New Mars Forums

I suggest you look into some of the Big Dumb Booster scenario work for some rough estimates of cost.  You could probably get a factor of 10 drop in cost/kg compared to conventional turbo-pump weight optimised high technology.

Reusability is not neccesarily a prerequisite for low cost access to space.  A steel coke can is not reusable, but can be produced for a pittence because its engineering is simple, it is produced from simple materials and they are produced by the million.

How long is a piece of string?  The space shuttle is expensive largely because is packed full of unneccesary technology and is based on the false assumption that a space vehicle should look like an aeroplane.  It uses over complicated engine technology, unsuitable liquid hydrogen propellant and was basically a public works project.

Using a 2 stage low-carbon-steel oxygen/kerosene 'firework', with simple ablative lined pressure fed engines, it could all be done relatively cheaply.  The lower stage could be made reusable, by splashing it down in the ocean following use.

Bed rest provides a good simulation for the decay of the body under weightless conditions.  Most people recover from extended periods of bedrest, but muscletone deteriorates quite rapidly, begining within 6 hours or so.  My girlfreind wrote her final year dissertation on the effects of microgravity on the human body.  Eighteen months in 1/3rd g certainly won't be a death sentence, but will result in varying degrees of muscle loss which may take some months to recover from.

Lunar and Martian conditions will clearly be less severe than microgravity.  Martian gravity may be sufficient to prevent severe deterioration of the body if a modest amount of exercise is taken each day.  This would become an integral part of Martian culture.  Generally, a sedentary lifestyle can be expected to have more severe consequences on Mars than on Earth.

Paraterraforming will begin as soon we begin a long term presence on another planetary body, probably with the first Martian base.  Immiediately, it will be neccesary to make use of sunlight to grow crops and inflatable domes are the obvious choice.  As the need for food expands so will the domed areas.  Eventually, people will want to live and work on the surface and domed cities will be built.  By the time terraforming proper begins, large areas will already be paraterraformed under inflatable domes.  Thickening the atmosphere will simplify and cheapen the process.  Simple economics and timescales suggest that Mars will be heavily paraterraformed, long before it reaches anything like an Earthlike state.

All atmospheric retention methods are likely to be highly imperfect on Ceres.  The biosphere would require occasional topping up with fresh gas, just as the Earth does.  The question is, would leakage rates from a 0.1-1tonne/sq metre column density physically contained atmosphere, exceed those of a 100tonne/sq meter magnetically confined atmosphere?

The problem with any sort of roof world is that it is exceptionally vulnerable to damage and very difficult to engineer in a safe and sustainable way.  Even relatively small impacts would tend to be disproportionately destructive and it would be very difficult to protect a 1000km diameter world from all impacts with the sort of reliability that one would need to create a biosphere on geological timescales.  Multiple independent cells would work much better than a single world house, given that each could be seperated by a barrier of vacuum.  But then we should ask the question as to why the cells need to be on Ceres in the first place?  Why not just build self-enclosed colonies in space and use rotation to produce whatever gravity you need and mirrors to provide however much sunlight is needed?

Any form of natural terraforming even with the aid of super-strong magnetic fields, would be extremely expensive on Ceres.  There are uncertainties as to whether it would work at all and the value of the land created under such a deep and poorly transparent atmosphere is open to question.

I think the same will end up being true of many other potential terraformable worlds.  Some of the icy worlds in the outer solar system have gravitational fields considerably deeper than Ceres.  But these worlds would be constrained to being as cold as Siberia, even with the aid of significant artificial illumination.  Soil would be available in limited quantities from meteorite dust, but ambient temperatures would be far too low for anything to grow.  Holding capacity of the land would be low at best.  So we come back to growing things in greehouses under artificial conditions, not really a great step forward from having domes on a non-terraformed world.  Again, it is difficult to see how the value of the land could ever justify the cost of carrying out such an enormous terraformation effort.

At this point somebody usualy chirps up that a terraformed iceball would be sustainable on geological timescales whereas man made space based habitats would not.  But it is questionable whether a terraformed dwarf planet would really offer that many advantages in terms of endurance to catastrophe.  A large impact would devastate any ecosystem established on the world, kill the vast majority of people living there and would very likely blow away a significant portion of the atmosphere.  And we shouldn't forget that most such worlds will require considerable human maintenance to maintain life permitting conditions.  A terraformed Triton or Pluto would need artificial illumination as a substitute for sunlight (which is only 10 times brighter than moonlight at their distance from the sun).  Could we engineer such a complex system to be invulnerable to catastrophic impacts on a geological timescale?

A large impact would very likely destroy an O'Neill habitat in its entirety.  But the fact remains that we would not be living in just one such habitat but thousands or millions.  As such we have a large degree of redundancy.  The bottom line will come down to cost.  Do we spend x producing y square miles of tundra or the same amount of resources producing a far larger quantity of far more desirable land?

Ceres equatorial illumination levels are 0.075kwh/m2/day.  That is comparable to winter illumination levels in England.  Crops will grow under those conditions if provided with adequate water and optimum temperatures.  But growth is generally retarded by lack of light.  Further from the sun than Ceres and sunlight becomes too weak to be of great value.  Even at Ceres distance, the productivity of the ecosystem would be low and would become zero abovce a certain latitude.  So the holding capacity of Ceres would be much smaller than an equivelant amount of land on Earth, or even on Mars.  Yet the difficulty of terraforming ceres might be an order of magnitude higher.

I realised today that a roofed world would be exceptionally vulnerable to impacts.  A large explosion on the surface, would send shockwaves through the atmosphere, ripping off the iron roof hundreds of kilometres from the impact site.  So a roofed world house isn't really a sensible option.  This would also be a problem for sealed O'Neill type colonies.  As a metoer passes through the outer shell, it would compress the air within the habitat and fracture the hull.  Rather like a bullet passing through an apple, the meteor would not leave a neat hole.

A good analysis.  At ionosphere heights, the average speed of the ions will greatly exceed those of ordinary atmospheric gas molecules, so the situation is even worse than you've suggested.  The only thing constraining gas molecules from escaping is collision with other gas molecules.  The atmosphere would evaporate like a pan of boiling water.  But, only the molecules at the top of the atmosphere have a free path, so the whole process would take time and the species escaping would be ions.

A magnetic field would trap the ions and they would spin along the field lines until they reenter the atmosphere at the poles.  Another potential problem is the temperature of the ions.  Ions within the upper atmosphere tend to thermalise through collision with other ions and gas molecuiles which keeps their average temperature relatively low.  As escaping atmospheric ions spread out across space, they would absorb energy from solar wind particles and UV.  This will increase their average temperature far above that of the upper atmosphere.  As the ions spiral down the magnetic field lines and reenter the atmosphere, they would reemit their accumulated energy as heat and light.  If the catchment area of the ions is too large, they would emit enough stored energy to create a serious problem for anyone or anything living on the surface.

For outer solar system worlds that happen to be a long way from the sun, the magnetic field provides a convenient mechanism for increasing their catchment area to solar radiation.  For Ceres, with a solar intensity ~1/9th that of Earth's it could end up litterally frying the place.

Atmospheric escape from a body like Ceres would not happen in a split second.  Gas atoms/molecules in the lower atmosphere would be constrained by collision with the molecules above them.  A gas atom must have a free path in order to escape.  We can therefore expect the atmosphere to slowly evapourate, with ions gradually escaping from the ionosphere.  The atmosphere would thin over a timescale of centuries.

Given that most of the species escaping reside within the ionosphere prior to escape, we are talking about the escape of ions rather than neutral gas molecules.  By surrounding Ceres with a magnetic field, the escaping ions can be trapped and will eventually spiral into the polls of the magnetic field re-entering the atmosphere.  Hence the atmosphere is recycled continuously.

Using a magnetic trapping, even relatively small bodies can be made to hold dense atmospheres for geological timescales.  Ultimately, for very small bodies, the mass of atmosphere required to produce a breathable surface pressure would exceed the mass of the body being terraformed and you have a mini gas-giant.  For Ceres for example, a mass of gas equivelent to 1% the mass of ceres would be required to produce a 1 bar surfcae pressure.  For asteroids just 300km in diamter, the mass of the atmosphere would be 30% the mass of the asteroid.  For a body like Phobos, the atmospheric mass would greatly exceed the mass of the asteroid and atmospheric radius would greatly exceed the diameter of phobos.  So there are clearly practical and economic limits to the size of body that can reasobaly be considered terraformable without tented enclosures.

In principle, most large moons and asteroids with diamter 500km> could be given oxygen atmospheres and could be made to hold onto those atmospheres for geological timescales.  Whether this will ever be practical and economic is another matter.

I gave some thought to the idea of terraforming icy worlds.  Basically, there is no way of doing this that does not involve planetary engineering on a scale that would dwarf anything required in the terraforming of Mars.

We would need an atmosphere with a much greater column density than Earth's and this would need to be manufactured from local ices.  Sunlight at that distance would be too weak to be useful in driving any meaningful ecosystem.  We would therefore need artificial illumination of the whole planet.  If this took place at ground level, the upper atmosphere would remain at about 30K and this would greatly reduce the problem of atmospheric escape.

The existing surface is ice and would melt if brought to Earth temperatures.  One way around this would be to cover the entire world in several metres of crushed rock and dust.  The surface temperature of the world could vary greatly over the year, but as long as the average temperature remained a few degrees below zero at all locations, the icy mantle under the thin crust would remain solid.  This would allow warm summer temperatures so long as they were matched by bitterly cold winters.

We could raise average temperature above freezing if it were possible to use heat pumps to cool the upper mantle.  An enormous pipe network would carry brine into giant heat pumps at a temperature of perhaps -10C, with an exit temperature of perhaps -12C.  Heat pumps would reject heat at a temperature of perhaps 10C.  We could even allow portions of the crust to melt and form seas in some locations.

Given that virtually any solid-surface world could be terraformed using magnetically confined ionospheres, it would be interesting to explore the parameters of using this technique.  For instance, Ceres has 2% of Earth's gravity and 0.7% its surface area.  So terraforming Ceres to 1 bar at the surface would require one third of Earth's atmosphere to provide less than 1% of its land.

At what point does it become no longer worth it?  It would also be interesting to model the properties of an atmosphee with 50 times the earth's column density on a world with 2% earth gravity and less than 1000km in diameter.  How much light would get down to the surface and waht would the structure of the atmosphere be like?  Would we get terrible winds in the upper atmosphere?

Weapons grade materials are expensive compared to everyday industrial materials, but are cheap for the amount of energy that they release.  Pulse units could be produced for as little as a few hundred thousand dollars each if mass produced, with perhaps a couple of hundred needed to reach orbit.  The total cost of the pulse units would be in the region of $100million per launch.  This sounds expensive, but when viewed in the context that each launch will lift tens or hundreds of thousands of tonnes of payload into orbit, it is actually very cheap relative to the cost of chemical rockets.

Building Orion bigger and using fusion pulse units would further reduce per unit costs and per unit radioactivity release.  The cost of adding a tonne of explosive yield to a fusion device is measured in cents, not dollars!  Unless and until the development of Polywell fusion, Orion remains the most cost effective means of lifting large payloads into Earth orbit at an affordable cost.

The problem of radioactivity release is best viewed in terms of cost benefit analysis.  Most of us accept that road vehicle emissions are harmful to health, cause lung cancer, heart attacks and aggravate cardiovascular disease.  Cars themselves inevitably cause thousands of fatalities each year as a result of road accidents.  The mature way of looking at this is that we do what we can to minimise emissions and accidents, but we accept that a certain number of fatalities and injuries are unavoidable (or exceptionally difficult to avoid) as a result of using cars to get around.  Given the benefits that we get from cars and given that the cost of reducing fatalities and injuries beneath a certain threshold would be excessive, we judge that the number of fatalities each year is tolerable (though never strictly acceptable), when weighed against the benefits we receive and the cost of further reduction.  This is exactly the sort of trade-off that must be applied to all of the technologies that we use and the problems that we face in life.  The same thought-process must be applied to the use of fossil fuels generally and their global warming potential.  We accept that these fuels do cause damage through global warming and have other undesirable consequences.  But we must balance the benefits we get from using these fuels against the damage that they do and the cost of NOT using them.  We may decide that the consequences of using the fuels are too high and spend money reducing CO2 emissions or mitigating the consequence in some other way.  In some cases, the cost of reducing CO2 emissions will be disproportionate and the benefits of using the fossil fuels very high (air travel).  We may decide in this case that the risk (or damage) is As Low As Reasonable Practicable (ALARP) when weighed against the benefits that they bring us.  In terms of direct risk, we each accept a 1 in 10 million chance of dying every time we step on an aircraft, in exchange for the benefit of rapid transcontinental travel.  This risk translates into real fatalities in air crashes each year (including people on the ground), which we similarly accept because of the benefits that we as a society gain from air travel.

Orion should be looked at in the same way.  Launching an Orion will release some radioactivity into the atmosphere.  Some of this activity will reach the public and will slightly increase the amount of radiation that they receive each year (in addition to natural sources, legacy fallout and medical X-rays).  This will presumably result in a small number of additional fatalities each year.  The public must weigh this consequence against the benefit that they as a society receive from using Orion as a launch vehicle.  If the benefits are very high (as they clearly are) and the consequences small (as they are) then we should use Orion.
We can invest money reducing the radiological consequences of Orion.  We can build remote launch sites in polar regions, which will reduce the fallout over inhabited areas.  We can research ways of making cleaner bombs that reduce fallout.  We can consolidate launches into larger ships, which use fusion powered devices with less fallout per kg delivered to orbit.  All of these things would cost money and the benefits should be weighed against the cost, just as is done for other technologies that we use.

What many greens appear to be saying is that it is totaly unacceptable to release any radioactivity for any reason.  If I applied that same logic to road vehicles, I would have to ban cars all over the world because of the enormous risk that thye clearly pose.  I would never be able to use electricity because of the risk of electrocution.  I could never use fossil fuels because of the damage to the environment.  And I could sit happy in the knowledge that I was risk-free and environmentally pure and starve and freeze to death.

How would you get the iron out of the star in the first place?  the surface temperature of the sun is 6000+degC.  Even low mass red dwarf stars have surfcae temperatures exceeding 2000degC.  Extracting material from a star would also mean braving intense radiation fields.  The investment of energy would also be large, given that even the smallest stars have masses 13 times that of Jupiter.

My guess is that a civilisation would need to be seriously short of raw materials before going to this much trouble.  If materials really are that valuable and expensive, it would be FAR cheaper and more efficient to build small rotating colonies, with physically contained atmospheres (ie, O'Neill type colonies).

Using gravity to hold down the atmosphere of an artificial world, is a very material intensive way of creating habitable area.  This is simply because gravity is such a weak force and you need a great deal of mass to create significant gravity.  For every square metre of land on Earth, there are 10million tonnes of raw materials.  That's an awful lot of material for just 1sq meter of land.  Building a habitable world in this way would be unimaginably expensive, especially if all the material required has to be lifted out of the full depth of a star's gravity well.