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February 28, 2009

The Nuclear Orion Home Run Shot, All Fallout Contained


The typical analysis of the nuclear Orion external pulse propulsion rocket is to use constant charges (bombs) every 1.1 seconds to launch with people inside who experience 4Gs or less.

Nuclear Orion can achieve launch costs of less than $1/kg and perhaps a tiny fraction of that. This is 1000 to 20,000 times cheaper than current costs.

UPDATE:
Rand Simberg at Transterrestrial has written up a response to the series of articles that have been written here in regards to nuclear Project Orion and the one shot contained fallout variant that has been presented here.

Rand points out his excellent article about how small space payloads can be made cheap if they are sent up frequently.

The 1,000 times cheaper number that I have quoted is cheaper than the Russian Dnepr converted ICBM cost of launch to Low Earth Orbit. I know of no space launch system that is launching more than 6 times per year now and I believe the peak might have been about 20 times in one year ever for one kind of rocket that was getting some economies of scale.

At the end of this article I noted that "Idealized chemical rockets with total economies of scale could achieve $50/kg." However, no one is doing this and Rand is hoping that Virgin Galactic or other new space launchers can build up to that level by doing thousands of sub-orbital flights and building up with technology and business to thousands of orbital flights.

This site analyzes past underground nuclear tests and geology and nuclear energy to kinetic energy to show how the one shot launch will work while containing fallout and not creating an EMP.
END UPDATE

How much would the pulse units cost? Pedersen gives the amazingly low figure of $10,000 to $40,000 per unit for the early Martin design; there is reason to think that $1 million is an upper limit [for the smaller charges]. Primarily from strength of materials considerations. Whereas the Shuttle might carry thirty tons of payload, the pulse vehicle would carry thousands. If one uses the extreme example of spending $5 billion to build a vehicle to lift 10,000 tons (or 20 million pounds) to orbit, the cost if spread over a single flight is $250 per pound, far cheaper than the accepted figure of $5,000 to $6,000 per pound for a Shuttle flight


Also, the system proposed here can just be a true nuclear bomb powered cannon. Not a chemical cannon launching nuclear bomb projectiles but a nuclear bomb powered cannon. So the projectiles and the launches do not have wait until we have working Orion ships to fire. We can just fire Orion like shells with cargo. We can use existing nuclear bombs from the existing arsenals. Ideally you would want to optimize with the more directional nuclear blasts (Casaba-Howitzer still mostly classified) Therefore initial costs and development would just be the containment launch facilty and adding the cheap filler part of the pulse charge that will be directed by the explosion. The nuclear bomb powered cannon is the simplest launch system. It has no development risk that can achieve $1/kg launch cost or less. The only new things being built are the fallout containment (which is a simple dome with a hole in the center and some kind of sliding door) and the shell which is a big simple metal shell.

Here we will look at containing the effects of handful or even one charge where all of the fallout can be contained.

Fallout and Typical Orion
The explosions for Orion that occur in the magnetosphere where the magnetic field lines lead back to earth is where fallout will come back down and be a problem.

We have already studied that reducing the fission component of any bomb and getting to higher fusion purity greatly reduces fallout and also a north pole launch reduces the fallout that returns to earth. Having a pile of conventional explosives for the first pulse also helps since the ground contact explosion is messier than the air bursts.


It would also seem best to send it up during a snow storm which would contain the fallout that coincides with a solar storm that flattens out the magnetosphere.

If you could not make the pure fusion bombs, which has not been done yet then another way to further reduce the radiation is for an unmanned high-G sprint start to a point outside the magnetosphere zone.

Another method is to use a large all chemical rocket that is able carry a smaller Orion into space where it is safe to light up the Orion.

The Toss and the Home Run shot
An unmanned Orion asteroid interceptor was designed. It would not need shock absorbers. Artillery arming, fusing, firing system for shells are regularly built to take 1000 Gs.

There was a three page paper: Nuclear explosive propelled Interceptor for deflecting objects on collision course with Earth. Johndale Solem, Los Alamos, proposed unmanned vehicle. No shock absorber or shielding. The pulse units were 25kg bombs of 2.5 kiloton yield for 100G acceleration of a 3.3 ton Orion. So an unmanned nuclear Orion can survive very high G forces. A single 25 kiloton yield would accelerate 3.3 tons to 1000Gs. A 2.5 megaton yield would accelerate 330 tons by 1000Gs. 25 megaton yield would accelerate 3,300 tons by 1000Gs. The highest acceleration had 0.4 seconds between charges so to get up to speed two or three charges might be needed to get 1.2 seconds of acceleration. Earth escape velocity is 11.2 km/s. 1000Gs is 9.8km/s**2. A structure can be built that can contain the fallout from one or a few bombs.

The tee up or toss. A toss would be to use a stack of chemical explosives to get the projectile moving a bit and clear of the ground when the nuclear charge goes off. A nuclear airburst has less fallout than a ground detonation. A tee-up would be to build a tower and have the projectile at the top and the nuclear charge at the proper distance below. Obviously the tower is utterly destroyed. Also, note that the initial charge or two would not count against any projectile or rocket cargo. It would always be outside.

We could also size the projectile so that we go at about 1.5 times the earth escape velocity so that it is a straight shot into the moon. The metal projectile designed to also survive the lunar impact. Ta da cheap cargo delivery to the moon.



Containing the Fallout


Please review the chart (click on pictures for a larger image) with the effects of different size nuclear explosions. Notice that the air eventually stops the nuclear explosion. The fireball stops after 1.1 kilometers because of air. The Orion tests showed that metal with ablative oil can be a few hundred feet away and not be damaged. The ablative oil vaporizes and takes care of the ultraviolet and soft x-rays. The metal has to be big enough to absorb the heat and not get to its melting temperature.

UPDATE:
The later articles that I have written indicate that an underground launch would contain most of the fallout and all of the blast. Any optional dome would be to capture any fallout that leaks from underground.
END UPDATE

You can build something bigger and relatively more flimsy or something smaller and tougher. The deciding factors are cost and cleanup and possibly maintenance.

Looking at the 10 megaton explosive the fireball radius is 1.1 kilometers. So something that is closer than that has to be able to withstand the fireball. We are talking about building Orion so we can make elongated Dome out of pusher plate material with a slathering of ablative coating on the inside. So contain it just like the pusher plate. It would need to be a few hundred meters wide. You would have a hole at the top for the Orion to pass through and doors that would slide into place to contain the fallout. Afterwards you clean up inside after things have settled and cooled.


Buckminster Fuller had designed geodesic domes that were 2 miles wide and 1 mile high. These would need to be able to withstand about 20-40 PSI. The materials exist to make such a structure.


A thin polymer film with thickness of 0.05 – 0.3 mm. The film is supported at this altitude by a small additional air pressure produced by ground ventilators. The film mass covered of 1 km**2 of ground area is M1 = 2×10**6 m**2 = 600 tons/km**2 and film cost is $60,000/km**2. Covering a diameter 20 km is 314 km**2. Area of semi-spherical dome is 628 km**2. The cost of Dome cover is 62.8 millions $US. The total cost of installation is about 30-90 million $US. There are large air supported strucures now of about 215 meters in diameter.


Scaling up would not be that difficult. More material and larger ventilators. Plus before the Orion went up and set off charges you would under-inflate so when the extra-pressure came it would use up some of the force inflating the thin film cover. There would need to be some flap or cover to go over the exit. If it was cheaper one could pack up the big bag afterwards for processing as opposed to cleaning up on site.

With the fallout contained then it is possible to re-use the facility or the method for multiple clean launches.

The Explosion that Goes to Pusher Plate or Metal Containment
The Orion explosive charge has a nuclear bomb and propellant filler. The explosion is configured to send 85% of the force towards the pusher plate (or the projectile). The explosion compresses the propellant slab to 1/4 of its thickness. This expands as a jet of plasma at 150 km/sec (300,000 mph). 300 microseconds later the expanding propellant cools to 10,000 degrees (one electron volt). In another few hundred microseconds the cloud hits the pusher. For less than a millisecond the stagnating propellant reaches 100,000-120,000 degrees. In space the cloud would be invisible until it hits the plate and there is an intense white flash. The 15% of the force that is going to the walls of the containment will be going a bit further in the case where we have thick metal walls containing the remainder and the fallout.

The key was how opaque the ablative oil is. The more opaque the better it protects the plate (and the walls) 100,000 degrees is a good range for opacity. It is ultraviolet and soft x-ray. The more opaque the less the radiation eats into the surface. Then the pusher and the containment have to be large enough so that the heat can be absorbed without melting the whole mass of metal.

In the case of the home run shot. Even if some of the plate is eroded it does not matter because we only need to protect the cargo for the one hit and transport into space. After which we just need enough left so that cargo does not leak out.

Nuclear Bomb Powered Cannon
This mode of operation could start within 2-3 years. Just build the simple facility Dig a hole to blow up the bomb underground to contain the fallout. Requisition a nuclear bomb from one of the arsenals. Up to 150 kilotons for the first test, so that international discussions are optional [Threshold test ban that limits underground tests to 150 kilotons or less is the only ratified agreement in force]. Make a big metal projectile with ablative oil slathered on the bottom and tee it up. Talk a bit to the other nuclear nations, get some signoffs and light them up and start the space age. Get water, fuel, food, any hardened electronics and any other tough supplies up and available for the crews in chemical rockets to get.

Chemical fuel depots would be setup at the low cost of less than $1/kg. Supply depots as well. No chemical rocket would need to take any supplies that can take more than 1000Gs. Chemical rockets can take a lot more material about ten times more cheaply to low earth orbit than to geosynch. So the nuclear supply cannon would lower the cost of chemical rockets by over ten times by supplying fuel depots. You can also launch carbon nanotube tethers or other polymer tethers for space elevators. You can launch Uranium and metal and other materials to build Orion rockets in orbit or on the moon. You can launch certain thin film or polymer solar cell material (just have to make sure it is the kind of material that can take the strain and leave out the components and structure that cannot take the stress)

Also, the nuclear bomb powered cannon of simple projectiles can be located anywhere since there is no constraint to get the projectile out of the magnetosphere. You would never have a nuclear light up of the projectile.

You would need to size the projectile to reach orbital velocity with an extra margin for air resistance. Plus you would need some small propulsion at the top to circularize the orbit so that it did not still fall back down.

The Nuclear bomb cannon is so simple that it has almost no problematic failure modes. The initial shot - you know you are lighting up a nuclear bomb. If the bomb is a dud then the shot goes almost nowhere or falls short. You launch with a flight path over the ocean. You are slathering on the ablative oil before you light up. There is no pump issue for repeated shots. If the pusher plate has a problem, well you are launching supplies or hardened equipment so you may lose the payload. There would be no people lost as it is unmanned.

You have the benefit of taking one stockpiled nuclear bomb out of the stockpile for peaceful purposes. Plus there is benefit of starting a real space age.

FURTHER READING
Fallout and EMP analysis and pictures of Project Orion

Photos and video of project Orion and super-orion.

The history of above ground nuclear tests

United States 216 tests from 1945-1962 for a total of 153.8 megatons
U.S.S.R. 214 tests from 1949-1962 for a total of 281.6 megatons
United Kingdom 21 tests from 1952-1958 for a total of 10.8 megatons
France 46 tests from 1960-1974 for a total of 11.4 megatons
P.R.C. 23 tests from 1964-1980 for a total of 21.5 megatons
South Africa 1 test 1979 for 0.003 megatons

So would it be "crazy" to set off nuclear bombs even if ALL of the fallout was contained for purposes of starting a true space age. As opposed to the 500 bomb explosions that were done in the atmosphere before for geopolitical and military posturing.

Chemical space program deaths about 300 (astronauts and civilian

Deaths from nuclear weapon tests. No direct deaths. If that is what you are planning for then you are careful and make sure everyones stays out of harms way and you can for months and years in advance to contain the effects.

Laser array launch details. $2 Billion and five your program to get to 100MW sounding rocket.

Previous list of favorite space launch systems, with many not yet feasible. Even an Inertial Electostatic fusion [which does not work yet] single stage to orbit would have projected costs of $27/kg.

Space elevators which do not exist and might not work and are unlikely to be developed before 2030 have initial projected costs of $220/kg which would then fall possibly to $10/kg. Idealized chemical rockets with total economies of scale could achieve $50/kg.

This system is 10-50 times cheaper than idealized systems that might not work and would likely take decades to develop.
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