Comments on Rocketpunk Manifesto: Let's Get Around

Good Afternoon!!! www.rocketpunk-manifesto.com is ...

2009-12-11T16:38:53.055-08:00

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There are plenty of reasons, though not quite '...

2009-07-02T17:20:27.148-07:00

There are plenty of reasons, though not quite 'sudden' ones, for shifting from fossil fuels to fusion! He3 is the most attractive fuel, and scarce as it is, a little of it goes a long ways.

In practice, though (as distinct from a story setting!) I doubt we'd have to go all over the Solar System looking for it. I believe that it can be brewed up in a D-T reactor, and in fact the T can also be brewed up. And on the moon, dirty breeder reactors are not a problem!

In the same setting in which I spoke of the 5 mile...

2009-07-02T16:33:31.886-07:00

In the same setting in which I spoke of the 5 mile long xray laser ship and the sheepdog style fighters, I also helped with a lot of the rationales for intrasystem travel.

The whole thing boiled down to the fusion economy. For some reason (that I never found out) fossil fuels suddenly stop being usable (I think it was some sort of terrorist attack). After the initial grab for resources war, the Earth had to solve their energy problems with fusion power. Initially, the Deuterium-Tritium fusion was used, but there were concerns about high energy neutrons, plus getting all that deuterium and tritium was not terribly easy. That lead to Helium-3 fusion, but He3 was even more rare. Earth struck out for the Moon pulling those He3 reserves. Fusion technology advanced bringing online the D-D breeder reactor that made Tritium and Helium-3. But again, there were radiation concerns and as far as we knew, Earth was the only habitable planet in the universe.

Earth's demand for power was never ending and they wanted more and more He3 for the terran power plants. Note that He3-He3 is the cleanest fusion but it also requires tremendous energy input and containment. The magnetic fields needed for He3-He3 fusion proved unfeasible for space vessels, but the D-T fusion rocket was very usable and the waste wasn't an issue in space.

So, Earth expanded outward, looking for resources. First the moon, then Mars (orbit) as a shipyard for the belt miners. If you can get material from the asteroid belt, you don't have to lift it from Earth surface. Several Earth-Mars cyclers were eventually set up at the various Sol-Mars LaGrange Points.

The initial Jupiter Class tankers for scooping Jupiter's atmosphere for Deuterium and Helium-3 were fission rockets. When the Human FTL was invented, Jupiter became largely forgotten in favor of Uranus's Moons Oberon and Titania. The fission powered Jupiter class tankers were retasked to Saturn, specifically Titan for its Nitrogen reserves. New D-T fusion tankers continued operation around Jupiter, but instead operated ion mining from cosmic spallation within Jupiter's radiation belt. Three times as many of the new D-T Jupiter Class ships went to Uranus to act as tugs. The new class of vessel, the Uranus class refinery ship needed those tugs for a slingshot maneuver around Uranus, bound for a 5 year trip to one of the Mars Cycler orbits. During that time, it refined the heavy water ice using the D-D breeder reactors, eventually reaching the cycler with enough He3 to service Earth for about 6 months. It also had a significant amount of Tritium, which it used for its Fusion rockets and also traded it in to the Asteroid Miners to recharge their Tritium batteries, which decays to He3. Eventually, all this Helium-3 goes planetside to Earth where people can appreciate clean plentiful energy...

Until the aliens show up and start zapping them from space.

Sabersonic - Deep space radiation, especially, may...

2009-07-02T08:37:10.733-07:00

Sabersonic - Deep space radiation, especially, may be a very serious barrier to any regular human activity; in the worst case a deal breaker.

I have tended to think of passenger travel as relying on speed, both to minimize radiation exposure and to save on thumb twiddling. But cycler stations are an interesting alternative, especially since even 'fast' orbits (absent magitech drives) take weeks, requiring cabins, galleys, lounges, etc.

And a good many people could do their work en route, e.g. writers. (!) They are out of telephone range, but email only takes minutes in the inner system.

The Interplanetary Space Tourism Industry would pr...

2009-07-02T07:53:24.408-07:00

The Interplanetary Space Tourism Industry would probably be extremely hazardous in its early decades, if not centuries, compared to the Earth Orbit Space Tourism Industry what with either the lack of an atmosphere that would protect said tourists and employees from space radiation or too much of the stuff that makes it too hot to survive any length of time. The Science Channel program Exodus Earth has some ideas on how that could be countered, but I have a feeling that said features aren't going to be easy to implement or even wide spread until the industry is profitable enough to warrant them.

Interplanetary travel would be akin to early twentieth century if one thinks about it. The fastest craft available still takes days to cross vast distances and the more economical and slower craft would take weeks, if not months to cross the same distance and would primarily cater to the freight and cargo industries. A Cycler Station would be extremely slow compared to either type of craft, but they could be similar to cruise ships of today and are basically Space Hotels but orbit two planets. It may take two years or so for a full round trip, but one might as well do it in style and luxury since delta V isn't that much of a concern except for getting off to your destination.

- Sabersonic

Stupidly, I thought a lunar elevator was out due t...

2008-06-04T20:58:00.000-07:00

Stupidly, I thought a lunar elevator was out due to the slow rotation. I forgot about Lagrange points. The thing is embarrassingly long, but can be built out of nonmagical materials, a major engineering advantage.

Nor did I think of cracking oxygen out of lunar rocks. This is what I get for not paying much attention to the Moon.

I don't see any reason this wouldn't work ...

2008-06-04T19:50:00.000-07:00

I don't see any reason this wouldn't work to get stuff on & off the moon cheaply.

http://en.wikipedia.org/wiki/Lunar_space_elevator

Given lunar material to work with you can extract oxygen with is most of the mass for hydrogen-oxygen fuel, or you can use an aluminum-oxygen rocket which needs no hydrogen.
http://www.asi.org/adb/06/09/03/02/
095/al-o-propellants.html

Note: I put a linefeed in the above URL otherwise the end got lost.

Going to the near-earth asteroids for volatiles would be good, but there is a lot you can do with lunar resources.

I have not been a fan of the Moon, because it is n...

2008-06-02T09:10:00.000-07:00

I have not been a fan of the Moon, because it is not all that easy to get stuff off of. (Compared to an asteroid you can all but pull up alongside of.) It also lacks the stuff I'd imagine us wanting first in bulk quantities, volatiles for rocket propellant.

But all of this depends hugely on what we are doing out there, and what techs turn out to work well for doing it. If (as I imagine) the lunar surface is a good source of aluminum - however spelled - and mass drivers work nicely in service, that's an obvious source for fabricating stuff.

Which is a way of saying I'm gonna kick this down the road a bit to discussion of midfuture space development and how it might go.

I've tended to see space manufacturing as somethin...

2008-06-01T19:36:00.000-07:00

I've tended to see space manufacturing as something done in the earth-moon region rather than the asteroid belt. It would be either to make stuff for use in space or to make stuff that is much easier to do in zero gee or ultra-high vacuum ( or impossible to do without one or the other).

Space manufacturing would use materials brought up from earth if the quantities involved are tiny or if launch costs drop by a few orders of magnitude. Otherwise lunar or near earth asteroid materials would be used. Since the moon is closer, asteroid material would be used only for elements that are scarce on the moon, ie: Carbon Hydrogen & Nitrogen. Maybe also those siderophile elements, but metallic meteor fragments in the lunar regolith might be cheaper than going to the asteroids.

If space mining does result in much cheaper siderophile elements, it might depress the price of gold severely, but the platinum group elements are so useful for catalysts, their price would likely remain high enough for a lot of mining to remain economic.

Jim - your quibble could be right, especially sinc...

2008-05-30T20:29:00.000-07:00

Jim - your quibble could be right, especially since launch cost is one of the most intractable problems of space access. It is now about $10 million per ton or person. In the past I've used $100,000 or so as the level needed for extensive space travel - two orders of magnitude being an awful lot to ask for.

Even a tenfold reduction to $1 million requires major progress, but could be enough for significant numbers of people to go up on a regular basis, though the orbital tourist hotel business will be high end to say the least. On the other hand it is a lot to pay to ship stuff up.

The first thing we'll want to manufacture in space is surely propellant, since spacecraft use so much, probably burning off more than their whole "dry" mass each mission.

I've had a longstanding bias against space manufacturing, because of the image of huge industrial plants in the asteroid belt, rather outrageous for a long time to come. But useful space manufacturing could be on a tiny scale by Earth standards. An operation producing three tons per day of structural material is enough to build several spaceships per year, a pretty impressive space shipyard.

So once we have reliable interplanetary shipping, it might become worth looking at modest scale space manufacturing. And what is gold worth per ton?

"any assumptions about Earth-to-orbit launch cost ...

2008-05-29T18:24:00.000-07:00

"any assumptions about Earth-to-orbit launch cost that make it cheap enough for large numbers of people to go up there also make it cheap enough to send up food, structural fabrications, and so on, at least to destinations in near-Earth space, rather than building a vast industrial infrastructure in the asteroid belt and shipping stuff back"

I'll quibble with that. If we get something as cheap as what the space elevator people are hoping for, I think you are right, but I think there are Earth to orbit price ranges where mass drivers or the lunar space elevator for lunar launch or ion drives from near earth asteroids would compete for radiation shielding & raw materials for zero gee manufacturing. Note that using slag for Apollo style heat shields makes sending stuff down cheap even with present technology.

My favorite scenario for asteroid mining involves 'siderophile' elements Ie: the elements that 'like' to go into metallic iron rather that silicate rock. Most of earth's supply of these elements is sitting in the core where they are a little hard to get at :^) So it might be economic to mine the nickel iron asteroids for these elements (platinum group, gold etc)& bring them back to earth. The iron etc would be kept for use in the asteroid belt.

I've also seen the suggestion that electromagnets could be used to pull out small fragments of nickel-iron meteorite from the lunar regolith. Those could be processed to extract platinum group elements.

Re: jupiter's moons - IINM Callisto is outside the radiation belts, unlike the other big 3.

An interesting possibility for interplanetary travel is Robert Winglee's Mini-Magnetosphere Plasma Propulsion (M2P2), which is a sort of magnetic sail for catching the solar wind & rotating planetary magnetic fields. IINM there would be some common components in an M2P2 drive & some sorts of electric drive, so using M2P2 when you want to accelerate away from the sun & ion drove otherwise could have some advantages.

I think space elevators for getting on & off bodies smaller than earth will be important even if we never get materials strong enough for an earth to space elevator. Many asteroids & moons have gravity greater than the acceleration an ion drive can generate, & current materials can be used for a space elevator for these bodies. The interplanetary nuclear-electric drive ships can rendevous with the tether, or just carry the tether to drop to the surface of a newly visited body.

Too true. The best way may well be to either go to...

2008-05-28T19:28:00.000-07:00

Too true. The best way may well be to either go totally modular or have multiple ship classes, each with their own sets of capabilities.
Ferrell

Transportation economics can be wonderfully weird,...

2008-05-26T21:42:00.000-07:00

Transportation economics can be wonderfully weird, mainly because it costs nearly as much to run an empty bus as a full one. The space line is eager to sell a ticket for the last empty roomette on an interplanetary liner, for a lot less than a million dollars. One more passenger, plus baggage, and food and air for the trip, is no more than a ton, so the cost to the space line is only a couple of tons of propellant, or a very slightly reduced speed, easily absorbed in the schedule.

If you have one ship making alternate fast passenger and slow freight runs, you might want a semi-modular design where you can disconnect the whole passenger compartment, with all its life support, etc. The slow freight run is probably robotic.

But it's equally possible that the best economics will turn out to be quite different ship classes, fast passenger/express ships, and slow freighters. I'll explore this a lot more in a front pager, but on near-Hohmann orbits even 0.1 milligee is acceptable, meaning a much bigger payload relative to ship operating cost, even with slower turnaround.

Passengers demand speed, because a year is a long time to twiddle thumbs in a roomette, plus the hotel expenses pile up.

"Hauling cargo may not hold ticket prices down, be...

2008-05-26T13:43:00.000-07:00

"Hauling cargo may not hold ticket prices down, because it takes up payload mass, reducing passenger capacity. (Passengers themselves don't weigh much, but the cabin structure for them does.)"
Maybe, but that supposes that the ship can carry either passangers or cargo; Passanger cabins might be contained in a removable habatat module, but most likely it will be a permanent part of the ship's structure. The cargo, on the other hand, would most likely be bolted onto the ship's structure, with only those items that are sensitive to tempoture, pressure, and/or radiation would be inside the hull. The added cost would be in propellent and I'm not sure how much that would cost per kilogram. You'd have to factor in finding it, purifying it, shipping it, and the labor involved in filling up the tanks. However, the more people that buy tickets, the lower the cost. Up to a point, anyway.
Ferrell

Ferrell - Ceres should be miffed at me! Fortunatel...

2008-05-25T17:13:00.000-07:00

Ferrell - Ceres should be miffed at me! Fortunately she must be the gentlest of the Olympians, the goddess of grain, so with any luck she won't turn me into a bowl of cornflakes.

(It wasn't a thinking-ahead mistake but a total brain fade!)

Hauling cargo may not hold ticket prices down, because it takes up payload mass, reducing passenger capacity. (Passengers themselves don't weigh much, but the cabin structure for them does.)

On engine types, there's a tendency to think only of the most spectacular vehicles, which may tend to a single engine type, e.g., all big modern airliners have turbofans, though plenty of smaller ones are turboprops, and piston planes are still flying passengers.

Electric space drives are especially ill-suited to most local service. So in a setting like this, even if big nuclear-electric interplanetary ships are the queens of the spaceways, other rocket types will remain conspicuous, doing everything but interplanetary missions, and sometimes those.

Barring a vastly sweeping and unforeseeable tech revolution, plain old chemfuel rockets will be ubiquitous as far into the future as the eye can see, because nearly all spacecraft, whatever their main drive, need attitude/maneuvering thrusters, and most local service spacecraft will be all-chemfuel.

Nuke-thermal and solar-electric rockets (the latter with very gentle thrust) have niches, while Isaac Kuo at SFConsim-l makes a case for laser-driven rockets for freight service on heavy-traffic routes.

Interesting post. Your spaceship concept seems rea...

2008-05-25T15:33:00.000-07:00

Interesting post. Your spaceship concept seems reasonable. As a kind of general purpose transport, you might be able to reduce ticket costs even more by hualing cargo every trip; I'm sure that colonies, outposts, and touriest hotels will need items that can't be supplied locally. By the way, I'm sure that when you begain writing about the asteroids, you ment to said tha Ceres, not Juno, was a dwarf planet. Thinking about the next paragraph while writing is always a good way to mistype something. Heaven knows I've done it enough times!
Something that you mention, about having different types of rocket engines, I really have to agree with. So often, during discussions online or where ever, people just assume that there is only going to be one-size-fits-all rocket motor and that's it. It annoys me; here and now, we don't use just one type of engine to propel vehicles, why should rocketships be any different? Anyway, good post. I hope you decide to continue the theme next time.
Ferrell