Hopefully a future spaceship design

[tater]

1 hour ago, kerbiloid said:

If I get that right, they are to be connected with noses (not with rear ends).

The nominal docking for refilling operations is indeed tail to tail. The image above shows radar/comms in the nose, I would propose adding a nose to nose docking port for crew (or a tether) to facilitate a spun pair of craft.

[sh1pman]

1 hour ago, tater said:

The nominal docking for refilling operations is indeed tail to tail. The image above shows radar/comms in the nose, I would propose adding a nose to nose docking port for crew (or a tether) to facilitate a spun pair of craft.

Someone needs to tweet this to Elon!

[satnet]

9 hours ago, SpaceFaringOrBust said:

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.

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?

It sounds like you're talking about an Mars cycler (you may also see it called an Aldrin cycler due to "Buzz" Aldrin's contributions) with a rotating section. This is more akin to a station than ship, though that distinction can be fuzzy in space. You can justify more mass because you get to use it over and over again, but this justification has its limits.

Like a lot of space infrastructure you're problem is not so much technical feasibility, but the economics and politics. For this one you have to justify 100 BFR launches which could have been put to other use. If the BFR can get to mars with 1 crew/cargo launch + 5 refuel launches that is the equivalent of trading ~16 BFR direct missions for this one cycler. If we do have a colony that might make sense because we'll be sending cargo and people for the foreseeable future, but for the early missions it is going to be overkill.

If it were me I would downscale this quite a bit. First, if this really only makes sense if we have permanent habitation we must have established that martian g is sufficient for long term, so target 1/3rd of a g instead of a full earth g. You can always design it with connectors so you can expand it out to a full g. I would also make them arc segments instead of full rings (again you can plan for expansion to a full ring).  Put only the things that benefit from gravity in there: gym, dining areas, medical, and sleeping quarters (some of those are debatable, but you get the idea). Those are just my first thoughts.

p.s. Rendezvous is slightly more delta-v than the direct mission. The benefit of a cycler isn't reduced delta-v, but the ability to re-use the high mass cycler while only boosting the much smaller rendezvous craft up to that speed.

[kerbiloid]

8 hours ago, tater said:

The nominal docking for refilling operations is indeed tail to tail.

Spoiler

This makes things better.

They can pour water into the nose room and have a pool to jump there from 3 other storeys.

 

P.S.
Just had a look. In XX century it typically took about 5..6 days for a steam ship to cross the Atlantic ocean.
So, that's probably what is required to transfer colonists, if they are not specially trained spacemen, but a next-door working class.

I.e. 1-2 weeks to Mars, which also means 8 months to Pluto.
Intermediate recreation stops breaking long routes into parts.

As unlikely somebody will be colonizing something beyond Saturn, this looks like:
1..2 weeks to Mars - stop - 1..2 weeks to asteroids ( - stop - 1 .2 months to Jupiter or Saturn, which anyway are less populated)

Edited September 4, 2018 by kerbiloid

[tater]

2 hours ago, kerbiloid said:

Just had a look. In XX century it typically took about 5..6 days for a steam ship to cross the Atlantic ocean.
So, that's probably what is required to transfer colonists, if they are not specially trained spacemen, but a next-door working class.

In the  age of sail it too 40-100 days. The Mayflower took 64 days, for example.

[KerikBalm]

the relevant equations here are:

a=v^2/r   and v= 2pi*r/t    (v=d/t, where distance is the circumference of the circle, 2*pi*r)

Combine these to get a= 4*pi^2*r/t^2. Therefore to maintain the same acceleration, if you halve the radius, you have to decrease t by a factor of sqrt(2).

If you go from 2 rpm to 4 rpm, the diameter of the ring can be decreased by a factor of 4. Why shouldn't we use something like 10 RPM?

We want a to equal... lets say 9 m/s^2, just over 0.9 Gs, comfortable 8and about what you'd experience on Venus). 2 rpm is a revolution time of 30 seconds...

9= 4*pi^2*r/30^2:    9= 0.0439*r: r = 205 meters (why do calculations in feet.... but yes, this is about 700 feet). At 6 rpm (one spin every 10 seconds, not 30), this is just 22.8 meters (75 feet... nearly an order of magnitude improvement). Now a problem is that if you shrink the radius too much, there will be a noticeable acceleration gradient between one's head and feet when standing up. A 2.3 meter tall human would only experience a 10% difference between their head and feet at this radius.

In KSP, I made a stock centrifuge that can rotate in less than 6 seconds... (>10 rpm), this means the required radius is just 8.21 meters (so it only needs to be 16.42 meters in diameter (54 feet).

What is so important about keeping the RPM low that we can't do 10 RPM instead of 2 RPM? The savings on the siye of the centrifuge are enormous.

54 feet in diameter vs ~1,400... 2 RPM is ridiculous.

For comparison, these are the stated dimensions of the ISS:

Length: 72.8 m (239 ft), Width: 108.5 m (356 ft), Height: 20 m (66 ft)

A centrifuge giving nearly Earth strength "artificial gravity" is quite feasible, just accept 10 rpm instead of 2.

 

[kerbiloid]

1 hour ago, tater said:

In the  age of sail it too 40-100 days. The Mayflower took 64 days, for example.

100 days is anyway a hyperbolic trajectory, hardly available with chemicals.
And unlikely one would like to have a random crowd onboard for months.

But yes, when Mars = 1.5..3 months, then 8 months = Jupiter, that's an intermediate phase.

15 minutes ago, KerikBalm said:

just accept 10 rpm instead of 2

We can. Does the stomach?

Edited September 4, 2018 by kerbiloid

[KerikBalm]

Why wouldn't it? If it helps, one can remove the windows in the part with gravity, or climb to the center and go to the zero grav part (which is nauseating at first for most astronauts anyway, and takes some getting used to).

It shouldn't be perceptible most of the time, except when standing up or lying down, because of the acceleration gradient. At 6 rpm, that's only 10% though for a very very tall human. At 10 rpm, its a 1 meter change in height that produces a 10% gradient... so have the bunks 1 meter from the floor (store personal stuff under the bunk), and your torso and CoM wont' experience much change at all, while your head and feet only experience ~10% changes.

I'm sure it would be manageable.

You could have 2 counter-rotating sections that spin up and spin down each day (or every few days), so astronauts can recover from the effects of weightlessness, but not always be dealing with acceleration gradients.

Its a shame they never attached a centrifuge module to the ISS, I think one was planned at one point

[kerbiloid]

3 minutes ago, KerikBalm said:

one was planned at one point

One was planned but later cancelled.

[SpaceFaringOrBust]

18 hours ago, Vanamonde said:

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. 

From what I've read they provide more protection. Especially micrometeorites. Think of a kevlar vest compared to a sheet of aluminum the same thickness.

19 hours ago, Bill Phil said:

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

 

I will have to find the article, but 2 rpm is the ideal speed to not cause motion sickness

 

[SpaceFaringOrBust]

5 hours ago, KerikBalm said:

 

What is so important about keeping the RPM low that we can't do 10 RPM instead of 2 RPM? The savings on the siye of the centrifuge are enormous.

 

 

1

https://www.artificial-gravity.com/sw/SpinCalc/

Not many humans couldn't stand a 10 rpm structure. I doubt any could stand it for 6-8 months. Around 2 rpm is ideal for motion sickness

[KerikBalm]

Well, this article suggests that one can adapt to 30 rpm, so my more modest proposal of 10 rpm should be fine:

https://www.researchgate.net/publication/222402733_Modeling_sensory_conflict_and_motion_sickness_in_artificial_gravity

This older one too:

https://www.ncbi.nlm.nih.gov/pubmed/18496680

Then there's this

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4470275/

Quote

The results of studies on humans living aboard slow rotating rooms in the 1960’s (Graybiel et al., 1960, 1965, 1969; Kennedy and Graybiel, 1962; Guedry et al., 1964) suggested that the lightest acceptable system for providing “comfortable” artificial gravity using a rotating spacecraft would be one rotating at 6 rpm at a radius ranging from 12–24 m, such as to create an artificial gravity level ranging from 0.3 G to 1 G (Stone and Letko, 1965; Figure Figure2).2). These theoretical limits to rotation rates and radii were based on casual observations of humans walking, climbing, moving objects, and performing nominal head movements in a large-radius centrifuge. These assumptions have largely been taken at face value as correct, but they need to be validated by experimental evidence. More recent data suggest that the adaptation limits of humans to rotating environment are much greater than these earlier studies had anticipated. For example, it has been observed that subjects in a rotating environment could tolerate a rotation rate up to 10 rpm provided that the exposure is progressive (Graybiel et al., 1965) or even up to 23 rpm after habituation of motion sickness symptoms (Young et al., 2001).

Your spin calc thing mentions only: "The value is too high for comfort or will require deliberate adaptation." or "The value is too low for comfort or will require deliberate adaptation."

Considering the massive benefits to the size of the spacecraft, I don't think its too much to ask for some "deliberate adaptation", particularly considering that adaptation is already required just for zero G itself.

This one used 28 rpm, not very long, but no mention of participants vomitting:

http://news.mit.edu/2015/exercise-artificial-gravity-space-0702

Limiting it to 2 rpm seems ridiculous...

[kerbiloid]

I have a feeling that such person who can withstand 23 rpm, can also survive for several months without rpm.

Edited September 4, 2018 by kerbiloid

[KerikBalm]

Yes, people have spent over 400 days in space... your point?

[kerbiloid]

17 minutes ago, KerikBalm said:

people have spent over 400 days in space.

So, they can spend 240.

And if unlike ISS they have a medical centrifuge, a full-featured gym, and a lot of free time during the flight, then they probably can stay less untrained, so there will be no need in a complicated rotating module.

Of course, also the helpful piles should be kept being developed  to improve the crew fitness from inside.

P.S.
Crowds of random untrained colonists shoud be postponed till 1-2 week long flights to the corresponding planet.

Edited September 4, 2018 by kerbiloid

[Cassel]

I found this, different use of cylinders, hope it adds something ;-)
 

 

[linuxgurugamer]

4 minutes ago, Cassel said:

I found this, different use of cylinders, hope it adds something ;-)
 

 

Very interesting, I've seen those ideas elsewhere.  But it doesn't seem to have anything for the voyage back.  Also no sense of scale here

[kerbiloid]

Somebody should leave this here.
http://www.projectrho.com/public_html/rocket/artificialgrav.php

[Cassel]

21 minutes ago, linuxgurugamer said:

Very interesting, I've seen those ideas elsewhere.  But it doesn't seem to have anything for the voyage back.  Also no sense of scale here

This is more realistic concept

 

[tater]

43 minutes ago, linuxgurugamer said:

Very interesting, I've seen those ideas elsewhere.  But it doesn't seem to have anything for the voyage back.  Also no sense of scale here

The TEI stage was shown just behind the rotational hub. Both spun hab components have a capsule, so I would assume that's basically Apollo sized (that's enough for 6 crew, and vid says 5 crew). The lander was a MDAV, so it's for landing, and return. I'd guess the habs then at ~4m dia.

[KerikBalm]

15 hours ago, kerbiloid said:

So, they can spend 240.

People have survived over 400 days in space, but they come back with severe problems, loss in bone density, muscle atrophy, sight problems, etc.

Taking a few days to get used to the rotation and not be dizzy is nowhere near comparable. Luckily if Mars is the destination, the problems will be less severe upon landing because its only 0.376 Gs, but unluckily there won't be support crews to carry them around. Its not known how much 0.376 Gs will help, so if they spend a lot of time there and then go back into space, they could have very severe problems when they get back to Earth after an additional several months in weightlessness.

However, if there is a centrifuge, one could start it at 0.376 Gs, and speed it up to 0.9 Gs on the way back, this will handle the acclimation to higher RPMs, and the adaptation to Earth's gravity.

It seems really obvious to me that the answer is a shorter radius/higher RPM centrifuge. It doesn't have to start at 1 G, it can take a month to get there.  Actually for the outbound journey maybe you'd only spin it up to about 0.6 G (between Earth and Mars gravity), so that the astronauts are plenty strong for Mars upon arrival, but acclimating to the rotation is easier.

On the way back, you've got 240 days to acclimate to the rotation, and given that they just spent a lot of time at 0.376 G, you wouldn't want to start much higher than that anyway (meaning lower initial RPM)... so lets say 15 days going from 0-0.4 G, then the next 100 days going from 0.4-0.9, then the remainder of time they spend at 0.9 Gs, and arrive back on earth pretty well adapted, since they've been at 0.9 Gs for the last 115 days.

[kerbiloid]

21 minutes ago, KerikBalm said:

People have survived over 400 days in space, but they come back with severe problems, loss in bone density, muscle atrophy, sight problems, etc.

These people don't have any training centrifuge, they are in zero-G 24/7.

Their time is occupied by scientific chores.

While an interplanetary ship crew spend their days in laziness and idleness,
(Just due to the lack of scientific equipment. Nobody should study materials or perform physical experiments on its board, tools are too heavy.)
That's btw another reason to keep colonist routes as short as possible.

So, the main joy and occupation of an interplanetary crew is workout, and the ship is a natural shaping club.
A huge gym with a short-hand medical centrifuge is a must have for any route more than month long.

And it's technically by orders of magnitude easier to implement than a rotating habitat.

Edited September 5, 2018 by kerbiloid

[KerikBalm]

Ok, thats fine, I wasn't arguing about having the whole thing rotate vs only a small section, I was just arguing that a shorter higher RPM centrifuge is better than the originally proposed 2 rpm, 210 meter centrifuge...

[Tyko]

On 9/3/2018 at 10:58 AM, Vanamonde said:

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. 

Interesting point...what if your inflatable included an internal core full of air with an outer shell "inflated" with water? It would stop most radiation and if it were thick enough and baffled with many small cells it could stop or absorb most of the energy from micrometeorites while only losing the cell that was hit.

[kerbiloid]

A layer of slime in strong electrostatic field.
A micrometeorite hits, the slime gulps, the droplets get attracted back by electrostatics.

The micrometeorite sinks in the slime and gets digested.
Here we come to bioships.

Edited September 6, 2018 by kerbiloid