New Mars Forums

Phobos Dec. 11 02   
>  I wonder how you will generate the effort and
motivation to build one.

The same as any other colony effort. You won't get investors & politicians and the tabloid-following general public to fund a huge space effort so that a few people can explore and eventually a few will be able to live there.
It's never gone that way. You set up infrastructure so that people & companies can survive out there -meaning make money-and that lets things grow naturally. Eventually, enough people will get tired of living in metal cans -either on a spinning rope in space or on an unnatural planetary body without healthy levels of gravity- and get together to build a better home.
Would it be any different on Mars? Can you hear the politicians laughter at the idea of settling other planets -more accurately, their apathetic silence on anything having to do with space?
The space colony designs grew out of studies of what's possible. The shapes & design choices followed not by any aesthetic choice, but of necessity driven by the environment and available resources.
They first looked at other planets and the Moon, and the overwhelming logical choice for living & working in space was space colonies, most likely using asteroid resources.

> At least with a Mars colony you can build it
up just a little over time and you don't have to
do anything drastic like rip up whole asteroids and
build huge superstructures even though those
types of things would likely naturally come into
play later on.

The thing is that if you go down to Mars, the people will have to rotate home on a regular basis (probably undergoing drastic therapy to combat long-term exposure to low-G).
And they still won't have decent living conditions.

Take the first expedition's habs (which they lived in during the trip), and let them drift in space, spinning for partial G, loosely anchored to Phobos or Diemos (Ph&D) or your NEA of choice.
Take the ship apart, and place the cargo where you can mine the NEA and set up a first generation rudimentry space manufacturing facility.
This makes mirror, volatiles (all the kinds of ices), rolled & stamped metal structures, metal cables (really the most effective use of metal mass and strength), and concrete.
Build up the truss the habs were on during the interplanetary trip, so it's long enough and strong enough to spin the now fully shielded habs (1.6 meters of concrete for space radiation) for full Gravity.
It may take a few interplanetrary throws of equipment until they can build this much, but until then, they live in the habs spinning for partial G, or in shelters buried under a few meters of dirt on the asteroid during a solar storm.

When the habs are finished, future crews have completely healthy living conditions. None of this requires any extravagant manufacturing, and the same facility that make the habitat makes metals & ices available for shipment back to LEO for sale -the first and every mission makes money this way, while seting up a permanent living outpost.
That's why I like Ph&D, even though an NEA is more attractive in terms of the cargo which can be placed there by a given rocket -conversely, a smaller & cheaper rocket can place the same cargo at an NEA as at Mars or its moons.
Go to Ph&D, and you're building up your base/first generation colony, and an exploration staging outpost for Mars itself.

> There would have to be some economic or
other reason that would motivate the building of
these massive things.  I guess you could start
small ...

You see, the thing doesn't grow in one tremendous leap up to a huge colony, it makes barely enough living conditions for the amount of people there, for the comfort level they can afford at the time. It get bigger & more comfortable as it makes more & more money.
The exploration of Mars and the growth of the first off-planet colony fuel each other.

> And issues like overpopulation relief probably
wouldn't be an incentive either.

Much the same for colonizing Mars. We won't solve overpopulation on Earth by transshipping huge amounts of people in sardine cans to space. The only historical way to lower a population's growth rate is to raise the standard of living.
Eventually, space resources and the tremendous economic drive from them will have this effect on Earth. We're not thinking just a few decades ahead, but centuries & more.

Dig around PERMANENT for info about mining asteroids and products and production techniques.

1) Gravity & atmosphere, and the unstabe nature of the asteroid's structure: Don't live on the asteroids, mine them for resources to build space colonies, which will spin for full Earth gravity. Steel, rock for concrete, chemical ices for plastics and fertilizer and water.
Another point: Where do we get the idea that .38G (Mars) will be enough for us to live & be healthy? Nowhere but hope and guesswork. (wishful thinking, maybe?).
We have no idea what living long term in low gravity will do, and it's irresponsible to portray things as if we know for certain that we can live there.
We do know for certain that we can build space colonies (of various sizes from a couple of shielded tuna cans strung on a cable/truss -a station, really- to O'Neill's "Island 3") with no new inventions.

2) Asteroids are not made of sheer rock (not all of them). Some are dirty snowballs, with an outer covering of a few meters of dark dust. These are actually expended comets. Their surfaces have outgassed and left the dark dust behind, protecting the core ices left behind. These may be anywhere from a few meters across to tens of kilometers...
Even the ones we call "stony" will have ice crystals mixed throughout. Happily, they seem to have about the right amount of ices to serve as process chemicals to work the metals & rocks remaining.
Others are nearly 90% metals. Catch one of these and a CC  (snowball) and you're in business -riches beyond a Martians' dreams of avarice.

3) and primarily, the contention that Mars is a *planet*

So what? Just because every human alive or dead has lived their lives on this planet, doesn't mean that's the only way to live. Not even the best way, arguably.
See the FAQ at this site

Another aspect of this, Since Mars is a planet, it has a lot of stuff in one place. This is usually taken as a good thing, since you have "everything needed for a civilization in one place".
Problem: that "one place" is a whole planet! and planets are huge! Too much gravity to let you move round easily outside your habitat (while not being enough inside your habitat), too much to let you move anywhere else in the solar system for commerce.
Mars has a nearly 24 hour day? So what. That only means that you're stuck with 12 hours of night. On Mars, you need to expensively import nuclear reactors from Earth.  At an asteroid, point a metal foil mirror at the Sun, and you're set up.

Geothermal? please. The planet's core is dead. No magnetosphere means no magma. The volcanoes tell the story: a long time ago, they grew big (multiple overlapping impact craters inside the calderas). Large volcanoes means that the surface of the planet doesn't move over a liquid core.
It's a dead cold rock, with maybe a few outgassings. Hardly the making of a civilization, when asteroids are flying mountains of ice, with a fusion furnace right nearby for energy.

Mars has evidence of subsurface ices. We know for a fact that asteroids (and Mars' moons, interestingly) have ices by the gigatonne, and no prospecting. Land, scoop up some stuff, and heat it; steam comes out.

Look at some of the old NASA images of space colonies on that site I linked to.
No new inventions needed to mine asteroids for materials to build these things.
Lots has been said about how odd it would be, living inside a huge spinning can.
Live on Mars, and you're stuck inside a tiny can, and if you go outside it, you're in a suit! a pink sky! (low gravity makes our bones & muscles weak, so after your 1.5 year surface exploration stint, you go back to Earth on a stretcher to spend the next 15 years rehabilitating. Prove I'm wrong...)
Many people on Earth never leave their home town for years at a time, never explore mountains, never see the ocean or forests.
  In a space colony, you have no sunset, but you've got the stars like nobody on Earth has ever seen them, and if your colony is near a planet, you've got it anytime you look out and you can go visit anywhere.

They did studies on living inside a colony like this. They specifically designed them for long sight-lines and roomy interiors.
People would work for days in old US Navy dirigible hangars. a 30 meter high ceiling, and little office cubicles inside them. People come outside their offices, and take a smoke break "outside" under the hangar roof!
The point is that people live in all osrts of places, and a space colony is just a lot more likely to be feasible and profitable than terraforming a whole bloody planet.

I like thinking & reading about interstellar travel -I like mental masturbation almost as much as the real thing.
But that's all it is.
I don't care about interstellar. Get some of us off this planet, making a living, and expanding the livable area/volume available to life out off this one rockball.
Interplanetary is quite enough challenge for us, locked up down here at the bottom of a hole 8km/sec deep.

Another aspect of it, goes back the Fermi's question about ETs ("Where are they") and Dyson's belief that we, ourselves or whatever we evolve into, should be able to live on past the death of the Sun, and on to the end of the universe. We just have to expand off-planet! No new inventions needed to start.
With techniques we can think of now, and no new fundamental discoveries in theoretical or applied science, we can foresee ways to get to all the nearest stars within a thousand years. Ten-fold greater time, and we're on our way across this entire galactic arm. Another ten-fold jump in timescale, and we're across the galaxy and on the way to others.

What ever particular you want to debate about -life support, engine & power supply, biomedical, or what, if we don't know the best way, we do know several ways which will work.
Don't hold up the first steps into the solar system, becuase we don't know for sure how to go to the stars.

Anyway, all I mentioned in my earlier post, was using this particular effective technique we've got -nuclear pulse rockets- to go into the solar system. Not it nor anything else close to moving off the drawing board into a laboratory curiosity helps much with interstellar travel.

hear, hear. You make my point.

I choose not to argue for the ignorant hysterical view that anything relating to or containing the words "radioactive" or "isotope" or "nuclear" is evil.
Nuclear pulse is the best tool we've got, and I'm not going to forget about it because of their irrational fears about a certain class of technical innovation.

Read those CDI articles about a multinational effort to use discarded weapons to fuel a spaceship.
All it takes is what the Mars Society is doing. Get something hoepful going, get some notoriety, and some following. Get the general public to see what's going on, and get more & more support.
By the time you need an intitial mass in LEO of several hundred tons (like many mission proposals out there), and want a few hundred tons of cargo delivered to Phobos for the Mars base, then you start educating people on the realities on nuclear pulse:
1) There is no possible way -at all in this universe- that our use of nuclear pulse engines will hurt anything in interplanetary space. (Yeah, yeah, we could ram the ship into an asteroid, but does that really hurt anything?)
2) the Pu is there. We're glad the warheads are dismantled, but the job's not over yet. The stuff is worth more than gold or just about anything else inorganic, and the only other proposals being floated to get rid of it, involves polluting it past the point of being useful for making a bang, and burying it, where we'll have to guard it for 100,000 years until it decays so it can't be re-refined.
3) We have an incentive to get a large, robust ship & payload to Mars -quickly and cheaply.
4) the Pu and NPR is the best way to do it -and get rid of the Pu.
5) Oh, yeah. It helps foster greater international cooperation in dealing with nuclear materials and energy, and it helps foster disarmament in an atmosphere of doing something large-scale, long term hopeful for the future, and which brings us closer together as it gets us Out There.

You do the math.

Lots of hysteria and mis-disinformation here.

First: Who says $200 billion? Let me guess, the program's detractors!

Second, and by far the bigger question, Exactly what are we talking about?
The term "Star Wars" was coined by detractors specifically to throw ridicule on something they didn't like.
Go ahead and let your preconceptions show, if you want, but you're only hurting your own credibility about being capable of a rational discussion of the subject.

Go back to Reagan-era SDI porposal and what were they talking about? Terminal phase and theater AA missiles on steroids. (THAAD and the Navy's cancelled SM2ER-block 4 for example.)

Nobody seriously talked about "thousands of nuclear powered armed laser space fortresses" except the detrators (Where the $200 billion and higher price estimates came from -and that only if using the flying cost-overrun Shuttle to lift everything).

Read Freeman Dyson on ABM. Entirely rational discussion sheds much light. (not the hysterical, nearly conspiracy theorist detractions we hear which are unquestioningly accepted by the mass media).
(I think this was from the book From Eros to Gaia)

If, as SDI and NMD talk about, Theater/Terminal defenses are looked at (T/T ABM), the entire menagerie of phantom bogeymen thrown up against ABM dissapears.

It does not require space assets, except for more of the standard EW satellites and redundant C3I capabilities we already have.
Don't worry about boost phase, because that's not likely: It requires space-based weapons, which do threaten your potential opponents. An orbiting weapon capable of hitting a rising ICBM could also hit the politburo members while they're on vacation at a beach on the Black Sea. It necessarily requires C3I capabilities which can reach out over the enemy territory, and the fog of war makes this highly unlikely.
You're always advantaged, and the enemy is disadvantaged if the battle is being fought over your terrain.

Hence T/T ABM. Deal with the threat after the missile busses have deployed, and the decoys are out -all the cards on the table, no deception. Hit them all, or discern the real threats, which ever works.
BTW, even fielding an ABM works, even before a single shot is fired. Decoys, you say? A missile lifts so much. Add more mass, and the missile doesn't lift as well. Add decoys, and you must lose either warheads or range. Right there, your defenses have cut the attacking force down, eh? Even before that, you force them to do R&D on their countrerss to your defenses, adding more time and causing them to build fewer missiles. Again, you've stopped an attack from getting through before a shot is fired.

T/T ABM doesn't threaten the enemy. It only applies defensive force over your terrain.
It doesn't require nuclear weapons, it doesn't require energy beam "Death Rays".

Note that the Russians were in favor of multilateral ABM in the early days of NMD.
For decades, they've fielded early generation ABM in their SA-5 SAM system. They were entirely enthusiastic about bidding on the contracts for multilateral ABM.
Doesn't sound too destabilising -quite the reverse, and I wonder why people didn't see the hyypocrisy of the detractors when they didn't seize on this: It removes some fear of the good ol' boys spending too much money among themselves, by spreading the contracts out around the globe. It fosters stability, by easing up on secrets among unsteady partners, making them more steady friends. It defends everybody against small-scale attacks, and accidental launches.
The detractors screamed all the louder. They don't care about workable answers, they only want to force their world view on everybody (the impossibility of unilateral disarmament is all they offer. "Sit around in a circle and hold hands and sing! That's the answer for peace!")

As for hurting the Chinese delicate sensibilities by fielding ABM and de-fanging their nuclear threat and the deterrance of their weapons, I don't care a bit. They can cry into their tea.
They want to threaten our cities with nuclear fire. I'm all the more happy to remove the threat. Not that I believe ABM is a "Shield"; only the detractors use that term, to make it sound more impossible. A good defense doesn't need to be 100%. Just cast enough doubt in the enemy's mind to cause him to hesitate or forestall attacking, and your defense is 100% effective.
It makes me sick to hear anti-war people talking in favor of MAD! Insane! Totally morally & intellectually bankrupt, to speak as if the "method of preserving peace for the last 50 years" is the best answer! (Until we can convince the Pentagon to turn all their weapons into prayer wheels, anyway.)

I don't consider the Chinese or N.Koreans to be much of a threat. They know full well that we wouldn't hesitate a moment to eradicate every military base, rail head, deep-water port, and large city of theirs if we detected a launch. They would cease to be a civilised power of the 21st century if they tried it, and everybody (but media outlets) knows it. A dozen or so old-fashioned liquid-fueled boosters? Don't make me laugh.

As for the Pu239 from all those decomissioned missiles, I say we make it into thousands of identical small yeild bombs. Multilateral effort to account for and dispose of tons of weapons-grade stuff, by doing a large-scale multinational space mission. Send 20 people to Mars, with the seeds of a colony among the moons and a permanent exploration outpost.
Use the same technology of a city-killer bomb to get humanity out into the stars! After we use up all the warheads, build breeder reactors to make more Pu239 for more spaceships! Build more nuclear power plants on Earth to make more Pu, to get us out there, so we can eventually remove all the heavy polluting industry from the face of the planet and get out into the solar system permanently (Nice circle of answers to a lot of our problems, huh?)

2 articles about this "plowshares" idea.
Note that the CDI is most definitely not "hawkish" on defense. You should agree with them, and they are a necessary tool for understanding the military spending. Knowledge of the Defense Monitor is the first credential I look for in anybody talking out against war.
Orion will rise! - CDI - Part I
Orion can rise! - CDI - Part II

Yes, that Penn St. article covers antimatter pretty well.
Specifically, it's another form of nuclear pulse (Ion beam Compressed ANtimatter, or ICAN is another name), where pico-grams of anti protons are injected into a HEU target to induce micro-fission/fusion via production of neutrons.
The articles state that only a few milligrams of anti protons are needed for the entire mission (~500 tons in LEO puts a few hundred tons to Mars on a 45 day trajectory. ~120 km/sec delta-V!).
The amount of anti protons is entirely within reason; modest improvements in what we do today would make the entire mission's fuel in 1 year, so we only need ~18 month storage (for a 6 month duration mission; increase this by any surface exploration time past 30 days...), and they talk favorably about improvements in Penning traps & storage devices.

In any case, it's interplanetary applications where this is used, instead of getting to LEO.

I like the Sea Dragon for lifting things up (an entire ICAN or Orion ship lifted up to where it can fire the nuclear engine, for instance), but the Shuttle-C or Ares works, too.

Not dead yet. Posts sent on Sept 3, 4, and 5. I just can't get back as often as I might wish.

What does "Mars floor" mean?

"Phobos" wrote
> On top of that, with in situ propellant
factories and greenhouses on the surface, food,
fuel, and maybe water could be provided to the
spinning space station from Mars itself.

Not upwards. Upwards travel is difficult. If a resource is in hand on the planet, it's more valuable there, to be used for supporting exploration. Resources needed by the space base/hab are much more easily gotten in space, from space resources. As I said earlier, it's inconceivable that Martian reources could out-compete space resources.
Far more likely for a while, that the line would point downwards, with activities on the planet consuming stuff made in space. Any long-term base on the planet (where explorers might base from, during their tour on the surface) would certainly have fuel production, water if possible, but it's more likely that processed items (food maybe) would be dropped in from the space facilities.

> I think once enough habs and people have
been sent on the red planet something like this
won't be out of the question.

Why not at the start? is my point. Install the space infrastructure and profit making base ASAP.
Have profit flowing back into it and a livable hab (Fully shielded and full G) within a year of starting activity at/around Mars.
Send hardhat types first, to establish a habitable base and income immediately, then worry about bringing in dedicated trained explorers to crawl around turning over rocks. ("habitable base" meaning that people can live there with absolutely no concerns about radiation & gravity adaptation, and people on the surface are never more than a few hours and only a few km/s away from support)

Didn't see some other bugs with Mars Direct.

1) no escape system on the crew launch. Better to wait an orbit or 2 for the crew to meet the hab in LEO from a Soyuz or 2, than risk the roman candles with absolutely no hope for survival.
Read here about the Shuttle's rotten safety.

So use Energia or something without roman candles as a first stage. Plenty of ways around it. (Sure, the crew acccepts the risks, but I doubt anybody is selfless enough to risk that, when there are ways around it)

2) No experience with long term exposure to low G. Much is made of Shannon Lucid walking off the Shuttle after a long time on Mir, and other cosmonauts surviving even longer durations. Yes, they made it, but a decade later, they still haven't completely recovered.

I suspect that .38G for 3.5 years will make the crew either permanently crippled or long-term debilitated after they get back. It'll take far more than mice in orbit for 50 days to settle it, and I suspect that it will prove that low G is almost as bad as zero G. (I've got a couple of long-term bets on it) Face it: people who don't get much exercise just aren't as healthy. They'll have to exercise strenuously for several hours every day of a Mars Direct mission, and they'll still have serious long-term health problems.

Not saying this is a mission killer. There may be other data out there, and you may find a crew willing to do the mission. It is a big unknown, though.

Transplanting a sub-topic which started budding off in the "Energy Transfer" topic, this seemed to need discussion of its own, as a new sort of mission architecture.
Note the links I provided in that thread, as a background for why I feel confident with this proposal.

I don't either. I do know for a fact that it's far safer and more conservative to say that we do know for a fact that we can fairly easily provide full G for the crew, and that they'll be entirely healthy in it.
Nothing of the sort can be said for low G, and it'll be a long time before we're certain -a long time of space missions to find out, unless you're able to find a crew to volunteer to be highly paid for the remainder of their lives spent in therapy to regain their health. Even if they're not physically ruined by the long exposure to low G, they don't know if they will be, before they launch. You're going to have to pay them very well for the gamble, and run the risk of being known for using up a crew just for impatience and not being willing to do your homework.

This started when I talked about a modicum of space infrastructure around Mars' moons being better than dropping exploration crews on the planet, with no attention paid to space industry.
Mars Direct leaves in place a network of safe havens and exploration gear on the planet. This is great for exploring the planet, but a little effort on Ph&D does far more. Near-term profitability is the big one. Get tanks of water or other chemicals back to EO, and the missions are paid for right away, along with bankrolling the future of the Mars effort.
The infrastructure of the water factory at Ph&D is easily built up to a more complete factory (In the same timescale as 3-5 Mars Direct missions, let alone building any sort of semi-permanent base on the planet.)
Cable & rock dust for concrete (shielding and structure in one piece, far more robust and actually cheaper than the alternatives), and rolled & stamped metalsfrom sapce resources are used to build a base from tools & finely machined parts brought from Earth (Zubrin pointed out the difficulty of making something as small as a screw & nut; we bring along screws, and make the dumb bulk beams out of moon dust).
Settle for .38G on the way out, but the same habs are built up at the base, with extra truss length and strength for spinning newly shielded habs for full G.

The base isn't mass sensitive, so we build the bulky parts of the base from materials easily gotten in space, from the skeleton delivered by the transit habs.
Graphically showing my point, first for low G, unshielded habs:
habs = 5-15 tons, spin cable = ~3tons
now for Full G, shielded habs
habs = 750 tons, truss = 2500 tons
(SWAG, for ~Mars Direct sized habs. Feel free to pick the asumptions apart, but I doubt the picture gets any better than this.)
Far easier to bring along tools to build the larger habs from moon dust, especially since the same infrastructure provides profits for the Mars effort, as well as a strong support base for the exploration of the planet.

Now we've got fairly early sustained funding for the Mars effort, and completely livable conditions for long duration crew stays at/around Mars.

In private, it can be speculated that a mission could be done for even less. Maybe 5 bil or even 2. This is the price of the hardware at rock-bottom, with no inflated overhead, no mistakes, no fat. Who knows if this includes pay for the crew and everything else which goes on during the mission.

They say an elephant is a mouse built to government specifications. I'd say a diplodocus is the NASA version.
* Remember that McDonnel Douglass & the BMDO build the DC-X vehicle testbed in 6 months, for under 60 million. (that's million)
* Rutan & Scaled Composites built the Voyager (Round the world unrefueled airplane) for something like $3 million. Estimates for the typical government aerospace/defense contractor cost would be more like $150 million.
* Just after the start of Desert Storm, the USAF put out a request for a earth-penetrating "Bunker Buster". Less than 1 month later, the GBU-28 saw combat action!

OTOH, there's the example of the "Space Pen":
During the early days of manned spaceflight, they had to come up with a way to let astronauts take notes and mark checklists in space -in zero-G, ink won't flow down to the nib of a pen.
They spent $70 million, and developed the space pen. It's amazing: Writes upside down or in zero-G, writes under water or bleach or oil, writes on glass or anything else.
The russians used a pencil.

At the first Mars Society convention, former Gemini & Apollo astronaut John Young gave a talk. I don't remember what his topic was, but he glanced past solar panels.
The solar panels on Mir or Skylab or most satellites are great; Unfold them, point them at the Sun, and you've got power.
He said that the ISS has solar panels, too. Do you know what they need to produce power?

Software.

Byron wrote:

Forget about it. The beam for an SSPS system is about 1/10 the intensity of sunlight, and it's also in a freq which won't affect anything smaller than ~3 meters (a significant fraction of the wavelength). Buildings will be immune, as will people, airplanes, birds, etc.

Surface-based solar is limited by nightfall. Nuclear must be imported and soft-landed from Earth. Mars seems to be tectonically dead; Not enough geothermal heat to warm much more than a small pool of bacteria (hopefully, and that probably not near where we'd like to build a big base)

Go to Mars' moons, and finance the entire thing -including future Mars exploration by extracting water for shipment to Earth orbit (the answer to quesations about self-financing Mars exploration).
Build SSPS in Mars orbit, send down materials to roll out rectennae, and have ample power anywhere on Mars. Build the long-term Mars base in orbit, and have fully shielded, full Earth gravity habitation at Mars (which you can never have as easily on Mars itself).

Says who? I can point to lots of other studies which show exactly the opposite.

Get resources from an asteroid or Mars' moons, get any amount of energy you need from the Sun, move tonnages around cheaply, build large things fror use in space, or to be packaged for delivery to the surface, etc.

Tom Jolly wrote:

Right there is where most detractors of SSPS go wrong. Don't forget that the Space industry system is going to be self-financing after not too long (if it's not, then it won't be built) Asteroid metals are a big one, Geo-synch telecommunications arrays are the other: huge antennae and huge areas of solar power collectors will let a few stations cover the entire planet, and pick up a cel phone from the grond. All this will take is wire, concrete, and rolled & stamped metals -all easily produced in an early space manufacturing facility.
Fully 95%+ of the facility and the antennae farms are built from bulk space resources.
Bootstrap the capability, instead of the stupid idea of lifting an entire factory from the Earth -using the even more stupid idea of lifting the entire thing with the Space Shuttle! Here's one: "You want to build a city on Mars? Figure the city weighs a billion tons, and you have to lift it on the Shuttle. Then you have to lift all the chemical fuels to boost it to Mars, and soft land it on Mars, and your Martian city is clearly impossible"
That's the kind of modelling some (unnamed) people use to detract from the space industry concept.

only if you use the worst possible (or impossible or at least unlikely) assumptions. Change your models, and the entire outlook turns about.

Earth-based solar requires Earth-based industry; space industry eventually involves no pollution in the biosphere whatsoever! The only effect on the biosphere is the incident energy from the power beams. All other energy intensive and heavily polluting industry is done off-planet...
And that is the part where the potential of space infrastructure and SSPS comes out on top. (Not to mention it stops the need to burn oil, adding to the greenhouse; killing another of the straw men erected to argue against space industry & SSPS)

Not just a multi-planet species, but a space-faring species. Not just crossing space to drop down into another hole, but living in all of space. Far more than just one more tiny planetary surface to expand into.
Far more important to the long-term survival of the species and Gaia than simply plopping tuna cans down on Mars.

"Phobos" wrote:

Or nuclear or solar thermal. whatever works (ED tethers are nice because they're a workable version of "magic" propulsion -no propellant mass being thrown backwards!)

I'm not entirely sure we understand each other in mentioning tethers.
First, you cannot use tethers to lift 100 tons, or even 20 tons from the ground... We still are stuck with chemical rockets for that. I doubt ED tethers are even strong enough (with reasonable mass/thrust ratios) to lift from a sub-orbital trajectory before it re-enters on the other side. (If a first stage gets something to orbital height, but not quite enough velocity, then 1/2 orbit later the perigee will be too low, and you lose it. A spinning tether can exchange orbital velocity with a comparatively much smaller load, raising the load's perigee above the atmosphere.)
A momentum exchange tether station could concievably do it in one throw, but if you can build, launch, and operate one capable of lifting a 20, 100, or 500+ ton load from a hypersonic suborbital trajectory to a high orbit above the magnetosphere, then you don't need anything else, because you can work miracles.
You must get your load into LEO, and extend solar panels or fire up a nuclear plant to power the ED tether, for a gradual boost, probably taking days.

Forget about vaporizing the bomb pits, even in a worst-case accident. If the packaging split, spilling the bomb pits or complete pulse units, they'd fall harmlessly to the bottom of the ocean (they are extremely dense, well built objects, and they wouldn't be broken up in a typical launch accident)
If it's a one-HLV launch, with the NPR engine being fired at the top of an arc, the bomb pits are in the middle of a 580 ton chunk of ship, so they'd be recovered intact from the wreckage at the bottom of the ocean. We'll package them to survive if they're cargo on a booster (in the case of a multiple HLV boosted, LEO constructed ship.

Sure, we have examples of RTGs burning up and spreading radioactive debris. I'll argue that they weren't designed properly...
These were not launch accidents, but re-entering satellites. By definition, a booster acident involves much less energy, and properly designed RTGs would be intact at the bottom of a hole in the ground, even if falling from orbit. (Yes, a booster malfunction involves lots of energy, but very little of the energy of a rapidly burning cloud of rocket fuel goes into the payload. Comparatively, falling from orbit is more stressful...)
Anything threatened by radioactive leakage would already be crushed by this dense mass falling from the sky!
A water tank from Skylab survived orbital re-entry mostly intact.
The crew of the Challenger survived the booster malfunction and vehicle breakup. They fell for 2.5 minutes, and the impact with the ocean is what killed them (no parachutes, airbags, or basically any kind of survival possibility on the Shuttle).
Hitting the water is something a properly designed container could survive. (Especially if we launched the pits in a recoverable "escape module" with parachutes, airbags, or the sort. Plutonium is valuable enough to go to the effort.) Booster malfunction, fuel mass-combustion, range safety charges, and all, we could ensure the safe recovery of the bombs (easier than people!).

An Ares boosts 120 tons to LEO, or ~65 tons without the second stage. The 2SSME variant of the Shuttle-C is the cheapest, nearest term HLV we could get, and it lifts ~40 tons, so that means 20+ tons of protective packaging for the bomb pits.

Lightcraft are one. Up to the old ideas for flocks of 2 ton pods to a given LEO spot every 90 minutes or so. With a little bit of rocketry to circularize, they'd be a wonder.
Further advancement is offered by tethers.
They'd make a great upper stage either for a payload tossed up by something like a rocketplane or laser-thermal, or to lift the entire craft to LEO, as in the Hypersonic Skyhook. (Neither of these options is to be mistaken for the magic Beanstalk or synchronous skyhook. Momentum exchange and the

space elevator

are obtainable with today's materials.)

Frankly, I'm not too dismayed to be stuck with chemical rockets.

With only limited advances, we could revolutionise space access -if we revolutionise our book-keeping and procuring practices: Do NOT buy parts through government graft & contractor lobbying. Day-to-day space access should be privatised, and we'd see a marked decrease in cost.

If the Mars Society gets a mission going, then they'd provide this: Opening production lines and procurement practises for business and private interests without paying government overhead would be one of the greatest gifts the Mars Society could give to humankind!

To nuts & bolts, we all know about the Ares.

The Shuttle-C
is even more near-term, because the ET is unchanged; the only change is to toss the orbiter over to the side of a hangar somewhere. Next, get rid of the roman candles, in favor of

liquid strap-ons.

The Shuttle Orbiter isn't very good for crew launch anyway (it's manifestly unsuited for heavy lifting) Use Soyuz, or evolve to using something like the old HL-
http://www.astronautix.com/craft/hl20.htm]20
http://www.astronautix.com/craft/hl42.htm]42

Notice that one of Grumman/orbital Sciences' proposals for the new NASA SLI is this older spaceplane. (Scroll down to the N-G/OSI section).

Costs would drop, but safety & assured crewed access to space are paramount. (One of my problems with the Mars Direct is launching the crews on top of the booster, without even the Shuttle's unlikely possibility for escape.)

For another idea, there's the old Truax Sea Dragon proposal. 500+tons to LEO in one shot, cheaper than a Shuttle by far.
Just to show that re-usability isn't necessarily the way to lower costs.

Of Course, it would be nice to have an airplane you step into, it rolls down the runway, and takes you to orbit. (The old dream...) The Devil is in the details, of course.
Airbreathing is about the only way, which for now means jets of some sort. Eventually, they'll learn to make SCramjets, which will help, but for now, it's multiple engines for different regimes of flight.
Work on something like the Russian tripropellant rocket engines would be a step in the right direction, too.

For the true spaceplane, we almost need nuclear thermal for the upper stage portions of flight -where rockets would kick in. It may someday be possible to make a NTR airbreather (and make it safe enough that there wouldn't be hysterical fears of a "Chernobyl-like disaster"), but that's way out there.
For that matter, O2 afterburner NTRs would help, too. Increase the thrust, at the expense of some loss of EV, exhaust temperature, and ISP for the O2 being thrown out. Does that change the outlook for NTR spaceplanes?