Orion safety in atmosphere

Date: Mar 19, 2005

Orion safety in atmosphere

Date: Mar 19, 2005

Fallout is the heavier matterial, like dirt, that has been picked up by the blast, pulled into the fireball, heavily irradiated, spewed out of the mess, and finally allowed to drop again. Simply put, if the fireball doesn't touch the ground, you don't have to worry about fallout. Tho if you are close enough and within line of sight, a standard nuke would send a wave of high energy particles through you that could cause some damage. Tho it's only a matter of degree, the same type of stuff goes through you every day in smaller quantities.

And the ground blast is relatively simple to take care of also, as the Orioneers showed. Use a small island as the launch pad, (or do a sea launch, but thats harder) and coat (or plate) all non-water surfaces of the island with steel. And the pulse units don't even have the standard, near uniform, blast shape that regular nukes have, instead they have a shape that causes most of the fireball to turn some plastic (or some such fuel thing) into plasma and shooting it at the Orion causing most of it to not go anywhere near the ground while it was still in any shape to mess things up that way.

Easy place to get enough basic data, if you don't wan't to actually go to the effort of learning enough physics to understand it, is some of the old Department of Civil Defence books. They had plenty of data, (taken when it was still fresh) and are written simply, tho they are based on stuff like the Linear No Threshold method of determining dangerous amounts of radiation.

http://www.oism.org/nwss/index.htm

Nuclear War Survival Skills Updated and Expanded 1987 Edition
Cresson H. Kearny With Foreword by Dr. Edward Teller

Original Edition Published September, 1979,

by Oak Ridge National Laboratory,

a Facility of the U.S. Department of Energy Published by the

Oregon Institute of Science and Medicine

Cave Junction, Oregon

john fraz · Veteran Member

Some fallout is the remains of the "combusted" plutonium pit of the bomb's primary. If we're talking about any sort of nuclear explosive as it's currently understood and practised, this is unavoidable.
I'd have to check, but you need around a kg of fuel to trigger a fission release, and that minimum is absolute. All that turns into nasty various fission products, all of which are vaporized, and mixed with vaporized particles of the bomb casing and structure, to be carried up into the mushroom. Ground bursts are worst, just because of the extra material available to mix it with.
A ~.1kt explosion is very tiny, compared to what we think of as the huge towering mushroom cloud, but as stated here, the ship leaves a trail leading upwards. (some hundreds of these, for the climb to orbital altitude, before the turn and burn directly to an interplanetary trajectory. That's several hundred kg of transplutonian metals and stuff released within the atmosphere.)

Freeman Dyson wrote that they'd established that an ambitious interplanetary program using big Orion ships (more, bigger bursts) would have added only 1% to the fallout we were putting into the atmosphere with all the atomic testing going on. Still, that's too much.
To me, the only hope (slim, at that) for a big ground-launch ship is the possibility of "clean" bombs -something that doesn't burn heavy radioactive metals. Even a micro-fusion burst involves neutron bombardment of propellants, any sacrificial or ablative materials involved and structures.
As long as whatever is released won't hurt anything, possibly we can get around it. Others who know more please check me: What sort of reaction can we use for the primary which excites the propellant? (big question, I know)
Neutron bombs are a clue, maybe, since they produce very little prompt or lasting particulate fallout. All the energy is concentrated into the prompt neutron release. If there's no one within harm's way, does fission product fallout matter? (Does a tree make a sound if there's no one to hear it being felled?)
Maybe there's some hope of a prompt nuclear burn reaction that only sprays out the really nasty products (the ones that cause immediate radiation burn symptoms and the immediate casualties, if they're released over a city) we do this out over the equatorial ocean, where it's at least several hours before any of it can be deposited anywhere sensitive. By that time, these very worst poisons will have already decayed into longer lived things, that are practically harmless.

If there's a nuclear attack, avoid breathing for at least 12 hours (the longer the better); the worst stuff -what'll kill you quicker than cancer 20 years down the line- burns off quickly. All bomb/storm shelters need overpressurization, if they're to protect against NBC threats. (a little -hopefully useless- advice)

I'll start another thread about a floating spaceport and launch structure for sea-launched big Orion ships. I don't at all share the doubts about building and floating around a platform with stand-off launch support towers. Sea launch is the way to go.

-- Edited by john fraz at 04:10, 2006-08-26

Martin Schwingenheuer · Member

I suppose,ORION start of Earth is only possible far far away of all populated areas.I think Antarctica would be the only place to start,because only a vertical start on Earth´s rotation axle is suitable due a possible start failures.When bomb sequenses stops,gravity will catch the ship and it comes back also vertical.Paracutes and a landing rocket system could damp the emergency landing.The pusherplate should sepperate before an emergency landing.We have to calculate a possible fail of a mission,the mini fission(or better fusion) bombs must be safe all times against an accident and terrorism of course.We had pointed out it´s complicated to build very small fission bombs in the moment.Where we get mutliple tausend of 1-5KT bombs from?How is the behaviour of it stored together in ORION`S storage device?A SRB start like at the video would be the best to avoid primary radioactive contamination of the start facilities and the atmosphere.But a rest is always comming back as falloud,catched by gravity and earth´s magnetic fields.I can only estimate and hope that the magnetic field is able to transport chaged particles to north or south poles away of our populated areas.If we could build mini fusion bombs,antimatter or laser iniciated it would be more safe,cheeper and reliabler of course.

Martin

Philipum · Veteran Member

john fraz wrote:

...you need around a kg of fuel to trigger a fission release, and that minimum is absolute. All that turns into nasty various fission products, ...

I think that only a small fraction of the fissile material is actually consumed in the explosion (it expands so quickly that the chain reaction stops well before everything is burned). It is true, though, that a certain amount of fission products is released, but the consequences of that are far to be catastrophic.

10kBq Jaro · Senior Member

Philipum wrote:

john fraz wrote:

...you need around a kg of fuel to trigger a fission release, and that minimum is absolute. All that turns into nasty various fission products, ...

I think that only a small fraction of the fissile material is actually consumed in the explosion (it expands so quickly that the chain reaction stops well before everything is burned). It is true, though, that a certain amount of fission products is released, but the consequences of that are far to be catastrophic.

No, the minimum is not absolute. But problems arise in terms of the time available for the fission cascade to develop, when you try to increase density by a greater implosion compression of a smaller mass (in order to maintain the required super-critical multiplication factor). This can be shortened by using antiprotons for triggering the cascade, because each one can yield approximately 16 to 18 neutrons on impact, instead of the usual 2 to 4 for U235 or Pu239 fission. A fission-fusion "boot-strap" mode of operation also helps in reducing fissile mass, as the 14MeV neutrons from fusion reactions are much more efficient in causing fission.

Philipum is right about the non-catastrophic nature of the resulting radiological risk. But there is the worse problem of perceived risk, public fear and political roadblocks. Clearly, no amount of fallout reduction will make Orion-type ground launch acceptable any time in the forseable future.