Tall Ships and Trading Posts: Economics and MacGuffinite

Apologies for such a long pause between post, RocketFans, but I have had an appalling number of Doctor's appointments in the last week.  Next week is just as bad, but that doesn't mean I can't squeeze in a post about our lovely Tall Ships in between long waits without wi-fi.

 

My week.

Anyways, to return to the topic at hand, I have played with the specs of my Tall Ships and Spacecoaches a little bit more, in order to get numbers I like better.  Mainly, I've manipulated mass ratios, altered the number of thrusters, and other minor tweeks in order to get designs I, as a writer, would like for an interplanetary wagon train to Mars:


Tall Ship with Star Destroyer for scale.  Just to put thing into perspective...

Tall Ship:
Dry Mass: 2164 tons
Wet Mass: 6656 tons
Mass Ratio: 4
Delta V: 13600 m/s
Acceleration: 0.005 m/s^2
Travel Time to Mars: 7.1 Months

Spacecoach:
Dry Mass: 794 tons
Wet Mass: 3176 tons
Mass Ratio: 4
Delta V: 13600 m/s
Acceleration: 0.007 m/s^2
Travel Time to Mars: 13.6 Months

Yes, the Spacecoaches take twice as long to travel despite having a higher acceleration.  These are just basic figures; the burn duration on the Tall Ship, for example, is almost three times that of the Spacecoach.  I justify the excess this way:  The Tall Ships trim their burns to keep pace with the Spacecoaches, and use the extra propellant for emergency burns, space taxi service from the fleet to the showboat, and emergency remassing of damaged craft.

They are perfect for my needs.  We have a wagon train to Mars, that will get there in a bit over a year, allowing for stories in SPAAACE! about life in a constellation to Mars and whatnot, and having a central Tall Ship that is the center of all the action, like a Miss Kitty's in the Dodge City of space. 

But. I am a writer of Hard science fiction, and therefore need more justification for my spacecraft designs that "it fits the story I want to tell"  Let's all remember Ray's Rule of Science Fiction:  "Soft Science Fiction tries to make technology fit the imagination, and Hard Science Fiction tries to imagine what fits the technology."  So, If I want to keep my Hard SF street cred, I must justify such robust spacecraft in the hands of middle-class starry-eyed pioneers who sold off their meager assets to Go To Mars.  If you'll bear with me, I'll provide just such a justification, and as a bonus give you those L5 colonies they talked about in the 70s free of charge.

Okay, as a first step in our journey to make Tall Ships realistic, let's put them into context by reviewing our basic assumptions:

1. The cost of natural gas from Saturn's moon Titan is less than the cost of oil drilling on Earth, when you factor in the cost of wars over oil bearing territory.
2. A future war between China and the United States will result in Kessler's Syndrome from the  destruction of the US satellite network.
3. Nuclear Pulse Propulsion vehicles will be the best equipped to go into space and establish a manned communications network of heavily armored space stations.
4. A NPP Spacecraft has enough Delta V to go to Saturn.
5. An NPP expedition will be dispatched to Titan by nations that cannot afford to fight for oil sands but can afford a spacecraft.
6.Once Kessler's Syndrome thins out enough to allow regular space travel, there will be a demand for it from the general public.

That last is an assumption based on the idea that we really want what we can't have.  This seems like a decent bet - just look at the current furor over the defunding of the commercial crew program.

So, how do we translate those assumptions into a wagon train to Mars?

First of all, the cost of the spacecraft must be reasonable.  The most likely method of obtaining a reasonably priced spacecraft, for my money, is to obtain them second-hand.  There's ample precedent for this; the 747, $300 million per aircraft new, goes for about the cost of a new Ferrari right now.  At that kind of price schedule, a family could easily afford to replace their house with a Spacecoach and fly off to Mars.  Unfortunately, In order to have Spacecoaches' price drop as dramatically as the 747, They would have to make as many Spacecoaches as Boeing did the 747.  Optimist that I am, I don't see the Martian Run ever needing that many Spacecoaches.

So I consulted the numbers for my two ships, both written on their own index cards, hoping for inspiration.  I thought about their Delta V, they could go all the way to Ceres if you had the patience.  I figure the demand for single-family spacecraft to the Belt will be even less than the same to Mars, so that was no help.  Next, I concentrated on the engine type I chose, the Microwave Electrical Thruster.  I love these engines!  They are perfect for the mission of a Spacecoach - no moving parts, the ability to double as mining drills, and an absurdly small mass flow.  Seriously, the mass flow for a 400 engine array is only one kilo per second - an infinitesimal 2.5 grams per thruster.  I had to check these numbers more than once before I believed them.  Because the output is low pressure steam, not liquid water, the entire array can get away with small mass flows.  With the propellant mass of the modest Spacecoach design 2.3 million kilos, you can have a burn duration of over a million seconds before flip-and-brake.  That's a burn for days...

That's when I realized, for a trip to Mars the Spacecoach may use a long, slow burn, but for a trip to the Moon, it would be a constant boost rocket.

The Bachristochrone Duration for a trip from LEO to Luna's orbit at the Spacecoach's acceleration is only 414,039 seconds - well under half the maximum burn duration of our example. Our example also has a massive payload capacity, as a pioneer's wagon, so we can convert some into passenger accommodation. So, the Spacecoaches I'll use for my theoretical trips to Mars were originally meant Luna Express ships, carrying passengers cheaply into lunar orbit.

As cool as a second-hand Lunar Express sounds, we're only half-way done, RocketFans.  We've made our ships economical, but only if there's something really important in Lunar orbit that requires a substantial human presence.  In other words, we need MacGuffinite.

Remember when I said you could have the L5 colonies of old as a bonus?  I meant it.  If you followed the link above, then you may have noticed that "Petroleum Mining" is already listed.  See, the megatons of Titanian methane have to end up somewhere. The most logical place would be the two stable LaGrange points in lunar orbit, because anything at those points will stay there until you're good and ready to go fetch them.  You could try to put the methane shipments directly into Earth orbit, but after having suffered through Kessler's Syndrome once,  I doubt anyone will be willing to try.  So that's the "really important stuff in lunar orbit" part.

 And while Saturn is far enough away to be nearly imaginary to some people, you can see the Moon, and just knowing that all the oil you would ever need is right there will be more than enough incentive to go get it.  But not everyone will want to pay the Titan Oil Co. for the privilege of getting orbital oil.  There will be nations that just want to take it. Which means the oil will be defended.  There will be nations trying to sabotage the oil recovery of their rivals; they must be stopped. The powers that be on Terra that stand to lose billions as their petroleum becomes too expensive to compete may also try to interfere. And the UN, whose Security Council has two of the original sponsors of Titan Oil as members, will be on hand to make sure everyone plays nice.

That's the "substantial human presence" part.

So Spacecoaches were the cheap express ships to L5 and Luna, and Tall Ships were the overpowered, over remassed versions on hand for search and rescue, mass transits and charters.  As power stations were built to support the colonies, beam-riders replaced the gigantic solar sailers, which became less economical to run. These were bought up second-hand by settlers moving rimward, toward Cape Dread, Mars, and the beyond.  With colonies from L5 to around Saturn already, anything in between seems possible.

 

Tall Ships and Trading Posts: Tall Ships verses Spacecoaches

Welcome back, RocketFans, to another installment of Tall Ships and Trading Posts.  This time we're dealing with the specific design issues of Spacecoaches and Tall Ships, and what they are meant to do.

First of all, you may have noticed I wrote Spacecoaches and Tall Ships.  I'm beginning to see these as two different types of solar electric spacecraft.  Just as you have Piper Cubs or Lears on one end of the aviation spectrum, with A380s and 787s on the other, there will be "small" Spacecoaches for Ma and Pa immigrants and larger Tall Ships for commercial purposes.

In SPAAAAAAACE!

"Small" - bit of a misnomer, as the engines and solar sail systems must be of a certain size to work at all.  I've been working on the larger Tall Ship version for the time being, and the numbers are humbling.  It will take 1200 MET units, arranged in a 900 square meter array to push the habs, propellant and eight hundred thousand square meters of thin solar film, carbon composite masts and yardarms, and automated rigging for same.  These  Solar Sailers have masts that are kilometers long, with hab sections that are almost too small to see when the Ships are shown in scale.

"But Ray", I hear no one ask, "if the number of passengers is smaller, and the payload is smaller, why can't the sails and engines be smaller?"  Ah, my hypothetical straw man, you must understand that in this case, it is not about payload, or even about mass.  It is about travel time.  If you make a smaller MET array, the thrust is lower, therefore the acceleration is lower, therefore the travel time is longer.

But still, lets look at some numbers.  Consider the following a real-time look at the creative process, meaning I'm making it up as I go along.

A full-sized Tall Ship has a MET array that pumps out 48000N of thrust and takes 240 Mw of electricity to run.  In order to power that system in the orbit of Mars, and assuming a SFnal PV efficiency of 50%, you'll need about 800,000 square meters of sail. That will be arranged on two masts, each a kilometer long, and about four hundred meters wide.  With all the stuff I mentioned above in terms of mast and rigging, that's about 900 tons for the power train.  You'll need 3000  tons of propellant, but that's okay, because it's water and can be drunk, bathed in, flushed, then used as propellant in a model of combined utility.  Habitats run you 270 tons, payload about seventy-two for a two-year mission.  This Tall Ship is more like Rick Robinson's gossamer winged spacecraft, with about 36 passengers and crew, two big habs, and a 400-ton lander/ transfer craft.

Also in SPAAAAACE!

A more conventional Spacecoach design will lose the lander, have a hab suitable for about six or so, cargo for a family of pioneers, and that's about it.  If we try to quarter the power train, we get 400 METs, 60 Mw of power, 12000, and a sail array 200,000 square meters.  That would be a pair of masts about five hundred meters by two hundred along the yardarms.  But, the mass will still be 450 tons, because while you quarter the area, you can only halve the mass. Still, try a thousand tons of water propellant, and habs at only 135 tons  you'll keep the same payload reqruirements, because these folks are moving to stay.

So, Tall Ship: Total "wet" Mass of 4672 Tons, and a Mass Ratio of 2.8 (wow!).  With a Delta V of 10.1 kps.  The Space coach will have a wet mass of 1657 tons, a mass ratio of  2.5 and a Delta V of 8.9 kps.  So our Spacecoach has shorter legs than a Tall Ship, but not overly so - especially with such a significant reduction in cost (assuming you measure cost by x-thousand dollars a ton).

So now we can figure travel time. All the current figures assume enough supplies for a two year mission, so if the Spacecoach can't make it to it's destination in that time, you have a problem.  Tall Ships are golden - they accelerate at a blistering 0.01 m/s.  They also have a long burn duration, on the order of four days (750000 seconds) and can zoom out to Mars in 16 months.  That may sound slow, but you can make the trip in gravity, with showers everyday, so it ain't all bad.

Spacecoaches, however, have the following numbers:  Acceleration is only 0.007m/s, so they are slower and their burn durations is only a quarter of a million seconds (69 hours) before coast-and-flip.  The average velocity will also be only be half that of a Tall Ship. With those numbers, it will take our Spacecoach thirty-three months to travel to Mars.  Having enough supplies is not a problem, fortunately, because we kept the 72 ton payload of the Tall Ship.  It will mean that you can carry less pioneer stuff, however...

But how much do you need?  Look at your ship:  You have enough solar sails to run your hab's power systems and your propulsion.  Another thing, your propulsion system doubles as a mining system, with the MET thrusters making handy drills on the surface of, say, Deimos or Mars herself.  The habs you already live in?  They have structure, bracing, and plumbing for use in gravity already.  So it sounds to me, for the cost of an aerobraking transport to the surface that the folks at Cape Dread would be happy to charge you for, you could turn that Spacecoach from a slow boat from Terra to a instant homestead/mining outpost.  Convenient.

These numbers are very much back-of-the-envelope, so take them with a grain of salt.  What the number do show is that you can have small slow Spacecoaches for individual families that cost less and provide an instant homestead on the other side.  You can also have larger commercial Tall Ships that economically yet quickly ferry dozens of people from here to the Red Planet.  And what's more, these numbers are scaleable - you can add more cargo to a Tall Ship if you don't mind going slower, and you can get a Spacecoach to go faster with the addition of more METs and studding sails on the existing mast.

What I'd like to have is Spacecoaches and Tall Ships move at closer to the same travel times. I have definate ideas brewing in my fevered brain, and they involve not only these majestic sail ships of space, but their successors, Microwave beam-riders. Those  however, are a topic for another post. 

Of Tall Ships and Trading Posts: Setting the Stage...

One of the most important design aspects when trying to create a plausible Hard SFnal space craft is context.  When every gram counts, and performance has to reach into the theoretical just to be possible, you're not going to design a spacecraft with more....anything than necessary.  It would be nice to have a starship that only needed to be told to "thattaway" and let you cruise at the speed of plot until you find your next adventure.

But in real life, or at least the approximation used for Hard SF, you're lucky if the cold equations let you make it to your destination with enough life support, and luckier still if the hot equations let you do so without melting in your own waste heat.

So. Context...

Starting with the future history I began discussing last time, we have a war between China and 'Merrica over oil sometime in the next twenty years.  Because China invested in cruise missiles, the world's largest Air Force, and ASATS instead of Carriers and other weapons designed to win WWII, they destroy the US satellite system and Navy surface fleet in relatively short order. This is a wake-up call for "the greatest nation on Earth" that leads to separatist movements as the Federal government in the US loses what little credibility and authority it still had.

Even better, the destruction of all of America's satellite constellations is the tipping point for a nasty case of Kessler's Syndrome, so now international communications, Internet and even television is knocked out.  Oh, and weather prediction, so the increasingly frisky weather causes much more loss of life than it does now.

Meanwhile, across the pond, the UK and France decide to take matters into their own national hands in regards to the oil crisis.  Since even together they can't fight China over the dregs of Middle Eastern oil, they decide to use their nuclear arsenal to launch heavily armored Orions into orbit, which can weather the debris storms by virtue of not having to worry about mass.  By selling space on said Orion stations, they can earn money and influence to become major players again, and also enough to not get into trouble with the UN.  In fact, with the world pretty much pissed at China and the US, They are invited to retire from the UN Security Council and their Veto powers are revoked.

That's just the beginning - with the worlds atomic powers giving the ESA their nukes in exchange for payloads on their Orions, A mission is sent to Saturn with the goal of starting an unending stream of megaton oil tanker from Titan to Earth.  It's an enormous gamble, but the investment isn't as bad it could have been  - Orions are in regular, if not frequent use at this point in time, and outfitting a ten kiloton trans-chronian is just a matter of packing enough biscuits, bombs and barrels for the oil.

It will take about twenty years to get the steam of oil from Saturn to Earth.  Once started, it come in regular like - which is good, because earth is just about dry.  All those Orion flights have heated things up a bit as well - the sea levels have displaced or drowned about a billion of the world's nine billion people.   Russia and China are at one an other's throats, but China lack's the resources (after taking out America) to mount an offensive, and Russia lacks the resources to sustain one.  They just...grind away, losing their military power more and more each year.

As for the US, if occurs to the rising military powers of  Mexica and South America that we have quite a bit of oil in our national territory.  Karma is an ugly thing.  What's left of CONUS is not the United States of America.  It's maybe three or four  smaller, weaker countries that dislike one another as much if not more than their neighbors to the south.

By the time the first mega-tankers with their endless supply of methane reach Terra, the Kessler syndrome has just about faded out.  You know how people really really want something when they're told they can't have it? That's how the Terran public feels about space.  And with the enormous amounts of methane making for a petroleum boom that makes frakking look like a backyard well, there's enough money in economy to invest in things like solar power stations in space, and laser launch facilities.  People lived through some lean times, not unlike the period between 1930 and 1950, and they want reliable power and lots of plastic feedstocks.

I didn't have a picture...

It's the late 21st century.  Orions go to Saturn.  Oil goes to Terra, and Mars - the idea of terraforming the red planet is a lot less ridiculous when you have an unlimited amount of greenhouse gasses and fertilizer.  Cape Dread is become a going concern.  Ceres is as well, and planes to visit Jupiter, just to round things out are in the making.
More than anything though, people want into space.  Maybe for a suborbital hop, just to say they did it, maybe for longer.  Space infrastructure builds up.  The numbers I put up for a single Gateway station are about right for the amount of cargo going up into space at this point.  There's a veritable monsoon of oil coming down in ships like the Liberty Bells I've shown here before.  And with interst in older ideas like the Spacecoach leading to actual corporate funding and construction, the Solar System on the verge of it's first bona fide diaspora.

The Kessler Era has ended.  The Conjunction War won't start for another hundred years.

It's Age of the Tall Ship.   

Of Tall Ships and Trading Posts

You know what, RocketFans?  It's been entirely to long since we've had some honest-to-Heinlein speculative worldbuilding around this blog.  Let's fix that, shall we?

So I was perusing that clearing house for all things Hard SF, Atomic Rockets, and came across a wonderful design for a cheap, reusable interplanetary spacecraft with the romantic name of Spacecoach.  It's an exciting idea - the ship's structure is primarily water ice and kevlar strands, a mixture known as Pykrete.  The habs are inflatable, the engines double as mining drils, and the propellant is grey water from the crew's life support.  It's a genius mixture of innovation, simplicity, and safety that would allow the average mortal to reach for the stars.

Part of the design that drew my curiousity was the large solar arrays needed to power the Microwave Electrical Thrusters.  Nothing wrong with solar - its the oldest and most mature form of In-Situ Resource Utilization used in orbit and, as they say, the sun is always shining in space.  The thing that concerned me was that the sun may always be shining, but its only half as strong around Mars, and a mere 4% of it's NEO intensity once you reach the Jovian system.  The excellent nano-fic Spaceward Ho! suggests that microwave rectennae could be utilized beyond Mars, but the price of such a system is dependance (and financial obligation) to whomever turns on the microwave beam.

Call me a recluse, but I didn't like that.

So I posed a question to the modern virtual agora that is Google+, in which I proposed the use of regenerative fuel cells to make the Spacecoach energy independant past Mars.  My reasoning was that 4% power on the solar array may not be enough to power the ship, but it could power the regenerative cycle on a fuel cell.  Since fuel cells crack water for hydrogen and oxygen, and the Spacecoach is pretty much made of water...you see my logic, right?

Alas, Robert Davidoff, who is to the untrained writer/artist like myself what the Logisician is to Generals (Read the first entry in Logistic Quotations and know that it's a compliment) points out that you can add hectares of solar arrays for the same mass that the regenerative fuel cell and enough solar panels to run them.  I wondered if it would make sense to stow the extra panels when in the inner system, or just leave them out all the time.  Like modern Muse of Hard SF, Rob posted a quote that seved as great inspiration:

"Well, there's the potential justification of protection from micrometeors and other debris, like you said, plus just general rule of cool". Maybe something like a roller-furling jib, with a fixed "boom" and retracting flexible solar array "sail" would do? The boom could be very light, and rigged inboard when not necessary to avoid docking issues, and it'd be easy to swing it out and unfurl the array to and start making watts when necessary."

...Masts?  Jibs? SAILS!?  That sounds like... a TALL SHIP!

So my fevered brain had to design one, of course.

Here we see her shaping an orbit from Cape Dread to points beyond in the Belt.  There's a family aboard, who will use their ship's MET thruster as a mining drill to tease volatiles out of the cold rock.  They'll trade surplus water for phosphorus and other necessities. I may be hard life, but there's freedom and opportunities in the Black.

See?  Inspired!

But I'm not just interested in making fun art pieces out of these ideas; I've been crunching numbers just as feverishly as I have been drawing pictures and sculpting pixels.  And while it is only a matter of many maths to come up with the essential specs of such a spacecraft, justifying its existance is another matter entirely.  Sure, you could build one, but who's gonna buy it?  It can go from here to Marse, or even Ceres, maybe, but what will it do once it gets there?

In future posts we will start seeing what this Tall Ship can do, and why it should do it.