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#26 2019-09-05 17:00:34

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 17,333

Re: Large scale colonization ship

For mars a ship landing with those diameters will be with no parachute and use fuels for the landing.
The heat shield even being made of light weight Pica X will still get to an impressive mass due to the size of the shield needed.
The ship's on orbit entry mass will also be quite heavy as a result of water and supplies that it would have as well for the support of those onboard.

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#27 2019-09-05 17:17:30

RobertDyck
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Re: Large scale colonization ship

This is for a ship that travels from Earth orbit to Mars orbit and back. Over and over again. Why would you think it lands?

I suggested using SpaceX Starship as reusable shuttle to carry 100 passengers at a time to LEO. And the fuel tanker version to refuel the colonization ship.

Here's a question: how much mass could Falcon Heavy lift to 400km @ 51.6° inclination with all 3 core stages recovered? The published lift to LEO is to 185km @ 28.5° inclination and with all core stages expended. With passengers in seats and nothing more, how many passengers could it carry?

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#28 2019-09-05 17:38:11

SpaceNut
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Re: Large scale colonization ship

I miss read the aerocapture as the desire to land.
Its still will need a heatshield for that breaking in either case.

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#29 2019-09-05 17:47:38

tahanson43206
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Registered: 2018-04-27
Posts: 1,615

Re: Large scale colonization ship

For RobertDyck re topic and aerobraking specifically ...

The arrival of a ship this size will be a noteworthy event on Earth for sure, and eventually it will be noteworthy on Mars as well.

I assume part of the navigation skill will be to arrive so that the bulk of the braking takes place over oceans.   

For the people on the vessel, it should be an exciting part of the trip.

For the navigator, it would be the part of the trip where the rank and privileges of the office will be truly earned.

(th)

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#30 2019-09-05 18:13:45

RobertDyck
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Re: Large scale colonization ship

SpaceNut: I said the heat shield will be a fabric parasol. I get this idea from Mars Direct. Mars Direct was written to use ADEPT, a carbon fibre fabric heat shield that opens like an umbrella. This provides greater surface area, which permits landing a larger/heavier vehicle. But I suggested using Nextel 440, a synthetic ceramic fibre that NASA's Ames Research Centre developed as part of a new thermal blanket for space shuttles. It was never installed on Shuttle, it was developed too late, but can handle more heat than the AFRSI heat shield that Shuttle used on its white areas. Carbon fibre can withstand more heat than Nextel 440, but not as reusable. Carbon fibre tends to become stiff / brittle after extreme heat. So carbon fibre is great for single use, such as landing a Mars Direct habitat. By the way, the NASA guys working on ADEPT estimated the landing mass to be much greater than the landed mass of a Mars Direct habitat. But I want to use Nextel 440. The artificial gravity ring will enter face-on, the fabric heat shield will cover the entire diameter of the ring. We're talking BIG!

And aerocapture means dipping into the atmosphere to produce aerodynamic drag, which will slow the ship. Aerocapture involves slowing enough to enter orbit. That's typically followed by repeated aerobraking to drop the apogee. Passing through the cloud of satellites in Earth orbit will require some serious navigation skill.

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#31 2019-09-06 05:09:18

tahanson43206
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Re: Large scale colonization ship

For RobertDyck .... Thanks for noting the cloud of Satellites .... I understand the Indians just (or recently) created a vast cloud of debris by running an anti-satellite test.  This would be in addition to any debris left over from the Chinese test a couple years back.

For SpaceNut .... Could you possibly find a video of the asteroid breakup over Russia that took place (relatively) recently.  I think it shows what an exciting event it would be for a Mars ship to perform aerobraking over land.  The difference would be that (unlike the asteroid) the ship would hold together after its run through the atmosphere, so that the light show (and possibly sound effects?) would be visible longer and for more people.

Media coverage of the event would (presumably) be extensive, and few Earth people would not be aware of the approach of the ship, the first pass, and possibly subsequent passes as the vehicle slows down.

(th)

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#32 2019-09-06 05:41:55

Terraformer
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From: Lancashire
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Posts: 3,160
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Re: Large scale colonization ship

This discussion is about a practical ship for large scale colonization. Not somebody's wet dream. We aren't going to build another space station. Not at Earth-Moon L1, not Earth-Moon L2, not anywhere else.

In that case, we're not going to build a giant colony ship either. If we can do that, building a proper spacedock is easy in comparison.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#33 2019-09-06 11:32:01

RobertDyck
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Re: Large scale colonization ship

Anything that even smells of the 90 Day Report is bad and has to be killed.

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#34 2019-09-06 12:21:10

Terraformer
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Re: Large scale colonization ship

So no big colony ships then.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#35 2019-09-06 12:31:15

GW Johnson
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From: McGregor, Texas USA
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Posts: 3,754
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Re: Large scale colonization ship

Re discussion of NERVA in post 22 above:

David Buden's book "Nuclear Thermal Propulsion Systems" (published by Polaris Books) gives a pretty good description of the Project Rover and related stuff,  including Timberwind.  Buden worked on Rover.  He is one of 3 or 4 surviving engineers who did so.  I met him at the Mars Society convention in Dallas a few years ago.

Rover had several test series where they rooted out the very challenging problems.  There was Kiwi,  Phoebus,  Peewee,  and NERVA,  each in multiple versions.  NERVA was restartable (one version started 28 times,  and another one burned for 47 minutes).  NERVA was not combined with electric power generation in actual testing,  that was a possible design modification explored but not built and tested. NERVA was also throttleable. 

The NERVA-powered nuclear stage was a lengthened replacement for the S-IVB LOX-LH2 stage on Saturn V.  It was definitely restartable.  NERVA was considered ready for its first flight test as a nuclear 3rd stage on the Saturn V,  when the nuclear propulsion program was shut down,  circa 1974.  There was extensive flight safety and self-destruct built into this nuclear upper stage design for Saturn V.  It did NOT involve activation of the reactor only to leave LEO on the way to "elsewhere". 

Re Timberwind:

Buden describes Timberwind in his book.  Timberwind was a Strategic Dense Initiative effort to look at a nuclear boost vehicle for a very high-energy strategic defense kill vehicle.  Timberwind was tested as components and specific test devices,  uncovering multiple serious problems that were never resolved.  No engineering prototype engine was ever built.  The Timberwind design was not restartable,  and it was not throttleable either.  That's not to say the Timberwind design cannot eventually be made to work,  because it can.  However,  this was never done.  It's still a huge effort to do. 

Re the nuclear explosion drive: 

Toward the end of his book,  Buden describes briefly the other pebble bed core,  liquid core,  and a couple of gas concepts for nuclear thermal propulsion,  and even the old "Project Orion" nuclear explosion design very briefly.  The pebble,  liquid,  and gas core ideas are concepts,  not tested designs.  They have much difficult basic feasibility work to do before any development work, all before any engineering prototype engines could be built for test. 

The nuclear explosion drive is different.  Buden describes the small Mars mission design,  under consideration by NASA circa 1975.  You need to look at another source to understand that program.  I would suggest "Project Orion - the True Story of the Atomic Spaceship" by George Dyson.  George is physicist Freeman Dyson's son.  Freeman Dyson was one of the team that worked on old "Project Orion". 

The testing they got done demonstrated the feasibility of explosion propulsion,  the survivability of the pusher plate,  and the shaped-charge fission devices necessary to make this thing work.  The pusher plate is a shadow shield for the neutron flux from the explosions.  They were ready to build a prototype;  something much larger than the NASA Mars mission version.  But they never got to do it.

Re big colony ship design: 

You need something the size of an ocean liner or medium warship to do that mission.  It is better done as an orbit-to-orbit transport,  not actually landing by itself.  You need appropriate landers at destination.  Every destination is different.  These should be reusable and reflyable. 

Nuclear thermal is a possibility to make one-stage two-way lander operation possible at Mars with high payload fraction.  It can be done with storable chemical rockets,  but only at payload fractions in the 1-2% class.

Whether you can use aerobraking to slow your colony ship into orbit is an open question.  All material technologies suffer from square-cube scaling laws,  while intrinsic material strengths are fixed.  You can only make your heat shield parasol so big,  and I doubt that we know yet how big that is.

Re the 90 Day Report:

We are not ready to build such big colony ships yet.  When we are,  no one will care about the 90 Day Report.  NASA will not be the entity that builds and operates such a thing.  This is going to come from the likes of Spacex,  Blue Origin,  etc,  although probably NOT specifically them. 

We may or may not live to see this happen.    But,  I stand by my suggestion that these colony ships be nuclear explosion drive items made on Earth,  launched from Earth,  and then operated as orbit-to-orbit transports.  If your vehicle is big enough,  and tough enough,  its hull is its own radiation shield,  and likely strong enough to do aerobraking without resort to parasols.  We'd likely need only 2 or 3 of them.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#36 2019-09-06 13:48:37

RobertDyck
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From: Winnipeg, Canada
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Re: Large scale colonization ship

RobertDyck wrote:

Anything that even smells of the 90 Day Report is bad and has to be killed.

Terraformer wrote:

So no big colony ships then.

The 90 Day Report does not mean going to Mars. The 90 Day Report means spending copious gobs of cash and going nowhere. Look what happened with VentureStar / X-33, and US Space Station Freedom, and Ares V, and DC-X/DC-XA. Gobs of cash spent, no results. The guys pushing the 90 Day Report are the same guys behind these past fiascoes.

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#37 2019-09-06 16:10:24

SpaceNut
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From: New Hampshire
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Posts: 17,333

Re: Large scale colonization ship

The money makers are the pork generators that we still go to for what is needed for space when it comes to Nasa.

When other companies turn into providers of a supply train of commodities then it will change.

example bigelow's inflateable, Space x Falcon 9 Dragon cargo, Once was ATK for cygnus which can be launched on just about anything....

With hopefully the next tier coming for manned flight but we are in a holding pattern....

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#38 2019-09-07 07:51:54

tahanson43206
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Registered: 2018-04-27
Posts: 1,615

Re: Large scale colonization ship

For GW Johnson ...

I was ** really happy ** to see your support of RobertDyck with nuclear fission propulsion in general, and with a variety of variations on the theme.

Thanks for the reference to David Budin's book, which I will try to find.

I am the proud owner of a copy of Dr. James Dewar's book on fission propulsion, and will be happy to (at least try) to answer any questions a forum participant may have about it.  If you (the reader) are not yet a member of the forum, and if you are not a spam artist, AND if you are in a position to contribute to this topic launched by RobertDyck, please do register.  If (as occasionally happens) you run into a bug with registration, you can send email to the site administrator using the contact option in the registration/login feature.

I'll add a bit of information about Dr. Dewar below the quote from GW Johnson:

GW Johnson wrote:

Re discussion of NERVA in post 22 above:

David Buden's book "Nuclear Thermal Propulsion Systems" (published by Polaris Books) gives a pretty good description of the Project Rover and related stuff,  including Timberwind.  Buden worked on Rover.  He is one of 3 or 4 surviving engineers who did so.  I met him at the Mars Society convention in Dallas a few years ago.

Rover had several test series where they rooted out the very challenging problems.  There was Kiwi,  Phoebus,  Peewee,  and NERVA,  each in multiple versions.  NERVA was restartable (one version started 28 times,  and another one burned for 47 minutes).  NERVA was not combined with electric power generation in actual testing,  that was a possible design modification explored but not built and tested. NERVA was also throttleable. 

The NERVA-powered nuclear stage was a lengthened replacement for the S-IVB LOX-LH2 stage on Saturn V.  It was definitely restartable.  NERVA was considered ready for its first flight test as a nuclear 3rd stage on the Saturn V,  when the nuclear propulsion program was shut down,  circa 1974.  There was extensive flight safety and self-destruct built into this nuclear upper stage design for Saturn V.  It did NOT involve activation of the reactor only to leave LEO on the way to "elsewhere". 
<snip>
GW

Quoting from The Space Show web site:

James A. Dewar worked exclusively on nuclear policy issues in the Atomic Energy Commission and its successor agencies, the Energy Research and Development Administration and the Department of Energy. Such included nonproliferation and export control, nuclear testing and verification, international, environmental, nuclear fuel cycle, intelligence and technology transfer from the nuclear weapons complex. He held a Q clearance, with Sigma access, as well as many intelligence clearances. He graduated from Augustana College in Rock Island, Illinois in 1966 with a BA, the University of Wisconsin in Madison, Wisconsin in 1968 with a MA and Kansas State University in Manhattan, Kansas in 1974 with the PhD. He began his government career and interest in nuclear rocketry in 1969 as a summer intern in NASA.

To see the full list of Space Show episodes in which Dr. Dewar was the guest, use:
https://www.thespaceshow.com/guest/dr.-james-.-dewar

For SpaceNut .... I'd like to invite you to consider Dr. Dewar as a guest speaker.  Our first attempt to set up a guest speaker failed, but the mechanism is in place and ready for use.

For those who are (rightly) concerned about emissions of radioactive particles and potent radiation from a nuclear rocket, I would like to point out that the ship's navigator can choose points in the orbit where fission propulsion can be initiated so that output is directed to outer space, away from all human occupied locations in the Solar System.  In the case of an approach to Earth from Mars, instead of initiating the burn before arriving at Earth, the navigator can wait until the ship has passed the Earth, in order to initiate fission to slow the vessel and to bend it's path as needed to achieve an Earth orbit suitable for docking with transport vessels.

Edit: I found a YouTube video of an interview with Dr. Dewar:
https://www.youtube.com/watch?v=u6f_iYbL-Zc

(th)

Last edited by tahanson43206 (2019-09-07 19:19:52)

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#39 2019-09-07 08:05:35

SpaceNut
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From: New Hampshire
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Posts: 17,333

Re: Large scale colonization ship

I see why not as we have the means to control the user accounts set up for that purpose.

Nuclear propulsion is something that for some say its a required element for Mars and farther out missions to more than the asteriod belt.

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#40 2019-09-07 09:03:23

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,754
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Re: Large scale colonization ship

I ran a quick little rocket-equation type bounding analysis for candidate approaches to a Mars colony ship design.  I included nuke explosion propulsion,  nuke thermal propulsion,  ion propulsion,  LOX-LH2 propulsion,  and storable chem propulsion.   The results point very clearly toward either nuke explosion or ion propulsion.

For those types of propulsion in the order listed,  Isp was 10,000 sec,  1000 sec,  3000 sec,  470 sec,  and 330 sec respectively.  Vehicle inert mass fractions were 0.50,  0.25,  0.10,  0.05,  and 0.05 respectively.  Inerts were rationalized as "heavy shocks and pusher plate",  "low thrust/weight solid core engine",  "mass of thruster array plus nuke or solar power supply",  "typical chemical stage",  and "typical chemical stage",  respectively.

All these were required to do the entire mission single stage.  The total orbital dV to and from Mars is 3.84+1.83+1.83+3.84 = 11.34 km/s.  Impulsive-burn options need supply only that with zero gravity and drag losses.  Long burn ion must supply a lot more than that due to very large planetary and solar gravity losses.

All but the ion option were considered as "impulsive burn" and Hohmann min energy transfer,  with vehicle acceleration exceeding 0.1 gee.  These used the sum of orbital dV's to and from Mars (orbit-to-orbit transport) as the mass ratio-effective dV for the rocket equation.  The ion option must spiral-out and spiral-in,  and accelerates to midpoint then decelerates to arrival.  Propulsion is sized for 0.001 gee.  To account for the planetary and solar gravity losses of months-of-burn,  I just doubled the orbital dV sum to 22.68 km/s.

All carried exactly the same 2000 metric tons of dead-head payload,  an arbitrary selection perhaps appropriate for a colony-type mission.  (I did not look at how to get that payload up to LEO,  or down from LMO,  that issue would be the same for all the candidates.)

Results:  nuke explosion 5100 metric tons at ignition with ignition/payload 2.56:1.  Nuke thermal 30,900 metric tons at ignition with 15.5:1 ignition/payload.  Ion 5500 metric tons at ignition with ignition/payload 2.76.  LOX-LH2 56,500 metric tons at ignition with ignition/payload 28.2.  Storable chemical utterly infeasible with a negative payload fraction available. 

The nuke explosion drive offers the lowest ignition/payload ratio at 2.56:1,  based on the old 1950's shaped-charge fission device technology.  This would be a very tough ship design,  probably usable for a century or more,  and likely tough enough to aerobrake,  reducing the load of bombs in favor of more payload.  Its hull and pusher plate are effective radiation shields.

The ion propulsion offers the next best ignition/payload ratio at 2.76:1,  which to be practical would require thrusters operating on something cheap,  plentiful,  and storable as a condensed phase like iodine.  This would be a relatively gossamer structure unable to survive aerobraking,  and it would likely also have a limited service life.  Radiation protection would have to be added. 

The others (nuke thermal and LOX-LH2) are nowhere close in ignition/payload ratio.  And storable chemicals are just infeasible in any sense of the word. 

I think you can look at the ignition/payload mass ratio to judge whether or not a given propulsion system might serve as a practical way to build a colony ship.  The same sort of analysis applies to other destinations.  You just need an appropriate list of orbit-to-orbit delta-vees,  and realistic guesses for inert fractions.

GW

Last edited by GW Johnson (2019-09-07 09:37:58)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#41 2019-09-07 10:38:52

tahanson43206
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Registered: 2018-04-27
Posts: 1,615

Re: Large scale colonization ship

For GW Johnson ...

Recalling your mantra to insure as little delay as possible between theory lecture and lab session in (EducationDoneRight), I'd like to ask for a test of comprehension by forum members ...

I am confident that at least three regular contributors have what it would take to arrive at the results you presented, if the challenge were broken down into subsets.

What I have in mind is (if you are willing) to set up an exercise for completion in (for example, a week) a period of time.  You could set the problem, and then provide hints for those who need them, but they would be visible to all, and therefore a lasting tutorial on that particular subset.

(th)

GW Johnson wrote:

I ran a quick little rocket-equation type bounding analysis for candidate approaches to a Mars colony ship design.  I included nuke explosion propulsion,  nuke thermal propulsion,  ion propulsion,  LOX-LH2 propulsion,  and storable chem propulsion.   The results point very clearly toward either nuke explosion or ion propulsion.

For those types of propulsion in the order listed,  Isp was 10,000 sec,  1000 sec,  3000 sec,  470 sec,  and 330 sec respectively.  Vehicle inert mass fractions were 0.50,  0.25,  0.10,  0.05,  and 0.05 respectively.  Inerts were rationalized as "heavy shocks and pusher plate",  "low thrust/weight solid core engine",  "mass of thruster array plus nuke or solar power supply",  "typical chemical stage",  and "typical chemical stage",  respectively.
<snip>
GW

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#42 2019-09-07 10:44:15

tahanson43206
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Posts: 1,615

Re: Large scale colonization ship

For RobertDyck on the topic in general ...

Navigation (or astrogation for purists) will be a significant challenge for any vehicles transiting between Mars and Earth.

Clearly there are people on Earth right now capable of the job.  What I would like to see is a set of posts on the navigation problem, hosted by existing experts in the field who are willing to subject themselves to the range of people who subscribe to this forum.

This would be a marathon rather than a sprint, and the new students would continue to arrive, so the series could be structured for new students to review earlier posts in order to master preliminary material.

(th)

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#43 2019-09-07 11:13:08

GW Johnson
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From: McGregor, Texas USA
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Posts: 3,754
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Re: Large scale colonization ship

Easiest thing for me to do is just send that spreadsheet to anybody who wants it.  You can put your own assumed numbers in,  and see the sensitivity of the results to them.  All the inputs are highlighted yellow.  Everything else is automatic.  It only models a single stage item doing all the burns from its propellant supply;  burns are Earth orbit departure,  Mars orbit arrival,  Mars orbit departure,  and Earth orbit arrival.  For low thrust propulsion,  you must factor these way up for long-burn gravity losses;  everybody else gets to use factor = 1.

mass ratio-effective dV = (factor for gravity & drag losses) x (orbital dV)  I used factor = 1 for all but ion,  I used factor = 2 for ion

mass ratio MR = exp(eff dV/Vex) where Vex, km/s = 9.8067*(Isp, sec)/1000

propellant mass fraction = 1 - 1/MR

inert mass fraction is an input (must justify appropriate values)

payload mass fraction = 1 - inert fraction - propellant fraction (only feasible if solid;  stop if negative)

payload is an input (doesn't really matter,  but 1000's of tons for any sort of realistic colonization mission)

ignition mass = payload / payload fraction

inert = ignition x inert fraction

propellant = ignition x propellant fraction

do the ignition / payload mass ratio;  you can scale any size from that ratio and any payload you want to deliver.

How much simpler can it be?

GW

Last edited by GW Johnson (2019-09-07 11:16:15)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#44 2019-09-07 13:03:52

RobertDyck
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From: Winnipeg, Canada
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Re: Large scale colonization ship

In the initial post, I calculated 66.85 metres of circumference for everything other than cabins, with ring width 19 metres. That provides 1,270.15 square metres =  13,671.78 square feet. Rule of thumb for restaurant seating is 18-20 square feet for fine dining, 15-18 sq.ft. for full service restaurant, 12-15 sq.ft. for commercial cafeteria, 10-11 sq.ft. for school lunch room, fast food or banquet room. I said 162 economy class cabins with 6 bunks, and 90 cabins with a queen-size bed. Captain would have a "single" cabin to him/herself, so full accommodation would be 1,151 not including premium and luxury cabins. Dining facilities could be sized for 1/3 at a time. No separate common room, instead use the dining room for games and other "common" facilities when meals aren't served. This could be broken up, say 2 large rooms with lunch room space to seat 100 at a time per room. Four themed diners for 50 people each. And for premium/luxury passengers, a fine dining restaurant that can accommodate 20 people. If seating is 10 sq.ft. per person, 15 sq.ft. for fine dining, that's 4,300 square feet.

Reference: Restaurant Layout & Restaurant Table Sizing: A Simple Guide to Knowing Which Tables Tops are Right for Your Restaurant

Is that enough? I notice commercial cruise ships serve meals in two shifts, so dining facilities accommodate half passengers at a time, not 1/3.

Add kitchen, laundry, gym, medical, bridge. Wouldn't require a library, we all have laptop/tablet/smart-phones; the ship would have Wifi and a server equipped with digital version of books, digital music, digital movies. Every cabin would have a large flat-screen TV. The hub of rotation would be zero-G arrival dock for the shuttle to carry passengers to/from the ship. During transit this could be a zero-G play area. The zero-G hub would have large windows facing forward. the hub would have elevators for "spokes" leading to the ring. Would also want at least one ladder in case of power failure. Again, I said zero-G storage for cargo aft of the hub.

The washroom for each cabin would have some life support equipment. A section of the washroom, full depth (30") and full height (floor to ceiling) say 1 foot depth would be life support equipment. A regenerable CO2 sorbent, and separate regenerable activated charcoal filter for smells. Rather than a flush toilet, I'm thinking urine collection tube like ISS. On ISS solid waste is collected with an air stream, what is basically a trash compactor compresses the waste into plastic bags with no air. Russia developed a vacuum desiccator toilet to recover moisture from feces, should we do that on the cruise ship. The ring will have full-time artificial gravity, but still has to recycle oxygen and water. Design the toilet to do the vacuum desiccation, dried waste carried by plumbing to life support for disposal. Urine processing also in the cabin washroom. A couple years ago I read about a British design student who designed a recycling shower. It uses a cyclonic filter similar to cyclonic vacuum cleaners, but for water. This separates skin oil, soap, shampoo, etc, from water. The separated water is put through a filter before going back to the shower head. This recycles 70% of the water, so reduces water consumption by 70% and energy to heat water by the same amount. That was intended for homes on Earth, but I'm thinking of cabins. Just don't urinate in the shower, the shower's filter is not designed for that. Um, you know what would happen. smile Could waste from the sink go through the shower's filter? So each washroom would have several plumbing lines back to life support: CO2, waste water, concentrated urine, dried feces. Supply would be O2, and potable water. Waste water would have combined result from the shower's filter, urine processing, and vacuum desiccation of feces. Life support would have to further process that to turn it into potable water.

Laundry could be a front-loading washing machine for reduced water consumption. And designed like an RV laundry machine, where the one drum acts as both washing machine and clothes dryer.

Does all this leave room for a club or bar/lounge? Lectures about Mars could be given in one of the dining rooms. Or a musician/entertainer.

Last edited by RobertDyck (2019-09-09 23:49:23)

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#45 2019-09-07 13:07:35

RobertDyck
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From: Winnipeg, Canada
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Posts: 5,858
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Re: Large scale colonization ship

I started this after the announcement from Elon Musk that Starship 2 would be twice the diameter of Starship, and passenger volume would be 8 times: 2 x 2 x 2. That means twice diameter and passenger module twice the length. My point is for a ship that size, you can do artificial gravity. And look what I'm doing: note quite cruise ship facilities, but getting close.

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#46 2019-09-07 14:56:26

SpaceNut
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From: New Hampshire
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Posts: 17,333

Re: Large scale colonization ship

Navigation is as GW put it all by equation, sensing and computing as there is very little close ship to ship where we would be docking. Sensing of position is done with stars and computing the angles for motion versus time.

The big diameter means we are spining as a spiral and not tumbling end over end for AG and that means the verticle wall is the floor once we are in motion.

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#47 2019-09-07 15:15:26

RobertDyck
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Re: Large scale colonization ship

Before we plug numbers into GW's equations, a couple questions. Do we recalculate for larger diameter and higher spin rate for 1G? Or stick with what I proposed for Mars level gravity? Is the size I proposed Ok? Do we use 6 month transit as Robert Zubrin proposed? That gives us a free return to Earth in case something goes wrong. Elon suggested faster transit, which means you better be able to slow once you reach Mars or you're heading out to the asteroid belt. Hull material? Do we use aluminum alloy like ISS? Or do we need a more durable material? GW can answer material durability. Remember, once this is spun up, it won't ever stop spinning. And once pressurized, it won't ever depressurize. There will be stress due to TMI and aerocapture, and for return TEI and aerocapture.

We could assume the same NTR engines as the 1990 version of NERVA. The 1974 version was built and tested in static engine test stands, it had Isp=825s in vacuum. The 1990 version had a number of technological improvements, Isp=925s in vacuum, but it was a design study with computer analysis and computer simulations only.

One technique is to orient the spacecraft so it's tail end to the Sun during transit. That would make the engine and propellant tank a radiation shield vs solar wind, although that would only protect zero-G cargo and the zero-G hub. It would mean the "side wall" of cabins would be toward the Sun, not the "floor". Or you could say the aft hull, not the ring outside hull. That would allow enhanced radiation shielding on that side.

How much radiation shielding do we need? 4" water wall? Shadow wall for radiation shelter? Or do we count on mini-magnetosphere?

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#48 2019-09-07 15:23:23

tahanson43206
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Registered: 2018-04-27
Posts: 1,615

Re: Large scale colonization ship

For SpaceNut ....

With a nod of appreciation to GW Johnson's generous spread sheet offer.

It seems to me likely that as the human race evolves into a space going culture, orbital mechanics will be included in the grade school curriculum the way trigonometry or algebra are included today.

The captain of the RobertDyck (or sister ships in the fleet) will be running software to keep track of position and vectors of the ship itself, Mars and the Earth, the Moons of Mars and Earth, and all the flotsam and jetsam moving around in the ship's path.

For a massive ship such as RobertDyck has proposed, there will be NO dodging and weaving to evade potential interference with its path.

The Earth Planetary Defense establishment will be VERY interested in the Captain's plans for aerobraking, and it would not surprise me at all to learn that the exact time of departure from Mars might be determined in consultation with the Earth Orbit management team.

We humans are in the process of developing a coordinated traffic control system for Near Earth Orbit.  The first serious signs I've seen are hints of authorization of a US Space Command.  The arrival of gigantic cruise ships carrying hundreds of passengers which must slow down by passing through the Earth's atmosphere will accelerate interest in developing coordinated management solutions.

Is there any where on the site that the spread sheet of propulsion options might be saved for access by interested members?

(th)

SpaceNut wrote:

Navigation is as GW put it all by equation, sensing and computing as there is very little close ship to ship where we would be docking. Sensing of position is done with stars and computing the angles for motion versus time.

The big diameter means we are spining as a spiral and not tumbling end over end for AG and that means the verticle wall is the floor once we are in motion.

Last edited by tahanson43206 (2019-09-07 15:23:46)

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#49 2019-09-07 16:07:19

RobertDyck
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From: Winnipeg, Canada
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Re: Large scale colonization ship

With enough power, we could get really fancy. In 1995 one researcher developed something called "plasma window". He was working on an electron beam welder. An electron only forms in vacuum, so the welding has to be done in a vacuum chamber. That's inconvenient. For the work piece to be outside the vacuum chamber, you need vacuum to generate the beam, but then a way for the beam to get out without destroying the chamber. In order to weld, the electron beam has to be intense enough to melt steel. So how do you get the beam out without punching a hole in the vacuum chamber? His solution was a plasma window. A 1" hole in the side of the vacuum chamber, but that hole would be filled with plasma. He found plasma at 12,000°K or hotter forms a thick viscous plasma that can hold out air pressure. It can withstand 1.5 atmospheres of pressure against hard vacuum. If the electron beam makes the plasma hot, that just makes the plasma stronger.

That solved his welding problem, but it gives as a new tool. This is a force field that can hold in air pressure. Star Trek TNG showed a force field to hold air pressure for a shuttle bay, so you didn't have to decompress. That has a number of problems. A thick viscous plasma at 12,000°K will melt any aluminum hull ship. It'll melt steel! And researchers have been using higher temperature, because if anything touches the plasma it'll cool. If it cools below the critical temperature of 12,000°K then it can't hold air pressure any more. So they've been using 14,000°K. Now imagine radiant heat coming off that; anyone standing near it would broil. So an emergency force field to seal a hull breach? Not going to work.

The reason I raise this is for protection. What if the ship's hull has a plasma window outside it's hull? A thick viscous plasma at high temperature forming a wall to protect the hull? If meteoroids hit, that would vaporize them. Mini-magnetosphere is more effective vs radiation because it uses a lot less power and extends kilometres from the ship. It can deflect GCR at such a distance that it'll go around the ship. Mini-magnetosphere works the same a Earth's magnetosphere. But plasma window would be a wall protecting the ship from impact. The catch is plasma window as designed in 1995 requires 20kW per inch diameter! Ouch! Is there a way to layer a lower temperature plasma over that to contain radiant heat, so it doesn't need as much power? And should we consider such leading edge technology?

This would literally be "shields".
Wikipedia: Plasma window

Science paper from Brookhaven National Laboratory:
Plasma Window Technology for Propagating Particle Beams and Radiation from Vacuum to Atmosphere

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#50 2019-09-08 19:01:19

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 5,858
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Re: Large scale colonization ship

Found a reference to commercial kitchen design. It says 5 square feet per seat in the dining room. I said above a total of 420 seats, so 2,100 square feet of kitchen? That leaves 7,274 square feet for laundry, gym, medical, bridge.

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