Hopefully a future spaceship design

[SpaceFaringOrBust]

So if SpaceX is successful with the BFR/BFS, it would allow my concept of a centrifugal spaceship to be economically feasible I believe. I want to design a ship capable of transporting humans at a comfortable 1 g of rotation, which would be less than 2 rpm of rotation of the rings from the research I have done. In order to achieve both 1 g and 2 rpm the ring would need to be around 700 ft in diameter. Quite a feat of engineering to loft into space and to assemble. So here's my solution Bigelow Aerospace has already proven inflatable habitats are possible. I think that with the possibility of Made in Space's 3d printer/truss building, a centrifugal ship of that size with be possible to build with about 100 launches of the BFR. Granted it would still not be cheap, but still very possible at the estimated cost of a few billion dollars. Spread out over a few years I think this could be achievable.

What do y'all think?

[Scotius]

Honestly? I think it's too ambitious. As of now, we don't have ANY experience with rotating modules in space. Building something akin to Hermes from "The Martian." is way beyond our capabilities. Besides... it is a question "Comfort or speed?" Is it better to build one giant ship which will provide the crew with comfort and safety - but due to all the mass will require very powerful engines, will have low acceleration and will need something like a year to reach Mars on energy efficient Hohmann orbit? Or maybe we should build several smaller ships with cramped conditions on board, but able to make a trip to Mars in couple of months?

Or

[linuxgurugamer]

Have you even thought about the problems associated with a rotating ship?  Lets start off with the fact that you will be unable to maneuver, because the centrifugal force will keep the ship pointing in the same direction.  Then, have you calculated the forces which will be exerted at the outer edge?  and then, as mentioned above, how are you planning on providing thrust to the ship?

And only a few billion dollars?  Hmmm.  Let's do the math:

Falcon 9 costs about 60-80 million per launch, just for the rocket.  So there you have 6-8 billion dollars.  But, the BFR will probably cost more.  Then, the cost of the components.  Even if it was only 10 million dollars, you have another billion right there.    So already, the cost is between 7 and 9 billion dollars, and this is JUST for the ring.  What about the rest of the ship?  and boosting the fuel needed?

Do the math and come back with some real numbers before asking if it's feasible.

[kerbiloid]

Flight distances just should correspond to the contemporary engine abilities.

It's proven that a human can survive a 1.5 year long flight and stay healthy.
It's no doubt that it can be even 2 or 3 years.
Also it's clear that usability of regular 5-years long flights is doubtful.

Keep your flight duration less than a year and limit your distances with achieved ISP.
A Mars expedition needs 6-8 months of flight. Then the crew can arrive either to a planet with natural gravity, or to an orbital station with a rotating habitat.

Have a gym module in your ship with fitness equipment and a short-arm medical centrifuge (this gym can be just a 2-storey cylinder 8 meters long, 8 meters wide), eat special piles during the flight, and you need no centrifugal habitat.

When you have better engines and greater delta-V you can just keep using the same model of a spaceship with another propulsion module.
So, first you get to Mars in 8 months.
Then you get to Jupiter in same 8 months, while Mars requires just 3 months.
Later you get to Pluto in same 8 months, while Mars requires just 2 weeks.
Later you get to Pluto in 2 weeks.
And you don't need a rotating habitat.

P.S.
At the moment Bigelow hasn't proven. A small empty inflatable barrel is not a full-featured module.

P.P.S.
Leave rotation for a station.

P.P.P.S.
A rotating habitat still needs anti-radiation protection. Imagine how much should it weight.

Edited September 3, 2018 by kerbiloid

[SpaceFaringOrBust]

3 minutes ago, linuxgurugamer said:

Have you even thought about the problems associated with a rotating ship?  Lets start off with the fact that you will be unable to maneuver, because the centrifugal force will keep the ship pointing in the same direction.  Then, have you calculated the forces which will be exerted at the outer edge?  and then, as mentioned above, how are you planning on providing thrust to the ship?

And only a few billion dollars?  Hmmm.  Let's do the math:

Falcon 9 costs about 60-80 million per launch, just for the rocket.  So there you have 6-8 billion dollars.  But, the BFR will probably cost more.  Then, the cost of the components.  Even if it was only 10 million dollars, you have another billion right there.    So already, the cost is between 7 and 9 billion dollars, and this is JUST for the ring.  What about the rest of the ship?  and boosting the fuel needed?

Do the math and come back with some real numbers before asking if it's feasible.

From what I have read SpaceX is saying the BFR will be much cheaper, due to full reusability. It'll be simply the fuel cost and wear and tear. I didn't mention that it will need two rings, rotating in opposite directions to cancel out those forces. I have not calculated the outer edge forces. Thrust is not something I'm knowledgeable with at this time. For now, I was just thinking of a large ion drive. Theoretically, the ship would be on a constant loop (whatever the term is called) between Mars and Earth. Ships from Earth or Mars would launch and rendezvous during it's orbit of the planet. It would require quick rendezvous which may be a greater issue than I can fathom. Obviously, two rings of that size could hold a few thousand passengers, which would be hard to transfer even in a 2-hour orbital window. The center of the ship I plan to be modular, like the ISS and can have components add and removed quickly during rendezvous'.

Again obviously this is not something that can be built tomorrow. But I'm 33 and hope to finish my masters in aerospace engineering before I'm 40 which leaves me well over 20 years to work out the details. I believe at the current rate of space advancement, the technology will be available to build something of this magnitude.

16 minutes ago, kerbiloid said:

Flight distances just should correspond to the contemporary engine abilities.

It's proven that a human can survive a 1.5 year long flight and stay healthy.
It's no doubt that it can be even 2 or 3 years.

Keep your flight duration less than a year and limit your distances with achieved ISP.
A Mars expedition needs 6-8 months of flight. Then the crew can arrive either to a planet with natural gravity, or to an orbital station with a rotating habitat.

Have a gym module in your ship with fitness equipment and a short-arm medical centrifuge (this gym can be just a 2-storey cylinder 8 meters long, 8 meters wide), eat special piles during the flight, and you need no centrifugal habitat.

When you have better engines and greater delta-V you can just keep using the same model of a spaceship with another propulsion module.
So, first you get to Mars in 8 months.
Then you get to Jupiter in same 8 months, while Mars requires just 3 months.
Later you get to Pluto in same 8 months, while Mars requires just 2 weeks.
Later you get to Pluto in 2 weeks.
And you don't need a rotating habitat.

5

Rotating habitats will help a person transition from earth gravity to other gravity fields over the trip. Besides if we can create the gravity to provide comfort, why not?

[kerbiloid]

30 minutes ago, SpaceFaringOrBust said:

Rotating habitats will help a person transition from earth gravity to other gravity fields over the trip.

The person can have a hour-long daily training in medical centrifuge and keep shaping in gym. Piles can improve this keeping.
Then on arriving he/she can have a 1-2 weeks of adaptation period after landing.
gym+medlab are much smaller and simpler.

Edited September 3, 2018 by kerbiloid

[Cassel]

Why it needs to be ring? In tv series Expanse I've seen interesting concept. Maybe it would be better concept? Simpler than ring?

http://expanse.wikia.com/wiki/Nauvoo

[kerbiloid]

Nauvoo is more a station than a ship.

It even rotates with help of a tug swarm.

[Cassel]

31 minutes ago, kerbiloid said:

Nauvoo is more a station than a ship.

It even rotates with help of a tug swarm.

Yea it is big, but isn't simpler to build 700ft diameter cylinder than spinning ring?

[kerbiloid]

If a cylinder rotates around a static stem, it's like two rings at once, connected together with a cylindrical surface.

If the whole ship rotates, it can't maneuver, and it's big and heavy, so it makes sense for large structures, with rotation radius >! 100.200 m or so. So for a station.

Nauvoo is not designed to maneuver a lot, it would be just floating for a while, exactly like a station, and its capacity is probably thousands passengers.

In any case a large rotating structure comparable to the whole ship:
1) make the ship unstable, make it to precess and maybe overturn or crash
2) prevent any active moving like an acceleration or an orbit correction, so are useful only for stations
 

13 minutes ago, Cassel said:

but isn't simpler to build 700ft diameter cylinder than spinning ring?

Not sure if so. Diameter is rather different. What if you miss 2 m and realize this trying to connect the cylinder edges. (Don't forget, the cylinder is also expanding/shrinking not uniformly)
Personally I would build a rotating station as a bunch of parallel cylinders of much lesser diameter.

Edited September 3, 2018 by kerbiloid

[tater]

There is no need in the foreseeable future for such a huge ship. If you are assuming BFRs, including the life support capable of such a large craft, then assume the nominal crew BFRs already proposed, and use a cargo BFR to loft a nose docking ring with a spool.

 

BFS|Docking ring ----------------------SPOOL----------------------Docking ring|BFS

 

Dock and spin up the thing after 2 TMI burns (one per BFS).

[Cassel]

47 minutes ago, kerbiloid said:

If a cylinder rotates around a static stem, it's like two rings at once, connected together with a cylindrical surface.

It seems to me that two connections are not necessary. The cylindrical design gives you a huge space that is always lacking in space ships.

47 minutes ago, kerbiloid said:

If the whole ship rotates, it can't maneuver, and it's big and heavy, so it makes sense for large structures, with rotation radius >! 100.200 m or so. So for a station.

Why can not he maneuver? If you want to fly far, you need something bigger than the space shuttle.

47 minutes ago, kerbiloid said:

Nauvoo is not designed to maneuver a lot, it would be just floating for a while, exactly like a station, and its capacity is probably thousands passengers.

For what, a ship for trips lasting several months, needs maneuverability? If the journey is shorter than a few months, why do you need artificial gravity?

47 minutes ago, kerbiloid said:

In any case a large rotating structure comparable to the whole ship:
1) make the ship unstable, make it to precess and maybe overturn or crash
2) prevent any active moving like an acceleration or an orbit correction, so are useful only for stations
 

During acceleration and deceleration, the "drum" can be turned off, you can survive without artificial gravity for several hours.

 

47 minutes ago, kerbiloid said:

Not sure if so. Diameter is rather different. What if you miss 2 m and realize this trying to connect the cylinder edges. (Don't forget, the cylinder is also expanding/shrinking not uniformly)
Personally I would build a rotating station as a bunch of parallel cylinders of much lesser diameter.

Wait, what if it turns out that the space shuttle door does not close, because one wing is too long? Or what if during the construction of the bridge you make a mistake and in the middle of the river span has passed by 2 meters? We are seriously talking about what if someone makes a mistake during construction?

Maybe the cylinders are expanding, but I do not know if you've noticed that many ships that deliver different things on the ISS have a cylindrical shape, eg Automated Transfer Vehicle created by ESA, Japan also has its own H-II Transfer Vehicle in the same shape. ISS modules also have this shape. It looks like the cylinder has some advantages over other shapes.

[cubinator]

With a ship like BFR, it's probably better in the short run to just do faster transfers to Mars by spending more delta-v. The astronauts can stay almost completely healthy by exercising.

[Bill Phil]

We might be able to use 4 rpm structures. Maybe. We need to do more research.

A ship of this size isn't altogether necessary, since we can just rotate two modules around their center of mass.

5 minutes ago, cubinator said:

With a ship like BFR, it's probably better in the short run to just do faster transfers to Mars by spending more delta-v. The astronauts can stay almost completely healthy by exercising.

Well, what if we aren't transporting astronauts, but colonists? Zero-g toilets aren't that fun, and exercising is only a stop-gap measure for the problems of free fall. Pseudo-gravity, even just a small amount, would likely be appreciated. 

[tater]

Seriously, if the capability existed to make a giant ship, and you already had BFR fully operational, the spool parts could just as well be assembled in orbit, rigid, and airtight. It could be sent alongside the crew BFS vehicles with a cargo ship, then they dock, and the crew can even then transfer between vehicles. There is no need to spin to 1g, either. They can spin to martian gravity, or some lower value where toilets work, and exercise is easier to do.

[cubinator]

15 minutes ago, Bill Phil said:

 

Well, what if we aren't transporting astronauts, but colonists? Zero-g toilets aren't that fun, and exercising is only a stop-gap measure for the problems of free fall. Pseudo-gravity, even just a small amount, would likely be appreciated. 

When Mars is safe enough for people who haven't trained to use a space toilet, then some centrifugal force would be good. Tethering would be the way to go with that.

Until then, if you want to go to Mars you had better be able to figure out how to use specialized equipment and procedure.

Edited September 3, 2018 by cubinator

[kerbiloid]

36 minutes ago, Cassel said:

If the journey is shorter than a few months, why do you need artificial gravity?

That's what I'm saying.

As well as 

36 minutes ago, Cassel said:

a ship for trips lasting several months

also can avoid it.

27 minutes ago, Bill Phil said:

what if we aren't transporting astronauts, but colonists? Zero-g toilets aren't that fun, and exercising is only a stop-gap measure for the problems of free fall. Pseudo-gravity, even just a small amount, would likely be appreciated. 

And that's another reason to postpone any colonization until you get to Pluto in 8 months, to Mars in 2 weeks.
That's just 300 km/s, so total delta-V ~700 km/s, ISP*g ~1000 km/s, i.e. a good thermonuke.

When in XX century European immigrant workers were getting to America, how long did the travel typically last: 8 months or less?
Do not forget that even if the colonist crowd lives on ground for 8 months, it has a lot of problems. And what if all these problems are onboard?

36 minutes ago, Cassel said:

Why can not he maneuver?

Because you will be tilting a rotating gyroscope which resists any tilting, increasing its precession.

Of course, you can stop and rotation every time before maneuvering. For a small ship with a small crew. But imagine if something goes wrong with Nauvoo.

Edited September 3, 2018 by kerbiloid

[tater]

8 minutes ago, cubinator said:

When Mars is safe enough for people who haven't trained to use a space toilet, then some centrifugal force would be good. Tethering would be the way to go with that.

Until then, if you want to go to Mars you had better be able to figure out how to use specialized equipment and procedure.

I have to say that if it can be done simply (a tether), then I think that artificial gravity would be ideal for any crew mission to Mars.

Astronauts have time to recover on Earth after long ISS flights, but at Mars, they will need to be able to do work upon arrival. The lower gravity will help, certainly, but being pre-adapted to that would help after months in space.

[kerbiloid]

Unlike ISS they have 8 months of nothing to do except sports, and they can have a medical centrifuge.

Upd.
If connect two BFSes with noses, how great will be the floor area?
I.e. how many of colonists inside will be really living under normal gravity (1st class pax), while others will be struggling against blood circulation problems due to small rotation radius (plebs)?

Edited September 3, 2018 by kerbiloid

[tater]

21 minutes ago, kerbiloid said:

Unlike ISS they have 8 months of nothing to do except sports, and they can have a medical centrifuge.

Upd.
If connect two BFSes with noses, how great will be the floor area?
I.e. how many of colonists inside will be really living under normal gravity (1st class pax), while others will be struggling against blood circulation problems due to small rotation radius (plebs)?

This diagram (fan art) shows 4 floors, the first of which (down from the top) is many meters from where a nose docking port could be.

[cubinator]

24 minutes ago, tater said:

I have to say that if it can be done simply (a tether), then I think that artificial gravity would be ideal for any crew mission to Mars.

Astronauts have time to recover on Earth after long ISS flights, but at Mars, they will need to be able to do work upon arrival. The lower gravity will help, certainly, but being pre-adapted to that would help after months in space.

That's a good point. I've never been to space for many months, so I don't know how much trouble it would really be readapting.

[Cassel]

1 hour ago, tater said:

There is no need in the foreseeable future for such a huge ship. If you are assuming BFRs, including the life support capable of such a large craft, then assume the nominal crew BFRs already proposed, and use a cargo BFR to loft a nose docking ring with a spool.

 

BFS|Docking ring ----------------------SPOOL----------------------Docking ring|BFS

 

Dock and spin up the thing after 2 TMI burns (one per BFS).

There was video with that solution, I think it was Constellation mission.

[Vanamonde]

If you're talking about the inflatable structures I have seen proposals and models for, they are not meant for long-term habitation because they provide almost no protection against radiation and micrometeorites. 

[kerbiloid]

43 minutes ago, tater said:

This diagram (fan art) shows 4 floors, the first of which (down from the top) is many meters from where a nose docking port could be.

If I get that right, they are to be connected with noses (not with rear ends).
According to the picture that's ~1/3 of length (48 m), so rotation radius is ~15 m.
External diameter = 9 m.
Rooms are not in center, but around a ~3 m wide vertical shaft.

4 floors say 2 m high.

The upper (the nosest) floor has rotation radius ~9 m. That means 0.6 gravity of the lowest floor gravity.
So, the gravity varies from floor to floor: 1, ~0.8, ~0.7 , ~0.6, and is 20% lesser at ceiling than on floor.
As the living surface is splitted between 4 floors, they should either stay at the same floor or feel bad moving radially in varying inertial accelerations field.

The angle between rotation axis and floor normal vector varies in [10°... 24° ] range for the upper floor
So either the floor should be concave (not good when the room is 3 m wide), or tilted (not good when 14° of difference, or even 24° if count from the axis.)
Anyway when the ship lands, they should have the floors not tilted, so they should be walking tilted themselves in artificial gravity.

The central shaft is not splitted between floors (and that's strange btw because it's a loss of space.)
Its height is 6..7 m, so falling from top is like falling from 5 m on Mars, so 1.5 m on Earth.

One floor living area = pi * (9² - 3²) / 4 = 56 m².
4 floors ~200 m² (if count the cabin as a living floor, too)
Total living floor area, say, 180 m².
If have 6 m² of floor per human, that means ~=200 / 6 = 30 humans.

Total pressurized volume = 4 floors * 2 m * pi * (9m)² / 4 ~= 510 m³.
Total empty volume , say,  ~= 480 m³.
If have the needed 27..28 m³ per human that means 480 / (27..28) ~= 18 humans.

 

So, max total crew according to medical normatives ~18..20 humans.

So, 5..6 will be living in Martian artificial gravity (elite). _{Though, all rubbish from upper floors will have fallen onto their floor, so they are also janitors. And toilet overseers, too.}

8..10 in intermediate gravity (medium class: one floor for low-g medium class, one floor for high-g medium class).

5..6 (expendables) are living in nearly twice lower g but with highest coriolis and floor tilted up to 24°. It's funny, but they are pilots. (On another hands who needs pilots after landing.)

Edited September 3, 2018 by kerbiloid

[tater]

That’s with no tether or distance added.

an additional, rigid docking port could easily add 3-4m of rotational radius and fit in cargo BFR. The top floor lower g, put the place people spend most time on the bottom.