Boeing WC-135 Constant Phoenix

Boeing WC-135 Constant Phoenix

US Air Force demands three new NUCLEAR SNIFFER planes over North Korea H-bomb threat
The US Air Force has requested £148million ($208 million) to convert three KC-135R aerial refueling tankers into specialised nuclear trackers dubbed Constant Phoenix.
The two “aging” WC-135 planes currently in active service are becoming unfit for purpose, the force said.
Introduced in the 1960s, Boeing WC-135 Constant Phoenix planes are designed to detect nuclear explosions by collecting samples from the atmosphere.
In the wake of North Korea’s hydrogen bomb test last year, Constant Phoenix aircraft have become a valuable asset to the US Air Force.
Hence, the US Air Force has asked for funds to fit three KC-135Rs with the same “mission sensor system” as the WC-135Ws, The Drive has reported.
“These conversions are needed to address airframe viability concerns associated with the aging WC-135W fleet,” a budget proposal, published on February 12, said.
“Analysis determined that it was more cost effective to convert KC-135R aircraft into WC-135Rs than to modify existing WC-135W aircraft to be on par with the rest of the C-135 variants (i.e. RC-135 and KC-135).”
The main purpose of Constant Phoenix jets is to ensure the 1963 Partial Nuclear Test Ban Treaty is unheld. But in the budget proposal, the US Air Force cites the “rapidly changing global threat environment” as the main reason for needing more advanced WC-135Rs.
Contractor: Boeing Aerospace Co.
Service: United States Air Force
Power Plant: WC-135C, Four Pratt & Whitney TF33-P9 turbofans without thrust reversers;
WC-135W, Four Pratt & Whitney TF33-P-5 turbofans with thrust reversers
Speed: 403 mph
Range: 4,000 nautical miles
Crew: Varies with mission
The WC-135 Constant Phoenix is a militarized version of the Boeing 707 commercial airliner which is used to verify compliance of the 1963 Limited Nuclear Test Ban Treaty. The WC-135W Constant Phoenix atmospheric collection aircraft supports national level consumers by collecting particulate and gaseous effluents and debris from accessible regions of the atmosphere.
The aircraft is a modified C-135B or EC-135C platform. The Constant Phoenix’s modifications are primarily related to its on-board atmospheric collection suite, which allows the mission crew to detect radioactive “clouds” in real time. The aircraft is equipped with external flow-through devices to collect particulates on filter paper and a compressor system for whole air samples collected in holding spheres.
The cockpit crew is from the 45th Reconnaissance Squadron at Offutt Air Force Base, Neb., and special equipment operators are assigned to Det. 1, Air Force Technical Applications Center at Offutt AFB.
General Dwight D. Eisenhower commissioned the Constant Phoenix program on Sept. 16, 1947, when he charged the Army Air Forces with the overall responsibility for detecting atomic explosions anywhere in the world. In September 1949, a WB-29 flying between Alaska and Japan detected nuclear debris from Russia’s first atomic test–an event thought not possible until mid-1950.
Beginning in August 1950, WB-50 aircraft were converted for the air-sampling mission over a two-year period. WC-135 aircraft began replacing the WB-50s in December 1965 and became the workhorse of the atmospheric collection program.
Air sampling missions were routinely conducted over the Far East, Indian Ocean, Bay of Bengal, Mediterranean Sea, the Polar regions, and off the coasts of South America and Africa. The WC-135W played a major role in tracking radioactive debris from the Soviet Union’s Chernobyl nuclear plant disaster.
Currently the air-sampling mission supports the Limited Nuclear Test Ban Treaty of 1963, which prohibits any nation from above ground nuclear weapons testing. WC-135s are currently the only aircraft in the inventory conducting air-sampling operations.
Nuclear weapons either produce energy through nuclear fission (fission bombs) or a combination of fission and fusion (thermonuclear or hydrogen bombs). In both cases, nuclear reactions with neutrons cause the uranium or plutonium fuel to fission into two smaller nuclei, called fission fragments. These fragments are radioactive, and can be detected by their characteristic decay radiation.
If we detect these fission fragments, we know that a nuclear explosion occurred. And that’s where “sniffer” planes come in.
Enter ‘sniffer’ planes
Since 1947, the United States Air Force has operated a nuclear explosions detection unit. The current fleet uses the WC-135 Constant Phoenix. The aircraft fly through clouds of radioactive debris to collect air samples and catch dust. By measuring their decay, fission fragments can be detected in minute quantities.
The crew are kept safe using filters to scrub cabin air. Radiation levels are monitored using personal measuring devices for each crew member. A WC-135 Constant Phoenix from the 45th Reconnaissance Squadron taxis in on the flightline. 
Sniffer planes like Constant Phoenix can be rapidly deployed soon after a reported nuclear test and have been used to verify nuclear testsin North Korea in the past.
This year, Constant Phoenix has reportedly been deployed in Okinawa, Japan and has had encounters with Chinese jets. On the ground, the Comprehensive Test Ban Treaty Organisation (CTBTO) operates 80 ground-based monitoring stations across the globe that constantly monitor the air for fission products that have dispersed through the atmosphere.
Japan and South Korea operate their own radiation monitoring networks. These networks will also presumably be looking for signatures of the latest North Korean test.
What can fission fragments tell us?
When a nuclear test occurs underground, the fission fragments are trapped except for noble gasses. Because noble gasses don’t react chemically (except in extreme cases), they diffuse through the rock and eventually escape, ready to be detected.
In particular, some radioactive isotopes of the chemical element xenon are useful due to the fact these isotopes of xenon don’t appear in the atmosphere naturally, have decay times that are neither too long nor too short, and are produced in large quantities in a nuclear explosion. If you see these isotopes, you know a nuclear test occurred.
Something happened during this test that has people excited — there was an additional magnitude 4.1 tremor around eight minutes after the initial tremor, according to the United States Geological Survey. Among other things, this may indicate that the tunnel containing the bomb collapsed. If this happened, then other fission products and other radioactive isotopes could escape as dust particles.
This might have been accidental or deliberate (to provide proof to international viewers), but in either case, we may learn a lot, depending on how fast the sniffer planes arrived and how much dust was released.
For example, by looking at the probability of seeing fission fragments with different masses, the composition of the fission fuel could be determined. We could also learn about the composition of the rest of the bomb. These facts are things that nuclear states keep very secret.
Crucially, by looking for isotopes that could only be produced in a high intensity high energy neutron flux, we could suggest whether or not the bomb was indeed a hydrogen bomb.
What can’t they tell us?
The amount of information a sniffer plane can determine depends on how much material was released from the test site, how quickly it was released (due to nuclear decay) and how rapidly the sniffer plane got into place.
But fission fragment measurements probably can’t tell us whether the bomb tested was small enough to fit on an Intercontinental Ballistic Missile (ICBM). After all, it’s easy enough for North Korea to show a casing in a staged photograph and blow up something else.
Whether or not North Korea has a thermonuclear device that is capable of being mounted to an ICBM is a question weighing heavily on the minds of the international community.
Sniffer planes and the CTBTO network will be wringing all of the data they can out of the debris in the atmosphere to help the world understand the nuclear threat from North Korea.

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