'm not sure I follow. Obviously, the fuel will be liquid. Are you suggesting that the energy flux from radiation will cause the fuel to heat up and boil? Radiation doesn't really carry a lot of energy, at least not this type. Plus, denser fuels will typically have better boil-off performance than less dense fuels.

[fredinno]

5 hours ago, sevenperforce said:

I'm afraid I'm not sure I follow. Obviously, the fuel will be liquid. Are you suggesting that the energy flux from radiation will cause the fuel to heat up and boil? Radiation doesn't really carry a lot of energy, at least not this type. Plus, denser fuels will typically have better boil-off performance than less dense fuels.

The HAB between the fuel tanks will accelerate boil-off in the tanks, being so close together. Unless you plan on keeping the HAB in cryogenic temperatures?

[sevenperforce]

Just now, fredinno said:

The HAB between the fuel tanks will accelerate boil-off in the tanks, being so close together. Unless you plan on keeping the HAB in cryogenic temperatures?

The HAB will be surrounded by tanks, but it won't be touching them. No way for the heat in the HAB to enter the tanks.

And it wouldn't matter anyway if the fuel is dense enough to be liquid at room temperature.

[SomeGuy123]

2 hours ago, fredinno said:

The HAB between the fuel tanks will accelerate boil-off in the tanks, being so close together. Unless you plan on keeping the HAB in cryogenic temperatures?

My concept also has this.  TLDR, yes, the inhabited section is in between the tanks but there's a gap between.  A gap full of space (aka vacuum an amazing insulator).  

And you don't accept boiloff.  You actually are continually actively cooling the cryogenic liquid inside the tanks, from the beginning of the mission to the end.  You have dedicated piping runs and possibly even dedicated radiators for this purpose and a dedicated power system - this is the second most important system short of life support.  (since dV = ability to change your fate).  

You cool tanked hydrogen to the point that it's in equilibrium between solid and liquid.  

[Bill Phil]

My only problem is that a lot of people seem to like that ships are both a lander and interplanetary craft. That arrangement is much harder to pull off than the mother ship philosophy.

Edited February 25, 2016 by Bill Phil

[sevenperforce]

7 minutes ago, Bill Phil said:

My only problem is that a lot of people seem to like that ships are both a lander and interplanetary craft. That arrangement is much harder to pull off than the mother ship philosophy.

Well, as I explained in the other thread, once you are talking about multiple interplanetary missions you really want more flexibility. Unless you have dedicated orbital space ports at every possible destination, then the spaceship has to bring along a lander of some kind. You can only aerobrake on Earth, Mars, and Titan. Thus, for any realistic mission flexibility, it will usually make more sense to equip the mothership for powered landing and ascent instead of dragging a bunch of other spacecraft along, which would themselves need to be launched from Earth to resupply for every individual mission.

Edited February 25, 2016 by sevenperforce

[Bill Phil]

1 minute ago, sevenperforce said:

Well, as I explained in the other thread, once you are talking about multiple interplanetary missions you really want more flexibility. Unless you have dedicated orbital space ports at every possible destination, then the spaceship has to bring along a lander of some kind. You can only aerobrake on Earth, Mars, and Titan. Thus, for any realistic mission flexibility, it will usually make more sense to equip the mothership for powered landing and descent,instead of dragging a bunch of other spacecraft along, which would themselves need to be launched from Earth to resupply for every individual mission.

You can aerobrake at Mars.

The thing is, it's hard to land. Mans that gets harder the bigger your ship. You have to kill your kinetic and potential energy, and that increase the massier your ship. 

Flexibility can still be attained by a mothership design. If anything, it's more flexible. The mothership could go to a smaller body and land while the dedicates landers labd on the bigger stuff. Some low gravity moons should do fine. Like Phobos, for Mars.

But, you could also land multiple dedicated landers on different celestial bodies, all at once. That's more flexible than the mothership being the only lander, too.

[Temstar]

1 hour ago, sevenperforce said:

Unless you have dedicated orbital space ports at every possible destination, then the spaceship has to bring along a lander of some kind.

No need to be that complicated, the landers can be launched from Earth and placed in position in orbit around the destination worlds before hand. Sending the lander unmanned before hand allows you to use all sorts of slowpoke propulsion methods like solar-ion when you don't have to worry about astronaut radiation exposure as you crawl your way through space.

[SomeGuy123]

7 hours ago, Bill Phil said:

My only problem is that a lot of people seem to like that ships are both a lander and interplanetary craft. That arrangement is much harder to pull off than the mother ship philosophy.

You're right, that won't work.

What would work is the ability to use modules on the mother ship in the lander.  So you don't carry this "dead weight" lander full of fuel all throughout the solar system.  You would put the lander together from modules that were part of the mother ship mainly (more practical than it sounds - most landable bodies in the solar system are vacuum moons with modest gravity) .  If you're really a good getter, after landing you'd collect more fuel than you started with and actually leave with full tanks and with your manufacturing modules full of freshly mined refined elements.  Being able to restock at the destination makes such a gigantic difference in KSP it's not even funny, being able to do it IRL would be incredible.

Starships, I think, would be very fragile and incredibly optimized vehicles, and they'd actually manufacture everything from resources in the destination star system.  They'd carry the absolute minimum payload, basically a piece of manufacturing equipment that can self replicate given time and resources.  Upon arrival they'd build everything from rocks at the destination.

This would mean advanced aliens could be stopped.   We could do it, today.  We just have to see the starship braking (hard to miss...) and intercept it with hundreds of Orion battleships before it can manufacture stuff to kill us with using it's advanced technology.

Edited February 26, 2016 by SomeGuy123

[sevenperforce]

16 hours ago, Temstar said:

No need to be that complicated, the landers can be launched from Earth and placed in position in orbit around the destination worlds before hand. Sending the lander unmanned before hand allows you to use all sorts of slowpoke propulsion methods like solar-ion when you don't have to worry about astronaut radiation exposure as you crawl your way through space.

That works to decrease overall launch costs, but it means you have to plan missions much further in advance and greatly limits flexibility. 

18 hours ago, Bill Phil said:

You can aerobrake at Mars.

The thing is, it's hard to land. Mans that gets harder the bigger your ship. You have to kill your kinetic and potential energy, and that increase the massier your ship. 

Flexibility can still be attained by a mothership design. If anything, it's more flexible. The mothership could go to a smaller body and land while the dedicates landers labd on the bigger stuff. Some low gravity moons should do fine. Like Phobos, for Mars.

But, you could also land multiple dedicated landers on different celestial bodies, all at once. That's more flexible than the mothership being the only lander, too.

Having a landing-capable mothership in no way prevents you from bringing along one or more smaller landers. Nor does it prevent you from carrying additional fuel. The flying-saucer design in the other thread would probably be provided with a standardized on-orbit docking spire mating through the open center to which added cargo, added fuel reserves, and additional vehicles could be docked.

I'm simply arguing that if you are using centrifugal gravity for your hab, then it makes more sense to rotate your entire mothership than to try and have a separately-rotating hab. And if you're rotating your entire mothership, then it makes sense to enclose your essential components -- the hab, the primary engines, and the primary fuel supply -- inside a single robust structure. And if you already have all those essential components inside a single robust structure, then it makes sense to make that structure an integrated aeroshell so that your mothership can aerobrake for 0 dV orbital insertion (for example, at Mars or Venus or Earth). 

[John FX]

On 23/02/2016 at 6:24 PM, 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?

like this? Obviously it would spin up when not thrusting.

[Darnok]

15 hours ago, John FX said:

like this? Obviously it would spin up when not thrusting.

I was thinking about two sections. First would be spinning habitat with supplies and life support. Second section is for tanks and engines that would undock after burn is complete and move away at safe distance from habitat. Both sections would dock before entering destination orbit.
Of course habitat while docked with engine section wouldn't be able to spin.

[sevenperforce]

On 2/27/2016 at 4:00 AM, Darnok said:

I was thinking about two sections. First would be spinning habitat with supplies and life support. Second section is for tanks and engines that would undock after burn is complete and move away at safe distance from habitat. Both sections would dock before entering destination orbit.
Of course habitat while docked with engine section wouldn't be able to spin.

Why not?