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#976 2021-12-07 21:51:04

tahanson43206
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Registered: 2018-04-27
Posts: 11,336

Re: Large scale colonization ship

For RobertDyck ... I heard back from Nathan at www.northhoustonspace.org.  I let him know about your talk on Large Ship.

There appears to be an opening for a speaker this coming Saturday at 3 PM Eastern Standard time (2 PM Houston time).

The web site is www.northhoustonspace.org

Update at 22:55 local time ... I just sent a message from NewMarsMember addressed to both of you.

Edit next day: As soon as the two of you connect, I will remove the email address above from the NewMars archive.

Update later: The Large Ship topic is booked for March 12th.

(th)

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#977 2021-12-19 19:20:30

tahanson43206
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Re: Large scale colonization ship

For RobertDyck...

kbd512 and I are scoping out topics for the Large Ship talk ... This is just a set of ideas ....

1) Overview
2) Life support
Why need large ship
Specific AG Mars equivalent
Atmosphere
Propulsion
Power
Food
Food on board and shipped with
Cabin/compartments
Crew/Passenger manifest
Radiation Protection Damage Protection
Hull Design

The talk is expected to be around 60 minutes with possible extension for questions

We are thinking about preparing 3 minute videos ahead of time (saving on YouTube) and offering 2 minutes between segments for questions. 

You could adjust the gap based on the number of questions.

Communications
Communications inside ship
Communications with Earth
Communications with Mars

Acceleration leaving Earth
Acceleration to Match Orbit at Mars
Operations ... multiple subtopics

Atmosphere
flammability
8 psi all
5 psi neutral gas
3 psi oxygen
.37
humidity is needed to help suppress flammability



(th)

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#978 2021-12-19 19:47:12

SpaceNut
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From: New Hampshire
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Posts: 26,331

Re: Large scale colonization ship

For me its how long to build, costs and launch count to deliver parts and pieces to make the ship.

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#979 2021-12-19 21:01:30

tahanson43206
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Re: Large scale colonization ship

For SpaceNut re #978

Those are useful items to add to the plan for the presentation on March 12th.  The question for RobertDyck is where those items would fit in an hour presentation.  As things are shaping up, each of the bullet points could develop into a full hour all by themselves.

The Zoom meeting is still underway.  GW Johnson joined one hour in, at 21:00 Eastern Time.

With GW's arrival, the group spend a ** lot ** of time working through various trajectories for the flight to Mars.

Mass figures were flying hot and heavy for a while.  It seemed to me the questions around mass were left unanswered.

They need to be resolved by March 12th.

It is UTC 3:01 according to time.is/utc

(th)

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#980 2021-12-19 21:43:17

RobertDyck
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Re: Large scale colonization ship

References
Energia Corporation: Mars mission plan
Princeton Satellite Systems: Direct Fusion Drive
Micro-fusion Thruster: Engineering of the Magnetized Target Fusion Propulsion System

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#981 2021-12-19 21:57:04

tahanson43206
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Re: Large scale colonization ship

Update on the Zoom meeting 2021/12/19 ... kbd512 has been leading an extended discussion of the practicality of huge thin film solar power collectors to drive ion thrusters for the Large Ship.

Unfortunately, there is no one taking notes, so all this hard work is going to disappear into the wake of the Zoom session.

(th)

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#982 2021-12-19 22:15:54

RobertDyck
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Re: Large scale colonization ship

Life Support for 12 people assuming the same technology as the US side of the International Space Station. Equipment purchased from Hamilton Sundstrand.

toilet: 375 watt peak, 0.071875 kWh per day
water processor: 915 watt peak, 1.40 kWh per day
urine processor: 424 watt operating, 108 watt standby, 255.2 watt continuous
oxygen generation: 1.73 kW continuous
CO2 removal: 0.259 kW continuous
dehumidifier: 0.6 kW continuous
circulation fan: 0.312 kW continuous

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#983 2021-12-19 22:31:51

RobertDyck
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Re: Large scale colonization ship

In post #293 I had posted one fan graphics with proposed floor plans for passenger Starship. This shows a configuration for Mars with 100 passengers and life support. How many could fit with airline seating for a trip to LEO?

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#984 2021-12-21 01:02:26

kbd512
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Re: Large scale colonization ship

Post moved to a separate thread.

Last edited by kbd512 (2021-12-21 09:09:00)

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#985 2021-12-21 03:11:56

RobertDyck
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Re: Large scale colonization ship

kbd512:
Yup, you are trying to radically change what this project is all about. To complete anything you have to stick to what you're trying to do. This is a passenger ship, it isn't a military vessel. It's a ship, not a tent. It isn't going to use solar electric propulsion because that's too slow. As GW Johnson pointed out, that requires a slow spiral out of Earth orbit through the Van Allen belts, exposing passengers to lethal radiation. And no, we aren't going to use kilometre wide solar panels of gossamer thin material that will only get shredded by micrometeoroids.

NASA placed the Long Duration Exposure Facility in space in April 1984. It had panels of several materials, originally planned to be left exposed to space until March 1985, but due to the Challenger accident it wasn't retrieved until January 1990. Panels of thin film material came back like this...
ldef1.jpg

You claimed 50m³ per person is extremely generous. My plan includes a cabin 2.43m x 2.4m x 4m to house 6 bunks plus washroom. That's 3.888m³ but then add corridor, dining rooms, kitchen, gym, etc. The habitation ring is 37.6992m radius x 19m wide x 2.43m high. But add 12cm width for the water wall. Area of a circle is π x R², area of a ring is area of a circle to the floor subtract area of the cut-out. Volume is that area x width. So (π x 37.6992²) - (π x (37.6992 - 2.43)²) x 19.12 = 10583.87 m³ for 1,000 passengers plus 66 crew. That's 9.991292 m³ per person. Then add the spokes, the second level for observation rooms, greenhouses, and advanced life support. And the central hub, and zero-G cargo. It's quite big. I don't know where you get 50m³ per person, it is extremely generous.

Propulsion: you mentioned M2P2, that's Mini-Magnetosphere Plasma Propulsion. It uses a magnetic field filled with a thin ionized plasma to produce a mini-magnetosphere, then that rides solar wind for propulsion. It's extremely slow. Whenever you have humans onboard, you can't be slow. Humans are vulnerable to radiation, and require food. Mass of food counters savings for propellant.

You also mentioned MagBeam. What is that?

Radiation shielding: my design orients one wall toward the Sun at all times. That allows shadow shielding. With shadow shielding, you don't need 360° shielding, just toward the Sun. My design orients one wall for the entire habitation ring toward the Sun. So if an SPE hits, all other areas of the ship would be off limits. But most passenger facilities are in the habitation ring, so that leaves passengers with a large and luxurious area to shelter.

Yes, use Mini-Magnetosphere for radiation shielding, which will shield against GCR. No, I don't expect it to completely eliminate all radiation. Reducing radiation to the level of ISS is enough. That means blocking 2/3 of GCR in interplanetary space. University of Washington worked out a design intended for a small spacecraft that only uses 50kW of electricity to maintain the magnetosphere. That would work for a Mars Direct habitat. This ship is a lot larger, but the Mini-Magnetosphere extends to multiple kilometres from the ship. So I don't know how the large ship would affect the Mini-Magnetosphere. Another issue with a magnetosphere (mini or otherwise) is radiation will be concentrated at the poles of the apple shaped field. On Earth that radiation enters our atmosphere, exciting gasses of the upper atmosphere creating aurora. For a Mini-Magnetosphere of a ship the pole areas would be dangerous. The aft end of the ship is protected by the propellant tank, but the forward end is not. That means the zero-G hub must be off limits during an SPE.

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#986 2021-12-21 03:58:02

RobertDyck
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Re: Large scale colonization ship

In post #387 I cited a trajectory from the NASA trajectory browser. One example: Earth departure Nov-02-2024, Mars arrival Apr-27-2025, duration 176 days, injection ΔV 4.34 km/s. NASA assumed injection from Earth orbit at 200km altitude. We would more likely start at 400km altitude, but for now let's just use these numbers.

I had originally assumed main propulsion would be Open Cycle Gas Core Nuclear Thermal Rocket. Using figures from the NASA study of the early 1990s. That estimated Isp of 9,000 seconds. Using that, assuming total ship dry mass of 10,000 metric tonnes, propellant required would be 505 tonnes. Liquid hydrogen is 71 kg/m³, so this requires 7,112.676 m³. Assuming the propellant tank is 9m diameter, it would have to be 111.8 metres long. SpaceX Starship is 9m diameter x 120m long. It would require 5 trips of SpaceX starship to deliver enough propellant.

Of course the fact an GCNTR uses highly enriched uranium would be an issue. Solution is to launch reactor fuel from Russia. I did look at cost of reactor fuel. Plutonium requires a lot less for the minimum critical mass to get the reactor to start. Cost per kg is higher than uranium, but total cost of sufficient fissile material to get the reactor to start is actually lower. There are other exotic fissile materials that require even smaller critical mass, but their cost per unit mass is so high that total cost for the reactor is higher. Changing to plutonium could be an issue. Plutonium boils at 3,230°C while uranium boils at 3,900°C. So that's not a problem. Uranium hexafluoride (UF6) is used to get the reactor to start, because it's a gas at moderate temperature. It will dissociate into uranium and fluorine gas when at operating temperature, the fluorine will be lost with exhaust gas. UF6 boils at 56.5°C, PuF6 boils at 62°C. So the only remaining issue is design of a vortex to keep plutonium in the reaction chamber while hydrogen injected as liquid into the doughnut hole will expel hydrogen gas out the exhaust nozzle while retaining the fissile core. Critical mass of a bare sphere of U-235 is 52kg, while Pu-239 10kg. Critical mass of Pu-238 is between 9.04 to 10.07 kg, according to Wikipedia which cites the U.S. Department of Energy: Office of Scientific & Technical Information. Critical mass can be greatly reduced by a neutron reflector, usually beryllium, but critical mass is also affected by density. The reason for the range for Pu-238 is crystal phases can have significantly different density. Gas obviously has low density. High pressure in the combustion chamber will increase density, but even high pressure gas will still be lower density than any phase of solid.

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#987 2021-12-21 06:41:08

Calliban
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From: Northern England, UK
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Posts: 2,073

Re: Large scale colonization ship

The hydrogen propellant is a very efficient moderator.  Changes in flow rate will result in reactivity swings.  Then again, temperature changes reactivity as well.  In the slow spectrum, with 238U present, temperature reactivity coefficient is negative.  In the fast spectrum, the number of neutrons released by fission increases with neutron energy, so temperature coefficient can be positive.  However, this effect is usually more than overwhelmed by the additional neutron leakage resulting from fuel thermal expansion.  Suffice to say, the neutronic analysis for something like a nuclear thermal engine will be complicated.  Generally, introducing moderation increases fuel reactivity and reduces critical mass.


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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#988 2021-12-21 07:43:38

tahanson43206
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Registered: 2018-04-27
Posts: 11,336

Re: Large scale colonization ship

This post is reserved for notes from GW Johnson from his participation in the recent Zoom meeting.

he sent them by email, and I'll post them here later today.

I'd like to see progress in building a set of videos starting next week.

We have plenty of time to prepare a very high quality presentation, if we can stay on track.

The introduction of a completely new concept is interesting but it is a distraction.

I ** do ** think the ideas of kbd512 deserve consideration and development, but that would best be done in a separate topic.

The mass that RobertDyck needs is what it is.  The propulsion system needs to be sized to match, and (of course), in real life, it ** will ** be sized to match, because physics demands it (a) and (b) the passengers are going to have a vote.

The following notes from Sunday's Zoom were contributed by GW Johnson:

it takes far fewer Starship/Superheavy launches to load up a big ship in orbit,  to send a 1000 people to Mars,  than it does to send those same 1000 people to Mars directly in Starships.  It is the refueling tankers per flight-to-Mars that make this true by about a factor of 6 to 8 or thereabouts.  Going only to orbit with Starship requires no tankers at all. 

The number of tankers depends on the payload to Mars.  If only ~100 tons,  a partial refill with 3-4 tankers is adequate.  If 100+ tons,  you need a full 1200 ton refill,  at about 150-200 tons per tanker.  That's all figured at Raptor-1 SL & vac engine performance,  and 120 ton inert mass for Starship.  As near as I can tell,  my numbers are now obsolete with the advent of Raptor-2,  about which I know nothing.

We didn't talk about this,  but it will require some Starships based and fueled on Mars to unload those same 1000 people.  Those can be flown single-stage round-trip from the surface to orbit and back,  refueling on the surface from an appropriate tank farm.  The only kicker will be landing with a full payload of 200+ people.  Kbd512 thinks 500 can be stuffed into the space.  I'm not so sure,  especially if they need to ride in pressure suits.

I would like to add another contribution of GW Johnson, which I heard over FM Radio broadcast of the Zoom session:

The subject of navigation of a rotating ship came up ... GW Johnson suggested a separate navigation "ship" travelling with the rotating passenger vessel.  The purpose would be to maintain accuracy of the Large Ship inertial navigation system by providing star fixes at frequent intervals

I like this suggestion because it matches up nicely with my previous posts in this topic, about providing fixed star observation capability flying along with the Large Ship.  The passengers are NOT going to be doing celestial observations from within the Large Ship itself.  However, a mini-Hubble flying next to the Large Ship would provide plenty of stable observation capability for the passengers and crew, and the 24*7 observations would be stored in digital form for anyone to review over the flight of the convoy.

The research/entertainment observations could be interspersed with the navigation observations, so the same instrument could be used for both purposes.

(th)

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#989 2021-12-21 09:11:39

kbd512
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Re: Large scale colonization ship

tahanson43206,

Replies moved to another thread.

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#990 2021-12-21 10:17:44

tahanson43206
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Re: Large scale colonization ship

For kbd512 ... just a detail ... were the posts "copied" to the new topic, or "moved"?

The posts were part of the history of this topic, so it would be reasonable for them to remain in place.

I could check, but have other things to do, so will simply ask.

(th)

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#991 2021-12-21 10:22:44

tahanson43206
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Re: Large scale colonization ship

For RobertDyck,

You have my continued support for your original concept, as modified by ** you ** over time. 

The talk you are scheduled to give will feature elements you want to retain over the long term.

I would encourage you to add as much mass as you need to create a vessel that decision makers will recognize as worthy of their investment.

The problem of accelerating that mass (whatever it turns out to be) is not something to worry about at this stage.

The Queen Mary could have been imagined in the Age of Sail, but the steam engines and other advanced technology were not available.

We can already see signs of what advanced propulsion will look like, so I am hoping you will stay ON COURSE and finish development of your vision in time for March 12th.

(th)

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#992 2021-12-21 10:28:01

tahanson43206
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Re: Large scale colonization ship

For RobertDyck ...

Here is a short list of distinguishing features of the Large Ship design you have been developing, as I remember them:

1) Mars Gravity in Habitation Ring
2) 20 second Rotation
3) Cabins arranged in groups able to seal for safety if necessary
4) Excellent food including fresh food
5) Plenty of power, communication, entertainment
6) Radiation protection
7) Exercise opportunity
8) 1000 passengers
9) 60 crew
10) 2 year fail-safe flight plan

That is just a top-of-mind list ... please ** do ** create a short post with a similar list for all to see as a "RobertDyck" class passenger ship for Mars service.

As soon as you are ready, I'd like to get your detailed specifications out in public view before someone else shows up to claim the spotlight.

(th)

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#993 2021-12-21 12:03:29

RobertDyck
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Re: Large scale colonization ship

tahanson43206,

You mentioned GW Johnson's idea of a drone flying beside the ship to provide star sight for navigation. As I told him at the time, excellent idea! But your post takes it a step farther, you suggested a mini-Hubble. That's also a great idea! I want telescopes on the observation deck so passengers can observe the stars. Amateur astronomers will find the absolute greatest "seeing" on the ship: no clouds, no atmosphere, and stars are visible 24/7. You literally are in space. The concern is a polar mount for the telescope to counter the rotation of the ship, so the telescope can remain fixed on one celestial target. I did suggest a telescope with digital image sensor that can be remotely operated, so anyone with an iPad or tablet on the ship can use it. A mini-Hubble detached from the ship and running parallel would completely resolve the issue of rotation. This would be great for amateur astronomers, they would literally have access to a space telescope.

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#994 2021-12-21 12:51:52

tahanson43206
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Posts: 11,336

Re: Large scale colonization ship

For RobertDyck re #993

It is rewarding and encouraging to see the pace of development of your ideas picking up speed.  While kbd512 may well be putting his considerable energy into a competitive design, I think you have the "luxury" liner concept all to yourself!

I am ** also ** greatly encouraged by the offer of Calliban to take a look at the propulsion system that will be needed for your vision to come to pass.

My recommendation (and hope) is that you will work on the "ship" and let the propulsion requirements fall out of whatever you decide to include.

(th)

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#995 2021-12-22 19:15:48

SpaceNut
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From: New Hampshire
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Posts: 26,331

Re: Large scale colonization ship

We have made note of the need for a washing machine to reduce the amount of clothing required for a mars mission and Nasa estimates that it will need approximately 500 pounds of clothing per astronaut for a three-year trip to Mars.

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#996 2021-12-23 00:00:01

RobertDyck
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Re: Large scale colonization ship

NASA doesn't do laundry, they wear one set of new clothes until they're too stinky, then throw them in the garbage and open the next set. kbd512 suggested military clothes. Some individuals are a "clothes horse", way too many clothes. I suggested storage in an economy cabin would be under the mattress plus one row of drawers. The under mattress compartment would be 75" x 30" x 4". Space for drawers would be 75" x 30" x 20", however each row is half that height, and subtract thickness of drawer bottom/sides/back, and space for drawer slides. What does that leave? For an economy cabin, this is all the storage space per person. That must include all clothing you will wear on the entire trip, plus toiletries, plus any other personal items. I suppose a the washroom could have a medicine cabinet on the wall over the sink for toiletries, but that space would be shared with everyone in the cabin.

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#997 2021-12-23 04:27:25

Calliban
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From: Northern England, UK
Registered: 2019-08-18
Posts: 2,073

Re: Large scale colonization ship

RobertDyck wrote:

NASA doesn't do laundry, they wear one set of new clothes until they're too stinky, then throw them in the garbage and open the next set. kbd512 suggested military clothes. Some individuals are a "clothes horse", way too many clothes. I suggested storage in an economy cabin would be under the mattress plus one row of drawers. The under mattress compartment would be 75" x 30" x 4". Space for drawers would be 75" x 30" x 20", however each row is half that height, and subtract thickness of drawer bottom/sides/back, and space for drawer slides. What does that leave? For an economy cabin, this is all the storage space per person. That must include all clothing you will wear on the entire trip, plus toiletries, plus any other personal items. I suppose a the washroom could have a medicine cabinet on the wall over the sink for toiletries, but that space would be shared with everyone in the cabin.

You could engineer a hold area for some personal items, outside of the habitat ring.  This would be zero-g and very lightly pressurised, to prevent polymers from subliming into vacuum.  This is essentially how baggage is transported on aeroplanes.


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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#998 2021-12-23 06:30:52

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 7,320
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Re: Large scale colonization ship

Yup. The central hub will have 3 areas: front of the ship will be a zero-G hub, which acts as reception area when passengers arrive, and zero-G play area during the trip. Aft of that is the zero-G cargo hold. It holds the bulk of the stored food, spare parts for ship repairs, and passenger cargo. Only crew can access the cargo hold, not passengers. It is pressurized, but acts much like the cargo hold for modern passenger aircraft. Aft of that is the propulsion stage, which holds propellant and main rocket engines. The propulsion stage will be detachable so it could be replaced if new technology is developed.

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#999 2021-12-23 07:28:31

tahanson43206
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Posts: 11,336

Re: Large scale colonization ship

For RobertDyck re SpaceNut's suggestion of a washing machine service ...

You are not bound by NASA practice.  A facility for cleaning clothing is a minimal expectation on a large ship of any kind, unless it is a ferry boat used for crossing a river or similar short run.

The idea of not being able to clean clothing for a two year trip is NOT new.  Sailors have been dealing with ** that ** problem for centuries.

Hopefully by the time your ship is flying, you will have run across a solution that allows your passengers to sustain a minimal sense of "civilization"

kbd512's ship, in contrast, will be a minimalist venture, so I would not expect washing machines.

Nanotechnology is advancing rapidly on multiple fronts.  Self-cleaning fabric is not out of the question.  Just plug in your coverall when you hit the sack, and it will remove all molecules it doesn't recognize overnight. 

For SpaceNut ... self cleaning garments would appear to be a potential product specialization on Earth.

(th)

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#1000 2021-12-23 09:56:36

tahanson43206
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Re: Large scale colonization ship

For RobertDyck ... re companion vessel ...

The image that came to mind just now is dolphins accompanying a whale ....

RobertDyck wrote:

tahanson43206,
A star-sight telescope could have small solar panels of it's own, and batteries. It doesn't need to transfer power. Use reaction wheels for orientation, which consume electric power, no propellant. Some propellant will be required for manoeuvring, and if the tiny space telescope is out for long it will have to desaturate reaction wheels. Transfer propellant from the main ship? That requires periodic docking.

There might be more than one non-spinning companion vessels traveling in a convoy with Large Ship.

For one category, in addition to the Navigation/Observation vessel, the landers could fly with the Large Ship.  There is no need for them to be spinning, and they can take care of their own propulsion, which would reduce the burden on the passenger vessel.

Your post above is in reply to a post about technology to assist with communication between a rotating component and a non-rotating component.

It is possible that digital communications flows between the rotating system and the non-rotating one will not require special knowledge or expertise.

My reason for posting the excerpt about engineering in such situations was for awareness, in case the engineering staff runs into a problem.

Programming thrust activity on the Large Ship is going to require a level of expertise and skill not currently available to the Large Ship project, but there is clearly a need for such expertise.

(th)

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