List all weapons of SDI ?

[Dilandu]

It depends on the situation. If the bombs are in space far away from the earth's atmosphere, I agree. However, if the bombs were detonated within the earth's atmosphere, then the consequences of radioactive fallout being carried to population centers is not a perfectly desirable outcome even though the nuclear explosion was far away.

Erm. If the bomb detonated above surface - so the fireball did not touch ground - there would be no or almost no fallout. Fallout is caused by nuclear fireball reaching the ground & dragging in massive ammounts of matter, which is then irrdadiated by intense neutron flow. If the nuclear fireball did not reach ground, then there is next to nothing to irradiate.

 

[martinbayer]

I readily admit to having deliberately added volatile fuel to this particular dumpster fire discussion, but what, if any, actual documented hardware ever came out of SDI?

 

[bcredman]

Erm. If the bomb detonated above surface - so the fireball did not touch ground - there would be no or almost no fallout. Fallout is caused by nuclear fireball reaching the ground & dragging in massive ammounts of matter, which is then irrdadiated by intense neutron flow. If the nuclear fireball did not reach ground, then there is next to nothing to irradiate.

To significantly reduce radioactive fallout from a nuclear explosion, the detonation needs to occur several kilometers above the ground, typically considered to be a "high-altitude burst," with the exact height depending on the yield of the bomb, but generally exceeding 5 kilometers (around 3 miles) above the ground level.

Nuclear explosions at lower heights above ground and at ground level would generate radioactive fallout to which I referred in my post.

 

[bcredman]

I readily admit to having deliberately added volatile fuel to this particular dumpster fire discussion, but what, if any, actual documented hardware ever came out of SDI?

While the Strategic Defense Initiative (SDI) did not result in any fully operational, deployable missile defense system as originally envisioned because the SDI program was canceled in 1993 by President Bill Clinton, some limited hardware prototypes and technologies were developed during its research phase, including experimental laser systems, advanced tracking radars, and early versions of kinetic kill vehicles, though none were ever fully implemented or deployed due to technological limitations and treaty concerns. See previous posts in this thread for specific SDI experimental projects that tested specific prototypes for examples.

After cancellation of SDI, starting in 1994, a scaled back version of the SDI program was carried on by the Ballistic Missile Defense Organization (BMDO) using the previous research results from SDI. BMDO retained and developed the SDI principle of hit-to-kill interception of nuclear missiles with other non-nuclear missiles. In 2002, the BMDO became the Missile Defense Agency, and MDA scientists and engineers continued to research and develop hit-to-kill technologies and later to test and field elements of today’s Ballistic Missile Defense System, which includes:

-- Networked sensors that include space-based sensors, and ground- and sea-based radars to detect and track targets;

-- Ground- and sea-based interceptor missiles to destroy a ballistic missile using the force of a direct collision -- hit-to-kill technology -- or an explosive blast fragmentation warhead; examples of such systems currently deployed are Patriot PAC-3, Aegis BMD, THAAD and the Ground Based Interceptor (GBI); and

-- A command, control, battle management and communications network to give operational commanders links between the sensors and interceptor missiles.

The Next Generation Interceptor (NGI), designed to eventually replace the aging Ground-Based Interceptor (GBI), is currently in development with Lockheed Martin as the prime contractor, aiming to be fielded by 2028.

 

[Scott Kenny]

If both sided had the neutrino beam weapon and used them to detonate each other's nuclear weapons stockpiles, the result would not be much different than an all out global nuclear war.

Worse, actually, because every nuke would be a surface blast, generating the maximum possible fallout.

what, if any, actual documented hardware ever came out of SDI?

Several really big lasers, though the most famous one (MIRACL) had absolutely terrible spot size.

I think the THAAD radar came out of SDI, though I'm not sure about THAAD proper.

IIRC the single best part of SDI was the SM3 KKV.

 

[Dilandu]

To significantly reduce radioactive fallout from a nuclear explosion, the detonation needs to occur several kilometers above the ground, typically considered to be a "high-altitude burst," with the exact height depending on the yield of the bomb, but generally exceeding 5 kilometers (around 3 miles) above the ground level.

This depend mainly of fireball size. The Hiroshima detonation, for example, was on about 600 meters altitude - and there were no long-term fallout to speak about, because nuclear fireball did not contact the surface.

 

[bcredman]

Worse, actually, because every nuke would be a surface blast, generating the maximum possible fallout.




Several really big lasers, though the most famous one (MIRACL) had absolutely terrible spot size.

I think the THAAD radar came out of SDI, though I'm not sure about THAAD proper.

IIRC the single best part of SDI was the SM3 KKV.

The THAAD missile defense concept was proposed in 1987, with a formal request for proposals submitted to industry in 1991. The THAAD program benefited from results of previous missile defense efforts like High Endoatmospheric Defense Interceptor (HEDI) and the Kinetic Kill Vehicle Integrated Technology Experiment (KITE), both of which were SDI projects. HEDI was a proposed endoatmospheric interceptor concept and KITE was a test vehicle designed to validate key technologies for HEDI within the SDI program. In September 1992, the US Army selected Lockheed, now Lockheed Martin, as the prime contractor for THAAD development.

The MIRACL laser was developed prior to SDI. The MIRACL laser first became operational in 1980. The SDI program began in 1983.

The high power chemical laser that was actually developed and tested under the SDI program was the Alpha laser, which had its origins in the 1970s in a DARPA project which was transitioned to the SDI program in 1983. The DARPA effort was known as Triad which had three programs: the Alpha Program to develop the laser source, the Large Optics Demonstration Experiment (LODE) to develop the beam control, and the Talon Gold Program to develop the precision pointing capability. All three programs were transitioned to SDI (LODE became the Large Advanced Mirror Program (LAMP) under SDI).

The Alpha laser demonstrated repeatable megawatt-class lasing in May of 1991, and multiple high-power lasing tests were conducted from 1992-1994. The system was transitioned from operational status to preservation status 1994-1996 when SDIO was replaced with BMDO. However, in September of 1996, the system was reactivated and a lasing test was performed in preparation for integrating the Alpha laser with the LAMP mirror. Alpha-LAMP integration experiments were performed from 1997 to 1998 partially overlapping with Alpha laser performance optimization from 1997 to 2000. Flow optimization and megahertz intensity and tilt sensor experiments were performed from 2000-2002. A total of 27 high-power tests were run with the Alpha laser. See https://www.deps.org/DEPSpages/JDE/JV1N4P5-Wacks.pdf for more details.

The SM-3* Kinetic Kill Vehicle (KKV) is the modern version of the Lightweight Exoatmospheric Projectile Kinetic Kill Vehicle (LEAP KKV) developed under SDI.

Built by Hughes Aircraft, an early version of the LEAP KKV was successfully tested at the hover facility at Edwards Air Force Base in June 1991. Launched by a booster, LEAP KKVs are designed to destroy an enemy missile in space by physical impact and not by detonation of a warhead. After separation from the booster, the infrared seeker and divert propulsion system help guide it to the enemy missile. Modern versions of the LEAP KKV, now built by Raytheon, are being deployed atop SM-3 missiles on selected U.S. Navy ships to provide defense against theatre ballistic missiles.

*SM-3 stands for "Standard Missile - 3," which is a surface-to-air missile used by the US Navy to intercept ballistic missiles, primarily as part of the Aegis Ballistic Missile Defense System.

 

[bcredman]

This depend mainly of fireball size. The Hiroshima detonation, for example, was on about 600 meters altitude - and there were no long-term fallout to speak about, because nuclear fireball did not contact the surface.

Since the fireball size is determined by the yield of the bomb, your statement "This depend mainly of fireball size" is equivalent to my previous statement "the exact height depending on the yield of the bomb."

The bomb used over Hiroshima was an atomic fission bomb not a modern thermonuclear fusion bomb. The yield of the Hiroshima A-bomb was only about 15 kilotons of TNT equivalent compared to hundreds to thousands of kilotons of TNT equivalent for modern strategic nuclear weapons, hence the difference in minimum altitude for an air burst to avoid significant fallout.

 

[Byeman]

-- Networked sensors that include space-based sensors, and ground- and sea-based radars to detect and track targets;

Sea-Based X-band radar (SBX-1) is the only specific SDIO/BMDO/MDA asset built. No new ground radars were built. Space based were just upgrades of existing systems (DSP-SBIRS)

 

[quellish]

Erm. If the bomb detonated above surface - so the fireball did not touch ground - there would be no or almost no fallout. Fallout is caused by nuclear fireball reaching the ground & dragging in massive ammounts of matter, which is then irrdadiated by intense neutron flow. If the nuclear fireball did not reach ground, then there is next to nothing to irradiate.

Wow! No fallout? Then what happens to all the radioactive material inside the bomb?

Fallout is primarily composed of fission products from the process of detonation and the material of the bomb itself.

The fissions products are a wide range of isotopes with short and long lives. These are very dangerous.
The bomb material is, well, the materials in the bomb! Both the radioactive materials like plutonium and things like the firing unit, etc.

When a bomb is detonated close to solid material, like the ground, the fission products and bomb materials are attached to larger particles. These larger particles can travel farther, etc. The foot print of the fallout is larger, but the actual amount of dangerous particles is not really any different. The effect of the detonation's radiation on that additional debris (i.e. from a ground burst) is tiny. It's the radioactive particles from the fission products and bomb material attaching to debris and traveling far and getting lodged into things that is problematic. With an airburst the fallout is still there, it travels differently than if it had large amounts of solid debris to attach to.

The idea that a bomb can have no fallout, or that detonating an airburst has little or no fallout is not correct at all.

 

[Firefinder]

The idea that a bomb can have no fallout, or that detonating an airburst has little or no fallout is not correct at all

Except that what real life have shown to be true.

Everyone done real life test with Airbursts and found that unless the bomb is made to do so or the fireball touch the ground, the amount of Fallout from it is basically a none factor.

Straight up that is what all the studies say.

 

[quellish]

Except that what real life have shown to be true.

Everyone done real life test with Airbursts and found that unless the bomb is made to do so or the fireball touch the ground, the amount of Fallout from it is basically a none factor.

Straight up that is what all the studies say.

Oh shit, ALL the studies?

"Physical and Radiochemical Properties Of Fallout Particles" USNRDL-TR-899

From the summary:

The physical and radiochemical properties of fallout particles from nuclear weapons do not fall Into narrowly defined ranges. Detonations at altitudes sufficient to prevent Incorporation of soil into the fireball tend to produce small, spherical, highly active particles with the activity distributed throughout. If soll and other on-site material le incorporated into the fireball, one observes Increased frequency of particles vith lover specific activity, Irreguler shape, larger size, evidence of partial melting and aggloneration, and actvity concentrated on the surface of the particle. The leaching action of various solvents on fallout particles dependa upon the nature of the particles themselves as well as that of the solvent.

Huh. Sounds like this study compared fallout from detonations at altitude vs. those close enough to the ground to capture soil and other debris. They found them to be different, but similar - and the air burst fallout exists!



"Radionuclide Fractionation In Air-Burst Debris" USNRDL-TR-933

From the summary:

Radiochemical data from fractionated samples from 15 airbursts provided a source of equivalent-fission values for 24 radionuclides. The airbursts ranged in yield by a factor of over 300. The equivalent-fission values were converted to ratios based on 2r95 and these ratios were correlated logarithmically. The correlation slopes were found to be rela tively insensitive to yield and their values permitted the placement of the radionuclides on a scale of volatility. There were found several groups of radionuclides which did not fractionate from each other. The nuclides Cs137 and Be140 had essentially the same slopes for air bursts as for high-yield surface bursts, but Mo99 and Np239 behaved more volatilely in the air bursts. Finally, the volatility Inferred from fractionation behavior correlated well with that based on thermodynamic calculations.

Huh! Another study that compared fallout from air burst detonations to those near the ground. And again, the fallout in the air bursts was more active and volatile. And the mythical air burst fallout again exists!

"Particle size distribution in clouds from nuclear airbursts"

The theory of self-preserving size distributions of Friedlander and Wang has been applied to particle formation after nuclear air bursts. The parameters at the start of coagulation are those derived from nucleation theory as applied by Stewart and by Edvarson. Brownian motion with and without slip correction has been considered. The results are compared with the log normal distribution having a logarithmic standard deviation of 2.0 such that both distributions have the same value of the geometric mean diameter. At constant mass 〈a〉 varies slowly with yield, namely, it varies as W−0.23. Contours of constant 〈a〉 as a function of mass and yield have been calculated. The results are compared with size distributions measured on cap and stem samples from eight air bursts of the 1962 Dominic series.

And again, they found fallout from an air burst. This one, however, is notable as it was from the DOMINIC series that used the RIPPLE design concept. This was an extremely "clean" and efficient design concept that was never used in an operational weapon. Operational weapons are largely fission-fusion-fission and much "dirtier" and produce more fallout than RIPPLE. Yet even with this airburst detonation of the cleanest weapon design ever tested...

They found fallout!



ZOMG. A-Mazed.

So here are just 3 easy to find studies that examined the radiochemical properties of fallout from airbursts. Airburst fallout exists, and it's not a "none factor". It's actually quite serious!

 

[bcredman]

Wow! No fallout? Then what happens to all the radioactive material inside the bomb?

Fallout is primarily composed of fission products from the process of detonation and the material of the bomb itself.

The fissions products are a wide range of isotopes with short and long lives. These are very dangerous.
The bomb material is, well, the materials in the bomb! Both the radioactive materials like plutonium and things like the firing unit, etc.

When a bomb is detonated close to solid material, like the ground, the fission products and bomb materials are attached to larger particles. These larger particles can travel farther, etc. The foot print of the fallout is larger, but the actual amount of dangerous particles is not really any different. The effect of the detonation's radiation on that additional debris (i.e. from a ground burst) is tiny. It's the radioactive particles from the fission products and bomb material attaching to debris and traveling far and getting lodged into things that is problematic. With an airburst the fallout is still there, it travels differently than if it had large amounts of solid debris to attach to.

The idea that a bomb can have no fallout, or that detonating an airburst has little or no fallout is not correct at all.

All nuclear explosions produce fission products, un-fissioned nuclear material, and weapon residues vaporized by the heat of the fireball. These materials are limited to the original mass of the device, but include radioisotopes with long lives. When the nuclear fireball does not reach the ground, this is the only fallout produced. Its amount can be estimated from the fission-fusion design and yield of the weapon.

A nuclear weapon detonated in the air, called an air burst, produces less fallout than a comparable explosion near the ground. A nuclear explosion in which the fireball touches the ground pulls soil and other materials into the cloud and neutron activates it before it falls back to the ground. An air burst produces a relatively small amount of the highly radioactive heavy metal components of the device itself.

After the detonation of a weapon at or above the fallout-free altitude (an air burst), fission products, un-fissioned nuclear material, and weapon residues vaporized by the heat of the fireball condense into a suspension of particles 10 nm to 20 μm in diameter. This size of particulate matter, lifted to the stratosphere, may take months or years to settle, and may do so anywhere in the world. Its radioactive characteristics increase the statistical cancer risk, with up to 2.4 million people having died by 2020 from the measurable elevated atmospheric radioactivity after the widespread nuclear weapons testing of the 1950s, peaking in 1963 (the Bomb pulse). Levels reached about 0.15 mSv per year worldwide, or about 7% of average background radiation dose from all sources, and has slowly decreased since, with natural background radiation levels being around 1 mSv.

Radioactive fallout has occurred around the world; for example, people have been exposed to iodine-131 from atmospheric nuclear testing. Fallout accumulates on vegetation, including fruits and vegetables. Starting from 1951 people may have gotten exposure, depending on whether they were outside, the weather, and whether they consumed contaminated milk, vegetables or fruit. Exposure can be on an intermediate time scale or long term. The intermediate time scale results from fallout that has been put into the troposphere and ejected by precipitation during the first month. Long-term fallout can sometimes occur from deposition of tiny particles carried in the stratosphere. By the time that stratospheric fallout has begun to reach the earth, the radioactivity is very much decreased. Also, after a year it is estimated that a sizable quantity of fission products move from the northern to the southern stratosphere. The intermediate time scale is between 1 and 30 days, with long term fallout occurring after that.

During detonations of devices at ground level (surface burst), below the fallout-free altitude, or in shallow water, heat vaporizes large amounts of earth or water, which is drawn up into the radioactive cloud. This material becomes radioactive when it combines with fission products or other radio-contaminants, or when it is neutron-activated.

A surface burst generates large amounts of particulate matter, composed of particles from less than 100 nm to several millimeters in diameter—in addition to very fine particles that contribute to worldwide fallout. The larger particles spill out of the stem and cascade down the outside of the fireball in a downdraft even as the cloud rises, so fallout begins to arrive near ground zero within an hour. More than half the total bomb debris lands on the ground within about 24 hours as local fallout. Chemical properties of the elements in the fallout control the rate at which they are deposited on the ground. Less volatile elements deposit first.

Severe local fallout contamination can extend far beyond the blast and thermal effects, particularly in the case of high yield surface detonations. The ground track of fallout from an explosion depends on the weather from the time of detonation onward. In stronger winds, fallout travels faster but takes the same time to descend, so although it covers a larger path, it is more spread out or diluted. Thus, the width of the fallout pattern for any given dose rate is reduced where the downwind distance is increased by higher winds. The total amount of activity deposited up to any given time is the same irrespective of the wind pattern, so overall casualty figures from fallout are generally independent of winds. But thunderstorms can bring down activity as rain allows fallout to drop more rapidly, particularly if the mushroom cloud is low enough to be below ("washout"), or mixed with ("rainout"), the thunderstorm.

 

[bcredman]

Sea-Based X-band radar (SBX-1) is the only specific SDIO/BMDO/MDA asset built. No new ground radars were built. Space based were just upgrades of existing systems (DSP-SBIRS)

The Ground Based Radar (GBR) SDI program developed technologies that were incorporated into new and upgraded existing ground based radar systems starting in the early 1990s. SDI research significantly advanced phased array radar technology, allowing for rapid scanning and accurate tracking of multiple targets, a critical feature of the new and upgraded radar systems. The need to differentiate real missile threats from clutter in the SDI program led to the development of sophisticated signal processing algorithms now used in the new and upgraded radar systems.

From https://apps.dtic.mil/sti/pdfs/ADA338719.pdf "Under Secretary of Defense for Acquisition Donald Yockey on January 28 [1992] issued a directive giving SDIO authority to proceed with the development of the Theater High Altitude Area Defense System (THAADS) and the Theater Missile Defense Ground-Based Radar (TMD-GBR). THAADS will be a missile capable of intercepting and destroying shorter-range ballistic missiles in the upper reaches of the atmosphere; TMD-GBR will track the incoming missiles and direct THAADS interceptors against their targets."

The AN/TPY-2 Surveillance Transportable Radar, also called the Forward Based X-Band Transportable (FBX-T), which was developed alongside the Terminal High Altitude Area Defense (THAAD) ballistic missile defense system is a long-range, very high-altitude active digital antenna array X band surveillance radar designed to add a tier to existing missile and air defense systems. It has a range of up to 3,000 km (1,600 nmi; 1,900 mi), depending on target/mode. Made by Raytheon, it is the primary radar for the THAAD missile system, but also cues the AN/MPQ-53 radar of the MIM-104 Patriot system. Patriot PAC-3 is a lower-altitude missile and air defense system than THAAD.

The Department of Defense awarded an initial contract to produce the AN/TPY-2—then known as the “Theater Missile Defense Ground Based Radar (GBR)”—in 1992. The Army began full-rate production of the AN/TPY-2 in August 2000, and in March 2004 received its first production radar. Two additional radars were completed in 2005 and late 2006. In 2016, the Missile Defense Agency awarded a contract to produce an upgraded AN/TPY-2 with gallium nitride (GaN) T/R modules. On September 25th 2024, RTX (Raytheon) announced that they had completed their first TPY-2 with a full complement of GaN devices.

Since the end of SDI, two of the former Ballistic Missile Early Warning System Radars, and one PAVE Phased Array Warning System (PAWS) have been modified to support the Missile Defense mission through the Upgraded Early Warning Radars (UEWR) program. The UEWR upgrades modernized 80 percent of the radar/computer subsystems and a complete re-write of software to improve midcourse BMDS sensor coverage by providing critical early warning, tracking, object classification, and cueing data.

 

[Dilandu]

Wow! No fallout? Then what happens to all the radioactive material inside the bomb?

You are talking about several hundreds kilo vs several thousands tons. The difference is MANY order of magnitude.

 

[quellish]

You are talking about several hundreds kilo vs several thousands tons. The difference is MANY order of magnitude.

Several thousand tons of what? Radioactive material?

If so please show me a reference that supports that assertion.

 

[Scott Kenny]

Several thousand tons of what? Radioactive material?

If so please show me a reference that supports that assertion.

Ever heard of neutron activation?

You know, where one material becomes a radioactive isotope due to catching at least one neutron from a nuclear reaction?

 

[Dilandu]

Several thousand tons of what? Radioactive material?

The material from surface is dragged from surface into the fireball - basically into the cloud of actively fissioning uranium plasma. It's subjected to very highly intence neutron radiation here. Atoms caught additional neutrons, and a lot of highly unstable isotopes are created. The updraft carry the irradiated material upward, creating a massive cloud of highly radioactive material.

 

[Byeman]

The Ground Based Radar (GBR) SDI program developed technologies that were incorporated into new and upgraded existing ground based radar systems starting in the early 1990s. SDI research significantly advanced phased array radar technology, allowing for rapid scanning and accurate tracking of multiple targets, a critical feature of the new and upgraded radar systems. The need to differentiate real missile threats from clutter in the SDI program led to the development of sophisticated signal processing algorithms now used in the new and upgraded radar systems.

From https://apps.dtic.mil/sti/pdfs/ADA338719.pdf "Under Secretary of Defense for Acquisition Donald Yockey on January 28 [1992] issued a directive giving SDIO authority to proceed with the development of the Theater High Altitude Area Defense System (THAADS) and the Theater Missile Defense Ground-Based Radar (TMD-GBR). THAADS will be a missile capable of intercepting and destroying shorter-range ballistic missiles in the upper reaches of the atmosphere; TMD-GBR will track the incoming missiles and direct THAADS interceptors against their targets."

The AN/TPY-2 Surveillance Transportable Radar, also called the Forward Based X-Band Transportable (FBX-T), which was developed alongside the Terminal High Altitude Area Defense (THAAD) ballistic missile defense system is a long-range, very high-altitude active digital antenna array X band surveillance radar designed to add a tier to existing missile and air defense systems. It has a range of up to 3,000 km (1,600 nmi; 1,900 mi), depending on target/mode. Made by Raytheon, it is the primary radar for the THAAD missile system, but also cues the AN/MPQ-53 radar of the MIM-104 Patriot system. Patriot PAC-3 is a lower-altitude missile and air defense system than THAAD.

The Department of Defense awarded an initial contract to produce the AN/TPY-2—then known as the “Theater Missile Defense Ground Based Radar (GBR)”—in 1992. The Army began full-rate production of the AN/TPY-2 in August 2000, and in March 2004 received its first production radar. Two additional radars were completed in 2005 and late 2006. In 2016, the Missile Defense Agency awarded a contract to produce an upgraded AN/TPY-2 with gallium nitride (GaN) T/R modules. On September 25th 2024, RTX (Raytheon) announced that they had completed their first TPY-2 with a full complement of GaN devices.

Since the end of SDI, two of the former Ballistic Missile Early Warning System Radars, and one PAVE Phased Array Warning System (PAWS) have been modified to support the Missile Defense mission through the Upgraded Early Warning Radars (UEWR) program. The UEWR upgrades modernized 80 percent of the radar/computer subsystems and a complete re-write of software to improve midcourse BMDS sensor coverage by providing critical early warning, tracking, object classification, and cueing data.

I was referring to CONUS defense. No new radars

 

[bcredman]

I was referring to CONUS defense. No new radars

You did not specify only for CONUS defense in your original response to my post, and I did not specify that limitation in my original post, nor was that limitation specified in the original question I was answering in my post, which was "what, if any, actual documented hardware ever came out of SDI?"

THAAD and the 12 AN/TPY-2 radars are certainly documented hardware the came out of SDI and the 12 AN/TPY-2 radars are certainly ground based radars.

In addition, according to https://www.armed-services.senate.gov/imo/media/doc/Hill Statement to SASC.pdf
Vice Admiral Jon A. Hill, USN, Director, Missile Defense Agency stated before the Senate Armed Services Committee Strategic Forces Subcommittee, on May 18, 2022:
"MDA is upgrading, sustaining, and supporting operation of 12 AN/TPY-2 radars, including five Forward Based Mode radars in Japan, Israel, Turkey, and U.S. Central Command. We have seven Terminal Mode radars in CONUS locations or forward deployed with U.S. Army Terminal High Altitude Area Defense (THAAD) batteries in U.S. Indo-Pacific Command."

 

[bcredman]

Several thousand tons of what? Radioactive material?

If so please show me a reference that supports that assertion.

From https://en.wikipedia.org/wiki/Mushroom_cloud :

"For a ground detonation, approximately 200 tons of soil per kiloton of yield is melted and comes in contact with radiation.[9]"

"A low-altitude detonation produces a cloud with a dust loading of 100 tons per megaton of yield. A ground detonation produces clouds with about three times as much dust."

Thus, for a ground detonation of a megaton of yield, about 1000kT * 200 tons/kT = 200,000 tons of soil is melted and comes in contact with radiation. Of this, about 300 tons of radioactive soil is lifted into the mushroom cloud.

From https://en.wikipedia.org/wiki/Nuclear_fallout :

"This radioactive dust, usually consisting of fission products mixed with bystanding atoms that are neutron-activated by exposure, is a form of radioactive contamination.[2]

Fallout comes in two varieties. The first is a small amount of carcinogenic material with a long half-life. The second, depending on the height of detonation, is a large quantity of radioactive dust and sand with a short half-life.

All nuclear explosions produce fission products, un-fissioned nuclear material, and weapon residues vaporized by the heat of the fireball. These materials are limited to the original mass of the device, but include radioisotopes with long lives.[3] When the nuclear fireball does not reach the ground, this is the only fallout produced. Its amount can be estimated from the fission-fusion design and yield of the weapon...

During detonations of devices at ground level (surface burst), below the fallout-free altitude, or in shallow water, heat vaporizes large amounts of earth or water, which is drawn up into the radioactive cloud. This material becomes radioactive when it combines with fission products or other radio-contaminants, or when it is neutron-activated...

There are two main considerations for the location of an explosion: height and surface composition. A nuclear weapon detonated in the air, called an air burst, produces less fallout than a comparable explosion near the ground. A nuclear explosion in which the fireball touches the ground pulls soil and other materials into the cloud and neutron activates it before it falls back to the ground. An air burst produces a relatively small amount of the highly radioactive heavy metal components of the device itself."


[2] "Radioactive Fallout | Effects of Nuclear Weapons | atomicarchive.com". www.atomicarchive.com. Archived from the original on 18 January 2018. Retrieved 31 December 2016.

[3] National Research Council (2005). Effects of Nuclear Earth-Penetrator and Other Weapons. National Academies Press. ISBN 9780309096737. Archived from the original on 15 May 2021. Retrieved 4 December 2018.

[9] Radioactive fallout after nuclear explosions and accidents, Volume 3, I. A. Izraėl, Elsevier, 2002 ISBN 0080438555

 

[quellish]

The material from surface is dragged from surface into the fireball - basically into the cloud of actively fissioning uranium plasma.

No, by the time any physical movement of "material from the surface" happens fission is long over. There is no cloud of "actively fissioning" material. There are fission products, but there is no fissioning going on.

It's subjected to very highly intence neutron radiation here. Atoms caught additional neutrons, and a lot of highly unstable isotopes are created.

No, again by this time the "high intense neutron radiation" is already over. Fission products have been created and are decaying at varying rates, and the majority of the neutrons capture has already happened within the bomb components themselves. The neutrons that have escaped the bomb components have already been captured by matter outside the bomb.

The updraft carry the irradiated material upward, creating a massive cloud of highly radioactive material.

The heat created by a detonation turns matter in close proximty to the "fireball" into gas or plasma. As the fireball expands and vaporizes matter it creates a vacuum which generates an updraft as matter rushes to fill the vacuum. Matter that is sucked into the vaccum is either vaporized or pulled into the updraft. All of this occurs AFTER that matter has experienced any neutron capture from the fission or fusion reactions. The radioactivity created by neutron capture of this matter is minor.

As the fireball cools and the fission products, bomb material (including unspent fuel), and collected matter condense into particles. These components combine in various forms. Fission products are the greatest source of radioactvity in the particles in both quantity and intensity. If these components do not have an opportunity to mix well during the cooling stages the particles generated will be smaller and less likely to reach the ground in the immediate area ("local fallout"). Instead they may travel the atmosphere for considerable periods of time and decrease in overall activity.

Fallout comes in two varieties. The first is a small amount of carcinogenic material with a long half-life. The second, depending on the height of detonation, is a large quantity of radioactive dust and sand with a short half-life.

No. The materials with short half lifes - which are more energetic and dangerouns - are fission products. The height of the detonation plays absolutely no part in production of these fission products. "Radioactive dust and sand" will only have a short half life if fission products attach to or condense with vaporized "dust and sand". "Dust and sand" will not result in material with a short energetic half life through neutron capture, which is what this seems to be implying.

An air burst produces a relatively small amount of the highly radioactive heavy metal components of the device itself.

According to this statement, if you had two identical bombs and detonated one as a ground burst and the other as an air burst they would produce two different masses of "radioactive heavy metal elements" from the bomb itself.

This does not pass the sniff test. The height of the detonation will have no effect on the mass of the internal bomb components. Both bombs will produce the same "highly radioactive heavy metal components of the device itself".

 

[bcredman]

No, by the time any physical movement of "material from the surface" happens fission is long over. There is no cloud of "actively fissioning" material. There are fission products, but there is no fissioning going on.



No, again by this time the "high intense neutron radiation" is already over. Fission products have been created and are decaying at varying rates, and the majority of the neutrons capture has already happened within the bomb components themselves. The neutrons that have escaped the bomb components have already been captured by matter outside the bomb.



The heat created by a detonation turns matter in close proximty to the "fireball" into gas or plasma. As the fireball expands and vaporizes matter it creates a vacuum which generates an updraft as matter rushes to fill the vacuum. Matter that is sucked into the vaccum is either vaporized or pulled into the updraft. All of this occurs AFTER that matter has experienced any neutron capture from the fission or fusion reactions. The radioactivity created by neutron capture of this matter is minor.

As the fireball cools and the fission products, bomb material (including unspent fuel), and collected matter condense into particles. These components combine in various forms. Fission products are the greatest source of radioactvity in the particles in both quantity and intensity. If these components do not have an opportunity to mix well during the cooling stages the particles generated will be smaller and less likely to reach the ground in the immediate area ("local fallout"). Instead they may travel the atmosphere for considerable periods of time and decrease in overall activity.



No. The materials with short half lifes - which are more energetic and dangerouns - are fission products. The height of the detonation plays absolutely no part in production of these fission products. "Radioactive dust and sand" will only have a short half life if fission products attach to or condense with vaporized "dust and sand". "Dust and sand" will not result in material with a short energetic half life through neutron capture, which is what this seems to be implying.




According to this statement, if you had two identical bombs and detonated one as a ground burst and the other as an air burst they would produce two different masses of "radioactive heavy metal elements" from the bomb itself.

This does not pass the sniff test. The height of the detonation will have no effect on the mass of the internal bomb components. Both bombs will produce the same "highly radioactive heavy metal components of the device itself".

You misconstrued my statement "An air burst produces a relatively small amount of the highly radioactive heavy metal components of the device itself" out of context, so let me make this clearer. For identical devices, both the air burst and the ground detonation contain the same amount of highly radioactive heavy metal components of the device itself, but the air burst contains only that component whereas the ground detonation contains both that component plus the soil and debris that was made radioactive by neutron activation during the initial detonation and then sucked into the mushroom cloud. The mass of the highly radioactive heavy metal components of the device itself is relatively small compared to the mass of the radioactive soil and debris entrained in the mushroom cloud.

The statement "Fallout comes in two varieties. The first is a small amount of carcinogenic material with a long half-life. The second, depending on the height of detonation, is a large quantity of radioactive dust and sand with a short half-life" is a direct quote from the Wikipedia article on nuclear fallout.

That article states:

"Fallout comes in two varieties. The first is a small amount of carcinogenic material with a long half-life. The second, depending on the height of detonation, is a large quantity of radioactive dust and sand with a short half-life.

All nuclear explosions produce fission products, un-fissioned nuclear material, and weapon residues vaporized by the heat of the fireball. These materials are limited to the original mass of the device, but include radioisotopes with long lives.[3] When the nuclear fireball does not reach the ground, this is the only fallout produced. Its amount can be estimated from the fission-fusion design and yield of the weapon..."

The reference [3] is National Research Council (2005). Effects of Nuclear Earth-Penetrator and Other Weapons. National Academies Press. ISBN 9780309096737. Archived from the original on 15 May 2021. Retrieved 4 December 2018.

If you think that statement is incorrect, argue it with the Wikipedia and the National Research Council, and then let me know the outcome.

But before you argue with the Wikipedia and the National Research Council, note that their statement does not say that the detonation of the device does not produce highly radioactive products with short half lives. As you say, detonation of the device does produce fission products that are highly radioactive with short half lives, but these products were vaporized into very small particles which stay aloft for much longer than their half-lives so they do not contribute to radioactive fallout if there are no large particles for them to condense on as in a high altitude air burst. Thus, for the high altitude air burst case, only the long half-life radioactive products remain radioactive long enough to contribute to the long term, widespread fallout, the effect of which is to raise the statistical rates of cancer in those exposed to it. In the ground burst case, the soil and debris particles provide condensation sites for the vaporized short half-life fission products, and the larger mass of those particles makes them fall to the ground while those short half-life fission products are still highly radioactive.

 

[quellish]

but the air burst contains only that component

Again, this is not true. Even an air burst contains components from outside the weapon. The atmosphere contains matter which is consumed and experiences neutron capture.

The mass of the highly radioactive heavy metal components of the device itself is relatively small compared to the mass of the radioactive soil and debris entrained in the mushroom cloud.

Again, this is not true, and does not take into account the half lifes or activity of the material.

If you think that statement is incorrect, argue it with the Wikipedia and the National Research Council, and then let me know the outcome.

And here is the problem. Neither Wikipedia nor the NRC posted this information to this forum. t

I have few issues with the NRC report that was cited. But the Wikipedia "article", that is a different story., The statements that were quoted in this forum from Wikipedia have little basis in fact and are not reflective of the supposed source material. The NRC report does not make the statements about half life, the "categories" of fallout, etc. that the Wikipedia article does. In fact, the Wikipedia article does not reflect that report at all and in is in several places contrary to the NRC report.

Wikipedia has low standards for articles, and this is great example. The "Nuclear Fallout" article has an edit history that includes:

→Long term: Editing wording. I'm pro-nuclear but this section was reeking with bias and mispresents the far more balanced arguments in the NYT and New Scientist sources (the only two I read)

Ah yes, wikipedia, written by those who can't be bothered to read the references yet still argue for "balance".

Wikipedia fails on technical and esoteric topics - which once may have been its strength - as many forum members know. I am sure a number of forum members can mention Wikipedia articles they know to be incorrect or complete fabrications, especially about topics that relfect the expertise on this forum.

As always, check and vet your references.

very small particles which stay aloft for much longer than their half-lives so they do not contribute to radioactive fallout if there are no large particles for them to condense on as in a high altitude air burst. Thus, for the high altitude air burst case, only the long half-life radioactive products remain radioactive long enough to contribute to the long term, widespread fallout

This is absolutely false, and reflects a theme within this thread.
While the Wikipedia article quoted verbatim previously in this thread makes assertions about fallout being of two absurd types, in reality there are many kinds - including "local fallout". Local fallout condenses and collects within proximity to the detonation site. "Soil, dust and sand" from a ground detonation produces more local fallout - though the actual quantity and activity of radioactive debris is little different from an air burst.
Other types of fallout, such as "global fallout", are more long lived and subject to more variables such as weather conditions. Fallout that might otherwise be "global" can get very local depending on weather conditions. The fallout products produced by an airburst become very local if conditions allow for rain - and the materials that condense can be very, very dangerous.