A More Practical Interplanetary Colonization Ship

kbd512 · 2021-12-21 09:06:28

This topic was started due to the inability of others to allow sensibility to override ego. It was originally posted in the "Large Scale Colonization Ship" thread.

Robert,

My thoughts on this "realistic ship design" are still not organized, but...

Major Subsystem Masses

Pair of Counter-Rotating Vectran Inflatable Hulls - 375t (50,044m^3 pressurized volume)
Interior Furnishings - 125t (furnishings / bedding / clothing storage)
Polymer Bag Water Wall / Life Support system - 275t (250t of potable water at mission start)
Rigid Fiber-Reinforced Plastic Hubs - 100t (Carbon Fiber filled PEEK)
Ship's Crew / Colonists - 100t (includes clothing / bathing / personal electronics mass allocation)
2 Years Provisions - 730t (some of this is regenerative mass provided by your bacteria / algae farm that supplies sugars / starches)
MagBeam Propellant - 350t (assumes an impulsive transfer provided by MagBeam)
ECLSS - (still working this out; will use CNT TEG fabrics / bio CO2 scrubbing / IWP water walls to reduce power consumption)
M2P2 Propellant - (still working this out; but at 50,000s to 90,000s Isp, it won't be that much; for MOI / TEI / EOI)
RCS Propellant - (still working this out; will probably use M2P2 rather than a traditional RCS)
Propulsion - (still working this out; not significant using MagBeam and M2P2)
Power - (still working this out; very tough to pin down, but involve thin film solar)

386kWh/day for ECLSS using existing equipment for 1,000 crew members. 32.5kWh/day for 1,000 iPad Air devices. Perhaps 500kWh/day total.

I predict a total wet mass near 2,500t. This is achievable using near-term electric propulsion technologies, and does not require gigantic solar arrays or gigantic nuclear reactors. If we can get the power from electric tethers, then perhaps we won't even need a large solar array. I think we can combine tethers with M2P2. If we can do that, then ignore everything I wrote about MagBeam, because it will be a technological dead-end requiring excessive mass and power.

Hull Design

If the hull structure was fabricated from layers of Vectran (Liquid Crystal Polymer) fiber, as the Bigelow Aerospace modules were, then 50,000m^3 of pressurized space weighs 375t using a tested safety factor of 4 at an inflation pressure of 14.7psi. The actual test articles were 6.875kg/m^3 of pressurized space (the inflatables that over-inflated by NASA to 58.8psi), but I'm using 7.5kg/m^3. A pair of counter-rotating torus structures at 7.5kg/m^3, with a 25m inner radius / 6.358m tube radius / 31.36m radius of rotation / 25,022m^3 volume, would each weigh 187.5t. That falls well within the payload performance of the cargo variant of Starship. 50m^3 per person is an extremely generous habitable volume allocation, roughly double the 25m^3 that NASA deems necessary for long duration space flight. Since no windows would be present in the habitation rings to induce motion sickness, at 5.37rpm to produce 1g, the angular velocity is feasible with minor adaptation. The solid center barrel section would consist of a fiber-reinforced plastic (not a resin-infused fabric composite). The center barrel would contain the food provisions, life support equipment, propellant, and engines.

The individual compartments would be woven fabric with polymer bag water walls. Even at this relatively small size, we can't afford to protect all areas with water wall shielding, so the shielded areas would be limited to crew quarters and bathrooms. The extensive use of polymers and water provides better shielding per unit mass than light alloys or steels, with respect to alpha / beta / neutron radiation types, though it's performance against high energy photon radiation would be less than ideal. Fortunately, nearly all of the radiation associated with SPE / CME / GCR is of the high energy particle variety.

My cabin furnishings / structures mass allocation per person works out to 125kg per person, so air mattress or cot, fabric clothing storage, and perhaps inflatable desks. There will be no traditional beds, but it will still be quite comfortable.

Propulsion

The more I look at the MagBeam and M2P2 propulsion concept for the large ship concept, the better it looks. Specific Impulse ranges between 50,000 and 90,000 seconds for M2P2. MagBeam would require 15GW of input power and 350t of propellant, which could be N2 siphoned off from the upper atmosphere. The 15GW for MagBeam would be supplied by a regenerative fuel cell or batteries and solar panel power station in orbit around Earth, and would clear the Van Allen belts in mere hours. The power would be supplied by a 2,500t PEM fuel cell that produces water from LOX/LH2. A 1,000kg spacecraft with a 100kg payload can be accelerated to 50km/s to 80km/s over the span of 3 months, with a propellant consumption ranging between 0.25kg and 1kg per day.

Mini-Magnetospheric Plasma Propulsion (M2P2)

ECLSS

This paper from NASA talks about a lot of the concepts you proposed, with respect to a life support system that provides usable food products and life support functions from waste water treatment and using bacteria and algae to do it:

WATER WALLS ARCHITECTURE: MASSIVELY REDUNDANT AND HIGHLY RELIABLE LIFE SUPPORT FOR LONG DURATION EXPLORATION MISSIONS

RobertDyck wrote:

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

Robert,

You're stuck on this military schtick. There was no mention of military anything in my last post. You're still fixated on that. I'm trying to look at power and propulsion technologies that offload crazy power and mass requirements. High strength fabric does a much better job at radiation and projectile protection, it's much lighter than steel, and a 5 Starships can carry the entire dry mass of the ship into orbit. It's not a "tent" of any kind. The walls of the pressure hull are much thicker than anything you can feasibly make from steel and still move it for any reasonable mass and therefore cost. It doesn't matter if you can eventually build ships from mined asteroids if the very first ship never gets built due to cost. MagBeam is a distributed propulsion system that offloads the power plant to a separate orbital facility and allows for impulsive transfers by beaming plasma power to the engines of the propelled vessel, spending mere hours in the Van Allen belts. MagBeam requires a lot of power for a very short period of time measured in hours.

The 50m^3 per person is total pressurized volume in both torus structures. Once you start filling the ship, then it's obviously less, but still more than what NASA specified as the minimum habitable volume for a long duration space flight.

There are no open cycle gas core nuclear rockets in existence and none are being developed. In all probability, none will ever be built, either due to the anti-nuclear whack jobs. I would love to have the technology available, but nobody is pursuing it.

The M2P2 is for propulsion outside of the Van Allen belts. Electrodynamic tethers would work inside the Van Allen belts, and can supply large quantities of electrical power inside or outside the Van Allen belts. Both are very low mass for the power and propulsion provided, because they use external forces for propulsion. It doesn't matter that M2P2 is slower than chemical rockets, because it's fast enough to insert into orbit and spiral back out to Earth.

I want to see a ship capable of carrying 1,000 colonists actually built within our lifetimes. I wanted a great big steel ship like you do, but I don't care about what I personally want to see used, so much as I care about seeing an actual ship built using technology that we can feasibly supply power and propulsion to. I'm still 100% onboard with your ideas about using bio-regenerative life support, because even this much lighter design becomes impractical without it. Lemonade from lemons. That's all this is and all it's ever been about for me, personally.

tahanson43206,

You know why nothing ever gets built?

Most people are too stubborn to admit when they've artificially created an insurmountable problem due to ego or personal likes / dislikes.

Does everything need to be ego-driven, or is it more important to get the job done in a practical manner?

I change things all the time at work, at the behest of others, despite my personal likes / dislikes. I don't get wrapped around the axle by any of it. I still get paid, the company still runs, and life goes on.

Elon Musk let go of his idea about using CFRP for Starship because it was proving too impractical and costly. Wonder of wonders, using a material more appropriate for a very high heat environment of reentry, he built an actual vessel without extreme heat shielding and extreme fabrication cost. The orbital environment is very different. Every kilo of weight counts against you when you have to push it between planets, and going with an all-steel design either means a paper thin hull or far more mass than we can tolerably propel between planets using technology we have or can develop for reasonable cost. Even if we had to replace the Vectran every 5 years, it would still be far less costly to operate than a much heavier design.

After work I will move these posts to a different topic and continue my thoughts about a practical design that we could feasibly build there. I love Robert's concept and ideas, and if someone was building GCNTRs and giant steel interplanetary transports I would cheer, but thus far nobody is doing that, due to cost or politics or whatever. As such, I proposed something quite a bit lighter with more volume and less lavish accommodations.

Remember the SpaceX ITS?

Nobody else does, either. It was a paper rocket that went nowhere because it was a bridge too far, even for SpaceX. Starship is actually being built.

To me, this modification is still Robert's design proposal and I will call it Robert Dyck's Interplanetary Transport Version 2 if it pleases him. It's in keeping with the spirit of what he wants, and only deviates insofar as it uses different hull materials and propulsion methods for the same purpose, in order to make it more practical using what we have, rather than what I wish we had. If he can't see it as a tribute to his excellent ideas, then I guess he can't, but that's what it is.

In the separate topic (yet another), there will be no hyper-sensitivity to any proposals that alter the design concept. If it does something useful or better than what little I can come up with, then it gets included, because the focus is a practical ship design that can be built, rather than me, my ego, or what I like best, because I don't care about any of that. I originally wanted a great big stainless steel ship as well, but then I looked at the mass / power / propulsion requirements and eventually came to my senses. I care about putting a proposal together that a company could feasibly construct and operate without requiring NASA-level funding. Anyway, I've already given credit where credit is due.

This "I don't like your idea, move it to a separate topic" silliness is how we end up with a bunch of separate topics all discussing the same basic ideas. I don't get it. We all complain about NIH Syndrome at NASA, but then exhibit it ourselves at every turn.

Last edited by kbd512 (2021-12-21 09:10:31)

kbd512 · 2021-12-21 09:22:44

SpaceNut,

I already removed my posts from RobertDyck's "Large Scale Colonization Ship" thread. Feel free to comment. I value free exchange of ideas. I don't care one bit if my ideas are repeated, altered wildly if necessary, critiqued, etc. All comments are welcome, especially those from RobertDyck. Agreement is not required nor expected. This topic is for discussion and vigorous debate, not dictating my personal wants or desires to anyone else. My only desire is to see someone build something using technology we have or could acquire without surmounting a mountain of red tape.

All credit for this concept goes to RobertDyck, in case that point is not crystal clear. This is the embodiment of his truly excellent ideas, with practical considerations given to mass and power and propulsion requirements.

kbd512 · 2021-12-21 09:24:50

Another post moved...

On the call we also discussed the possibility of using multi-layer inflatable fiber-based structures to reduce launch weight. While it would eventually be highly desirable to fabricate the ship's hull using materials mined from asteroids, the weight of stainless steel, relative to its strength, is considerable. To reduce the mass of the large habitation ring to something tolerable for launch aboard a Starship or other Super Heavy Lift Launch Vehicle, it may initially be necessary to consider lighter hull material alternatives until such time as high-Isp / high-thrust engines become available. At the present time, only electric propulsion can provide the high-Isp required for a ship as heavy as this, with or without the use of lightweight woven fiber inflatables, to move beyond LEO using existing engines and propellants. There are a number of promising propulsion concepts that could serve as prime movers for a ship this large, but ion engines are the most well-developed and we know how to scale them up to provide the input power and thrust required.

There is no single fabric with all of the properties that would make it a suitable replacement for steel, but by using multiple layers of Kevlar, Vectran, rubberized fabric to retain pressure, and insulating layers to protect against fires, a complete solution can be provided for far less mass than steel, if both solutions have equivalent strength.

We also discussed the possibility of using composite or glass-filled plastic interior hatches, given how rare a decompression event will be, thus the very limited number of pressure cycles that such composites must withstand. I think a plastic like Zytel would be ideal for this use case, especially if it was thermally protected from fire using a fabric covering. Zytel is frequently used in plastic intake manifolds, radiators, oil pans, and fuel injector bodies for internal combustion engines.

To that end, the power requirement is so large that only a nuclear reactor is a practical power plant. Nuclear power approximately halves the thrusting period by virtue of the fact that it can supply input power to convert to thrust 24/7, irrespective of whether the ship is in the shadow of a planetary body. It makes little difference how far the ship is from the Sun, either, with respect to power output from the reactor, whereas in Mars orbit the Sun has approximately half of the intensity that it has in Earth orbit, so approximately twice the solar panel area is required to generate equivalent input power for the electric propulsion system.

kbd512 · 2021-12-21 09:26:14

Another post moved...

Robert,

If the MPLM was scaled up to provide 4,615m^3 of pressurized volume, it would weigh around 608t. That's remarkably close to the 640t figure I calculated for using BNNT fabrics, except it's nowhere near as strong. Even if we included substantial reinforcement, the steel will never be as strong for any reasonable weight. The Kevlar inflatable modules developed by NASA and ILC Dover were 6.56kg/m^3 of pressurized space, as compared to the MPLM at 131.68kg/m^3 of pressurized space. That's a fairly dramatic difference, wouldn't you say? Those inflatable modules were also tested to a safety factor of 4 (60psi).

Leftist radicals fought against gender roles and used what should have been educational institutions to brainwash other people into believing things that were facially false and absurd. When was the last time you saw a woman hanging off the back of a garbage truck, or a female plumber? I've never seen one. Have you? I'm not saying that women shouldn't be allowed to hold any job that they're qualified to hold, but they're clearly better suited to some jobs than others. In every military there are different physical fitness standards for men and women, otherwise 90%+ of the women would not pass the male physical fitness standards, especially those related to upper body strength. They're not meant to be infantry, plain and simple. Men didn't make that decision for women, either, evolution did. People who believe in science also believe in evolution. Simply declaring biological evolution defunct does not make it so. That doesn't make women any less valuable than men, nor does it mean that their jobs aren't every bit as valuable as the ones that men do. It's a simple acknowledgement that men and women evolved differently and are much better suited to some tasks versus others.

In the nordic countries that have attempted to make everything "gender neutral", nearly all of the nurses and teachers are women, and nearly all of the engineers / soldiers / garbage removers / plumbers are men. Well, why is that? The vast majority of women are interested in people, not things. You can't have much of a relationship with a chunk of Iron, whereas another person can talk to you, they can give and receive affection, can console you when you're feeling depressed- all things that no engine block or software program will ever do for you. To be perfectly frank, I also don't want my wife or daughter doing things that are intrinsically very dangerous, merely because some radical who will not deal with the consequences of their own stupidity, has convinced them that 2+2=5. I'd rather they left those tasks to me or to their brothers or husbands. There will never be a "next generation" without women, so I'd say that their role in society is pretty much cemented for the foreseeable future. A high-functioning society can only come about by men and women working together, playing to their strengths, and using the strengths of the other to mitigate their weaknesses.

Yes, all of the able-bodied people living aboard a ship, tens of millions of miles from home, should all have jobs to do. Nobody should be sent to Mars who isn't at least initially able-bodied, so that would mean everyone. The ship will run much smoother with all 1,066 people aboard working together. The quality of the meals will be better, the ship will be better maintained, and our prospective Mars homesteaders will learn how to cope with the rigor of frontier life before they ever set foot on the planet. If they're not lending a hand to the crew of the ship, then they need to be training aboard the ship. The Marines we had aboard our ships weren't part of ship's company and did not participate in most shipboard evolutions, but I never saw them sitting around with their thumbs up their butts, either. An ocean-going cruise ship provides a 1 to 2 week vacation for the very wealthy. There are no 6 month vacations for 20-somethings and 30-somethings, unless they're independently wealthy. 6 months without work is called unemployment, but everyone who goes to Mars is going to do work and lots of it, or there's no point to having them there.

kbd512 · 2021-12-21 09:27:13

Another post moved...

Calliban,

Another option that both drastically reduces weight while increasing both temperature and radiation resistance, is to use BNNT fabric instead of steel. BNNT remains fairly stable when heated in an oxidizing atmosphere, up to 800C or so, unlike CNNT. By 800C, virtually all steel alloys and super alloys have become junk, strength-wise. Most of these super alloys are annealed near 800C, so that makes perfect sense. BNNT also has vastly superior ballistic properties to any steel, capable of repeatedly absorbing hits that would tear any reasonably strong steel structure apart. Some kind of stiffening structure would be required to assure that the structural rigidity was maintained, even if a compartment was compromised (lost pressurization from puncture or fire damage). That requires an internal or external skeleton of metal or composite tubing.

If most of the structure was BNNT fabric, then it would be easier for me to accept an all-up-weight, less propellant, near 5,000t. Please bear in mind that sufficient food for 1,000 people for 2 years will weigh 552,508kg (0.71kg per person per day), without any packaging mass included. That 5,000t figure also presumes that the ship does not require significant heat shielding mass. 100kg per woman is 53,300kg and 125kg per man is 66,625kg. We're already up to 672,433kg before any mass for the ship is included. Once we factor in the water required for cooking / cleaning / drinking / radiation shielding, we're going to be very near 1,000t. 250t of water is 66,050 gallons.

So I ask everyone here, does it seem at all reasonable for this ship to only weigh 1,000t?

Personally, I think not, though opinions obviously vary.

Beyond that, does it seem reasonable to allocate 96,733kg to steel coffin racks if mass margins are that tight?

Again, I think not.

Given a 5,000t dry mass / 7,000t wet mass / 5,000s Isp (pulsed fusion propulsion, which is impulsive in nature), you have ~16.5km/s of Delta-V, which is enough for a single mission using minimum energy transfers.

A 1cm thick / 2g/cm^3 BNNT fabric torus with a 25m inner radius and 31m outer radius would weigh 34,905kg (straight volume difference of 17m^3 says it's 34t, but some rounding error is involved here). Multiply by about 4, and that is the weight of a stainless or maraging steel. BNNT and steel won't provide equivalent tensile strength, though, as the BNNT fabric is much stronger. The assertion is frequently made that "perfect" CNT / BNNT would be 100X stronger than steel (I've yet to see any "perfect" megastructures), but recent actual measurements of BNNT tensile strength is 30GPa, or only 15X stronger than steel. Even at 1cm, a 3D-woven BNNT fabric would stop most small hypervelocity projectiles cold, with minimal damage. 1cm of steel may as well be paper to a hypervelocity space rock, but is worse than paper in a GCR / SPE environment.

To that 17t base hull weight, using woven BNNT fiber (NOT a composite), we must add the mass of gas impermeable PTFE restraint layers, fiber-reinforced / semi-rigid water cells (not all 250t, some of which would be stored in the center of the ship), and either an inner hull or stiffening ribs if we want to be really sure that nothing penetrates and nothing compromises the structural integrity of the torus. I would think that stiffening ribs would be the lightest solution.

What should be obvious is that the torus can be gigantic if constructed of CNT or BNNT, for very little weight. With the 20cm thick water wall, this thing still has 4,615m^3 of interior volume, or 4.33m^3 per person (just shy of 153ft^3). NASA's "team of experts" assert that we need a bare minimum of 25m^3 of habitable volume per person for long duration space flight. A pair of counter-rotating fabric donuts would only provide 1/3rd of that requirement, so we need to think about drastically increasing the volume.

We probably need to upgrade to a 640t / 50m inner radius BNNT torus. If we have a pair of them, we're still only providing 2/3rds of what NASA deems acceptable habitable volume for long duration space flight, but it's probable that we now have sufficient volume for 1,000 pax and sufficient radius to avoid nauseating them. Unfortunately, now we really do have to think about where to put our 250t of water to adequately protect them from radiation.

This is one of the best NASA articles I've found to explain the relative merit of different radiation shielding concepts in layman's terms:

Radiation Shielding By Dr. Ronald Turner

SpaceNut · 2021-12-21 09:43:08

Enjoy you day

The lifting of the parts are greatly reduced by the use of fabrics and if those things like water are brought up after its inflated we have also reduced the lifts required.

The real question for the inflatable is how many ports or air interlock can we have made into a single unit.

As such the current Bigelow units could be altered and sent with the interiors altered with little issue for use of a water wall interior for shielding serving as a backup source. Keeping the water in the outer blatter layers for the inflatable is also a means to gain shielding through use as its converted to waste.

https://en.wikipedia.org/wiki/Rotating_ … ce_station

Connecting an engine module plus tanks rather than pumping also makes it simpler to build and get to using it as it sets out on the journey by combining the exhaust plasma to creating a shield means a magnetic material is part of the exhaust or expelled into the exhaust path before it can cool.

Calliban · 2021-12-21 09:55:17

This is an excellent topic that clearly took a lot of collaborative work between a number of contributors, with Robert leading the project through a number of years. Well done indeed to all involved. I will read through the posts in detail this evening, after work.

Skimming through both this thread and the previous one; In the scale of engineering development, this project is clearly advancing towards a developed concept design. All I will say at this stage is that following completion of concept, the next stages would normally be hazard analysis and manufacturing assessment. This can be expected to take at least a few years from experience in the ship building sector. The final design, following completion of these stages and modifications, is the developed design. In theory, this is ready for manufacture. In reality, the design authority will probably still need to adjust the design according to customer (SpaceX?) requirements and it may be necessary to make minor design changes to fine tune in line with manufacturing capability of sub-contractors and cost saving requirements. It is important to have tools that can accommodate these sorts of changes, without having to go back to square one in the analysis.

Robert's decision to modularise the ship is a sensible one. It allows easier assembly in orbit of modular parts and also makes it easier to accommodate late design changes, I.e due to advances in propulsion technology. All naval manufacturing is heading the same way. It cuts down build time and cost considerably and is obviously essential if we are lifting components from Earth. There are risks in working this way. Individual design teams typically inherit responsibility for individual modules. This can create interface problems that you have to work around. It can be a real headache. You have to integrate lots of different systems into compact modules. Each system has its own unique space and geometry requirements. Each system interacts and is a hazard to other systems and to people around it. There are no slick solutions for managing this. But it has become much easier following the introduction of 3D CAD models that can show 3D arrangements. Before that design changes were often made during build. There was a lot of rework that typically increased cost, build time and introduced defects. Things are much better nowadays.

Systems engineering hazard analysis typically employs 'structured what-if' techniques. It is a qualitative assessment that examines an arrangement against a set of key words to identify hazards. Additionally, unstructured analysis is carried out by putting subject matter experts in a room with the 3D CAD model and identifying hazards that might give rise to accidents. It is mostly obvious stuff. You don't want oil containing lines less than a foot away from high voltage components that might generate arc flash. You don't want hydraulic or lube oil lines running over steam pipes, as oil soaked insulation will smolder and create a fire hazard. Fire systems engineering employs a combination of what-if and zonal hazard analysis techniques. The same is probability true of flood (or in our case, depressurisation faults). Most of the system engineering expertise relevant to naval projects will be applicable to space craft and vise versa. I have only worked in my own little specialism, but got a good view of the whole ship design process. I am grateful for those years, even if they didn't pay as well as I might have wished.

Last edited by Calliban (2021-12-21 10:22:10)

tahanson43206 · 2021-12-21 10:15:30

For kbd512 re new topic

The evolution of Large Ship from it's initial vision into multiple versions is inevitable, and I welcome and appreciate your decision to open this new line of thought.

I remain supportive of the original line as developed by RobertDyck over the past couple of Earth years, but I welcome your decision to give him some competition.

It is entirely possible even more variations of the basic idea will appear, both here in the forum and in the outside world.

The idea of building a vessel to match Mars gravity is first published here (as far as I know) but the idea itself will (or could) occur to any thoughtful person.

The idea of providing Mars Habitat atmosphere as designed by RobertDyck is a bit less obvious, but it is an idea that has momentum on it's side, so I expect most ship designers are going to adopt it as a standard, for compatibility if nothing else.

All-in-all, I think this fork of the original idea is positive for everyone.

Bravo!

(th)

kbd512 · 2021-12-21 22:45:35

tahanson43206,

1. This isn't a competition to me. I'm not looking for credit for anything, nor am I claiming any ideas as my own. Everyone else should feel free to take any good ideas I do come up with, call them their own, and then build a ship. I care infinitely more about a practical ship that actually gets built than I do about who gets credit for what. This is one way in which Robert and I differ. He's entitled to ownership over his ideas, but I think ownership of ideas frequently gets in the way of actually implementing them. I would also like to make it clear that I still support Robert Dyck's original concept. I am merely trying to propose a similar alternative with lower mass and power requirements. This thread was started as a "Come to Jesus" moment regarding the incredible mass and power requirements of his proposed ship. This one is slightly more practical. It still embodies the essence of all or most of his ideas, without getting wrapped around the axle regarding implementation details.

2. I don't care where this ultimately takes us. I want to see Robert Dyck's good ideas brought to life. Robert's large ship concept doesn't lose anything by being feasible to put into orbit with a mere handful of Starship launches, no matter what he thinks to the contrary. I suspect a ship in this weight class will cost about as much as a commercial airliner to build and launch.

3. Robert said he was still tallying up the mass for his ship and was already over 25,000t worth of dry mass. While I have no doubt that one day we'll be capable of propelling the Titanic through interplanetary space, I would like to still be counted amongst the living when the first convoy of true interplanetary transports set sail for Mars.

4. If you put enough thrust behind a refrigerator then you can make it fly, but refrigerators clearly weren't meant to fly. At first I thought this vehicle would still fall within the realm of feasibility, if not practicality, but that was before the mass estimates rolled in. We can't supply enough power and propellant at a practical cost, so something has to give. As is always the case with space flight, "what gives" is the dry mass of the vehicle.

5. Robert wants to build the Rolls Royce of interplanetary transports, and more power to him. Who doesn't want a Rolls? This alternative proposal will be a comparative Ford Fiesta. The humble Fiesta will never be as nice as the Rolls, but it'll still get the job done for a lot less money. I was in the Navy, so of course I want steel ships. However, I'm also a practical person. All sailors need ships, but steel is optional for space ships. I can definitely see space stations built from steel, but the sheer mass of steel is a mother when you have to move it.

6. I would love to have open cycle gas core nuclear thermal rockets for propulsion, but lighting one off in LEO is probably a non-starter. Here in America, or possibly in Russia, we wouldn't think twice about putting more oomph behind a rocket, but there are also other countries on this space rock we call home and those are the people who need convincing, not me. If Robert convinces all or most of the rest of the nations on planet Earth to get behind this idea, then let's do it.

The alternative propulsion systems proposed here are a combination of the following (admittedly with less pizzazz than GCNTR):

A. MagBeam for outbound transfer maneuvers (TMI / TEI)

MagBeam offloads most of the mass and power generating requirements for impulsive maneuvers to an orbital satellite / space station that supplies the input electrical power. MagBeam uses a plasma "gun" to remotely supply input power for propulsion, very similar to the beamed Microwave power concept, but with extreme beam coherence over great distances. The MagBeam spacecraft / space station stays in orbit around the planetary body and never leaves. The powered spacecraft uses the power beam to heat / ionize gas and generate a considerable amount of thrust over a very short time period measured in hours. This is the closest electric analog to an impulsive transfer that chemical or nuclear thermal propulsion provides. The MagBeam station's input power can be supplied by batteries, regenerative fuel cells, or nuclear reactors. I could care less which option is selected, so long as the station's mass remains within the realm of feasibility. What it does do is offload hundreds to thousands of tons of mass associated with the power generating equipment.

B. Electrodynamic Tethers for outbound transfer maneuvers (TMI only)

Electrodynamic tethers are very long thin wires capable of generating enormous power within Earth's electromagnetic bubble. They can be used to raise the orbits of ships or satellites over longer periods of time measured in weeks. The major advantage is that no propellant is required because the combination of solar protons and Earth's electromagnetic field supplies the input power. So long as radiation shielding remains adequate, waiting a few weeks is not a major impediment. Outside of Earth's Van Allen belts, they can still be used to collect power from the Sun.

C. M2P2 for cruise propulsion and return to Earth (TEI only)

M2P2 alone is capable of producing very high velocities over a period of 1 to 3 months, tens of kilometers per second. It does have a specific impulse attached to it, because it requires the injection of a tiny quantity of gas each day, but that Isp ranges between 50,000s and 90,000s (not a typo). However, it was intended to function best in interplanetary space, away from the electromagnetic field of Earth's Van Allen belts. M2P2 uses an electromagnetically ionized plasma field to repel solar protons, generating thrust in the process. As the craft moves away from the Sun, the electromagnetic field inflates / grows larger in size, in order to generate near-constant thrust out to the Heliopause.

Apart from electrodynamic tethers, MagBeam and M2P2 technologies use plasma trapped in a magnetic field to generate thrust. Whereas MagBeam requires a lot of input power, M2P2 requires very little power to generate considerable thrust.

kbd512 · 2021-12-21 23:44:32

SpaceNut,

I'm proposing that the ship's hull structure be brought up in 5 launches.

Launch #1 - engineering / propulsion / attitude control module, basically the rear end of the ship
Launch #2 - aft barrel section that the aft rotating inflatable habitation ring and engineering module attaches to
Launch #3 - forward barrel section the forward inflatable habitation ring attaches to
Launch #4 - aft inflatable habitation ring
Launch #5 - forward inflatable habitation ring

Launch #6 / #7 - potable water and supplies
Launches #8 / #9 / #10 / #11 / #12 - food
Launches #13 / #14 - crew members and personal belongings

The labor to construct the ship will come from ISS. The astronauts will have to take breaks from tinkering with their science experiments to supply labor to assemble / kit-out the ship. A supplemental crew head count will be provided by Dragon or Starliner or Dream Chaser or Soyuz. 3 crew members will be dedicated to assembly, kit-out, and testing for a period of about a year, alternating between running ISS and assembly tasks every 3 months to rebuild experience in orbital assembly within the astronaut / cosmonaut corps. Crews will be international in nature, so we need to fetch enough bodies from the labor pool. We will begin operations with a dozen ships or so.

Each convoy will consist of a pair of ships and a pair of robotic supply vessels carrying bulk commodities such as metals, foodstuffs, and tanks of supplemental liquid consumables to include H2O / LOX / LN2 / LCH4 / LNH3 / etc. The supply vessels will only be engineering modules and attached cargo, rather than rotating habitation modules. This is a one-way trip, so the colonists and supplies will arrive in disposable landers that will then be repurposed or stripped for use in build-out of the colony. For example, the metals from the engines might be melted down for producing heat exchangers, or to build pressure vessels for nuclear reactors. The propellant tanks might see a second life as fuel tanks for vehicles, or they might be repurposed as storage containers for hot water or liquefied gases.

As you can see, even this 2,500t ship concept (1/10th to 1/20th scale of what Robert proposes) requires at least a dozen Starship launches to construct and kit out for its maiden voyage. It's still a major undertaking that won't be cheap. It'll be six times the weight of ISS. I'd say that's big enough for what we're going to use it for.

kbd512 · 2021-12-22 01:08:55

Calliban,

The real genius of the various ideas that Robert came up with was bio-regenerative life support, and it seems that NASA is already doing quite a bit of applied research into those concepts, including using bacteria and algae to supply foodstuffs for the crew. The "Water Wall" paper I posted a link to shows that NASA has finally "taken a shine" to some of his ideas. To enable space flight for the masses and associated space colonization, that sort of technology will become increasingly important over the coming decades. That was a very forward-thinking idea on Robert's part.

Calliban · 2021-12-22 11:36:04

I will be a bit more scarce on this board over the next two months, as I need to put the time in to developing the propulsion system for the large ship.

In summary, what I am proposing is an inertial confinement fusion-fission hybrid concept. This is quite similar to the mini-mag orion. In that case, small quantities of fissile material were compressed by z-pinch in a liner, reaching critical conditions. The extreme compression and density achievable in a z-pinch, reduces critical mass far beneath what would normally be achievable in a conventional fission bomb. The resulting energy release can be fully enclosed within a magnetic nozzle, which provides far more propulsive work per unit fissile material than a conventional bomb driven Orion.

What I am proposing is similar, but the fissile core is surrounded by a shell of lithium deuteride. As the pellet compresses, it serves as a neutron reflector for the fissile core, which is a raison of fissile material at the centre of the pellet. Because the fissile core is so small, any fission products generated within the core, will escape into the surrounding lithium deuteride. As the fission products slow down within the medium, they generate high energy ions, some of which then undergo fusion. The fusion reactions generate neutrons. The slowing down length of fission products in the highly compressed shell will be about 1E-6m. About half of the generated neutrons will therefore enter the core, where they will produce more fission, generating more fission products, creating more fusion events in the shell and so on. This close coupling between the fissile and fusion stages, and the neutron reflection provided by the compressed shell, allows critical mass to be reduced far beneath the limits of mini-mag orion. Ideally, we want fusion to contribute all of the energy released and for no radioactivity to be generated in the form of fission products. In reality, fission in the core will generate a hot spot at the centre of the compressed pellet, giving rise to a detonation wave when the pellet is sufficiently compressed. The goal is to get the most propulsive energy possible, with minimum generation of fission products. Ideally, we want a mini-mag orion with ISP in the 10,000 range, with T/W 1g> and clean enough to use in Earth's atmosphere. If we can do that, then the large ship can take off and land on Earth and Mars and achieve a round trip from Earth surface, to Mars and back to Earth, with a fuel and propellant mass fraction of around 10%. That would make travel to Mars as cheap as a travel on an ocean liner. Puts me in mind of a Star Destroyer, which was primarily a ship of space, but could land on planets if necessary.

This is a task that I will not be able to finish, as modelling the coupling between the imploding nuclear materials, is beyond my capabilities. I am going to see how far I can get with it. I can at the very least explain the concept qualitatively and suggest further experiment.

Such a coupled hybrid system could function as a surface power source on Mars as well. If we can use very small amounts of fissile materials to trigger nuclear fusion in a space drive, then we can build compact fusion reactors as well. If this can be demonstrated in concept, then SpaceX will need neither a solar plant or fission reactor to power propellant production in early missions. The leap can be made directly to fusion. This will obviously revolutionise power production on Earth as well.

Last edited by Calliban (2021-12-22 11:49:47)

kbd512 · 2021-12-22 11:48:57

Calliban,

A steel ship would be ideal, as I've previously stated many times, but it's becoming increasingly clear that it also requires power and propulsion well beyond the limits of what we're presently pursuing. I am very interested in what you come up with, as it will determine if we can feasibly propel a steel ship of approximately the same gross tonnage as the Titanic through interplanetary space. If physics won't allow us to ride in the Rolls Royce (50,000t) of interplanetary transports, then I'd be interested in whether or not you think M2P2 and MagBeam could provide a practical alternative for the Ford Fiesta of interplanetary transports (2,500t).

Calliban · 2021-12-22 12:15:53

kbd512 wrote:

Calliban,
A steel ship would be ideal, as I've previously stated many times, but it's becoming increasingly clear that it also requires power and propulsion well beyond the limits of what we're presently pursuing. I am very interested in what you come up with, as it will determine if we can feasibly propel a steel ship of approximately the same gross tonnage as the Titanic through interplanetary space. If physics won't allow us to ride in the Rolls Royce (50,000t) of interplanetary transports, then I'd be interested in whether or not you think M2P2 and MagBeam could provide a practical alternative for the Ford Fiesta of interplanetary transports (2,500t).

There are lots of limitations that may end up derailing such a concept. For one thing, accelerating a 50,000 tonne ship against Earth gravity at 1g (2g effective acceleration force), requires 1000MN of thrust. That is a huge point loading. The shock wave from the drive plume will have a lethal range comparable to a small a-bomb. The thermal radiation from the plume will ignite fabrics and cause burns many miles away. And even if the plume is not especially radioactive, it will be hot enough to emit x-rays. Once in space the environmental impact doesn't stop. The plume will pump the magnetosphere with high energy ions. This could damage satellites and imperil astronauts that aren't properly shielded. Any decent performing space drive is a weapon of mass destruction in the hands of the unscrupulous. The amount of power it entails renders that inevitable.

The bremsstrahlung and neutron emissions from the plasma, will irradiate the inside of the engine at power levels of 100s GW. Removing that much heat is beyond what is achievable with conductive cooling into cooling pipes. We must cool those components by bleeding pressurised propellant through them and into the engine chamber. Suffice to say, if we build a fusion powered Titanic that can take off from Earth, it will be the biggest engineering challenge that mankind has ever taken on. The drive will be visible to the naked eye many millions of miles out in space. The power of the drive will exceed total energy consumption of all mankind on planet Earth when it is switched on. So basically, wherever this thing takes off and lands, it will need an exclusion zone several miles in radius. No small ask for any nation.

Last edited by Calliban (2021-12-22 12:33:04)

kbd512 · 2021-12-22 12:31:27

Calliban,

I was thinking more along the lines of orbit-to-orbit transport. Reentry itself is problematic due to the extreme heating and aero loads placed upon all reentry vehicles. I don't think a 2g acceleration is required or even desirable for such a large ship, even without that minor detail of "a lethal blast radius comparable to a small atom bomb". Maybe we could shoot for 50MN (still equivalent to 28 Raptor engines at full power) for 1/10th g acceleration instead? That's still an impulsive transfer.

RobertDyck · 2021-12-22 13:59:39

Congratulations. I want to stick to my design in my discussion thread, and try to bring my vision to reality. That does not prevent others from design a different spacecraft. I am glad you started a separate thread to explore and develop your design. I wish you well. Good luck! Ideally, both spacecraft will meet at Mars. To quote a slogan of the "Case for Mars" conferences of the 1990s, before the Mars Society was founded: "On to Mars!"

SpaceNut · 2021-12-22 14:29:26

This looks like its part of mission 1 delivery to orbit which is a hard floor item to build from post 10.

kbd512 wrote:

Once the payloads are in space, nuclear fusion achieved with power supplied by small fission reactors is the way to go. We already achieve fusion each time we try it, we just can't make the energy conversion efficient enough to obtain a net gain in terms of electrical power output from the process. The very best part of this in-space propulsion scheme is that it involves doing things we already know how to do and are 100% successful in doing, namely making super heated plasma from fusion, losing containment of the plasma- this time intentionally, and never generating a single watt of electrical power- just pure thrust.

Of course that power system and shield is what will make the journey possible but it sets the ground for everything else.

kbd512 wrote:

Here's what we absolutely must have, in terms of technology development:
1. utterly reliable closed loop or nearly closed loop long duration life support
2. high thrust / high Isp rocket engines for in-space propulsion
3. artificial gravity for long duration interplanetary transits
4. GCR and SPE / CME radiation mitigation technologies, such as the mini-magnetosphere you mentioned
5. nuclear fission reactors to prove tens of megawatts of electrical power to fusion-driven rocket engines and surface colonies
ISRU technologies were not included because no missions are practical without them, so you can either make your own rocket fuel to return or you're not going.
Nice to have (will rapidly become mandatory during colonization, though):
1. MCP space suits
2. nuclear thermal rocket engines (falls between chemical and nuclear fusion rocket engines in terms of thrust-to-weight)
3. high speed laser-based deep space data relays and GPS in orbit around Mars and solar power satellites that can beam power to the surface on-demand
4. novel construction techniques that maximize the use of local resources for habitat construction
5. aeroponics or hydroponics to grow food without soil

SpaceNut · 2021-12-22 19:16:30

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

The clothes washer was something RobertDyck and I talked about for how to do one for zero G use and it would work just fine even on the surface of mars. Of course its a combo unit...

Will see if I can find the topic.

Found it

Laundry

GW Johnson · 2021-12-23 17:43:44

Rob & Kbd512:

I sent you some rocket equation propulsion stuff -- check your emails. I also sent you the spreadsheet with which I did it, so you can go and play, yourselves. It's just ballpark, one should never infer predicted performance from something so crude. But it can readily identify relative trends. Just something with which to select a couple of likely propulsion candidates.

GW

kbd512 · 2021-12-23 21:21:49

GW,

Thank you, sir. I'll take a look.

tahanson43206 · 2021-12-26 20:41:11

For kbd512 ...

A military organization might be interested in your ideas for a lightweight, counter-rotating personnel transport vehicle.

RobertDyck has a standing claim to the civilian passenger trade.

I am hoping you will continue to develop your ideas and to provide some 2D drawings at a minimum to show what you are seeing in your mind's eye.

The idea of delivering a variable gravity (and a variable spin rate) is sure to be of interest to a number of Nations, as well as groups within Nations.

Drawings will help to build support for the ideas you develop.

(th)

kbd512 · 2021-12-27 19:05:50

tahanson43206,

I'm not really interested in weaponizing space. My only real disagreement with Robert over the military is the utility of using the military's organizational structure, training, and operational doctrines to assure the completion of the ship's mission and the survival of her crew. In this case, the mission is colonization of another planet. That cannot be done if the crew does not survive the journey, or the crew is not organized, physically fit, and mentally prepared. Rather than fixate on some "universal truth" about the differences between the military and civilian approaches to organization and problem solving, I find "general truths" more useful.

After sufficient training, the military generally performs tasks requiring swift and organized action better than people who have not been so-trained / indoctrinated. My experience boarding a commercial airliner with 200 other people in the military is that it takes less than 5 minutes. In the civilian world, 30 minutes later they're still milling around. If it was a military cargo plane, then it would take longer to lower and raise the ramp than it would for us to board. When something goes wrong in space, it typically happens really fast and is insanely dangerous, so appropriate responses need to be as fast and second-nature as breathing.

Your personal job description is also irrelevant if the ship is sinking while you're on it. The ocean doesn't distinguish between ship's cook and ship's Captain. Space can't tell the difference, either. Arguments over what could have been done differently are best explored during a more appropriate time. When command structures are adhered to, that sort of problem is nearly non-existent. Whether civilians are all 10 times smarter than anyone in the military because civilians all get to decide when and how they will respond, is utterly meaningless if they all die while debating who needs to batten down a hatch. Most civilians are clearly capable of learning how to coordinate their actions, because all military personnel were once civilians, but without the training regimen the immediate responses do not magically materialize.

Following any serious casualties or contentious issues, all of the officers and chiefs I worked for would ask their subordinates' input about how to avoid or rectify future problems. The notion that serious problems or disagreements would simply be ignored, due to some vague notion that the hierarchical command structure makes such issues irrelevant to those at the top, was not what I personally witnessed. There have been instances of individual commands failing under poor leadership, but while those people would frequently be promoted in the civilian world, in the military world the command leadership is relieved of command and those responsible for oversight are also frequently relieved. Many civilian ships function in a remarkably similar manner for the same reasons. Hierarchy has been established inside and outside of the uniformed services for the express purpose of absolute clarity when carrying out orders.

Unfortunately, space is an immediate lethal and entirely unforgiving operating environment that requires detailed knowledge, rigorous training, and swift but organized responses to survive after something goes wrong. There simply cannot be any debates about what to do, who does what, etc, because there isn't enough time for that process to play out. That's where military-style command structure, training, and doctrine truly shines. We have training-based responses to survive immediately lethal events and crews have been conditioned through training to respond fast enough to be effective.

We don't need a specific "rank structure" per se because this is not the military, but we do need assigned roles (CO / XO / OPSO / COMMO / EO / CDO / etc) and a clearly defined chain of command for purposes of passing information to those who need to know and decide how to solve a problem. The funny thing is that nearly all civilian owned businesses have a de-facto rank structure, they simply don't call it that, as if that somehow changes what it actually is while you're working there.

Whenever we go to general quarters, you can't see anyone's rank insignia because their collars are entirely hidden, but everyone knows their role from training. I knew nearly everyone from my damage control locker by sight / voice / name, my tools and equipment were always waiting for me in the same place after I arrived, and other than the odd one-liner from the Damage Control Officer (DCO), I knew where to go / what to do / what information to pass back to my DCO based upon what I found. That kind of knowledge and response only comes from rigorous and continuous training (at times we conducted these drills up to once per day, always unannounced and at random times of the day), trust in each other from shared experience (good and bad), and faith in the abilities of your crew from close personal observation.

The cross-training was also very important since personnel came and went, and were injured (unfortunately, this happened with some regularity, often with ghastly results- it could get messy to say the least) or sickened (food-borne illness, mostly, and this happened to me twice- you look like warmed-over death for about a day) or killed (very few, thankfully, but it generally happened once or twice per cruise- electricity / ejection seats and other explosive devices / falling / drowning / heart attack was common amongst those nearing retirement- one of many reasons I left after seeing the number of Chiefs who died at their post or died immediately after leaving, kinda like Police). Everyone was required to know and demonstrate basic first-aid (I eventually had to use what I was taught), pipe patching, firefighting, NBC contamination response and cleanup (this was actually kind of interesting and "fun" in its own dark little way), passing of instructions over sound powered phones, how to make standardized log entries (we wrote everything down on paper in logbooks passed from watch-to-watch), etc.

tahanson43206 · 2021-12-27 19:27:26

For kbd512 re new topic ...

A military transport does not equate to "weaponization" of space....

It simply means you have provided a way for Space Force to move personnel from one duty station to another.

The sooner you can find something to work on that is not directly competitive with RobertDyck, the better for everyone.

I am offering the military transport option as an arena that is directly useful to an agency of the US Government, and therefore a potential customer with deep pockets.

RobertDyck has been on a course to design a civilian passenger vessel since 2019-09-03 07:07:42

He has held a steady course throughout that entire period, and I am counting upon his steady hand at the wheel as we approach March 12th.

On the other hand, you have very recently decided to embark upon a similar venture, with distinct differences that should be interesting for observers to follow, and for your prospective customer(s) to appreciate.

When you have two years of steady progress in the forum archive, you should be ready to give a talk on your design.

I'm hoping the posts in this topic will be highly technical in nature, and not political discussions that have little or nothing to do with the topic itself. We have chat topics for politics, and I note that you've had a chance to contribute there from time to time.

(th)

SpaceNut · 2021-12-27 19:35:58

The current Nasa Astronauts are selected by the process that Kbd512 has in mind unlike that of space x or Bezos both which are giving a small amount of training too. After that they are not put through any program to give there mind the muscle memory of how to act under conditions that they might face. They are not given the training on how something works let alone the knowledge on how to fix it.

Here is what most think of for a counter rotating space vehicle but this takes quite a while to build on orbit.
720?cb=20091214012911

Inflatable technology: using flexible materials to make large structures

ANALYSES OF A ROTATING ADVANCED-TECHNOLOGY SPACE STATION FOR THE YEAR 2025

How Inflatable Spacecraft Will Work

https://patents.google.com/patent/US4730797
Inflatable core orbital construction method and space station

http://www.artificial-gravity.com/Artif … 201704.pdf

tahanson43206 · 2021-12-27 21:25:41

For SpaceNut re #24 .... thanks in particular for the link to the NASA torus study. I've just scanned it enough to know that it contains a substantial amount of guidance for any of the Large Ship concepts under discussion these days. The paper was from 1988, but I note that even back then they were thinking about fiber optic communications.

SearchTerm:torus NASA 1988 study see link found by SpaceNut

(th)

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