Large scale colonization ship

RobertDyck · 2020-07-15 22:15:01

Second question: ticket price. I'm running some financial numbers. Trying to see how a working person could afford a ticket to Mars. Conclusion is ticket price has to be US$100,000 per person. That's a lot of money, but profit to the corporation is not that much.

I said 162 economy cabins, each with 6 beds. Assume 6 cabins used by crew. Further assume cost to book an entire economy cabin is the cost of 5 beds; so you get a little discount by booking the whole cabin. If you buy just one ticket for yourself, you're assigned a bunk in a cabin with strangers. Assume an average of 5 bunks filled per cabin. That's actually pretty full.
I also said 90 "single" cabins, same size as economy but with only a one bed: queen size Murphy bed. More space, but cost of the cabin is the same as a whole economy cabin. Assume 1 cabin is assigned to the captain, the other 89 are for passengers. Further assume 2 passengers per cabin. (Doesn't matter since it's fixed price per cabin.)
Plus 4 "premium" cabins, each 4 times the size of an economy cabin. Each premium cabin would have a queen size bed, and a hide-a-bed couch that can fold out as another queen size bed. Assume average of 2 passengers per cabin.
Plus only 1 "luxury" cabin, each 4 times the size of premium, which is 16 times the size of economy. That's for someone rich with more money than brains. It would also have a hide-a-bed couch, but assume only 2 people in that cabin.

This adds up to 780 economy passengers, 178 passengers in "single" cabins, 8 premium passengers, and 2 luxury passengers. Total 958.
Crew would include only 24 to care for economy and "single" passengers, 6 to care for premium and luxury passengers. This leaves only 6 more crew members to join the captain on the bridge. So total of 7 to operate and repair the ship. That seems a too spartan.

This is based on flight attendants on a commercial airliner. US regulations require at least 1 flight attendant for 50 passengers. One airline has 1 flight attendant for 40 passengers. So using the 1:40 ratio, that gives us 24 crew. But this isn't an aircraft with flying time measured in hours. This is a ship that will take 6 months one way. Crew includes a chef to cook meals. You can't have prepared meals that are just heated in a microwave, they won't keep that long. Dry food like flour will keep years, but that requires cooking. So this ship will literally require a ship's kitchen. And dining rooms with waiters/waitresses. Housekeeping maids, laundry service. Medical staff including ship's doctor, dentist, nurses. Cruise ships typically serve meals in 2 shifts per meal, but I said 3 shifts so we could make dining rooms smaller. Those same dining rooms would be used for entertainment: movies (digital recording on ship's server, played on data projector), and live entertainment. What I suggested for live entertainment would be someone who could give lectures on Mars, what to expect when they arrive. As well as astronomy lecture; Discovery Channel has some beautiful programs, a live presentation would be great. And lectures on how the ship works. Passengers would be literally on a spacecraft in space, they would want to know more about it.

There would be a gym, but I said 1/2 the square feet per passenger of a cruise ship. That still results in 4,000 square feet of gym for the ship. There has to be someone to give advice/training and run the gym. And the hub would be used to receive passengers, but during the transit could be use for zero-G entertainment. Would want a crew member there to ensure passengers don't hurt themselves.

So this number sounds low. But if an economy ticket costs US$100,000 per person, then a whole economy cabin would cost US$500,000. So a family of two parents and 3 or 4 children would have to pay US$500,000. A "single" cabin would also cost US$500,000. A premium cabin would cost US$2 million, and the luxury suite would cost US$8 million. You could charge more for premium or luxury, but there aren't many of those cabins, so lets use these prices for now.

Based on occupancy above, this works out to $138.5 million per trip to Mars. That doesn't sound like a lot considering the investment. Even though the ship is reusable, the ship will only make 1 round trip ever 26 months. That's when the planets align.

Interviews with Elon Musk stated he thought ticket price could drop below $500,000 per ticket. Eventually he thought it could drop down to $100,000. That ticket price would have expenses. It would include advertising, and a long passenger orientation. During orientation, passengers would have to be quarantined for at least 2 weeks. Don't want to bring COVID-19 or any other disease to Mars. And the ticket would include shuttle service to carry passengers to LEO. Assume shuttle is the SpaceX Starship. Announcements by SpaceX claim Starship will operate Earth-to-Earth, with a trip from New York to London in 29 minutes. Such a ticket would cost the same as an economy class airline ticket. Really? That cheap? That wouldn't take much from the Mars ticket price.

But still, for this to work it must be profitable. Could we fill this ship if ticket prices were 3 times what I just listed? That would be US$300,000 for a single bunk in an economy cabin, or US$1.5 million for a whole cabin.

Void · 2020-07-16 08:33:23

Robert,

Per your first question a post or two back, this is from Dr. Robert Zubrin. I have not yet found a reference to radiation shielding. I just have not looked it over well yet.
https://www.centauri-dreams.org/2018/06 … ropulsion/
His drive will work backwards and forwards in the solar wind, and will also work in the Earth's magnetic field

However this one claims radiation protection:
https://www.centauri-dreams.org/2017/12 … 20diameter.

I am having a lot of trouble understanding the size of the actual parts. However, it is supposed to be very light. This one will not go backwards against the solar wind, and cannot operate in the Earth's magnetic field.

I don't know what the compatibility would be with your "Large scale colonization ship.

But if nothing else the 2nd one (Spinning magnetics), can carry the luggage. I visualize that in this one the solar panels would be
Collapsible, and would make a one way trip to Mars. They would be brought to LEO by Starship, and unfurled , and then at Mars would be collapsed, and brought down to the surface by Starship. Along the way they would pay their passage by powering the magnetic plasma drive.

Perhaps one of you could do a better analysis of these drives to help. I am especially interested in the 2nd one because I cannot figure out its scale relative to say a Starship.

This quote from it seems to indicate that the solid parts are small, which makes me wonder what the large rings in the depiction are about?
Are they a magnetic effect?

Developed by John Slough and others [5, 6], the plasma magnet drive has been validated by experimental results in a vacuum chamber and was a NIAC phase 1 project in the mid-2000s [6]. The drive works by initially creating a rotating magnetic field that in turns traps and entrains the charged solar wind to create a large diameter ring current, inducing a large scale magnetosphere. The drive coils of the reference design are small, about 10 centimeters in diameter. With 10 kW of electric power, the magnetosphere expands to about 30 kilometers in diameter at 1 AU, with enough magnetic force to deflect the solar wind pressure of about 1 nPa (1 nN/m2) which produces a thrust in the direction of the wind of about 1 newton (1N). Thrust is transmitted to the device by the magnetic fields, just as with the coupling of rotation in an electric motor (figure 2).

Size matters, per how the Starship operates either with a Hohmann transfer or Ballistic Capture. Ballistic Capture would be better, if this is a large device, otherwise, I guess just turn it off when you get to Mars.

But yes, for this one radiation shielding.

I might note that if this device is small as they seem to indicate, you may bring it back to Earth and use again. On the way back I would anticipate only the crew, and perhaps a small number of passengers, so just a storm shelter might be sufficient for that many.

Here is the radiation protection claim:
3. Charged particle radiation shield for crewed flights

The magnetosphere generated by the engine makes a good radiation shield for the charged particles of the solar wind. It should prove to be a good solution for the solar wind, solar flares and even coronal mass ejections (CME). This device could, therefore, be used for human flight to reduce radiation effects. For human crewed flights, the 1N of thrust is insufficient for the size of the spacecraft and would have a marginal propulsion compared to the main engines. Given the plasma magnet’s small size and mass, and relatively low power requirements, the device provides a cost-effective means to protect the crew without resorting to large masses of physical shielding. The plasma magnet would appear to be only effective for the charged solar wind, leaving the neutral GCRs to enter the craft. However, when an auxiliary device is used in the mode of aerobraking, the charge exchange mechanism should reduce the galactic cosmic ray (GCR) penetration (see item 8 below).

Even though it is not by itself suitable for Crewed mission propulsion, I would really think that like early steamboats with sails, it might earn its keep by reducing the amount of propellant needed for the Raptor engines.

Done.

Last edited by Void (2020-07-16 08:45:23)

RobertDyck · 2020-07-16 12:35:23

Recalculating floor area. There is enough room for separate crew quarters. So all 162 economy cabins, and all 90 "single" cabins could be for paying passengers. Economy cabins have a capacity of 6 passengers, but let's say average of 5 per cabin, and 100% of all cabins occupied. Single cabins have a queen size bed, capacity 2 passengers. Say 100% occupancy. Premiums cabins have a queen bed and a hide-a-bed couch, so could carry 4 passengers, but lets say 2 passengers per cabin. And the one luxury cabin has a hide-a-bed couch as well, but again lets say 2 passengers. Besides, "single", premium, and luxury cabins have a fixed price per cabin. And we're saying all cabins occupied.

Lower ticket price:
US$100,000 for a bunk in an economy cabin. You're assigned a room with strangers.
US$500,000 for a whole economy cabin.
US$500,000 for "single" cabin.
US$2 million for premium cabin.
US$8 million for luxury cabin.
Total revenue with all cabins occupied: US$142 million per trip.

Now what if first several trips the ticket prices was triple that. Could we fill the ship?

GW Johnson · 2020-07-16 12:39:46

I guess I don't understand why no one has picked up on Bigelow's way of providing radiation shielding.

Everybody talks about 15-20 cm thickness of water. That's density x thickness = 1 g/cc x 15 to 20 cm = 15 to 20 g/sq.cm worth of shielding mass per unit area, which is the real design criteria (read the old NASA report yourself, if you don't believe me). Change the material density, and you must change the thickness required to achieve 15 to 20 g/sq.cm.

Water is modest molecular weight (but fairly high density with a low thickness), so the secondary shower tendency is low. So also hydrogen, and most of the other low molecular weight materials, are composed of low weight atoms (they just need thicker layers because of the lower densities). Meaning you want as shielding things composed of atoms like carbon, hydrogen, oxygen, and maybe nitrogen atoms. The metals other than aluminum, maybe not so much, but the polymers derived from petroleum qualify.

Think about it. Multiple layers of fairly coarse-woven polymer fabric (Kevlar and some others). Carbon, hydrogen, and oxygen atoms, mostly, so the secondary shower risk is low. The polymers themselves have a density more-or-less comparable to water, one way or another. But there's a lot of void space in all woven fabrics.

Let us assume half polymer and half void on a volume basis. Nothing but a wild guess on my part! So the effective density is near 0.5 g/cc. Bigelow puts a meter thickness = 100 cm of these fabric layers on its B-330 module as thermal insulation and a meteor bumper. This is outside the inflatable pressure vessel, which is on the inside.

0.5 g/cc x 100 cm = 50 g/sq.cm mass per unit area. That's a very good radiation shield, and still is a pretty good shield, even if I am factor 2 to 3 high on my wild guess for effective density. Bigelow does claim a good radiation shielding effect for their B-330 design, one more than twice as good as their BEAM module at ISS, which has insulation layers only half a meter thick.

You have to have thermal insulation anyway, in order to have livable temperatures inside your shell. You have to have a meteor bumper anyway, or else you run the severe risk of a rapid depressurization event that kills people. You can do both with the very same layered-fabric approach. Why not use these same materials as your radiation shield, since they inherently also provide that function?

That leaves your windows and portholes as the actual radiation leak risks to any vehicle design. All you need is a closable cover on each window made with these same materials, and you have the radiation leak stopped.

The thermal problem requires one thickness of these materials. The meteor bumper problem requires another, different thickness. The radiation shielding problem requires yet another thickness. Just choose the largest of those three numbers and design with that! What could be simpler?

The biggest advantage of such a passive shielding approach is ZERO POWER DRAW! I would think everybody on these forums would be jumping all over this design approach to radiation shielding because of that zero power draw characteristic. I have been so puzzled as to why they are not.

Beyond that, just put your water and propellant tanks around living spaces, and get even more shielding effect. You have to have them anyway, why not place them where they do you this additional good?

I don't see this as a problem requiring any new technologies be developed at all. Certainly not technologies that need KW of power just to function. If you go that way with a shield that must draw power to function, and you have a power outage during a solar flare storm, then you will have a dead crew.

And don't tell me that won't happen, because Murphy's Law says it will.

GW

tahanson43206 · 2020-07-22 06:29:56

For RobertDyck re topic ...

Last night's local Linux Zoom meeting included discussion of barbering, and specifically the discussion led to "Flowbee" which is listed on Wikipedia, and has its own web site. The system is understandably out of stock due to the Covid-19 situation.

Apparently this product (or something similary) is in use on the ISS for hair care. The main benefit appears to be the immediate collection of fine particles which would be objectionable in the highly filtered air of the station.

It seemed to me that having something like this would be appropriate for the standard cabins in your inter-planetary transport vehicle.

***
In a previous Zoom meeting, a technology called "Magic Mirror" was discussed at some length. A 52 minute Zoom recording is available on YouTube, for anyone who might be curious to know what it is.

When I heard the presentation, I thought of your concept for large viewing "ports" in the inner cabins of your large inter-planetary passenger vessel.

For those who might not be familiar with "Magic Mirror", it consists of three components ...

The key concept is the use of two way glass for the outer surface of the display.

Behind that is a high definition display panel, such as a computer monitor or television flat panel.

The monitor is driven by a computer. In the case of the YouTube video, the presenter had loaded a Raspberry Pi with downloaded software to pull data from the Internet and display it on the screen.

In the case of the inter-planetary transport, the display could serve as a mirror to increase the sense of greater volume in the space, and then function as you have described earlier when power is on.

The advantage that occurs to me is that in power off mode the space occupied by the device would continue to function aesthetically.

(th)

RobertDyck · 2020-07-22 11:35:01

Cool. The only difference is instead of using "two way glass", it would use normal window glass. Well, the window has to retain air pressure against the vacuum of space, and survive micrometeoroids, so ideally use ALON (aluminum oxynitride), but reflectivity would be the same as a normal window. The reason is the "two way glass" is intended to appear as a mirror when there's no power. However, the spacecraft window would appear to be a window when there's no power. But yes, the display could do all those functions.

RobertDyck · 2020-07-27 13:55:55

Primarily for GW Johnson. I found the website about nuclear thermal rockets: Atomic Rockets
This lists Open Cycle MAX with Isp=9,990 seconds, thrust 3 million newtons, thrust power 0.15 TW, engine mass 15,000kg (15 tonnes), Thurst:Weight ratio 20, fuel uranium hexafluoride. Web page links to a report about Americium. Although the web page talks about Americium 241, if you read the actual report it says Americium 242m.

Calliban · 2020-08-03 10:24:09

Two articles on high power-density integral molten salt reactors.
https://www.nextbigfuture.com/2013/12/m … times.html
https://www.nextbigfuture.com/2013/12/c … power.html

The idea appears to be to mount the heat exchanger and compact power generation cycle inside the reactor vessel. The challenging thing about using this in a spacecraft is finding a power generation cycle that is efficient and can eject heat at high temperature, thus keeping the area of the radiator to a minimum.

Last edited by Calliban (2020-08-03 10:29:09)

tahanson43206 · 2020-08-03 10:48:48

For Calliban re #158

Thank you for those encouraging looking updates on molten salt reactors!

You are a practicing engineer, so I expect you to be skeptical of unproven research.

That said, are you aware of progress in understanding the quantum process that facilitates intake of heat photons and combining them (through their guided interaction with electron shells in selected molecules) to yield output at a higher energy (frequency) level?

I do not claim to understand much about the physics involved, but I ** am ** hoping the research will yield a practical way to avoid dumping (otherwise useless) heat energy into space, and instead harnessing it (or some part of it) to make useful photons, such as those suitable for capture by photoelectric cells.

There are several posts about this in the forum.

(th)

Calliban · 2020-08-03 13:05:09

tahanson43206 wrote:

For Calliban re #158
Thank you for those encouraging looking updates on molten salt reactors!
You are a practicing engineer, so I expect you to be skeptical of unproven research.
That said, are you aware of progress in understanding the quantum process that facilitates intake of heat photons and combining them (through their guided interaction with electron shells in selected molecules) to yield output at a higher energy (frequency) level?
I do not claim to understand much about the physics involved, but I ** am ** hoping the research will yield a practical way to avoid dumping (otherwise useless) heat energy into space, and instead harnessing it (or some part of it) to make useful photons, such as those suitable for capture by photoelectric cells.
There are several posts about this in the forum.
(th)

Sounds like an interesting technology. But there is no escaping entropy. Upgrading photons means taking low grade infrared light and converting it to shorter wavelengths. There is no way that this can work without increasing total entropy. I suspect that the only way you can produce one photon of short wave radiation is by downgrading a number of others which you then have to dump into space. That is the inescapable nature of the universe. Entropy always increases.

GW Johnson · 2020-08-03 13:30:11

Entropy (Second Law of Thermo) is why Edsel Murphy of Murphy's Law fame was an optimist. That and the Third Law of thermo.

First Law: you cannot win (easiest way to understand energy conservation)

Second Law: you will always lose (the proof gets clouded by the math of entropy in most texts, but that IS what it fundamentally means)

Third Law: you will always lose BIG-TIME / you cannot get out of the game (most folks have never even heard of this one)

GW

tahanson43206 · 2020-08-03 14:29:02

For Calliban re #160

Thanks for thinking about photon upconversion ...

I'll keep your concern in mind as I try to learn more. It is my understanding that NO energy is lost when events occur at the quantum level.

There is nothing to throw away, if I understand your meaning.

However, as I say, I'll keep your concern in mind.

(th)

Calliban · 2020-08-03 15:16:55

Getting back to the molten salt reactor, there would appear to be two factors that allow it to achieve uniquely high power density.

Firstly, the fuel itself is liquid, allowing it to serve as its own heat transfer medium to a heat exchanger immersed within the liquid fuel. The peak temperature of solid fuel is limited by the melting point of the fuel cladding. To prevent the cladding from melting, power generation rates can never exceed the rate of heat transfer from the cladding into the coolant. High heat transfer rates favour maintaining a high temperature gradient between the clad and coolant. However, high efficiency favours minimising temperature gradient and maintaining the highest coolant temperature possible. This sort of conflict does not exist if the fuel is also its own coolant.

Secondly, the entirety of the core volume is occupied by fuel. There is no need for separate coolant channels, because the fuel is the coolant. This means that every cubic centimetre of the core cam generate heat.

Hence, a liquid core nuclear reactor will generally have superior power density to a solid core reactor. The difficulty in space is that pumping or natural circulation in a liquid requires artificial gravity. Containing molten salt for any length of time requires high grade nickel alloys. And preventing life limiting corrosion requires careful control of the oxidation states of the molten fuel compound.

A molten salt reactor in a centrifugal configuration would make a good nuclear thermal engine because it should be possible to maintain a very strong temperature gradient between the outer and inner core. The outer core could have temperature beneath the melting point of nickel. The inner core could be close to the boiling point of the salt. Hydrogen gas would vent into the centrifugal void at the centre of the core, before exiting through a graphite or tungsten nozzle. Unfortunately, it is very difficult to design a model that achieves good thrust whilst containing fission products. The reason being that it would then require heat transferacross whatever barrier contains the fission products.

Last edited by Calliban (2020-08-03 15:23:21)

SpaceNut · 2020-08-03 19:52:23

The natural flow of molten salt is hot from the reactor but the spin is hot to cold as its forced outward by the spin, things that hot will be lighter while cold they are heavier which makes that to which is colder transit outward while spinning.

tahanson43206 · 2020-08-14 12:31:11

This is for RobertDyck re topic ...

Best wishes for your safe return from your current travel adventures in the far northern reaches of Canada!

In anticipation of your safe return, I am adding to my request for advice and counsel for design of the Big Wheel Passenger Transport vehicle.

I'm starting with the figure of 56 meters radius, published by GW Johnson in another topic.

In that post, GW Johnson reported 56 meters as the radius needed for the floor of a rotating habitat to deliver 1 g of simulated gravity (Void's term) at 4 rpm.

I am using that figure as the starting point for design of a 3D printable model. At 1:100 scale, that size is quite useful for a design with the tools I have available.

In a previous post, I asked you for your estimate of the optimum width for the floor of a first class cabin that stretches across the entire "floor" of the habitat.

In anticipation of future versions of the habitat, to offer slower and slower rpm as inducements for passengers to select one space line over another, I am expecting the width of the habitat would remain constant while the diameter would increase.

In a work session way from the forum, I made a list of issues/questions/concerns/opportunities ...

Item 1 is the width question, already described

Item 2 is: Plan for Lifeboat capability?

In a separate topic (Fast to Mars) kbd512 has described his vision of a large ship that could glide through an atmosphere on a one-way landing attempt if necessary. In this topic, and pending SpaceNut creating a new topic just for Big Wheel, I am imagining that the "floor" of the habitat would be filled with individual spacecraft/lifeboat/mobile-home-like compartments.

As a stretch exercise, I can imagine SpaceX Starship cylinders adapted for this purpose. The length of a starship is reported to be 50 meters.

Size
Second stage – Starship
Length 50 m (160 ft)
Diameter 9 m (30 ft)
Empty mass 120,000 kg (260,000 lb)
SpaceX Starship - Wikipedia

For what it's worth, the ratio between 50 meters and 112 meters is 2.24

If you were to select 50 meters as the width of the habitat disk, the cylinder generated in a 3D printer design program looks agreeable to my eye.

I'll try to post an image of the 50:112 cylinder later today.

Edit#1:

Getting back to the lifeboat design question ...

If the habitat is designed to accommodate a number of Starship second stage vehicles as passenger cabins, then there would be design questions to address for how to mount them in the circumference of the habitat so they can be released if need be with minimal difficulty. I would imagine a combination of manual locking mechanism (for backup) as well as explosive bolts for emergency deployment would make sense.

This post is getting longish, so I'll continue in another ...

(th)

Last edited by tahanson43206 (2020-08-14 13:01:41)

tahanson43206 · 2020-08-14 12:50:35

This is a continuation of Post #165 for RobertDyck

Other questions/issues/opportunities would include:

3) Plan for self sufficiency in flight (assuming 6 months using the generally accepted minimal energy path)

I would expect use would be made of the volume in the cylinder inside the outer ring of passenger cabins.

What stores of what items would be needed to insure a comfortable flight, without the need to open a service door to the habitat.

(as a reminder, the Big Wheel Passenger Transport design currently assumes only two sites where vacuum is exposed, at the ends of the axle of rotation)

I can imagine water (for example) moving from a reservoir (or several) of clean, potable water into a waste tank (or several) for cleaning service at a major destination port (such as Phobos or LEO).

4) Power in flight?

I can imagine a set of solar panels for normal power supply, as well as for topping off emergency batteries or other storage devices.

However, in anticipation of possible failures of the solar panel system, or an emergency, the passenger compartments(lifeboats) should be capable of sustaining themselves independently for some reasonable period of time.

5) Communication ... this subtopic has multiple aspects

a) With the propulsion/navigation unit

This would be a very high capacity Internet service for crew inside the habitat to be able to direct the activity of the propulsion unit.

(as a reminder, it is anticipated the crew could use a "Captain's Gig" for movement between the habitat and propulsion unit if necessary)

b) With Earth ... large dish antenna would seem appropriate ... these could be mounted on the Propulsion unit
c) With Mars ... the same or perhaps other dish antenna
d) With any other location ... these might be smaller and easy to maneuver as needed

6) Science enroute

The crew and passengers will have six months (or so) for useful activity while in transit. As a reminder, Benjamin Franklin carried out scientific research while travelling between the North American continent and Europe.

Mapping the Gulf Stream
Although Spanish explorers had described the Gulf Stream, Franklin, fascinated by the fact that the sea journey from North America to England was shorter than the return trip, asked his cousin, Nantucket sea captain Timothy Folger, to map its dimensions and course. Franklin published this map and his directions for avoiding it in the Transactions of the American Philosophical Society in 1786. Systematic research, conducted by the U.S. Coast Survey, of the Gulf Stream did not occur until 1845.

Benjamin Franklin. “Maritime Observations and A Chart of the Gulph Stream.” in Transactions of the American Philosophical Society. Philadelphia: 1796. Engraved map. Geography & Map Division, Library of Congress (40A) [gmd9/g9112/g9112g/ct000136]
Bookmark this item: //www.loc.gov/exhibits/franklin/franklin-scientist.html#obj40a

In the case of passengers and crew transiting from Earth to Mars and back, there will be ample opportunity to make astronomical observations in a wide variety of wavelengths. In addition, the moving transport could be a node in an interferometer:

VLBI reveals the universe in amazing detail | Astronomy ...earthsky.org › astronomy-essentials › how-vlbi-reveals-...
Jul 5, 2012 - Very Long Baseline Interferometry, or VLBI, is a powerful technique in radio astronomy. By linking together widely separated radio telescopes, VLBI allows astronomers to see the universe in more detail than ever.

(th)

RobertDyck · 2020-08-14 14:14:49

I'm back. I flew to Berens River, Manitoba, which is the southern most of the locations they send me to. It's an indigenous reservation; a year ago they actually built a road to the community. I know, that sound basic. Many of these northern communities have a gravel runway airport for propeller planes, and ice roads. An ice road is built on a lake, scraping off the snow in winter so the ice freezes to greater depth. Snow acts as insulation. An ice road can support the weight of an 18 wheel semi-truck. But Berens River has an all weather road; although I'm told it's gravel for a couple hundred kilometres. Next Monday/Tuesday I will be in Little Grand Rapids. That's one of the locations without an all weather road. Then either Tuesday/Wednesday or Wednesday/Thursday to Keewaywin (near Sandy Lake) Ontario. Their original schedule left me 2¼ hours to get from St Andrews airport to the Perimeter terminal of Winnipeg airport. Perimeter Airlines requires check-in 45 minutes before flight, so it's actually 1.5 hours. Taxi (or Winnipeg equivalent to Uber) takes 28 minutes between airports, so it works. But now they're talking of sending me from St Andrews Airport first thing Tuesday morning. And we're in negotiation for Bearskin Lake, Ontario. Woo hoo! More work. They pay me full days for these jobs, so it's quite lucrative. Haven't flown to a northern community since February; now they all want their equipment fixed all at once.

Ps. Manager at Berens River was a 20-somthing single woman. When I called for her to give me a ride to the hotel, she answered with a bedroom voice. Flirting.

RobertDyck · 2020-08-14 14:49:15

This topic started with the premise: Elon Musk said the next ship after Starship would be twice diameter and twice height, so 8 times volume. This ship was designed to have the same volume, but go from Earth orbit to Mars orbit and back, with artificial gravity. Ok, the hub would provide more volume than Starship 2, but still...

Radius from centre of rotation to surface of floor: 37.76 metres. 3 RPM. 38% gravity = Mars surface equivalent. One deck. Circumference: 237.25 metres. Ring width 19 metres. This allows 2 isles for cabins, corridors 1.5 metres wide, outside cabins have a window, inside cabins do not. Standard cabin size 4x2.4 metres. Cabins are also 2.4 metres (8 feet) high. These figures are from the initial post.

Cabins configures with short end along side wall, so outside cabins have 2.4 metres of exterior hull. Width of the ring is 4 metres for first cabin, plus 1.5 metres for corridor, plus 4 metres for inside cabin, then 4 metres for inside cabin facing the other corridor, then 1.5 metres for that other corridor, then 4 metres for the last outside cabin. Total 19 metre width. (Yes, Canada uses the British spelling for metre. But it's still pronounced "meter".)

Hohmann transfer orbit is minimum energy; it takes 8.5 months. "Express" trajectory requires 10% more propellant; it takes 6 months one-way from Earth to Mars. This is actually the "Free Return" trajectory. That means if something goes wrong, gravity of Mars will alter spacecraft flight path to return to Earth. It'll take more than 6 months to get back, but you'll get back when Earth is at that location. Getting back to Earth's orbit about the Sun when Earth is somewhere else in it's orbit is not useful.

Lifeboats: I hadn't considered that. Had instead focused on pressurized sections, redundant life support, and using the ship itself. You could add inflatable fabric rescue spheres. NASA developed a personal rescue enclosure (ball), but the ship could make them larger, able to accommodate several people.

Self sufficiency: My design would use parabolic mirrors on the sun-facing side of the ring to reflect sunlight into light pipes. These light pipes would direct sunlight to life support for each cabin. Each cabin would have it's own life support. Regenerable sorbent to remove CO2, dehumidifier to remove cabin humidity, urine processor for toilet, water processor to produce potable water. Instead of water electrolysis, each cabin would have a bag of in-vitro chloroplasts to convert CO2 and water into O2 and carbohydrate. The carbohydrate would be filtered, concentrated, then sent along a tube to ship's central life support. This will provide starch, but other food will be stored. Roof of the ring will have hydroponic greenhouses to grow fresh greens and tomatoes for salad. Other food will be stored. Dehydrated food to reduce mass, re-hydrated with recycled water.

RobertDyck · 2020-08-15 02:36:47

Lifeboats: The idea is based on lifeboats for an American aircraft carrier. A carrier doesn't have traditional boats, instead inflatable rafts. Stowed they look like this...
main-qimg-b17fc51f5d47c08fcf996102bbd76a7d
deployed...

Doing this for a Mars ship is more complicated. A space lifeboat has to provide air, water and food for a long time. Apollo used the LM as a lifeboat. That was a deliberate design decision by engineers. Apollo 8 was considered extremely risky because no LM was available; it was originally supposed to be an unmanned test of the CSM, but changed to manned after the Soviets did an unmanned test of their Soyuz capsule around the Moon and back. Apollo 13 had to use it. But how do you provide air, water and food in a lifeboat in space long enough for rescue? Apollo used a free return trajectory. My modification of Mars Direct would use a reusable in-space habitat, and the lander would go with the astronauts. Result is all food for the Mars surface stay plus all food for return are with astronauts at all times; if a free return is required, they have all that food. Robert Zubrin's Mars Direct placed the ERV ahead, along with food for return to Earth, so food for a free return becomes an issue. My architecture fixes that. But lifeboats for a large colonization ship? That will require more thought.

RobertDyck · 2020-08-15 03:19:51

4) Power. Yes, I was planning on solar. Spacecraft main engine would be open cycle gas core nuclear thermal rocket (OC GCNTR), but that means the reactor core is dumped when the engine is turned off. Trying to use one reactor for both propulsion and electrical power makes the reactor design complicated and heavy. And again, with gas core the reactor is non-operational when not providing thrust. I have suggested mid-course corrections with micro-fusion thrusters. That provides very short pulses, again no sustained reaction.

5) Communication. This depends on technology development, and how much you think will be developed soon. Realize quantum entanglement has been discussed since the late 1990s. Why hasn't it been developed by now? One possibility is the military already has it, but considers it classified. This provides instantaneous communication over great distance, theoretically interstellar. From the military perspective, it's secure, cannot be intercepted, cannot be detected. But if the military has it, why do they have humans on AWACS (air force) and Hawkeye (navy) aircraft? Mission control should be done from the ground, or an aircraft carrier ship. Sensors for AWACs or Hawkeye could be placed on an unmanned drone. I could give a long-winded explanation of my theory of physics; short version is using an entangled pair of electrons will have limited range. A pair of photons would have unlimited range, the range would literally be the universe. Electrons are a lot easier to control, you can use a quantum well of a microchip, but they behave randomly so will randomly break the quantum link. The greater the range, the more quickly they'll break the link. The link can be self-regenerating, but greater the range the more communication bandwidth is consumed just maintaining the link. You could use normal radio; NASA's deep space network obviously does communicate with Mars.

tahanson43206 · 2020-08-15 07:12:18

For RobertDyck re multiple posts on Large Ship design ...

This is just a note of appreciation for your series of additions to the topic.

It is good to see your vision develop.

(th)

RobertDyck · 2020-08-15 15:54:21

Ah hah! I posted this in another discussion thread. The "Intermediate axis theorum" could cause the ship to flip. But for the flip to happen, the object requires 3 different axes, all with different moments of inertia. I was worried that our ship would flip, because the propellant tank and engine section would be on one side of the wheel. But as long as the ship remains symmetrical about it's axis of rotation, then two of the axes have the same moment of inertia. That means it won't flip. So we can still have the fabric heat shield on the face of the wheel.

RobertDyck wrote:

The question is how much does the station move? If the station remains in fixed orbit, never moving, and always rotates in the same direction, then precession is not an issue. But there's another problem: if the rotating bit is asymmetrical, you can get the "Intermediate axis theorum". With Station 5 rotating while the second ring is only partially constructed, mass will not be perfectly balanced. This could result in the "flip" behaviour explained in this video. (14 minutes, 48 seconds)
The Bizarre Behavior of Rotating Bodies, Explained

tahanson43206 · 2020-08-16 05:56:40

For RobertDyck re #172 and gyroscopic stability

Thank you for continuing to press this issue. It seems to me that the stability we (humans) observe in commercially manufactured gyroscopes is likely to be the result of painstaking perfectionism in manufacture, so that rotating masses are of uniform density and uniform configuration.

Your reminder of the potential for instability (here and previously) is concerning (me at least) as I contemplate a rotating mass of significant size filled with people who move around, and all the masses they need to not only survive but enjoy six to eight months of travel from Earth to Mars.

kbd512 proposed counter rotating masses, and I can see that solution as having significant advantages, but the movements of mass inside each of the two rotators will (presumably) still lead to instability that will communicate itself to the adjacent rotor via the shared shaft. This constant force load would (presumably) exercise the roller bearings more than would have been expected if the rotors were of gyroscopic perfection.

***
Call for contribution by forum readers ...

At present this forum does not include a member with the capability to run a computer model of habitat modules rotating in either a single mode, or in the contra-rotating mode suggested by kbd512.

If there is a reader who could help with understanding of the situation, please consider registering and making a post or two.

This would be a (relatively) complex simulation program (as I am imagining it). The masses inside the rotor would be moving around at different rates and to varying degrees in a random manner, but (it seems likely) most of the activity would occur close to the outer rim of the habitat.

The information to be generated would inform designers of the forces that would ultimately arrive at the axle bearings of the system, where they would need to be addressed.

A strategy for mass management inside a rotating habitat that may be worth investigating is movement of mass (eg, water) to maintain a balance of the habitat as humans move about, or as mass is transferred from one location to another to meet requirements.

Energy required to maintain a balance in this manner (or in any manner) would be an investment in the safety and comfort of passengers that must be factored into the ticket price.

(th)

RobertDyck · 2020-08-16 21:45:41

Not to worry. A single wheel spacecraft designed so the largest moment of inertia is the axis about which the wheel rotates, makes that wheel stable. But a big rotating wheel acts as a flywheel, wants to continue to rotate in the same direction. Turning becomes an issue. The reason for counter-rotating wheels is to cancel that. But that raises issues of bearings and seals. I suggest keeping the wheel oriented aft toward the Sun the entire trip. Mid-course corrections applied to the hub so orientation doesn't have to change. Orienting the wheel only becomes an issue when preparing for aerocapture.

Maintaining orientation to the Sun has additional benefits. Only one wall needs radiation shielding. And solar collector. Remember, I said primary oxygen generation via bags of in-vitro chloroplasts. So sunlight directly powers oxygen generation.

tahanson43206 · 2020-08-17 07:59:53

For RobertDyck re #174 and topic ...

Thanks for continuing to develop your concept for a passenger transport. And thanks for your additional thoughts on stability of the rotation.

Your design has the distinct feature of a massive axle, as you point out.

You posted a sketch a while back. I'll try to find it.

http://newmars.com/forums/viewtopic.php … 64#p169464

Can I invite you to consider an update to the sketch, incorporating some of the ideas you've added in recent times?

An interior layout of the habitat portion would be particularly interesting. If you've already created such a layout and I missed it, then just post a link to the post.

Edit#1: for RobertDyle ... the image in the original post did not come up for me when I tried it today.

here is the link I pulled from the post:

https://scontent.fyyc2-1.fna.fbcdn.net/ … e=5F1EC4B4

(th)

Last edited by tahanson43206 (2020-08-17 09:00:08)

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