Factual space fleet composition

[hongi]

Present day Earth trying to meet an alien invasion in orbit? Give Footfall by Larry Niven and Jerry Pournelle a try. Although the Michael might now be more automated in today's age than outfitted with a manned crew, like a big Predator aircraft. The advantage of Michael's crew was onsite human reaction to changing situations, and dealing with damage control.

Is an Orion feasible in the first place?

[TOSDOC]

Is an Orion feasible in the first place?

That's a good question. If you mean technologically, I'll leave that to the engineers, but this article and its links made for very interesting reading. It's true this is one of Eleventh Century Remnant's untried space vehicles, due to the Atmospheric Test Ban Treaty among other obstacles, but the premise was tested successfully using conventional explosives:

http://en.wikipedia.org/wiki/Project_Or ... ropulsion)

If you mean politically, socially, and economically, I'd say not at our current state of world affairs. Footfall's state of affairs was much more extreme, and the situation in that story called for getting a battleship in orbit by any means necessary as soon as possible to regain air and space superiority. In that case only the technological limits had to be overcome, and they did so with remarkable ingenuity.

[Eleventh Century Remnant]

Oi! Don't blame me for the failure of Project Orion...

For as close as the internet is likely to get to the Encyclopeda of the Real, there's http://astronautix.com/index.html- the main entry on the Orion confirms that while the physicists thought it was great, the project manager wasn't predicting flyable hardware before 2010-2030, and at least one person- a mathematician- thought "Zis is not nuts, ziz is super-nuts". There are numerous entries on various aspects of the project- use the alphabetical index, the search function doesn't work- as well as various other projects and articles that have gone by the name.

Personally, comparison with various other projects suggests it would not have been easy, apart from anything else the designers saying 1964 and the project engineer saying 2010 does not sound like a well integrated program, but the propulsion physics were sound, there's no cheaper method of getting mass off earth; the legal concerns, the test ban treaties ultimately being intended to preserve MAD, the private legal concerns in particular- Orion was much less of a rad- spewing monster than usually represented, cleaner than most atmospheric tests, but that's still a hell of a lot more than none.

There were many different sizes of Orion design, ranging from endoatmospheric explosive powered testbed past could have been got off the ground by the first stage of a Saturn V, through fifty men to Pluto (and think of the age this would have been happening in before quibbling with "men")- up to twenty million ton starship. Basically, they would not have been plain sailing but they were well within the realm of the physically practical, international law prevented them happening, and in a metaphorical way they were shot down by the oldest and probably most effective strategic weapon of all, Fear.

For that reason, and for the purposes of the thread, Orion fails the practicality test, as do most nuclear rockets.

Chemical propulsion, sheer cost holds practical size and reach back to the realm of the armed probe/drone ships already discussed, and dirty work becomes a much cheaper alternative.

Then there are further out possibilities like the ideas NASA's Propulsion Research Laboratory get paid to think about, electric ion and plasma drives that could be real- could have been real a hell of a lot sooner- if actual time and money were invested in them, and maybe ideas like Mach- Lorenz Thrusters, Heim- Droscher Theory- which may actually be testable, and if true will make space a very different and much more accessible place; all that is probably too far out on the fringe to consider factual, though.


There's an idea we've been missing; solar sails. They have been inching micrometrically towards the practical since the late sixties, deserve to be real, and pose interesting challenges. For one, the sail might be the weapon, if it can be made to flex enough to focus on a small area. Magnetic wire with thin reflective material laid over it, an interesting plot could be made out of that.

[Eleventh Century Remnant]

The economics of chemical launch are easier to find than things like the production cost of bombs; try http://www.theculture.org/rich/sharpblu ... 00066.html- not sure if the picture will import, but

The cost of "interface" transportation between the surface of the Earth and low orbit is the determining factor in the feasibility of many schemes for space industrialisation. If access to space is sufficiently cheap, then not just mining operations (as described in part one of this series), but solar power satellites, scientific outposts on the Moon, voyages to Mars and even cities in orbit would become affordable. Unfortunately, very little progress has been made in the development of cheap launchers. In 1996, it cost $11.8m (2002 dollars) to put a tonne of payload into low Earth orbit using an Ariane 5 rocket. In 1962, it would have cost $13.3m (2002 dollars) to launch a similar payload with a Titan 2 rocket. Decades of technology and billions of dollars of development costs separate the rockets we use in the twenty-first century from the workhorses of the early years of the Space Age, and launch vehicles are no more cost effective than they were.

Some features of the history of launch vehicles are readily apparent:

•The price of launches has only rarely fallen below $10 million per tonne (the low stated price of the Proton 8K82K is most likely an artefact of the Soviet system rather accurately reflecting the high value offered by that vehicle).
•There are relatively few heavy lift vehicles (the now obsolete Saturn V and Energia, the Shuttle, the various Titan variants), and a large number of launcher types adapted to more moderate payloads (in the region of ten to twenty tonnes).
•Since the early 1980s, there has been a steady fall in the price of launches towards prices reminiscent of the Titan boosters used for moderately massive payloads in the 1960s and early 1970s.

On the other side, http://www.islandone.org/Propulsion/ProjectOrion.html, from which

Does it make any sense to even think of reviving the nuclear-pulse concept? Economically the answer is yes. Pedersen (55) says that 10,000-ton spaceships with 10,000-ton payloads are feasible. Spaceships like this could be relatively cheap compared to Shuttle-like vehicles due to their heavyweight construction. One tends to think of shipyards with heavy plates being lowered into place by cranes. How much would the pulse units cost? Pedersen gives the amazingly low figure of $10,000 to $40,000 per unit for the early Martin design (56); there is reason to think that $1 million is an upper limit (57). Primarily from strength of materials considerations, Dyson (58) argues that 30 meters/second (about 100 feet/second) is the maximum velocity increment that could be obtained from a single pulse. Given that low-altitude orbital velocity is about 26,000 feet/second, around 350 pulses would be required (59). Using $500,000 as a reasonable pulse-unit cost, this implies a "fuel cost" of $175 million, cheaper than a Shuttle launch. Whereas the Shuttle might carry thirty tons of payload, the pulse vehicle would carry thousands. If one uses the extreme example of spending $5 billion to build a vehicle to lift 10,000 tons (or 20 million pounds) to orbit, the cost if spread over a single flight is $250 per pound, far cheaper than the accepted figure of $5,000 to $6,000 per pound for a Shuttle flight.

Going by the best numbers available, you're flat out wrong. Pulse units are much cheaper than you seem to think, and not having to design down to the extreme limits of precision and weight- saving required by conventional aerospace is cheaper still- by at least a factor of twenty-five.

[TOSDOC]

Oi! Don't blame me for the failure of Project Orion...

Wouldn't think of it! Please don't misconstrue!

No, sir. Is it Jane Fonda I'm thinking of instead?

[TOSDOC]

On the other side, http://www.islandone.org/Propulsion/ProjectOrion.html, from which

Thank you for those figures, that was some article. It's gratifying to see they were attempting orbital rendezvous via Saturn V's as well as working out launches from the ground. But the cost analyses are amazing--I wonder what they would be after adjusting for inflation.

[Eleventh Century Remnant]

Well, I can see that D13's obviously a fan of Valentin Glushko- the engines strapped to that goalpost must have developed at least 330 seconds Isp.

Going from

Eleventh Century Remnant wrote:
there's no cheaper method of getting mass off earth

That's insane. The only way it could be cheaper than the plain alternatives is if you either don't count the cost of the bombs or use cheaper material figuring its negligible mass anyway.

to

Stop right there, we're talking about different settings. I'm assuming space to space transport, which is a whole different beast than Earth launch.

is at the very least slipshod and a failure of comprehension.

Reinforced by failure to read the title of the linked paper- "Project Orion; Its Life, Death, and Possible Rebirth"- mistaking an apple for an orange, or possibly the other way around, the paper is present tense, intended to convince that Orion is worth doing now, and the references are to current (at the time of writing) costs for both, and actually a worst- case for bombs. Not a valid objection.

As far as the book "Atomic Audit; the costs and consequences of US nuclear weapons since 1940" goes,

First, what did nuclear weapons cost the United States? From 1940 through 1996, we spent nearly $5.5 trillion on nuclear weapons and weapons-related programs, in constant 1996 dollars.

, but

In fact, when we add the cost of deploying offensive delivery systems to those of defensive weapons, along with the costs associated with targeting and controlling the arsenal, we find that 86 percent of what was spent was spent on building a variety of launch systems and ensuring that not only could they be fired when ordered to do so but, more important, that they would not go off unless valid launch orders were issued.

Which goes some way to set

57. Kenneth A Bertsch and Linda S. Shaw, The Nuclear Weapons Industry
(Washington D.C.: Investor Responsibility Research Center, 1984),
on p. 55 state that warheads for 560 ground-launched cruise missiles
were expected to cost $630 million. Not only were these military
weapons but they were quite likely fusion devices as well and so would
be significantly more expensive than simple fission bombs.

in context.

And for chemical rockets, pray tell; how? Exactly how do you reduce the cost of chemical surface to orbit by a factor of twenty-five or more? Given that the ten thousand dollar to orbit figure is the nearest rough estimate of a historical average of what turned out to be practical- for this to be true and more than wild assertion, three thousand (the likely Isp of an Orion rocket) has to be the same as 476 (hydrogen-oxygen chemical). Two plus two still doesn't equal five.

[spartasman]

Here's a question. How expensive would it be to transport manufacturies to a base located on the Moon (Moonbase construction not included) and assemble a ship there? Surely the lower gravity would require less fuel to launch?

[Rabid]

I heard the Japanese are now trying to industrialize space. 'Cause they want to install solar power plants in orbit.

Even with the good old chemical rocket, the industrialization of space, by the economy of scale it will induce, will greatly cheapen launch prices.
When you are building rockets not on a "custom made" basis, for a particular launch ; but that instead you're mass-producing rockets with a large stock of spare parts, largely automated production, and an integrated assembly line (much like in the automobile industry), you have the opportunity to divide the cost by ten, twenty - hell, let's say fifty if there's a real will !

Now, how much is it to launch one tonne of stuff in space at the twentieth part of the costs of today ? Is it beginning to be affordable ?

[Simon_Jester]

Here's a question. How expensive would it be to transport manufacturies to a base located on the Moon (Moonbase construction not included) and assemble a ship there? Surely the lower gravity would require less fuel to launch?

As a general rule, a vehicle weighs less than the machinery required to fabricate its parts, assemble it, and launch it. Consider the relative weight of an airplane and an airplane factory.

Unless you have the market for many, many spacecraft, setting up a spacecraft factory on the moon won't save you very much money.

[Eleventh Century Remnant]

So, two points emerge here; it's a chicken and egg situation- spaceflight isn't going to get very much cheaper, and (pace the OP) a human presence in the solar system worth fighting about isn't going to happen, until there is mass production of at least airliner numbers of the things- which isn't going to happen until they get so very much cheaper that they can be built in sufficient numbers to carry the capability to establish a presence. Catch 22.

One possible way out of this is (or, let's face it, was) to avoid having to build rockets to aerospace tolerances, that and safety being the major factors in the cost, by going for massive single launchers- brute force platforms that can be assembled literally like ships.

I have to admit that, much as I think the world would be a richer and more interesting place if Orion had flown, it would also be a more radioactive one- and whatever the theoretical cost advantages of the project, it missed it's time. Not by much, but enough to be caught by the beginning of the environmental movement and make adding liability costs and indemnities to the cost of a launch probably prohibitive, if it could be made to happen at all.

One of the interesting things about Orion was that the bigger it got, the cleaner it got- the amount of fissile material staying much the same, around one critical mass per bomb, and the rest of the energy being taken up by fusion stages (which the writers of that paper don't seem to have been aware of, which is worrying)- so the larger it could be built, the lower the radiation release per ton to orbit would have been.

Sea Dragon's an interesting option- that enormous single engine might be a good idea on paper but it screams 'combustion instability' to me. Sea launch in itself, if the costs of Zenit- 3SL are a guide, is little or no saving- allows more orbital paths to be reached, launching from near the equator could save mass and add payload, but the sheer scale of it is the saving factor. Only five times the payload of a Saturn after all- I'd be much happier about the concept if it used clustered F1M engines instead of one unretrievable, monstrous point of failure, and I wonder what the true commercial cost would have been, once development was added?

Still comes up against the Isp problem, though- to quote Atomic Rockets,

The sad little secret about Orion is that the mission it is best suited for is boosting heavy payloads into orbit. Which is exactly the mission that the enviromentalist and the nuclear test ban treaty will prevent. Orion has excellent thrust, which is what you need for lift-off and landing. Unfortunately its exhaust velocity is pretty average, which is what you need for efficient orbit-to-orbit maneuvers.

[TOSDOC]

This is a cool discussion--I know it's a bit strayed from the thread, but I hope it keeps going.

What if we launched just one Orion big enough to set up a permanent base on the moon, from which future launches to explore the solar system would be considered cleaner and more feasible in the lower gravity? Then you could go back to chemical rockets and Shuttles to send parts and supplies (or get back to work on that orbital elevator).

[espatier]

Space Navy?

my question is why wold it be a space navy and not a new department that would handle threats from space?. I didn't think that the navy would cover space as a space navy.