Envisioning the world of 2100

[gturner]

Because, last time I checked, the STS is no longer operational and its replacement won't be ready before the end of the decade.

And its enemies would love to kill it thereby wasting money when they should be supporting it.

Its cost is going to kill it, not its enemies. The budget axes are going to start falling all over government, and NASA is going to have trouble maintaining a drawn-out development program for something that doesn't even have a payload when other branches are cutting essential services. It's going to face the same gauntlet as Ares and Constellation.

The Block 0 SLS can lift 70 tonnes and throws away both the solids and 3 RS-25D engines. The estimated cost of the Block 0 is $1.4 billion, which is $44,000 a pound to LEO, and its first launch is in 2018. Under the plan with the highest flight rate, it will then fly once a year till the launch of SLS #5 (which is upgraded to 100 or 130 tons), in 2021, and under the curent Senate authorization will fly once a year till 2026. That's nine flights for the next 14 years. Under the President's current budget we get 4 flights over the next 14 years. That's 930 metric tons delivered to LEO by 2026.

http://www.spacepolicyonline.com/pages/images/stories/SLS_budget_Integration_2011-08.pdf

In the 1990's the Shuttle was making about 7 flights a year, and just counting the roughly 55,000 lbs in the cargo bay, that comes to 175 metric tons delivered to orbit, per year, which would've been 2450 metric tons delivered between now and 2026, instead of the SLS's 930 tons under the Senate plan, or the 280 tons under the President's budget.

According to the plans the SLS isn't even as good at putting mass into orbit as the Shuttle was over the course of the next decade and a half, by a factor of about 3 to 10.

If that's the plan the execution certainly won't exceed it.

That's just one reason why the SLS program gives me cause for concern.

 

[publiusr]

It's what we have. My concern is this habit of starting something--then someone killing it--then starting something else, and its enemies killing that. SLS won't have that pesky orbiter to contend with. The SLS up mass will be all payload. This means that ISS would actually have been done more quickly with fewer large modules than with a lot of smaller 20 ton modules. That puts it ahead of an STS that wasted a lot of power on placing an orbiter in LEO.

I just don't like the idea of a lot of liquid sloshing around up there in a depot with boil-off problems. Now newtype wants a return to hypergolics--and a hypergolic depot would be fine--but we aren't going down that path. That decision has been made. The plus that comes from larger LVs for exploration is that you do all your fueling on ground level--put a heck of an upper stage up there with a big rocket--and get rid of those liquids as fast as you can. Things do wear in space--we saw that with LDEF and ISS solar panels, micrometeoroids, etc.

The plan is political, but there is nothing to say that if STS can fly 7 times of year with an orbiter--that SLS couldn't match that without one. That's a budgetary question--but that affects everything. We might get a president that destoys NASA--and then we get only what Musk can fund privately--and his LV was 80-90% gov't, so is that really private spaceflight if he is just another contactor?

Having 70 tons in space (orbiter free) allows for simpler missions, no Rube Goldberg assembly --at least for awhile--until we can afford a Mars ship that is more responsible than Musk's laughable one-way missions. I've been a big fan of Cassini's Ms. Porco, and she and others see easier sample return missions, icy moon landers and the like coming from SLS. It is capability--not frequency of launch--that is most important.

STS was an HLLV with only a Titan IV payload--and thus redundant. Free it of the orbiter, and you open up BEO in a responsible and engineering friendly fashion without depots that could easily make space debris worse by being a prolonged target to expansion, debris hits, etc. I don't want one of those things blowing up and making LEO a minefield.

Let's put that off--or at least have the depot a more sturdy SLS launched design with some meteor bumpers, and not an EELV launched balloon tank eggshell of a Centaur. That spooks the crap out of me. We had a small Briz failure a few years ago and it put more debris up there than the China ASAT test and the US sat-shootdown combined.

We have a space race exactly because R-7 was more than an ICBM needed to be. Where we shrank the payload, the Soviet response was--make the rocket bigger.

And you know something? It worked.

 

[sojourner]

SLS costs more per kg of payload than a smaller launcher. End of argument.

 

[gturner]

SLS costs more per kg of payload than a smaller launcher. End of argument.

I'm not sure SLS ever gets below $20,000 a pound to LEO. SpaceX is already selling Falcon 9 launches at $2,400 per pound to LEO. And that's their expensive, early system. He thinks $500 a pound is doable with expendables, and hopefully get down to $100 a pound if his grasshopper goes well.

If the government can launch 200 times the payload for the same dollar, they would be fiscally insane to retain the SLS.

--and then we get only what Musk can fund privately--and his LV was 80-90% gov't, so is that really private spaceflight if he is just another contactor?

Of the $1.2 billion in SpaceX (now valued at about $2.4 billion), NASA has contributed about $500 million, which is 20 to 40 percent, not 80 or 90%, and their private Iridium launch contract is $492 million.

 

[Mars]

Because running at full power, a typical fuel rod will only last for 20 (25 if you're lucky) before it decays to the point of no longer producing useable heat and subsequently becoming a serious radiation hazard.

Ah, but you forget, in space no longer usable fuel rods can be tossed overboard and never seen again, you don't need to store them anywhere or worry about their radiation.

And that's why your ship will get boarded for a "health and safety inspection."

Well the nuclear power plant will only be at full power for 20 years out of the 5000 year voyage, for the rest of the voyage, it will only be used to provide light and heat for the habitat. There is no other power source available in interstellar space until the discovery of fusion.

A molten salt reactor is probably going to be better than a conventional nuclear reactor, for a host of reasons.

1) A conventional reactor runs at very high operating pressures, requiring a heavy containment vessel, yet the containment vessel has to open to allow replacement of the fuel rods. That's very heavy and complicated.

A molten salt reactor can operate at atmospheric pressure, so the reactor vessel itself doesn't need to contain high pressures.

2) A conventional reactor has all the short half-life highly radioactive breakdown products trapped in the fuel rods, which not only causes problems with fuel poisoning, but the issue of a massive release of radiation during a melt-down.

Molten salt reactors allow the seperation of breakdown products from the fuel during operation because they boil out of the liquid fuel, making it easy to vent them somewhere else for storage, if even venting them overboard as a gas.

3) Having the reaction products boil out as a gas also eliminates most of the problems with reactor poisoning, an issue primarily with xenon-135, which has a 9 hour half-life and a huge neutron capture cross section, potentially sucking up so many neutrons that the reactor won't restart.

Reactor poisoning isn't much of an issue unless you have to rapidly cycle the ship's power levels for maneuvering to avoid space objects, but if you might have to do that, then designing to avoid poisoning is critical.

Naval powerplants use highly enriched uranium (instead of very low enriched uranium like commercial reactors) because they have to guarantee full power operation for combat maneuvers regardless of the output power levels over the previous few hours.

But going that route means you've massively increased the cost of the fuel, and created further handling problems because it's much, much more fissionable than commercial fuel.

4) Conventional solid fuel rods will need to be reprocessed, which is technically difficult.

If you toss them overboard, you're throwing away 97% of your potential fuel, which means you have to store over thirty times as much initial fuel on board.

The fuel rods, obviously, can't be stored too close together or you could risk a chain reaction, especially if a moderator is introduced (such as from a broken water pipe). So each future fuel rod has a shielding or storage space overhead.

Unnecessarily upping the mass and space requirements for your fuel storage by perhaps several hundred times isn't a good design, and the ship will have to be able to reprocess fuel anyway, because if it can't, it will one day run out of fuel without the ability to manufacture any more no matter how much uranium the crew can dig up.

5) If the molten salt reactor uses thorium, which is extremely likely, then you not only can reprocess the fuel on the fly, as part of the normal reaction cycle, but you can store tons of thorium as a giant lump, because it won't support a nuclear chain reaction no matter how pure it is. Thorium is also 100% fertile, so it can all be burned up. With the uranium cycle, you've generally got a lot of excess U-238 to deal with.

6) Molten salt reactors can run at much higher temperatures, making them more thermodynamically efficient. That means more available power to the drive system for a given thermal output.

On Earth, where the heat rejection is limited by outside ambient temperature, they could hit roughly 50% efficiency in a single fluid design. Water cooled uranium reactors run at about 35% efficiency.

In deep space, both reactors could have their efficiency impoved by further stages using lighter gases with lower boiling points, but the molten salt reactor would retain the advantage.

7) Molten salt reactors have a much higher specific power density, which is the energy output per mass. Conventional nuclear reactors work well in ships, which ran pretty well with coal-fired steam piston engines, but molten salt reactors were first designed to power an Air Force bomber. In aerospace applications, that's an advantage that's hard to ignore.

8) Conventional reactors have to be shut down for long periods to replace the fuel rods. That means you have to have multiple reactors to guarantee that power will always be available to keep the ship from freezing.

Molten salt reactors can circulate the fuel in and out as part of normal operations, so they never actually need to shut down. They can also be shut down, the fuel drained, and then refilled and restarted up to full power in just a few hours, as opposed to weeks or months with a conventional reactor.

9) Since their reactor vessels doesn't have to hold high pressures, they are thin and lightweight, which means they are vastly easier to store, move, or fabricate, and multiple vessels could be carried for inflight swapping if neutron embrittlement becomes an issue.

The reactor shielding (the room's walls) doesn't have to be structural, so it never has to be swapped.

So neutron embrittlement is at least easier to cope with in a molten salt reactor that has to run for centuries, because fabricating a very thick, high pressure vessel is always difficult, or requires carrying a whole lot of extra steel.

10) Thorium is more abundant than uranium, and doesn't require enrichment, so any human colony using thorium just needs to mine it, instead of trying to build an isotope seperation facility.

Canadian CANDU reactors don't require fuel enrichment, but they do require a source of deuterium, which they extract from seawater. Though not technically difficult, it does require processing about 6,000 times as much water as would otherwise be required.

And if the destination solar system is much older (or derived from older source materials) the U-235/U-238 ratio will be lower, possibly preventing even a CANDU from running without some level of fuel enrichment.

****

A final note is that from an engine standpoint, you've got the initial and final acceleration phases (which burn fuel), and your coast phase where you keep the ship from freezing (which burns fuel). Once you've got hard numbers for the power requirements of those phases, you'd optimize for the minimal total energy consumed during the flight. If the deep-space heating and lighting is a huge demand and delta V isn't that expensive, you'd accelerate more to shorten the trip (100 years of lighting takes 50 times less fuel than 5000 years of lighting).

Thank you for your expertise in this matter. I am not wedded to any particular reactor design, I just assumed the fuel would be uranium because that is what powers commercial reactors.

 

[gturner]

^ Ironically, LFTR (Liquid Fluoride Thorium Reactors) were a dead relic of the 1950's and 60's until Kirk Sorensen of NASA was looking into reactor designs more suited to space travel. He started http://energyfromthorium.com/ and then founded Flibe energy to build reactors, inititally focusing on the military market because they have their own seperate certifications (If military reactors had all the red-tape and roadblocks as commercial nuclear powerplants, it would take decades to launch a new submarine).

[yt]http://www.youtube.com/watch?v=6-uxvSVIGtU[/yt]

 

[Robert Maxwell]

How do you propose handling the corrosion problems of thorium-cycle molten salt reactors? Isn't that the main thing that makes them impractical for long-term use?

 

[Mars]

Like I said, whatever works, whatever off the shelf commercially available nuclear reactor at the end of the 21st century, I admit I am not a nuclear engineer, but I know about nuclear power plants, and the Fusion program just seems to be soaking up money and their progress is so slow with them talking multiple decades just to build an experimental reactor the ITER, and multiple decades more to build a commercial power plant with what was learned. I think if we are to do a starship by the end of this century, it could only reliably count on atomic fission as its main power source, I've calculated by the way it would take 1000 metric tons of fissionables to light and heat a 500 meter diameter Island One Bernal Sphere habitat for every 1000 years of the journey, and at 300 km/sec, that journey to Alpha Centauri would take 4100 years, because Alpha Centauri is approaching us, so figure 4100 metric tons of fusion fuel for lighting and heating the habitat.

 

[gturner]

How do you propose handling the corrosion problems of thorium-cycle molten salt reactors? Isn't that the main thing that makes them impractical for long-term use?

It's not a horribly difficult problem, and one that has some pretty good solutions.

Here's a 2010 report from Idaho National Labs on the issue, which is covered on pages 5 to 10. (Highly recommended, easy to read with lots of graphs)

http://www.inl.gov/technicalpublications/Documents/4502649.pdf

It looks like chromium content in a molten salt with graphite causes most problem with favored alloys, with a chromium carbide intermediary and chromium plating out on the graphite. Nickel is largely unaffected, and cobalt and molybdenum should likewise vastly improve things.

Some of the higher chromium alloys had a corrosion rate rangine up to 1 mm/year with graphite, but Hastelloy N was 0.045 mm/year. Incoloy 800H without graphite only had a corrosion rate of 0.0033 mm/year (300 years/mm).

The report also says at a nickel coating stops the corrosion. They tried spray on moly and diamond coatings but they spalled, which should be a simple surface bonding/structural issue that could be fixed (getting Teflon to stick to a frying pan wasn't easy, either). Silicon carbide coatings also seem to eliminate the issue.

On approach I'd at least take a look at is using sacrificial anodes, perhaps aluminum or even zinc, depending on which element offers protection and is easily removed and reprocessed from the fluid. And of course since molten salts are so conductive, they could try putting an electric charge between the vessel walls and the graphite.

I've also read that some of the reaction products (like gold), plate out, making recovery for reprocessing difficult. But that could also be an advantage, if the reactor is coating its plumbing instead of corroding it (like hard water protecting copper pipes with a thin layer of scale).

So, as is true in most applications, you can pick the wrong alloy and run into corrosion trouble, or switch to an alloy that largely avoids the problem, while developing better alloys and coatings based on further experience and experiments.

If we just gave up on simple metallurgy and coatings problems, jet engine turbine temperatures would still be stuck at early 1940's levels.

 

[gturner]

Like I said, whatever works, whatever off the shelf commercially available nuclear reactor at the end of the 21st century, I admit I am not a nuclear engineer, but I know about nuclear power plants, and the Fusion program just seems to be soaking up money and their progress is so slow with them talking multiple decades just to build an experimental reactor the ITER, and multiple decades more to build a commercial power plant with what was learned. I think if we are to do a starship by the end of this century, it could only reliably count on atomic fission as its main power source, I've calculated by the way it would take 1000 metric tons of fissionables to light and heat a 500 meter diameter Island One Bernal Sphere habitat for every 1000 years of the journey, and at 300 km/sec, that journey to Alpha Centauri would take 4100 years, because Alpha Centauri is approaching us, so figure 4100 metric tons of fusion fuel for lighting and heating the habitat.

I think most people take a wait-and-see approach to fusion. If they get a reactor working for a year or two we'll have an idea what it would take, power-to-weight ratios, thermal efficiencies, neutron damage problems, and maintenance issues. Till then, it might as well be a warp drive.

But I also wouldn't design for a 4,500 year journey to the nearest star, for the simple reason that someone else could just devote a little more fuel to acceleration and get there in 500 years. That means that when your slow ship arrives, people will have already been living there for 4,000 years.

Even with a population increase of just 0.5% per year, it means that your ship's passengers will be greeted by 400 million descendants for every person who departed on the 500 year ship. But of course 50 years after the launch of the 500 years ship, somebody will launch a 100 year ship, and 50 years after it launches, someone will launch a 20 year ship.

Ironically, for a while ships from Earth will probably arrive at the nearest star in the reverse order that they launched.

 

[sojourner]

Ironically, for a while ships from Earth will probably arrive at the nearest star in the reverse order that they launched.

I actually think this will be the biggest deterrent to launching slow boats to other stars.

 

[Mars]

^ But that's just the point, a 300 km/sec starship could be built by the end of this century using off the shelf technology.

A 3000 km/sec starship would require at least a fusion power source, that is 1% of the speed of light the rule here is take the distance to the star in light years and multiply it by 100 years, so a 3000 km/sec could reach Alpha Centauri in 440 years, I don't know if we'll have the technology to build it by the end of this century, possibly if we have reliable fusion by the end of this century. Its likely the fusion fuel would be deuterium and tritium same stuff to make hydrogen bombs out of, another possibility is helium-3 and deuterium, but that is harder to fuse and would require the mining of a gas giant to obtain enough Helium-3, the most likely gas giant probably would be Saturn due to its lower gravity, though I think it might be a stretch to expect mining operations in the vicinity of Saturn by 2100.

A 30,000 km/sec starship would require a staged fusion rocket or antimatter, it would be a hideously expensive thing to have throw-away rocket parts, probably only a massive government program could attempt this, another wild possibility is a giant laser to push a starship up to 10% of the speed of light, to calculate travel time, simply multiply the distance of the star in light years by 10 years, for a trip to Alpha Centauri it would take 44 years.

I think in all cases, we need a 500 meter habitat sphere even for starships that reach 10% of the speed of light, as 44 years is half a human lifetime they'll need somewhere comfortable to live for 44 years. I think acceleration should be limited to 1% of Earth gravity max, as where talking about a rotating sphere.

1% of Earth's gravity is 10 cm per second squared, and at that rate it would take 9.51 years to reach 10% of the speed of light or 30,000 km/sec.

At 0.1% of Earth gravity or 1 cm per second squared it would take 9.51 years to reach 1% of the speed of light or 3000 km/sec.

At 0.01% of Earth gravity or 1 mm per second squared it would take 9.51 years to reach 0.1% of the speed of light or 300 km/sec.

If we wait for these more advanced technologies, we are allowing ourselves more time to destroy ourselves. If the goal is to preserve the human race, there really is no hurry to get there, but there is a hurry to launch a starship, the sooner we launch this ship the sooner we would have "bought" the insurance policy against the extinction of the human race. I think it would be easier to develop artificial intelligence than fusion reactors or antimatter reactors and a way of mass producing antimatter in a large enough scale to power a starship, and if we could do that, how much easier would it be to destroy ourselves with control over energies like that? I would feel safer if we launched as starship sooner rather than waiting for the technologies to arrive to send a human crew over there within their own lifetimes.

 

[gturner]

Well, the crux of the launch issue is time and economic expansion. You say staging would be prohibitively expensive, but that's only true at the time that you're building your single-stage mission. If we're building a rocket to another star we'd obviously be mining the solar system and expanding out into its vast supply of resources, creating a huge boom. Let's give that period a very conservative 5% economic growth rate. In 40 years, when the economy has expanded four-fold, launching a staged rocket with a mass ratio of four and the same payload will be the same relative cost as launching your original rocket, and be guaranteed to arrive much, much earlier. That earlier arrival time translates into economic and population growth at the other star, because there aren't any resources to exploit in-transit.

That leap-frogging of the missions just through economic expansion can be counted on to occur, even assuming no technological advances in propulsion. It's the same effect we see with Earth launches using chemical propulsion, which hasn't really advanced since the 1950's or 1960's. Even with the massive drawdown of launch funding after Apollo, the expansion of the economy means that we can keep putting mass into space at a higher and higher rate, even without concentrating on it, as long as there is a justification to expand into space. These same forces will be at work once we're living and working in space, at least by the time we can even contemplate an interstellar mission.

The implication of that is that the early, slow, single-stage ships will arrive at their destination so long after the ships launched later that their existence will be entirely irrelevant (10,000 new people will arrive at a star whose population is already in the tens of millions or billions), at least aside from the practical example their flight provides (we can do this! And oh, don't use terbillium coatings and remember to bring avacado seeds, because we just ate the last of a guacamole).

It may be that you're chosing the wrong destination. The nearest stars are guaranteed to get populated by later missions. Perhaps you need to switch destination stars to someplace obscure, or treat your mission as an ark whose destination doesn't so much matter as the fact of its existence, or design your mission to accomodate technological upgrades in-flight by including an ability to bootstrap new manufacturing abilities on board, so the latest Earth-tech propulsion innovations can be re-created with materials and equipment on hand.

 

[Crazy Eddie]

So tell me why can't you run a nuclear reactor for 5000 years?

Because running at full power, a typical fuel rod will only last for 20 (25 if you're lucky) before it decays to the point of no longer producing useable heat and subsequently becoming a serious radiation hazard.

Ah, but you forget, in space no longer usable fuel rods can be tossed overboard and never seen again, you don't need to store them anywhere or worry about their radiation.

I didn't forget that at all. It's immaterial, because whether you store them or eject them, radioactive waste can't be used as a fuel source and the reactor must be completely overhauled at regular intervals to replace those fuel elements.

But slow starships are relatively cheap to build

Spoken like someone who knows anything at all about how much it would cost to build a starship.

As for World hunger, AIs alone could solve this problem

Not in the next 50 years they won't. Though, admittedly, automation will probably begin to raise the quality of life for the third world long before it empowers humanity to build utterly impractical traveling space colonies.

Machines would be in the same peril from obsolescence as humans.

Humans are not in peril from obsolescence. Humans are imperiled by the greedy machinations of other humans. AIs, on the other hand, are no more threatened by obsolescence than a fork is threatened by a spork.

Well this ship can certainly be launched by 2100

On the Islamic calendar, sure. But not any time in the next 80 years; we don't have anywhere near the spaceflight infrastructure needed to even dream about that sort of thing, and we'll be lucky to even be DEVELOPING it by the end of the century.

More to the point: the advent of AIs might make that entire concept moot, since by then we'd have developed computerized spacecraft that can explore the solar system by proxy and will avoid the expense of maturing manned spaceflight altogether. Your generation ship would simply be a probe the size of a winnebago containing three thousand frozen embryos and a set of really beefy landing thrusters.

I remove myself from immediate consideration, it is the rest of humanity, those that will come after me that I am concerned about

I am not sufficiently concerned with the rest of humanity to make a substantial financial investment to ensure the continuation of the species against a threat that may or may not never materialize in a plan whose outcome will probably never be known. That is simply not a smart thing to EVER invest money on. Because I am probably not in the minority in this opinion, a generation starship of the type you describe will remain another "cool but impractical" concept in science fiction.

Why does one buy life insurance, this is life insurance for the human race, I think it is worth some effort and expense.

It is. So freeze the embryos and hide them in an ultra-secret bunker a thousand feet underground. We could do that with TODAY'S technology... IF we had any reason to believe humanity was threatened with extinction at any point in the near future.

People buy life insurance because they know they're going to die. We don't know this is true of humanity yet, so there's no reason to ensure against it.

I hate to tell you this, but its not working, North Korea has acquired the nuclear bomb and Iran is acquiring it

And before them, Pakistan and India, none of which were signatories to the non-proliferation treaty at the time (North Korea is sufficiently isolated and sufficiently broke to render this a non-issue).

And Iran is not interested in a nuclear weapon (if they were, no one would care). They're after nuclear POWER, which is economically and politically destabilizing in ways that a nuclear weapon can never be. With the capacity to build warheads, Iran can only make empty threats and rattle their nuclear sabers to make their voters feel better. With nuclear ENERGY, they can apply leverage to oil production and commercial transit through the Persian Gulf, hiking global energy prices to impose political change to their own advantage. It is this reason, also, why nobody cares that North Korea has nukes: with a nuclear warhead you can only destroy one really really big target and then duck your head down and suffer the consequences, which otherwise still leaves you politically powerless on the world's stage.

Keeping AIs out of the hands of pariah states becomes a far greater imperative because that sort of technology would have the effect of economically and politically empowering anyone who masters it. The treaty would doubtless be written to reflect this, allowing powerful first world countries to continue to use and develop AIs while everyone else gets carpet bombed if they get caught researching the subject without a U.N. permit.

Its hard to predict the unpredictable

Really? You don't seem to have any trouble throwing around suspiciously accurate predictions as if they were certainties.

And we're back to starting a nuclear war aren't we.

You don't need nukes for something like that. Just ask the Iraqis.

Its not the numbers but how far they are spread out that matters. If you can pack one billion human beings within the radius of one nuclear bomb blast, then they all die if one goes off

No they won't. ALOT of them will die instantly, and a lot of them will die days and weeks later to medical complications due to radiation poisoning. Even then, a nuclear detonation in a metropolitan area can be expected to produce casualty rates between 40 and 70%.

So even if half of the human race is clustered together in a densely urbanized society, then of the 4 billion people endangered by the attacks, at least 1 billion will survive, and humanity's overall population would drop by about 30% at most.

A nuclear war or even a really bad conventional war will not threaten the survival of the human species unless a targeted campaign of genocide goes from town to town specifically targeting individual communities that otherwise have no strategic value except that people live there. This sort of campaign would require a MASSIVE military force, easily larger than the combined armed forces of all the nations on Earth, which is only to say that even if every soldier everywhere decided to kill every non-soldier on Earth, it would STILL take decades to accomplish this. It would take twice as long if this was being attempted by an outside force independent of those military forces (e.g. an AI rebellion). And if somehow this happens at a time when the AIs control all the military assets of the world, then it wouldn't NEED to happen because humans would no longer be in control of their own defense anyway.

It is the limited scope of humanity on one planet that is the danger.

Absolutely. Just not in danger of EXTINCTION, not on anything less than a geologic timescale. Simply put, there are too many of us and our resources too well developed, and a huge number of things would have to go south before we get anywhere near that point.

 

[Crazy Eddie]

Because, last time I checked, the STS is no longer operational and its replacement won't be ready before the end of the decade.

And its enemies would love to kill it thereby wasting money when they should be supporting it.

Flawed logic. The first thing they tell you in systems analysis is that bad money is bad money and throwing good money after it won't change that fact. If the system you're developing isn't feasible in the first place, terminating future development is a savings, not a waste.

Apollo was thinking big. STS was thinking reusable.

STS was thinking "let's build five space stations and use them as construction docks to build the Battlestar Galactica and then cruise around the solar system in style!" As such, the space shuttle was the first in a SERIES of big things NASA was dreaming about but never bothered to secure funding for.

We are not just starting out

Yes we are. We never got past the starting stages because our various big projects never develop into anything sustainable. We essentially have to start over from scratch every single time, because we can't afford the kind of incremental development timescales enjoyed by the rest of the aerospace industry.

Of course, the EELVS could, and for the most part they have. Mainly because they operate on a smaller scale, spreading experience and technical knowledge over a higher flight rate allows them to make developmental improvements a few at a time and evolve their capabilities into new technologies. Thus the EELV program has made technical and capability improvements in the past two decades, during which NASA has made no technical progress whatsoever and wound up REDUCING the shuttle's capabilities due to safety concerns.

In more familiar terms: when you move to a new area and start a new town, you start with houses, not skyscrapers.

What does NASA doe when any rocket blows up?

Suspend any further launches, pending two years of handwringing, technical reviews, theatre and apologia in front of congress, committees, consultations, more committees, studies, and a billion dollars worth of safety upgrades that reduce the rocket's capabilities by 30%.

Significantly, that means NASA's entire manned spaceflight program will come to a screeching halt until their Next Big Thing comes out of its mourning cycle and is cleared to fly again 25 months later at severely increased cost and severely reduced capacity.

So Griffin--who wrote AIAA texts is unsourced.

When you fail to provide the name of the person you're quoting or the context of that quote, yes, that means the quote is unsourced.

A man on Augustine who trashed HLVs, gave us the Roton.

A man on Augustine who supported HLVs is still beating his wife.

See, I can do that too.

what do you think launches heavy reactors--Delta IIs?

Delta-IVs, or IV heavies, probably.

 

[sojourner]

This is why slow boats are a bad idea.

 

[gturner]

what do you think launches heavy reactors--Delta IIs?

Delta-IVs, or IV heavies, probably.

But the Delta-IV is a dead-end because they can't make a Delta-V without confusing the f**k out of everybody.

 

[gturner]

This is why slow boats are a bad idea.

They're not necessarily a bad idea, even though they'll have no impact at the destination. It's the journey that matters.

With a warp drive, people from Earth could routinely venture to the millenia ship and take tours of it, staring at the spooky frozen embryos or aging crew, still stuck in the world of 2100 like cavemen stuck on a raft going in circles in an eddy in the Pacific.

In inflation adjusted constant 2010 dollars, I'm thinking $350 for the flight out to the millenia ship and $50 for admission. The souvernier shop would make a killing and could easily be restocked from the warp ships. Of course the actual crew would quickly abandon the effort, so you'd have to pay college kids to dress up in crazy year-2100 costumes and speechify in the old way, but they work cheap. Since the journey is going to take thousands of years, the return on investment should be astronomical.

After the first thousand years of profitable business you'd even hire people to play tourists from earlier centuries, so new visitors could see what it was like to gawk at the "Twenty-One Hundreders" back in 2350.

 

[Mars]

Well, the crux of the launch issue is time and economic expansion. You say staging would be prohibitively expensive, but that's only true at the time that you're building your single-stage mission. If we're building a rocket to another star we'd obviously be mining the solar system and expanding out into its vast supply of resources, creating a huge boom. Let's give that period a very conservative 5% economic growth rate. In 40 years, when the economy has expanded four-fold, launching a staged rocket with a mass ratio of four and the same payload will be the same relative cost as launching your original rocket, and be guaranteed to arrive much, much earlier. That earlier arrival time translates into economic and population growth at the other star, because there aren't any resources to exploit in-transit.

That leap-frogging of the missions just through economic expansion can be counted on to occur, even assuming no technological advances in propulsion. It's the same effect we see with Earth launches using chemical propulsion, which hasn't really advanced since the 1950's or 1960's. Even with the massive drawdown of launch funding after Apollo, the expansion of the economy means that we can keep putting mass into space at a higher and higher rate, even without concentrating on it, as long as there is a justification to expand into space. These same forces will be at work once we're living and working in space, at least by the time we can even contemplate an interstellar mission.

The implication of that is that the early, slow, single-stage ships will arrive at their destination so long after the ships launched later that their existence will be entirely irrelevant (10,000 new people will arrive at a star whose population is already in the tens of millions or billions), at least aside from the practical example their flight provides (we can do this! And oh, don't use terbillium coatings and remember to bring avacado seeds, because we just ate the last of a guacamole).

It may be that you're chosing the wrong destination. The nearest stars are guaranteed to get populated by later missions. Perhaps you need to switch destination stars to someplace obscure, or treat your mission as an ark whose destination doesn't so much matter as the fact of its existence, or design your mission to accomodate technological upgrades in-flight by including an ability to bootstrap new manufacturing abilities on board, so the latest Earth-tech propulsion innovations can be re-created with materials and equipment on hand.

You have to take into consideration that this slow starship will take 4100 years to reach Alpha Centauri, if what you say happens and it is bypassed by more advanced ships, the slow ship would still arrive 4100 years in the future around the years 6200 AD, by this time after 4100 years of technological advancement, I would be surprised to find flesh and blood humans populating the system, not that humans couldn't have got there, but if they got there 4000 years before the slow humans arrived then 4000 years of technological advancement may have advanced them beyond their physical flesh and blood human bodies, in other words they'd likely be no longer human, they might have uploaded their minds to machines or computers and become a society of AI, and as such they wouldn't need oxygen, wouldn't need an earth like environment, they could live anywhere that would allow their machines to operate, the humans arriving in the slow ship might find an already terraformed planet that was discarded by humans who had uploaded themselves into machines thousands of years ago, but these just arrived throwback humans could still use the planet.

Think of it not so much as a starship but as a one way time machine. The humans raised in the ship would be in a miniature world surrounded by 21st century technology, although they themselves have never lived in the 21st century, that would be the world they grew up in until they reached planet-fall.

 

[Mars]

This is why slow boats are a bad idea.

They're not necessarily a bad idea, even though they'll have no impact at the destination. It's the journey that matters.

With a warp drive, people from Earth could routinely venture to the millenia ship and take tours of it, staring at the spooky frozen embryos or aging crew, still stuck in the world of 2100 like cavemen stuck on a raft going in circles in an eddy in the Pacific.

In inflation adjusted constant 2010 dollars, I'm thinking $350 for the flight out to the millenia ship and $50 for admission. The souvernier shop would make a killing and could easily be restocked from the warp ships. Of course the actual crew would quickly abandon the effort, so you'd have to pay college kids to dress up in crazy year-2100 costumes and speechify in the old way, but they work cheap. Since the journey is going to take thousands of years, the return on investment should be astronomical.

After the first thousand years of profitable business you'd even hire people to play tourists from earlier centuries, so new visitors could see what it was like to gawk at the "Twenty-One Hundreders" back in 2350.

Think of it this way, if you buy a ten year life insurance policy on your self, and within that ten years you don't die, would you feel that was wasted money?

If we launched that slow starship and humanity destroyed itself before building a faster ship, that would be a good investment as it would have saved the human race, humans would get to start all over again on a new planet.

If the starship was launched and humanity did not destroy itself and faster ships bypassed it on their way to the destination, then it is just like the life insurance policy you bought but never needed because you didn't die, that life insurance policy still cost you money however, would you feel cheated if you bought a life insurance policy on yourself and you didn't die, or are you paying just to ease your mind that your heirs and dependents will be taken care of in the event you did actually die?

A slow starship that eventually gets there is like paying money for life insurance it turned out was never needed, its purpose is to save humanity should the worst happen, and at least its development would be a step on the path to even faster starships.