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#126 2022-06-20 09:51:31

SpaceNut
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From: New Hampshire
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Re: A More Practical Interplanetary Colonization Ship

The system is a cross between iss and a submarines which means replacement water is the requirement and that is where the sabetier reactor should come in as it would cut down on the water loss. Which means dumping methane overboard and not oxygen.

https://www.nasa.gov/mission_pages/stat … atier.html

https://space.nss.org/settlement/nasa/t … o_gen.html

The Li-co2 sounds like a flow battery in function and seems worth investing for mars power systems.

Its these combinations of thoughts that could lead to a residential solution for those facing drought conditions.

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#127 2022-06-20 10:33:32

kbd512
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Re: A More Practical Interplanetary Colonization Ship

SpaceNut,

Why SOFC's were not developed to recover O2 from CO2 aboard ISS is a great question, though.  I wonder if eventual plate-out of the fuel cell was a design consideration.  I think it would have to be.  Hopefully the MOXIE SOFC sent to Mars aboard Perseverance can help answer questions about the long term durability and reliability of the fuel cell in an operational environment.  A ship would be a more benign operating environment than the surface of Mars- very little dust and no mildly cryogenically cold nights to contend with.  All that Carbon has to go somewhere, which means a periodic cleaning task for the crew- probably less of a problem in a 1g environment than 0g.  You definitely don't want Carbon dust inside the ship.  The fuel cell itself is also easily hot enough to melt steel.  Aboard a ship, however, said SOFC would remain "hot" 24/7 except during cleaning events, so cracking from continual thermal cycling should be less of an issue.

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#128 2022-06-20 10:41:58

kbd512
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Re: A More Practical Interplanetary Colonization Ship

SpaceNut,

Yes, when waste CO2 and waste H2 are combined in a Sabatier reactor after water splitting, you dump CH4 instead of O2.  However, water electrolysis plus a Sabatier reactor is still more energy-intensive than splitting CO2 in a less efficient SOFC vs a state-of-the-art PEMFC used for H2 cracking, so there must be significant technical challenges associated with directly recovering O2 from waste CO2.  Alternatively, NASA created a Rube Goldberg to solve O2 recovery, which also seems pretty unlikely, so I'm going with severe technical challenges as the most likely answer for NASA not using direct O2 recovery aboard ISS.

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#129 2022-06-20 10:49:53

SpaceNut
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Re: A More Practical Interplanetary Colonization Ship

For the trial 300 w used to pull mars co2 which is 96% we got 5.4 g oxygen in an hour which was shy of the 10 grams that it was to produce. Carbon monoxide is expelled harmlessly back into the atmosphere of mars or expelled from the large ship.

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#130 2022-06-20 12:23:02

kbd512
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Re: A More Practical Interplanetary Colonization Ship

SpaceNut,

If the MOXIE SOFC is producing CO vs C and O2, then that means we're only getting half of our O2 back, which makes water splitting and a Sabatier reaction look much more favorable in terms of total energy expenditure for a given O2 recovery rate.  Now what NASA did makes perfect sense to me, and again, there are likely technical challenges with plate-out to recover 100% of O2 from CO2 using SOFCs.  Either way, the Sabatier reactor looks like the simplest / least energy-intensive path towards full O2 recovery.  You end up loosing some H2O in the form of H2 split-off and combined with CO2 to create CH4, but since H2 is only 11% of H2O by mass, you end up saving mass by using a Sabatier reactor.  Since mass is the most expensive thing to replace in space, this would seem to be the best compromise solution.

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#131 2022-06-20 17:16:38

SpaceNut
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Re: A More Practical Interplanetary Colonization Ship

round up repost

kbd512 wrote:

tahanson43206,

Target all-up-weight for my ship is 1,000t.  Ship uses laser ablation propulsion that can vary thrust and specific impulse independently of each other.  Ship requires solar-powered laser satellites in GEO or higher orbits generating about 25MWe to produce laser power sufficient to ablate the propellant.  All propellant (Aluminum or Alumina Oxide) is aboard the ship.  A similar laser remote power satellite system must also be in place at Mars.  Laser focuses beam power on a plate of solid Aluminum on the rear of the ship with a high pulse repetition rate to increase thrust without melting the Aluminum, except for a very thin layer.  IIRC, ship requires about 1kN of thrust to achieve escape velocity in about 39 days and some change.  Transit time can be decreased by increasing the laser power / pulse repetition rate or by increasing the number of laser remote power satellites.  All basic experiments to confirm thrust generated, specific impulse, and required beam coherency over target distances have been carried out on Earth already.  All passengers will have to remain in the spokes connected to the counter-rotating habitation rings during Trans-Mars Injection / TMI period for proper radiation shielding, because there's no practical way to carry enough water for ionizing radiation mitigation during the extended transit through Earth's Van Allen belts.  All life support requirements should require about 160kWe of onboard generating capacity, or less, which is exactly what ISS generates.

Life support power requirement was determined by scaling up the ISS-tested CAMRAS / RCA 3.0 amine swing bed CO2 scrubbers, OGA, ventilation fan power, and IWP next-gen / "exploration class" life support systems developed for Orion, Mars space suits, and the Lunar Gateway.  BTW, this amount of power must be generated 24/7/365, without interruption, including when the ship is at Mars, 2X further from the Sun than Earth, and that is how the solar array was sized.

Total ship empty weight target of 250t was arrived at using C250 "maraging" (martensitic aging) sheet steel (250ksi min yield strength), "next-gen" life support systems tested aboard ISS, Aluminum wiring, Nextel/Kevlar "stuffed" Whipple shielding.  Total onboard food and water rations must be reduced to a 1 year supply to meet the all-up mass target.  The ship will nominally be in transit for 6 months and must be braked into orbit around Mars using a laser power satellite permanently stationed at Mars.  Apart from control moment gyros for attitude control and a small electric-based reaction control system for mid-course trajectory corrections, there won't be any other onboard propulsion systems because this greatly increases mass and cost.

We need to divorce propulsion power generation mass from the ship, even if it's technically feasible to include the power generation mass with the ship.  The goal here is to deliver people with maximum efficiency and therefore minimum cost, a modicum of comfort, and exceptionally high reliability.  Apart from low-thrust leading to increased Van Allen belt radiation exposures that must be mitigated, minimum cost all-electric in-space propulsion excels at providing the required thrust and specific impulse for efficient interplanetary transits.

Every bit of dead weight carried back-and-forth between Mars and Earth drastically increases the cost of the mission, which is why we will stop doing that.  This is also why chemical propulsion near the 1,000t payload class becomes very impractical.  Starship has to load 1,100t of LOX/LCH4 to deliver 150t to Mars, so 5,133t of the same propellant would be required to TMI 1,000t, with no possibility of doing anything except aerobraking into the Martian atmosphere at the other end.  The total "dead head" payload will be about 700t or so.  At the 5,000s or so that laser propulsion can provide by ablating Aluminum, a single propellant load is sufficient for spiral-out to Mars, spiral-in to Mars, and spiral-in to Earth without a refill.  Perhaps most importantly, Aluminum propellant is indefinitely storable, whereas cryogenic liquids are not.

This ship is not reliant upon any nuclear power or propulsion technologies that may never see serious development effort in the next decade.  A small space-rated nuclear reactor would obviously be a boon to ship development and possibly propulsion as well, but not required for inner solar system transits.  Apart from the laser power satellites which are technically dual-purpose defense hardware, every bit of the ship technology will be COTS or commercialized NASA space-related technology (CAMRAS / OGA / IWP) available to American corporations and select foreign partners, such as the European Space Agency.  The power satellites can be controlled by NASA, so that no civilians are in control of dual-purpose hardware, and used for various robotic interplanetary exploration or space debris removal efforts as well.

We are not going to reinvent any wheels here.  We need some very pointed propulsion development technology related to creating laser-based solar power satellites.  Everything but the propulsion system will be stock hardware from NASA.  US DoD is already developing the laser technology, which we will need to either scale-up or distribute and coordinate for civil propulsion purposes.  We need engineering development of the ship itself, which will include development of the forming dies to wrap the C250 steel over and then laser or electric resistance weld into place.  If we opt to use laser welding, then we need more precise butt-joint alignment.  If we opt for electric resistance welding, then we will wrap the slit coil sheet steel around the mandrel, then continuously seam-weld a thin steel tape over the joints, which don't need to be all that precise.  So long as the steel tape covers the seam between the inner layer of steel wrapped over the mandrel, it will seal.  We're going to do this from both directions, meaning interior and exterior, so welded sheet steel tape is sealing the habitation ring from both sides.

Megawatt lasers should be ready around 2023 and the SpaceX BFR would be able to deploy them in space

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#132 2022-06-21 04:17:56

Calliban
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Re: A More Practical Interplanetary Colonization Ship

Interesting.  If the ship is using low thrust laser ablation propulsion, substantial dV can be saved by having it depart and arrive into high Earth orbit.  A lot of the high thrust requirements for orbital insertion from the hohman transfer orbit, result from entering Earth gravity well.  If that can be done at say lunar orbital distance, then the job of braking the spacecraft becomes easier.  We could use a cycler to ferry people from LEO to HEO and small transfer vehicles from LEO to cycler and cycler to interplanetary ship.  At the Mars end, the gravity well is far less steep.

One of the problems with laser propulsion is that the lasers are in orbit and could be on the wrong side of the planet when the ship arrives.  That presumably means you need multiple laser stations along the length of the orbit.  Transmitting over tens of thousands of km also requires excellent beam coherence.  Still, this idea is probably technically easier than building gas cored fission reactors, which like all else nuclear, is rendered almost impossible by Earth based regulators.  When we have sufficient industrial capacity on Mars, we can hopefullg bypass these luddites.  But ablation propulsion is something we can work with in the mean time.

Last edited by Calliban (2022-06-21 04:32:00)


"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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#133 2022-06-21 05:03:29

kbd512
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Re: A More Practical Interplanetary Colonization Ship

Calliban,

The issue with using higher orbits is that you still have to get there somehow and you're still transiting through a high-radiation area, so you're limited to using chemical propulsion to do that fast enough.  If you use ISS-like orbits for loading passengers and consumables, then you get maximum payload performance, radiation is minimized, you're up high enough that orbital decay takes some time.  The lasers need to remain in GEO orbits where they can reach a significant portion of the planet to push payloads and the total number required is minimized.

I agree that nuclear power would make the propulsion problem easier to solve, but we don't have any at the moment.  We have thin film solar aboard ISS, we have MW-class fiber lasers in defense contractor labs on Earth, we use adaptive optics to make the beam coherent at a point in space well beyond the source emitter, and we currently use kW-class lasers to ablate Aluminum and other metal substrates for commercial / industrial purposes.  It's not as if we don't know how this stuff works, we're simply choosing to "make a meal" out of the process of combining lasers and thin film solar aboard a satellite in a tonnage class that we've already deployed to GEO.  Basically, this is an engineering problem, not a basic technology problem.  We know how it works and we use the technologies separately, but now we need to combine them in order to move large ships efficiently.  I've looked at the ion engine and plasma engine alternatives, and while they're also highly efficient and potentially promising if thrust can be improved, the thrust is too low at present and most of them use exotic or non-storable propellants.

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#134 2022-06-21 06:00:28

Calliban
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From: Northern England, UK
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Re: A More Practical Interplanetary Colonization Ship

Sounds like these lasers could also be used to dispose of space junk when there aren't any ships around.  A nice little bonus.  Use radar to track the particles and then use the lasers to lower their perogee into the Earth's ionosphere.  All of the junk in LEO can be cleared out in just a few years.  (This is also a clean way of disposing of enemy satellites).

One thing that is good about this idea is that the lasers do not need to be mounted onto a single satellite.  Hundreds of small solar powered satellites do the job just as well.

Regarding the cycler: this is essentially a space station on a highly elliptical orbit.  At its perigee, its altitude could be 500km.  But its apogee could be all the way out to the moon.  The advantage is a well shielded and spacious habitat that can safely cross the van allen belts and will do so continuously with no additional propellant.  The downside is a lot of propulsive dV needed to dock with it in LEO.  And this is about shipping people not supplies.  Maybe it is less than optimal in this situation.

Last edited by Calliban (2022-06-21 06:08:06)


"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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#135 2022-06-21 19:23:48

kbd512
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Re: A More Practical Interplanetary Colonization Ship

POST RELOCATED FROM LARGE SHIP FINANCE TOPIC

FriendOfQuark1,

The US Air Force is developing megawatt-class adaptive optics fiber channel laser satellite technology no matter what anyone else says or does.  They're not going to stop.  I want to give them a bonafide dual-purpose use for the technology that provides a plausible alternative civil use and allows them to conduct regular "target practice" on moving targets so that the presence of such technology is "normalized".  This will not be "speculative technology" for very long.  It's one of the reasons that the US Air Force / US Space Force funded Starship development.  They wanted the ability to launch sizable military payloads using Starship.  NASA is also funding Starship development for other reasons.  A first launch date has already been set for Starship and approved by all the relevant government agencies.

The laser tech has developed to the point where they're achieving 4kg/kW of laser output power.  The laser equipment (all of it, less thermal management) would then weigh 4,000kg/MW of output.  The thin film solar tech has developed to the point where 1.25kW/kg is flying in orbit aboard ISS and they're developing 2.5kW/kg panels.  The 2MW of output for a 50% efficient fiber channel laser would then weigh 1,600kg.  A 10,000kg class laser satellite payload in GEO is what we're talking about, and what US Air Force / US Space Force is developing.  If Lockheed-Martin or Northrop-Grumman come close to meeting the 2kg/kW aspirational program goal, then commodity rockets of the sort that Rocket Labs, Blue Origin, and others are developing could deliver the satellites to GEO.  This sort of military technology will be transformed into technological reality sooner rather than later.

Optics and Photonics News - High Power Fiber Lasers

I looked at X3 ion engines (real NASA hardware) and MPD plasma engine (still real hardware, more frequently used by universities than space agencies due to a lack of input power, but never subjected to the long duration tests that ion engines have been subjected to) technologies first, but both of these engines would require very large onboard solar arrays or distributed power input, or small nuclear reactors, and/or exotic and expensive propellants that make them unsuitable for commercial use aboard spacecraft that are double the mass of the ISS.

I want to mount an Aluminum plate to the black of my ship, similar to the giant Aluminum thermal radiator plate used aboard Skylab, and hit that plate with the laser to generate thrust.  Dependent upon cost, this represents between $500K to $1M of Aluminum and if Starship can provide transport at $2M per launch, $4M in launch costs, so $5M in total.  Propellant then represents $10K of the total ticket price, per passenger.  In terms of calories, whole wheat flour provides 3,400 calories per kilogram, which will also remain shelf-stable for longer than the total mission duration if kept frozen.  A 180 day transit would consume 53t of flour to provide a 2,000 calorie per day diet for 500 people.  Every day, 500 crew consumes 1,000,000 calories if provided with a 2,000 calorie diet.  Flour is obviously not the only food we'll feed the crew, and I intended to allocate 150t of food per mission, but flour is a staple of western diets that prevents anyone from starving to death.  I can't speculate on the future cost of food, but 150t is 1 Starship payload that also represents another $2M in launch costs, $4,000 per person.  If we allocate 150t of water per mission / 300kg per person / 79 gallons per person, then another $4,000 per person.  1 Starship flight will be allocated to carrying 500 people to the ship, and represents another $4,000 in launch costs.  So... $22,000 USD covers launch costs for all consumables provided from Earth, including propellant.

If that seems unaffordable, then recall that SpaceX has to launch 6 to 8 tanker flights to send a single Starship carrying 100 people, anywhere beyond LEO.  SpaceX's propellant and consumables cost could be near-zero, but each passenger would still pay a minimum of $140,000 USD in terms of launch costs (6 tanker flights plus their ride to Mars).  Aboard Starship, they have very little radiation shielding in case of a solar flare, no MMOD shielding, no artificial gravity, no massively redundant life support, and only enough consumables to get there alive.  Starship is the upper stage of a rocket.  Rocket upper stages must remain lightweight in order to do what they do best.

The large ship program is also a mutually-supportive space flight endeavor.  We simultaneously justify Starship mass production, military laser satellite development and mass production, and large ship deployment.  We can drastically cut down on the number of consumables flights because propellant becomes a minor fraction of the total cost.  2 flights for propellant, another 2 for consumables, and 1 for delivery of the Mars colonists themselves.  Short of a Starship redesign to provide double the payload capacity or humanity discovering propellant-less in-space propulsion methods, I can't see us getting substantially more efficient than that using conventional chemical rockets.

Elon Musk wants to put 1,000,000 people on Mars over about 40 years, which represents 18 launch opportunities.  That means 55,555 people need to be transported there at every launch opportunity.  We're not going to do that using ships carrying 100 passengers apiece, because we'd need at least 555 ships.  We'd still need 111 ships using this scheme.  However, for comparison purposes the worldwide fleet of Airbus A380 aircraft includes 251 ships.  My proposed fleet size is less than half as many ships, similar in capacity to an A380.  A typical A380 seats 525 passengers.  The last variants of the Boeing 747 seated a similar number of passengers.  We're also seating about 500 passengers.  Our ships are made from welded high strength steel rather than Aluminum and composites, but they contain fabric covers, a similar amount of wiring and electronics, as well as life support systems not used in commercial aircraft.  The expensive turbofan engines that make each A380 or 747 hull are not present, so it's reasonable to think that fabrication costs will be similar after launch costs, materials, and specialty equipment are taken into account.  The empty weight of each ship will be quite similar to the A380, which weighs 277,000kg / 277t.  My ship design will have a maximum operating empty weight of 250t (all structures, wiring, life support, avionics, and photovoltaics).

7075 Aluminum (63ksi to 69ksi yield strength) and CFRP (467ksi with high modulus fibers) are very expensive compared to just about any type of steel, but they're very popular in airliner construction, which require greater material thickness to achieve greater stiffness at reduced weight, in order to resist aerodynamic loads imposed by high speed flight, and compound curves for improved aerodynamics.  In the case of a tin can floating in space, which never sees any aero loads and for which aerodynamics is an entirely moot point, lower-cost high strength steel is sufficient for the job.  C250 is about 2X the cost of standard structural steel and about 2/3rds the cost of stainless, which is considerably weaker (40ksi yield strength, little different than the 2219 Aluminum, what NASA calls "hard alloy", used in the SLS core tank).  C250 is about $1,000/t to $1,200/t, the 304L used in Starship is about $1,500 per metric ton, whereas 2219 is about $2,500/t.  Anyway, I'd much rather spend money on life support / wiring / solar panels than exotic / expensive hull materials.  We're not spending money for sake of doing so.

The Nextel fabrics are about $1,000 to $1,500 per square yard at retail prices.  Pretty much every square inch of pressurized space must be wrapped in multiple layers of this or a similar fabric, so that's our major cost center.  EF-11 only weighs about 370g/m^2, so the mass penalty is very slight.  I don't know if we can get a bulk discount by purchasing directly from 3M, but at retail prices that's a minimum of $159M for six layers of that stuff.  If I had to guess, the cost of covering the hull with appropriate insulation / MMOD protection will greatly exceed the cost of all other components, because we're opting for low-cost materials everywhere we can.

Thin film solar is now about $1 to $1.5 per Watt, so $240,000 for the solar panels.

I don't know what the life support equipment will cost when it's mass-manufactured, but the electronics will be where most of the money is spent because the bulk materials (Aluminum alloys and zeolites) are relatively cheap.  This is something that Tesla could make, and they did start making ventilators during the pandemic.

The hull forming mandrels and welding equipment will range into the low tens of millions of dollars, mostly because INVAR or COVAR dies / mandrels are very expensive to make (frequently used in aerospace composites or injection molded plastics manufacturing).  The C250 sheet steel hull will be wrapped around the die and continuously seam welded by applying electrical resistance over the steel tape, similar to how seam welded pipes of arbitrary length are made.  The welding technique is also very similar to the spot and seam welding technology used in aerosol can manufacturing.  The process itself is very cheap and fast.  ERW uses modestly more power than a laser or EBW, but it's exceptionally fast for thin sheet steel.  If sufficient hull material and heat rejection capacity is available, then hull welding could literally be done and over with well inside of a week.  It'll take much longer to outfit the ship with wiring and life support systems than it will to form the hull.  Over the hull, we will apply a white ceramic using plasma spray that provides electrical isolation and extreme corrosion protection.  Since the ceramic material is non-flammable, it will greatly reduce the risk of fire, as compared to conventional paint.  It also reflects light, similar to to the white paint applied to the inside of Navy ships.

At a high level, we will form the hull from high strength structural steel (C250 is aircraft landing gear steel), wrap the exterior of the ship in high performance ballistic fabrics to absorb MMOD impacts, spin both habitation rings in opposite directions to counteract gyroscopic precession without the need for inordinately heavy / power-hungry gyros, simplifying attitude control and maneuvering in the process, and providing the artificial gravity that humans (and normal toilets / washing machines / sinks / showers) need for optimum functioning.  The ship development program money will be devoted to good basic design that appropriately compartmentalizes the vessel to assure survival after a hull breach, the all-important redundant life support systems, radiation and micrometeorite impact protection measures using mass of consumables as the shielding material, control avionics, and solar panels.  The ship doesn't have much in the way of expensive onboard propulsion technology because it won't need much when primary propulsive power is provided at both endpoints of its transit.

Humans aren't leaving Earth and they won't be leaving Mars if we decide to colonize it, so having minimal orbital support infrastructure in place, such as laser-based remote power / propulsion, is good common sense.  If we attempt to drag every ton of power and propulsion system mass with us, everywhere we go, then we'll only succeed in making space colonization unaffordable, which is exactly where we're already stuck at due to the mass and therefore cost penalties imposed by low-Isp chemical propulsion.  If lower cost bulk material transport to orbit becomes available along the way, such as "SpinLaunch", then we'll incorporate those cost reductions as they become available.  As of right now, I think 3 Starship launches are sufficient to fabricate and outfit a single ship.  In the broader context of what SpaceX intends to do to support Starship flights to Mars, that seems like a very reasonable alternative.

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#136 2022-06-21 19:38:03

SpaceNut
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Re: A More Practical Interplanetary Colonization Ship

It is said that fuel is the smaller cost of any mission launch.. thanks for the laser data to think about.

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#137 2022-06-22 16:15:15

kbd512
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Re: A More Practical Interplanetary Colonization Ship

SpaceNut,

Lots of things "said about fuel costs" only apply when the fuel quantities you're consuming don't exceed the total fuel consumption (for natural gas) of the United States, by a factor of 2.  When you start exceeding the fuel consumption of an entire country, a very large one with one of the highest per-capita energy consumption rates in the world at that, then people who can do basic math take notice.

Once again, this is NOT about ideology or support for SpaceX or a tirade against chemical propulsion.  I love what SpaceX does.  I know that we would never get to space without conventional chemical rockets, and thus wouldn't be having this conversation.  I can also do basic math.  Sometimes I make mistakes, but this is a simple multiplication problem that can be done on a pocket calculator.  Most math problems with results that matter, at a global scale, seem to be rather simple multiplication problems.  If you understand the inputs and outputs, then you multiply to arrive at your answer.  Whenever someone tells me that they need more natural gas than America consumes for their Mars colonization scheme to work, then I presume they're either setting up their own very large scale natural gas synthesis plant or they're talking out their rear end and hoping nobody else notices.

Since I've seen no plans for the former, nor mere talk of it, I must assume the latter.  Under my propulsion schemes, we will consume 0.65% of the total US annual natural gas consumption.  Under the SpaceX propulsion scheme, we consume twice as much natural gas as the entire US, every single year for decades on end.  One scheme seems a lot more practical and plausible than the other.  It's not that I don't like their idea, it's that basic math tells me that it requires even more development work and resource inputs than my idea, and not by a little bit.

If SpaceX starts talking about building the world's largest natural gas synthesis plant, bar none, then fine, I'm onboard with that.  I don't care how a ship is propelled to Mars, so long as it gets there in one piece.

There's nothing speculative about what I've proposed.  High-power fiber channel lasers are real technology.  Adaptive optics are real technology.  If they didn't work, then the military's laser weapons wouldn't work, but clearly they do since they can shoot down missiles from miles away.  Solar-powered satellites are real technology.  Laser ablation of metal substrates is a real industrial process used every day to manufacture semiconductors and other parts.  The work to figure out how much power per unit of thrust and how well lasers work for propulsion has already been completed and revisited again and again.  Basically, all the individual technologies work and all required technologies are at least as affordable as chemical rocket engines.

If the alternative is burning through double the amount of natural gas that the entire US consumes every year, for purposes of launching rockets and refueling them in orbit, then yes, I think this is much more practical to do at the scale required.

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#138 2022-06-22 17:57:47

Calliban
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From: Northern England, UK
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Posts: 2,212

Re: A More Practical Interplanetary Colonization Ship

Having watched about a dozen of Peter Zeihan's videos, I begin to wonder how much Mars colonisation the world will be able to afford a decade from now.  World GDP is going to collapse as globalisation unravels.  China is going to disappear altogether.  East Asian countries are going to face declining GDP due to collapsing population.  In the developed world, we are going to see the largest decline in human numbers since the black death.  Europe is facing a combined demographic and energy crisis that could take a century to recover from.  The US and South America look set to be the last ones standing with a broadly industrialised and wealthy economy.  That's not to say that these places are going to escape the consequences of the coming bust.  But Russia and China look like they will disappear as credible rivals.  Saudi and Iran could start obliterating each other if the US withdraws from the gulf.  The world we are heading into looks a lit poorer and hungrier.  If Mars colonisation happens at all, it is going to be a US led effort.  No one else is going to have the capability or interest.

Last edited by Calliban (2022-06-22 17:58:23)


"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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#139 2022-06-23 15:06:20

kbd512
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Re: A More Practical Interplanetary Colonization Ship

Calliban,

I still think a Mars colonization campaign is a practical endeavor, but not using chemical propulsion alone.

GDP collapse is not a given, but population collapse is now inevitable.  If a man has two sons and one of his sons dies prior to inheriting the family fortune, the surviving son does not become less wealthy.  If that were to happen all across the world, the survivors still do not become less wealthy, but the sum total human brain power available to solve problems is greatly diminished, the total wealth distribution is diminished, and thus more pointed wealth allocation becomes mandatory and discretionary projects that may or may not create new groups of very wealthy individuals are also greatly diminished.  The potential productive capacity of the dead son is lost forever, but so is his consumption capacity.  There's little net economic change from the loss.  Losing people will never help the economy, and that's pretty much guaranteed, but the state of human advancement doesn't automatically go away.

I think a more apt description is that economics driven by volume will collapse within the coming decades, largely de-justifying supply chains that wrap around the world several times.  There will not be enough people, and therefore enough volume of sales of products, for any of that to make sense.  More locally-based goods and services will be consumed instead.  It's not clear to me if there was ever a net benefit to the major companies doing such things, but like so many other "get rich quick schemes" on the part of management, their attempts to cheap-out on labor and material costs have now run their course.  America is coming full-circle on offshoring, and to little surprise of anyone paying attention, we're right back where we started.

In a world with dwindling resources, quality and overall efficiency matter greatly.  Pinching that last penny is only likely to lead to total losses.  Short-term thinking rarely pays off over enough time.  I think some of the automotive manufacturers now see the writing on the wall- improve your product and thus your value proposition to your customers, else someone who "does it better" will replace you or customers will simply not buy your product.  Either way, now they have to start responding to what consumers actually want.

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#140 2022-06-23 22:52:17

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 2,212

Re: A More Practical Interplanetary Colonization Ship

Obviously I agree that Mars colonisation is worth doing.  But Peter Zeihan's work changes a lot of the assumptions that many of us had about how this might be taking place.  Much of the world is going to be in turmoil over the next thirty years.  It is hard to know exactly how this will affect the capabilities of the US and other players in space.

Demographic decline is an enormous problem that will result in reductions in GDP in many countries.  You are correct that physical capital that has built up over time will not disappear over night.  But it does requure maintainance and replacement over time, which requires investment.  An ageing and shrinking population leads to a number of problems simultaneously.  A country's GDP is equal to its working age population x labour force participation rate x average productivity per worker.  There is no way around that.  And as the age structure of the population shifts upwards, a smaller working age population must support a larger population of retirees.  That smaller population must pay sufficient taxes to maintain public services that everyone is using.  On the other side, a smaller working age population means a smaller consumer base, which robs industry of economy of scale.  If the 40-60 age group declines, then investment flow into infrastructure and industry declines.  A shrinking and ageing population squeezes society in so many different ways, that it raises the risk of complete systematic collapse.  This appears to be the future for East Asia, Russia and probably Europe as well.

The future of Mars colonisation really is going to depend on NAFTA, which the UK and Australia will probably end up joining.  Japan will ultimately be drawn into a more intimate relationship with NAFTA as it's Asian trading partners collapse.  But it will lack a substantial surplus population to support actual colonisation efforts.  This means that a future colonised Mars is going to have a very specific Anglo-US Australian cultural leaning, with Hispanic elements part of the mix.  That has interesting implications for how Martian society will look, how it will solve problems and evolve.  But I digress.

There is really no near term alternative to chemical rockets for reaching Earth orbital velocity from Earth surface.  But for Earth-orbit to Mars-orbit transit, I agree that a low-thrust, high-ISP pure space ferry is a lower cost design than trying refuel low ISP Starships with multiple tanker flights.  I think the design process for a near term colonisation ship needs to be carefully balanced.  Essentially, we are trying to reduce the cost of Mars transit as much as possible, whilst also reducing its dangers.  The dangers are low G health deterioration, space radiation, pychological factors from confinement and systems breakdown leading to suffocation, dehydration, starvation, etc.

There needs to be careful consideration of which hazards we are prepared to tolerate and to what degree.  For example, a compact ship is cheaper, but more crowded and less comfortable.  Compact living arrangements are easier to shield using provisions, which greatly reduces launch mass.  But a crowded ship raises risks of psychological consequences.  To what extent do we allow higher cosmic radiation doses in order to reduce the shield mass of the ship?  Zero G for six months, raises health risks.  But how much money should we be prepared to spend to mitigate this risk?  How much does artificial gravity add to the cost of the ship?  These are all optioneering questions that need to be answered before we begin designing anything.  It is frustrating when the answers to these questikns are hard to pin down.  But the costs differences implied are not trivial.

Last edited by Calliban (2022-06-23 23:22:45)


"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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#141 2022-06-24 07:13:47

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 26,750

Re: A More Practical Interplanetary Colonization Ship

snippet repost

kbd512 wrote:

SpaceNut,

The large ship concept is forward-thinking.  The large ship concept is not a replacement for Starship.  Both technologies are complementary, meaning each does something so much better than the other that there's merit to investment in both.  We can't colonize other planets in a practical manner using the upper stages of rockets, nor can ships the size of the ISS land on other planets.  I didn't "decide" that the universe would or should operate this way, basic physics did.

Starship has to meet design requirements for an upper stage of a rocket that's also capable of vertical take-off and landing.  It will always be sub-optimal for in-space transport for that reason.  The large ship is an object sent into space once per vehicle lifetime, much like the ISS, which has proven to last for at least 20 years using weaker materials like 2219 Aluminum alloys.  After construction, a large ship stays in space, no different than the ISS.

The dry mass of the Starship upper stage falls between 150t and 200t.  My ship concept is only about 50t heavier than a Starship in terms of total dry mass, yet it also carries about twice the payload mass of a Starship.  250t of food / water / air plus 50t for the colonists and their personal effects.  In theory, you could send a Starship to orbit and then retrofit the AG components to create the sort of ship I had in mind.  It's not going to land anywhere afterwards, because it can't.

In terms of total mass for a round trip to Mars, my ship concept is equivalent to the propellant load of a Starship.  It requires fewer flights to restock / refuel than the propellant launches required to refuel a Starship in orbit to send it to Mars.  Over enough flights, that becomes drastically less expensive to operate than a much larger fleet of Starships.  Ultimately, the food to travel to Mars will be produced in orbit or on Mars, the Oxygen will come from lunar regolith or Mars, and the water will also be sourced from the moon or Mars.  At that point, the cost of  the consumables is borne by the Mars colony or lunar base, not people living on Earth.

As our closed-loop life support slowly but surely increases air and water recycling efficiency to near 100%, eventually the only Starship flights required to go to Mars are the ones required to reach orbit from the surface of the Earth and the one required to take you from Mars orbit to the surface of Mars.  It's not feasible to get much more efficient than that.  Right now, we're stuck with ye olde "chicken-and-egg" conundrum.  It's too expensive to colonize Mars because nobody has built out the infrastructure to make it more affordable, and therefore the infrastructure hasn't been built so nobody can afford to go.  That situation won't change itself.  A miracle is not going to happen.  It's never going to get any cheaper to fly into space, never mind go anywhere after you get into space, using the technology we're already using.  Airline ticket prices have only gone up over time as the jets and jet fuel become more expensive.  Wages have also risen to the point where an ever-greater number of people can afford to fly once per year on their own dime.  For that end result to occur, major investments into the airports and aircraft and academia was required first.  Jet aircraft made flying affordable for the masses by making it feasible to stuff more butts into seats, per aircraft, and to complete more flights per aircraft per day, than their piston-powered equivalents.

I sized my large ship concept based upon the maximum number of colonists a single Starship could reasonably take to orbit.  To achieve even greater efficiency, you need a bigger conventional rocket.  I don't know how to stuff more butts into seats using SpaceX's existing Starship design, in a practical manner.  It's technically feasible to cram more people inside, but doing so would also put them in greater danger for little to no practical benefit.  I don't want to explain to the parents of 750 to 1,000 young people that all of their children died so that we could charge $2,000 vs $4,000 for the flight.  At a certain point, being "just a little" cheaper doesn't pay off over time.

Thanks as this puts more details to the project.

The mass seems right inline with calculations done for RobertDycks ship size using starship mass for construction values for that ring size approximates. But I think that was much larger than you ships design of which I need to read through the topic to gather.

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#142 2022-06-27 12:20:34

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 11,988

Re: A More Practical Interplanetary Colonization Ship

For kbd512 re laser (or similar) propulsion....

I am mindful of your strong desire to work on this propulsion concept.

What I think about it is irrelevant .... what ** is ** important is that you see potential in the idea, and you want to invest time and energy in seeing how far you can get with it.

I am willing to try to find the support you need.

What seems clear (to me at least) is that you do not have the background to prepare you for a deep dive into this technology.

There are people (still living) who ** have ** made deep dives into the feasibility of using photons to lift space craft.

I have listed one or two names in other topics in the forum.

Any of these folks might be willing to help you, if they think you are a reasonable person and not an unreasonable person.

Again, what ** I ** think is irrelevant.  What knowledgeable people think ** is ** relevant.

(th)

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#143 2022-06-27 18:51:37

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 26,750

Re: A More Practical Interplanetary Colonization Ship

We need a trial vehicle to develop the skills and beaming of energy to a target vehicle that we are trying to accelerate.

https://en.wikipedia.org/wiki/Solar_sail

High-energy laser beams could be used as an alternative light source to exert much greater force than would be possible using sunlight, a concept known as beam sailing.

220px-Sail-Force1.gif

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#144 2022-06-28 04:20:19

kbd512
Administrator
Registered: 2015-01-02
Posts: 6,222

Re: A More Practical Interplanetary Colonization Ship

tahanson43206,

I have a strong desire to find any workable propulsion concept that can deliver large numbers of people to Mars in a practical and affordable manner that increases the odds that enough people will be able to go there to establish a city on Mars.  Adequate propulsion is an integral part of making that happen.  Chemical propulsion is not affordable for this purpose, nor will it become significantly more affordable in the near future.  It's a known quantity, which is great, but the "total quantity required" is the problem.

I can do enough basic math to know that chemical propulsion is off the table, solid core nuclear thermal is not significantly better, and nobody is working on gas core nuclear thermal rockets at all.  If the propulsion system can't provide about 10kN of thrust and a specific impulse of 5,000s or better, then most of what you're sending to Mars is propellant.  The end goal, when last I checked, is to send lots of people and cargo.  The propulsion system and propellant are simply a means to an end, not an end unto itself.

You're correct that I don't have the background to do a deep-dive into any form of in-space electric propulsion, let alone laser ablation propulsion.  So what?  At this point, we're just a bunch of guys and gals, sitting around dreaming about going to Mars.  The probability that any of us makes any major contribution to that effort, or that anybody who truly does have the expertise would even give us the time of day, is near-zero.  There's a reason I write software for forecasting tools for a living, whereas aerospace engineers work for NASA or defense contractors.  If I was totally fixated on this, then I would've gone to aerospace engineering school and then worked for NASA or SpaceX.  It's still fun to think about, and to try to work out what little I can from what I've read.

I have read the papers published by people who do know what lasers can and cannot do, based upon their research work.  Unless I have wildly misinterpreted their work, then laser ablation can provide the thrust that the various forms of ion or plasma engines cannot, until the input power is scaled-up to tens of megawatts and exotic / hard-to-store / very expensive propellants are used.

I'm not fixated on any specific propulsion concept, unlike some other people here.  I'm only fixated on achieving the end result.  Whatever I have to do or learn about to achieve that result is only incidental to it.  If some other form of adequate propulsion pops up that's much cheaper or easier to do, then I have no qualms about refocusing on the newer / faster / better technology.  I'm pragmatic about this, rather than dogmatic.  If someone can show me that there's a much better or more practical way, then I'm always willing to learn.

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#145 2022-06-28 21:30:35

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 26,750

Re: A More Practical Interplanetary Colonization Ship

What takes all of the fuel is mostly departure from earth's orbit
https://en.wikipedia.org/wiki/Earth_Departure_Stage

https://ntrs.nasa.gov/api/citations/201 … 037210.pdf
Interplanetary Mission Design Handbook - NASA

Keep in mind that a starship starts this with 1200 mt and has 100mt onboard at mars orbit to land with.

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