Monday, January 18, 2021

Joan Curran, Physicist and Inventor

By Nancy J. Farrier

Joan Strothers
Wikimedia Commons

Joan Strothers  Curran is a little known name, yet 
her inventions made a significant impact with during WWII, saving many lives. 


She was born in 1916 in Wales, attended a girls’ high school there and won a scholarship to Newnham College, Cambridge. Joan completed an honors degree program in physics at Cambridge, but was denied the actual degree, because at that time women were not allowed a degree from Cambridge.

Cambridge, Newnham College
Photo by Azeira, Wikimedia Commons

Joan had a gift for science and physics and after completing her first degree in 1938, she received a government grant to continue her doctorate in physics at Cambridge’s Cavendish Laboratory where she worked with another physicist, Sam Curran. Joan and Sam worked well together but as the war heated up, she and Sam were often transferred to other facilities to work on war specific designs. 


During this time, they developed proximity fuses, used to destroy enemy planes and rockets. This fuse would detonate a launched rocket before it could strike the intended target. Britain did not have the resources to mass-produce the fuse so they sent the design to the United States. The Americans were able to mass-produce the fuse, sending them back to Britain to help in the war. 


Joan and Sam married in November of 1940. They were transferred to the Telecommunications Research Establishment (TRE) where Sam worked on centimetric radar and Joan was assigned to a counter measures group. This is where Joan developed the radar cloaking technique called Window by the British and Düppel by the German Luftwaffe. Later the radar cloaking device became known as Chaff.


Joan believed strips of metal would deflect the radar and confuse the enemy about the location of the plane or planes. She worked with many different sizes of metal, including one that was a thin metal sheet also used to print a message for the people after the metal fell to the ground. In the end, she decided to use thin tin foil strips, less than and inch wide and almost ten inches long. Bundles of these strips would be thrown from the lead plane in a raid and form a cloud of confusion for the radar devices of the enemy.

Lancaster dropping chaff over Essen during
a thousand bomber raid. 
Wikimedia Commons


Chaff was first tested during Operation Gomorrah, a raid on Hamburg. The loss of planes and lives was much lower and credited to the use of Joan’s device. The Allies went on to use Window or chaff to confuse the enemy during large bomber raids. The Allies used chaff combined with dummy parachutists in Northern France to deflect the enemy from the invasion in Normandy. Joan is credited with helping to bring about victory for the Allies and lessening the loss of planes and lives.

Chaff on Radar
Wikimedia Commons

In 1944, the Curran’s went to the USA to work on the Manhattan Project, which developed the Atomic Bomb. They were sent to Berkeley, California to join the Berkeley Radiation Laboratory. They helped to develop an electromagnetic isotope separation process to make enriched uranium for the atomic bomb.


In Berkeley, Joan gave birth to their first child, a daughter. Their daughter had a severe mental disability, which made Joan sensitive to the issues of the handicapped. Joan and Sam had three sons, all of whom grew up and completed their own PhD’s. 


After the war ended, Joan and Sam went to Glasgow, Scotland, where Sam became the Professor of Natural Philosophy at Glasgow University. Joan was very active in the Scottish Society for the Parents of Mentally Handicapped Children, which the Curran’s and some of their friends started. Joan worked toward the needs of the handicapped and the disabled. 


In 1987, Joan received her first degree from the University of Strathclyde, as a Doctor of Laws honoris causa. This is an honorary degree that includes the sciences. Sam died in February 1998 and Joan died of cancer one year later. 


I enjoyed researching and learning about this amazing woman who did so much to further science and save lives. Have you ever heard of Joan Curran or her inventions? A colleague of Joan's said, “In my opinion, Joan Curran made an even greater contribution to victory, in 1945, than Sam.”  What an amazing legacy.

Nancy J Farrier is an award-winning author who lives in Southern Arizona in the Sonoran Desert. She loves the Southwest with its interesting historical past. When Nancy isn’t writing, she loves to read, do needlecraft, play with her cats, and spend time with her family. You can read more about Nancy and her books on her website:


  1. Very interesting! Even with all my research into WWII, I've not heard of Joan. Thanks for sharing.

  2. Wow! Thanks for this informative post! This was a power couple if there ever was one!

    1. Thank you, Connie. I loved learning about them too.

  3. wow this is some cool history. thanks for sharing what you found. i love to read about how women made a huge difference.

    1. Thank you, Lori. I'm so glad you enjoyed the post about Joan.

    2. Suzanne Kelman writes an interesting historical novel, "When the Nightingale Sings" based on the friendship between Joan Curran and Hedy Lamarr who was also a lover of the sciences and an inventor.