The SR-71 Blackbird's Predecessor Created "Plasma Stealth" By Burning Cesium-Laced Fuel
Lockheed's A-12 Oxcart spy plane, which the company developed for the Central Intelligence Agency, was a direct response to the growing vulnerability of its earlier U-2 Dragon Lady to hostile air defense networks. As such, the plane – the predecessor to the U.S. Air Force's iconic SR-71 Blackbird – was extremely high- and fast-flying, but also incorporated then-state-of-the-art features to reduce its radar cross-section. These included a combination of a stealthy overall shape and radar-evading structures, as well as the use of composites in its construction, and the incorporation of radar absorbing materials on its skin. A far less known, but still a key component of the Skunk Works plan to make the A-12 harder to spot on radar involved a cesium-laced fuel additive to dramatically reduce the radar signature of the plane's massive engine exhausts and afterburner plumes by creating an ionizing cloud behind the aircraft to help conceal its entire rear aspect from radar waves.
A J58 during a ground test
Another J58 engine running
The basic principle behind this is a concept known as “
plasma stealth.” In the simplest terms, this involves creating a cloud of plasma, or ionized gas, around some or all of an object. The plasma then absorbs electromagnetic radiation, such as radar waves, preventing them from reflecting back. There are multiple ways to generate the required plasma Lovick’s idea was to inject an alkali metal, via a fuel additive, into the extremely hot exhaust streams, where the heat would turn it into an ionized gas.
The final additive mix was 30 percent cesium metal and 60 percent dialkyl phosphate, according to Lovick. However, he says in his book that the testing of the additives, which included flight tests at Area 51, was finished by 1965, but it’s unclear if this only refers to Lockheed’s portion of the work before the project passed to Pratt & Whitney.
However, none of the post-mission reports clearly state that the A-12s on either of these missions, or any others, used
A-50. Available records also make clear that standard JP-7 did not have the cesium mixture and that
personnel would only have added it when authorized to do so for a specific mission. It’s not entirely clear why, with the reported effectiveness of the mixture, the CIA would have declined to actually employ operationally in the end.
Given that the A-12’s speed and its electronic warfare package seemed sufficient to protect it over North Vietnam, the CIA may have continued to withhold use of A-50 for operational security reasons. Using it could have exposed its existence and given the Soviets and their allies time to develop countermeasures, rendering it less effective when it might have been absolutely necessary.
Whatever the case, A-50 appears to have at least remained available for use throughout Operation Black Shield. What happened to any remaining stockpiles of the additive after the A-12 program came to a close in 1968 is unclear.
https://www.thedrive.com/the-war-zo...d-plasma-stealth-by-burning-cesium-laced-fuel
