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.   

Signed Books for Sale!

Good books, too!  Alister Young, writer extraordinaire and my inspiration behind the idea of doing Nano-fic, has two anthologies from his Eldreverse for sale on Amazon here and here.  I mention this because for a limited time, he is offering to sign copies of said books for only the Amazon price plus additional postage.  You can leave a comment at the links above if interested.

I've read both of these books, and highly recommend them.   Alister has received the distinctive Atomic Rockets Seal of Approval, so you know that the stuff is excellent, but allow me to put my additional $0.02 worth on top of that.  One of the stories, Cosmos and Ethos, was one of the most inspiring things I've read this decade.  Considering this decade is half-over, that's saying something.

Anyway, it's good stuff.  You should take a look.  Pledge to Alister's Patreon, even.