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#926 2021-11-23 14:14:15

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 23,913

Re: Large scale colonization ship

Collective thought on how to move to reality is a hard step when you along have not the funds to build.
That is the nature of a non-profit as what they are receiving can only go just so far.

How do we sell the assembly of the ship on orbit?
What are the number of starships or others required to do so?
What is the projected time to finish the large ship for use?
Is the large ship build like a home where the shell gets completed and other stuff is built to fit it delivered?

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#927 2021-11-23 15:55:44

RobertDyck
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From: Winnipeg, Canada
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Posts: 6,920
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Re: Large scale colonization ship

I could get bitter. If the same things happen, traditional contractors for NASA will kill any effort. We won't go to Mars. If Elon continues, he's headed in an odd direction. Starship is amazing, but Mars needs a lot more. If all he does is Starship, I'm afraid the first landing will look like this...
spacex-fail.gif

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#928 2021-11-23 18:55:50

RobertDyck
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From: Winnipeg, Canada
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Posts: 6,920
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Re: Large scale colonization ship

If anyone has access to investors, I have other business ideas. Profits from these other businesses can be used to start the space company to build the large ship.

  • develop gallium-indium-arsenide photovoltaic cells

  • Use said solar cells to build houses that are 100% energy independent in northern climates like mine. That includes Canada, North/South Dakota, Montana, Minnesota, etc.

  • Install solar/wind/geothermal system in commercial buildings with a large roof.

  • Manufacture/sell kits to convert used cars to battery electric. One option could be hydrogen fuel cell; that just adds a fuel cell and hydrogen storage tank. Target for vehicles used as host cars for body kits. Customers already are willing to install a kit into such vehicles.

  • Hearing aid using direct nerve induction. This can be worn with electrodes taped to skin, no surgery. Advantage over cochlear implant is no surgery.

  • Thermal depolymerization facility to reduce recycled plastic into oil & natural gas. Same building will use that oil and natural gas to produce plastic. Sell bulk plastic as nurdles.

  • Recycle glass into glass bottles. Last I checked the glass from blue box recycling programs convert the glass into beads for reflective paint on road signs, or bury the glass under roads. That's not recycling. Recycling means glass bottles become glass bottles. Would require partnering with a major customer who needs those bottles.

I could work with a company that produces pea starch. If they're willing to fund research, develop a genetically modified pea that uses genes from cyanobacteria to recycle waste product from oxidation of RuBP. This would require working with a biotech company that can genetically modify a plant. The goal is to reduce photorespiration, which should increase crop yield. The funder would get a cultivar that produces higher yield for their use. Of course my objective is to produce a pea that produces chloroplasts suitable for the chloroplast oxygen generator for life support.

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#929 2021-11-23 19:39:51

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 23,913

Re: Large scale colonization ship

Looks like a jump start business is in order to get into those others.

What about a program app for google play store that displays ads for a penny a look buried inside of something people might use?

Create your app

    Open Play Console.
    Select All apps > Create app.
    Select a default language and add the name of your app as you want it to appear on Google Play. ...
    Specify whether your application is an app or a game. ...
    Specify whether your application is free or paid.

More items...

https://support.google.com/googleplay/a … 9152?hl=en

How about wifi internet expansion extender connection for a fee to get access to the web ion you local area

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#930 2021-11-24 20:34:29

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 6,920
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Re: Large scale colonization ship

Business manufacturing aluminum oxynitride windows, sized for storefront windows. I'm sure areas prone to riots would like this, jewellery stores, etc. Smaller panes sized for jewellery display cases. Not just profitable, but develops the technology to manufacture windows for the large ship. Obviously not a new technology, but sets up a company able to make them.

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#931 2021-11-29 09:34:33

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,701
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Re: Large scale colonization ship

Robert:

Take a look at one of my "exrocketman" blog articles:  "On High-Speed Aerodynamics and Heat Transfer",  dated 2 January 2020,  in particular the discussions about lateral wake zone heating near Figure 5 in that article.  That will explain the concern I raised about survival of your solar panels and mirrors during aerobraking.

The heat shield fabric material is a distinct issue.  The aluminosilicates all share a solid phase change temperature in the vicinity of 2350 F,  that causes about 3% shrinkage and extreme embrittlement.  This is far below the nominal meltpoint near 3300 F.  Doesn't matter whether a flake or fiber consolidated into a tile,  or a fiber spun and woven into a fabric.  It's a property of the basic material. 

Left white,  these are also very NON-gray emitters of fairly low average efficiency.  They have to be coated black in some way to emit efficiently.  You simply cannot reuse them if they get hot enough to hit the phase change point. Doesn't matter what the form is,  it's a property of the basic minerals.

There was a paper that I presented at one of the Mars Society conventions about using these materials as heat shields.  To be used on the windward side,  they have to be coated black.  To be used at the stagnation point,  your ballistic coefficient has to be very low,  and your nose radius of curvature very,  very large. 

It'll work to about 8 or maybe 9 km/s ,  but faster than that,  the plasma sheath starts getting opaque,  preventing effective re-radiation cooling. At about 10 km/s,  plasma radiation heating begins to exceed the convective heating.  It dominates the heating by far,  at about 11 km/s. Convective is proportional to velocity cubed.  Radiational heating is proportional to velocity to the 6th power.

GW

Last edited by GW Johnson (2021-11-29 09:36:00)


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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#932 2021-11-29 11:02:55

Calliban
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From: Northern England, UK
Registered: 2019-08-18
Posts: 1,338

Re: Large scale colonization ship

One thing that I realised when trying to model deceleration of ballistic projectiles using a spreadsheet program: aerobraking only works for relatively small spacecraft.  As the size of the body increases, it must dip deeper into the atmosphere to achieve enough force per unit area to shed meaningful velocity.  You reach a point where the force acting on the aeroshield is extreme and the heating becomes unmanageable.

I also wondered (I have no way of modelling this) about differential pressure across the shield.  As the shield gets larger, the effect of density variations in the atmosphere across its surface becomes more pronounced.  This could cause the centre of pressure to wander during the maneuver.  I don't know if there is a way of compensating for that?

It would be interesting to explore the use of sacrificial liquids as a means of reducing plasma heating.  Water might be best because huge amounts of energy are absorbed breaking the O-H bond as it dissociated.  This should provide a way of holding down plasma temperature and convectively cooling the shield.  It would also provide an element of thrust as the dissociation products form plasma ahead of the shield.  Propellant use could be very efficient as we are talking about small amounts of water cooling the plasma through dissociation.  Something to think about.

Last edited by Calliban (2021-11-29 11:05:41)


"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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#933 2021-11-29 13:58:02

RobertDyck
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Re: Large scale colonization ship

GW Johnson:
3M: Nextel 440

Multi-strand twisted yarn made from 3M™ Nextel™ 440 continuous ceramic oxide fiber
...
Melting point 3272°F (1800°C)

3M: 3M™ Nextel™ Ceramic Fibers and Textiles Technical Reference Guide

3M™ Nextel™ Ceramic Fibers are refractory aluminoborosilicate (312 and 440)...

NASA Technical Report Server: Reusable Launch Vehicle: Technology Development and Test Program

Nextel AFRSI—Advanced fibrous refractory surface insulation is made from Nextel 440 fabric and alumina batting and can withstand temperatures of about 2,000°F.
...
DurAFRSI—AFRSI is modified by adding metallic foil brazed to the wire mesh top surface to create DurAFRSI, which makes the material more robust.

Note: this is not for atmospheric entry, only for aerocapture and aerobraking. The goal is to reduce heat load to what the thermal protection system can handle. Mars Global Surveyor used propulsion for orbital capture, but aerobraking to drop to mapping orbit. It just used solar panels for aerobraking, so very gentle deceleration and heat load. The references cited above confirm your figures, but again the point is not atmospheric entry, it's simply aerocapture.

Also note: both Nextel AFRSI and DurAFRSI described above is a quilt with alumina batting. To be precise it's Saffil batting which is 96% aluminia/4% silica. Saffil is high-purity polycrystalline fibers designed for use in applications up to 1600°C (2912°F). However, the heat shield I proposed for aerocapture would be just Nextel 440 fabric.

In Post #535 I cited posts made earlier calculating aerocapture. Result is 2.91361 m/s² over 872.801 seconds (14 minutes, 32.801 seconds). How much heating will that cause? Will it exceed limits of this material?

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#934 2021-11-29 14:09:42

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

Calliban,
One researcher working for NASA developed ADEPT in the 1980s. That is a carbon fibre fabric heat shield that opens like an umbrella. It increases surface area to resolve the cube-square problem. It reduced ballistic coefficient by increasing surface area. That ensures it doesn't have to dip any deeper into the atmosphere than smaller aeroshells like those used for Mars Exploration Rovers (Spirit & Opportunity) or Mars Science Laboratory (Curiosity rover). ADEPT was designed for a standard payload of 40 metric tonnes landed weight. Mars Direct habitat was 25.2 metric tonnes, and Mars Direct ERV 28.6 metric tonnes, taken from "The Case for Mars" first edition 1997, paperback, page 93. Mars Direct was designed in 1990 and one feature was to use ADEPT for atmospheric entry. My proposal is to use Nextel 440 instead of carbon fibre, although carbon fibre can withstand greater temperature it becomes hardened and embrittled after thermal cycling. So my goal is to keep heating below the temperature that GW Johnson said will cause phase change and embrittlement.

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#935 2021-11-29 22:20:34

GW Johnson
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From: McGregor, Texas USA
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Posts: 4,701
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Re: Large scale colonization ship

Rob:

I checked on the construction of Apollo vs Mercury & Gemini.  The two LEO entry designs had ablative heat shields and Rene-41 metal after-shells.  Apollo had an aluminum honeycomb sandwich pressure shell,  within a stainless steel honeycomb sandwich "heat shield" shell.  Another phenolic honeycomb was bonded to the outer surface of the stainless steel shell,  with Avcoat of reduced density (31 pcf) injected into each cell of that honeycomb with a heated caulk gun,  hexagonal cell by hexagonal cell.  The outer coating was an aluminum foil. This heat shield was 2 to 3 inches thick on the blunt end of the capsule,  and 0.7 to 1.3 inches thick on the conical after-shell.  It is said that the heating rates on Apollo were some 4 times higher than those seen on Mercury or Gemini. 

What you have going with an aerobrake at Mars is an entry speed of 7.5 km/s,  versus 7.9 from LEO on Earth.  Those are quite comparable.  The heating rates should be comparable to LEO entry capsules,  all else being equal,  which it is not.  Because of geometry and density differences,  as well as speed differences,  along the two different trajectories.  You could probably have bare metal structures exposed to the wake gases,  if they are as tough thermally as Rene-41.  Those gases will be somewhere near 7500 K effective temperature,  falling as you decelerate. 

Stagnation convective heating is proportional to ambient density^0.5,  inversely proportional to nose radius ^0.5,  and proportional to velocity^3.0.  At only 7.5 km/s entry speed,  you need not worry about plasma sheath radiation heating,  and that plasma sheath is transparent to re-radiated infrared.  It is about 10 km/s where the radiation heating surpasses the convective,  and the plasma sheath starts becoming opaque to re-radiated infrared.  Stagnation heating is the worst case location.  Along the sides with attached supersonic flow prior to wake separation,  heating rates are about half an order of magnitude lower.  It takes experimental data to refine those estimates for any shapes not yet tested and correlated.  Downstream in the separated wake zone,  heating rates are about a order of magnitude lower than stagnation.  All three locations share the same driving temperature,  just different effective heat transfer coefficients.

In order to get your intended deceleration levels for capture,  in the thin Martian atmosphere,  during one single pass,  my guess or hunch is that your aerobrake pass will be within 30-or-so km of the surface.  That raises heating rates by the density^0.5 effect.  This is quite distinct from the probe that aerobraked with its solar panels.  Mars has a thin atmosphere:  you must dive deep to get any deceleration gees.  That also means more heating,  because of the higher densities that deep.

Whatever the heating rates are,  they have to be balanced by infrared re-radiation from the exposed part,  there is little if any opportunity for conduction into the interior.  Its material temperature equilibriates where the re-radiation per unit surface area matches the convective heating per unit surface area.  Generally speaking,  that happens in the 1000 F to 1200 F range at these speeds,  but only if the material behaves as a gray body at high average spectral emissivity (0.8 or higher).  Low emissivity drives equilibrium temperature up substantially.

The very same heating correlation applies to your fabric heat shield.  Since it does not ablate,  its only cooling mechanism is re-radiation of infrared.  Its temperature has to equilibriate the same way I already described.  It will see a worst-case stagnation point heating rate,  and about half an order of magnitude lower heating rate at its periphery.   You cannot rely on conduction to cool the stagnation point by conducting heat toward the periphery,  and your design concept precludes heat conduction into the ship interior for heat-sinking there.   Especially because the material is a non-gray white (emissivity ~ 0.2 or lower),  it will equilibriate at a very high temperature indeed.

All of this depends very sensitively upon the exact history of velocity and ambient density during the aerobrake pass.  The same is true for deceleration gees.

GW

Last edited by GW Johnson (2021-11-29 22:35:04)


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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#936 2021-11-29 23:13:44

RobertDyck
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From: Winnipeg, Canada
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Posts: 6,920
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Re: Large scale colonization ship

Yes, that description of Apollo and Gemini/Mercury is what I read too. The difference is milder deceleration, so you don't need to dive into thick atmosphere. Apollo angled the capsule during reentry to provide lift. It wasn't much, but pure ballistic would have been 8-9 g deceleration. With lift it was 4-5 g deceleration. Reducing g load also reduced peak heating. (reference: Wikipedia) I'm talking about 2.91361 m/s² = 0.2971 g deceleration. A good portion of reentry heating is gas compression of the shock wave. Lower deceleration, less compression of the shock wave. And covering the entire ring with a disk of fabric heat shield spreads out the force and consequently the heating.

Ok, we have to study this. I already suggested the hull made of stainless steel. Stagnant air behind the heat shield will be an issue; the photovoltaic panels will have to be protected.

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#937 2021-11-30 13:14:25

GW Johnson
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From: McGregor, Texas USA
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Posts: 4,701
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Re: Large scale colonization ship

The effective temperature of the gas behind the shock wave depends upon the speed,  not the deceleration.  7.5 km/s is roughly 7500 K gas,  no matter how many or few gees of deceleration you experience.  Gees are set by your speed and by the ambient density.  For typical Mars entry at higher ballistic coefficients,  I'm showing about a peak 2-4 gee deceleration at somewhere near 30-40 km altitudes. 

That's not the same flight path at all as aerobraking,  but the profile with time is similar.  There is vanishingly-small deceleration and heating at entry interface altitudes and for some significant time later diving deeper.  That is about 135 km altitude on Mars. The pulses of high deceleration gees and heating (not simultaneous,  but close) occurs late in the trajectory on Mars because the air is so thin even at low altitudes.  After the pulses of deceleration and heating,  velocity is much lower (under half orbit speed),  and deceleration drops to low fractions of a gee again,  now governed by supersonic aerodynamics and weight.

That's for entry.  Aerobrake capture in one pass is different,  but not as different as most might think.  You are moving about 7.5 km/s wrt Mars at entry interface.  Circular orbit is 3.5 km/s,  and you better not be much faster than than 4.5 km/s if you want a stable orbit with a period not too long.  5 km/s is Mars escape.  Which means your delta-vee you need from the aerobrake pass is 3 to 4 km/s.  And that's a big delta-vee requirement!.  Most of it comes in the peak deceleration pulse which is only 10's of seconds long,  not minutes long.  Your peak gees and heating are going to at least loosely resemble those in entry.  And until the pulse slows you down,  your velocity will be in the 7.5 to 6.5 km/s range,  corresponding to hot gas exposures at 7500 to 6500 K.  The second half of your pass,  your velocity is around 3 to 4 km/s,  corresponding to hot gases at around 3000 to 4000 K.

In other words,  your peak gees will be nearer 2 gees than 0.3 gees,  although it may average near 0.3 gees.  And you are exposed for several minutes to hot gases in the 3000-7000 K range. 

Take your Earth(!!!) weight of your spacecraft,  double that for 2 gees,  and that's your peak deceleration force.  Divide that by your craft's total blockage area,  and that's the average pressure exerted on its windward surfaces.  Double that,  and you have a crude estimate of the peak windward side pressure felt at or near stagnation zones.

Your velocity at entry interface is low enough that you need not worry about radiant heating from the plasma sheath,  and you will be able to re-radiate heat to space back through that sheath.  Use the old warhead correlation for stagnation heating rate,  which is the max,  at the stagnation point.  Figure the heat rate per unit area there in your deceleration pulse at about 4 or 5 km/s,  and around 40 km altitude on Mars.  Figure it for your heat shield radius of curvature as your "nose radius".  Then figure your re-radiation rate per unit area vs assumed material temperature and some realistic emissivity.  If left white,  use e = 0.2;  if coated black,  use e = 0.8.  Where the two heat rates per unit area equal,  is the equilibrium material temperature at the stagnation point,  which is the max. 

If that is over 2350 F,  you cannot expect to use your aluminosilicate heat shield but once.  If it is lower,  it is reusable many times.  Simple as that.  And just as stark.

GW

update 11-30-21 2:25 PM CST

The old warhead stagnation heating correlation,  updated to metric units,  is convective q/A, W/cm^2 = 1.75 E-8 (rho/Rn)^.5 (1000 V)^3 where rho is ambient density,  kg/m^3,  Rn is "nose radius", m,  and V is flight velocity km/s.  Note that the result is W/sq.cm,  NOT the more usual W/sq.m.  Entry heating rates are just high,  no way around that.

Last edited by GW Johnson (2021-11-30 14:33:19)


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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#938 2021-11-30 16:20:16

RobertDyck
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Re: Large scale colonization ship

Apollo was able to "fly" so they reduced peak acceleration from 8-9 go down to 4-5 g. The aeroshell for Curiosity rover used the same technique. This reduced peak acceleration, while increasing time that acceleration was applied. We can definitely do the same during aerocapture. With an average deceleration of 0.2971 g over 14½ minutes, yes you can maintain a flat deceleration profile for most of that time. Which means peak deceleration will be very close to 0.3 g, not 2 g. I'm not arguing to make the structure flimsy, the point is to reduce heating during aerocapture.

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#939 2021-11-30 17:03:26

GW Johnson
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Re: Large scale colonization ship

Apollo was 4-5 gee coming back from LEO.  It was 10-11 gees coming back from the moon. 

I do not have the necessary tools to look at a real aerocapture pass.  But for entry,  you do not have a choice:  there comes a point where you get a short pulse of deceleration that is way larger than your average deceleration.  You get a heating pulse also,  close to,  but not simultaneous with,  the deceleration pulse.  They are set by your speed at entry interface,  your ballistic coefficient,  and your entry angle below local horizontal.  Higher ballistic coefficient and higher speed both delay the pulses to later and deeper,  which makes them very much stronger.  Steeper angle does the same thing. 

Considering that for a capsule shape L/D is usually near 0.01,  with 0.1 as an utter maximum,  L/D doesn't really affect the deceleration pulses so much as it affects your downrange and cross range touchdown locations. 

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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#940 2021-11-30 23:15:32

RobertDyck
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Re: Large scale colonization ship

Setting up a spreadsheet to estimate mass. So we have hard figures to work with. I'm already at 1,000 metric tonnes and a lot of things haven't been added yet.

Here is a record of Apollo 11 directly from NASA: Day 9: Re-entry and Splashdown

[This is the final Entry PAD. It is interpreted as follows:

    Purpose: Entry.

    Landing target: The landing target is in the Mid-Pacific.

    IMU gimbal angles required for trim at 0.05g: Roll, 0°; pitch, 150°; yaw, 1°.

    Time of the horizon check: 194 hours, 46 minutes, 6 seconds GET.

    Spacecraft pitch at horizon check: 267°. This is 17 minutes before time of entry.

    Splashdown point (Noun 61): 13.32° north latitude, 169.17° west longitude.

    Maximum number of g's during entry: 6.4.

    Velocity at Entry Interface (400,000 feet altitude, Noun 60): 36,194 feet/second (11,032 metres/second).

    Entry flight path angle at Entry Interface: 6.49°.

    Range to go to splashdown point from 0.05g event: 1,404.5 nautical miles (2,601.1 km).

    Predicted inertial velocity at 0.05g event: 36,275 feet/second (11,057 metres/second).

    Time of Entry Interface: 195 hours, 3 minutes, 6 seconds GET.

    Time from Entry Interface to 0.05g event: 0:28 (seconds).

    The next four items relate to the g-forces and velocities that pertain to the skip-out maneuver that this entry will perform.

    Maximum drag level at skip-out maneuver (Noun 69): 1.54g

    Minimum drag level at skip-out maneuver (Noun 69): 0.84g

    Maximum skip-out velocity: 22,400 feet/second (~6,800 metres/second)

    Minimum skip-out velocity: 18,000 feet/second (~5,500 metres/second)

    Planned drag level (deceleration) during the constant g phase: 4.00g.

    Time from Entry Interface until their velocity slows sufficiently to allow a circular orbit around the Earth: 2:13.

    The practical implication of this is that this is the "capture point" where the CM cannot exit on an orbit around Earth. It is bound to reach the surface on this pass.

    Time from Entry Interface that the communications blackout begins: 0:17.

    Time from Entry Interface that the communications blackout ends: 3:51.

    Time from Entry Interface that the drogue parachutes will deploy: 9:02.

    Sextant star: 45 (Fomalhaut, Alpha Piscis Austrini.)

    Sextant shaft angle at Entry Interface minus 2 minutes: 18.9°.

    Sextant trunnion angle at Entry Interface minus 2 minutes: 27.7°.

    The crew will not make an additional attitude check made using the COAS sighted on a star so the next three items are not applicable.

    Lift vector at Entry Interface: Up.

    Comments in addition to the PAD:

    If the IMU fails and they need to have a backup alignment on the Gyro Display Couplers, then they should use stars Vega and Deneb. Aligning to them would represent the following attitude; roll, 078; pitch, 223; yaw, 340. Although they are extending the length of the entry by invoking the skip-out software, they will not be exiting the atmosphere so therefore they should use the part of the EMS scroll that pertains to a non-exit entry. When making a check of the horizon angle 30 minutes prior to Entry Interface, their pitch angle should be 298°. In a conventional entry, P64 is followed by P67. For a skip-out re-entry, P65 and 66 are employed to handle the exit and entry parts of the skip. In this case, because they are extending the re-entry but not actually skipping out, P66 will not be invoked and instead, P65 will lead directly to P67. The crew are also informed that they may not be in a full-lift (heads-down) attitude when they enter P67.]

Key lines from this are:
    Maximum number of g's during entry: 6.4.
    Planned drag level (deceleration) during the constant g phase: 4.00g.

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#941 2021-12-01 01:54:53

RobertDyck
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From: Winnipeg, Canada
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Posts: 6,920
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Re: Large scale colonization ship

Mars Climate Orbiter was intended to use it's solar panels for aerobraking.
mars98orb.gif

Mars Global Surveyor used thrusters to enter orbit, then used solar panels for aerobraking to drop into mapping orbit.
mars_global_surveyor.gif

Mars Odyssey also used aerobraking to enter mapping orbit.
mars_2001_odyssey.gif

And Mars Reconnaissance Orbiter
mars_recon_orbiter.gif

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#942 2021-12-01 17:20:21

GW Johnson
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From: McGregor, Texas USA
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Posts: 4,701
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Re: Large scale colonization ship

Rob:

I may be wrong,  but I think all those probes did low delta-vees (well under 1 km/s) in any one pass.  That can be done at very high altitudes in the thinnest air where drag and heating are low.  You need a high delta-vee (around 3 to 4 km/s),  and it must happen in one pass to effect capture.  That has to be done deeper down,  at higher densities,  where both drag and heating are much higher.  This question will take a real aerobraking code to answer.  I do NOT have one.

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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#943 2021-12-01 18:43:19

tahanson43206
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Posts: 8,112

Re: Large scale colonization ship

For RobertDyck ... GW Johnson asked about the mass of Large Ship ... if I recall correctly, you recently published a first guess about the mass.

If so, please post that figure again so he can iind it.  He's expressed interest in working on planning for the boost you'll need to put Large Ship at Mars using a Hohmann Transfer (if you are OK with that travel time). 

Our reasoning is that the Large Ship provides gravity, radiation protection, and "comfortable" living (compared to alternatives) so 8 months might be acceptable for passengers and crew.

(th)

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#944 2021-12-01 22:02:00

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

GW:

Yes, you're right, those orbiters did low delta-vees in any one pass. This ship will require 0.3 g for 14½ minutes for aerocapture. It could aerobrake to drop orbit further before off-loading. Yes, that means dipping deeper into the atmosphere. However, my point is it doesn't require the 4.0 g deceleration of Apollo, so I expect far less heating.

I'm hoping this will work! I suggested the propulsion stage is attached such that it can be replaced. So the first trip could use a LOX/LCH4 propulsion stage using all Raptor engine. The propulsion stage could be launched by SpaceX Super Heavy booster. The propulsion stage would replace Starship. It would use all vacuum optimized Raptors, no sea level Raptors because it would never land on Earth. It could be slightly longer/higher, with straight cylinder top with tank dome like Super Heavy. An expendable fairing for launch.

Some time later the propulsion stage could be replaced with one that uses Direct Fusion Drive by Princeton Satellite Systems. But that's only when said engines become available. Fusion Engines should provide enough thrust and specific impulse to make propulsive orbital insertion practical.

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#945 2021-12-01 23:41:37

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 6,920
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Re: Large scale colonization ship

I'm working on a spreadsheet to estimate mass of the ship. Not ready yet.

Missing mass for:
Gym, Dining rooms, Kitchens, Bar, Laundry, Infirmary, Bridge, Brig
completely missing upper deck: observation galleries/rooms, Mars simulation room, greenhouses, hydroponics & aquaculture, advanced life support (microbe tanks)
RCS thrusters/tanks/propellant
mid-course correction engines/tanks/propellant
main propulsion propellant (engines & tanks are included in estimate)
radiators, air conditioning equipment, solar panels, batteries
plumbing pipes, electrical wiring
food

Assumptions:
66 crew + 1000 passengers, average body weight for North American adult, 50% male / 50% female
all passengers and crew bring 23kg (50lb) luggage per person, stored in cabin
all passengers (but not crew) bring 46kg (100lb) cargo per person, stored in hold

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#946 2021-12-02 15:41:56

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 6,920
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Re: Large scale colonization ship

Sent a message to a friend who's a professional chef. He used to be head chef for a chain of restaurants. One task was to evaluate potential restaurant managers. After corporate had selected candidates according to management skills, then sent the candidates to my friend to see if they could manage a kitchen. What he told me makes the TV show "Hell's Kitchen" sound mild. He had candidates run out crying. His plan was to retire at age 30. He founded the local comic con, although that now has serious competition. And founded a comic book store. But he still does catering. I asked him to help design the ship's kitchen and dining rooms.

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#947 2021-12-02 17:14:07

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,701
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Re: Large scale colonization ship

Well,  I'm just glad to see progress toward this large colonization ship design. 

I did some estimates a while back for using Starship single stage from Mars to Mars LEO and back to Mars,  as a sort of "lighter" for unloading or loading craft in low Mars orbit.  Such looked feasible at nice large payload figures.  These could be transports for people and cargo,  or they could be refueling tankers.  I posted this on "exrocketman" a couple of years ago,  but I don't remember the date or the title. 

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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#948 2021-12-03 01:18:21

kbd512
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Registered: 2015-01-02
Posts: 4,924

Re: Large scale colonization ship

Robert,

That thing won't weigh anywhere near 1,000t if it's carrying 1,000 people.  10,000t without propellant is a lot more realistic.  The Ticonderoga class guided missile cruiser weighs 9,800t at full load and has a complement of around 350.  If you ripped out all of the combat systems and the machinery in the main spaces, then you might have sufficient space to accommodate 1,000 people.

I don't care what kind of Iron or Nickel-Iron or Titanium alloy you're working with, when going beyond 800C it's tensile strength will closely resemble the glide path of a brick.  By 1,000C, it's tensile strength is 1/5th to 1/10th of what it was at room temperature.  I'm unaware of any alloy or super alloy that performs substantially better.  Some can withstand higher temperatures than others before they melt, but long before they melt they have near-zero strength left.

This is only somewhat related, but a good source of info with actual test results on various families of alloys suitable for use at cryogenic temperatures:

A Review on Steels for Cryogenic Applications

This paper talks about both cryogenic and high temperature properties of various stainless and maraging steel parts that were made using additive manufacturing:

Effect of Cryogenic Grinding on Fatigue Life of Additively Manufactured Maraging Steel

More advertising than info, but still basic info on general uses for Nickel-Iron alloys (the author is someone who helps end users select steels suitable for their applications, so he might be willing to help us):

Strong, hard and tough: the many ways nickel-containing alloy steels deliver

I only bring this up because you're expecting these structures to survive over a huge range of operating temperatures and transients.  Given the considerably higher yield strength and toughness of maraging steels, as compared to stainless steels, within the anticipated -250F/+250F environment of space, along with excellent formability and weldability, we may need to spec-out a maraging steel to use for the primary structure.  These steels are generally expensive, but widely used in ship and aircraft construction.  These alloys are also used for LNG tanks.  A true stainless would be far more suitable for storing LOX.  I'm looking at ways of economizing on steel usage, given how heavy these things will be.

BTW, I don't see us using many COTS items for berthing, furniture, and whatnot inside this ship.

For example, there will be no free-weights in the gym, because they could become projectiles and rubber bands can provide equivalent resistance for exercising with or without gravity, for far less total weight.

The steel coffin racks used by the Navy are way too heavy for this application.  Each one weighs about 150lbs, so 68t for 1,000 people.  That weight does not include the steel supports to stack them three high, either.  IIRC, a complete 3 rack set was around 600lbs or thereabouts.  The Aluminum tubing frame camping cots are around 5lbs or so.  Add in supports to cantilever that cot off the walls of a berthing compartment, and it's still 10lbs or less.  We used hammocks aboard ships during WWII, so a cot is a big step up from that.  You sleep under a wool blanket of around 4lbs.  Whenever possible, the berthing compartments were deliberately kept cold to slow the spread of disease, thus the need for a blanket.  A complete Sea Bag weighs about 45lbs.  If you replace the various jackets / coats / dress uniforms with working uniforms / light jacket / blanket, then the bag could hold all of your personal items.  Removing steel toe boots would save quite a bit of weight, as those were around 5lbs per pair.  I'm not sure what cargo you would take to Mars, as I would imagine that everything to support your life there also has to be made there.  I would say everyone is strictly limited to a single Sea Bag.  Cargo freighters will take cargo.  This is a purpose-built passenger carrying vessel.

The cot can fold down to make space in the berthing compartment for activities like exercise, playing cards, and watching movies.  We primarily exercised, played cards, told sea stories, and watched movies with each other for entertainment.  Maybe video games would be more popular now that you can play online.  For example, I had a guy I normally went to the gym with, guys and gals I normally ate lunch with, and guys I did training with that I also hung out with (guys from my watch, primarily).  It's rare to see anyone outside of their group, mostly because you work together and have the same schedule.  Wrestling was also popular, which we routinely got in trouble for when (not if) people were hurt- basically, don't let a senior officer or a chief see you do it.  That pretty much covers entertainment for 6 to 8 months.  You also have to spend time studying, because testing never ends.

US Navy Sea Bags are made from a tough nylon material and can be locked using a pad lock.  These bags could be made from Kevlar or Spectra fabric, if required, to reduce weight and increase abrasion and cut resistance (deter theft).  That said, I could leave a roll of cash on my rack and it would still be there when I returned, but if you left a cover (command ball cap) on your rack then it would sprout legs and probably never return of its own accord (they're required for uniform inspections, but most of them weren't embroidered with your name and rank, because that was expensive).  Money is nearly useless aboard a ship, but inspections are routine and required.  Inspection is how the command verifies that all required uniform items are maintained by each crew member or passenger.  Uniforms have to be repaired by the ship's tailor (normally a Store Keeper's mate, but anyone with industrial / commercial sewing experience will do) or replaced if they're damaged or destroyed.

The "chairs" in the galley will be plastic bar stools bolted to the deck.  Loose furniture is a liability.  Maybe the officers or wealthy passengers could have a chair tethered to the deck, but allowing lots of large / heavy loose objects is only screwing yourself over.  We had roller chairs in radio, but we tied them to equipment mounted in shock-racks or to the deck with paracord.  Apart from the minor entertainment they provided when the officers were not present, they were not particularly well-liked by the crew since they frequently tipped over in rough seas.  As such, all loose items need to be secured to the compartment bulkheads or the deck.

There's a lot of heavy equipment (space suits, firefighting suits and tanks, machine tools to repair the ship) and consumables (food / water / propellant) that all need to be packed into this ship, so it won't be an orbital version of the Carnival Cruise Lines.  It can still be quite livable and even a fun place (at times) for the crew and passengers if they work and play well together.  I simply don't see the passengers as being anything other than a walk-on part of the ship's compliment.  66 people aren't going to wait hand-and-foot on 1,000 passengers for 6 to 9 months for low pay and no place to spend it.  Perhaps lighter weight rescue balls can be substituted for the women and children, but the men need to have FFE and space suits so that they can fight fires and repair the hull of the ship.  It would be irresponsible in the extreme not to carry this equipment, though.

The women will care for the children, tend to the sick or elderly, do laundry, and teach.  The men will prepare meals, clean or repair the ship, and train to fight fires or deal with any other shipboard emergencies like casualty evacuation.  The officers and crew will con the ship, stand various watches, and plan / coordinate activities.  I know you really want this to be a cruise liner in space, but that's a personal wish list item that's not very amenable to the unforgiving reality of living and working in an immediately lethal environment.  Giving everyone a job to do also prevents a lot of the mischief coming from idle hands- and despite whatever you may think, this will become a problem.  Duty and responsibility gives meaning to life, and the ultimate purpose of work is to gain leisure.  So long as everyone is working together to achieve the common goal of getting everyone to Mars in one piece, the ship will run smoothly and any problems encountered along the way will be adequately dealt with.

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#949 2021-12-03 07:29:43

tahanson43206
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Registered: 2018-04-27
Posts: 8,112

Re: Large scale colonization ship

For kbd512 re #948

SearchTerm:carrier life aboard a large sea-going vessel
SearchTerm:Mass estimates of requirements for (Large Ship)
SearchTerm:Gender roles of aboard ship

(th)

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#950 2021-12-03 07:32:48

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 1,338

Re: Large scale colonization ship

One option for producing metals that retain strength until a high fraction of melting point is to use mechanical alloys.  This is basically a metal substrate with ceramic fibres embedded within it.  Unfortunately, it isn't an easy thing to manufacture, because the matrix must be assembled by layered vapour deposition of metal onto the ceramic fibres.  A slow and tedious process that makes mechanical alloys expensive.  They have been suggested as cladding materials in some nuclear reactor designs, where efficiency is a function of coolant temperature.  A stainless steel that keeps a lot of its room temperature strength at temperatures approaching 1000°C,  is clearly valuable in this application.  Only affordable at high burn up.

I would agree that it doesn't make sense to have idle passengers on a long-duration space flight.  Running the ship during transit is part of the cost of passage.  They would be bored to tears is they spend six months looking out of the window.  Even with nuclear pulse propulsion, extensive recreational facility are going to be an unaffordable mass burden in my opinion.

Last edited by Calliban (2021-12-03 07:41:32)


"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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